ANDREW R KOENIG

ANDREW R KOENIG

 

 

Andrew R. Koenig (born June 1952) is a former AT&T and Bell Labs researcher and programmer. He is the author of ‘C Traps and Pitfalls, co-author (with Barbara Moo) of Accelerated C++ & Ruminations on C++, and his name is associated with argument-dependent name lookup, also known as “Koenig lookup”. He served as the Project Editor of the ISO/ANSI standards committee for C++, has authored over 150 papers on C++, and is listed as inventor on four patents. The first book he authored, in 1987, C Traps and Pitfalls, had been motivated by his prior paper and work on a different computer language, PL/I. In 1977, while a staff member working at Columbia University, Koenig presented a paper called “PL/I Traps and Pitfalls” at a SHARE meeting in Washington, DC. Koenig has a BS and MS degree from Columbia University in New York. He was a prominent member of the Columbia University Center for Computing Activities. He wrote the first e-mail program used at the university.

 

Andrew Koenig’s Overview                            

                                                                                

Past

• Founding member at C++ Standards Committee
• Principal Technical Staff Member at AT&T Shannon Laboratory
• Member of Technical Staff at Bell Labs

Education

• Columbia University School of Engineering and Applied Science
• Columbia College

Andrew Koenig’s Summary

Author or coauthor of three books and more than 160 technical articles. Founding member of C++ standards committee. More than 35 years’ software experience.

Specialties

Programming languages and tools, particularly C++ and Python.

Andrew Koenig’s Experience

Founding member

C++ Standards Committee

1990 – 2003 (13 years)

Principal Technical Staff Member

AT &T Shannon Laboratory

Public Company; 10,001+ employees; T; Telecommunications industry

July 1977 – June 2003 (26 years)

Member of Technical Staff

Bell Labs

Public Company; 10,001+ employees; T; Telecommunications industry

1977 – 1996 (19 years)

Technical Staff Member

Columbia University Center For  Computing Activities

Educational Institution; 10,001+ employees; Higher Education industry

September 1968 – June 1977 (8 years 10 months)

Andrew Koenig’s Education

• Columbia University School of Engineering and Applied Science

             MS, Computer Science

             January 1977

• Columbia College

           BA, Mathematics

         

                             

                                                            

DAVID A.HUFFMAN-BY MEENU P RAJMOHAN

David  A.Huffman

  

David Albert Huffman (August 9, 1925 – October 7, 1999) was a pioneer in the computer science field.

Throughout his life, Huffman made significant contributions to the study of finite state machines, switching circuits, synthesis procedures, and signal designs. However, David Huffman is best known for the invention of Huffman code, a highly important compression scheme for lossless variable length encoding. It was the result of a term paper he wrote while a graduate student at the Massachusetts Institute of Technology (MIT), where he earned a D.Sc. degree on a thesis named The Synthesis of Sequential Switching Circuits, advised by Samuel H. Caldwell (1953).                   

                                                                                        “Huffman Codes” are used in nearly every application that involves the compression and transmission of digital data, such as fax machines, modems, computer networks, and high-definition television (HDTV), to name a few.

                                           

A native of Ohio, Huffman earned his B.S. in electrical engineering from Ohio State University at the age of 18 in 1944. He then served in the U.S. Navy as a radar maintenance officer on a destroyer that helped to clear mines in Japanese and Chinese waters after World War II. He subsequently earned his M.S. degree from Ohio State in 1949 and his Ph.D. from MIT in 1953, also in electrical engineering.

Huffman joined the faculty at MIT in 1953. In 1967, he went to University of California, Santa Cruz as the founding faculty member of the Computer Science Department. He played a major role in the development of the department’s academic programs and the hiring of its faculty, and served as chair from 1970 to 1973. He retired in 1994, but remained active as an emeritus professor, teaching information theory and signal analysis courses.

Huffman made important contributions in many other areas, including information theory and coding, signal designs for radar and communications applications, and design procedures for asynchronous logical circuits. As an outgrowth of his work on the mathematical properties of “zero curvature Gaussian” surfaces, Huffman developed his own techniques for folding paper into unusual sculptured shapes (which gave rise to the field of computational origami).

                                                                                

 

Huffman’s accomplishments earned him numerous awards and honors. Most recently, he received the 1999 Richard Hamming Medal from the Institute of Electrical and Electronics Engineers (IEEE) in recognition of his exceptional contributions to information sciences. He also received the Louis E. Levy Medal of the Franklin Institute for his doctoral thesis on sequential switching circuits, a Distinguished Alumnus Award from Ohio State University, and the W. Wallace McDowell Award. He was a charter recipient of the Computer Pioneer Award from the IEEE Computer Society, and he received a Golden Jubilee Award for Technological Innovation from the IEEE Information Theory Society in 1998.

David Huffman died in 1999 after a 10-month battle with cancer.

Huffman never tried to patent an invention from his work. Instead, he concentrated his efforts on education. In Huffman’s words, “My products are my students.” 

                                              

ALAN TURING

ALAN TURING

                      

Alan Turing was born on 23 June, 1912, in London. His father was in the Indian Civil Service and Turing’s parents lived in India until his father’s retirement in 1926. Turing studied mathematics at Cambridge University, and subsequently taught there, working in the burgeoning world of quantum mechanics. It was at Cambridge that he developed the proof which states that automatic computation cannot solve all mathematical problems. This concept, also known as the Turing machine, is considered the basis for the modern theory of computation.

