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A website wholly devoted to buckled shells

John Hutchinson has just pointed out to me the website, shellbuckling.com.  The site is devoted to the mechanics of buckled shells, with downloadable photos, slides, papers, and computer codes.  The site also has a section on buckling people.  The site is created by a veteran buckling person, Dr. David Bushnell, formerly of Lockheed Martin.  Check the site out, and enjoy. 


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西安交通大学 国际应用力学中心(ICAM)全球诚聘tenure-track PI及博士后

 (本招聘广告有效期至2012年12月31日)PDF of this file

为了更好地聚集海外优秀人才、培养国际一流的青年学者、及借此加快建设世界高水平大学的进程,西安交通大学建立了一个新型的、采用美国先进的用人和科研体制管理的研究中心---“国际应用力学中心” International Center for Applied Mechanics (ICAM)。该中心的目标是聚集和培养一流人才,产出一流学术成果,打造国际一流的力学学科。ICAM以独立的tenure-track PI为本,将重点研究国际力学前沿问题及国家重大需求中的关键力学问题,承担国家级的重点和重大项目,并开展高层次国际合作与交流。

ICAM是西安交通大学的一个独立的学术机构,参照美国常春藤盟校的高效和高度扁平化的科研管理体制。中心的学术带头人为国际著名的中青年力学家锁志刚、高华健、陈曦、刘子顺等西安交通大学杰出校友。中心的国际学术顾问包括Hutchinson,Willis,Needleman等世界力学大师。在他们的指导和引领下,ICAM将汇集和激励青年学者成长为有国际影响力的国家级人才。作为西安交通大学机械结构强度与振动国家重点实验室的一个“学术特区”,中心的人才招聘、薪酬、考核、评估、管理与运行等均参照美国的先进体制进行。ICAM实行独立的tenure-track PI制度,使得青年科研人员能够最大限度地发挥其创造力和主导作用,在国际著名学者的指引和激励下快速成长为具有国际能见度的一流学者(且不存在成长的上限)。ICAM将给每位tenure-track PI配备相应的独立的实验室空间和科研平台建设费,研究生招生和国际交流计划单列(不受传统名额限制)。中心的运行模式、人员岗位、人才培养和经费预算等均具有高度灵活性,可为每位tenure-track PI量身定制其发展轨迹。中心充分鼓励有共同兴趣的研究组在中心内部开展全面合作,并大力支持PI和校内外的其它学科(如机械、能动、电子电气、材料、航空航天、土木、生物生医、物理、化学等)的国际国内学者开展广泛的交叉研究。在学校的鼎力支持和中心全体人员的共同努力下,力争在较短时间内将ICAM建设成一个具有鲜明学科交叉特色、拥有世界一流研究水准和较高国际影响力的力学研究中心、成为国际力学学科前沿的领头羊之一。


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Add Google Scholar Citations to your iMechanica account

Sukumar pointed out a Google service to retrieve your papers.  Here are a few examples:


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Empirical observations of temperature

I have divided the old notes on temperature into three parts:

Our feeling of hotness comes from everyday experiences. These experiences indicate that many levels of hotness exist, and that all levels of hotness can be mapped to a real variable.


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Principle of the conservation of energy

The world consists of moving parts: stars, planets, animals, electrons, protons, photons, etc. Their movements and interactions carry energy. Energy is a fundamental concept. We do not know how to define energy in terms of more fundamental concepts. We do know many ways to keep track of energy. For example, we know how to calculate the kinetic energy of a flying bullet, and the gravitational energy of a weight. We can measure the electrostatic energy in a capacitor, and the elastic energy in a spring. We can look up the values of energy in all kinds of food. We can find similar numbers for fuels—coal, oil, gas. Energy in foods and fuels are stored in chemical bonds.


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Carnot Cycle

(Class notes for ES 181 Engineering Thermodynamics.  Also part of my notes on thermodynamics)  In 1824, Sadi Carnot (1796-1832) published a short book, Reflections on the Motive Power of Fire. (The book is now free online. You should try it out.) To construct an engine, Carnot noted, at least two reservoirs of energy of different temperatures are needed. He further noted that the engine loses efficiency whenever the working fluid of the engine exchanges energy with the rest of the world across a finite difference in temperature. To avoid such exchange of energy, he described a specific cycle—later known as the Carnot cycle—consisting of isothermal and adiabatic processes. Whenever the working fluid exchanges energy with either reservoir, the temperature of the working fluid is kept the same as that of the reservoir. Whenever the temperature of working fluid differs from the temperatures of the reservoirs, the working fluid is thermally insulated. He argued that this cycle is the most efficient of all cycles that convert heat to work by operating between two constant-temperature reservoirs of energy.


