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Short Wavelength, Ultra-High Speed Quantum Light Source based on Quantum Dot Developed
Professor Yong Hoon, Cho (Department of Physics) and his research team synthesized an obelisk nanostructure and successfully formed a single semiconductor quantum exhibiting high reliability to realize an ultra-high speed, highly efficient, release of quantum dots.
The result of the research effort was published in the July 5th online edition of Scientific Reports published by Nature.
Semiconductor Quantum Dots restrict electrons within a cubic boundary of few nanometers thereby exhibiting similar properties to an atom with discontinuous energy levels. Exploitation of this characteristic makes possible the development of quantum light source, critical for next generation quantum information communication and quantum encryption.
High operational temperatures, stability, rapid photon release, electric current capability, and other advantages are reasons why semiconductor quantum dots are regarded as next generation core technology.
However conventional, spontaneously formed quantum dots are densely packed in a planar structure rendering the analysis of a single quantum dot difficult and result in the poor efficiency of photon release. In addition, the internal electromagnetic effect which is caused by inter-planar stress results in low internal quantum efficiency due to the difficulty in electron-hole recombination.
Professor Cho’s research team synthesized an obelisk shaped nanostructure using nitrides that emit short wavelengths of light. The activation layer was grown on the tip of the nanostructure and the team succeeded in placing a single quantum dot on the nano-tip. The team was therefore able to confirm the ultra-high speed single photon characteristics which occur at low energy levels.
Use of unique nanostructures makes synthesis of single atomic structures without processes like patterning while enabling the release of light emitted by the quantum dot.
Using this unique method the team showed the increase in internal quantum efficiency. The electromagnetic forces apparent in thin films no longer affects the quantum dot greatly due to the obelisk structure’s reduced inter planar stress.
The newly developed quantum light source emits visible light (400nm range) and not the conventional infrared light. This characteristic makes possible it use in communication in free space and enables use of highly efficient, visible range photon detector.
Professor Cho commented that “the developed method makes quantum dot growth much easier making single photon synthesis much faster to contribute to the development of practical quantum light source.” And that “the characteristics of the obelisk nanostructure enable the easy detachment from and attachment to other substrates enabling its use in producing single chip quantum light source.”
The research was conducted under the supervision of Professor Cho. The researchers werey Jae Hyung, Kim (first author) and Yong Ho, Ko (second author), both Ph.D. candidates at KAIST. The Ministry of Science, ICT and Future Planning, the National Research Foundation, and WCU Program provided support to the research effort.
2013.08.23 View 7962 -
Ultra-High Strength Metamaterial Developed Using Graphene
New metamaterial has been developed, exhibiting hundreds of times greater strength than pure metals.
Professor Seung Min, Han and Yoo Sung, Jeong (Graduate School of Energy, Environment, Water, and Sustainability (EEWS)) and Professor Seok Woo, Jeon (Department of Material Science and Engineering) have developed a composite nanomaterial. The nanomaterial consists of graphene inserted in copper and nickel and exhibits strengths 500 times and 180 times, respectively, greater than that of pure metals. The result of the research was published on the July 2nd online edition in Nature Communications journal.
Graphene displays strengths 200 times greater than that of steel, is stretchable, and is flexible. The U.S. Army Armaments Research, Development and Engineering Center developed a graphene-metal nanomaterial but failed to drastically improve the strength of the material.
To maximize the strength increased by the addition of graphene, the KAIST research team created a layered structure of metal and graphene. Using CVD (Chemical Vapor Deposition), the team grew a single layer of graphene on a metal deposited substrate and then deposited another metal layer. They repeated this process to produce a metal-graphene multilayer composite material, utilizing a single layer of graphene. Micro-compression tests within Transmission Electronic Microscope and Molecular Dynamics simulations effectively showed the strength enhancing effect and the dislocation movement in grain boundaries of graphene on an atomic level.
The mechanical characteristics of the graphene layer within the metal-graphene composite material successfully blocked the dislocations and cracks from external damage from traveling inwards. Therefore the composite material displayed strength beyond conventional metal-metal multilayer materials. The copper-graphene multilayer material with an interplanar distance of 70nm exhibited 500 times greater (1.5GPa) strength than pure copper. Nickel-graphene multilayer material with an interplanar distance of 100nm showed 180 times greater (4.0GPa) strength than pure nickel.