In 1936, Turing went to Princeton University in America, returning to England in 1938. He began to work secretly part-time for the British cryptanalytic department, the Government Code and Cypher School. On the outbreak of war he took up full-time work at its headquarters,Bletchley Park.                                                  

          

Here he played a vital role in deciphering the messages encrypted by the German Enigma machine, which provided vital intelligence for the Allies. He took the lead in a team that designed a machine known as a bombe that successfully decoded German messages. He became a well-known and rather eccentric figure at Bletchley.

After the war, Turing turned his thoughts to the development of a machine that would logically process information. He worked first for the National Physical Laboratory (1945-1948). His plans were dismissed by his colleagues and the lab lost out on being the first to design a digital computer. It is thought that Turing’s blueprint would have secured them the honour, as his machine was capable of computation speeds higher than the others. In 1949, he went to Manchester University where he directed the computing laboratory and developed a body of work that helped to form the basis for the field of artificial intelligence. In 1951 he was elected a fellow of the Royal Society.

Early life and career                                                           

The son of a British member of the Indian civil service, Turing entered King’s College, University of Cambridge, to study mathematics in 1931. After graduating in 1934, Turing was elected to a fellowship at King’s College in recognition of his research in probability theory. In 1936 Turing’s seminal paper “On Computable Numbers, with an Application to the Entscheidungsproblem [Decision Problem]” was recommended for publication by American mathematician-logician Alonzo Church,who had himself just published a paper that reached the same conclusion as  Turing’s.

Alanzo Church

In 1936 Turing and Church independently showed that in general this problem has no solution, proving that no consistent formal system of arithmetic is decidable. This result and others—notably the mathematician-logician Kurt Gödel’s incompleteness theorems—ended the dream of a system that could banish ignorance from mathematics forever. (In fact, Turing and Church showed that even some purely logical systems, considerably weaker than arithmetic, are undecidable.)

                                                                            Kurt Godel

An important argument of Turing’s and Church’s was that the class of lambda-definable functions (functions on the positive integers whose values can be calculated by a process of repeated substitution) coincides with the class of all functions that are effectively calculable—or computable. This claim is now known as Church’s thesis—or as the Church-Turing thesis when stated in the form that any effectively calculable function can be calculated by a universal Turing machine, a type of abstract computer that Turing had introduced in the course of his proof. (Turing showed in 1936 that the two formulations of the thesis are equivalent by proving that the lambda-definable functions and the functions that can be calculated by a universal Turing machine are identical.) In a review of Turing’s work, Church acknowledged the superiority of Turing’s formulation of the thesis over his own, saying that the concept of computability by a Turing machine “has the advantage of making the identification with effectiveness…evident immediately.”

                                                                      

The machine can be described as a finite state control device (meaning that it has a finite number of states that control its operations), with a tape of unlimited length, divided into squares, upon which symbols may be written or stored. A sequence of actions can take place when a symbol is scanned by a read/write head and the machine is in a certain state. The sequence of actions is the “program.”

At any point in time, the finite state control will be in one state and the tape head will be scanning a single symbol, or square, on the tape. On the basis of this symbol and the current state, it will write a symbol on the square, or choose to leave the symbol alone, move the tape one square to the left or the right, and change to a “new” (possibly the same) state. All this constitutes a “move” of the basic machine.

The purpose of the machine was to provide a method for deciding mathematical questions. Turing had become interested in the foundations of logic, and one of the unsolved or open questions was the “decideability” problem.

Code breaker

In the summer of 1938 Turing returned from the United States to his fellowship at King’s College. At the outbreak of hostilities with Germany in September 1939, he joined the wartime headquarters of the Government Code and Cypher School at Bletchley Park, Buckinghamshire. The British government had just been given the details of efforts by the Poles, assisted by the French, to break the Enigma code, used by the German military for their radio communications. As early as 1932, a small team of Polish mathematician-cryptanalysts, led by Marian Rejewski, had succeeded in reconstructing the internal wiring of the type of Enigma machine used by the Germans, and by 1938 they had devised a code-breaking machine, code-named Bomba (the Polish word for a type of ice cream).. At the end of the war, Turing was made an officer of the Order of the British Empire for his code-breaking work.

              Enigma 

Computer designer

In 1945, the war being over, Turing was recruited to the National Physical Laboratory (NPL) in London to design and develop an electronic computer. His design for the Automatic Computing Engine (ACE) was the first relatively complete specification of an electronic stored-program general-purpose digital computer. Had Turing’s ACE been built as planned, it would have had considerably more memory than any of the other early computers, as well as being faster. However, his colleagues at NPL thought the engineering too difficult to attempt, and a much simpler machine was built, the Pilot Model ACE.

Automatic Computing Engine

ANDREW S TANENBAUM- BY MUFEEDA BASHEER(ROLL NO:23)

ANDREW S.TANENBAUM                                      

Andrew Stuart “Andy” Tanenbaum (sometimes referred to by the handle ast) (born March 16, 1944) is a professor of computer science at the Vrije Universiteit, Amsterdam in the Netherlands. He is best known as the author of MINIX, a free Unix-like operating system for teaching purposes, and for his computer science textbooks, regarded as standard texts in the field. He regards his teaching job as his most important work.Andrew Tanenbaum is best known for his work on computer architecture, operating systems, and networks.

