Applied Mechanics Research and Researchers

We are migrating to iMechanica.Org

2006-09-09T09:24:00.000-07:00

The drama of a mathematical proof

2006-08-26T15:03:00.000-07:00

An article in this week’s New Yorker describes the human drama behind a proof of the Poincare conjecture, one of the seven Millennium Problems. The article is unsparing of several mathematicians of Chinese origin.

Notes added on 27 August.

Perelman turns down Fields Medal.
Here is an excellent article on the proof in the New York Times.
See the comment posted by Ting Zhu.

Meshfree Methods blog

2006-08-03T15:53:00.000-07:00

A blog dedicated to Meshfree Methods has recently been set up by the USACM Specialty Committee on Meshfree Methods. This was inspired in no small part by the work of Professor Zhigang Suo and colleagues on the Applied Mechanics blogs.

Mechanics of Solids and Materials

2006-07-17T10:23:00.000-07:00

This graduate level textbook by Robert J. Asaro and Vlado A. Lubarda has recently been published. The website of Cambridge University Press gives some description of the book.

Online Journal Club on Flexible Electronics

2006-07-13T08:06:00.000-07:00

In the sidebar of this blog, I've added a link to the Macroelectronics Journal Club, which was started by Teng Li using CiteULike. You may want to read Teng Li's introduction to the Journal Club. You may want to join his club, or create your own club.

e-reader is out

2006-07-10T18:56:00.000-07:00

For those who do research on macroelectronics, the e-reader has been a long awaited product. Will it really be as good as a printed book?

Note added on 11 July 2006. See also 5 new design concepts of flexible displays.

Shaky Equilibrium - Phys Rev Focus

2006-07-08T13:48:00.000-07:00

The 'crystallization' of shaken sand-like grains matches the process in computer simulations of idealized molecules, implying that the physics of gases and fluids may apply to granular materials.

1990 Timoshenko Medal Lecture by Stephen H. Crandall

2006-07-08T05:59:00.000-07:00

The Joy of Applying Mechanics

Stephen H. Crandall, Massachusetts Institute of Technology

Text of Timoshenko Medal acceptance speech delivered at the Applied Mechanics Dinner of the 1990 Winter Annual Meeting of ASME in Dallas, Texas.

Good evening. Thank you Tom and Art for your kind introductions.

Thirty-five years ago I joined the Applied Mechanics Division of ASME. Two years later I was in the audience when the first Timoshenko medal was awarded to Stepan Prokovievich Timoshenko. I wonder how many others here tonight were also in that audience (a show of hands indicated that there were a total of twelve including the speaker). After that first medal, the Division went into high gear. In the next three years, six of the remaining giants of applied mechanics were given Timoshenko medals: Th. von Karman, G. I. Taylor, Arpad Nadai, Sir Richard Southwell, C. B. Biezeno, and Richard Grammel. Then in 1961, the Division settled down to our present steady-state operation of one medal a year. I haven't missed many AMD dinners through the years so I have had the good fortune to see most of the previous 36 awardees receive their medals. Taken together, they form an impressive cavalcade of applied mechanics. I consider it a very great honor to join this team.

I feel proud and humble at the same time. Five years ago when the late Eli Sternberg was accepting the Timoshenko medal he said, in jest, that medals, much like arthritis, were a common symptom of advancing years. I am sure that underneath that jest, deep down in his heart of hearts, Eli was just as proud as I am to receive this award.

In my case I owe a great deal to my mentor the late Jaapie Den Hartog and indirectly to his mentor before that. When I joined the ME department at MIT in 1946 Den Hartog was my first boss. Many of you already know that Den Hartog's first boss, 22 years earlier at Westinghouse, was none other than our Stepan Prokovievich. From this point of view I think you can say that I'm the first third generation Timoshenko medalist.

Many of my predecessors have taken this opportunity to reflect on the state of applied mechanics. Some have been optimistic, others pessimistic. I find myself strongly optimistic. In my time I've seen great changes in mechanics education and great changes in mechanics research. Fifty years ago in the required curriculum for mechanical engineers at MIT there were nine semesters of applied mechanics. Today there are about 2 1/2 semesters in the required curriculum which are devoted to applied mechanics. You could call that the bad news. The good news is that in these same 50 years there has been an enormous growth in the amount of applied mechanics research. The growth rate in the number of mechanics journals over the past 50 years has been substantially greater than the inflation rate in the cost of living. The growth has been in many directions. Some developments have been driven by military and industrial applications. Some developments have been driven by the desire for greater rigor. One direction of development which has flourished during my time has been the treatment of multi-discipline and multi-media problems. Forty years ago I stumbled over the idea that most engineering analysis problems fall into one of three major categories: equilibrium problems, eigenvalue problems, or propagation problems. However, when I wrote Engineering Analysis, all the examples I used were limited to single discipline problems: an elastic structure, or a compressible flow, or a thermal conduction field. The book had hardly been published when I noticed that some of my colleagues were writing about topics like thermoelasticity or electromechanics or magneto-hydrodynamics. I found myself doing research on fluid-structure interactions, on soil-structure interactions, and on random vibration which is the marriage of vibration theory with probability theory.

For the most part, the developments in mechanics are in the applications. The basic theory is pretty much in place. I often tell my dynamics students that the last major break¬through in dynamics was made by a 24-year-old Cambridge University graduate student 325 years ago. His name was Isaac Newton. This is, of course, an exaggeration. Even in classical dynamics there is some growth. We have had a significant advance during the last decade with the development of the theory of chaotic responses to deterministic excitations. I think we can look forward to changes in how mechanics education is organized and to changes in application areas for mechanics research, but I am optimistic that there will continue to be interesting and exciting things to do in mechanics.

My wife Pat has a favorite cookbook called "The Joy of Cooking". What I'd like to do now is to recount to you my views on "The Joy of Applying Mechanics". I have had the good fortune to live through a period when an academic career devoted to applied mechanics could indeed be a joy. The primary reasons for this are the teaching, the research, and the people.

First of all, mechanics is fun to teach. It has its own logical consistency. Almost everything fits, and once you get into it the density of illuminating insights is very great. I sometimes feel sorry for my colleagues in materials and design. Compared to mechanics, those subjects are very difficult to teach well.

Secondly, mechanics is fun to do research in. The thrill of turning up a new insight is an exquisite joy, whatever the discipline, but the richness of insights, at all levels, in mechanics, makes it an especially inviting field. The spectrum of opportunities ranges from abstract analysis, to computational mechanics, to experimental mechanics. One of the spectacular areas of growth that I have witnessed is that of laboratory instrumentation for research in mechanics. For many investigations the latest high-tech instrumentation is indispensable, but mechanics is perhaps unique in providing opportunities for serious work with elementary tools. For example, the most effective technique I found for displaying the salient features of a wide-band random vibration field did not involve laser holography but consisted simply of resurrecting Chladni's 150-year-old technique of sprinkling salt on the vibrating plate.

Finally, mechanics is fun because of the people. The most important people are the students and the national and international brotherhood of fellow researchers in mechanics. Students provide a wonderful stimulus to their teachers. I agree with the statement that the way to stay young is to stop looking in the mirror and to concentrate instead on the faces of the students. A great joy as one grows older is the network of colleagues sharing similar research interests that one meets at national and international meetings. The opportunities for this were greatly expanded for my generation by the invention of the jet plane.

Pat and I enjoy travelling. Our marriage began with a sabbatical year in post-war London and we have subsequently enjoyed sabbaticals in France, Mexico, Israel, and California. We have gone on lecture tours in Australia, the Soviet Union, and China. Over the years we have built up an extended family of applied mechanics friends all around the world. As a spin-off from international travelling I took up the hobby of studying foreign languages. I have enjoyed learning basic conversational skills in several languages but so far I have only reached my goal of being able to give a lecture in the language in French, Spanish, and Russian. At a birthday celebration, not too long ago, I was being "roasted" about this hobby and I would like to share with you one of the jokes they told.

A tiny mouse was running for its life with a big black cat in pursuit. Just in time it popped into its hole and went squeaking with fright to its mother. "Oh mother! There's a terrible big cat outside. It almost killed me." The mother mouse calmed her child down saying, "There, there. You're safe in here." Then she said, "Now I'll teach you a lesson." Where upon mother mouse climbed boldly out of the hole and marched right up to the cat. Looking the cat in the eye she said, "Bow Wow! Arf, Arf!" The cat was so surprised, it turned tail and ran. Mother mouse then turned to her child and said, "Now you see the advantage of having a second language!"

Well, I hope you can see that I've thoroughly enjoyed a career of applying mechanics. To have it all topped off with the Timoshenko Medal is indeed a great delight. My cup runneth over! I shall always be grateful to the Applied Mechanics Division for this heartwarming recognition from my colleagues and friends. Thank you all.

1991 Timoshenko Medal Lecture by Yuan-Cheng Fung

2006-07-01T05:49:00.000-07:00

Mechanics of Man

by Yuan-Cheng Fung, University of California, San Diego

The text of the Timoshenko Medal Acceptance Speech delivered at the Applied Mechanics Dinner of the 1991 Winter Annual Meeting of ASME in Atlanta, Georgia.

First of all, let me thank those of you who worked hard to give me this honor. I know how much effort was involved. I want to thank Dr. Saric, Dr. Bogy, and all the Committee members who indulged in me. And thank you all here this evening. To Chia Shun's remarks I am speechless. I love him as a brother. I am proud to be praised by a sibling. He is the Timoshenko Professor at the University of Michigan. With this medal I can catch up with him to honor our hero.

I am very glad to be given this Award, because Timoshenko is my hero. His books on Elasticity, Elastic Stability, and Plates and Shells are the ones I cut my teeth on. Another hero of mine is Theodor von Karman. A third one is Poiseuille, who brought fluid mechanics to medicine. They are my idols, and I am very fortunate to have been given a von Karman medal by ASCE in 1976, a Poiseuille medal by the International Society of Biorheology in 1986, and a Timoshenko medal today. I would like to speak about them. I think they have a common feature in that they developed a mechanics of man, as distinguished from a mechanics of the heaven and earth.