It was found that there is a clear relationship between the interplanar distance and the strength of the multilayer material. A smaller interplanar distance made the dislocation movement more difficult and therefore increased the strength of the material. Professor Han, who led the research, commented, “the result is astounding as 0.00004% in weight of graphene increased the strength of the materials by hundreds of times” and “improvements based on this success, especially mass production with roll-to-roll process or metal sintering process in the production of ultra-high strength, lightweight parts for automobile and spacecraft, may become possible.” In addition, Professor Han mentioned that “the new material can be applied to coating materials for nuclear reactor construction or other structural materials requiring high reliability.”
The research project received support from National Research Foundation, Global Frontier Program, KAIST EEWS-KINC Program and KISTI Supercomputer and was a collaborative effort with KISTI (Korea Institute of Science and Technology Information), KBSI (Korea Basic Science Institute), Stanford University, and Columbia University.
A schematic diagram shows the structure of metal-graphene multi-layers. The metal-graphene multi-layered composite materials, containing a single-layered graphene, block the dislocation movement of graphene layers, resulting in a greater strength in the materials.
2013.08.23 View 14259 -
KAIST unveils foldable micro electric car, Armadillo-T
The small and light electric car completely folds in half when parking, making it a perfect fit for public or private transportation in an urban environment.
Looking for a parking space for hours at a busy shopping mall or being stuck on roads jammed with cars releasing large amounts of carbon dioxide are all-too-familiar scenes for city dwellers.
A group of researchers at the Korea Advanced Institute of Science and Technology (KAIST) recently developed a possible solution to such problems: a foldable, compact electric vehicle that can be utilized either as a personal car or part of the public transit system to connect major transportation routes within a city.
In-Soo Suh, associate professor of the Graduate School for Green Transportation at KAIST, and his research team introduced a prototype micro electric car called "Armadillo-T," whose design is based on a native animal of South America, the armadillo, a placental mammal with a leathery armor shell.
The research team imitated the animal"s distinctive protection characteristic of rolling up into a ball when facing with threat from predators. Just as armadillos hide themselves inside the shell, Armadillo-T tucks its rear body away, shrinking its original size of 2.8 meters (110 inches) down to almost half, 1.65 meters (65 inches), when folding.
Armadillo-T is a four-wheel-drive, all-electric car with two seats and four in-wheel motors. Since the motors are installed inside the wheels, and the 13.6 kWh capacity of lithium-ion battery pack is housed on the front side, the battery and motors do not have to change their positions when the car folds. This not only optimizes the energy efficiency but also provides stability and ample room to drivers and passengers.
Once folded, the small and light (weighs 450 kg) electric vehicle takes up only one-third of a 5-meter parking space, the standard parking size in Korea, allowing three of its kind to be parked. With a smartphone-interfaced remote control on the wheels, the vehicle can turn 360 degrees, enhancing drivers" convenience to park the car, even in an odd space in a parking lot, the corner of a building, for example.
Professor In-Soo Suh said, "I expect that people living in cities will eventually shift their preferences from bulky, petro-engine cars to smaller and lighter electric cars. Armadillo-T can be one of the alternatives city drivers can opt for. Particularly, this car is ideal for urban travels, including car-sharing and transit transfer, to offer major transportation links in a city. In addition to the urban application, local near-distance travels such as tourist zones or large buildings can be another example of application."
The concept car has loads of smart features on board, too: the cameras installed inside the car eliminate the need for side mirrors and increase the driver"s ability to see the car"s right and left side, thereby reducing blind spots. With a smartphone, the driver can control Armadillo-T and enable remote folding control. The car has a maximum speed of 60 km/h, and with a ten-minute fast charge, it can run up to 100 km.
Professor Suh explained that the concept of Armadillo-T was originally initiated in 2011 as he focused his research interest on the sub-A segment of personal mobility vehicles (PMVs), which are smaller and lighter than the current compact cars, as a new personalized transport mode.