Andrew Stuart Tanenbaum was born in New York  and grew up in White Plains, New York, where he attended the local high school. His undergraduate degree was obtained at the Massachusetts Institute of Technology (MIT) in 1965 and his Ph.D. came from the University of California at Berkeley in 1971. Both degrees were in computer science. During his undergraduate period Tanenbaum spent a summer working at IBM, and this experience put him off working in industry for the rest of his life. For his postdoctoral studies Tanenbaum went to Amsterdam, where he has remained ever since. His postdoctoral studies were carried out jointly at Mathematisch Centrum and Vrije Universiteit between 1971 and 1973. In 1973 he took a permanent position at Vrije Universiteit where he rose to the position of professor of computer.He moved to the Netherlands to live with his wife, who is Dutch, but he retains his United States citizenship. He teaches courses about Computer Organization and Operating Systems and supervises the work of Ph.D. candidates at the VU University Amsterdam.

Prof. Tanenbaum is the principal designer of three operating systems: Amoeba, MINIX, and Globe. Amoeba is a distributed operating systems for SUN, VAX, and similar workstation computers. MINIX is a small operating system designed for high reliability and embedded applications as well as for teaching. Globe is a distributed operating system.

The Netherlands, where he heads the Computer Systems Group. He is also Dean of the Advanced School for Computing and Imaging, an interuniversity graduate school doing research on advanced parallel, distributed, and imaging systems. Nevertheless, he is trying very hard to avoid turning into a bureaucrat.
In the past, he has done research on compilers, operating systems, networking, and local-area distributed systems. His current research focuses primarily on the design of wide-area distributed systems that scale to a billion users. These research projects have led to five books and over 85 refereed papers in journals and conference proceedings.
He has also produced a considerable volume of software. He was the principal architect of the Amsterdam Compiler Kit, a widely-used toolkit for writing portable compilers, as well as of MINIX, a small UNIX clone intended for use in student programming labs. Together with his Ph.D. students and programmers, he helped design the Amoeba distributed operating system, a high-performance microkernel-based distributed operating system. The MINIX and Amoeba systems are now available for free via the Internet.
He is a Fellow of the ACM, a Fellow of the IEEE, a member of the Royal Netherlands Academy of Arts and Sciences, winner of the 1994 ACM Karl V. Karlstrom Outstanding Educator Award, and winner of the 1997 ACM/SIGCSE Award for Outstanding Contributions to Computer Science Education. In 2006 he was awarded the IEEE James H. Mulligan, Jr. medal for outstanding contributions to computer education. He is also listed in Who’s Who in the World. His home page on the World Wide Web can be found at http://www.cs.vu.nl/~ast/.

He is well recognized for his texts on computer science, which are famous as standard texts in the field, particularly:
Computer Networks, ISBN 0-13-066102-3
Operating Systems: Design and Implementation, (co-authored with Albert Woodhull), ISBN 0-13-142938-8
Modern Operating Systems, ISBN 0-13-031358-0
Distributed Operating Systems, ISBN 0-13-219908-4
Structured Computer Organization, ISBN 0-13-148521-0
Distributed Systems: Principles and Paradigms, (co-authored with Maarten van Steen), ISBN 0-13-239227-5

In addition, Tanenbaum is the author or coauthor of five books:

“Distributed Systems” (with Maarten van Steen)
“Modern Operating Systems”
  “Structured Computer Organization”
 “Operating Systems: Design and Implementation” (with Albert S. Woodhull)
 “Computer Networks”

                                         

                                

These books have been translated into 20 languages and are used all over the world. Tanenbaum has also published more than 125 refereed papers on a variety of subjects and has lectured in a dozen countries on many topics.

    Minix was the inspiration for the Linux kernel.Tanenbaum became involved in a famous Usenet discussion in 1992 with Linus Torvalds, Linux’s creator, about the merits of Linux’s basic approach using a monolithic kernel instead of the microkernel-based designs that Tanenbaum believed were the way of the future.

BLIND USER COMPUTING-done by MUFEEDA BASHEER

BLIND USER COMPUTING

   Earlier, the blind people  were unaware of most of the technological development.For them, the world of personal computers, office automation and the Internet offers mixed blessings.That world wasn’t designed for them,but now,as the technology growth is at its hike,with the right assistive technology, they can take part in it. When everything works well, they have access to an ocean of information vastly greater than anything previously available to the blind.

Blind computer users mainly rely upon screen-reader software, which describes the activity on the screen and reads the text in the various windows.Screen readers cost between US$500 and $1,000, although there are also freeware screen readers.(Windows XP and Vista come with a screen reader called Narrator, but even Microsoft says it’s not powerful enough for serious use.)

The screen reader’s output can be sent to the computer’s speakers as a synthesized voice or to a Braille display. The latter uses tiny push pins to create a pattern of raised dots that can be read by a moving finger. A unit with an 80-character line (enough for one full line of text) , and most blind people use a 40-character unit.

Braille displays are better than speech for editing because individual characters can be isolated and they are a necessity for the deaf-blind. It also lets them silently read e-mail while talking to someone else.

Although major operating systems usually have built-in screen readers for accessibility by the blind, they are rudimentary at best.But knowing what the screen is saying is just the beginning — the blind user then has to issue commands using keyboard shortcuts, because the mouse cursor is useless. Using shortcuts involves a lot of memorization, but at least the option is always available — or at least it used to be.

“Starting with Version 3.1, Microsoft tried to make sure there was a keystroke to do everything in Windows,” noted Dave Porter, an accessibility consultant and head of Comp-Unique. “It’s not so much that the keyboard shortcuts are different but that the user interface has changed,” said Rob Sinclair, director of accessibility at Microsoft.We have gotten away from a lot of menus and created a more simplified experience.

There are some amazingly powerful features in Vista for those with disabilities, like a Start function that begins with a search field.We can type in the name of an application, or a command, or search for a keyword in a document or an e-mail & can launch any application with a few keystrokes, easier than using menus.

