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Preliminary experimental study of a supercritical CO2 power cycle test loop with a high-speed turbo-generator using R134a under similarity conditions

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Frontiers in Energy 2017年第4期11卷 452-460页

作者： Junhyun CHO Hyungki SHIN Jongjae CHO Young-Seok KANG Ho-Sang RA Chulwoo ROH Beomjoon LEE Gilbong LEE Byunghui KIM Young-Jin BAIK Thermal Energy system Laboratory Korea Institute of Energy Research 152 Gajeong-ro Yusung-gu Daejeon 34129 Republic of Korea Engine Component Research team Korea Aerospace Research Institute (KARl) 169-84 Gwahak-ro Yusung-gu Daejeon 34133 Republic of Korea InGineers 21 Saman-ro 16 Beon-gil Gimhae-si Gyeongsangnam-do 621-220 Republic of Korea

Research on applying a supercritical carbon dioxide power cycle （S-CO2） to concentrating solar power （CSP） instead of a steam Rankine cycle or an air Brayton cycle has been recently conducted. An S-CO2 system is suitable for CSP owing to its compactness, higher efficiency, and dry-cooling capability. At the Korea Institute of Energy Research （KIER）, to implement an S-CO2 system, a 10 kWe class test loop with a turbine- alternator-compressor （TAC） using gas foil bearings was developed. A basic sub-kWe class test loop with a high- speed radial type turbo-generator and a test loop with a capability of tens of kWe with an axial type turbo- generator were then developed. To solve the technical bottleneck of S-CO2 turbomachinery, a partial admission nozzle and oil-lubrication bearings were used in the turbo- generators. To experience the closed-power cycle and develop an operational strategy of S-CO2 operated at high pressure, an organic Rankine cycle （ORC） operating test using a refrigerant as the working fluid was conducted owing to its operational capability at relatively low- pressure conditions of approximately 30 to 40 bar. By operating the sub-kWe class test loop using R134a as the working fluid instead of CO2, an average turbine power of 400 W was obtained.

关键词： supercritical CO2 power cycle turbomachin-ery compressor turbine

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Managing advertising campaigns-an approximate planning approach

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Frontiers of Computer Science 2012年第2期6卷 209-229页

作者： SertanGIRGIN JérémieMARY PhilippePREUX OlivierNICOL team—projectSequeL INRIALilleNordEuropeVilleneuved’Ascq59650France LIFLUMRCNRS Universit6deLilleVilleneuved’Ascq59650France

We consider the problem of displaying commer- cial advertisements on web pages, in the ＂cost per click＂ model. The advertisement server has to learn the appeal of each type of visitor for the different advertisements in order to maximize the profit. Advertisements have constraints such as a certain number of clicks to draw, as well as a lifetime. This problem is thus inherently dynamic, and intimately com- bines combinatorial and statistical issues. To set the stage, it is also noteworthy that we deal with very rare events of in- terest, since the base probability of one click is in the or- der of 10-4. Different approaches may be thought of, rang- ing from computationally demanding ones （use of Markov decision processes, or stochastic programming） to very fast ones. We introduce NOSEED, an adaptive policy learning al- gorithm based on a combination of linear programming and multi-arm bandits. We also propose a way to evaluate the extent to which we have to handle the constraints （which is directly related to the computation cost）. We investigate the performance of our system through simulations on a realistic model designed with an important commercial web actor.

关键词： advertisement selection web sites optimiza-tion non-stationary setting linear programming multi-armbandit click-through rate (CTR) estimation exploration-exploitation trade-off

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Phase-field framework with constraints and its applications to ductile fracture in polycrystals and fatigue

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npj Computational Materials 2022年第1期8卷 149-163页

作者： Fei Xue Tian-Le Cheng Yinkai Lei You-Hai Wen U.S.DOE National Energy Technology Laboratory AlbanyOR 97321USA Leidos Research Support team AlbanyOR 97321USA

Modeling of ductile fracture in polycrystalline structures is challenging,since it requires integrated modeling of cracks,crystal plasticity,and *** we extend the typical phase-field framework to the situations with constraints on the order parameters,and formulate two types of phase-field models on ductile *** Type-Ⅰ model incorporates three sets of order parameters,which describe the distributions of cracks,plastic strain,and grains,*** plasticity is employed within grain interiors accommodated by J_(2)plasticity at grain *** applications of the Type-Ⅰ model to single crystals and bicrystals demonstrate the influences of grain orientations and grain boundaries on crack *** the Type-Ⅱ model,J_(2)plasticity is assumed for the whole system and grain structures are *** advantage of the efficiency of the fast Fourier transform,our Type-Ⅱ model is employed to study low cycle *** closure and striation-like patterning of plastic strain are observed in the *** growth rate is analyzed as a function of the J-integral,and the simulated fatigue life as a function of plastic strain agrees with the Coffin–Manson relation without a priori assumption.

