Magnet
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Spintronics: A high wire act by Nanowerk News
An article by Nanowerk News on the integration of ferromagnetic nanowire arrays on grapheme substrates was published. Professor Bong-Soo Kim from the Department of Chemistry, KAIST, led the research in conjunction with Hanyang University and Samsung in Korea.
http://www.nanowerk.com/news/newsid=22204.php
Posted: Jul 25th, 2011
Spintronics: A high wire act
(Nanowerk News) Graphene is a promising material for a wide range of applications due to its remarkable mechanical and electronic properties. An application of particular interest is spin-based electronics, or spintronics, in which the spin orientation of an electron is used to perform circuit functions in addition to its charge. Bongsoo Kim and colleagues from KAIST, Hanyang University and Samsung in Korea now report the integration of ferromagnetic nanowire arrays on graphene substrates, opening up a route for the construction of graphene-based spintronic devices using nanowires as spin-injecting contacts ("Epitaxially Integrating Ferromagnetic Fe1.3Ge Nanowire Arrays on Few-Layer Graphene").
The spin of an electron is a property that, like charge, can be used to encode, process and transport information. However, spin information is easily lost in most media, which has made spintronics difficult to realize in practice. In graphene, on the other hand, spin can be preserved for longer due to its peculiar electron transport properties. "Low intrinsic spin–orbit coupling, long spin diffusion lengths and vanishing hyperfine interaction are features of graphene that make it a promising medium for spin transport," explains Kim.
Scanning electron microscopy image of vertical iron germanide nanowires grown on graphene. (© ACS 2011)
A prerequisite for the realization of spintronic devices based on graphene is its integration with ferromagnetic contacts to allow spin injection. Kim and his co-workers found that nanowires of iron germanide (Fe1.3Ge) serve as efficient contacts for this purpose. "Iron germanide nanowires show low resistivity and room-temperature ferromagnetism, and they are compatible with existing complementary metal–oxide–semiconductor technologies," says Kim.
To produce the atomically well-defined interfacial contact between the nanowires and the graphene surface needed for optimum device performance, the researchers deposited the contacts by an epitaxial method based on chemical vapor transport. Through careful adjustment of deposition parameters such as carrier gas flow rate and reaction temperature, the researchers produced vertically aligned nanowires that are closely lattice-matched to the graphene sheets (see image).
Initially preparing the graphene sheets on a substrate of silicon oxide allowed the researchers to isolate the final nanowire–graphene structure by etching and then transfer it to another substrate, greatly expanding the versatility of the approach. It is a delicate process, however. "It is necessary to transfer the graphene films onto the substrate very carefully in order to avoid folding and wrinkling of the graphene," says Kim.
Source: Tokyo Institute of Technology
2011.07.26 View 11342 -
Wireless electric trams at Seoul Amusement Park begin full operations.
Photo by Hyung-Joon Jun
IMMEDIATE RELEASE
Wireless electric trams at Seoul Amusement Park begin full operations.
KAIST’s On-Line Electric Vehicle (OLEV) becomes an icon of green technology, particularly for young students who aspire to transform their nation into the “vanguard of sustainability.”
Seoul, South Korea, July 19, 2011—As young students wrap up their school work before summer vacation in late July, Seoul Grand Park, an amusement park located south of Seoul, is busily preparing to accommodate throngs of summer visitors. Among the park’s routine preparations, however, there is something new to introduce to guests this summer: three wireless electric trams have replaced the old diesel-powered carts used by passengers for transportation within the park.
The Korea Advanced Institute of Science and Technology (KAIST) and the city of Seoul held a ceremony this morning, July 19, 2011, to celebrate their joint efforts to adopt a green public transportation system and presented park visitors with the three On-Line Electric Vehicles (OLEVs), which will be operated immediately thereafter. Approximately one hundred people, including science high school students across the nation, attended the ceremony and had a chance to ride the trams.
KAIST unveiled the prototype of an electric tram to the public in March 2010, and since then it has developed three commercial trams. The Korean government and the institute have worked on legal issues to embark on the full-scale commercialization of OLEV, and the long awaited approval from the government on such issues as standardization of the OLEV technology and road infrastructure, regulation of electromagnetic fields and electricity safety, and license and permits for vehicle eligibility, finally came through.
