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Split singularities and the competition between crack penetration and debond at a bimaterial interface

Zhen Zhang and Zhigang Suo

For a crack impinging upon a bimaterial interface at an angle, the singular stress field is a linear superposition of two modes, usually of unequal exponents, either a pair of complex conjugates, or two unequal real numbers. In the latter case, a stronger and a weaker singularity coexist (known as split singularities). We define a dimensionless parameter, called the local mode mixity, to characterize the proportion of the two modes at the length scale where the processes of fracture occur. We show that the weaker singularity can readily affect whether the crack will penetrate, or debond, the interface.

Zhigang Suo's picture

How to make long distance phone calls for free

Like many other communities, we mechanicians are scattered all over the world, often separated from families and colleagues. The Internet has promised for years to make long dstances irrelevant: anybody anywhere is just a click away. While nothing will ever be the same as being together in person, many Internet services can facilitate distant communication and collaboration. For example, Skype, an Internet phone service, allows you make free phone calls around the world. The sound quality is excellent.

Zhigang Suo's picture

Pay per paper (P3)

(Originally published on Applied Mechanics News on 22 July 2006, where many comments provided remarkable insight)

I’ve just stopped subscribing to Science. The magazine is great, but few papers in it interest me. The signal-to-noise ratio of Science, I guess, is just too low to most individuals. Instead, I’ve now subscribed to the RSS feed of Science. If any paper looks interesting, I can access to the full paper online through Harvard Libraries. Outside my office, a color printer is free to use for everyone. A library of an institution seems to be an ideal home for a journal like Science. Nearly every individual paper in Science is of high enough quality to appeal to someone in the institution.

Few journals can make that claim, however. Most journals are only relevant to several people in an institution. Furthermore, few researchers read any scholarly journal from cover to cover. Rather, we all read individual papers. However, libraries subscribe to journals, or even bundles of journals. As a result, the libraries pay for many papers that nobody reads, and miss other papers that someone would like to read.

This business model is bad for authors and readers, and possibly even bad for publishers. Technology now exists to distribute information far more efficiently, in a unit consistent with how people consume the information. For example, many people now prefer buying individual songs to albums. See a recent book, The Long Tail, by Chris Anderson, the editor-in-chief of Wired, for a remarkably perceptive analysis of media industries.

The same business model may apply to scholarly papers. One may argue that journals, like albums, were invented as a packaging technology to suit the old economics of delivery. As scholarly papers are all online, the name of a journal becomes simply a tag to the papers published in that journal. Maybe a powerful tag, but a tag nonetheless. So far as how papers should be distributed, the name of a journal should serve the same function as all other tag-like entities: keywords, names of authors, etc: the tags help readers to sort papers and set priorities. It makes no sense for anyone to insist that papers with any particular tag be delivered as a bundle.

Many publishers already offer individual papers for sale online; for example, the cost is at $30 per paper for many Elsevier journals. Once a reader buys a paper, it seems reasonable to share this paper with his close colleagues, and it also seems reasonable to store the paper for future use. Perhaps we can formalize this practice.

How about we treat a paper just like a book? With one click, a reader will have the paper, and his library will automatically pay for it. Once bought, the paper is accessible to every user of the library. We can also collect statistics. If the users of a library buy many papers in a journal, the library should subscribe to the journal. Libraries will set up an algorithm to minimize the total cost. Publishers will set up their algorithms to maximize profits. However, libraries and publishers do have a common ground: they both want to help people to find papers.

To support such a business model, a third party may provide a web service. It seems to be too wasteful to make every individual library and every individual publisher maintain a separate web service. Something like Amazon.com or Last.fm for papers might do. The service can also be an extension of services like EZproxy or CiteULike.

Zhigang Suo's picture

The LibraryLookup Bookmarklet

(Opriginally posted on Applied Mechanics News on 8 July 2006)

Quick link added on 12 July 2006. Here is a list of LibraryLookup Bookmarklets for many libraries, along with an instruction to use them.

Zhigang Suo's picture

Libraries and Amazon

(Originally posted on Applied Mechanics News on 25 June 2006)

Libraries take premium spaces, which will not grow and will likely shrink. As more and more books are stored in off-campus depositories, people miss the serendipity of browsing among shelves and discovering books that they don’t know they’d like to read. They can browse the catalogues of the libraries. However, a typical catalogue of a library contains meager information: the online catalogue is a clone of its ancestor on cards. Creating an information-rich and user-friendly online catalogue is too expensive for a library.

