Teng Li's blog

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Post-Doc position on surgical simulation at University of Maryland, College Park

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

 


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iMechanica now has over 3000 registered users

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


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Minutes of iMechanica get-together at McMat 2007

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.


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Post-doc position: Surgical Simulation in a NIH project

From Prof. Jaydev P. Desai at University of Maryland

Post-Doc Position


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Engineering education in the age of Web 2.0 -- Explorations through iMechanica.org

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). 


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Flexible Macroelectronics (a video for middle/high school students)

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


 


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IBM Airgap Microprocessors enabled by self assembly (Video)

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


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iMechanica now has 2000+ registered users

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.


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Online meeting scheduling

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.


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The future role of iMechanica

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.


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Delocalizing Strain in a Thin Metal Film on a Polymer Substrate

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


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Mechanics of flexible macroelectronics

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:


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Gecko, Spiderman and Climbing Robot (Video)

I am at Boston for MRS 2006 Fall meeting this week, where I met a real "spiderman" at the poster session tonight. I'd like to share with you the following videos which were posted at YouTube by the "spiderman" himself, Mr. Jose Berengueres at Tokyo Instititute of Technology.

Mr. "Spiderman" also has posted a video on fasting climbing robot.


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The Future of Cell Phone?

Here is one answer from Nokia.


Nokia 888 communicator, a concept design which recently won the Nokia's Benelux Design Award. It uses liquid battery, flexible touch display, speech recognition, touch sensitive body cover which lets it understand and adjust to the environment. It has a simple programmable body mechanism so that it changes forms in different situations. Don't forget to enjoy a video demo of this cell phone of future.
Yet one more future application of flexible electronics, it's clear there're great mechanics and materials challenges in making electronic devices flexible. It will be great mechanicians can help accelerate the advance of this emerging technology.


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How to post a video?

Sometimes a video can be more convenient and effective than words on delivering a message. Now you can embed videos in your post in iMechanica. As a demonstration, I first embed a video below I made previously on how to make hyperlinks in your post. If you're interested in posting a video in iMechanica, read the following instructions:



How to embed a video in your post?
Step 1: Sign up a free account at YouTube.com, a website you can share videos online. Upon sign up, you can upload videos to YouTube. Follow the easy directions there. Of course you may want to read copyright tips of YouTube before uploading.
Step 2: Once uploaded, your video will have a Unique URL. You can always provide a hyperlink of the video in your post. To directly embed the video into a post, you need to use the html code automatically generated by YouTube, which you can easily find below the unique URL in the video information. Copy the entire html code.
Step 3: Since the current setting of the default text editor of iMechanica (those MS-word-type buttons above the textbox, called TinyMCE) does not support video yet, you need to turn it off and just use plain html. To turn off TinyMCE, click "my account" on the left sidebar, then click "edit" tab. Below "Account information" box, find "TinyMCE rich-text settings" and click it to expand the box. In the Default state, it shows "true" (means TinyMCE is on). Click the drop-down list and choose "false" . Scroll down to the bottom and click "Submit". Now TinyMCE is turned off.
Step 4: Start to post a new entry. Now you should see a Body textbox without any buttons. Paste the YouTube html code into the box. You can add any description above or below the code. If you want, you can also use any html editor to prepare your post and copy/paste the entire html file into the box.
Step 5: Preview your post then submit. Now all iMech users can view your video without leaving your post!
Of course, you can always turn TinyMCE back on by repeating Step 3.
We're still improving the video function in iMechanica. If you have any creative ideas to better achieve such a function, welcome to leave your comment below.
Enjoy vlogging in iMech.

 


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Symposium: Mechanics of micro/nano structures on soft substrates: applications for flexible and stretchable electronics

The SES 2007 Conference, Oct. 21-24, 2007, Texas A&M University campus in College Station, Texas, home to the George Bush Presidential Library and Museum.

Call for abstract

Symposium: Mechanics of micro/nano structures on soft substrates: applications for flexible and stretchable electronics


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Looking for a job in academia?

Finding an academic job is like finding a perfect match. Universities advertise openings, you choose a list of places to apply. Nowadays an opening can easily attract hundreds of applicants, of which several are invited for on-campus interview. When the whole process is over, there might be a perfect match between you and a department (Congratulations!), while sometimes there is not.


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Video Demo: How to make hyperlinks in your post?

In a recent post, Zhigang Suo explains how to add hyperlinks in your post. We all understand how hard to write an instruction for a simple operation, so we should appreciate Dr. Suo's every effort trying to be elucidative.

If you prefer a visualized instruction, click here to watch a video demonstration on how to make a post in your blog at iMechanica, and how to add a hyperlink in your post.


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nanoHUB: online simulations and more

The nanoHUB is a web-based initiative spearheaded by the NSF-funded Network for Computational Nanotechnology (NCN). Based at Purdue University and partnered by eight other universities, nanoHUB provides a web interface to numerous resources relevant to students and practitioners in nanotechnology. The cyber environment includes online courses and tutorials, proceedings of seminars, collaborative tools, and an interface for online simulation.

For example, you can view research seminars on nanoHUB through online slideshow with audio, powered by Breeze technology. You can go over the outline of the seminar, choose thumbnail views of the slides and even search text within the titles of the slides, then locate the content of interest and save some time. Another type of resource on nanoHUB is the online simulation tools, which run realtime on nanoHUB. No installation is needed.

The nanoHUB resources are open to public for free. You just need to register to use. In the last eight months, nanoHUB has served more than 10,000 users, with about 60,000 simulation jobs run and more than 10,000 videos viewed. The web server hits of nanoHUB reach 1 million in May 2006.


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MRS Bulletin features Macroelectronics

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)


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Strength map of carbon nanotube

 

 

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.


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Whence the Force of F=ma?

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
.


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A Virtual Tour of the 1906 Great Earthquake in Google Earth

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.


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Organic LED could replace light bulb?

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.

(Via www.macroelectronics.org)


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