The On-Line Electric Vehicle (OLEV) is no ordinary electric car in that it is remotely charged via electromagnetic fields created by electric cables buried beneath the road. Unlike other currently available electric cars, OLEV can travel unlimited distances without having to stop to recharge. OLEV also has a small battery onboard, which enables the vehicle to travel on roads that are not equipped with underground power cables. This battery, however, is only one-fifth of the size of a conventional electric vehicle battery, resulting in considerable savings in the cost, size, and weight of the vehicle.
The OLEV project was initiated in 2009 as a method of resolving the battery problems of electric cars in a creative and disruptive way. KAIST came up with the idea of supplying electricity directly to the cars instead of depending solely on the onboard battery for power. Since then, the university has developed core technologies related to OLEV such as the “Shaped Magnetic Field in Resonance (SMFIR),” which enables an electric car to collect the magnetic fields and convert them into electricity, and the “Segment Technology,” which controls the flow of electromagnetic waves through an automatic power-on/shut-down system, thereby eliminating accidental exposure of the electromagnetic waves to pedestrians or non-OLEV cars.
According to KAIST, three types of OLEV have been developed thus far: electric buses, trams, and sport utility vehicles (SUVs). The technical specifications of the most recently developed OLEV (an electric bus), the OLEV research team at the university said, are as follows:
· Power cables are buried 15cm beneath the road surface.
· On average, over 80% power transmission efficiency is achieved.
· The distance gap between the road surface and the underbody of the vehicle is 20cm.
· The OLEV bus has a maximum electricity pickup capacity of 100kW.
· The OLEV bus complies with international standards for electromagnetic fields (below 24.1 mG).
The eco-friendly electric trams at Seoul Grand Park consume no fossil fuels and do not require any overhead wires or cables. Out of the total circular driving route (2.2km), only 16% of the road, 372.5m, has the embedded power lines, indicating that OLEV does not require extensive reconstruction of the road infrastructure. The city government of Seoul signed a memorandum of understanding with KAIST in 2009 as part of its initiatives to curtail emissions from public transportation and provide cleaner air to its citizens. Both parties plan to expand such collaboration to other transportation systems including buses in the future.
KAIST expects the OLEV technology to be applied in industries ranging from transportation to electronics, aviation, maritime transportation, robotics, and leisure. There are several ongoing international collaborative projects to utilize the OLEV technology for a variety of transportation needs, such as inner city commute systems (bus and trolley) and airport shuttle buses, in nations including Malaysia, US, Germany, and Denmark.
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More information about KAIST’s On-Line Electric Vehicle can be found at http://olev.co.kr/en/index.php. For any inquiries, please contact Lan Yoon at 82-42-350-2295 (cell: 82-10-2539-4303) or by email at hlyoon@kaist.ac.kr.
2011.07.22 View 16072 -
Professor Min Beom Ki develops metamaterial with high index of refraction
Korean research team was able to theoretically prove that a metamaterial with high index of refraction does exist and produced it experimentally.
Professor Min Beom Ki, Dr. Choi Moo Han, and Doctorate candidate Lee Seung Hoon was joined by Dr. Kang Kwang Yong’s team from ETRI, KAIST’s Professor Less Yong Hee’s team, and Seoul National University’s Professor Park Nam Kyu’s team. The research was funded by the Basic Research Support Program initiated by the Ministry of Education, Science, and Technology and Korea Research Federation.
The result of the research was published in ‘Nature’ magazine and is one of the few researches carried out by teams composed entirely of Koreans.
Metamaterials are materials that have physical properties beyond those materials’ properties that are found in nature. It is formed not with atoms, but with synthetic atoms which have smaller structures than wavelengths.
The optical and electromagnetic waves’ properties of metamaterials can be altered significantly which has caught the attention of scientists worldwide.
Professor Min Beom Ki’s team independently designed and created a dielectric metamaterial with high polarization and low diamagnetism with an index of refraction of 38.6, highest synthesized index value.
It is expected that the result of the experiment will help develop high resolution imaging system and ultra small, hyper sensitive optical devices.
2011.02.23 View 18344
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OLEV Safety Confirmed by International Standards
On September 19, KAIST announced that the electromagnetic (EM) field levels of its online electric vehicle (OLEV) measured in June and September of this year demonstrated verification of its safety.
