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KAIST Unveils the Hidden Control Architecture of Brain Networks
(Professor Kwang-Hyun Cho and his team) A KAIST research team identified the intrinsic control architecture of brain networks. The control properties will contribute to providing a fundamental basis for the exogenous control of brain networks and, therefore, has broad implications in cognitive and clinical neuroscience. Although efficiency and robustness are often regarded as having a trade-off relationship, the human brain usually exhibits both attributes when it performs complex cognitive functions. Such optimality must be rooted in a specific coordinated control of interconnected brain regions, but the understanding of the intrinsic control architecture of brain networks is lacking. Professor Kwang-Hyun Cho from the Department of Bio and Brain Engineering and his team investigated the intrinsic control architecture of brain networks. They employed an interdisciplinary approach that spans connectomics, neuroscience, control engineering, network science, and systems biology to examine the structural brain networks of various species and compared them with the control architecture of other biological networks, as well as man-made ones, such as social, infrastructural and technological networks. In particular, the team reconstructed the structural brain networks of 100 healthy human adults by performing brain parcellation and tractography with structural and diffusion imaging data obtained from the Human Connectome Project database of the US National Institutes of Health. The team developed a framework for analyzing the control architecture of brain networks based on the minimum dominating set (MDSet), which refers to a minimal subset of nodes (MD-nodes) that control the remaining nodes with a one-step direct interaction. MD-nodes play a crucial role in various complex networks including biomolecular networks, but they have not been investigated in brain networks. By exploring and comparing the structural principles underlying the composition of MDSets of various complex networks, the team delineated their distinct control architectures. Interestingly, the team found that the proportion of MDSets in brain networks is remarkably small compared to those of other complex networks. This finding implies that brain networks may have been optimized for minimizing the cost required for controlling networks. Furthermore, the team found that the MDSets of brain networks are not solely determined by the degree of nodes, but rather strategically placed to form a particular control architecture. Consequently, the team revealed the hidden control architecture of brain networks, namely, the distributed and overlapping control architecture that is distinct from other complex networks. The team found that such a particular control architecture brings about robustness against targeted attacks (i.e., preferential attacks on high-degree nodes) which might be a fundamental basis of robust brain functions against preferential damage of high-degree nodes (i.e., brain regions). Moreover, the team found that the particular control architecture of brain networks also enables high efficiency in switching from one network state, defined by a set of node activities, to another – a capability that is crucial for traversing diverse cognitive states. Professor Cho said, “This study is the first attempt to make a quantitative comparison between brain networks and other real-world complex networks. Understanding of intrinsic control architecture underlying brain networks may enable the development of optimal interventions for therapeutic purposes or cognitive enhancement.” This research, led by Byeongwook Lee, Uiryong Kang and Hongjun Chang, was published in iScience (10.1016/j.isci.2019.02.017) on March 29, 2019. Figure 1. Schematic of identification of control architecture of brain networks. Figure 2. Identified control architectures of brain networks and other real-world complex networks.
2019.04.23
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KAIST-KU Joint Research Center for Smart Healthcare & Transportation
(President Shin shakes hands with KU acting Presidedent Arif Al Hammdi at the KAIST-KU Joint Research Center opening ceremony on April 8.) KAIST opened the KAIST-Khalifa University Joint Research Center with Khalifa University on April 8. The opening ceremony was held at Khalifa University and was attended by President Sung-Chul Shin and Khalifa University Acting President Arif Al Hammadi. The new research center reflects the evolution of the long-established partnership between the two institutions. The two universities have already made very close collaborations in research and education in the fields of nuclear and quantum engineering. The launch of this center expanded their fields of collaboration to smart healthcare and smart transportation, key emerging sectors in the Fourth Industrial Revolution. President Shin signed an MOU with the UAE Minister of State for Advanced Science Sarah Amiri and Khalifa University to expand mutual collaboration in technology development and fostering human capital last year. The center will conduct research and education on autonomous vehicles, infrastructure for autonomous vehicle operation, wireless charging for electric vehicles, and infrastructure for electric autonomous vehicles. As for smart healthcare, the center will focus on healthcare robotics as well as sensors and wearable devices for personal healthcare services. President Shin, who accompanied a research team from the Graduate School of Green Transportation, said, “We are very delighted to enter into this expanded collaboration with KU. This partnership justifies our long-standing collaboration in the areas of emerging technologies in the Fourth Industrial Revolution while fostering human capital.” KU Acting President Arif Al Hammadi added, “The outcome of these research projects will establish the status of both institutions as champions of the Fourth Industrial Revolution, bringing benefits to our communities. We believe the new research center will further consolidate our status as a globally active, research-intensive academic institution, developing international collaborations that benefit the community in general.”