These problems have a solution. The primary source of data on books is Amazon. It contains publisher-supplied data such as cover images, table of contents, index, and sample material. Searchable full texts are within reach. Perhaps even more valuable, Amazon contains comments of users on books. Based on collective behavior of users, Amazon also recommends books to users. Amazon will no doubt continue relentless innovation.

In an ideal world, a user should not waste his time on the catalog of a library, nor should the library waste its resources on maintaining a stand-alone catalog. The user should simply browse on Amazon. Once he finds an interesting book, a single click should tell him if the book is in any of the libraries accessible to him. In this ideal world, to enter a book into the catalog of a library, a librarian only needs to enter a single number: the call number of the book. All other data of the book are not library-specific and are already in Amazon. What if the library owns a book not in Amazon? The librarian should enter a detailed description of the book, as if she were the publisher of the book.

This ideal world may not be far different from our world. The LibraryLookup Project allows a user to generate a bookmarklet, so that with one click he can look up a book in a library, while surfing on Amazon. The creator of the Project, Jon Udell, has developed a screencast to guide you through the process of generating your own bookmarklet.

A deeper integration of Amazon and libraries would harness more power. The statistics of borrowing books could be aggregated from all libraries and be used to recommend books to users. Amazon, libraries and some third party could collaborate on the business of print on demand. Libraries could send even more books to depositories and greatly simplify efforts in cataloging books. Users would have a seamless experience with books. Oh, if a book is not in a library, users could suggest, with a single click, that the library order the book.

Ending added on 26 June 2006, after reading a message from Zak Stone. Amazon.com is named after the Amazon River, the largest river in the world, carrying more water than the next six largest rivers combined. May the rivers of libraries and the streams of users contribute to the River of All Books. May Amazon.com nurture the civilization without drowning us with commercialism.

Note added on 10 July 2006. An entry describes my experience with LibraryLookup Bookmarklets.

Note added on 15 July 2006. Wall Street Journal (13 July 2006) on Rice University's Press on line and print on demand (POD). For an example of comercial POD, see lulu.com. Also see a recent product annoucement of e-reader.

Note added on 17 July 2006. OCLC and Amazon: A Connection Revealed.

Note added on 27 July 2006. Springer will offer all new titles in e-book form.

Note added on 20 August 2006. Amazon introduces library processing.

Note added on 31 August 2006. Google offers free download of books.

Note added on 31 August 2006. Stanford's vision for library.

Zhigang Suo's picture

What's wrong with Applied Mechanics?

(Originally posted on Applied Mechanics News in 16 May 2006)

Zhigang Suo's picture

Connexions: knowledge as commodities

(Originally posted on Applied Mechanics News on 2 May 2006)

A twelve-year old found a blueprint to assemble a computer in a magazine, and ordered parts on newegg.com, a website that listed parts from all vendors and comments on each part by customers. Both features were reassuring. When the parts arrived in mail a week or two later, the boy assembled the computer himself. In the process, he saved a substantial amount of money. He also learned a lot about computers, and about dealing with his parents.

The boy could do all these because computer parts are commodities, products that are produced by different companies but conforming to the same standards: all parts fit. Websites like newegg bring the parts from the companies directly to boys and girls of all ages, skipping middlemen like Dell.

Commoditization has also occurred in the software industry, largely due to the open-source movement that has produced the Linux operating system, as well as a large number of other software systems.

Can we also commoditize knowledge? This is precisely the mission of the Connexions Project, founded by the electrical engineer Richard Baraniuk, of Rice University, in 1999. The Project has been funded by the National Science Foundation and private donors, and has produced a system of software to enable anyone to author parts of knowledge (called modules). It also enables anyone to assemble parts into a functional product of knowledge (called a course), free of charge, under a Creative Commons open license. By January 2006, Connexions hosted over 2900 modules and 138 courses.

Connexions will likely have tremendous impact on the textbook industry, which has an annual revenue of 10 billion dollars in the US alone. The Project is also bringing free, up-to-date knowledge to developing countries, including North Karea.