"In coming years, we will see more mega-size cities established and face more serious environmental problems. Throughout the world, the aging population is rapidly growing as well. To cope with climate, energy, and limited petroleum resources, we really need to think outside the box, once again, to find more convenient and eco-friendly transportation, just as the Ford Model T did in the early 1920s. A further level of R&D, technical standards, and regulatory reviews are required to have these types of micro vehicles or PMVs on the market through test-bed evaluations, but we believe that Armadillo-T is an icon toward the future transport system with technology innovation."
The research project has been supported by the Korean government, the Ministry of Land, Infrastructure and Transport and the Korea Agency for Infrastructure Technology Advancement, since December 2012.Youtube Link: http://www.youtube.com/watch?v=8DoZH7Y-sR0
2013.08.21 View 13957 -
Two Dimensions of Value: Dopamine Neurons Represent Reward but not Aversiveness
Professor Christopher D. Fiorillo of the Bio & Brain Engineering (http://ineuron.kaist.ac.kr/web/home.html) at KAIST published a research paper in the August 2 issue of Science. The title of the paper is “Two Dimensions of Value: Dopamine Neurons Represent Reward but not Aversiveness.” The following is an introduction of his research work:
To make decisions, we need to estimate the value of sensory stimuli and motor actions, their “goodness” and “badness.” We can imagine that good and bad are two ends of a single continuum, or dimension, of value. This would be analogous to the single dimension of light intensity, which ranges from dark on one end to bright light on the other, with many shades of gray in between. Past models of behavior and learning have been based on a single continuum of value, and it has been proposed that a particular group of neurons (brain cells) that use dopamine as a neurotransmitter (chemical messenger) represent the single dimension of value, signaling both good and bad.
The experiments reported here show that dopamine neurons are sensitive to the value of reward but not punishment (like the aversiveness of a bitter taste). This demonstrates that reward and aversiveness are represented as two discrete dimensions (or categories) in the brain. “Reward” refers to the category of good things (food, water, sex, money, etc.), and “punishment” to the category of bad things (stimuli associated with harm to the body and that cause pain or other unpleasant sensations or emotions).
Rather than having one neurotransmitter (dopamine) to represent a single dimension of value, the present results imply the existence of four neurotransmitters to represent two dimensions of value. Dopamine signals evidence for reward (“gains”) and some other neurotransmitter presumably signals evidence against reward (“losses”). Likewise, there should be a neurotransmitter for evidence of danger and another for evidence of safety. It is interesting that there are three other neurotransmitters that are analogous to dopamine in many respects (serotonin, norepinephrine, and acetylcholine), and it is possible that they could represent the other three value signals.
For the research article, please visit: http://www.sciencemag.org/content/341/6145/546.abstract
For the Science 2nd issue, please visit: http://www.sciencemag.org/content/current#ResearchArticles
Illustration of Value Dimension
2013.08.08 View 7490
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2013 International Conference for the Integration of Science, Technology, and Society at KAIST (ICISTS-KAIST)
The International Conference for the Integration of Science, Technology, and Society at KAIST (ICISTS-KAIST) is a global forum organized by KAIST undergraduate students to promote the exchange of ideas and facilitate the discussion of issues that are important to science, technology, society, and higher education. The ICISTS-KAIST conference has been held annually every summer since 2005, inviting distinguished speakers and guests from all around the world to share their insights and expertise with students gathered from Korea and abroad. Last year alone, more than 300 students from 22 nations and 40 speakers participated in the event.
Originally, the ICISTS-KAIST was established by KAIST students who were inspired by the Harvard Project for Asian and International Relations (HPAIR), which is one of the Harvard’s largest annual student conferences in Asia.
This year, 335 students from 103 universities in 22 countries joined the conference that was held on August 5th-9th in Daejeon, making the 2013 ICISTS-KAIST the biggest science and engineering gathering hosted by university students in Asia. About 36% of the participants were international students.
The theme of the conference was “Perfect Alliance: Coexistence for Human Society,” in which students and speakers addressed issues on how to harmonize the speed of scientific progress with the development of important values in society, as well as to explore solutions to overcome the chasm, if any, between the boundaries of science and society.
