College+of+Natural+Sciences
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Nanowire crystal transformation method was newly developed by a KAIST research team.
Figure 1
Schematic illustration of NW crystal transformation process. FeSi is converted to Fe3Si by high-temperature thermal annealing in diluted O2 condition and subsequent wet etching by 5% HF.
Figure 2
Low-resolution TEM images of FeSi; Fe3Si@SiO2 core—shell; Fe3Si NW after shell-etching; and Scale bars are 20 nm
Professor Bongsoo Kim of the Department of Chemistry, KAIST, and his research team succeeded to fabricate Heusler alloy Fe3Si nanowires by a diffusion-driven crystal structure transformation method from paramagnetic FeSi nanowires. This methodology is also applied to Co2Si nanowires in order to obtain metal-rich nanowires (Co) as another evidence of the structural transformation process. The newly developed nanowire crystal transformation method, Professor Kim said, would be valuable as a general method to fabricate metal-rich silicide nanowires that are otherwise difficult to synthesize.
Metal silicide nanowires are potentially useful in a wide array of fields including nao-optics, information technology, biosensors, and medicine. Chemical synthesis of these nanowires, however, is challenging due to the complex phase behavior of silicides.
The metal silicide nanowires are grown on a silicon substrate covered with a thin layer of silicon oxide via a simple chemical vapor deposition (CVD) process using single or multiple source precursors. Alternatively, the nanowires can be grown on the thin silicon oxide film via a chemical vapor transport (CVT) process using solid metal silicide precursors.
The CVT-based method has been highly effective for the syntheses of metal silicide NWs, but changing the composition of metal silicide NWs in a wider range, especially achieving a composition of a metal to silicon, has been quite difficult.
Thus, developing efficient and reliable synthetic methods to adjust flexibly the elemental compositions in metal silicide NWs can be valuable for the fabrication of practical spintronic and neonelectronic devices.
Professor Kim expliained, “The key concept underlying this work is metal-enrichment of metal silicide NWs by thermal diffusion. This conversion method could prove highly valuable, since novel metal-rich silicide NWs that are difficult to synthesize but possess interesting physical properties can be fabricated from other metal silicide NWs.”
The research result was published in Nanao Letters, a leading peer-reviewed journal, and posted online in early August 2010.
2010.08.25 View 10405 -
The 6th president of KAIST passed away on May 7, 2010.
Dr. Sang-Soo Lee was the first president of Korea Advanced Institute of Science (KAIS) and the 6th president of KAIST, who died of a chronic disease at the age of 85. The KAIS was the matrix of KAIST today. Graduated from the physics department of Seoul National University in 1949, he later received a doctoral degree in optics from Imperial College of Science and Technology, University of London.
Dr. Lee has greatly contributed to the development of science and technology in Korea in the capacity of a policy administrator, educator, scientist, researcher, and engineer. He held numerous prestigious offices including President of Korea Atomic Energy Research Institute in 1967, of KAIS in 172, and of KAIST in 1989. Dr. Lee also worked as a professor at the physics department of KAIST for 20 years from 1972-1992.
The Society of Photographic Instrumentation Engineers (SPIE), an international society for optics and photonics, was founded in 1955 to advance light-based technologies. Dr. Sang-Soo Lee was a member of the SPIE that issued a news release expressing its sincere condolences to his death. The following is the full text of the news release: http://spie.org/x40527.xml
In memoriam: Sang Soo Lee
10 May 2010
Sang Soo Lee, known as the "Father of Optics" in Korea passed away on May 7, 2010, in Korea. He was 84.
Lee received a B.S. in Physics from Seoul National University in Korea and a Ph.D. from Imperial College of Science and Technology, University of London, UK. Receiving the first Ph.D. in Optics in Korea, Dr. Lee devoted his life to lay the foundation for optical science and engineering for more than four decades as an educator, researcher, and administrator in science policy.
"He was one of the architects of the extraordinary and rapid emergence of Korea as a world leader in science and technology, or perhaps with the rich history of contributions centuries ago, re-emergence would be more appropriate." said Eugene G. Arthurs, SPIE Executive Director.