Connexions will also likely to change the practice of scholarship. If you'd like to learn how Connexions works, you may visit the website of Connexions, or look at a course, or read a white paper written by the Connexions staff, or simply enjoy a video of an inspiring talk given by Professor Baraniuk to Google engineers.

Notes added on 15 July 2006. Wall Street Journal (13 July 2006) reported on Rice University's Press on line and print on demand.

Zhigang Suo's picture

Wikipedia and Applied Mechanics

(Originally posted on Applied Mechanics News on 25 February 2006)

Zhigang Suo's picture

Plan activities of the Applied Mechanics Division at 2007 ASME Congress

The ASME International Mechanical Engineering Congress and Exposition (IMECE) will be held in 11-16 November 2007, in Seattle, Washington. As the 2007 Program Chair of the Applied Mechanics Division (AMD), I hope to get you involved in planning activities at the Congress.

IMECE is a place where you can meet people and attend talks in Applied Mechanics, as well as in other fields, such as Materials, Electronic Packaging, Tribology, and Heat Transfer. For many mechanicians, a highlight of the Congress is the Applied Mechanics Annual Dinner, where old acquaintances are resumed, new friends made, awards announced, and the Timoshenko lectures delivered.

Teng Li's picture

What can mechanics community learn from the success of Google?

A cartoon in The New Yorker magazine shows a boy asking his dad a question. The dad, reading a book, replies, “Go ask your search engine.” The cartoon was published in Feb. 2000, three months before Google officially became the world's largest search engine with its introduction of a billion-page index — the first time so much of the web's content was made searchable. If the boy asks again today, his dad will say, “Go ask Google.”

At $6 billion a year in revenue and $7.6 billion in cash, Google is a success. What’s more important to the rest of us, Google is running its business in a way that may change the world. Through its never-about-average products (i.e., Google search, Google Earth (and Mars too), Google Map, and more recently, Writely), Google is radically redefining the ways we obtain, organize, use, store, and share information.

Teng Li's picture

Review Articles on Flexible Electronics

[img_assist|nid=46|title=|desc=|link=url,http://www.materialstoday.com/2006_issues/april.htm|align=right|width=75|height=100]The cover story of the April 2006 issue of Materials Today features Flexible Electronics. This issue also includes two review articles in this emerging field of research. Access to full text articles is free of charge at http://www.materialstoday.com.

Review Article:

Material challenge for flexible organic devices, by Jay Lewis

Review Article:

Organic and polymer transistors for electronics, by Ananth Dodabalapur

Cover Story:

Jet printing flexible displays, by R.A. Street et al.

Zhigang Suo's picture

Applied Mechanics in the Age of Web 2.0

The ASME International Applied Mechanics Division has about 5000 members. The number is too large for us to know each other individually, but too small for CNN to cover us in the Situation Room.

Then came the Internet. We have since been in touch through emails, and looked up each other on the Web. Many web pages created in 1990s, however, are static. For such a web page, the bottleneck is often the webmaster. He or she gets a request each time anyone wants to post anything. It is more like a broadcast than a web.

In recent years, there have been waves of new internet phenomena, such as Wikipedia, Real Simple Syndicates (RSS), open-source movement, and web logs (blogs). They are collectively known as Web 2.0.

A new home for mechanics researchers

Zhigang is really a master of good ideas. He learned the new technology from his son months ago, and then so many good ideas have been popping up in the mechanics community. Google group was the first trial, then google blog, wikepedia, etc. Now even fancier, iMech. I dreamed before, if I had money, I would buy a series of products by Apple. Now and in the future, I wish I can obtain iMech for free. I wish it has the quality as other products of i*** by Apple, but not as expensive as those. Good news is that the iMech is made by Zhigang, not Apple.

Zhigang Suo's picture

Let us seize the greatest opportunity of our time

We've been hearing rumors that print is dead, killed by the Internet. What is the reality then? For example, how are newspapers doing? Not too badly, according to the numbers cited by James Surowiecki, of The New Yorker. He also made the following remarks, however.

"The popular conviction that papers are doomed may cause owners and shareholders to prefer the cash-cow approach, accepting eventual oblivion while continuing to harvest billions of dollars in profits. Settling for a tolerable short-term future, newspapers could end up writing themselves out of the long-term one. Yet it’s also clear that this moment of supposed doom represents a sizable opportunity for newspapers, a chance to reinvigorate their product and, eventually, improve the economics of their business."

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