In character, these three men were different. Timoshenko had a father image and is more immitigable. In the first lecture I heard from Timoshenko in 1949, he talked about how brilliant St. Venant was in science and engineering. He questioned why St. Venant was so obscure in French history. He searched for the reasons long and detailed. I felt it was like listening to a tale about a lost uncle on Christmas Eve.

Another good description of Timoshenko I heard from Den Hartog in his Timoshenko Award acceptance speech. Den Hartog said that he was working under Timoshenko at Westinghouse Research Lab when he finished a paper on torsion and hesitated to publish it because he did not know whether it was important enough. Timoshenko told him, "Who do you think you are! One contributes what one can!" One contributes what one can! I like that attitude.

In a von Karman lecture I heard, he opened with a remark about himself. He said that in his youth he missed inventing the radio, in his prime age he missed inventing the airplane, in his senior years he missed inventing the nuclear reactor. In his old age he would miss the exploration of space. So he can only talk about waves, aerodynamics, and aerothermo-dynamics. As a graduate student I did not know what to make of that comment, but I remembered it. It does make sense to me now against his total contributions and ambitions. The story of his inventing the vortex street was this: He was in Gottingen and talked to Herr Hiemenz who had spent years measuring the flow behind a circular cylinder. Hiemenz could not get the flow to be stabilized. The data he obtained was always oscillating. So Karman went to work on it and wrote out the whole theory in one weekend. When he presented it at a meeting in Paris, Henri Benard said that he had photographed the vortices earlier and there were some differences between Karman's theory and the experimental results. Karman made some quick calculations on the back of an envelope, stood up to explain the differences, and suggested that the street should be called "Boulevard de Benard in Paris." Such stories make Karman inimitable.

Poiseuille was born in 1797. He attended Ecole Polytechnique and got his Doctor of Science degree at age 31 with a thesis on the measurement of blood pressure with a small bore mercury manometer. He obtained the first accurate values of blood pressure since Stephen Hales showed the way 119 years earlier (1709). Then, in 1840, at an age of 43, he published his famous paper on water flow in circular cylindrical tubes. He used pipettes of diameter 15 microns to avoid turbulence, a diameter similar to capillary blood vessels. After that he published only one other paper, on the measurement of flow with ether and mercury at the suggestion of the reviewers of his famous paper. His biographers did not know what positions he held in his life until he was 63 years old, when he became an inspector of primary schools in Paris. He died on Dec. 26, 1869 at an age of 72. He exemplifies the case that one paper makes a man.

These three men are not shy in applying mechanics to new areas. They showed that science is developed by man, and man is helped by developments in science. In hard times like this year of budget cuts, it is worth remembering this principle, because society always has a need to improve the lot of people, and engineers are the ones to deliver such improvements. And the society will always provide the needed resources.

I believe in this principle, and did not find too much conflict between personal interest and the necessity for survival. Let me tell you a little bit about myself.

I was born in China in 1919. I grew up in a period when China was very unsure of itself. My memory of my childhood was that the Christmas seasons were the time to seek refuge in the countryside, to get out of the way of the war paths of local war lords fighting for territory. I remember my family crowded in a little boat eating cold chicken. That's probably why I have liked cold chicken all my life. Later, China's problem of survival became even more difficult. In my first junior high school year, Japan took Manchuria (the September 18th event). The next year Japan invaded Shanghai (the January 28th event) and we fled to Peking. At year's end, Japan invaded She-Feng Kou and we fled back to Changchow. Students struck often to protest the government's nonresistance policy. I entered college in 1937 when the Japanese militarists started the last big push to conquer China. I chose to study aeronautics because airplanes were needed most in China's fight for survival.

In 1943, a consortium of American universities offered 20 graduate assistantships to China. The Chinese government held a national examination, selected the candidates, trained them for language, then sent them on their way. I got the position from Caltech. When I arrived in Pasadena and reported to Ernie Sechler on Jan. 6, 1946, Ernie laughed heartily by saying that the assistantship offer had expired by over two years! But he hired me as an RA. I inherited a little wind tunnel built by von Karman and Louis Dunn to study the flutter of the Tacoma Narrows suspension bridge, and was also given the job to study a drawer full of notes and scratch papers written by Tony Biot on theoretical analysis of flutter of that bridge, and to write a report about it. That was how I got into aeroelasticity. Unfortunately, von Karman had retired, Biot had gone to New York, and Dunn had gone to the Jet Propulsion Laboratory. I was left without a supervisor on aeroelasticity. Professor of mathematics Aristotle Michal took me under his wing. He taught me Frechet derivatives, with which I began my thesis on airplane dynamics.

I got my Ph.D. in Aeronautics in 1948, and stayed on the faculty. Ernie Sechler was my mentor. I have an enormous love and respect for him. Whatever I did he could show me a way to make it simpler. He was a wise counselor, and a warm friend. We worked together for 20 years on swept wing design, shell buckling, ICBM base hardening, rocket structure, fuel sloshing, etc.
In 1957, I began my self-study of physiology. I had a sabbatical leave in Gottingen, Germany. I stayed at Prandtl and von Karman's old Institution. I found its work on aeroelasticity rather dull, but the library on physiology next door was excellent. The causal factor for my going to the library was my mother's glaucoma. I translated newly published articles on glaucoma into Chinese and sent them to her in China to give to her surgeon. On returning to Caltech I began working on physiology with Sid Sobin, Wally Frasher, and Ben Zweifach. Together we wrote papers on the capillary blood vessels, red blood cells, the interaction of cells and vessels, and the mechanical properties of living soft tissues. I found continuum mechanics indispensible in clarifying these topics. In 1966, I resigned from Caltech and went to UCSD to devote full time to physiology and bioengineering.

I wanted to demonstrate that physiological problems can be solved with engineering methods. Together with Sid Sobin, I chose to work on the blood circulation in the lung. It was surprising that a thorough search of literature yielded very little reliable basic data on the pulmonary vasculature. The basic information we needed on the anatomy of the lung and biorheological properties of the materials did not exist. We had to obtain them by ourselves. Hence we had to turn ourselves into anatomists and histologists before we could use mathematical tools for physiology. The program was straightforward, but the road was long. For pulmonary circulation, it took us 12 years before we could close the first round. But we had fun on the way, and found many pretty pebbles right and left. The data we collected can be used to solve other problems. The theory worked out can be used clinically. Our patience was pretty good because a master plan existed and we knew the value of every link in the chain. But the importance of longevity became evident.

On approaching retirement, I entered another field: that of the relationship between tissue growth and physical stress. The question began at home. My wife, Luna, has a little high blood pressure which can be controlled with diazyde. But she does not like to take medicine. So she takes diazyde until her blood pressure lowers, then she stops to wait until the blood pressure rises again before taking another pill. This is not what the doctor ordered, and I wanted to know if it was a good idea. So I made a research project out of it. The project turned out to be full of surprises. For example, I found that our blood vessels remodel themselves rather quickly when the blood pressure changes. If the blood pressure was raised as a step function of time, structural change in the blood vessel wall will be detectable in one or two hours. Generally, the inner wall of the blood vessel will thicken first, doubling its thickness in two or three days. Then the outer wall thickens, and can be doubled in about 10 days. Furthermore, the residual stress in the vessel wall changes. Residual stress can be revealed by cutting a vessel segment into a ring, then cutting the ring open radially. The ring opens into a sector. The opening angles of normal arteries vary from place to place in the range of 0 to 90°, but in the aortic arch region it could be about 180°. In the pulmonary trunk it can be 360° or larger, i.e., it has so much residual stress that if it were given a chance to reach zero-stress, the vessel will turn itself inside out! Isn't that amazing! With a stepwise increase of blood pressure, the opening angle will increase first, reach a peak in 2 days, then decrease to an asymptotic value. The up and down swing of opening angle can be as large as 90-100° in some places. Our blood vessels are that alive! Associated with the structural changes, the mechanical properties change also. The constitutive equation changes with time. They are not constitutional laws at all.

These results are published in refereed medical journals such as Circulation Research, Journal of Applied Physiology, American Journal of Physiology, Journal of Biomechanical Engineering, etc., so I am not just telling you stories. You understand the mechanics instantly. I wish the medical people were as easily convinced as you are.

Fortunately, when the blood pressure is returned to normal, the changes are reversible to a large extent. Hence it appears that my wife is right. So she said, "All right. Then why don't you stop here? Why do you still talk about generalization, and more experiments? Why do you have to have a stress-growth law as you call it, sort of a constitutive equation squared?"

I offered Poiseuille as my excuse. I said, "Poiseuille knew that his paper No. 5 is his best. I still think that my next paper will be a better one. I am still experiencing my normal experience. My normal experience is something like this: A problem arises. It looks difficult. It is impossible to crack. I work on it day after day. I draw a blank. Then suddenly it becomes clear. It becomes simpler. Soon it is so simple that it is indeed trivial. I wonder why I did not see it before. So I throw the scratch paper into the waste paper basket. But the experience is pleasant. I call it life's little pleasure. I am still getting these little pleasures. But although the big one has not come, I like the little ones. That's the secret of my life I want to share with you.

Now I will conclude with sincere thanks to the Applied Mechanics Division for this heartwarming recognition from colleagues and friends. Thank you all, I wish you all the best.

1995 Timoshenko Medal Lecture by Daniel D. Joseph

2006-06-24T06:59:00.000-07:00

by Daniel D. Joseph , University of Minnesota

In my instructions about the correct behavior of recipients of the Timoshenko Medal at this dinner, Tom Cruse wrote to me that "While I ask that you consider the hour and the length of the evening in selecting the length of your remarks, the time is yours and we are honored to hear from you at that time." This suggests to me that as a Timoshenko Medalist, I can be indulged but that if I really want to be appreciated, I should keep it short.