Speaking of user applications, compatibility with a screen reader can be a crap shoot, and some commercial software packages include custom controls that screen readers can’t recognize.

In the days of DOS, there was a fixed number of characters across the screen, so identifying the information in the different parts of the screen was relatively simple.Finding the boundaries of the information is harder now, since there is no native indicator as to what is inside each window when we scrape the screen.
Beyond packaged software lies the world of in-house applications, where things can really go haywire for the blind user.The screen readers don’t work with in-house applications — it’s too easy to break the interface.It can be as simple as an application that puts up a lot of windows on the screen which are not windows from the viewpoint of the operating system. The screen reader will see one huge blob of information and read across the window boundaries.This can cause problems for job applicants, for example.

Of course, these days, many computers are used principally to access the Internet — and there is no telling what a blind person will encounter there.

“It can take a while to wade through a strange site — it can be maddening,” complained Jay Leventhal, who is blind and serves as editor of AccessWorld Magazine, produced by the American Foundation for the Blind. “Sometimes you find what you want to buy, but then you can’t find the submit button. It seems to literally not be there. A skilled [blind] user can navigate a majority of the sites on the Web these days, but you have to master certain tricks, like jumping from header to header in order to skip over a lot of junk, and use the search function to get the information you want. An average user can struggle for a long time looking for something and will even struggle on a familiar site.”

Blind man carrying mobile guide & PDA

A major sin among Web sites is a failure to use the HTML ALT attribute, which can be used to attach a descriptive label to a nontext item. If an image, for example, has an ALT label, the screen reader will read it. Otherwise it is forced to read the file name, which often amounts to useless gibberish.

There are accepted guidelines for designing accessible Web sites, especially the guidelines derived from Section 508 of the US Rehabilitation Act of 1973, as amended. Cyndi Rowland, director of WebAIM, an accessibility organization at Utah State University, noted that the guidelines are mandatory for federal Web sites and for organizations doing business with the US government. A number of states have also adopted the guidelines.

Her organization has a checklist of 16 requirements derived from Section 508, including use of the ALT description for images and image-map hot spots. Among other things, they state that frames should be given descriptive titles and that data tables should have row and column headers. There is a separate list of 12 requirements for applets.

Chong said the basic problem was a “next” button that was coded in such a way that it was invisible to screen readers, leaving blind users stranded. The problem has been fixed, but the lawsuit continues because Target hasn’t committed to accessibility, Chong said.But what literally frightens blind users is the rise of so-called CAPTCHA technology for Web site security. (CAPTCHA stands for Completely Automated Public Turing Test.”) To deny access to bots, the user must input a password that is displayed in a moderately distorted image that a machine can’t read. Of course, the screen readers can’t read it either.Some sites have an optional button to play an audio file that reads the password. However, this still leaves out the deaf-blind.

Made iphone for  blindusers

Beyond computers, sources complained of cell phones so complicated that they, too, need expensive screen readers. Many have small, flat buttons that are useless to the blind, culminating in the iPhone with no buttons. The iPod and its imitators don’t have buttons either, and even kitchen appliances today often have digital readouts that are useless to the blind.But Rowland noted that such considerations need to be weighed against the vast increase in electronic information during the past several years, at least part of which is accessible  to the blind.

With the advanced technology,people who kept a distance with everything due to their disabilities(blind,deaf) are able to experience the world in a different manner.We can say that the  new computing techniques is a boon to them.Eventhough they can access the electronic gadgets & other things with the current technology,they cannot enjoy everything as we normal  people can do.That is, it is something better than nothing.Lets us hope that the technology will give these differently abled people many more aids in the coming future.

PUPPY LINUX-done by MEENU P RAJMOHAN

PUPPY  LINUX                                                             

Puppy Linux is a variant of the Linux operating system designed to be small, portable, and easy to use. It was created in June 2003 by Barry Kauler, with the name based on his Chihuahua named Puppy.

Below are some examples of the features included with Puppy Linux.

• Small – Can be run from a USB drive, CD, SD Card, and other types of media.
• Can run entirely in RAM.
• GUI with window management.
• Can be run on old systems lacking a hard drive by running from external media.
• Can be used to remove malware by running from external media.
• Boot time is less than a minute in most cases.

MORE ABOUT PUPPY LINUX                                    

**********************************************                                        .

Linux is a free operating system, and Puppy Linux is a special build of Linux meant to make computing easy and fast.

Puppy Linux enables you to save money while doing more work, even allowing you to do magic by recovering data from destroyed PCs or by removing malware from Windows.

With Puppy Linux, you can carry your programs and data anywhere.

• Easy – Just use a CD or USB flash to boot a PC. Puppy Linux is downloadable as ISO, an image that can be burned to CD or DVD.
• Fast – Because Puppy is small, it can live in your PC’s memory and be ready to quickly execute your commands, whereas in other systems, programs are first read from drive storage before being executed.
• Save Money – Even if your PC has no hard disk (ex, broken hard disk), you can still boot Puppy via CD or USB and continue working. Old PCs that no longer work with new systems will still work good-as-new with Puppy.
• Do More – Puppy boots in less than a minute, even in old PCs, and it does not require antivirus software. Administering Puppy is quick and minimal. With Puppy, you just have to take care of your data, which you can easily save to USB flash (Then forget about your operating system!). Your data can be read by other computers.
• Do Magic -Help your friends suffering from computer malware by booting Puppy and removing malware from their PC (use antivirus that is built-in or can be installed in Puppy). Example – bad Autorun.inf is easily removed by Puppy (Just delete it as well as its companion exe program). If your friend thinks that she has lost data from her corrupted hard disk, boot Puppy and try saving her data!
• Carry Anywhere (Portable) – Because Puppy is able to live in CD/DVD or USB flash, as well as save data to these same devices, you can carry your programs and data with you.

