Giving presentations at conferences or seminar series is a vital part of a researcher's professional life.  Listening to others' presentations is also one of the best ways to stay current with the frontier of a research field. While the audience in conference/seminar room is often limited, a presentation posted online can be virtually viewed by any interested audience. At iMechanica, users have started to post their presentation slides, quite often as the attachments of a post briefing the presentation.  Such a way is simple and effective, but may not be the best way for everyone for the following reasons:

We study the effects of grain boundary adhesion and grain size on the ductility of thin metal films well bonded to polymer substrates, using finite element method. It is shown that the ductility of polymer-supported metal films increases approximately linearly as the grain boundary adhesion increases, and as the grain size decreases. A rule-of-thumb estimate of the ductility of polymer-supported metal films agrees well with the simulation results.

In press, Scripta Materialia, 2008 

DOI: 10.1016/j.scriptamat.2008.06.058

Dear fellow iMechanica users,

Many of you have experienced unstable access to iMechanica recently.  To our best knowledge, such unstable performance can be related to the fast-growing user volume of iMechanica. We have been working with Lesley Lam at OIT of Harvard School of Engineering and Applied Sciences to cure such growing pains of iMechanica.  We apologize for any inconvenience due to unstable access to iMechanica, and appreciate your understanding while we're working on this issue.  The support from all of you has been vital to iMechanica since day one and will continue to be so for the years to come.

The number of registered users of iMechanica reaches 7000 on 11 May 2008. So far, our fellow iMechanicians have contributed 3172 posts and 7425 comments.  The evolving statistics of iMechanica
(see the latest updates here and here) shows a steady growth with no sign of slowing down. 

Check out the earlier milestones of iMechanica when the number of registered users reached:

6000

Dear fellow iMechanicians:

After some technical problems over the past weekend, iMechanica is now back on full service. We apologize for any inconvenience this may cause and thank for your patience.

We are particularly grateful to Ms. Lesley Lam in OIT of Harvard School of Engineering and Applied Sciences for her prompt fix of the problem.

Well-known for its high yield strength, metallic glass often suffers from its low ductility and intrinsic brittleness, as discussed in a recent iMech jClub theme on plasticity and failure in metallic glasses led by Yanfei Gao.

As the most rigid cytoskeletal filaments, microtubules bear compressive forces in living cells, balancing the tensile forces within the cytoskeleton to maintain the cell shape. It is often observed that, in living cells, microtubules under compression severely buckle into short wavelengths. By contrast, when compressed, isolated microtubules in vitro buckle into single long-wavelength arcs. The critical buckling force of the microtubules in vitro is two orders of magnitude lower than that of the microtubules in living cells.

From Prof. Weidong Zhu at
University of Maryland, Baltimore County

At 71, Physics Professor Is a Web Star

Most frequently e-mailed by NYTimes.com readers in the past 30 days, the above article features MIT physics professor, Walter H. G. Lewin, on how his free physics lecture videos online have won him devotees all over the world.

While preparing a talk on iMechanica , I came across the following video "Information R/evolution" by Michael Wesch, an assistant professor of anthropology at Kansas State University.  This thought provoking video echoes a recent comment on "The future of knowledge?"

Enjoy!

Attending conferences is one of the essential professional activities for scientific researchers. Conferences take various forms, such as community-wide meetings (e.g., MRS meetings, ASME congress, APS meetings), and topic-focused meetings/workshops (e.g., Plasticity07, Gordon Research Conferences(GRC)).  While people have different preferences on the types of conference to attend (e.g., see a recent iMech poll initiated by Biswajit Banerjee ), here are some common positive driving forces to motivate one to attend a conference:

On September 20, 2007, Harvard School of Engineering and Applied Sciences (SEAS) was officially launched .   SEAS emeritus Gordon McKay Professor of Systems Engineering and T. Jefferson Coolidge Professor of Applied Mathematics,  Yu-Chi Ho, wrote a blog entry about the history of Harvard engineering.  Interesting to we mechnicians is that the original benefactor Mr. Gordon McKay specified in his will that his huge furtune is to be used to support " mechanical engineering and related arts". As a result, the first strong group established was the applied mechanics group.