I understand that when Jerry Ericksen got this award, he said "thank you" and sat down. I would like to follow this courageous path, but I lack the courage and so I will embellish "thank you" just a little.

Of course, I am pleased and honored to get the Timoshenko Medal and I am especially pleased to be introduced by my teacher and dear friend, Phil Hodge. I got my Ph.D. in 1963 at the Illinois Institute of Technology in Chicago. My advisor was L.N. Tao, but I took a graduate course in continuum mechanics with Phil when I was an undergraduate. It was a very demanding and quite unusual course with an emphasis on mathematical rigor at a level at which beginning students in engineering could understand. The course had a very important and permanent influence on my understanding of the mathematics of mechanics which influences me still.

At the University of Minnesota, Phil and I were running buddies. We even ran some marathons together; that is, we started together, then I saw his backside for a few minutes and three or four hours later, I could find him well rested at the finish. I ran 22 marathons; my best time for all of them was 3:42. In that marathon, Phil did it in 3:16 and was No. 1 in his old age group. My marathon running is like my career; not much talent, but very persistent. It is good for me that the Timoshenko Medal is also given to tortoises.

Applied mechanics was very strong at IIT in the early 1960's. The late Peter Chiarulli and Max Frocht were there then, and Eli Sternberg had been there not so much earlier. Another applied mechanician, Walter Jaunzemis, taught us a very thoughtful course on analytical dynamics which I appreciated greatly. He died as a young man. It is so sad to think of these ghosts of my past. My friend, Ronald Rivlin, who thank God is still alive and feisty, told me on the occasion of my 60th birthday that I was too old to die young. This is actually some comfort. It might interest you that Barenblatt and I are editing a collected works of Rivlin which ought to appear next year.

My relations with the people of applied mechanics developed more strongly at IIT than later. Peter Chiarulli arranged for me to present some work I did about Stokes flow over a porous sphere at an ASME meeting in a session chaired by George Carrier. He introduced me as Dr. Joseph. I wasn't a Dr., but George didn't know it. Later, he told me that he always played it safe. A little later, he saved me from later embarrassment by rejecting that paper. Too many mediocre papers were published in the 1960's and 1970's.

Jim Rice noted already in his acceptance speech of last year that the early 1960's was possi¬bly the best time to get a Ph.D. in mechanics ever. Due to Sputnik, there was lots of money for fel¬lowships, new faculty positions and research. I certainly benefited from this; I got a good job eas¬ily at the University of Minnesota in 1963 and my career advanced very fast. One consequence of the atmosphere of the time was to put a bigger than usual emphasis on foundations at the expense of applications. Many engineers in those days had an exaggerated idea of the power of abstract approaches. Mathematicians, and physicists too, have a good sense of the history of their subject. They know their heroes and who to emulate. We have not this sense of history in engineering and it leaves us rudderless and prey to foreign influences like those which, in the 1960's and 70's, led to the unnatural attempt to axiomatize mechanics.

It is probable that in recent times the pendulum has swung too far against abstract approaches based in mathematics in a kind of over-reaction which generally accompanies the correction of abuses.

My career can also be understood in two phases, the first emphasizing mathematics and the second, engineering. Actually, I could point to a third phase—the sociology phase, which came first. Some of you may know that I got a master's degree in sociology from the University of Chicago in 1950. Even though I have a master's degree in this field, I don't get much respect. The problem is that no matter how well educated you may be in sociology, the man on the street has his own opinion. Engineers are much better off because they get the benefit of the doubt.

Probably only a few of you know why I got this medal. Some years ago, when I had no honors and awards but Jerry Ericksen had many, I noticed that to get them, you needed to be certified. I told Jerry that the best kind of certification is that you have already got some honors and awards from elsewhere. Jerry then noted that "every dog knows where other dogs pee."

Joking aside, I owe so much to the string of superb students who have worked with me in these past years: Luigi Preziosi, KangPing Chen, Howard Hu, Pushpendra Singh, Adam Huang, Runyuan Bai, Jimmy Feng, Todd Hesla, Mike Arney, Joe Liu, Geraldo Ribeiro, Chris Christodoulou, Oliver Riccius, Joe Than, P. Huang and many others. These students worked with me on many projects; here, I will mention two: Hyperbolicity and change of type in the flow of viscoelastic fluids and the water-lubricated pipelining of heavy crudes.

In the 1980's, together with Michael Renardy and Jean Claude Saut, I found that the unsteady vorticity equation for many models of viscoelastic fluid is hyperbolic, giving rise to waves of vorticity. In steady flows, the vorticity field can be of one type here and another there, as in transonic flow. The other variables, stresses and velocities, are neither strictly hyperbolic and/or strictly elliptic. To me, it is surprising that with so much mathematical work coming from rational mechanics in the 1960's, 70's and 80's, that the problem of the mathematical classification of type of the governing PDE's was not joined.

The key quantity in the discussion of hyperbolic waves of vorticity is the speed of shear waves. We invented a device in 1986 to measure the speed of these waves. We must have measured these speeds in 200 different fluids by now. There are over 100 values published in my 1990 book on the Fluid Dynamics of Viscoelastic Liquids. You can compute a relaxation time for these speeds, and usually it is an order of magnitude smaller than what other people get by the devices they use. I think that conventional rheometers have a too slow response, most of the signal has decayed by the time those instruments kick in.

Using speeds measured on my device, I have correlated data from our experiments on delayed die swell, the orientational change of falling bodies, the change in the drag law of air bubbles rising in viscoelastic fluids and other anomalous effects that were reported in experiments, which I interpret as a change of type. If you use the speed we measure, you get a good agreement, but not otherwise.

I must confess that the rheology community, though not hostile, seems largely indifferent to these results which I consider to be so important.

Another topic on which we have worked, which I like greatly, is water-lubricated pipelining of heavy oils. It is a gift of nature that if you put water and oil into a pipeline, and the oil is viscous enough, say, greater than 5 poise, the water will go to the walls of the pipe where it lubricates the flow. You can get drag reductions this way of the order of the viscosity ratio. Crude oils with a viscosity of 1,000 poise are not uncommon. They can't be pushed through pipes at that viscosity, but with water there, they go through easily. You've got drag reductions of the order of thousands. This is a technology which has been used and it will be used more and more.

CNN found out about our work on this and did a short video segment on it which I am going to show you. That week, I had a tooth pulled and my face was swollen. Just my luck to have a swollen face on the road to stardom.

I have been asked many times if the lubrication of one fluid by another can be described by a variational principle. Strictly speaking, it cannot; however there is something in the idea of minimum dissipation which is best expressed in anthropomorphic terms. "High viscosity liquids are lazy. Low viscosity liquids are the victims of the laziness of high viscosity liquids because they are easy to push around."

MRS Bulletin features Macroelectronics

2006-06-18T09:46:00.000-07:00

The June 2006 issue of MRS Bulletin features Macroelectronics.

The guest editor of this issue include Robert H. Reuss (program manager of DARPA's macroelectronics program), Darrel G. Hopper (principal electronics engineer at US ARFL), and Jae-Geun Park (Materials Center at Samsung Advanced Institute of Technology)

The issue include a theme review article by the guest editors and four theme technical articles covering various topics related to macroelectronics.

(via www.macroelectronics.org)

KEVLAR is a modern material with many applications

2006-06-17T08:17:00.000-07:00

1999 Timoshenko Medal Lecture by Anatol Roshko

2006-06-17T04:16:00.000-07:00

Small is Good

By Anatol Roshko, California Institute of Technology

The text of the Timoshenko Medal Acceptance Speech delivered at the Applied Mechanics Dinner of the 1999 IMECE in Nashville, TN.

David Belden’s letter announcing the award was really a surprise, almost a shock. At first I wondered whether it was another example of a story which you may have heard and which, I believe, originated in the FSU. Two friends are at a grand reception sipping cocktails when one notices a man with his chest almost completely covered with medals. Says one to the other, “Do you have any idea what those medals are for?” and the other replies, “Well, you see that one at the top left? That one was a mistake; and the others followed automatically.” I humored myself out of that thought but not out of a feeling of guilt. You see, I suddenly felt terrible that I was not a member of the ASME. There had been opportunities but somehow I had let them go by. One reason is that I was concerned about another onslaught of communications, information and other paper that always results and requires attention. Fortunately, ASME lost no time in relieving my guilt. In a few weeks I received a nice invitation and forms to fill out, and now I am Member No.6143358. And sure enough, information has begun to roll in: a beautiful, glossy magazine, notices of various meetings, etc.

I sincerely thank those who put my name forward and the Division of Applied Mechanics for this honor. I want to assure you that, though not a joiner, my destiny has always been in Applied Mechanics, as you will see as my talk progresses.

Other medalists have had some acquaintance or connection with Professor Timoshenko. Mine is mainly through the ending “-ko”. I understand that there are some who think that Tim O’Shenko was an Irishman but, as most of you know, he was Ukrainian. The “-ko” is almost certain identification. So even though I did not have the good fortune to meet Stephen Timoshenko I feel some connection.

Originally, when informed by Dr. Belden about the award and tonight’s dinner, I assumed that it was going to be appropriate to make a few acceptance remarks and that something like what I just said would do it. Not being a member, I was not familiar with the rituals of the Applied Mechanics Division. So when, a few months later, Professor Needleman informed me of the custom, I again had a bit of shock, especially when he told me it should be a NON technical talk; and no blackboard, no overhead projector! And a written copy would be needed for the Newsletter! Well, I have here my illegible hand written notes which I hope to have in printable form before the due date.

What do you want to hear in a non technical talk? Humor? Advice? An appraisal of the field and projections for the future? Views on public policy for Applied Mechanics? I’m not very good at any of that. So I’ve modelled my talk somewhat on that of Professor Willis, the 1997 Medallist, whose acceptance speech I read in the AMD Newsletter and liked very much. Some back copies were kindly provided by Professor Needleman and Mr. Majewski.