2019.04.09
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Distinguished Alumni Awardees 2018
The KAIST Alumni Association (KAA) announced four recipients of the Distinguished Alumni Awards 2018. The Distinguished Alumni Awards recognize graduates who have achieved outstanding accomplishments in their professional and personal lives, and who have been an inspiration to fellow alumni and students in Korea and around the globe. Since the establishment of the award in 1992, a total of 99 alumni at home and abroad have been honored as recipients. The awards ceremony will take place during the New Year Alumni Reception on January 19 in Seoul. Yeungnam University President Gil-Soo Sur (’75 MS, ’78 PhD in Chemistry) has demonstrated leadership in higher education and gained trust in academia for playing a leading role in educational innovation as well as serving as an educator who has fostered outstanding research talents for decades. Professor Kwang-Soo Kim (’77 MS, ’79 PhD in Life Science) is the director of the Molecular Neurobiology Laboratory at McLean Hospital at Harvard Medical School. He has more than 20 years of experience investigating molecular and developmental neurobiology of the midbrain dopamine neuronal system. He has contributed to developing cell replacement therapy for Parkinson’s disease and has pioneered a generation of safe human-induced pluripotent stem cells through the direct delivery of reprogrammed proteins. Young-Hwan Moon (’82 MS, ’87 PhD in Chemistry and Biomolecular Engineering) is the CEO of Coretech, which specializes in producing specialty gases and environmental catalysts required for chemical processes. He was recognized for enhancing national competence by securing competitive technology for manufacturing products. Young-Hyun Jun (’84 MS, ’86 PhD in Electrical Engineering), the CEO of Samsung SDI, is a globally renowned expert in memory semiconductors. By bringing about innovative technology to enhance productivity and processes, he led Samsung Electronics to become the number one company at the global level in the field of semiconductors.
2019.01.14
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Ultrathin Digital Camera Inspired by Xenos Peckii Eyes
(Professor Ki-Hun Jeong from the Department of Bio and Brain Engineering) The visual system of Xenos peckii, an endoparasite of paper wasps, demonstrates distinct benefits for high sensitivity and high resolution, differing from the compound eyes of most insects. Taking their unique features, a KAIST team developed an ultrathin digital camera that emulates the unique eyes of Xenos peckii. The ultrathin digital camera offers a wide field of view and high resolution in a slimmer body compared to existing imaging systems. It is expected to support various applications, such as monitoring equipment, medical imaging devices, and mobile imaging systems. Professor Ki-Hun Jeong from the Department of Bio and Brain Engineering and his team are known for mimicking biological visual organs. The team’s past research includes an LED lens based on the abdominal segments of fireflies and biologically inspired anti-reflective structures. Recently, the demand for ultrathin digital cameras has increased, due to the miniaturization of electronic and optical devices. However, most camera modules use multiple lenses along the optical axis to compensate for optical aberrations, resulting in a larger volume as well as a thicker total track length of digital cameras. Resolution and sensitivity would be compromised if these modules were to be simply reduced in size and thickness. To address this issue, the team have developed micro-optical components, inspired from the visual system of Xenos peckii, and combined them with a CMOS (complementary metal oxide semiconductor) image sensor to achieve an ultrathin digital camera. This new camera, measuring less than 2mm in thickness, emulates the eyes of Xenos peckii by using dozens of microprism arrays and microlens arrays. A microprism and microlens pair form a channel and the light-absorbing medium between the channels reduces optical crosstalk. Each channel captures the partial image at slightly different orientation, and the retrieved partial images are combined into a single image, thereby ensuring a wide field of view and high resolution. Professor Jeong said, “We have proposed a novel method of fabricating an ultrathin camera. As the first insect-inspired, ultrathin camera that integrates a microcamera on a conventional CMOS image sensor array, our study will have a significant impact in optics and related fields.” This research, led by PhD candidates Dongmin Keum and Kyung-Won Jang, was published in Light: Science & Applications on October 24, 2018. Figure 1. Natural Xenos peckii eye and the biological inspiration for the ultrathin digital camera (Light: Science & Applications 2018) Figure 2. Optical images captured by the bioinspired ultrathin digital camera (Light: Science & Applications 2018)
2018.12.31