关键词： ductile fatigue grain

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Novel Magnesium Alloys Developed for Biomedical Application:A Review

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Journal of Materials Science & Technology 2013年第6期29卷 489-502页

作者： Nan Li Yufeng Zheng State Key Laboratory for Turbulence and Complex system and Department of Materials Science and Engineering College of EngineeringPeking University

There is an increasing interest in the development of magnesium alloys both for industrial and biomedical applications. Industrial interest in magnesium alloys is based on strong demand of weight reduction of transportation vehicles for better fuel efficiency, so higher strength, and better ductility and corrosion resistance are required. Nevertheless, biomedical magnesium alloys require appropriate mechanical properties, suitable degradation rate in physiological environment, and what is most important, biosafety to human body. Rather than simply apply commercial magnesium alloys to biomedical field, new alloys should be designed from the point of view of nutriology and toxicology. This article provides a review of state-of-the-art of magnesium alloy implants and devices for orthopedic, cardiovascular and tissue engineering applications. Advances in new alloy design, novel structure design and surface modification are overviewed. The factors that influence the corrosion behavior of magnesium alloys are discussed and the strategy in the future development of biomedical magnesium alloys is proposed.

关键词： Biomaterials Magnesium alloys Biodegradation Mechanical property Biocompatibility

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An Apparatus Design for the Vehicle Control Scheme in Personal Rapid Transit system

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Journal of Mechanics Engineering and Automation 2013年第5期3卷 325-333页

作者： Jun-Ho Lee Advanced Traction and Noncontact Feeding system Research team Korea Railroad Research Institute Gyeonggi-do Uiwang-City437-757 Korea

A new transportation technology known as personal rapid transit （PRT） is being developed by multiple different companies around the world, and one system is under commercial operations in the United Kingdom. Each design is different, but they all share a need to operate many automated transit vehicles at very close headways. Safe operation will require a level of control an order of magnitude above any current transit system. As a result, new techniques will be needed for the development and testing of the mechanical and control systems. In this paper an apparatus for developing and testing a PRT vehicle control scheme is demonstrated. This system is composed of independent modules that represent virtual vehicles, a central control system, a man-machine interface and a monitoring device. It can be used to implement and to evaluate the designed vehicle control algorithm. The vehicle control algorithm is designed and simulated in a combined simulation platform that consists of Matlab/Simulink and Labview Simulation Interface Toolkit. Simple operational scenarios are proposed for the testing of the proposed vehicle control apparatus.

关键词： Personal rapid transit vehicle control scheme virtual vehicles safe operation headway.

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Clinical trial perspective for adult and juvenile Huntington's disease using genetically-engineered mesenchymal stem cells

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Neural Regeneration Research 2016年第5期11卷 702-705页

作者： Peter Deng Audrey Torrest Kari Pollock Heather Dahlenburg Geralyn Annett Jan A.Nolta Kyle D.Fink Stem Cell Program and Institute for Regenerative Cures University of California Davis Health System

Progress to date from our group and others indicate that using genetically-engineered mesenchymal stem cells（MSC） to secrete brain-derived neurotrophic factor（BDNF） supports our plan to submit an Investigational New Drug application to the Food and Drug Administration for the future planned Phase 1 safety and tolerability trial of MSC/BDNF in patients with Huntington＇s disease（HD）. There are also potential applications of this approach beyond HD. Our biological delivery system for BDNF sets the precedent for adult stem cell therapy in the brain and could potentially be modified for other neurodegenerative disorders such as amyotrophic lateral sclerosis（ALS）, spinocerebellar ataxia（SCA）, Alzheimer＇s disease, and some forms of Parkinson＇s disease. The MSC/BDNF product could also be considered for studies of regeneration in traumatic brain injury, spinal cord and peripheral nerve injury. This work also provides a platform for our future gene editing studies, since we will again use MSCs to deliver the needed molecules into the central nervous system.

关键词： mesenchymal stem cells neurodegenerative disorders, Huntington's disease genetic engineering brain derived neurotrophic factor

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A Study on the Levitation Control of the Multi-degrees-of-Freedom Rotational Machine Supported by Magnetic Bearings Using Flux Feedback

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Journal of Mechanics Engineering and Automation 2014年第6期4卷 533-541页

作者： Jun-Ho Lee Advanced Traction and Noncontact Feeding system Research team Korea Railroad Research Institute Uiwang-City Gyeonggi-do437-757 Korea

This paper deals with an open-loop characteristic of a magnetically levitated system including flux feedback. In order to design a controller to obtain a good disturbance rejection and to be insensitive to parameter variations, it might be useful to employ a flux feedback loop. The air gap flux which can be sensed by a proper sensor has linear relationship with respect to the change of the current and the air gap. This linear property decreases the inherent nonlinearity of the magnetic suspension system that is caused by the coupling between the electrical actuator and the mechanical plant. Simulation results achieved from a multi-degree-of-freedom numerical model show that the flux feedback loop makes an improvement of the performance of the magnetic suspension system against the load variations.