 

*What is Puppy Linux?                                    

Puppy Linux is an operating system for computers. Other well-known operating systems are Microsoft Windows, Apple OSX, and MS-DOS. Puppy Linux is based on GNU/Linux. It is completely free and open source software.

*How is Puppy Different?     

                                                                              

• Small size, ~100MB! This lends itself to some very useful and unique features.
• ‘Live’ booting from CDs, DVDs, USB flash drives, and other portable media.
• Runs from RAM, making it unusually fast even in old PCs and in netbooks with solid state storage media.
• Very low minimum system requirements.
• Boot time is well under a minute, 30-40 seconds in most systems.
• Includes a wide range of applications: wordprocessors, spreadsheets, internet browsers, games, image editors and many utilities. Extra software in the form of dotpets. There is a GUI Puppy Software Installer included.
• Puppy is easy to use and little technical knowledge is assumed. Most hardware is automatically detect

Puppy’s Goals 

******************

     
                                                              

                                                                                 

• Puppy will easily install to USB, Zip, hard drive or other storage media.
• Booting from CD (or DVD), Puppy can load itself totally into RAM so that the CD (DVD) drive is then free for other purposes.
• Booting from DVD (or CD), Puppy can save all work to the DVD (CD). 
• Booting from USB flash drive (or other flash media), Puppy will minimize writes to extend its life.
• Puppy will be extremely friendly for Linux newbies.
• Puppy will boot up and run extraordinarily fast.
• Puppy will have all the applications needed for daily use.
• Puppy will just work, no hassles.
• Puppy will breathe new life into old PCs.
• Puppy will load and run totally in RAM for diskless thin stations.

*Who owns Puppy?

We all do. Puppy is covered by the GPL/LGPL license.

 

* Creator of  PUPPY LINUX  and how does he control the project?

Puppy Linux was first released in June 2003 by Barry Kauler.

The community that later developed is completely open, without any formal agenda or structure. It often takes newcomers a while to realize that, other than being friendly, there aren’t really any rules to Puppy. If you want to do something, make a new Puplet, offer your skills or take things in a new direction, just do so and be surprised that support will be around. However, questions will be asked so be ready to defend your ideas. Refer to what Barry Kauler has written about how the project is run.

Where does the name come from?

Puppy as immortalized in Barry Kauler’s avatar  

“The real Puppy, the mascot for Puppy Linux, was a very tiny dog, a Chihuahua, but totally fearless. He didn’t seem to know that he was vulnerable because of his small size. Once when my sister was visiting my country property, she brought her Blue Heeler, a very solid middle-sized dog named Muti. We were out walking, and suddenly there was a substantial rustling of branches of a large bush, something was in or behind the bush. Muti took fright and ran back behind the legs of my sister, whereas Puppy got into launch position in front of the bush and barked furiously. It turned out to be my dad playing a trick on the dogs. Puppy used to chase kangaroos and other big wild animals. Anyway, Puppy Linux is like that, reckless, unshackled, in memory of the mascot.” – Barry Kauler

3D-PRINTING

3D PRINTING

                                                 

Additive manufacturing or 3D printing is a process of making three dimensional solid objects from a digital model. 3D printing is achieved using additive processes, where an object is created by laying down successive layers of material. 3D printing is considered distinct from traditional machining techniques (subtractive processes) which mostly rely on the removal of material by drilling, cutting etc.

3D Printing is an SFF Process which creates parts in layers.Each layer is formed by spreading powder and selectively Joining the powder by ink-jet printing of a binder material.

What is a 3D Printing Process?

Three Dimensional Printing is a process under development at MIT for the rapid and flexible production of prototype parts, end-use parts, and tools directly from a CAD model. Three Dimensional Printing has unprecedented flexibility. It can create parts of any geometry, and out of any material, including ceramics, metals, polymers and composites. Furthermore, it can exercise local control over the material composition, microstructure, and surface texture.

Process

Three Dimensional Printing functions by building parts in layers. From a computer (CAD) model of the desired part, a slicing algorithm draws detailed information for every layer. Each layer begins with a thin distribution of powder spread over the surface of a powder bed. Using a technology similar to ink-jet printing, a binder material selectively joins particles where the object is to be formed. A piston that supports the powder bed and the part-in-progress lowers so that the next powder layer can be spread and selectively joined. This layer-by-layer process repeats until the part is completed. Following a heat treatment, unbound powder is removed, leaving the fabricated part. The sequence of operations is depicted below.

Process Capabilities

The 3DP^TM process combines powders and binders with unprecedented geometric flexibility. The support gained from the powder bed means that overhangs, undercuts and internal volumes can be created (as long as there is a hole for the loose powder to escape). 3D Printing can form any material that can be obtained as a powder – which is just about any material. Further, because different materials can be dispensed by different print heads, 3D Printing can exercise control over local material composition. Material can be in a liquid carrier, or it can be applied as molten matter. The proper placement of droplets can be used to create surfaces of controlled texture and to control the internal microstructure of the printed part.

The 3DP^TM process surpasses conventional powder processing because while the 3DP^TM components rival the performance of those made by conventional methods, there are no tooling or geometric limitations with Three Dimensional Printing. Because of its great flexibility in handling a wide range of materials and because of the unique ability to locally tailor the material composition, Three Dimensional Printing offers potential for the direct manufacture of structural components with unique microstructures and capabilities. Three Dimensional Printing is also readily scaled in production rate through the use of multiple nozzle technology which has been commercially developed for printing images on paper.

