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Development of a Photonic Diode with Light Speed, Single-Direction Transfer
A photonic diode using a nitride semiconductor rod can increase the possibility of developing all-optical integrated circuits, an alternative to conventional integrated circuits.
Professor Yong-Hoon Cho's research team from the Department of Physics, KAIST, developed a photonic diode which can selectively transfer light in one way, using semiconductor rods.
The photonic diode has a diameter of hundreds of nanometers (nm) and a length of few micrometers. This size enables its use in large-scale integration (LSI). The diode’s less sensitivity towards polarized light angle makes it more useful.
In an integrated circuit, a diode controls the flow of electrons. If this diode controls light rather than electrons, data can be transferred at high speed, and its loss is minimized to a greater extent. Since these implementations conserve more energy, this is a very promising future technology.
However, conventional electronic diodes, made up of asymmetric meta-materials or photonic crystalline structures, are large, which makes them difficult to be used in LSI. These diodes could only be implemented under limited conditions due to its sensitivity towards polarized light angle.
The research team used nitride semiconductor rods to develop a highly efficient photonic diode with distinct light intensities from opposite ends.
The semiconductor rod yields different amount of energy horizontally. According to the research team, this is because the width of the quantum well and its indium quantity is continuously controlled.
Professor Cho said, "A large energy difference in a horizontal direction causes asymmetrical light propagation, enabling it to be operated as a photonic diode." He added that “If light, instead of electrons, were adopted in integrated circuits, the transfer speed would be expected as great as that of light.”
The research findings were published in the September 10th issue of Nano Letters as the cover paper.
Under the guidance of Professor Cho, two Ph.D. candidates, Suk-Min Ko and Su-Hyun Gong, conducted this research. This research project was sponsored by the National Research Foundation of Korea and KAIST’s EEWS (energy, environment, water, and sustainability) Research Center.
Figure Description: Computer simulated image of photonic diode made of semiconductor rod implemented in an all-optical integrated circuit
2014.09.23 View 10272 -
An Electron Cloud Distribution Observed by the Scanning Seebeck Microscope
All matters are made of small particles, namely atoms. An atom is composed of a heavy nucleus and cloud-like, extremely light electrons.
Korean researchers developed an electron microscopy technique that enables the accurate observation of an electron cloud distribution at room-temperature. The achievement is comparable to the invention of the quantum tunneling microscopy technique developed 33 years ago.
Professor Yong-Hyun Kim of the Graduate School of Nanoscience and Technology at KAIST and Dr. Ho-Gi Yeo of the Korea Research Institute of Standards and Science (KRISS) developed the Scanning Seebeck Microscope (SSM). The SSM renders clear images of atoms, as well as an electron cloud distribution. This was achieved by creating a voltage difference via a temperature gradient.
The development was introduced in the online edition of Physical Review Letters (April 2014), a prestigious journal published by the American Institute of Physics.
The SSM is expected to be economically competitive as it gives high resolution images at an atomic scale even for graphene and semiconductors, both at room temperature. In addition, if the SSM is applied to thermoelectric material research, it will contribute to the development of high-efficiency thermoelectric materials.
Through numerous hypotheses and experiments, scientists now believe that there exists an electron cloud surrounding a nucleus. IBM's Scanning Tunneling Microscope (STM) was the first to observe the electron cloud and has remained as the only technique to this day. The developers of IBM microscope, Dr. Gerd Binnig and Dr. Heinrich Rohrer, were awarded the 1986 Nobel Prize in Physics.
There still remains a downside to the STM technique, however: it required high precision and extreme low temperature and vibration. The application of voltage also affects the electron cloud, resulting in a distorted image.
The KAIST research team adopted a different approach by using the Seebeck effect which refers to the voltage generation due to a temperature gradient between two materials.
The team placed an observation sample (graphene) at room temperature (37~57℃) and detected its voltage generation. This technique made it possible to observe an electron cloud at room temperature.
Furthermore, the research team investigated the theoretical quantum mechanics behind the electron cloud using the observation gained through the Seebeck effect and also obtained by simulation capability to analyze the experimental results.
The research was a joint research project between KAIST Professor Yong-Hyun Kim and KRISS researcher Dr. Ho-Gi Yeo. Eui-Seop Lee, a Ph.D. candidate of KAIST, and KRISS researcher Dr. Sang-Hui Cho also participated. The Ministry of Science, ICT, and Future Planning, the Global Frontier Initiative, and the Disruptive Convergent Technology Development Initiative funded the project in Korea.