In his opening remarks, President Steve Kang said, “Creativity and innovation are born out of openness. Therefore, it is essential for young scientists and engineers to communicate with people from different cultural and political backgrounds. Through this kind of global interaction and exchange of ideas and views, students will have an opportunity to deepen their understanding of the world and to better examine the purpose of their intellectual exploration in science and technology.” At the 2013 ICISTS-KAIST, 25 distinguished speakers participated including Walter Bender, a former director of the Media Lab at MIT and David Christian, a professor of Macquarie University in Australia.
2013.08.08 View 9659 -
Chemistry World: Interview with Professor Cafer Yavuz of EEWS Graduate School
Professor Cafer Yavuz of the Graduate School of EEWS (energy, environment, water, and sustainability) at KAIST had an interview with the Chemistry World, the print and online magazine issued by the Royal Society of Chemistry, the largest organization in Europe for advancing the chemical sciences. The link below is the article published by the magazine:
http://www.rsc.org/chemistryworld/2013/08/interview-cafer-yavuz-carbon-dioxide-capture
2013.08.07 View 7553
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High Speed Nanomanufacturing Process Developed using Laser
Dr. Yeo Jun Yeop from KAIST’s Department of Mechanical Engineering, in a joint research project with Prof. Seung Hwan Ko, has developed a technology that speeds up the nanomanufacturing process by using lasers. Their research is published in the frontispiece of Advanced Functional Materials (July 9th issue).
Fig. The frontispiece of Advanced Functional Materials(July 9th issue)
The research group put a nanomaterial precursor on the board, illuminated it with a continuous-wave laser in the green wavelength range, and succeeded in synthesizing a nanowire at the point they wanted for the first time in the world.
Currently nanomaterials are difficult to mass produce and commercialize due to their complex and costly manufacturing processes which also use toxic gases. However, their new technology simplified the process and so reduced the manufacturing time from some hours to five minutes (1/10th times reduced).
Furthermore, this technology will apply regardless of the type of the board. Such nanometerials can be synthesized at any point on a flexible plastic board or even in three dimensional structures by illuminating them with a simple laser. Academics and industries expect mass production and commercialization of nanomaterials in near future.
Dr. Yeo said he intends to research further to promote early commercialization of multifunctional electronic devices by combining various nanomaterials
This research is sponsored by the National Research Foundation of Korea, the Ministry of Trade, Industry and Energy and KAIST EEWS
Fig. A nanomaterial synthesized after illuminated by lasers
Fig. A nanomaterial synthesized on a three dimensional structure using the developed technology
Fig. Functional electron device manufactured by using the synthesized nanomaterials
2013.08.02 View 8238 -
A magnetic pen for smartphones adds another level of conveniences
Utilizing existing features on smartphones, the MagPen provides users with a compatible and simple input tool regardless of the type of phones they are using.
A doctoral candidate at the Korea Advanced Institute of Science and Technology (KAIST) developed a magnetically driven pen interface that works both on and around mobile devices. This interface, called the MagPen, can be used for any type of smartphones and tablet computers so long as they have magnetometers embedded in.
Advised by Professor Kwang-yun Wohn of the Graduate School of Culture Technology (GSCT) at KAIST, Sungjae Hwang, a Ph.D. student, created the MagPen in collaboration with Myung-Wook Ahn, a master"s student at the GSCT of KAIST, and Andrea Bianchi, a professor at Sungkyunkwan University.
Almost all mobile devices today provide location-based services, and magnetometers are incorporated in the integrated circuits of smartphones or tablet PCs, functioning as compasses. Taking advantage of built-in magnetometers, Hwang"s team came up with a technology that enabled an input tool for mobile devices such as a capacitive stylus pen to interact more sensitively and effectively with the devices" touch screen. Text and command entered by a stylus pen are expressed better on the screen of mobile devices than those done by human fingers.
The MagPen utilizes magnetometers equipped with smartphones, thus there is no need to build an additional sensing panel for a touchscreen as well as circuits, communication modules, or batteries for the pen. With an application installed on smartphones, it senses and analyzes the magnetic field produced by a permanent magnet embedded in a standard capacitive stylus pen.
Sungjae Hwang said, "Our technology is eco-friendly and very affordable because we are able to improve the expressiveness of the stylus pen without requiring additional hardware beyond those already installed on the current mobile devices. The technology allows smartphone users to enjoy added convenience while no wastes generated."