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Vietnamese Alumni of Korean S&T Universities Gather in Hanoi
(Vietnamese KAIST alumni gather in Hanoi on November 24.) (Dr.Huong Minh Nguyen at the Institute of Biotechnology in the Vietnam Academy of Science and Technology (VAST). She is the representative of Vietnamese KAIST alumni.) Some came from Ho Chi Minh and some even flew in from Singapore. For those KAIST alumni who gathered in Hanoi, the trip was well worth it. More than 100 Vietnamese alumni of KAIST, GIST, and UST attended the reunion in Hanoi on November 24. Presidents and vice president from three universities welcomed them and celebrated their successful careers after returning home or starting careers in other countries. The reunion was co-hosted by KAIST, UST, and GIST in an effort to make a platform for continued networking for scientists who have studied at Korea’s science and technology universities. This joint reunion will be expected to include other science and technology universities and institutes in the future. Among 1,873 international KAIST alumni from 106 countries, the number of Vietnamese graduates is the most dominant with 262 alumni, 14% of the total international alumni. Welcoming them, KAIST Vice President Soohyun Kim said that he was very impressed that all of the alumni are making a very impressive stride in their fields. “You will be a big asset to make your country grow. You will also be a bridge for future collaborations with your institutions and KAIST and Korea. Vietnam holds great potential for future prosperity especially in science and technology and we look forward to seeing this network continue to benefit both countries.” Vice President Kim said all of the presidents shared the idea to make this gathering a regular event. “Other S&T universities will join to hold joint reunions in other countries in the future,” he added. Dr. Huong Minh Nguyen at the Institute of Biotechnology in the Vietnam Academy of Science and Technology (VAST) is one of 22 KAIST alumni who joined the reunion and supported the idea. She is also the representative of Vietnamese KAIST alumni. Dr. Nguyen, who earned her MS and PhD in the Department of Biological Sciences in 2013, spent five and half years at KAIST. “All the members at the lab were taking care of each other. When I joined the lab back then, they treated me as a ‘baby sister’ in a family and our relationship grew like a sister and brotherhood. I still appreciate the bonding relationship we could make with our colleagues.” She cites a supporting culture, a competent educational system that places a focus on practicality, and rich resources that help researchers try whatever they want as the distinct advantages of a KAIST education. “I never heard my professor saying “No” to any of my suggestions in conducting research. Professors and lab members put all their efforts, resources, and facilities to getting my research started. They helped me obtain all the resources that I needed. It was a huge encouragement to me,” she added. She started her Masters, along with four Vietnamese colleagues, right after graduating from the Hanoi University of Natural Sciences, a top science university in Vietnam. Their experience at KAIST during a 4-week exchange program during undergraduates made them decide their academic destination without any doubt. All of them finished their PhDs in 2013. Two of them moved back home and the two others are now in the US and Germany as postdoctoral fellows. “At that time, I could go to other countries for my further studies. But I already experienced KAIST for a month when I was an undergraduate, so I was not hesitant to go to KAIST. All of the classes are in English so, for students who do not speak in Korean, language does not bring any problems in studying and conducting research.” She said that KAIST alumni are enjoying very successful careers in Vietnam and many foreign countries. “We do not have any problems choosing our careers back home and other countries we wanted to work in.” However, like many PhD candidates who feel pressure about their studies and an uncertain future, her days at KAIST also included challenging times while adjusting to Korean culture. She took Korean classes for three semesters voluntarily at the KAIST Language Center to better understand Korea and her lab members. Her efforts paid off well. She could easily communicate with her colleagues and felt she became a real part of the inner group. But the stress remained to prove herself in research and she still had to deal with some bias. “I know some people think Vietnam is behind Korea. Many people think that we are not as good as Korean students because we are from Vietnam. I desperately wanted to prove that I am as good as my peers.” Studying together with Korean and other international PhD candidates, she realized that everyone has their own purposes and pressures. “Even though there are minor differences, every PhD candidate has the same issues