Last June, the EM field level of OLEV installed at the Seoul Grand Park was measured by the Korea Research Institute of Standards and Science (KRISS) to test its harmfulness to human. The results were 0.5 ~ 61mG which is within the national and international standards of 62.5mG.
KRISS measured EM field levels on 22 spots on the side of and at the center of OLEV at a fixed distance (30cm) but variable heights (5cm~150cm) according to the national standard of measurement methods for electromagnetic fields of household appliances and similar apparatuses with regard to human exposure (IEC 62233).
In addition, another testing took place on September 13 following a request by National Assemblywoman Young-Ah Park, a member of the National Assembly’s Education, Science and Technology Committee, who has raised an issue on the safety of OLEV. This testing session was held by EMF Safety, Inc., an institution designated by Park, and it tested the EM field level of the same OLEV train that was tested in June.
As a result, the September measurements were well within the national and international standards with 0~24.1mG. The test was conducted under the presence of third party to produce a fair and objective result.
As reference, the EM field level results are well within the American IEEE electromagnetic field standards of 1,100 mG.
The September measurements were produced by Park’s recommendation of following the criteria specified in the measurement procedures of IEC 62110, “Electric and magnetic field levels generated by AC power systems to public exposure,” which were 15 measurements at a fixed 20cm distance at the side of and from the center of OLEV with variable heights of 50cm~150cm.
2010.09.27 View 13414 -
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 12156 -
KAIST's OLEV Best Model of Creative Growth Engine
Various models of electric vehicles designed to replace the internal combustion automobiles face significant problems as they invariably failed to overcome the limitations involving lithium battery in terms of power capacity, weight, raw materal price, recharging time and preparation of charging stations. Worst of all, the limited supply of lithium will eventually raise its price sky high when all cars use lithium batteries, and the economic value of electric cars will be lost.
KAIST"s online electric vehicle project (OLEV) seeks to resolve these fundamental problems involving electric vehicles that have so far been developed. KAIST OLEV, a project to develop a new growth engine for the nation and lead the future of global automotive industry, is an entirely new concept: the electric vehicle picks up power from underground power supplier lines through the non-contact magnetic charging method, while either running or standing. This is the first eco-friendly and economic automotive system that can resolve the problems inherent to previously-developed electric vehicles, according to the KAIST OLEV Project Center.
In February 2009, KAIST researchers first proved that up to 80 percent power conveyance is possible through a gap of 1 centimeter from the power line, and in July they successfully supplied power to a bus -- up to 60 percent across a 12 cm gap from the power line embedded in the ground -- using power supply and pick-up devices they developed. In this process, KAIST has secured the core technologies for maximizing power efficiency and minimizing the cost of installing the non-contact power supply system. KAIST has established the Online Electric Vehicle Co., Ltd., to undertake business activities related to the OLEV project, including the IPR on power supply and pick-up devices, parts and accessories and commercial promotion. A demonstration event is scheduled for Aug. 13, Thursday.
The impact of the development of the OLEV technology on the energy and environment issues and the overall economy will be enormous. In case a half of the total automobiles running in Korea, or 6 million vehicles, are replaced with OLEV, electric power produced by just two of the nation"s atomic power plants will be enough to operate them all, and the nation will be able to reduce crude oil import by 35 million barrels worth U.S.$3 billion a year (supposing $80 per barrel).
Korea"s export of OLEV units will in the future surpass the present level of overseas sale of conventional cars. When nations use online electric vehicles in large numbers, their demand for CO2-free power plants will grow. Korea has cutting-edge technology in the construction of atomic power plants. As a world leader in the area of nuclear power plant, Korea will enjoy new opportunities to contribute to the global advancement of atomic power generation as well as transportation industries.
Korea still shares a small portion of the world"s automobile market estimated to worth some 2,000 trillion Korean won. But commercialization of the OLEV technology worldwide will greatly enhance Korea"s global automotive market share. Successful development of the online electric vehicle requires preemptive investment and positive support by the government for the ultimate purpose of resolving energy and environment problems.
If and when domestic enterprises secure technological supremacy in the next generation automobile market with their online electric vehicles which will replace the 100-year-old combustion engine, it will be the most desirable shortcut to raising Korea"s international competitiveness. OLEV promises to be the model of creative growth engine in the 21st century.