The Impact of Three Dimensional Printing

Three Dimensional Printing has led the field of Rapid Prototyping (RP) in the creation of functional parts and tooling directly from a CAD model. It was the first technology to achieve the fabrication of ceramic parts, and pioneered the direct fabrication of ceramic molds for casting. Three Dimensional Printing was a leader in the creation of metal parts directly and in the use of these parts for dies. Our work on ceramic preforms was the first demonstration of a functionally gradient material by RP. Most recently, we have pioneered the fabrication of structural ceramic parts using the 3DP^TM process.

MIT has licensed the 3DP^TM technology to six companies in diverse fields of use.

Three Dimensional Printing can substantially reduce the time to market for new products, enhance product quality by improving the coupling between design and manufacturing, and lower product cost by reducing development and tooling costs.

Furthermore, the flexibility of the process makes totally new technologies and applications possible and has already generated novel solutions to engineering problems. 3D Printing is at the forefront of the coming revolution in manufacturing brought about by Rapid Prototyping

3D printing is usually performed by a materials printer using digital technology. Since the start of the twenty-first century there has been a large growth in the sales of these machines, and their price dropped substantially.

The technology is used in the fields of jewellery, footwear, industrial design, architecture, engineering and construction (AEC), automotive, aerospace, dental and medical industries, education, geographic information systems, civil engineering, and many others.

Additive manufacturing (AM) also known as 3D printing is defined by ASTM as the “process of joining…

Applications:

Ceramic Shells for Direct Casting of Metal Parts

Three Dimensional Printing is the only process that fabricates ceramic molds directly from a computer model with no intervening steps. With 3D Printing, a ceramic shell with integral cores may be fabricated directly from a computer model. This results in a tremendous streamlining of the casting process as compared to the traditional lost-wax casting process (see figure below). Soligen, Inc. has licensed the 3DP^TM technology for producing shells, and has helped companies achieve dramatic reductions in turnaround times for metal castings.

Typically, molds by 3D Printing are fabricated using a refractory powder such as alumina and an inorganic binder material such as colloidal silica. After firing, the loose powder is removed from within the shell resulting in a shell which is similar in composition and properties to those now made in the lost wax process by dipping wax forms in ceramic slurries. However, no part specific tooling is needed 3D Printing has produced metal castings for a wide range of applications including aerospace, medical implants, automotive.

·      Direct Metal Tools

Metal parts for injection molding tooling inserts and for direct use have been built using the 3DPprocess and placed into use. ExtrudeHone Corporation has licensed the 3DP technology for the fabrication of metal parts and tools.

Parts have been created in a range of materials including stainless steel,

tungsten and tungsten carbide. Printed parts are sintered for strength, then they may be infiltrated with low melting point alloys to produce fully dense parts. The 3DP^TM process is easily adaptable to a variety of materials systems, allowing the production of metallic/ceramic parts with novel compositions.

The possibilities of this process include:

·         Direct production of injection molding tooling

·         Direct production of metal prototypes and end-use parts

·         Improved rate and dimensional control for injection-molded parts

3D Printing can be used to create tooling with integral cooling passages which are conformable to the molding cavity and near to its surface. Such channels can be printed in virtually any geometry and with virtually any interconnectedness. Tools with cooling passages can be used to control the temperature accurately and yield reproducible parts with predictable properties. Fast thermal response tooling can be created by printing passages for liquids near the surface and then providing a low thermal mass back-up structure, possibly by printing a truss structure (shown below). Textures may be printed onto the cooling channels themselves to further enhance heat transfer.

                                 

A cooling passage printed conformable to the Cooling cavity.

                                                               

Fast thermal response tooling with conformal cooling passages with a cellular/truss structure behind it for thermal isolation.

With such tooling, the temperature of the tool can be raised before injection and then quickly dropped after injection. This results in demonstrated and significant improvements in part quality (by reduced residual stress) and increased production rate.

·      Composite and Functionally Gradient Parts

1.     Functionally Gradient parts with Local Composition Control

A unique capability of the 3D Printing process is the ability to locally tailor the material composition of a part. This is made possible by precise control of a multiple-material printhead (see figure below). An appropriate data structure is all that is required to generate parts with multiple materials. This allows the part designer to locally tailor properties such as strength, toughness, or heat transfer, for example. Any material gradient can be imposed over any region, and locally, half-toning algorithms can be applied.

2.     Macroscopically Toughened Composite (MTC) Parts

It has been shown that silicon carbide reinforced aluminum alloys can display higher Charpy impact values if the SiC particulates are clustered into well organized arrays of “macro fibers” as compared to uniformly dispersed particulate reinforced composites. This concept has been demonstrated with 3-D printed preforms at MIT. Since these pseudo fibers can be printed into any array and can be infiltrated by techniques developed at MIT, a more flexible and low cost approach to the manufacture of MTC components is now possible.

The part shown to the left was produced as follows. Here, the pseudo-fibers are supported by densely printed end blocks. The printed preform is removed from the powder bed after heating to set the binder. It is then inserted into a die and pressure-infiltrated with molten metal. After removal from the die, a net-shaped component is produced with little need for additional machining. The concept of macroscopically toughened composites has many possibilities:

·        enhanced material properties including:

·        toughness

·        wear

·        thermal or electrical conductivity

·        thermal expansivity

·        ability to locally vary toughness or wear properties

·      Medical Applications: Drug Delivery Devices

MIT has issued Therics, Inc. a license for the production of time-release drug-delivery devices. Using a multiple jet printhead, extremely accurate quantities of several drugs can be printed into a bio-compatible, water-soluble substrate designed to time-release these drugs into the bloodstream.