Picture 1: Schematic Diagram of the Scanning Seebeck Microscope (SSM)
Picture 2: Electron cloud distribution observed by SSM at room temperature
Picture 3: Professor Yong-Hyun Kim
2014.04.04 View 12976 -
Extreme Tech: Nanowire "impossible to replicate" fingerprints could eliminate fraud, counterfeit goods
Research done by Professor Hyun-Joon Song of Chemistry at KAIST on
anti-counterfeit, nanoscale fingerprints generated by randomly distributed
nanowires was introduced by Extreme Tech, an online global science and technology
news.
For the articles, please go to:
Extreme Tech, March 25, 2014Nanowire ‘impossible to replicate’ fingerprints could eliminate fraud, counterfeit goods
http://www.extremetech.com/extreme/179131-nanowire-impossible-to-replicate-fingerprints-could-eliminate-fraud-counterfeit-goods
2014.03.26 View 7809 -
Household Scale Indoor Position Tracking Technology Developed
Technology that will allow household scale position tracking of smartphones indoors, where GPS signals do not reach, has been developed. It is anticipated that the newly developed technology will enable the tracking of persons indoors in an emergency situation or aid in the finding of a lost smartphone.
Professor Han Dong Soo (Department of Computer Sciences) and his research team has developed the technology that enables tracking a smartphone’s location indoors using wireless LAN signals accurate to 10 meters.
Because the technology utilizes wireless LAN signals and the address of smartphone users, the technology can be implemented for a low cost all over the world.
Conventionally the location of a lost smartphone can be found through a telecommunications company. However the location found using the base station is only accurate to 500m~700m and therefore reclaiming lost smartphones is nearly impossible.
In addition, there have been unfortunate events where the kidnapped victim called the police but was murdered due to the inaccuracy of smartphone location tracking.
The newly developed technology by Professor Han’s team remedies the inaccuracy of smartphone location tracking.
Professor Han’s team collected wireless LAN data recorded in the smartphones for a week to analyze the patterns to distinguish patterns between signals recorded in the workplace and in the household.
The stability and accuracy of the technology was verified over a period of five months in various locations across Korea with varying population densities.
The result was when the total amount of data collected passes 50% of the number of households, the technology show accuracy to 10 meters. The result showed that the new technology can track the location of the smartphone to 10 meters on a household scale. In addition it was possible to distinguish which floor the smartphone was located.
The technology is anticipated to improve smartphone positioning. However caution needs to be practiced as the technology requires the address of the user’s workplace and home.
2012.12.21 View 7583 -
Technology that will allow household scale position tracking of smartphones indoors, where GPS signals do not reach, has been developed. It is anticipated that the newly developed technology will enable the tracking of persons indoors in an emergency situ
Technology that will allow household scale position tracking of smartphones indoors, where GPS signals do not reach, has been developed. It is anticipated that the newly developed technology will enable the tracking of persons indoors in an emergency situation or aid in the finding of a lost smartphone.
Professor Han Dong Soo (Department of Computer Sciences) and his research team has developed the technology that enables tracking a smartphone’s location indoors using wireless LAN signals accurate to 10 meters.
Because the technology utilizes wireless LAN signals and the address of smartphone users, the technology can be implemented for a low cost all over the world.
Conventionally the location of a lost smartphone can be found through a telecommunications company. However the location found using the base station is only accurate to 500m~700m and therefore reclaiming lost smartphones is nearly impossible.
In addition, there have been unfortunate events where the kidnapped victim called the police but was murdered due to the inaccuracy of smartphone location tracking.
The newly developed technology by Professor Han’s team remedies the inaccuracy of smartphone location tracking.
Professor Han’s team collected wireless LAN data recorded in the smartphones for a week to analyze the patterns to distinguish patterns between signals recorded in the workplace and in the household.
The stability and accuracy of the technology was verified over a period of five months in various locations across Korea with varying population densities.
The result was when the total amount of data collected passes 50% of the number of households, the technology show accuracy to 10 meters. The result showed that the new technology can track the location of the smartphone to 10 meters on a household scale. In addition it was possible to distinguish which floor the smartphone was located.
The technology is anticipated to improve smartphone positioning. However caution needs to be practiced as the technology requires the address of the user’s workplace and home.
2012.12.21 View 8451
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Seeing Inside Cells with Fiber Optics
Professor Jiho Park’s research team was successful in receiving minute optical signals from inside the cell using optical nano fibers.
Through the invention of this technology, we can now look inside cells in high resolution without the use of equipment such as endoscopes that damage cells. We will be able to study the biological phenomena within cells, and thus cure diseases more effectively.
Recently, ultra high resolution microscopes have been used to analyze incubated cells. However, because of the need for a very complex and large system, it had been impossible to monitor cells in the less transparent areas of the body in real time.
The research team created the wire with a semiconductor created with tin oxides to be only 100 nanometers in diameter (1nanometer= 1/1billion meters).