The theme is “how to pursue a satisfying career in Applied Mechanics”, and I feel very satisfied with mine. I discovered the generalized formula only at the end of my career, but perhaps someone else can use it. Simply stated it is this: “Be in the right place at the right time.” But there’s an important caveat: the places should be small. I use the term “places” as a generalization for various entities, as you will see. Hence the title of this talk.

My career started in a small high school in a small coal-mining town in the Canadian Rockies. There were 15 in the graduating class. Bellevue High School provided me with an excellent education in the basics, up to introductory calculus. The town was an ethnic pot, it was poor, everyone in it was poor, but the three high school teachers had University degrees! I still don’t know how that worked and why it doesn’t seem to work so well now, but I think one clue may be in the word “small”.

From there I went to the University of Alberta, which at that time had a total enrollment of about 2500. I was in the Civil Engineering class, some 15 in all, but on a special track called Engineering Physics, which allowed me to substitute extra Math and Physics for courses like Concrete Mixing. The Eng. Phys. option was the brainchild of Applied Mechanics professors in the Civil Engineering Department (there was no M.E. Department at that time); they were mainly in Structures and Soil Mechanics. Many of them had gone to the University of Illinois for graduate work. One of them, my good friend George Ford, an Applied Mechaniker at heart, went to Stanford to work with Goodier, the son-in-law of Timoshenko who was still very active then. So I got to know a bit about Timoshenko from George Ford, who went back to Alberta and was instrumental in establishing an M.E. Department there.

From Alberta, after some diversions, I came to Caltech for graduate work in GALCIT. This is, effectively, the department of Aeronautics, but the Division of Engineering and Applied Science does not have Departments. I guess each department would be TOO small. Lucky for me; I got to teach some of the Applied Mechanics courses that George Housner and Don Hudson had established.

In 1946 the enrollment at Caltech was about 1500, half undergrad and half gradate. After half a century it has grown to about 2000, still half and half. Bigness is not big at Caltech. You probably noticed that US News and World Report recently ranked Caltech at the top of Universities in the U.S. (even though it’s not a University!). You may have also heard, at about the same time, another education story from LA County, namely the crisis in the Los Angeles Unified School District. It’s difficult to avoid comparisons—no, not with Caltech but with Bellevue High School. In fact, one of the proposals being suggested is to break up LAUSD into smaller units. About the size of the old Bellevue School District should be about right. (This ends my venture into Public Policy.)

I was fortunate to come into the orbit of Hans Liepmann the first day I arrived at Caltech. Much of my way of seeing and doing things has been influenced by him. Hans was wary of bigness. He liked to keep things lean: big funding brings big baggage with it; you should seek funding for research you want to do, not the other way around; research must be enjoyable to be productive; “smaller” makes it easier to recover from setbacks, even crashes, and so on.

Echoing Professor Willis’ observations, I believe that a productive career in research in Academia is helped by three elements, all related to the fact that research is nurtured by questions and questioning. An ideal mix is the combination of teaching, consulting and research; the elements of this triangle feed each other constructively.
To teach technical material convincingly it is necessary to understand it, and students encourage you to do so. Digging deeply often reveals gaps not only in your own understanding but often in the subject itself. When interacting with students at the research level we teach each other. Liepmann delighted in asserting that even before a PhD thesis is finished the student should know more about his subject than anyone else, including his advisor.

The second element of the triangle which leads to questions and questioning is consulting, using this term in the broad meaning of interaction with the outside world, whether it be industrial companies, government laboratories or other societal entities. My own work was strongly influenced by such activities. Observing engineers solve tough technical problems, with imperfect technologies at their disposal, gave me a healthy respect and admiration for how they get their jobs done, and it often left me with feelings of inadequacy to help. I also realized how inadequate even our best students may be feeling as they stepped out into the real world. This led to the introduction, with Don Coles, of a new course in our curriculum, officially called Technical Fluid Mechanics but unofficially Dirty Fluid Mechanics, the kind you can’t find in textbooks. This enabled us to pass on to our future engineers and researchers some extra help; at the same time it impacted our own research, by the feedback process I’ve mentioned. I suspect that there’s also a place for a course in Dirty Solid Mechanics.

The third corner of the triangle, scientific research, is at the apex. Feynmann called it “the pleasure of finding things out”. Exhilaration may be a better describer. I feel privileged to have experienced it. Professor Oden, in his 1996 acceptance speech, said “I have experienced this phenomenon many times. I am constantly amazed by it, but find it awkward to explain or rationalize”. I had thought to give a few examples here, but there’s no blackboard or overhead projector! But I have promised to write up one of them for Applied Mechanics Reviews.

It seems to me that it is the nature of Applied Mechanics research that it is best carried out by individual investigators or small groups. So it concerns many of us that the trend is toward large consortia of researchers who are supposed to interact with each other and across disciplines. This is inevitably directed research, about which many thoughtful people were concerned when government funding of research accelerated, continuing a process that had begun during World War II. Other thoughtful people point out that this is the only way that societal expenditures on research can continue and even increase, and that anyway there is no net loss to the undirected research that would and will otherwise flourish. Perhaps this trend toward more directed research should be viewed as a contribution to the consulting corner of the triangle which I described and that individuals may still be able to work on their creative ideas under the umbrella of a large consortium. A little moonlighting might be helpful. In fact, life could be very comfortable, except possibly for the Director. But, inevitably, creative people will be left out.

Also troubling is that bigness seems to be crowding out some of the culture that has served Applied Mechanics so well, i.e. the abstraction of well-posed scientific questions from important but messy practical ones (a phrase which I’ve borrowed from Garry Brown). As someone (Prandtl?) remarked, “there is nothing so practical as a sound scientific theory”. It is idealized models, leading to analytical descriptions, that reveal the innermost workings of nature, and they help develop the “intuition” which engineers need to do their “dirty” work. This culture should not diminish; it is already small.

Mr. Chairman, again I thank you and the Division for the honor you have given me, the ASME for signing me up, and you the audience for the opportunity of speaking to you.

A Second-Gradient Theory of Fluid Flow

2006-06-09T05:30:00.000-07:00

Recently, Eliot Fried and Mort Gurtin have developed general balance equations and boundary conditions for second-grade materials. Their work is set to appear in the Archive for Rational Mechanics and Analysis and is presently available online (DOI: 10.1007/s00205-006-0015-7). The theory essentially blends classical work by Toupin on elastic materials with couple stresses with a modern, nonstandard principle of virtual power developed by Gurtin. Importantly, the basic formulation is independent of constitutive assumptions, and as such, applicable to both solids and fluids.

Fried and Gurtin consider incompressible fluid flow as one such application. The approach effectively generalizes the Navier-Stokes equations to include higher-order gradients of the velocity field. Through constitutive assumptions, material lengths are naturally introduced in the flow equation and higher-order boundary conditions. Fried and Gurtin refer to the former as the gradient length, L, and the latter as the adherence length, l. This work is of interest because recent simulations suggest that at sufficiently small length scales, the classical Navier-Stokes equations and their boundary conditions fail to accurately describe fluid flow. The new theory provides a mechanism to account for these length scale effects, and being continuum-based, promises to be much more efficient than discrete methods such as molecular dynamics.

In particular, Fried and Gurtin consider the case of plane Poiseuille flow and derive analytical expressions for the velocity profile. If one considers laminar flow through a channel of height h, for example, gradient effects play an increasingly important role on the flow with decreasing ratios h/L of physical to gradient lengths. A plot of the flow profiles predicted by the theory is reproduced here in the Figure to the right. The theory allows for a range of flow profiles from the limiting cases of strong (l approaching infinity) and weak (vanishing l) adherence to the classical results predicted by the Navier Stokes equations.

Strength map of carbon nanotube

2006-05-29T06:22:00.000-07:00

In theory, carbon nanotubes are 100 times stronger than steel at one-sixth the weight, but in practice, scientists have struggled make nanotubes that live up to those predictions. This is partly because there are still many unanswered questions about how nanotubes break and under what conditions.

Recently, Prof. Boris I. Yakobson at Rice University, his former postdoc Traian Dumitrica (now assistant professor at University of Minnesota), and his doctoral student Ming Hua, have developed a new computer modeling approach to create a “strength map” that plots the likelihood or probability that a carbon nanotube will break—and how it’s likely to break. Four critical variables are considered in the model: load level, load duration, temperature, and chirality. This work was published in the Proceedings of the National Adacemy of Sciences (Apr. 18, 2006 Cover feature). Full text pdf file of this paper is available here .

1992 Timoshenko Medal Lecture by Jan D. Achenbach

2006-05-20T13:14:00.000-07:00

The Wages of Wave Analysis

by Jan D. Achenbach, Northwestern University

The text of the Timoshenko Medal Acceptance Speech delivered at the Applied Mechanics Dinner of the 1992 Winter Annual Meeting of ASME.

Ladies and Gentlemen, Friends and Fellow Members of the Applied Mechanics Division, I am grateful to the Applied Mechanics Division for honoring me with the Timoshenko Medal. When I think of the past recipients of this award, I must, however, stand here with a great deal of humility.

It appears that I am the first member of a next generation, the redoubtable sputnik generation, squeezed in between the elder statesmen and the baby boomers, to receive the medal. Undoubtedly many of my contempo¬raries, who have kept the field of applied mechanics on the move, will follow soon.

Two of my favorite colleagues, Ben Freund and Dan Drucker, participated in tonight's proceedings. Ben, who was one of my first Ph.D. students, has become famous for his work on dynamic fracture. I feel some kind of vicarious pride in his achievements. Ben is a very generous person, as was obvious from his introduction. I am happy Dan Drucker was here to present the medal. I have admired Dan since my graduate student days, not only for his achievements in applied mechanics, for which he received the Timoshenko medal many years ago, but also because he has been a consistent and forceful spokesman for basic and applied research in the high councils, in which he more than anyone else in applied mechanics has taken the time and effort to participate.