3D Printing, now used primarily as a tool for processing metal and ceramic prototypes, has many advantages over other rapid prototyping technologies. It is capable of specific spatial deposition of multiple materials with fine resolution and control over local composition and microstructure. It is particularly worthy for fabricating functionally graded structures.

These aspects of the 3DP^TM process offer new possibilities for the fabrication of drug delivery systems. The ability to spatially control the deposition of multiple drugs, the level of porosity, and the strategic positioning of matrix modifiers will be important in designing the next generation of chronopharmacological drug delivery systems. 3D Printing has the ability to fabricate oral dosage forms for sustained release, controlled release, targeted release, cyclical release, or any combination of these. More precise spatial and temporal placement of drug into the body will reduce the size and number of doses, and this will thereby increase the therapeutic efficiency and safety of drugs, and help assist patient compliance.

        

3D printed model / 3D printed model

Objet Bio-Compatible material (MED610™) is a rigid material featuring great dimensional stability and colorless transparency. The material is ideal for applications requiring prolonged skin contact of over 30 days and short term mucosal-membrane contact of up to 24 hours

Much of the current research still concerns proving itself with the 3D Printing concept. Recent testing shows that 3D Printing is able to deliver precise drug dosage control, and cross-sample contamination was not detected. It has also been shown that samples with varying bulk densities and porosities can be fabricated, and that this in turn leads to great flexibility in the release kinetics. We are now engineering composite tablets which contain both regions of an erosion-type and a diffusion-type release mechanism. These composite devices are currently being designed for specific applications involving the delivery of antihistamine and anti-inflammatory medications.

·        Porous Ceramic Filters

Specific Surface, Inc. has licensed the 3DP^TM process for the production of porous ceramic filters with complex internal structures. The flexibility of 3DPTM allows the filter design to be tailored by a combination of geometry and particle size. This results in filter products with up to 10 times greater efficiency than conventional filters. One use of their products is in coal-burning power plants, which use the filters to remove particles from stack gases.

·      Experimental Geometries

1.Surface textures

Front-end CAD systems, combined with the geometric flexibility of 3D Printing have the potential for creating some dramatic new geometry. In the parts shown here, a surface texture was defined in CAD and then mapped onto different solids. Such surface textures can be used to enhance heat transfer or create a prescribed surface roughness, for example.

2. Truss structures

Truss structures of any complexity can be generated and printed by 3DPTM. This feature can be used for thermal isolation (injection molding), or to create a part with prescribed weaknesses (casting). In one application, a ceramic shell was designed with truss structures supporting and surrounding the shell wall. This shell was designed to fail as the poured metal cools, thus eliminating the problem of “hot tears.”

                                                                     

3DP part with fine surface feature mapped onto a                                                        Lattice structures by 3DP

geometric solid

TOUCHE :” TOUCHE AND GESTURE” -DISNEY RESEARCH-done by LAKSHMIPRIYA

A doorknob that knows to lock or unlock based on how it is grasped. A smartphone that silences itself if the user holds a finger to her lips. A chair that adjusts room lighting.

They are among the many possible applications of Touché, a new sensing technique developed by a team at Disney Research, Pittsburgh, and Carnegie Mellon University.

Touché is a new touch and gesture sensing technology that allows to make everyday objects, such as a common door knob, touch and gesture sensitive with just a single wire.

Touché can sense touch and hand postures on everyday objects, hand grasp on hand-held devices, human gestures directly on their bodies and with unusual materials such as water.

Touché is a form of capacitive touch sensing, the same principle underlying the types of touchscreens used in most smartphones. Touché is a new sensing technology that proposes a novel Swept Frequency Capacitive Sensing technique that can not only detect a touch event, but simultaneously recognize complex configurations of the human hands and body during touch interaction. This allows to significantly enhances touch interaction in a broad range of applications, from enhancing conventional touchscreens to designing interaction scenarios for unique use contexts and materials. For example, in our explorations we added complex touch and gesture sensitivity not only to computing devices and everyday objects, but also to the human body and liquids. Importantly, instrumenting objects and material with touch sensitivity is easy and straightforward: a single wire is sufficient to make objects and environments touch and gesture sensitive.

But instead of sensing electrical signals at a single frequency, like the typical touchscreen, Touché monitors capacitive signals across a broad range of frequencies.This Swept Frequency Capacitive Sensing (SFCS) makes it possible to not only detect a “touch event,” but to recognize complex configurations of the hand or body that is doing the touching. An object thus could sense how it is being touched, or might sense the body configuration of the person doing the touching.

SFCS is robust and can enhance everyday objects by using just a single sensing electrode. Sometimes, as in the case of a doorknob or other conductive objects, the object itself can serve as a sensor and no modifications are required.

Even the human body or a body of water can be a sensor.

Touché can recognize how the user touches his own body.

The basic principles of operation in most common capacitive sensing techniques are quite similar: A periodic electrical signal is injected into an electrode forming an oscillating electrical field. As the user’s hand approaches the electrode,a weak capacitive link is formed between the electrode and conductive physiological fluids inside the human hand, altering the signal supplied by the electrode. This happens because the user body introduces an additional path for flow of charges, acting as a charge “sink”. By measuring the degree of this signal change, touch events can be detected.

There is a wide variety of capacitive touch sensing techniques.One important design variable is the choice of signal property that is used to detect touch events, e.g., changes in signal phase or signal amplitude can be used for touch detection.