with their uncertain futures. It was quite comforting when we shared that it’s not only my problem. To understand that it’s a problem we all share comforts us a lot and we came to support each other. To better help students release such pressure and stress, she said the university needs to create more diverse institutional channels to communicate with them. “Looking back, I was younger and less competent to speak up about when we were stressed and needed to ask for help. I hope students can begin to release their pressure and stress through diverse channels and resolve the problems,” she said. Asked about her future plans, she replied, “I don’t think I can do anything better than what I am doing now. I enjoy what I am doing now at my institute. But in the near very future, I want to visit Korea and KAIST again.”
2018.11.27
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Faster and More Powerful Aqueous Hybrid Capacitor
(Professor Jeung Ku Kang from the Graduate School of EEWS) A KAIST research team made it one step closer to realizing safe energy storage with high energy density, high power density, and a longer cycle life. This hybrid storage alternative shows power density 100 times faster than conventional batteries, allowing it to be charged within a few seconds. Hence, it is suitable for small portable electronic devices. Conventional electrochemical energy storage systems, including lithium-ion batteries (LIBs), have a high voltage range and energy density, but are subject to safety issues raised by flammable organic electrolytes, which are used to ensure the beneficial properties. Additionally, they suffer from slow electrochemical reaction rates, which lead to a poor charging rate and low power density with a capacity that fades quickly, resulting in a short cycle life. On the other hand, capacitors based on aqueous electrolytes are receiving a great deal of attention because they are considered to be safe and environmentally friendly alternatives. However, aqueous electrolytes lag behind energy storage systems based on organic electrolytes in terms of energy density due to their limited voltage range and low capacitance. Hence, developing aqueous energy storage with high energy density and a long cycle life in addition to the high power density that enables fast charging is the most challenging task for advancing next-generation electrochemical energy storage devices. Here, Professor Jeung Ku Kang from the Graduate School of Energy, Environment, Water and Sustainability and his team developed an aqueous hybrid capacitor (AHC) that boasts high energy density, high power, and excellent cycle stability by synthesizing two types of porous metal oxide nanoclusters on graphene to create positive and negative electrodes for AHCs. The porous metal oxide nanoparticles are composed of nanoclusters as small as two to three nanometers and have mesopores that are smaller than five nanometers. In these porous structures, ions can be rapidly transferred to the material surfaces and a large number of ions can be stored inside the metal oxide particles very quickly due to their small particle size and large surface area. The team applied porous manganese oxide on graphene for positive electrodes and porous iron oxide on graphene for negative electrodes to design an aqueous hybrid capacitor that can operate at an extended voltage range of 2V. Professor Kang said, “This newly developed AHC with high capacity and power density driven from porous metal oxide electrodes will contribute to commercializing a new type of energy storage system. This technology allows ultra-fast charging within several seconds, making it suitable as a power source for mobile devices or electric vehicles where solar energy is directly stored as electricity.” This research, co-led by Professor Hyung Mo Jeong from Kangwon National University, was published in Advanced Functional Materials on August 15, 2018. Figure 1. Image that shows properties of porous metal oxide nanoparticles formed on graphene in the aqueous hybrid capacitor
2018.11.09
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KAIST Thanks Supporters for Building KAIST of Today
KAIST hosted its first Fundraising Gala on October 26, 2018. It was organized to demonstrate deep gratitude to those who have made contributions to KAIST, making it possible to progress every year. The KAIST Development Foundation (KDF) endeavored to make a meaningful and inclusive event by collecting archives that show the history of donations while sending invitatio ns to all the members of KAIST, including donors and potential donors as well as professors and student representatives. Approximately 200 distinguished guests attended the gala, including major donors, Chairperson of KDF Soo Young Lee and Chairman Beang Ho Kim, Former Minister of Science Dr. Geun Mo Jung, Former Minister of Science and Technology Woo Sik Kim, and KAIST alumni including the first Korean astronaut So-Yeon Yi. (Student cheer leading