The nanowire is connected to the end of the optical fiber, and the light that comes through the optical fiber is transmitted to particular spots in the cell, and the optical signals from the cell are retrieved back from the cell as well
Together with this, based on the fact that nanowires do not damage cells, the research team covered the end of the wire with a photo reactive material and entered this into the cell. They were able to check that the material reacted to light and entered the cell when they transmitted light
Accordingly, this showed the possibilities of the use of this technology as a method of treatment to effectively transfer the medication into the cells.
Prof. Jiho Park stated that “in this research, we only used cells incubated outside the human body, but soon we will use this technology to stimulate and control cells within the body in a minute scale” as well as that “soon, we will be able to study the biological phenomena inside a cell to study diseases and apply this to cure them more effectively”.
This research result has been published in the online publication of ‘Nature Nanotechnology’ on December 18.
This study was done through the cooperation of various schools. Besides Prof. Jiho Park, Prof. Seungman Yang from the Biochemistry department, and Doctor Chuljoon Huh from KAIST, Prof. Yeonho Choi from Biomedical Science department of Korea University, Professor Peidon Yang and Doctor Ruoxue Yan from UC Berkeley’s chemistry department, and Luke Lee from UC Berkeley’s bioengineering department participated in the project.
2012.01.31 View 9121
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Scientists develop highly efficient industrial catalyst
http://english.yonhapnews.co.kr/business/2011/07/14/48/0501000000AEN20110714009600320F.HTML
SEOUL, July 15 (Yonhap) -- South Korean scientists said Friday that they have developed a highly efficient nanoporous industrial catalyst that can have a considerable impact on chemical and oil-refining sectors.
The team of scientists led by Ryoo Ryong, a chemistry professor at the Korea Advanced Institute of Science and Technology (KAIST), said the solid zeolite compound developed in the laboratory has a reaction speed five to 10 times faster than that of conventional materials.
Zeolite, which is made from silica and aluminium, is frequently used as an absorbent, water purifier and in nuclear reprocessing, although it is mainly employed in the chemical industry.
The annual size of the zeolite market is estimated at US$2.5 billion with output using the material topping $30 billion. At present, 41 percent of all catalysts used in the chemical sector are nano-scale zeolite materials.
The KAIST team said that because the new zeolite is made up of different sized pores, the material can be used as a catalyst when existing materials are unable to act as a changing agent.
"Existing zeolites only have pores under 1 nanometer in diameter, but the new material has holes that range from 1 nanometer to 3.5 nanometers, which are all arranged in a regular honeycomb arrangement," Ryoo said. A nanometer is one-billionth of a meter.
He said the ability to have both micro- and meso-sized pores is key to the faster reaction speed that is an integral part of raising efficiency. The South Korean researchers used a so-called surfactant process to make the different sizes of pores.
The development is a breakthrough because researchers and companies such as Exxon Mobil Corp. have been trying to build zeolite with different sizes of pores for the past two decades without making serious headway. There are more than 200 different types of zeolites in the world.
Ryoo, who received funding from the government, has requested intellectual property rights for the discovery, which has been published in the latest issue of Science magazine. He also developed another zeolite in the past that can transform methanol to gasoline up to 10 times more efficiently than existing catalysts.
Exxon Mobil has expressed interest in the two zeolites made by Ryoo"s team. Undisclosed South Korean petrochemical companies have also made inquiries that may lead to commercial development in the future.
"There are some technical issues to resolve, mainly related with mass production and stability," the scientist said.
He said full-fledge production will be determined by how much companies are willing to spend on research to speed up development that can bring down overall production costs.
The KAIST team said it took two years to make the new zeolite, which can be custom made to meet specific needs.
(END)
2011.07.15 View 11362
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Prof. Seong Publishes English Book on Reliability in Digital Control Systems
Prof. Poong-Hyun Seong of Department of Nuclear and Quantum Engineering has recently published an English-language book on reliability and risk issues in large scale safety-critical digital control systems used in complex facilities such as nuclear power plants.
The book entitled “Reliability and Risk Issues in Large Scale Safety-critical Digital Control Systems” is a result of Prof. Seong’s collaboration with some KAIST graduates who used to be under his guidance. The 303-page publication has been published by Springer, one of the world’s leading publishers of academic journals, as part of the Springer Series in Reliability Engineering.
The book consists of four parts; part I deals with issues related to hardware, part II software, part III human factors and finally the last part integrated systems. It can be purchased through some on-line book stores such as Amazon.com.
Prof. Seong served as an editor-in-chief for Nuclear Engineering and Technology (NET), an international journal of Korean Nuclear Society (KNS), from 2003 to 2008. He also worked as a chair of the Human Factors Division (HFD) of American Nuclear Society (ANS) from 2006 to 2007. Prof. Seong is now a commissioner of Korea Nuclear Safety Commission which is the nation’s highest committee on Nuclear Safety.