Touché can recognize hand gestures on liquids

 SWEPT FREQUENCY CAPACITIVE SENSING

 

 

Touché is measuring capacitive response of object and human at multiple frequencies, a technique that we called Swept Frequency Capacitive Sensing. The signal travels through different paths depending on it’s frequency, capturing the posture of human hand and body as well as other properties of the context. The resulted data is classified using machine learning algorithms to identify gestures that are then used to trigger desired responses of the user interface.

The human body is conductive, e.g., the average internal Resistance of a human trunk is ~100 Ω.Skin, on the other hand, is highly resistive, ~1M Ω for dry undamaged skin.This would block any weak constant electrical(DC) signal applied to the body. Alternating current (AC) signal, however, passes through the skin, which forms a capacitive interface between the electrode and ionic physiologic fluids inside the body.The body forms a charge “sink” with the signal flowing though tissues and bones to ground, which is also connected to the body through a capacitive link.The resistive and capacitive properties of the human body oppose the applied AC signal. This opposition, or electrical impedance1, changes the phase and amplitude of the AC signal. Thus, by measuring changes in the applied AC signal we can 1) detect the presence of a human body and also 2) learn about the internal composition of the body itself. This phenomenon, in its many variations, has been used since the 1960s in medical practice to measure the fluid composition of the human body,in electro-impedance tomography imaging and even to detect the ripeness of nectarine fruits.More recently, it has been used in a broad variety of capacitive touch buttons, sliders and touchscreens in human-computer interaction.The amount of signal change depends on a variety of factors.It is affected by how a person touches the electrode, e.g., the surface area of skin touching the electrode. It is affected by the body’s connection to ground, e.g., wearing or not wearing shoes or having one or both feet on the ground. Finally, it strongly depends on signal frequency.This is because at different frequencies, the AC signal will flow through different paths inside of the body. Indeed, just as DC signal flows through the path of least resistance, the AC signal will always flow through the path of least impedance. The human body is anatomically complex and different tissues, e.g., muscle, fat and bones, have different resistive and capacitive properties. As the frequency of the AC signal changes, some of the tissues become more opposed to the flow of charges, while others less, thus changing the path of the signal flow (see for an overview of the bioelectrical aspects of human body impedance).Therefore, by sweeping through a range of frequencies in capacitive sensing applications, we obtain a wealth of information about 1) how the user is touching the object, 2) how the user is connected to the ground and 3) the current configuration of the human body and individual body properties.

TOUCHÉ IMPLEMENTATION

The user interacts with an object that is attached to a Touché sensor board via a single wire. If the object itself is conductive, the wire can be attached directly to it. Otherwise, a single electrode has to be embedded into the object and the wire attached to this electrode. Touché implements SFCS on a compact custom-built board powered by an ARM Cortex-M3 microprocessor. The on-board signal generator excites an electrode with sinusoid sweeps and measures returned signal at each frequency.The resulting sampled signal is a capacitive profile of the touch interaction. Finally, the capacitive profile is sent to a conventional computer over Bluetooth for classification. Recognized gestures can then be used to trigger different interactive functions.While it is possible to implement classification directly on the sensor board, a conventional computer provided more flexibility in fine-tuning and allowed for rapid prototyping.

EXAMPLE TOUCHÉ APPLICATIONS

The application space of Touché is broad, therefore at least some categorization is pertinent to guide the development of the interfaces based on this technology. We identified five application areas where we felt that Touché could have the largest impact – either as a useful enhancement to an established application or a novel application, uniquely enabled by our approach:

• • making everyday objects touch gesture sensitive
• • sensing human bimanual hand gestures
• • sensing human body configuration (e.g., pose)
• • enhancing traditional touch interfaces
• • sensing interaction with unusual materials (e.g., liquids)

Making objects touch and grasp sensitive

If analogue or digital objects can be made aware of how they are being touched, held or manipulated, they could configure themselves in meaningful and productive ways The canonical example is a mobile phone which, when held like a phone, operates as a phone.However, when held like a camera, the mode could switch to picture-taking automatically. Touché offers a lightweight, non-invasive sensing approach that makes it very easy to add touch and gesture sensitivity to everyday objects. Doorknobs provide an illustrative exa to operate. Yet, in general, doorknobs have not been infused with computational abilities. A smart doorknob that can sense how a user is touching it could have many useful features. For example, closing a door with a tight grasp could lock it, while closing it with a pinch might set a user’s away message, e.g., “back in five minutes”. A sequence of grasps

could constitute a “grasp password” that would allow an authorized user to unlock the door

Body Configuration Sensing

Touché can be used to sense the configuration of the entire human body. For example, a door could sense if a person is simply standing next to it, if they have raised their arm to knock on it, are pushing the door, or are leaning against it.Alternatively, a chair or a table could sense the posture of a

seated person – reclined or leaning forward, arms on the armrests or not, one or two arms operating on the surface, as well as their configuration .More importantly, this can occur without instrumenting the user. Similar to

everyday objects, conductive tables can be used as is, just by connecting a Touché sensor. Non-conductive tables would require a single flat electrode added to their surface or could simply be painted with conductive paint.

Enhancing Touchscreen Interaction

Touché brings new and rich interaction dimensions to conventional touch surfaces by enhancing touch with sensed hand posture. For example, Touché could sense the configuration of fingers holding a device, e.g., if they are closed into a fist or held open, whether a single finger is touching, all five fingers, or the entire palm. The part of the hand touching could be also possibly be inferred,e.g., fingertips or knuckles, a valuable extra dimension