club, ELKA) At the gala, KAIST shared its 47 years of funding and an expenditure summary with major performances achieved from the year it was founded. According to the summary, KAIST has received more than 323.1 billion won since 1971. The total number of donors was 12,906 while the number of contribution reached 77,710. Among the total funding (323.1 billion won), corporate gifts made up 43.1% of the total and individual gifts stood at 39.1%, showing that KAIST has received and is receiving support evenly from companies and individuals. Taking a close look at the major donors, there is an interesting fact about KAIST’s fundraising culture. There has been continuous support from individuals who did not have any personal or academic ties with KAIST before donating. However, they have made large gifts to KAIST so that the best students in the fields of science and technology can be fostered for the sake of national development. The major donors included Young Han Kim (1999), Moon Soul Chung (2001), Byiung Joon Park (2007), Keun Chul Ryu (2008), Beong Ho Kim (2009), Chun Shik Cho and E won Oh (2010), Soo Young Lee (2012), Tae-won Chey (2014), Jeong Ja Cho (2015), and Chang Kun Sohn (2017). Especially, M. S. Chung, B. H. Kim, C. S. Cho and S. Y. Lee made additional mega-gifts to KAIST, showing continuous support for KAIST’s development. Nevertheless, the KAIST fundraising culture could not be created with major donors only. Among the total number of donors (12,906), alumni showed the strong engagement standing at 40.4% while parents and students were at 26.1% and 12.7% respectively. The contribution numbers follow the order of alumni (34.8%), parents (20.3%), staff (20%), professors (13.3%), and students (5.7%). These statistics imply that individual’s constant donations play a significant part in the fundraising culture of KAIST. Additionally, engagement continues to rise every year, and it reached 12,039 gifts in 2017, which increased 5.7 times over ten years. (from left: Executive Director of KDF Young-gul Kim KAIST President Sung-Chul Shin) These valuable gifts are the vital fuel for KAIST’s progress. As of 2018, KAIST has spent 205.8 billion won: 81.9 billion won for construction and facilities operation, 79.7 billion won for academics and research, 39 billion won for academic management, and 5.2 billion won for scholarships. The construction and facilities operation fund aided the evolution of physical infrastructure. KAIST endowed the ChungMoonSoul Building for promoting convergence between information and biotechnology, the Yang Bun Soon Building for bio and brain engineering studies, and the Chunghi & Byiung Jun Park KI Building for multi and interdisciplinary research. Their generous gifts built the foundation for KAIST taking off towards becoming a global leading university. Meanwhile, the academic and research funds provided opportunities to professors and students to carry out creative research and academic missions. The academic management fund helped open new departments (i.e. The Cho Chun Shik Graduate School of Green Transportation and the Moon Soul Graduate School of Future Strategy) and their programs, for which their names came from the major donors. (The first Korean astronaut So-Yeon Yi) At the gala, special events were held for two exclusive moments that contributed to promoting and making a better image for KAIST to the public. One was the 10th anniversary of the space exploration of the first Korean astronaut Dr. Yi. The other was the 20th anniversary of the TV drama series, called ‘KAIST’ which was aired from 1999 to 2000. The writer and main casting crew members joined the event. They said that it was their first time to gather in one place after the show last aired and this event would be memorable for them as well. President Sung-Chul Shin said, “These gifts play the role of seed money that helps KAIST obtain competence in a global scenario. I hope people have more interest in supporting KAIST through this event.” 1 Total Amount of Gift 2 Total Donors 3 Expenditure Number of Contribution 4 Expenditure
2018.10.29
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Skin Hardness to Estimate Better Human Thermal Status
(Professor Young-Ho Cho and Researcher Sunghyun Yoon) Under the same temperature and humidity, human thermal status may vary due to individual body constitution and climatic environment. A KAIST research team previously developed a wearable sweat rate sensor for human thermal comfort monitoring. Furthering the development, this time they proposed skin hardness as an additional, independent physiological sign to estimate human thermal status more accurately. This novel approach can be applied to developing systems incorporating human-machine interaction, which requires accurate information about human thermal status. Professor Young-Ho Cho and his team from the Department of Bio and Brain Engineering had previously studied skin temperature and sweat rate to determine human thermal comfort, and developed a watch-type sweat rate sensor that accurately and steadily detects thermal comfort last February (title: Wearable Sweat Rate Sensors for Human Thermal Comfort Monitoring ). However, skin temperature and sweat rate are still not enough to estimate exact human thermal comfort. Hence, an additional indicator is required for enhancing the accuracy and reliability of the estimation and the team selected skin hardness. When people feel hot or cold, arrector pili muscles connected to hair follicles contract and expand, and skin hardness comes from this contraction and relaxation of the muscles. Based on the phenomenon of changing skin hardness, the team proposed skin hardness as a new indicator for measuring human thermal sensation. With this new estimation model using three physiological signs for estimating human thermal status, the team conducted human experiments and verified that skin hardness is effective and independent from the two conventional physiological signs. Adding skin hardness to the conventional model can reduce errors by 23.5%, which makes its estimation more reliable. The team will develop a sensor that detects skin hardness and applies it to cognitive air-conditioning and heating systems that better interact with humans than existing systems. Professor Cho said, “Introducing this new indicator, skin hardness, elevates the reliability of measuring human thermal comfort regardless of individual body constitution and climatic environment. Based on this method, we can develop a personalized air conditioning and heating system that will allow affective interaction between humans and machines by sharing both physical and mental health conditions and emotions.” This research, led by researchers Sunghyun Yoon and Jai Kyoung Sim, was published in Scientific Reports, Vol.8, Article No.12027 on August 13, 2018. (pp.1-6) Figure 1. Measuring human thermal status through skin hardness Figure 2. The instrument used for measuring human thermal status through skin hardness
2018.10.17
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Trigger of the Hyperactivation of Fibrosis Identified
(Professor Kwang-Hyun Cho from the Department of Bio and Brain Engineering) Scientists have been investigating the negative effects that the hyperactivation of fibrosis has on fibrotic diseases and cancer. A KAIST research team unveiled a positive feedback loop that bi-stably activates fibroblasts in collaboration with Samsung Medical Center. This finding will contribute to developing therapeutic targets for both fibrosis and cancer. Human fibroblasts are dormant in normal tissue, but show radical activation during wound healing. However, the principle that induces their explosive activation has not yet been identified. Here, Professor Kwang-Hyun Cho from the Department of Bio and Brain Engineering, in collaboration with Professor Seok-Hyung Kim from Samsung Medical Center, discovered the principle of a circuit that continuously activates fibroblasts. They constructed a positive feedback loops (PFLs) where Twist1, Prrx1, and Tenascin-C (TNC) molecules consecutively activate fibroblasts. They confirmed that these are the main inducers of fibroblast activation by conducting various experiments, including molecular biological tests, mathematical modeling, animal testing, and computer simulations to conclude that they are the main inducers of fibroblast activation. According to their research, Twist 1 is a key regulator of cancer-associated fibroblasts, which directly upregulates Prrx1 and then triggers TNC, which also increases Twist1 expression. This circuit consequently forms a Twist-Prrx1-TNC positive feedback loop. Activated fibroblasts need to be deactivated after wounds are healed. However, if the PFLs continue, the fibroblasts become the major cause of worsening fibrotic diseases and cancers. Therefore, the team expects that Twist1-Prrx1-TNC positive PFLs will be applied for novel and effective therapeutic targeting of fibrotic diseases and cancers. This research was published in Nature Communications on August 1, 2018. Figure 1. Twist1 increases tenascin-c expression in cancer-associated fibroblasts. Twist1 is a potent but indirect inducer of tenascin-c (TNC), which is essential for maintaining Twist1 expression in cancer-associated fibroblasts (CAFs). Figure 2. Summary of the study. The Twist1-Prrx1-TNC positive feedback regulation provides clues for understanding the activation of fibroblasts during wound healing under normal conditions, as well as abnormally activated fibroblasts in pathological conditions such as cancerous and fibrotic diseases. Under normal conditions, the PFL acts as a reversible bistable switch by which the activation of fibroblasts is “ON" above a sufficient level of stimulation and “OFF" for the withdrawal of the stimulus. However, this switch can be permanently turned on under pathologic conditions by continued activation of the PFL, resulting in sustained proliferation of fibroblasts.