Let me tell you of the experience of a colleague who passed away some years ago. He had lived a virtuous life, and he was admitted to Heaven. When he entered the Gate he was briefed by an Angel who explained to him that the pace was relaxed in Heaven. There was plenty of funding for research. Researchers were taking their time, and they studied mechanics problems carefully and in depth. So the Angel said why don't you go to work, and give a seminar a year from now. No problem, our colleague replied, I did some work on the way over here and I can give a seminar tomorrow. The Angel thought for a minute and then said: Fine, but keep one thing in mind, Timoshenko, von Karman and G. I. Taylor will be in the audience. Our colleague decided to take some more time.

In a sense Timoshenko, von Karman and G. I. Taylor, as well as all those other recipients of the medal are in the audience tonight. But then again these luminaries of applied mechanics are in that same sense always in the audience in talks that you and I may give in the AMD sessions that we are attending this week. They have set the standards. Judging from the Sessions I attended we are, however, admirably living up to these standards.

I believe I am the first recipient of the Timoshenko medal who has never seen Timoshenko in person. When I arrived at Stanford as a Graduate Student in 1959, Timoshenko, who was on the faculty, had long since retired. I never saw Timoshenko, but I certainly saw his books. They were used in courses on advanced strength of materials, elasticity, shells, stability, vibrations and dynamics. My exposure to the Timoshenko approach was sandwiched in between a more classical European viewpoint and a more modern American one. Before I came to Stanford I studied in Delft, and took courses from Biezeno and Koiter, both got the Timoshenko medal years ago. The core course in solid mechanics was then and usually still is linear elasticity. Biezeno taught elasticity broadly based on Biezeno and Grammell: "Technische Dynamik", written in German. It was an excellent course but it still was a refreshing experience to be exposed by J.N. Goodier to the Timoshenko approach. After Stanford, I went to Columbia as a Post-Doc, and I decided to listen in on elasticity as taught by Ray Mindlin and I learned a good deal more, particularly since Mindlin included the inertia term. Biezeno, Goodier and Mindlin, all three were incomparable teachers with their own style and particular interests.

If I wanted to stretch the point of connections to Timoshenko, I could tell you that my advisor (C.C. Chao) did his work with Bruno Boley, who worked for Nick Hoff, who was a Ph.D. student of Timoshenko. The genealogy is right. Time marches on.

I have always been happy that, when asked what I do for a living, I can answer I work on waves, particularly when asked by someone outside the field. Waves conjure up thoughts of possibly destructive rapidly moving energies, and visions of sweeping motions propagating towards far horizons, or deep into unknown territories.

My address tonight is entitled "The Wages of Wave Analysis'", as in the "Wages of Sin", i.e., the recompense or return. The wages have indeed been many, certainly for me, but also in an infinitely more important sense for many fields of science and technology. I gave some thought to "Riding the Waves." As you probably know this is a surfer's term which would seem appropriate for a talk in Southern California. Some of you may recall that a num¬ber of years ago there was a movie entitled "The Endless Summer", the story of some surfers who go around the world to search for the perfect wave. My activities in the field of applied mechanics, of almost thirty years, have also been an endless summer looking for the perfect wave.

I received an important exposure to waves in solids in a course taught by J.N. Goodier. The book "Stress Waves in Solids" by Harry Kolsky was the textbook. The book was then already out of print and had not yet been published as a Dover paperback. One copy in a decrepit state was available, xeroxing hardly existed and my fellow students and I copied parts of the book by hand. J believe that was the first time the thought occurred to me that there was a need for another book on waves in solids. My own book Wave Propagation in Elastic Solids was published more than ten years later. I am sure that it has been xeroxed many a time, but pardon the plug, it is still available, in paper-back form.

In this country research on waves in solids was already in bloom when I started, thanks to the work of Harry Kolsky, Julius Miklowitz and Ray Mindlin, all departed from this world, and Werner Goldschmidt and C. C. Chao still very much with us. I learned much from these gentlemen, and also from Joe Keller, as well as from contemporaries such as Y. C. Pao, Subhendu Datta and Ajit Mali. Now there is a good-size group of younger workers in the field. The Wave Propagation Committee of the Applied Mechanics Division is more active than ever before.

Over the years I have tried to advance applied mechanics techniques to analyze wave motion in solids and acoustic media in several areas of science and engineering. There were the obvious applications to impact on structures and rapid crack propagation, but there were also applications that reached further from home base to structural acoustics, seismology and quantitative ultrasonics for nondestructive evaluation. These efforts had their ups and downs. They were least successful in seismology and most successful in nondestructive evaluation. It was hard to contribute to seismology in part because seismologists are very good at wave propagation theory, and they have been initiated in the mysteries of earthquake records. There was, however, a period in the seventies and early eighties when applied mechanicians did significantly contribute to the theory of ground motion and to the understanding of earthquake mechanisms with their recently developed models of rapid crack propagation and the associated radiated wave motion.

When I became interested in non-destructive evaluation in the mid-seventies, the field was dominated by applied physicists and electrical engineers. They had excellent abilities in instrumentation and they were interested in analysis and simulation but did not want to spend a lot of time on it. They welcomed help in the area of wave analysis. The perfect match. By now I have learned something about instru¬mentation and measurement techniques and they have adopted our analytical and numerical approaches. Some of the most knowledgeable men in NDE like Don Thompson, Bruce Thompson and Laszlo Adler are among my best friends, and we happily work together.

In the quest for quality of products, especially large expensive products such as planes, bridges and nuclear reactors, and to insure safety of these products, non-destructive testing will play an important role. It is an essential part of life cycle engineering as are other areas of applied mechanics such as fracture mechanics, or in a more general sense failure mechanics, damage tolerant design philosophy and retirement for cause procedures.

I had the privilege of being introduced by a former student. I have been very fortunate with students. It is a great responsibility to find an interesting, challenging and worthwhile topic for a student to work on, particularly since it generally has to be done within the constraints of available funding for specific projects. The choice has long-range consequences for the student. Ideally advisor and student would follow Wayne Gretsky's example. When Wayne Gretsky, who is often said to best hockey player in the USA, was asked the secret of his success, he replied "I never skate to where the puck is, I skate to where it's going to be." Knowing where to go is a good idea, because as Lewis Carroll wrote: "If you don't know where you are going any road will take you there", I might add including many wrong ones. A well defined objective helps. Let me tell another little story. Two men, say a graduate student and his advisor, were looking for work. They were in a flat country, like Holland, where you can see to the horizon. They arrived at a railroad crossing where a third man happened to be standing. The two men explained that they were looking for work and asked where they could find it. The man who was asked pointed to the horizon and said: "over there where the rails get together, that's where you can find work". The two men started to walk along the track, a long way. Finally one of them, probably the professor, stopped and looked back and said "dammit we passed it".

Once a good topic has been selected, the work's progress may be characterized by different sports metaphors. One would be like a golf game where the student accurately hits a single ball from hole to hole. The role of the research advisor would be that of the caddy who carries the golf clubs, occasionally advises on the selection of an iron or a wood, warns that the terrain may be rougher than it looks, points out some slopes, warns that the edge of the sand trap is closer than it may seem and applauds the good shots. A second would be like a tennis game where student and advisor bound all over the court to hit the ball in all directions until a point is scored. The final result may be better than in the golf game. I actually prefer to play tennis. Of course many of us dream of the quarterback/running back situation where the ball is handed off by the advisor on the one yard line for a single ninety-nine yards run and a touchdown.

A few hundred years ago a wise man said "Much have I learned from my teachers, even more from my colleagues, but most of all from my students." On a more prosaic contemporary level I might add, and much do I owe to the Agencies that have made my learning possible, particularly the Mechanics Division of the Office of Naval Research and the Basic Energy Sciences Division of the Department of Energy.

As you know there are some important signs on the horizon for changes in research funding from basic to applied research. Some of these changes are already halfway here. The National Science Foundation is presently considering its future. There will be less emphasis on basic science and more on education, applied science and technology transfer. There will be a switch from DOD funding to research for civilian applications. These changes will, it seems to me, offer excellent opportunities for us in applied mechanics. Applications of mechanics pervade every area of science and technology.

A recent article in Business Week dealing with the Federal Government's move toward a new science and technology policy that puts more emphasis on "practical research" was entitled "Hey, you in the ivory tower. Come on down". I believe that we in applied mechanics have always been ready to meet on the first floor with our colleagues in industry. Interaction with industry can be very stimulating and in the future many if not all of us will become more involved with mechanics problems for industrial applications. Remember that Timoshenko worked for many years for Westinghouse and Mindlin based some of his most interesting research on the needs of Bell Labs to understand the vibration of crystals.

An effective cooperation requires, however, the participation of someone on the company's payroll. A major problem is that many medium sized and small companies have long since fired their research and development engineers, including the one that worked in applied mechanics, as part of cost-cutting efforts to improve the bottom line or the last quarterly balance sheet or to service the debt from the last hostile takeover. We at universities can contribute in an important way to strengthen R&D efforts for product development and international competitiveness, but we must have colleagues at companies to cooperate with. So hey you out there in the boardrooms and penthouses of corporate America hire some R&D engineers.