During his teaching career, Dr. Lee mentored 50 doctoral and more than 100 masters" degree candidates. in the areas of laser physics, wave optics, and quantum optics. Many of his former students have become leaders in academia, government-funded research institutes, and industry both in Korea and abroad. He published more than 250 technical papers and authored five textbooks, including "Wave Optics", "Geometrical Optics", "Quantum Optics", and "Laser Speckles and Holography".
Lee was the first president of the Korea Advanced Institute of Science and Technology (KAIST), and the first president to establish a new government funded graduate school. He played a pivotal role in founding the Optical Society of Korea (OSK) in 1989 and served as its first president.
Lee was an active member of the international scientific community. In addition to his pioneering scholastic achievements at KAIST, he served as the Vice President of the International Commission for Optics (ICO), a Council Member of the Third World Academy of Sciences, and a Council Member of UN University, serving as an ambassador for the optics community, which showed a significant example of how a developing country like Korea can serve international optics community.
Dr. Lee was a Fellow of the International Society for Optical Engineering (SPIE), the Optical Society of America (OSA), and the Korean Physical Society (KPS). He was the recipient of many awards and honors, including the National Order of Civil Merit that is the Presidential Medal of Honor from the Republic of Korea (2000), the Songgok Academic Achievement Prize, the Presidential Award for Science, and the Medal of Honor for Distinguished Scientific Achievement in Korea. In 2006, he was awarded OSA"s Esther Hoffman Beller Medal.
2010.05.19 View 12774 -
Professor Eun-Seong Kim and his research staff observed the phenomena of hysteresis and relaxation dynamics from supersolid Helium
Professor Eun-Seong Kim and his research staff observed the phenomena of hysteresis and relaxation dynamics from supersolid Helium.
Their research paper was published in Nature Physics for the issue of April 2010.
If we take Helium 4 and cool it down at temperatures below 2.176 Kelivin, liquid helium 4 undergoes a phase transition and becomes superfluid with a zero viscosity. The superfluidity was observed in solid helium through an experiment performed by researchers of Pennsylvania State University in 2004. One of the researchers then was Professor Eun-Seong Kim in the Department of Physics, KAIST.
Professor Kim and his research staff, Hyung-Soon Choi, Ph.D., recently published their research results in Nature Physics (April 2010), a highly esteemed journal in the field, on the phenomena of hysteresis and relaxation dynamics observed in supersolid Helium.
For the paper, please download the attached .pdf file.
Nature Physics link: http://www.nature.com
2010.04.13 View 11962 -
New Text Book on Chemistry Published by KAIST Professor and Student
A chemistry textbook written in English and Korean will aid Korean students to learn General Chemistry in a global academic setting.
Korean students majoring in chemistry and looking for an opportunity to study abroad will have a new, handy textbook that presents them with a practical introduction to an English speaking lecture on general chemistry.
Aiming for advanced Korean high school and college/university students, the inter-language textbook is written by two incumbent professors teaching chemistry at a university in Korea and the US. The book will help Korean students prepare for a classroom where various topics of general chemistry are presented and discussed in English. Clear, collated sections of English and Korean text provide the student with sufficient explanation of the rudimentary topics and concepts.
Composed of 15 chapters on the core subjects of General Chemistry, i.e., Stoichiometry and Chemical Reactions, Thermochemistry, Atomic Structure, and Bonding, the textbook includes essential English vocabulary and usage sections for each chapter; it also contains a pre-reading study guide on the subject that prepares the student for listening to a lecture. This section includes view-graph type slides, audio files, and follow-up questions the student can use to prepare for an English-speaking course. The various accompanying audio files are prepared to expose the student to English scientific dialogue and serve as examples for instruction at Korean secondary and tertiary schools.
The book was coauthored by Korean and American scientists: A father and son, who have taught chemistry at an American and Korean university, wrote the book. Professor Melvyn R. Churchill at the State University of New York at Buffalo and Professor David G. Churchill at KAIST prepared all of the technical English text which was adapted from General Chemistry course lecture notes; the text was further shaped by original perspectives arising from many student interactions and questions.
This English text was translated into Korean by Professor Kwanhee Lee from the Department of Life and Food Science at Handong Global University, who coauthored a previous preparatory book for Korean students in a different subject. He also supplied an important introductory section which serves as a general guide to the classroom student. Kibong Kim, a doctoral student in the Department of Chemistry at KAIST, helped in preparing the book as well.
“This has been definitely a collaborative undertaking with an international academic crew and it underscores that the Korean internationalization in science is mainstream. Professors and a Korean student created a new book for Korean consumption and benefit,” Professor David G. Churchill says.
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Bibliography: “How to Prepare for General Chemistry Taught in English” by David George Churchill, Melvyn Rowen Churchill, Kwanhee Lee & Kibong Kim, Darakwon Publishing, Paju, Republic of Korea, 2010, 400 pp, ISBN 978-89-5995-730-9 (1 Audio CD included)
2010.04.02 View 13490 -
Prof. Ryoo's Team Discovers Breakthrough Method to Create New Zeolite
A group of scientists led by Prof. Ryong Ryoo of the Department of Chemistry, KAIST, has found a method to direct the growth of zeolite, a crystalline substance that is frequently used as catalyst in the chemical and petrochemical industries, the university authorities said on Thursday (Sept. 10).
Ryoo"s research team successfully created ultrathin nano-sheets, only two nano-meters thick, that are efficiently used as long-life catalysts for hydrocarbon cracking and other petrochemical applications. The breakthrough finding, which is credited with taking acidic zeolite catalysts to the limit in terms of thickness, was published in the latest edition of the peer-review journal, "Nature."
A team from the Polytechnic Univeristy of Valencia, Spain, also contributed to the research.
Zeolites are already widely used in the petrochemical industry, but making the catalysts very thin means that reactant molecules can easily diffuse into the zeolite structure and product molecules can get out quickly. This improves the efficiency of the catalyst and reduces unwanted side reactions that can produce polymeric hydrocarbon "coke" that clogs the zeolite pores and eventually kills the catalytic activity, Prof. Yoo said.
To make the thin sheets, Ryoo and his team used a surfactant as a template to direct the growth of the zeolite structure. The surfactant molecule has a polar "head" group - with two quaternary ammonium groups around which the aluminosilicate zeolite crystal grows - and a long hydrocarbon "tail," which prevents the sheets from aggregating together into larger, three dimensional crystals. When the surfactant is removed, these flakes pile up randomly with gaps in between which further aids diffusion to the catalyst sites.
"Zeolite could be used as a catalyst to convert heavy oil into gasoline. Our new zeolite could provide even more possibilities, such as being used as catalysts for transforming methanol into gasline," Ryoo said.
Prof. Ryoo, a Distinguished Professor of KAIST, has won a variety of academic awards, which included the Top Scientist Award given by the Korean government in 2005 and the 2001 KOSEF Science and Technology Award for his work on the synthesis and crystal structure of mezzoporous silica.
Ryoo obtained his bachelor"s degree from Seoul National University in 1977, master"s from KAIST in 1979, and doctorate from Stanford University in 1985.
In 2006, Ryoo and his research team announced the discovery of a form of zeolite that can catalyze petrochemical reactions much more effectively than previous zeolites. Because of the potential of this to streamline the gasoline refining process, it was greeted as a "magical substance" by the South Korean press.
2009.09.11 View 11773 -
Scaling Laws between Population and Facility Densities Found
A research team led by Prof. Ha-Woong Jeong of the Department of Physics, KAIST, has found a positive correlation between facilities and population densities, university authorities said on Tuesday (Sept. 2). The research was conducted in the cooperation with a research team of Prof. Beom-Jun Kim at Sungkyunkwan University.
The researchers investigated the ideal relation between the population and the facilities within the framework of an economic mechanism governing microdynamics.
In previous studies based on the global optimization of facility positions in minimizing the overall travel distance between people and facilities, the relation between population and facilities should follow a simple law. The new empirical analysis, however, determined that the law is not a fixed value but spreads in a broad range depending on facility types.
To explain this discrepancy, the researchers proposed a model based on economic mechanism that mimics the competitive balance between the profit of the facilities and the social opportunity cost for population.
The results were published in the Proceedings of the National Academy of Sciences of the United States on Aug. 25.
2009.09.04 View 11963
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Prof. Song Develops Nano-Structure to Enhance Power of Rechargeable Lithium-ion Battery
A team of scientists led by Prof. Hyun-Joon Song of the Department of Chemistry, KAIST, developed a nano-structure that could increase the power of rechargeable lithium-ion batteries, university sources said on Monday (Feb. 16).
The research team found that a nano-structured material using copper oxide (CuO) could produce lithium-ion batteries with some 50 percent more capacity than conventional products. The study was published in the online edition of peer-review journal Advanced Materials.
In rechargeable lithium-ion batteries, lithium ions move between the battery"s anode and cathode. The high-energy density of the batteries led to their common use in consumer electronics products, expecially portable devices. Their demand in automotive and aerospace applications is growing, and nano-structured, or nano-enabled batteries are emerging as the new generation of lithium-ion batteries for their edge in recharging time, capacity and battery life.
Graphite has been a popular material for cathodes in lithium-ion batteries. However, graphite cathodes are also blamed for lost capacity due to their consumption of lithium ions, which are linked to shorter battery life.
As such, scientists have been looking for materials that could replace graphite in cathodes, and silicon and metal oxide have been studied as possible alternatives.
2009.02.17 View 11252
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KAIST Professor Finds Paradox in Human Behaviors on Road
-Strange as it might seem, closing roads can cut delays
A new route opened to ease traffic jam, but commuting time has not been reduced.Conversely, motorists reached their destinations in shorter times after a big street was closed. These paradoxical phenomena are the result of human selfishness, according to recent findings of a research team led by a KAIST physics professor.
Prof. Ha-Woong Jeong, 40, at the Department of Physics, conducted a joint research with a team from Santa Fe Institute of the U.S. to analyze the behaviors of drivers in Boston, New York and London. Their study found that when individual drivers, fed with traffic information via various kinds of media, try to choose the quickest route, it can cause delays for others and even worsen congestion.
Prof. Jeong and his group"s study will be published in the Sept. 18 edition of the authoritative Physical Review Letters. The London-based Economist magazine introduced Prof. Jeong"s finding in its latest edition.
Prof. Jeong, a pioneer in the study of "complex system," has published more than 70 research papers in the world"s leading science journals, including Nature, PNAS and Physical Review Letters. "Initially, my study was to reduce annoyance from traffic jam during rush hours," Prof. Jeong said. "Ultimately, it is purposed to eliminate inefficiency located in various corners of social activities, with the help of the network science."
The Economist article read (in part):
"...when individual drivers each try to choose the quickest route it can cause delays for others and even increase hold-ups in the entire road network.
"The physicists give a simplified example of how this can happen: trying to reach a destination either by using a short but narrow bridge or a longer but wide motorway. In their hypothetical case, the combined travel time of all the drivers is minimized if half use the bridge and half the motorway. But that is not what happens. Some drivers will switch to the bridge to shorten their commute, but as the traffic builds up there the motorway starts to look like a better bet, so some switch back. Eventually the traffic flow on the two routes settles into what game theory calls a Nash equilibrium, named after John Nash, the mathematician who described it. This is the point where no individual driver could arrive any faster by switching routes.
"The researchers looked at how this equilibrium could arise if travelling across Boston from Harvard Square to Boston Common. They analysed 246 different links in the road network that could be used for the journey and calculated traffic flows at different volumes to produce what they call a “price of anarchy” (POA). This is the ratio of the total cost of the Nash equilibrium to the total cost of an optimal traffic flow directed by an omniscient traffic controller. In Boston they found that at high traffic levels drivers face a POA which results in journey times 30% longer than if motorists were co-ordinated into an optimal traffic flow. Much the same thing was found in London (a POA of up to 24% for journeys between Borough and Farringdon Underground stations) and New York (a POA of up to 28% from Washington Market Park to Queens Midtown Tunnel).
"Modifying the road network could reduce delays. And contrary to popular belief, a simple way to do that might be to close certain roads. This is known as Braess’s paradox, after another mathematician, Dietrich Braess, who found that adding extra capacity to a network can sometimes reduce its overall efficiency.
"In Boston the group looked to see if the paradox could be created by closing any of the 246 links. In 240 cases their analysis showed that a closure increased traffic problems. But closing any one of the remaining six streets reduced the POA of the new Nash equilibrium. Much the same thing was found in London and New York. More work needs to be done to understand these effects, say the researchers. But even so, planners should note that there is now evidence that even a well intentioned new road may make traffic jams worse."