2009.07.30 View 17853
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KAIST Wins First Prize at Recon Challenge of Int"l Magnetic Resonance Society
Professor Jong-chul Ye of the Department of Bio and Brain Engineering and Hong Jeong, a doctorate student, won the first prize at the Recon Challenge held as part of a workshop sponsored by the International Society for Magnetic Resonance in Medicine (ISMRM) held in Sedona, the United States.
The workshop took place under the theme of “data sampling and image reconstruction” on Jan. 25-28 in Sedona, Arizona, the United States. The KAIST team beat out major magnetic resonance imaging groups from the U.S. and Europe.
The Recon Challenge is a biennial competition highlighting different reconstruction strategies and metrics to compare them. ISMRM is an international, nonprofit, scientific association which promotes communication, research, development, and applications in the field of magnetic resonance in medicine and biology and other related topics.
At the competition, the KAIST team presented a new dynamic MRI algorithm called k-t FOCUSS that is optimal from a compressed sensing perspective. The main contribution of the method is extension of k-t FOCUSS to a more general framework with prediction and residual encoding. The prediction provides an initial estimate while the residual encoding takes care of the remaining residual signals.
2009.02.06 View 15011 -
Two KAIST Professors Elected Fellows of APS
Profs. Sung-Chul Shin and Chang-Hee Nam of the Department of Physics, KAIST, have recently been elected the 2009 fellows of the American Physical Society (APS), university officials said on Tuesday (Dec. 2).
The APS fellowship is a prestigious recognition of the two professors" outstanding academic achievements in the field of physics, the officials said. The selection criteria are known to be extremely stringent and only a small fraction of APS members become fellows.
Prof. Shin was cited for his pioneering contributions to the understanding of magnetization reversal dynamics, in particular critical scaling behavior of Barkhausen avalanches of 2D ferromagnets, and discovery of novel magnetic thin films and multilayers for high-density data storage.
Prof. Nam was recognized for his contributions to the theory and experiments of physical processes of high harmonic generation for the development of attosecond coherent x-ray sources and related femtosecond laser technology.
The American Physical Society, founded in 1899, is the world"s second largest organization of physicists, behind the Deutsche Physikalische Gesellschaft. It has 46,000 members across the world.
2008.12.04 View 15392 -
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 14611 -
Professor Chung-Seok Chang named as APS Fellow
Professor Chung-Seok Chang named as APS Fellow
- Honorable position offered only to an extremely small number of members within 0.5% of APS
- Recognized for his leading and creative contribution to Plasma conveyance theory, Electromagnetic waves heating theory and leadership in the research field of large-scaled computer simulation
Professor Chung-Seok Chang (Department of Physics) was named as a fellow of the American Physics Society (APS), world-renowned society in the physics filed.
The fellow of the APS is considered as a position of great honor among scholars in the field of Physics since only a small number of regular members within 0.5% of the APS can become the fellows. Professor Chang was recognized for his leading and creative contribution to the fields of Plasma conveyance theory, Electromagnetic waves heating theory and leadership in the research field of large-scaled computer simulation, which made him named as APS fellow.
Professor Chang has been invited several times to the Main Policy Committee of the U.S. Department of Energy and was a member of On-site Review Committee on the theoretical research activities of the U.S. major state-run institutes. Due to many world-recognized research results carried out with KAIST students, he has been invited several times for lecture to the conference of the APS as well as large-scaled international academic conferences. As a result, KAIST doctorates of Computational Physics from his laboratory are recognized globally for their excellence in the field of nuclear fusion.
Besides, Professor Chang was assigned as the Chief General of the super-sized Computational Theory Research Group last year, to which the U.S Department of Energy will invest 6 million dollars of research fund for three years, and manages the complex theory research group that transcribes and reproduces the properties of nuclear fusion plasma by using large-scaled parallel computers with its head quarter in the U.S. Courant Institute of Mathematical Sciences. This research group consists of greatest U.S. scholars in the fields of Physics, Mathematics, and Computation, belonging to 14 research-education institutes such as Princeton University, Colombia University, MIT, University of California Engineering College, California State University, Rutgers University, New-York University, Courant Institute of Mathematical Sciences, Oak Ridge National Lab, Berkeley National Laboratories, etc., thereby gathering worldwide
2006.10.25 View 14527