Prof. Ho's blog entry is available at:

From Prof. Jaydev P. Desai at University of Maryland:

The number of registered users of iMechanica exceeded 3000 today, three months after iMechanica welcomed its 2000th user.  The number of posts has exceeded 1700, and the number of comments, 3800. The growth of iMechanica has been stable and amazing, leading to a natural question: why do people register at iMechanica? iMechanica is open:  evevryone can read everything without registration.  You can post anything of interest to mechanicians once you register for a free account. 

On 6 June 2007, about 50 mechanicians attended a special session at the McMat 2007, "iMechanica.org get together". The attendees of this special session came from various job sectors, such as academia, industry as well as government agencies. The session was chaired by K. Ravi-Chander and Rui Huang, who also served in the organizing committee of McMat 2007.

From Prof. Jaydev P. Desai at University of Maryland

Post-Doc Position

Abstract: Web 2.0 refers to a collection of second generation web services, such as blogs, social bookmarking, wikis, podcasts, and Really Simple Syndicates (RSS) feeds.  While the first generation web (Web 1.0) is about linking information available online, Web 2.0 emphasizes online collaboration and sharing among people.  These new web services bring up new opportunities to innovate how we conduct research and education. We report the preliminary explorations of engineering education exploiting Web 2.0 services, through iMechanica (http://imechanica.org). 

This is a winning entry in the Sci/Terp Video Competition at University of Maryland (UMD).

An earlier post by Xiaohu Liu reported IBM's latest progress in microprocessors. IBM has figured out how to control and perfect the self assembly process to create trillions of tiny, nano-sized holes across a chip, which speed electrons that flow across wires inside the chip and reduce the power consumed by 15 percent.The following short video may help us understand a little bit more about the new technology. More videos, audio and images on this are available here (free, but registration needed)
Enjoy.

-Teng

iMechanica was lunched on 9 September 2006. It took about five months for iMechanica to see its 1000th registered user. Today we are welcoming the 2000th registered user after only another two and half months.

Scheduling a meeting with more than 3 participants can be a headache. The organizer often needs to email or call the group, and wait for feedbacks. Quite often both the organizer and the participants need to go through such a process several rounds to finalize the schedule.

Now you can schedule meetings online. The organizer proposes a series of possible time slots and provides the email list of the participants. Each participant will receive email notice from the system with a link to the time slots, where they can just click to choose. The participant can then view the availability of others. Once a time slot works for everyone, the organizer can confirm online then the system will notify every participant.

Since iMechanica went official on 9 September 2006, its growth has always been accelerating. As of 22 February 2007, the total number of hits on iMechanica reaches 1,000,000+, iMechanica has 1252 registered users, 908 posts and 1308 comments.

Teng Li, Zhenyu Huang, Zhichen Xi, Stephanie P. Lacour, Sigurd Wagner, Zhigang Suo, Mechanics of Materials, 37, 261-273 (2005).

Under tension, a freestanding thin metal film usually ruptures at a smaller strain than its bulk counterpart. Often this apparent brittleness does not result from cleavage, but from strain localization, such as necking. By volume conservation, necking causes local elongation. This elongation is much smaller than the film length, and adds little to the overall strain. The film ruptures when the overall strain just exceeds the necking initiation strain, εN , which for a weakly hardening film is not far beyond its elastic limit. Now consider a weakly hardening metal film on a steeply hardening polymer substrate. If the metal film is fully bonded to the polymer substrate, the substrate suppresses large local elongation in the film, so that the metal film may deform uniformly far beyond εN. If the metal film debonds from the substrate, however, the film becomes freestanding and ruptures at a smaller strain than the fully bonded film; the polymer substrate remains intact. We study strain delocalization in the metal film on the polymer substrate by analyzing incipient and large-amplitude nonuniform deformation, as well as debond-assisted necking. The theoretical considerations call for further experiments to clarify the rupture behavior of the metal-on-polymer laminates.

Related posts and discussions

Tension of Cu film on Pi substrate
Local thinning of Cu film
High ductility of a metal film adherent on a polymer substrate

The following entry was first posted in www.macroelectronics.org on 8 May 2006.

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: