-
Making Graphene Using Laser-induced Phase Separation
IBS & KAIST researchers clarify how laser annealing technology can lead to the production of ultrathin nanomaterials
All our smart phones have shiny flat AMOLED (active-matrix organic light-emitting diode) displays. Behind each single pixel of these displays hides at least two silicon transistors which are mass-manufactured using laser annealing technology. While the traditional methods to make the transistors use temperature above 1,000°C, the laser technique reaches the same results at low temperatures even on plastic substrates (melting temperature below 300°C). Interestingly, a similar procedure can be used to generate crystals of graphene. Graphene is a strong and thin nano-material made of carbon, its electric and heat-conductive properties have attracted the attention of scientists worldwide.
Professor Keon Jae Lee of the Materials Science and Engineering Department at KAIST and his research group at the Center for Multidimensional Carbon Materials within the Institute for Basic Science (IBS), as well as Professor Sung-Yool Choi of the Electrical Engineering School at KAIST and his research team discovered graphene synthesis mechanism using laser-induced solid-state phase separation of single-crystal silicon carbide (SiC). This study, available in Nature Communications, clarifies how this laser technology can separate a complex compound (SiC) into its ultrathin elements of carbon and silicon.
Although several fundamental studies presented the effect of excimer lasers in transforming elemental materials like silicon, the laser interaction with more complex compounds like SiC has rarely been studied due to the complexity of compound phase transition and ultra-short processing time.
With high resolution microscope images and molecular dynamic simulations, scientists found that a single-pulse irradiation of xenon chloride excimer laser of 30 nanoseconds melts SiC, leading to the separation of a liquid SiC layer, a disordered carbon layer with graphitic domains (about 2.5 nm thick) on top surface and a polycrystalline silicon layer (about 5 nm) below carbon layer. Giving additional pulses causes the sublimation of the separated silicon, while the disordered carbon layer is transformed into a multilayer graphene.
"This research shows that the laser material interaction technology can be a powerful tool for the next generation of two dimensional nanomaterials," said Professor Lee.
Professor Choi added: "Using laser-induced phase separation of complex compounds, new types of two dimensional materials can be synthesized in the future."
High-resolution transmission electron microscopy shows that after just one laser pulse of 30 nanoseconds, the silicon carbide (SiC) substrate is melted and separates into a carbon and a silicon layer. More pulses cause the carbon layer to organize into graphene and the silicon to leave as gas.
Molecular dynamics simulates the graphene formation mechanism. The carbon layer on the top forms because the laser-induced liquid SiC (SiC (l)) is unstable.
(Press Release by Courtesy of the Institute for Basic Science (IBS))
2016.12.01 View 9990 -
Aerospace Engineering Students Win the Minister's Award
On November 11, 2016, students from KAIST’s Aerospace Engineering Department won the Minister’s Award of Trade, Industry and Energy of Korea at the 14th Research Paper Competition hosted by Korea Aerospace Industries (KAI). The award came with a cash prize of USD 1,200 as well as opportunities to visit international airshows held abroad.
The KAIST students' paper introduced a novel design concept for "a virtual-fighter-pilot system for unmanned combat aerial vehicles to enable them to engage in mass aerial combat."
This was one of the two highest honors given to contestants. A group of students from Korea Aerospace University received the other grand prize from the Minister of Land, Infrastructure and Transport of Korea.
The KAIST team consisted of two doctoral students, Hee-Min Shin and Jae-Hyun Lee, and one Master’s student, Hyun-Gi Kim. Their advisor, Professor “David” Hyunchul Shim, received the Special Achievement Award for his contribution to the paper.
KAI’s competition was established in 2003 to spur academic interest and research in aerospace engineering. Over the past 14 years, contestants have submitted 376 papers, and KAI has published 88 papers. KAI has positioned itself as the host of one of the most prestigious research paper competitions held in Korea in the area of aerospace engineering.
The Korean Society for Aeronautical and Space Sciences, the Korea Aerospace Industries Association, and the Korea Civil Aviation Development Association also sponsored the competition, with the Ministries of Trade, Industry and Energy and of Land, Infrastructure and Transport.
Professor Shim said, “This represents a great honor for our students. In recent years, research in unmanned aerial systems has increased tremendously throughout the world, and I hope KAIST will continue to inspire and innovate research in this field.”
Pictured from left to right are Hee-Min Shin, Jae-Hyun Lee, and Hyun-Gi Kim.
Pictured from right to left are Professor Hyunchul Shim, Hyun-Gi Kim, Hee-Min Shin, and Vice President Sung-Sup Chang of Korea Aerospace Industries.
2016.11.22 View 9963 -
KAIST's Doctoral Student Receives a Hoffman Scholarship Award
Hyo-Sun Lee, a doctoral student at the Graduate School of EEWS (Environment, Energy, Water and Sustainability), KAIST, is a recipient of the 2016 Dorothy M. and Earl S. Hoffman Scholarships presented by the American Vacuum Society (AVS). The award ceremony took place during the Society’s 63rd International Symposium and Exhibition on November 6-11, 2016 in Nashville, Tennessee.
Lee is the first Korean and foreign student to receive this scholarship.
The Hoffman Scholarships were established in 2002 to recognize and encourage excellence in graduate studies in the sciences and technologies of interest to AVS. The scholarships are funded by a bequest from Dorothy M. Hoffman, who was a pioneering member of the Society of Women Engineers and served as the president of AVS in 1974.
Lee received the scholarship for her research that detects hot electrons from chemical reactions on catalytic surface using nanodevices. Nano Letters, an academic journal published by the American Chemical Society, described her work in its February 2016 issue as a technology that allows quantitative analysis of hot electrons by employing a new nanodevice and therefore helps researchers understand better the mechanism of chemical reactions on nanocatalytic surface. She also published her work to detect the flow of hot electrons that occur on metal nanocatalytic surface during hydrogen oxidation reactions in Angewandte Chemie.
Lee said, “I am pleased to receive this honor from such a world-renowned academic society. Certainly, this will be a great support for my future study and research.”
Founded in 1953, AVS is an interdisciplinary, professional society composed of approximately 4,500 members worldwide. It supports networking among academic, industrial, government, and consulting professionals involved in a range of established and emerging science and technology areas such as chemistry, physics, engineering, business, and technology development.
2016.11.17 View 8161 -
Key Interaction between the Circadian Clock and Cancer Identified
Professor Jae Kyoung Kim and his research team from the Department of Mathematical Sciences at KAIST found that the circadian clock drives changes in circadian rhythms of p53 which functions as a tumor suppressor. Using a differential equation, he applied a model-driven mathematical approach to learn the mechanism and role of p53.
Kim’s mathematical modeling has been validated by experimental studies conducted by a research team at Virginia Polytechnic Institute and State University (Virginia Tech) in the United State, which is led by Professor Carla Finkielstein. As a result, the researchers revealed that there is an important link existed between the circadian clock and cancer.
The findings of this research were published online in Proceedings of the National Academy of Sciences of the United States of the America (PNAS) on November 9, 2016.
The circadian clock in our brain controls behavioral and physiological processes within a period of 24 hours, including making us fall asleep at a certain time by triggering the release of the sleep hormone melatonin in our brain, for example, around 9 pm. The clock is also involved in various physiological processes such as cell division, movement, and development.
Disruptions caused by the mismatch of the circadian clock and real time due to chronic late night work, shiftwork, and other similar issues may lead to various diseases such as diabetes, cancer, and heart disease.
In 2014, when Kim met with Finkielstein, her research team succeeded in observing the changes of p53 over a period of 24 hours, but could not understand how the circadian clock controls the 24-hour rhythm of p53. It was difficult to determine p53’s mechanism since its cell regulation system is far more complex than other cells
To solve the problem, Kim set up a computer simulation using mathematical modeling and ran millions of simulations. Instead of the traditional method based on trial and error experiments, mathematical modeling allowed to save a great deal of time, cost, and manpower.
During this process, Kim proved that the biorhythm of p53 and Period2, an important protein in the circadian clock, are closely related. Cells usually consist of a cell nucleus and cytoplasm. While p53 exists in both nucleus and cytoplasm, it becomes more stable and its degradation slows down when it is in the nucleus.
Kim predicted that the Period2 protein, which plays a key role in the functioning of the circadian clock, could influence the nucleus entry of the p53 protein.
Kim’s predictions based on mathematical modeling have been validated by the Virginia team, thereby revealing a strong connection between the circadian clock and cancer.
Researchers said that this research will help explain the cause of different results from numerous anticancer drugs, which are used to normalize the level of p53, when they are administrated at different times and find the most effective dosing times for the drugs.
They also believe that this study will play an important role in identifying the cause of increasing cancer rates in shift-workers whose circadian clocks are unstable and will contribute to the development of more effective treatments for cancer.
Professor Kim said, “This is an exciting thing that my research can contribute to improving the healthy lives of nurses, police officers, firefighters, and the like, who work in shifts against their circadian rhythms. Taking these findings as an opportunity, I hope to see more active interchanges of ideas between biological sciences and mathematical science in Korea.”
This research has been jointly conducted between KAIST and Virginia Tech and supported by the T. J. Park Science Fellowship of POSCO, the National Science Foundation of the United States, and the Young Researcher Program of the National Research Foundation of Korea.
Picture 1. The complex interaction between tumor antigen p53 and Period2 (Per2) which plays a major role in the circadian clock as revealed by mathematical simulations and experiments
Picture 2. A portion of the mathematical model used in the research
Picture 3. Professor Jae Kyoung Kim (third from left) and the Virginia Tech Research Team
2016.11.17 View 7006 -
Professor Lee Co-chairs the Global Future Councils on Biotechnology of the WEF
The World Economic Forum (WEF) established a new global network of the world’s leading experts, “The Annual Meeting of the Global Future Councils,” to explore innovative solutions for the most pressing global challenges. The Councils’ first meeting took place on November 13-14, 2016, in Dubai, the United Arab Emirates (UAE). Some 25 nations joined as member states. The Councils have 35 committees.
Over 700 global leaders in business, government, civil society and academia gathered at the inaugural meeting to “develop ideas and strategies to prepare the world for the Fourth Industrial Revolution, with topics including smart cities, robotics, and the future of mobility,” according to a statement issued by the WEF.
Distinguished Professor Sang Yup Lee of Chemical and Biomolecular Engineering at KAIST was appointed to co-chair one of the Councils' committees, The Annual Meeting of the Global Future Councils on Biotechnology, for two years. The other chairperson is Dr. Feng Zhang, a professor of Biomedical Engineering at the Massachusetts Institute of Technology (MIT), who played a critical role in the development of optogenetics and CRISPR technologies.
The Biotechnology Committee consists of 24 globally recognized professionals in life sciences, law, ethics and policy including Thomas Connelly, the executive director of the American Chemical Society, Tina Fano, the executive vice president of Novozymes, and Mostafa Ronaghi, the chief technology officer of Illumina.
Professor Lee also serves as a committee member of The Annual Meeting of the Global Future Councils on the Fourth Industrial Revolution.
“Life sciences and engineering will receive more attention as a key element of the Fourth Industrial Revolution that the global society as a whole has been experiencing now. Together with thought leaders gathered worldwide, I will join the international community’s concerted efforts to address issues of importance that impact greatly on the future of humanity,” Professor Lee said.
In addition, Professor Lee received the James E. Bailey Award 2016 from The Society for Biological Engineering on November 15, 2016. He is the first Asian researcher to be recognized for his contributions to the field of biotechnology.
2016.11.15 View 8072 -
Robot Drone Man: A
Research Professor Ilhan Bae of the Moon Soul Graduate School of Future Strategy at KAIST created a life-size humanoid robot on a drone platform, which gives users the experience of virtual flight and an opportunity to interact with people at remote locations. Professor Bae calls his new creation a "telepresence robot."
This avatar drone is a new application of drone and robotics technology, which extends the reach of human presence and mobility, Professor Bae explained his research.
“As a futurist, I forecast that drone technology will soon evolve to become another body for humans, and I wanted to demonstrate this potential application of drones. Avatar drones are especially useful for people who need to meet or manage other people face to face in remote locations,” he said.
For example, if elderly people with physical disabilities want to engage in social gatherings, this avatar drone is designed to help them do just that.
For more details, please see the link below:
Behind the Music: How Robot Drone Man Built His Flying Avatar
IEEE Spectrum, November 7, 2016
2016.11.08 View 6024 -
Technology to Allow Non-Magnetic Materials to Have Magnetic Properties by Professor Chan-Ho Yang
Professor Chan-Ho Yang and his research team from the Department of Physics at KAIST have developed a technology that allows non-magnetic materials to have magnetic properties or, in reverse, to remove magnetic properties from a magnet using an electric field.
Based on this research, it is expected that if magnetic-material-based data storage is developed, applications for high-speed massive data transfer will be possible.
The results of this research, with Ph.D. candidate Byung-Kwon Jang as the first author, were published online in Nature Physics on October 3.
Very small magnets exist inside of any materials. If the direction of the minuscule magnets is dis-aligned, pointing multiple directions, it is non-magnetic. If the direction is aligned in a certain direction, the material holds magnetic property just like any magnet we normally see.
Data storage capacity technology has rapidly advanced to the point where we can easily get a portable hard disk drive (HDD) with terabyte-level storage; however, the increase in storage is inevitably followed by slower data access speed for a storage device. Although HDDs are currently the most widely used data storage devices, their technical applications are limited due to their slow data access speed.
Other methods such as solid-state drives (SSDs), floating gates, and resistive switching have been developed as alternatives. Yet, they leave tracks every time data is written, and this can cause fatigue cumulative damage.
There have been many attempts to compose cells—the smallest data storage space on a storage device—with magnetic materials as that would enable faster data access speeds and remove fatigue cumulative damage. Generally, the techniques tried by researchers were to use induced magnetic fields through current flow. However, magnetic fields are very difficult to shield and can affect a large area. As a result, they alternate the magnetic property of adjacent cells. Because each cell cannot be adjusted one by one, it cannot also be arranged in a certain direction, and therefore, it is hard to change the magnetic state.
Professor Yang and his team adjusted the magnetic state by using magnetoelectric interaction to deal with this issue. Instead of using magnetic fields, magnetoelectric interaction is a method that uses an electric field to adjust the magnetic state. It has the advantage of smaller energy consumption as well.
Professor Yang's team demonstrated that cells facing random directions can be arranged in a certain direction by only inducing an electric field. In addition, the reverse was also proved to be feasible.
Until this research, most cases of previous findings were only feasible at extremely low temperatures or high temperatures, but the technology developed by the research team is practicable at room temperature by manipulating chemical pressure. It allows for a reversible magnetic state, and moreover, is non-volatile. Therefore, the results of this research are expected to provide the basis for developing next-generation information storage device.
Professor Yang said, “The changes in the electric magnetic state will be accompanied by entropy changes” and added, “Our research is expected to open new potential for future applications not only for magnetoelectric devices, but also for thermoelectric effect.”
This research has been worked on jointly with Dr. Si-Yong Choi from the Korea Institute of Materials Science, Prof. Yoon-Hee Jeong from the Pohang University of Science and Technology, Dr. Tae-Yeong Koo from the Pohang Accelerator Laboratory, Dr. Kyung-Tae Ko from the Max Planck Institute for Chemical Physics of Solids, Dr. Jun-Sik Lee and Dr. Hendrik Ohldag from the SLAC National Accelerator Laboratory of the United States, and Prof. Jan Seidel from the University of New South Wales of Australia.
The research was supported by the Mid-Career Researcher Program of the National Research Foundation of Korea, Global Research Network Support Project, Leading Research Center Support Project (Condensed Quantum Coherence Research Center), Global Frontier Project (Hybrid Interface Materials Research Group), and others.
Picture: The concept graphic for the electric-field-induced magnetic phase switching the magnetic direction
2016.11.04 View 7291 -
MOU between KAIST and DTU Signed
KAIST and the Technical University of Denmark (DTU) signed a memorandum of understanding (MOU) to cooperate in the areas of startup, student exchange, and joint research on October 25, 2016 at the Embassy of Denmark in Seoul, Korea. Under the agreement, KAIST and DTU will exchange students and researchers through startup programs and continue to collaborating in education and research.
The MOU was facilitated during the Green Growth Alliance Meeting and Energy Seminar hosted by the Danish embassy, in which Danish Prime Minister Lars Løkke Rasmussen participated.
President Steve Kang of KAIST, who fostered the agreement, said,
“DTU has been one of our strategic partners in Europe. We have been working closely with them on academic exchanges and research collaborations, but now with the expansion of our cooperation into entrepreneurship, we will create momentum to spur startups in both schools. To support such activities, we will use KAIST’s experiences acquired from operating the K-School, an entrepreneurship graduate school, and the Institute of KAIST Entrepreneurship. DTU will also share their knowledge on startup programs including SkyLab and StartDTU. I believe this will become another successful alliance between the two universities.”