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Mechanics for soft machines

I gave a seminar at Xian Jiaotong University on 27 October 2009.  I recently found the video of the seminar online.  The seminar was in Chinese, but the slides were in English.

If the subject interests you, the following papers will lead you to the literature.


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Lithium batteries--When mechanics meets chemistry

When I learned chemistry in college, the subject was presented to me with equations of chemical reactions.  It took me some time to realize a couple of simple points:  reactants need to meet to produce a product, and compounds take space.

The connection between chemistry and mechanics is made vivid to me in recent years in studying lithium batteries.  As an example, here is a recent paper when chemistry is linked with plasticity, mass transport, and fracture—essential ingredients of solid mechanics.

Kejie Zhao, Matt Pharr, Joost J. Vlassak and Zhigang Suo. Inelastic hosts as electrodes for high-capacity lithium-ion batteries. Journal of Applied Physics 109, 016110 (2011).


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Whitesides on how to write a paper to communicate your research

George Whitesides has published over 1,100 papers.  In 2004 he published a three-page essay “Whitesides’ Group:  Writing a Paper”.  I have been asking all my students to study this essay when they begin to work with me.  Now you can watch Whitesides on video explaining his approach to publishing papers.    


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From esoteric research in continuum mechanics to first commercial product of dielectric elastomer transducers (1956-2011)

I’ve just come back from EuroEAP 2011, the First International Conference on Electromechanically Active Polymer (EAP) Transducers & Artificial Muscles.  The technical program was exciting.  The meeting was chaired by Federico Carpi, and took place in Pisa, Italy.  The weather was cool, and air fresh. 

Also in the air was optimism for the new technology of dielectric elastomer transducers.   The potential of soft dielectrics as a broad-ranging technology was first brought into focus by a SRI team in a paper published in Science in 2000.  The technology is based on an extremely robust electromechanical coupling.  A membrane of a dielectric elastomer is sandwiched between two compliant electrodes, such as those made of carbon grease.  When a voltage is applied between the two electrodes, one electrode becomes positively charged, and the other becomes negatively charged.  The opposite charges cause the membrane to reduce thickness and expand area.  Linear strains beyond 100% have been achieved.  Many videos of dielectric elastomer transducers are available on YouTube.


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Elastomer in equilibrium with forces and solvent

A long polymer consists of many monomers. The monomers are covalently bonded, and two bonded monomers may rotate relative to each other. Consequently, the polymer may be modeled as a chain of many links, each link representing a monomer. At a finite temperature, the polymer rapidly changes from one configuration to another.

A large number of long, flexible polymers can be crosslinked by covalent bonds to form a three-dimensional network. Subject to forces, the network undergoes large elastic deformation. The network is commonly called an elastomer.


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Thermodynamics 0, 1, 2, 3

In teaching the elements of thermodynamics in the graduate course on soft active materials, I have followed this sequence:

  • Isolated system:  a system capable of no variation. Entropy, S.
  • Temperature: a system capable of one independent variation. Entropy is a function of energy, S(U).
  • Pressure:  a system capable of two independent variations. Entropy is a function of energy and volume, S(U,V).
  • Chemical potential: a system capable of three independent variations. Entropy is a function of energy, volume and the number of water molecules, S(U,V,N).

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Temperature vs. chemical potential

For the third time I am teaching the graduate course on soft active materials.  This course is called Advanced Elasticity in the Catalog of Courses.  In the last several years, I have dropped several traditional topics, and focused on thermodynamics and finite deformation.  I have added several topics where both thermodynamics and finite deformation play significant roles, such as elastomeric gels and dielectric elastomers.


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Professor in Computational Mechanical and Materials Engineering at Harvard University

The Harvard School of Engineering and Applied Sciences (HSEAS) seeks applicants for an appointment at the level of tenured professor in the field of computational mechanical and materials engineering. The ideal candidate will have high expertise in computation, and will also have a demonstrated commitment to significant and innovative applications in mechanical engineering and/or materials engineering.

Successful candidates will have enthusiasm for teaching both graduate and undergraduate courses in engineering and applied computational science, and work with HSEAS faculty to develop a curriculum for our ABET-accredited engineering program.


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Who was PhD advisor of Prager?

I have been asking colleagues this question for some time.  I was a Ph.D. student of John W. Hutchinson, who was a Ph.D. student of Bernard Budiansky, who was a Ph.D. student of William Prager.  But for years, the Mathematics Genealogy Project listed the advisor for Prager as “unknown”.