2018.10.11
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Permanent, Wireless Self-charging System Using NIR Band
(Professor Jung-Yong Lee from the Graduate School of Energy, Environment, Water and Sustainability) As wearable devices are emerging, there are numerous studies on wireless charging systems. Here, a KAIST research team has developed a permanent, wireless self-charging platform for low-power wearable electronics by converting near-infrared (NIR) band irradiation to electrical energy. This novel technology can be applied to flexible, wearable charging systems without needing any attachments. Colloidal-quantum-dots (CQDs) are promising materials for manufacturing semiconductors; in particular, PbS-based CQDs have facile optical tunability from the visible to infrared wavelength region. Hence, they can be applied to various devices, such as lighting, photovoltaics (PVs), and photodetectors. Continuous research on CQD-based optoelectronic devices has increased their power conversion efficiency (PCE) to 12%; however, applicable fields have not yet been found for them. Meanwhile, wearable electronic devices commonly face the problem of inconvenient charging systems because users have to constantly charge batteries attached to an energy source. A joint team led by Professor Jung-Yong Lee from the Graduate School of Energy, Environment, Water and Sustainability and Jang Wok Choi from Seoul National University decided to apply CQD PVs, which have high quantum efficiency in NIR band to self-charging systems on wearable devices. They employed a stable and efficient NIR energy conversion strategy. The system was comprised of a PbS CQD-based PV module, a flexible interdigitated lithium-ion battery, and various types of NIR-transparent films. The team removed the existing battery from the already commercialized wearable healthcare bracelet and replaced it with the proposed self-charging system. They confirmed that the system can be applied to a low power wearable device via the NIR band. There have been numerous platforms using solar irradiation, but the newly developed platform has more advantages because it allows conventional devices to be much more comfortable to wear and charged easily in everyday life using various irradiation sources for constant charging. With this aspect, the proposed platform facilitates more flexible designs, which are the important component for actual commercialization. It also secures higher photostability and efficient than existing structures. Professor Lee said, “By using the NIR band, we proposed a new approach to solve charging system issues of wearable devices. I believe that this platform will be a novel platform for energy conversion and that its application can be further extended to various fields, including mobiles, IoTs, and drones.” This research, led by PhD Se-Woong Baek and M.S. candidate Jungmin Cho, was published in Advanced Materials on May 11. Figure 1. a) Conceptual NIR-driven self-charging system including a flexible CQD PVs module and an interdigitatedly structured LIB. b) Photographic images of a conventional wearable healthcare bracelet and a self-charging system-integrated wearable device. Figure 2. Illustration of the CQD PVs structure and performance of the wireless self-charging platform.