An occasion like this tends to generate retrospection. I have tried to keep it to a minimum. I know I have been very lucky. Somehow I have always stumbled into the right places, the right people and pretty much the right problems to work on. Bruno Boley crossed my path twice, the first time at Columbia, the second time at Northwestern. Back in the early sixties Bruno had an idea for post-doctoral positions that had absolutely no strings attached. They were called preceptorships and they paid better than assistant professor jobs, a princely $1000./month. The money was provided by ONR through Hal Liebowitz, who was then the director of ONR's Mechanics Division. I was one of the first beneficiaries. I used the time primarily to round off my education. After 9 months at Columbia I went to Northwestern, and years later Bruno via a detour to Cornell arrived at Northwestern to become Dean. He established an environment conducive to our research work in mechanics. Special thanks go to Bruno. I also want to thank my former and present colleagues at Northwestern for keeping me on my toes. Starting with George Herrmann, and then John Dundurs, Toshio Mura, Leon Keer, Sia Nemat-Nasser, Zdenek Bazant, Ted Belytschko, John Rudnicki and Isaac Daniel, as well as our younger colleagues, Tak Igusa, Brian Moran and Sridhar Krishnaswamy. I thank them all for providing a challenging environment.

The Applied Mechanics Division was founded in 1927 by S. P. Timoshenko. It has a great tradition. In the Sadam Hussein sense the Applied Mechanics Division is the Mother of all Divisions of the ASME. In the regular sense the Applied Mechanics Division is the Mother of several other Divisions to which it has actually given birth over the years, but the Division remains strong and fertile. The changes in the research environment which I mentioned earlier offer great opportunities to our members for a bright future. I have been a proud member of the Division for almost thirty years, and I hope to be an active member for many years to come. Thank you for honoring me with the Timoshenko Medal. Thank you very much.

Mechanics of flexible macroelectronics -- an emerging field of research

2006-05-17T05:35:00.000-07:00

Flat-panel displays are rapidly replacing cathode-ray tubes as the monitors of choice for computers and televisions, a commercial success that has opened the era of macroelectronics, in which transistors and other micro-components are integrated over large areas. In addition to the flat-panel displays, other macroelectronic products include x-ray imagers, thin-film solar cells, and thin-film antennas.

Like a microelectronic product, a macroelectronic product consists of many thin-film components of small features. While microelectronics advances by miniaturizing features, macroelectronics does so by enlarging systems. Macroelectronic products today are mostly fabricated on substrates of glass or silicon; they are expensive, fragile and not readily portable when their areas are large. To reduce cost and enhance portability, future innovation will come from new choice of materials and of manufacturing processes. For example, thin-film devices on thin polymer substrates lend themselves to roll-to-roll fabrication, resulting in lightweight, rugged and flexible products. These macroelectronic products will have diverse architectures, hybrid materials, and small features. Their mechanical behavior during manufacturing and use poses significant challenges to the creation of the new technologies.

A recent review paper by Suo et al. describes ongoing work in the emerging field of research – mechanics of flexible macroelectronics, with emphasis on the mechanical behavior at the scale of individual features, and over a long time. The following topics have been discussed in the paper:

Why many macroelectronic systems will be organic/inorganic hybrid structures, and how they can be made flexible.
A way to realize stretchable electronics by using compliant thin-film patterns of stiff materials.
How to achieve high ductility of thin metal films on polymer substrates and fatigue of metal films subject to cyclic loads.
Cracking in brittle materials such as oxides, nitrides and amorphous silicon on polymer substrates.
Issues of interfacial debonding

References:

Crawford, G.P. (editor), 2005. Flexible Flat Panel Displays, Wiley, Hoboken, New York.
Nathan, A., Chalamala, B.R. (editors), 2005. Special Issues on Flexible Electronics Technology, Proc. IEEE 93, 1235-1510.
Z. Suo, J.J. Vlassak and S. Wagner, Micromechanics of macroelectronics. China Particuology 3, 321-328 (2005). (Check out the references of this paper for a comprehensive list of recent literatures in this emerging field of research)

(via www.macroelectronics.org)

The 18th Annual Robert J. Melosh Medal Competition

2006-05-16T11:28:00.000-07:00

The 18th Annual Robert J. Melosh Medal Competition for the Best Student Paper in Finite Element Analysis was held on Friday, April 28th, at Duke University. The Competition was inaugurated in 1989 to honor Professor Melosh, a pioneering researcher in finite element methods and former chairman of Civil and Environmental Engineering at Duke University. The event is made possible through generous gifts to Duke University from Elsevier, Sandia National Laboratories, and the extended Melosh family.

The Competition consists of two phases. In the first phase, candidates submit extended abstracts for consideration by the panel of judges. The names and affiliations of the authors are not provided to the judges during this phase. The competition is open to students who are no more than one year beyond the completion of a graduate degree. From the submitted abstracts, six finalists are selected to give oral presentations of their work at the Melosh Symposium. During the past few years, the Symposium has been hosted at UC Berkeley, Rensselaer Polytechnic Institute, and Duke University. The winner and Melosh Medalist is selected on the basis of the combined written and oral scores.

The Melosh finalists represent a young group of researchers with bright futures. Indeed, many of the past finalists have continued on to successful careers in computational mechanics at universities, national laboratories, and industrial research centers. The group of finalists selected for this year's competition are no exception:

Jose Andrade, Stanford University

Roman Arciniega, Texas A&M University

Homayoun Heidari, NC State University

Shanhu Li, Ohio State University

Roger Sauer, UC Berkeley

Haim Waisman, Rensselaer Polytechnic Institute

The judges for this year's Competition were Professor Tom Hughes, UT Austin, Professor JS Chen, UCLA, and Dr. William Scherzinger, from Sandia National Laboratories.

Dr. Homayoun Heidari was selected as the 18th Melosh Medalist for his paper entitled "Novel Subsurface Imaging Algorithms Based on the Finite Element Method." A list of past Melosh Medalists and judges is available at the competition website. A special issue of the journal Finite Elements in Analysis and Design will be assembled to commemorate the event.

Whence the Force of F=ma?

2006-05-07T18:39:00.000-07:00

This is the title of a three-part series published in Physics Today by Frank Wilczek, the Herman Feshbach Professor of Physics at MIT. Prof. Wilczek is considered one of the world's most eminent theoretical physicists, and is the 2004 Nobel laureate in Physics for work he did as a graduate student at Princeton University, when he was only 21 years old.

Prof. Wilczek contributes regularly to Physics Today and to Nature, explaining topics at the frontiers of physics to wider scientific audiences. The following series of his "musing on mechanics" won the Best American Science Writing in 2005:
Whence the Force of F=ma? 1: Culture Shock
Whence the Force of F=ma? II: Rationalizations
Whence the Force of F= ma ? III: Cultural Diversity

Prof. Wilczek recently published a book named Fantastic Realities, in which 49 inspiring pieces, including the above three, of "mind journeys" are included. This book also includes contribution from his wife Betsy Devine's blog on what winning a Nobel Prize looks like from inside prizewinner's family.
You may also enjoy a recent podcast of Scientific American, in which Prof. Wilczek and his wife talk about their new book.

1997 Timoshenko Medal Lecture by John R. Willis

2006-05-06T14:18:00.000-07:00

Mechanics of Research
The text of the Timoshenko Medal Acceptance Speech delivered at the Applied Mechanics Dinner at the 1997 IMECE.
by J. R. Willis, University of Cambridge

The award of the Timoshenko Medal is a singular and unexpected honour. I thank my friends who exaggerated my case so successfully, and promise them that I shall do my best to justify their faith in the future, even if I have not managed it in the past.

I’m not sure if I should say this, but I will. I have attended one Applied Mechanics Division Dinner previously. Bernie Budiansky received the Timoshenko Medal. I was surprised that he spoke for so long! Now I realize why. It was no ordinary after-dinner speech but the Timoshenko Lecture, and its length is prescribed. Therefore, I can only advise now that you settle down and prepare to let your thoughts wander!

A technical exposition is clearly not required, and I sought inspiration, or at least examples of how to proceed, by reading the lectures of a few previous medallists. It seemed to me that I might try to follow, in some approximate way, the path taken by George Batchelor, who was also my boss at a formative time in my career. He was founder and head of the Department of Applied Mathematics and Theoretical Physics in Cambridge.

I was fortunate enough to hold junior posts there, between 1965 and 1972, and perhaps am now even more fortunate to hold a senior post in that department. George is no longer its head but he is there every day, providing an example of dedication to research and scholarship in mechanics.

This, in fact, will be my theme: how does a career develop, in which perhaps the most significant component is research? Naturally, this will relate to applied mathematics and mechanics, because that is all that I know.

The main focus of George’s lecture was how an institution should be organised to stimulate invention and research, and I shall try to address a somewhat similar question.

Yapa Rajapakse asked me the other night what would be the title of my talk. I told him that I hadn’t given one, but perhaps an appropriate title would be “Mechanics of Research”. My concern will be how an individual should position himself or herself, to do fruitful research. So, in particular, what should someone just starting out do, and expect?

To begin, it pays to be good at passing exams. Otherwise, acceptance in a good research school is likely to be difficult. It pays also to have a thesis adviser who has the right sense of what might be important in the future as well as tractable now, with the right amount of effort. This is not always so easy to achieve. Paul Matthews, a physicist of great distinction (I knew him when he was Vice-Chancellor of the University of Bath, where I spent many happy years as a Professor), told me that, when he was a young research student in the Cavendish Laboratory, he one day approached Paul Dirac and asked him if he might be willing to supervise his research. Dirac’s response, utterly sincere and modest, was that he didn’t need any help with his problems at that time.

Few of us have the opportunity to acquire such an anecdote. There is, however, an uncomfortable lesson to be learned by all at this stage. Being clever may be necessary, but it certainly is not sufficient! It is still more important to have commitment and true interest in what you are doing. While a bit of competitive spirit is surely no bad thing (and may be almost essential), the pleasure of achievement against your own standards should be -- probably has to be -- your main reward, since it is certain, whoever you are, that you will see people around you who have more talent, and have done much more significant research than you are ever likely to do yourself. I am reminded here of another story I was once told. I am not sure now whether it was told me by Jock Eshelby, or about him: as a young research student, he went to see a great elder statesman of solid state physics, and asked what were the really significant areas in which an aspiring researcher should concentrate. The reply was, “I don’t know. And if I did, I wouldn’t tell you!”. Or perhaps Jock was the elder statesman: those that knew him can surely imagine him making such a response, mixing humour with truth! The fact is that, unless you are exceptionally lucky, you have to have your own ideas and be satisfied with them.