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Teaching Engineering Thermodynamics to Undergraduate Students

I have just volunteered to teach engineering thermodynamics to undergraduates in the Fall semester of 2011.  The students will be from all fields of engineering, primarily mechanical engineering, environmental engineering, and bioengineering.  I have never taught this course before, and would love to hear from you about your experience, either as a student or as a teacher. 

Here is what I have found from the website about the course.

Engineering Science 181 Engineering Thermodynamics

Introduction to engineering thermodynamics with emphasis on classical thermodynamics. Topics:


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Worldwide Electroactive Polymer Newsletter

The latest issue of the WW-EAP Newsletter is now available.  I’m pleased that the issue includes my submission on a recently completed review on the Theory of Dielectric Elastomers.  As usual, the Newsletter contains lots of extremely valuable information, such as new books in the field, and new products.

The Newsletter has been edited by Dr. Yoseph Bar-Cohen.  Past issues of the WW-EAP Newsletter are archived online.


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Set up your ResearcherID, and let the world know about your publications

In 2008 I wrote about ResearcherID, a service provided by the publisher of the Web of Science.  The service is now used by many mechanicians.  Here are several examples:


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Theory of dielectric elastomers

In response to a stimulus, a soft material deforms, and the deformation provides a function. We call such a material a soft active material (SAM). This review focuses on one class of soft active materials: dielectric elastomers. Subject to a voltage, a membrane of a dielectric elastomer reduces thickness and expands area, possibly straining over 100%. The phenomenon is being developed as transducers for broad applications, including soft robots, adaptive optics, Braille displays, and electric generators.


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Bird Nest Plan at Huazhong University of Science and Technology

The "Bird Nest Plan" Research Center aiming at recruiting and nurturing young future leaders in emerging interdisciplinary science and technology has recently been launched at Huazhong University of Science and Technology (HUST).


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Report of the Chair, The Applied Mechanics Division, 2010

This report will appear in the 2010 Newsletter of the Applied Mechanics Division, of the American Society of Mechanical Engineers.

Mary Boyce called one day, in late 2004, asking if I would serve on the Executive Committee of the Applied Mechanics Division (AMD). I said yes. She told me that she would seek the consensus from other members of the Committee, and that meanwhile I should think the matter over. I did not have much to think about, but she did come back to me. On 1 July 2005, I replaced her as a new member of the Committee. Five years flies by, and I am now writing to you as the 2009-2010 Chair of the Division. The AMD is run by its members, volunteers like you and me. You have many ways to participate in shaping the Division and our field. I will highlight some of these ways in this report.


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A new textbook: Elasticity and Geometry, by Audoly and Pomeau

 From hair curls to the nonlinear response of shellsThe publisher sent me the other day this new book by Audoly and Pomeau.  I haven’t gone through the book carefully, but a quick look has indicated that this is a very special book, well worth a close reading.  The book is beautifully written and well produced.  The authors have captured the recent excitement about thin elastic objects, such as rods, plates, and shells.  While existing books on plates and shells mostly focus on calculating critical loads for instability, this new book describes shapes produced by instability.  Examples include wrinkles in a leaf, ridges in a piece of crumpled paper, and curls of a hair.  The subject is photogenic, and the book contains a large number of delightful illustrations.  The book approaches the subject through physical phenomena, rather than mathematical formalisms.  The authors have intended it as a text for a course at the level of senior undergraduate students or beginning graduate students.         


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Lectures on Soft Active Materials, 3rd edition

At the invitation of Yonggang Huang, I’ll give 4-hour lectures at the NSF Summer Institute Course on the Mechanics of Soft Materials.   I attach the slides of the lectures, to be given on Monday, 10 May 2010.  An abstract of the lectures follows.


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A new book: The Mechanics and Thermodynamics of Continua

Book_blurb_v1.pdf - Adobe Reader

 Early this year Amazon sent me a recommendation of this book by Morton Gurtin, Eliot Fried, and Lallit Anand.  I pre-ordered this book, which arrived the other day.  The authors are active and distinguished scholars.  The publisher has done an excellent job in producing the book.  It is simply a joy to hold the book in your hands, and read. 

As you can see from the table of contents posted on Amazon, the book consists of 114 Sections.  Each section reads like an essay, focusing on a particular idea.  The book is concerned with formulating field theories, and is excellent for graduate students and researchers in mechanics, especially those interested in creating new theories and computational methods.  I have requested our library to order a copy. 


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