The MagPen detects the direction at which a stylus pen is pointing; selects colors by dragging the pen across smartphone bezel; identifies pens with different magnetic properties; recognizes pen-spinning gestures; and estimates the finger pressure applied to the pen.
Notably, with its spinning motion, the MagPen expands the scope of input gestures recognized by a stylus pen beyond its existing vocabularies of gestures and techniques such as titling, hovering, and varying pressures. The tip of the pen switches from a pointer to an eraser and vice versa when spinning. Or, it can choose the thickness of the lines drawn on a screen by spinning.
"It"s quite remarkable to see that the MagPen can understand spinning motion. It"s like the pen changes its living environment from two dimensions to three dimensions. This is the most creative characteristic of our technology," added Sungjae Hwang.
Hwang"s initial research result was first presented at the International Conference on Intelligent User Interfaces organized by the Association for Computing Machinery and held on March 19-22 in Santa Monica, the US.
In the next month of August, the research team will present a paper on the MagPen technology, entitled "MagPen: Magnetically Driven Pen Interaction On and Around Conventional Smartphones" and receive an Honorable Mention Award at the 15th International Conference on Human-Computer Interaction with Mobile Devices and Services (MobileHCI 2013) to be held in Germany.
In addition to the MagPen, Hwang and his team are conducting other projects to develop different types of magnetic gadgets (collectively called "MagGetz") that include the Magnetic Marionette, a magnetic cover for a smartphone, which offers augmented interactions with the phone, as well as magnetic widgets such as buttons and toggle interface.
Hwang has filed ten patents for the MagGetz technology.
Youtube Links: http://www.youtube.com/watch?v=NkPo2las7wc, http://www.youtube.com/watch?v=J9GtgyzoZmM
2013.07.25 View 9921 -
Technology Developed to Control Light Scattering Using Holography
Published on May 29th Nature Scientific Reports online
Recently, a popular article demonstrated that an opaque glass becomes transparent as transparent tape is applied to the glass. The scientific principle is that light is less scattered as the rough surface of the opaque glass is filled by transparent tape, thereby making things behind the opaque glass look clearer.
Professor Yong-Keun Park from KAIST’s Department of Physics, in a joint research with MIT Spectroscopy Lab, has developed a technology to easily control light scattering using holography. Their results are published on Nature’s Scientific Reports May 29th online edition.
This technology allows us to see things behind visual obstructions such as cloud and smoke, or even human skin that is highly scattering, optically thick materials. The research team applied the holography technology that records both the direction and intensity of light, and controlled light scattering of obstacles lied between an observer and a target image. The team was able to retrieve the original image by recording the information of scattered light and reflecting the light precisely to the other side.This phenomenon is known as “phase conjugation” in physics. Professor Park’s team applied phase conjugation and digital holography to observe two-dimensional image behind a highly scattering wall. “This technology will be utilized in many fields of physics, optics, nanotechnology, medical science, and even military science,” said Professor Park. “This is different from what is commonly known as penetrating camera or invisible clothes.” He nevertheless drew the line at over-interpreting the technology, “Currently, the significance is on the development of the technology itself that allows us to accurately control the scattering of light."
Figure I. Observed Images
Figure II. Light Scattering Control
2013.07.19 View 7821 -
Joint Research Center on EEWS with Hyundai Heavy Industries Plans to Open
The research center will conduct collaborative R&D projects on energy, environment, water, and sustainability for the next five years.Hyundai Heavy Industries (HHI), the world’s largest shipbuilding company, signed an MOU with KAIST for future business development and joint research collaboration.
KAIST and HHI signed an MOU as an agreement to establish the “HHI-KAIST EEWS Research Center (HK Research Center) on June 21st.”
The major mission of the HK Research Center is to build a strong base for creating future businesses through developing fundamental, core technology in the field of EEWS and designing business models based on the new technology.
Toward this goal, HHI will sponsor the R&D budget and operation expenses of the research center for the next five years.
Prior to the signing of the MOU, a delegation from HHI, led by the Vice President, Mr. Si-Young Hwang, visited the Office of EEWS Initiative at KAIST and held a workshop. During the workshop, HHI and KAIST agreed to collaborate in fields such as LNG-propelled ships, solar power generation, energy storage, fuel cells, and CO2 capture.