As of October 2016, KAIST has made 18 agreements with DTU, exchanging 120 students in the past three years and implementing various joint seminars and conferences for academic and research exchanges.
Established in 1829, DTU has been a leading science and technology university in Denmark. It ranked 109 in the QS World University Rankings 2016 and 46th in its subject rankings in engineering and technology.
In the picture below, President Steve Kang of KAIST (right) and Senior Vice President Martin P. Bendsøe of the Technical University of Denmark (left) are signing an agreement for academic and research cooperation.
2016.10.27 View 7293 -
Professor Shin's Team Receives the Best Software Defined Network Solution Showcase Award
Professor Seungwon Shin of the Electrical Engineering School at KAIST and his research team won the Best Software Defined Networking (SDN) Solution Showcase Award hosted by the SDN World Congress, one of the biggest network summits held in Europe with over 2,000 participants. This year the conference took place in The Hague, the Netherlands, October 10-14, 2016.
SDN is an approach to computer networking that allows network administrators to respond quickly to changing business requirements via a centralized control console and to support the dynamic, scalable computing and storage needs of more modern computing environments such as data centers.
Collaborating with researchers from Queen’s University in the United Kingdom and Huawei, a global information and communications technology solutions provider in China, Professor Shin’s team, which is led by doctoral students Seungsoo Lee, Changhoon Yoon, and Jaehyun Nam, implemented a SDN security project called “DELTA.” ATTORESEARCH, a Korean SDN architecture and applications provider, conducted testing and verification for the project.
DELTA is a new SDN security evaluation framework with two main functions. It can automatically recognize attack cases against SDN elements across diverse environments and can assist in identifying unknown security problems within a SDN deployment.
The DELTA project consists of a control plane, the part of a network that carries signaling traffic and is responsible for routing; a data plane, the part of a network that carries user traffic; and a control channel that connects the two aforementioned planes. These three components have their own agents installed, which are all controlled by an agent manger. The agent manger can automatically detect any spots where the network security is weak.
Specifically, the project aimes to defense attacks against OpenFlow protocol, one of the first SDN standards; SDN controllers, a network operating system that is based on protocols; and network switch devices that use OpenFlow protocol.
The DELTA project was registered with the Open Networking Foundation, a user-driven organization dedicated to the promotion and adoption of SDN through open standards development, as an open source SDN security evaluation tool. This project is the only open source SDN which has been led by Korean researchers.
The SDN World Congress 2016 recognized the need for and importance of the DELTA project by conferring upon it the Best Solution Showcase Award. The Open Networking Foundation also widely publicized this award news.
Professor Shin said:
“In recent years, SDN has been attracting a large amount of interest as an emerging technology, but there still have not many SDN projects in Korea. This award acknowledges the advancement of Korean SDN technology, showing the potential for Korea to become a leader in SDN research.”
Picture: Major Components of the DELTA Project: Agents and Agent Manger
2016.10.25 View 7715 -
KAIST and the Budapest University of Technology and Economics Agree to Cooperate in Education and Research
KAIST and the Budapest University of Technology and Economics in Hungary extended their existing agreement for comprehensive cooperation in education and research, and signed a new memorandum of understanding (MOU) for student exchanges on October 19, 2016, at Budapest University.
The two universities will exchange faculty, researchers, and students for education and research collaboration, implement dual degree programs, conduct joint lectures and research projects, and share infrastructures and talent pools.
These agreements were part of the agenda for the 8th Meeting of the Korea and Hungary Science and Technology Joint Committee, which took place October 17-19, 2016, in Budapest.
President Sung-Mo Kang of KAIST, Associate Vice President Sung-Hyon Myaeng of the International Office, and Director General Won-Ho Choi of International Relations at the Ministry of Science, ICT and Future Planning of Korea were present at the MOU singing.
Associate Vice President Myaeng said:
“Traditionally, the Budapest University of Technology and Economics has been known for its strong base in the natural sciences. Combining this with KAIST’s excellence in engineering, the two universities will bring synergistic effects that will help further develop the schools as well as their host nations.”
“Finding partners to implement joint research projects sponsored by the European Union or establishing cooperative networks among future talents between the two countries through various student exchange programs can be a good starting point,” he added.