2008.09.18 View 13282 -
Prof. Kim Receives Lee Osheroff Prize
Professor Eun-Seong Kim of the Department of Physics has been selected as the winner of the Lee Osheroff Richardson Prize for 2008.
The award was established in honor of the 1996 Nobel Prize laureates in Physics David Lee, Douglas Osheroff, and Robert Richardson for their discovery in superfluidity in helium-3. The annual prize sponsored by Oxford Instruments NanoScience is awarded to a young scientist who has made a notable achievement in the field of low temperatures and high magnetic fields.
Kim was chosen as the winner of this prestigious award for his contributions to the understanding of solid helium. Through research, Professor Kim found superfluid-like behavior in solid helium and with this discovery it is shown that all three states of matter can exhibit superfluid behavior.
The Lee Osheroff Richardson Prize recipient is selected by the North American Prize Committee which is composed of prominent figures in the low temperature and high magnetic fields including Professor Bruce Gaulin of McMaster University, who chairs the Prize Committee. The award ceremony was held on March 11 in New Orleans.
2008.03.18 View 12703 -
Professor Jie-Oh Lee of the Department of Chemistry of KAIST
Professor Jie-Oh Lee of the Department of Chemistry of KAIST was selected as the "KAIST Man of the Year."
Lee was cited for his successful identifying of the three-dimensional structure of protein that causes sepsis. His research is expected to contribute greatly to the development of medicines for immune system treatment.
The prize was given by KAIST President Suh Nam Pyo at the New Year"s ceremony on Jan. 2, 2008 at the KAIST auditorium.
Professor Lee published a series of research papers in Science, one of the world"s most prestigious scientific journals. Most recently, Lee was awarded the "Scientist of the Year" prize by the Korean Science Reporters Association.
2008.01.02 View 13436 -
Professor Jie-Oh Lee awarded 'Scientist of the Year'
Professor Jie-Oh Lee of the Department of Chemistry was awarded the ‘Scientist of the Year’ prize for identifying the three-dimensional structure of protein that causes sepsis, and it was announced by the Korean Science Reporters Association (KOSRA) on November 26th.“Humans have about 30,000 different kinds of proteins, and they all have different structures, just like our faces,” said Professor Lee. “It is extremely helpful to know the three-dimensional shape of proteins when you are trying to understand what their functions in an organism are and trying to develop medicine for them.”
When looking for the three-dimensional structure, protein must first be crystallized and radiated with x-ray, so that reflected x-ray can be interpreted. The three-dimensional structure of sepsis immunity proteins TLR1-TLR2 and TLR4-MD2 could not be found until now because they would not even crystallize.
“I began to doubt if it was even possible to crystallize them because we went through so many failures,” reflected Professor Lee.
In August of last year, after about three years of research, the team finally came up with a new idea. The team decided to ‘stick’ the sepsis immunity protein to protein that easily crystallizes. If the combined structure of sepsis immunity protein and the known protein could be identified, the structure of sepsis immunity protein would be a combined structure subtracted by the known structure.
The three-dimensional structure was obtained with x-ray radiation from combined protein crystal. The combined protein was derived from an insect cell with altered DNA.
“This method seems very simple but no one ever tried it or no one ever succeeded in it,” said Professor Lee.
The result was a horseshoe shaped protein structure. The research team also expects the new protein-combining technology to contribute to the development of a new immune system treatment medicine.
The prize-awarding ceremony was held on November 26th in an event hosted by the Korean Hospital Association.
Also, Professor Ryong Ryoo of the Department of Chemistry was selected as the National Scientist last month.By KAIST Herald on November, 2007
2007.12.21 View 13050 -
Professor Churchill listed on international biographical dictionary
Professor Churchill listed on international biographical dictionary
Professor David G. Churchill (Department of Chemistry) is listed in Who’s Who in the World in its edition for 2007, international biographical dictionary published by Marquis Who’s Who.
Professor Churchill majored in Organometallic Chemistry and Chemistry of Complex at Colombia University in U.S. and began lectures at KAIST Chemistry department in July 2004.
Professor Churchill has presented 56 papers as member of the American Chemical Society and the Korea Chemical Society and is recognized for his excellent research performances. Recently, he is studying on a method to sense and counteract various toxic nervous substances by bonding them with metals.
2006.11.08 View 16128