2018.10.08
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AI |QC ITRC Opens at KAIST
(from left: Dean of College of Engineering Jong-Hwan Kim, Director of AI│QC ITRC June-Koo Rhee, Vice President for R&DB Heekyung Park and Director General for Industrial Policy Hong Taek Yong) Artificial Intelligence|The Quantum Computing Information Technology Research Center (AI|QC ITRC) opened at KAIST on October 2. AI|QC ITRC, established with government funding, is the first institute specializing in quantum computing. Three universities (Seoul National University, Korea University, and Kyung Hee University), and four corporations, KT, Homomicus, Actusnetworks, and Mirae Tech are jointly participating in the center. Over four years, the institute will receive 3.2 billion KRW of research funds. Last April, KAIST selected quantum technology as one of its flagship research areas. AI|QC ITRC will dedicate itself to developing quantum computing technology that provides the computability required for human-level artificial intelligence. It will also foster leaders in related industries by introducing industry-academic educational programs in graduate schools. QC is receiving a great deal of attention for transcending current digital computers in terms of computability. World-class IT companies like IBM, Google, and Intel and ventures including D-Wave, Rigetti, and IonQ are currently leading the industry and investing heavily in securing source technologies. Starting from the establishment of the ITRC, KAIST will continue to plan strategies to foster the field of QC. KAIST will carry out two-track strategies; one is to secure source technology of first-generation QC technology, and the other is to focus on basic research that can preoccupy next-generation QC technology. Professor June-Koo Rhee, the director of AI│QC ITRC said, “I believe that QC will be the imperative technology that enables the realization of the Fourth Industrial Revolution. AIQC ITRC will foster experts required for domestic academia and industries and build a foundation to disseminate the technology to industries.” Vice President for R&DB Heekyung Park, Director General for Industrial Policy Hong Taek Yong from the Ministry of Science and ICT, Seung Pyo Hong from the Institute for Information & communications Technology Promotion, Head of Technology Strategy Jinhyon Youn from KT, and participating companies attended and celebrated the opening of the AI│QC ITRC.
2018.10.05
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Improved Efficiency of CQD Solar Cells Using an Organic Thin Film
(from left: Professor Jung-Yong Lee and Dr. Se-Woong Baek) Recently, the power conversion efficiency (PCE) of colloidal quantum dot (CQD)-based solar cells has been enhanced, paving the way for their commercialization in various fields; nevertheless, they are still a long way from being commercialized due to their efficiency not matching their stability. In this research, a KAIST team achieved highly stable and efficient CQD-based solar cells by using an amorphous organic layer to block oxygen and water permeation. CQD-based solar cells are light-weight, flexible, and they boost light harvesting by absorbing near-infrared lights. Especially, they draw special attention for their optical properties controlled efficiently by changing the quantum dot sizes. However, they are still incompatible with existing solar cells in terms of efficiency, stability, and cost. Therefore, there is great demand for a novel technology that can simultaneously improve both PCE and stability while using an inexpensive electrode material. Responding to this demand, Professor Jung-Yong Lee from the Graduate School of Energy, Environment, Water and Sustainability and his team introduced a technology to improve the efficiency and stability of CQD-based solar cells. The team found that an amorphous organic thin film has a strong resistance to oxygen and water. Using these properties, they employed this doped organic layer as a top-hole selective layer (HSL) for the PbS CQD solar cells, and confirmed that the hydro/oxo-phobic properties of the layer efficiently protected the PbS layer. According to the molecular dynamics simulations, the layer significantly postponed the oxygen and water permeation into the PbS layer. Moreover, the efficient injection of the holes in the layer reduced interfacial resistance and improved performance. With this technology, the team finally developed CQD-based solar cells with excellent stability. The PCE of their device stood at 11.7% and maintained over 90% of its initial performance when stored for one year under ambient conditions. Professor Lee said, “This technology can be also applied to QD LEDs and Perovskite devices. I hope this technology can hasten the commercialization of CQD-based solar cells.” This research, led by Dr. Se-Woong Baek and a Ph.D. student, Sang-Hoon Lee, was published in Energy & Environmental Science on May 10. Figure 1. The schematic of the equilibrated structure of the amorphous organic film Figure 2. Schematic illustration of CQD-based solar cells and graphs showing their performance
2018.08.27
View 6499
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