Having done your first research, and obtained your PhD, the next problem is to find a position which will allow your research to flourish. I wish I could advise here. My own experience is useless, since when I was at that stage, there were more good jobs than there were people to fill them, and I remember with appreciation one of the services my thesis adviser, Maurice Jaswon, rendered at that time. He took sabbatical leave in the USA, and I was able to monitor some of his movements from job offers that I received. I actually took a post-doctoral position at the Courant Institute, New York, and had the benefit of learning from some of the greats of applied mathematics, including Joe Keller, another Timoshenko Medallist. There are two problems now, or so it seems to me.

One is that jobs are scarce. The other is that there is pressure to behave immediately as though you are a great leader, attract research funds and perhaps have more graduate students than is comfortable for you or them. I do believe that foundations have to be laid, by personal study and contemplation. Better to become a motivator and facilitator later! And in any case, you won’t survive long-term as a generator of ideas, unless you are doing quite a bit of research personally. Clearly, these days, some compromise is necessary. I would like to think that talent is recognised not only by amounts of money attracted, or numbers of publications, though it would be quite wrong to infer that independence from these activities as demonstrated by failure to deliver necessarily implies true commitment, or ability, or depth. A positive aspect of the grant culture is that research driven by practical concerns can have fundamental significance and, even when it does not, involvement in such research can provide a perspective from which important generic or fundamental problems may be identified.

Assuming that you keep going successfully, and achieve a senior position either in a University or a Research Department, you surely will acquire wider responsibilities. These are likely to include responsibility for the welfare (and livelihood) of others, and may also involve administration concerning the research infrastructure of your discipline.

I think particularly here of activities relating to publishing. We almost all act as referees (except for those — some very distinguished — who just don’t respond!) and some of us act as journal editors.

I have to admit that I sometimes suspect that people these days write more than they read -- including, in some cases, papers upon which the person’s name appears as author! But enough of that, and back to the functions of an editor. This is not a research activity, but (I do my best to remind myself) it does make an important contribution to the collective scientific endeavour. Furthermore, although you certainly can’t please everyone all the time, it is my experience that the job can make you more friends than enemies. The thing to remember is that you can’t know everything, so you must take the best advice that you can find and then (even when the advice is inadequate, as it can be on occasions!) take a decision in as honest a fashion as you can. Just occasionally, you may have the opportunity to promote some of the first work of someone destined to be a star. This is a real satisfaction. And this reminds me of something else that goes with age and seniority: if you become a head of department -- or similar -- and have the opportunity to make appointments, you must never be afraid of appointing someone you suspect may be better than yourself. I have done this many times. Not only is it essential for the well-being of your unit, but you actually derive credit as well as benefit for your own research.

I realize that I started with the intention of making general comment but have lapsed into personal reminiscence. Now I would like to do this still more explicitly. Certainly the progress of my career has been influenced greatly by various colleagues that I have had. After NYU, I went to Cambridge on the initiative of Rodney Hill.

Of course he is impossible to emulate, but I saw an example towards which to aspire. Also at Cambridge, I interacted with Jock Eshelby, whose papers had already been one of the foundations of my education. I always knew that my main contribution would be mathematical, and I learned important lessons from Gerard Friedlander and Edward Fraenkel in particular.

When I was still relatively young, I moved to the then new University of Bath. Over the next few years, I had the great good fortune to appoint outstanding colleagues, and I learned some more mathematics particularly from John Toland. I also had several excellent students and post-docs. In particular, David Talbot was my student more than 20 years ago. He is still a major collaborator and I am happy to acknowledge my debt to him. One of my best post-docs was Pedro Ponte Castañeda.

Again, we have interacted over the succeeding years to my distinct advantage. When I first returned to Cambridge, I was fortunate to have Pedro as one of my early visitors. Another was Walt Drugan, who was never my student or post-doc but I wish he had been. This is one of the advantages of working in a location that others consider attractive. In the three and a half years I have been back, I have had the benefit of a succession of distinguished long-term visitors including, besides Pedro and Walt, Huajian Gao and Zvi Hashin. I have also, in recent years, done my own share of travelling, and my most frequent single destination has been the laboratory of Sia Nemat-Nasser, where there is always something new and exciting for me to learn.

Travelling and editing a journal do not form an ideal mixture, and would have been much more difficult to combine if I had not had the fortune to have Ben Freund as an outstanding co-editor of JMPS. During periods that I am away, he continues -- I expect -to feed copy to the press, so that short absence is not a problem.

One of the most significant world events of the last few years had impact on me and my research too: the demise of the Soviet Union made available many researchers of great ability, prepared to take more junior positions than objectively they deserved. In my case, I had successively as post-docs Sasha Movchan, Valery Smyshlyaev and Natasha Movchan. I can only liken working with them to driving a powerful car: you touch the accelerator and really move! They all three now have secure positions and do not need me, but still we collaborate, and I get (some of) the credit for their hard work and talent.

This, perhaps, leads me to my final piece of advice: when you get the chance, collaborate with talented younger researchers as much as you can. Few activities can be more rewarding. In my case, this goes a long way towards explaining my presence this evening. Now I would like to conclude, expressing my deep gratitude to all those with whom I have had the good fortune to interact during my career so far, coupled with keen anticipation of more in the future.

1993 Timoshenko Medal Lecture by John L. Lumley

2006-04-22T04:05:00.000-07:00

John L. Lumley

I am profoundly honored by the award of this medal. Awards like this are made, of course, not by faceless organizations, but by collections of individuals, voting in rooms which are no longer smoke-filled; it is particularly gratifying to find that so many of my colleagues think I am worthy of this honor. As Jan Achenbach remarked last year, we are of the sputnik generation, too young to have known Timoshenko, who, in fact, did have some connections with Cornell long before I came there. Although I have spent my life in fluid mechanics, I began by taking all the standard courses in solid mechanics: strength of materials, elasticity, plates and shells, buckling; in nearly every one there was a text by Timoshenko or a friend or relation, all admirably clear. I felt very grateful to him.

I would like to mention that the three ASME medal winners this year (Roger Arndt, David Crighton and I) were all together at Penn State in the Aerospace Engineering Department and the Garfield Thomas Water Tunnel, under the leadership of George Wislicenus about thirty years ago. Roger and I were on the faculty, and David came in the summers as a consultant. I think that says something about the vision and values that George used as he built his group.

I have heard a story about L. M. Milne-Thomson, whom we all know for his work on theoretical hydro- and aerodynamics. Many years ago he was asked to speak after dinner at a grand banquet in the Washington area. He may have been given an award; I am not sure. The banquet was attended by wives in elegant dresses, and there were naval officers of flag rank in class A uniforms. To everyone's surprise, he said that he wanted to give a technical lecture. After a short delay they found a tiny portable blackboard, and as he covered it with equations, he had two full admirals erasing for him in relays, tossing the eraser back and forth to each other over his head. I won't do that this evening.

Instead, I want to talk about becoming a scientist and being one, during the latter part of the twentieth century, in the United States. I realize that, when people reach my age, they think that anything they have to say is golden. I am reminded of Eric Walker, former president of Penn State. When he retired, he started writing a column in the local newspaper called "Now it's my turn". Many of us thought it had already been his turn for entirely too long, and his column was not too popular. I will try to spare you that syndrome as much as possible, but some of it is unavoidable. If the Medal Committee had any decency, they would not require a speech, and we would all be spared.

My father was an architectural engineer, and a do-it-yourself craftsman, car buff and spare-time artist. My earliest recollections are of being allowed to wash the spokes of the artillery wheels on our Hudson, while Dad polished the car with the chamois. We always had a car that was a little bit special, a little different. As we drove around Detroit, Dad would point out buildings that he had had a hand in designing or building. On Saturday mornings I remember being taken to completed buildings and building sites, and having the various flaws pointed out to me. Dad was a very demanding man; everything had to be just so. Ann Landers recently had a letter describing engineers as uncompromising, inflexible and perfectionist. That was certainly Dad. One of his friends said that Charlie was a wonderful guy, but he would hate like Hell to work for him. For years my mother talked about the dog house Dad built. It was large enough for a child to play in, with insulation and a shingled roof, and a baffle at the door to keep the cold wind out. It was a lot better built than many houses for people - certainly than the ones in Dade county in Florida. Dad never did manage to teach me how to do lettering and make arrowheads on drawings in a thoroughly professional manner, though God knows he tried. He also tried to get me always to make a complete set of drawings before I fabricated something; it never took - I always preferred to plan the project in my head, and make modifications as I went along; very unprofessional. Dad had ambiguous feelings about engineering, and from time to time thought he might have been happier as an architect. He once asked me if I was prepared to spend my life among these gray, inarticulate people. That's not entirely unfair, though I have grown rather fond of many of these people, who are only gray if you don't look beneath the surface. And there are not many, but enough poets and artists among us, so I am happy.

This is really how I got into engineering. I have always loved machinery, making things, building things. But I have spent my life as a research scientist, which is not quite the same thing. It seems that when I work on a problem, even a practical problem, I turn it into a research project; I chop it up finer and finer until there is nothing left but the fundamentals. In fact, half the theses I have supervised were experimental - a good experiment is a little closer to engineering; you usually have an opportunity to design some piece of equipment, and see it come into being. That, of course, is not quite the same as making it yourself. Evenings and weekends I restore old cars out in the barn - that satisfies the urge to make things. It also satisfies the craftsman-like desire to design in your head, with the materials and tools at hand, and modify as you go along. I get tired of too much calculation, too much precision, which I get enough of professionally. In addition, what I do professionally has a very delayed payoff - something of the order of twenty years or more. It is nice to do something that provides shorter-term gratification. It is also peaceful out in the barn.