KAIST has run a EEWS graduate program that receives government grants over the last five years, with a research emphasis on energy, environment, water, and sustainability, which are crucial issues to humankind in the 21st century. The EEWS program achieved 24 core technological developments and educates more than 200 masters- and PhD-degree students annually.
The EEWS program also emphasizes commercializing its research outcomes. Through the annual Business Planning Competition and Investment Drive, there have been eight new companies founded by alumni and professors over the last five years of the program. The HK Research Center will be an excellent foundation for future education and research in EEWS.
Professor Jae-Kyu Lee, the head of the HK Research Center and the director of the EEWS Initiative, said, “This event is a benchmarking example of Industry-KAIST collaboration. We hope that the HK Research Center will be a place for disruptive innovations to translate into creative business opportunities.”
MOU signed for Hyundai Heavy Industries-KAIST EEWS Research Center
2013.07.15 View 7870 -
Prof. Song Chong received the IEEE William R. Bennett Prize Paper Award
The IEEE (Institute of Electrical and Electronics Engineers) Communications Society (ComSoc), a renowned global network of professionals with a common interest in advancing communications technologies, has announced the winner of the 2013 William R. Bennett Prize in the field of communications networking. The prize was given to a Korean research team led by Song Chong, Professor of Electrical Engineering at KAIST and Injong Rhee, Professor of Computer Science at North Carolina State University. In addition, Dr. Minsu Shin, Dr. Seongik Hong, and Dr. Seong Joon Kim of Samsung Electronics Co., Ltd. as well as Professor Kyunghan Lee from Ulsan National Institute of Science and Technology were recognized for their contribution.
The William R. Bennett Prize for communications networking has been awarded each year since 1994 in recognition of the best paper published in any journal financially sponsored or co-sponsored by ComSoc in the previous three calendar years. Only one paper per year is selected based on its quality, originality, scientific citation index, and peer reviews. Among the previous award winners are Robert Gallager of MIT, and Steven Low of the California Institute of Technology, and Kang G. Shin of the University of Michigan.
The Korean research team’s paper, On the Levy-Walk Nature of Human Mobility, was published in the June 2011 issue of IEEE/ACM Transactions on Networking, a bimonthly journal co-sponsored by the IEEE ComSoc, the IEEE Computer Society, and the Association for Computing Machinery (ACM) with its Special Interest Group on Data Communications (SIGCOMM).
In the paper, the research team proposed a new statistical model to effectively analyze the pattern of individual human mobility in daily life. The team handed out GPS (global positioning system) devices to 100 participants residing in five different university campuses in Korea and the US and collected data on their movements for 226 days. The mobility pattern obtained from the experiment predicted accurately how the participants actually moved around during their routines. Since publication, the paper has been cited by other papers approximately 350 times.
The team’s research results will apply to many fields such as the prevention and control of epidemics, the design of efficient communications networks, and the development of urban and transportation system.
The research team received the award on June 10th at the 2013 IEEE International Conference on Communications (ICC) held in Budapest, Hungary, from June 9-13, 2013.
Professor Song Chong
2013.07.06 View 12119 -
Foreign graduates donate to development fund for six years
International graduates of the Global IT Technology Graduate School at KAIST have continued a tradition of giving something back to their alma mater.
On May 10th, President Steve Kang held a donation ceremony with 12 donors.
Started in 2008, the graduates, mostly consisted of government officials from developing countries, have raised a development fund for KAIST, and in the past six years, a total of 81 graduates donated USD 10,000.
“KAIST provided me with an excellent education and research environment during my studies. I’m glad that I can have an opportunity to help my juniors and the university,” said Naryn Kenzhaliyev of Kazakhstan, a graduate present at the ceremony.
“Every year, these students voluntarily give when they are about to graduate. We feel proud and greatly appreciated for their philanthropic efforts,” said Professor Jae-Jung Noh, responsible for the global IT technology graduate program.
Established in 2006, the Global IT Technology Graduate School has attracted IT specialists from Korea and abroad, offering master’s and doctoral degrees. The school has invited many public servants in developing countries whose expertise lies in IT technology.
2013.07.04 View 5958