2008.12.26 View 15054
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KAIST Team Identifies Nano-scale Origin of Toughness in Rare Earth-added Silicon Carbide
A research team led by Prof. Do-Kyung Kim of the Department of Materials Science and Engineering of KAIST has identified the nano-scale origin of the toughness in rare-earth doped silicon carbide (RE-SiC), university sources said on Monday (Oct. 6).
The research was conducted jointly with a U.S. team headed by Prof. R. O. Ritchie of the Department of Materials Science and Engineering, University of California, Berkeley.
The findings were carried in the online edition of Nano Letters published by the American Chemical Association.
Silicon carbide, a ceramic material known to be one of the hardest substances, are potential candidate materials for many ultrahigh-temperature structural applications. For example, if SiC, instead of metallic alloys, is used in gas-turbine engines for power generation and aerospace applications, operating temperatures of many hundred degrees higher can be obtained with a consequent dramatic increase in thermodynamic efficiency and reduced fuel consumption. However, the use of such ceramic materials has so far been severely limited since the origin of the toughness in RE-SiC remained unknown thus far.
In order to investigate the origin of the toughness in RE-SiC, the researchers attempted to examine the mechanistic nature of the cracking events, which they found to occur precisely along the interface between SiC grains and the nano-scale grain-boundary phase, by using ultrahigh-resolution transmission electron microscopy and atomic-scale spectroscopy. The research found that for optimal toughness, the relative elastic modulus across the grain-boundary phase and the interfacial fracture toughness are the most critical material parameters; both can be altered with appropriate choice of rare-earth elements.
In addition to identifying the nano-scale origin of the toughness in RE-SiC, the findings also contributed to precisely predicting how the use of various rare-earth elements lead to difference in toughness.
University sources said that the findings will significantly advance the date when RE-SiC will replace metallic alloys in gas-turbine engines for power generation and aerospace applications.
2008.10.08 View 13936 -
KAIST to build large-scale civil engineering experiment center
- Geo-Centrifuge experiment center of an area of about 1,712 square meters and an estimated construction cost of total 8.4 billion won
- Simulation laboratory in the field of geotechnical engineering with state-of-the-art experiment equipment- Ground-breaking ceremony held on April 3 at 4 pm
KAIST will construct ‘distributed shared-type Geo-Centrifuge experiment center’, a large-scale civil engineering laboratory that will study natural disasters such as earthquake, embankment collapse, etc. with ground structure miniatures.
A two-story building with a basement occupying an area of about 1,712 square meters will become a landmark laboratory in the field of geotechnical engineering that can be used for the education, research, and social infrastructure design by universities, institutes, and corporations via high-speed information and communication network. The estimated construction cost is 8.4 billion won.
The center will be composed of experiment building including geo-centrifuge laboratory, model-making room, workshop, geotechnical engineering laboratory, and specimen storehouse; and research building including control room, video conference room, electronic library, and research rooms. A variety of convenience facilities for researchers and video conference and remote monitoring system, with which researcher at remote distances can directly participate in experiments, will be provided in the research building, and world’s top-class experiment equipment such as geo-centrifuge with a turning radius of 5 meters, a maximum acceleration of 130 G (130 times faster than the acceleration of gravity), a preload of 2,400 kg and bidirectional shaking-table that can reproduce earthquakes-like wave during experiments, and robots that can reproduce construction procedures by a remote control will be installed.
Geo-Centrifuge experiment refers to an experiment that reproduces natural disaster-like motions by making miniatures of large-scale ground structures such as dams, slopes, etc. and using centrifugal forces generated from high-speed rotation. This experiment can easily and rapidly reproduce actual motions of ground structures at a low cost, thereby being widely used for various geotechnical engineering researches such as evaluation of seismic safety, movement of soft ground, slope stability analysis, etc. The causes of the embankment collapse in New Orleans by Hurricane Katrina in 2005 were also revealed by simulation tests by this experiment.
“The center will make possible a variety of experiments and researches that have never been available in Korea due to the lack of experiment infrastructure, therefore activate researches over the design and construction of large-scale social infrastructures. Making possible civil engineering researches demanding the use of large-scale equipment like Centrifuge, severely dependent on overseas technologies so far, will enhance the global competitiveness of Korean construction industry,” said Dong-soo Kim, President of the center.
The center will be constructed as part of the Ministry of Construction & Transportation (MOCT)’s project for the establishment of distributed shared-style construction research infrastructure, which is designed to establish construction research infrastructures in a national level. The ground breaking ceremony was held at KAIST on April 3 at 4 pm.
2007.04.12 View 14161