There is less dichotomy than you might think, however, between what I do professionally and what I do evenings and weekends. I believe it was von Karman who said "There is nothing so practical as a good theory". I have always felt when constructing a very mathematical theory, that I was constructing something real and practical, to explain something physical, to make design possible. I have always been deeply offended by the attitude we meet so often, "it's just a theory", although I am certainly used to it.

More important, perhaps, I have always wanted to be involved with real things. That is, I have never wanted to abstract what I do too much, remove it too far from the real world, from the application. When I was in graduate school, it was rather nice to work on clean, neat problems that were somewhat removed from the real world. When I got my first job with George Wislicenus at Penn State, I was connected with the Garfield Thomas Water Tunnel, as well as with the Aerospace Engineering Department. The water tunnel is the world's largest high speed water tunnel, and is a part of the Applied Research Laboratory, that Penn State operates for the Naval Sea Systems Command. The Laboratory is responsible for various aspects of undersea warfare. At the Water Tunnel I was quickly immersed in the very practical problems arising from torpedoes and submarines: primarily various schemes for reduction of turbulent skin friction drag, and the many problems connected with testing in the water tunnel. At first I was a little appalled by the complex interdisciplinary problems. I had been unconsciously trained to be a bit disdainful of real problems; somehow, if you were concerned with real problems, it suggested that you didn't have the wit to find the fundamental problem underlying the real problem. It seemed that, to be socially acceptable in my circles, you never mentioned the real problem, but only the fundamental problem that you had abstracted from it. I discovered fairly fast that this was not such a straightforward matter, and that the business of reducing a real problem to a series of connected fundamental problems, all simple enough to resolve, without throwing out the baby with the bath water, was very challenging. Of course, in this reduction process you have to clip away everything that seems extraneous, hoping to be left with something that, while only a skeleton, still shares enough with the real problem to shed light on it. I think my colleagues often thought that I had pruned a bit too much, leaving a stunted stub that could not survive. However, even if they could no longer see the connection, I always saw the theoretical result as still directly connected to the real world. I also quickly came to see what a tremendously rich environment this was, how stimulating, how many problems there were to solve. I think it is a great mistake to get too far away from the applications; you dry up, you starve.

In the last few years I have managed to combine my hobby and my profession. When I was a relatively junior faculty member, I taught undergraduates. As I became more senior, however, I taught only graduate students, and for many years this was true. When I went to Cornell, I was told that I would have to teach undergraduates, but in fact I was never asked, and I never volunteered. Three years ago, however, I was made an offer I could not refuse, and I am now responsible for the undergraduate course in automotive engineering, with between fifty and one hundred students. This is one of our capstone design courses, and is a nice synthesis of much of what the kids have learned in their other courses. It is fun to teach, and I enjoy the undergraduates, although they still frighten me a bit. The young can be very judgmental and demanding. I think it helps to have raised some children. The first year I taught the course, my teaching evaluations were appalling - I hope the dean never sees them. I must say they were richly deserved. Now, however, the evaluations have substantially improved, and they no longer give me nightmares.

As I have gotten older, I have found that more and more I am a research administrator. I am sure I am not unique - this happens to all of us, but it is a bit sad. That is, I have less and less opportunity to do things myself. I am supervising others who are having all the fun. The world of science in which I live and work is structured differently now from the way it was when I was young. The world itself is changing, but of course it is also changing for me because I am getting older. The changes are also not uniform from country to country. In any event, at present, at my age, in this country, a successful scientist must have a large operation, which means a hand-full of contracts, students, post-docs, colleagues, visitors. This is a nice environment for the people working in it - I try to make it that way, recalling my earlier years. I certainly was very grateful for the environment that my thesis advisor created around us. Mostly that is simply a matter of collecting an interesting group of people, and letting them interact. I was an only child, and when I was little I became accustomed to playing by myself. Probably because of that, what attracted me to science was the pleasure of working alone at a problem uninterruptedly, following thoughts to their conclusions, trying various possibilities. I now recognize that that is not always an efficient way to work - it sometimes makes more sense to break off, and sleep on a problem, or do something unrelated, or go to the library and read something that someone else has said on the subject. That was something I never wanted to do when I was young - I didn't care what someone else had said - I wanted to do it myself. In any event, this lovely environment for everybody else is not really a nice environment for me. Whether it is desirable or not, uninterrupted work is rarely possible for me. I function in the interrupt mode, which I understand is the norm for managers. In addition, I do virtually nothing myself, but must act collaboratively with others, and at second hand. This makes me feel somewhat like a child who is forced to share his toys.

Gertrude Stein compared politicians to garbage collectors; they do necessary, but not very exciting, things that keep the place running, and are not really noticed until the system breaks down and the garbage is not collected. Administration is a lot like that, even research administration. A lot of what I do these days is the moral equivalent of garbage collection.

When I came to Cornell, of course I no longer had a connection with the water tunnel and its sophisticated but practical problems. At Cornell, I have found a certain satisfaction in being an expert witness and consultant. The problems that I solve in this capacity are reminiscent of the problems that I enjoyed resolving when I was younger. They are practical problems, usually complex and interdisciplinary, which must be broken up and abstracted to be resolved. This process involves some technology transfer, since I am often applying fundamental things that my research has taught me over the years to industrial or environmental problems.

Sometimes it is like detective work. Let me tell you about something I worked on last year, that will illustrate how a complex, interdisciplinary practical problem can lead to fundamental problems. This is in the area of atmospheric turbulence, in which I worked for some years at Penn State. Some of the material may be unfamiliar, but I think you will find the logical chain interesting. My client was a sheep farmer whose sheep seemed to be dying as a result of emissions of sulfur dioxide and hydrogen sulfide from a heavy water plant. Both sulfur dioxide and hydrogen sulfide are toxic in sufficiently high concentrations. The farmer was just a kilometer and a half from the plant, which is very close, but any normal calculations suggested that his sheep were receiving concentrations at a level considered completely safe. In addition, monitoring stations placed near his farm indicated low concentrations. I must explain how Hydrogen sulfide and sulfur dioxide happened to be emitted. Hydrogen sulfide is used in the process of making heavy water, and once a year the towers in which the heavy water is made have to be cleaned. After as much hydrogen sulfide as possible has been removed from the towers, the majority of the remainder is burned on a flare stack and converted to sulfur dioxide. The plant was right on the edge of one of the great lakes, and the stack was close to the water. After several false starts, we finally realized that the on-shore breeze from the lake, during the spring and summer, was stably stratified, and thus not turbulent, from traveling over the cooler lake water for hundreds of kilometers. The top of the stack was in this stably stratified air. Thus, the stack plume did not disperse. The cool, stable air, when it started over the warmer land, began to grow an internal turbulent boundary layer, and when this reached the height of the stack plume, the plume was sucked into the first downgoing eddy, and taken to the surface. The distances were about right so that the place where this happened was right over my client's farm, and the first descending eddy was probably caused by his cool, insulated farm buildings. His sheep were thus getting the stack plume at nearly full strength. The plume, of course, did not descend on the monitoring station. The matter was complicated by the fact that the sulfur dioxide was considerably heavier than air, and could lie on the ground in hollows among the vegetation, where the sheep would be immersed in it.

This general situation is called shoreline fumigation, and is well-known to meteorologists. However, they are only familiar with the average effects. The phenomenon of the descent of the instantaneous plume to ground level, with its associated high instantaneous concentrations, has not been measured. One of my colleagues has now submitted a proposal for laboratory measurements of instantaneous concentrations in this situation. In addition, the pooling of the sulfur dioxide at ground level, and the probability of its remaining for various periods, was a nice little fundamental problem that was fun to solve.

Everything has its down side, and I must admit I don't much like being questioned in hearings. In addition, this was all part of an environmental impact hearing in connection with a request for license renewal for the heavy water plant. When it became evident that my client had a case that would stand up, the request for license renewal was withdrawn. As a result, the outcome is moot. Also, although I work hard at communicating my results, I sometimes suspect that my clients find my name and credentials more useful to them than my findings. That's all right - at least I had fun.

Well, I hope I have kept you awake. Let me thank you again for this wonderful honor you have bestowed on me.

A Virtual Tour of the 1906 Great Earthquake in Google Earth

2006-04-18T19:39:00.000-07:00

The California earthquake of April 18, 1906 (one century ago today) ranks as one of the most significant earthquakes of all time. Today, its importance comes more from the wealth of scientific knowledge derived from it than from its sheer size --it marked the dawn of modern science of earthquakes.

U.S. Geological Survey (USGS) recently provides a virtual tour utilizing the geographic interactive software Google Earth to explain the scientific, engineering, and human dimensions of this earthquake. This virtual tour can help you visualize and understand the causes and effects of this and future earthquakes.

Enjoy this virtual tour to explore how Google Earth (and other new softwares...) can facilitate and improve the way we teach and conduct research.

Organic LED could replace light bulb?

2006-04-17T06:56:00.000-07:00

Lighting accounts for about 22% of the electricity consumed in buildings in the United States, and 40% of that amount is eaten up by inefficient incandescent light bulbs. The search for economical light sources has been a hot topic.

Recently, scientists have made important progress towards making white organic light-emitting diodes (OLEDs) commercially viable as light source. As reported in a latest Nature article, even at an early stage of development this new source is up to 75% more fficient than today's incandescent sources at similar brightnesses. The traditional light bulb's days could be numbered.

Read media report here.

A new wiki is set up to solve the Millennium Problems in Mathematics

2006-04-16T04:24:00.000-07:00

This entry in Slashdot links to the new wiki, from which one can at least learn what these problems are, as well as their prize tags. The 139 comments in Slashdot once again show the issues concerning any wikiscience project.

Nanogenerators created by a team led by Zhonglin Wang

2006-04-13T18:02:00.000-07:00