关键词： Flux feedback magnetic bearings levitation rotational machine multi-degrees-of-freedom

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What did we learn from preparing for cross-border transmission of Ebola virus disease into a complex humanitarian setting-The Republic of South Sudan?

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Infectious Diseases of Poverty 2020年第2期9卷 106-107页

作者： Olushayo Oluseun Olu Richard Lako Joseph Francis Wamala Patrick Otim Ramadan Caroline Ryan Ifeanyi Udenweze Kibebu Berta Argata Guracha Guyo Alex Sokemawu Michael Tukuru Henry John Gray Alex Chimbaru World Health Organization Ebola Virus Disease preparedness team JubaRepublic of South Sudan 不详

Background:Following the West Africa Ebola virus disease(EVD)outbreak(2013-2016),WHO developed a preparedness checklist for its member *** checklist is currently being applied for the first time on a large and systematic scale to prepare for the cross border importation of the ongoing EVD outbreak in the Democratic Republic of Congo hence the need to document the lessons learnt from this *** is more pertinent considering the complex humanitarian context and weak health system under which some of the countries such as the Republic of South Sudan are implementing their EVD preparedness *** text:We identified four main lessons from the ongoing EVD preparedness efforts in the Republic South ***,EVD preparedness is possible in complex humanitarian settings such as the Republic of South Sudan by using a longer-term health system strengthening ***,the Republic of South Sudan is at risk of both domestic and cross border transmission of EVD and several other infectious disease outbreaks hence the need for an integrated and sustainable approach to outbreak preparedness in the ***,a phased and well-prioritized approach is required for EVD preparedness in complex humanitarian settings given the costs associated with preparedness and the difficulties in the accurate prediction of outbreaks in such ***,EVD preparedness in complex humanitarian settings is a massive undertaking that requires effective and decentralized ***:Despite a very challenging context,the Republic of South Sudan made significant progress in its EVD preparedness drive demonstrating that it is possible to rapidly scale up preparedness efforts in complex humanitarian contexts if appropriate and context-specific approaches are *** research,systematic reviews and evaluation of the ongoing preparedness efforts are required to ensure comprehensive documentation and application of the lessons learnt for future EV

关键词： Lessons learnt Ebola virus disease Preparedness Complex humanitarian settings The Republic of South Sudan

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Long Pulse Operation of High Performance Plasmas in JT-60U

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Plasma Science and Technology 2006年第1期8卷 1-4页

作者： S.IDE the 3T-60 team Naka Fusion Research Establishment Japan Atomic Energy Agency NakaIbaraki311-0193Japan

Recent experimental progress in JT-60U advanced tokamak research is presented： sustainment of the normalized beta （βN）- 3 in a normal magnetic shear plasma, the bootstrap current fraction （fBs） - 45% in a weak shear plasma and - 75% in a reversed magnetic shear plasma in a nearly fully non-inductive current drive condition for longer than the current relaxation time. Achievement of high-density, high-radiation fraction together with high-confinement in advanced plasmas is demonstrated. Achievements and findings in long pulse operations after system modification are presented as well. A 65 s discharge of Ip = 0.7 MA was successfully obtained. As a result, high-βN of 2.3 was successfully sustained for a very long period of 22.3 s. In addition, a 30 s standard ELMy H-mode plasma of Ip up to 1.4 MA was also obtained. Effectiveness of divertor pumping to control particle recycling and the electron density under the saturated wall retention was demonstrated. These achievements and issues in development are discussed.

关键词： transport properties magnetohydrodynamics tokamaks

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Distributed Information Flow Verification for Secure Service Composition in Smart Sensor Network

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China Communications 2016年第4期13卷 119-130页

作者： XI Ning SUN Cong MA Jianfeng CHEN Xiaofeng SHEN Yulong Shaanxi Key Laboratory of Network and system Security XIDIAN University School of Cyber Engineering XIDIAN University

Accelerate processor, efficient software and pervasive connections provide sensor nodes with more powerful computation and storage ability, which can offer various services to user. Based on these atomic services, different sensor nodes can cooperate and compose with each other to complete more complicated tasks for user. However, because of the regional characteristic of sensor nodes, merging data with different sensitivities become a primary requirement to the composite services, and information flow security should be intensively considered during service composition. In order to mitigate the great cost caused by the complexity of modeling and the heavy load of single-node verification to the energy-limited sensor node, in this paper, we propose a new distributed verification framework to enforce information flow security on composite services of smart sensor network. We analyze the information flows in composite services and specify security constraints for each service participant. Then we propose an algorithm over the distributed verification framework involving each sensor node to participate in the composite service verification based on the security constraints. The experimental results indicate that our approach can reduce the cost of verification and provide a better load balance.

关键词： information flow security service composition formal verification smart sensor network

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