The Budapest University of Technology and Economics was created in 1782, and is one of the most prestigious universities in Hungary, having produced three Nobel Prize laureates. It has a highly-globalized campus, where one third of its student population is made up of international students, and offers lectures and research in English.
In addition, the Hungarian-Korean Technical Cooperation Center Foundation, established in 1992 and based in Budapest, hosted a seminar on science in Korea and Hungary on October 17, 2016. At the seminar, Korean and Hungarian participants discussed issues on the two nations’ science, technology, and strategies to drive innovation under the topic “The Technical Innovation-Importance of Startup Companies.”
Associate Vice President Sung-Hyon Myaeng of the International Office, KAIST, is pictured fourth from the left, and János Józsa, rector of the Budapest University of Technology and Economics, is fifth from the left.
2016.10.20 View 7512 -
2016 KAIST EEWS Workshop
The Energy, Environment, Water and Sustainability (EEWS) Graduate School of KAIST hosted a workshop entitled “Progress and Perspectives of Energy Science and Technology” on October 20, 2016. The workshop took place at the Fusion Hall of the KAIST Institute on campus.
About 400 experts in energy science and engineering participated in the event. Eight globally recognized scientists introduced the latest research trends in nanomaterials, energy theory, catalysts, and photocatalysts and led discussions on the current status and prospects of EEWS.
Professors Yi Cui of Stanford University, an expert in nanomaterials, and William A. Goddard of California Institute of Technology presented their research experiments on materials design and recent results on the direction of theory under the topics of energy and environment.
Dr. Miquel Salmeron, a former head of the Material Science Division of Lawrence Berkeley National Laboratory, and Professor Yuichi Ikuhara of Tokyo University introduced their analysis of catalysts and energy matters at an atomic scale.
Professor Sukbok Chang of the Chemistry Department at KAIST, a deputy editor of ACS Catalysis and the head of the Center for Catalytic Hydrocarbon Functionalizations at the Institute of Basic Science, and Professor Yang-Kook Sun of Energy Engineering at Hanyang University, who is also a deputy editor of ACS Energy Letters, presented their latest research results on new catalytic reaction development and energy storage.
The workshop consisted of three sections which addressed the design of energy and environment materials; analysis of energy and catalytic materials; and energy conversion and catalysts.
The EEWS Graduate School was established in 2008 with the sponsorship of the Korean government’s World Class University (WCU) project to support science education in Korea. Professor J. Fraser Stoddart, the winner of the 2016 Nobel Prize in Chemistry, was previously worked at the KAIST EEWS Graduate School as a WCU visiting professor for two years, from 2011 to 2013. Professor Ali Coskun, who was a postdoctoral researcher in the laboratory of Professor Stoddart, now teaches and conducts research as a full-time professor at the graduate school.
Dean Yousung Jung of the EEWS Graduate School said:
“This workshop has provided us with a meaningful opportunity to engage in discussions on energy science and technology with world-class scholars from all around the world. It is also a good venue for our graduate school to share with them what we have been doing in research and education.”
2016.10.20 View 10878 -
KAIST Signs an Agreement with CSC for Cooperation
KAIST and the China Scholarship Council (CSC) established a memorandum of understanding (MOU) to support the admission of Chinese students to KAIST on October 5, 2016 in Seoul. KAIST is the only institution in Korea made such agreement with the CSC.
Affiliated with the Ministry of Education of China, the CSC is a non-profit institution that provides financial assistance to Chinese students to study abroad and to internationals wishing to study in China. The CSC has supported 500,000 Chinese students for their studying and living in a foreign country, and this year alone, it provided outbound Chinese students with scholarships of approximately USD 100 million.
Under the MOU, Chinese students admitted to KAIST’s master’s and doctoral programs will receive finical support from CSC, including monthly stipends and roundtrip airfare from China to Korea.
President Sung-Mo Kang of KAIST said, “This is a great opportunity for us because we can invite more outstanding Chinese students. They will make our campus more diverse and global, while their academic experiences will become richer with KAIST’s offerings in education and research. I hope many Chinese students will capitalize on this chance to come to KAIST for their advanced degrees in science and technology.”
In the picture below, President Steve Kang of KAIST, on the right, is pictured with Secretary General Liu Jinghui of China Scholarship Council.
2016.10.19 View 6330