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Thermoelectric properties of solution-synthesized n-type Bi2Te3 nanocomposites modulated by Se： An experimental and theoretical study

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Nano Research 2016年第1期9卷 117-127页

作者： Haiyu Fang je-hyeong bahk Tianli Feng Zhe Cheng Amr M. S. Mohammed Xinwei Wang Xiulin Ruan Ali Shakouri Yue Wu School of Chemical Engineering Purdue University West Lafayette IN 47907 USA Birck Nanotechnology Center Purdue University West Lafayette IN 47907 USA School of Mechanical Engineering Purdue University West Lafayette IN 47907 USA Department of Mechanical Engineering Iowa State University Ames IA 50011 USA Department of Chemical and Biological Engineering Iowa State University Ames IA 50011 USA

We report the investigation of the thermoelectric properties of large-scale solution-synthesized Bi2Te3 nanocomposites prepared from nanowires hot- pressed into bulk pellets. A third element, Se, is introduced to tune the carrier concentration of the nanocomposites. Due to the Se doping, the thermoelectric figure of merit （ZT） of the nanocomposites is significantly enhanced due to the increased power factor and reduced thermal conductivity. We also find that thermal transport in our hot-pressed pellets is anisotropic, which results in different thermal conductivities along the in-plane and cross-plane directions. Theoretical calculations for both electronic and thermal transport are carried out to establish fundamental understanding of the material system and provide directions for further ZT optimization with adjustments to carrier concentration and mobility.

关键词： Bi2Te3 Se doping solution synthesis nanostructure thermoelectric

Aqueous-processable,naphthalene diimide-based polymers for eco-friendly fabrication of high-performance,n-type organic electrolyte-gated transistors

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Science China Chemistry 2022年第5期65卷 973-978页

作者： Dahyun jeong Min je Kim Seungjin Lee Jin-Woo Lee Youngwoong Kim hyeong Jun Kim jeong Ho Cho Bumjoon J.Kim Department of Chemical and Biomolecular Engineering Korea Advanced Institute of Science and Technology(KAIST)Daejeon 34141Republic of Korea Department of Chemical and Biomolecular Engineering Yonsei UniversitySeoul 03722Republic of Korea Department of Chemical and Biomolecular Engineering Sogang UniversitySeoul 04107Republic of Korea

Organic electrolyte-gated transistors(OEGTs) have the benefits of low power consumption and large current ***,the electrical performance of n-type OEGTs lags far behind that of p-type *** this study,we design a series of polymers,P(NDITEG-T) and P(NDIMTEG-T),comprising a naphthalene diimide backbone for n-type charge transport and oligo(ethylene glycol)(OEG) side chains for high ionic conductivity and eco-friendly solution *** incorporation of the OEG chain facilitates the electrochemical doping of the semiconductor by ions to realize high-performance,n-type ***,in OEGTs,P(NDITEG-T) achieves a high electron mobility of 1.0 × 10^(-1) cm^(2) V^(-1) s^(-1),which represents the highest value reported for solution-processed,n-type *** is noted that the fabrication of the OEGTs is achieved by solution processing with eco-friendly ethanol/water mixtures in virtue of the hydrophilic OEG *** work demonstrates the molecular design of the P(NDITEG-T) polymer and its significant ability to produce aqueous-processable,high-performance,and n-type OEGTs.

关键词： organic electrolyte-gated transistors n-type transistors oligo(ethylene glycol)polymers eco-friendly solution process high electron mobility

k-Nearest Neighbor Query Processing Algorithms for a Query Region in Road Networks

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Journal of Computer Science & Technology 2013年第4期28卷 585-596页

作者： hyeong-Il Kim Jae-Woo Chang Department of Computer Engineering Chonbuk National University Cloud Open R&D Center Chonbuk National University

Recent development of wireless communication technologies and the popularity of smart phones .are making location-based services （LBS） popular. However, requesting queries to LBS servers with users＇ exact locations may threat the privacy of users. Therefore, there have been many researches on generating a cloaked query region for user privacy protection. Consequently, an efficient query processing algorithm for a query region is required. So, in this paper, we propose k-nearest neighbor query （k-NN） processing algorithms for a query region in road networks. To efficiently retrieve k-NN points of interest （POIs）, we make use of the Island index. We also propose a method that generates an adaptive Island index to improve the query processing performance and storage usage. Finally, we show by our performance analysis that our k-NN query processing algorithms outperform the existing k-Range Nearest Neighbor （kRNN） algorithm in terms of network expansion cost and query processing time.

关键词： island index k-nearest neighbor query processing scheme locatiombased service road network

Simple black holes with anisotropic fluid

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Chinese Physics C 2019年第2期43卷 125-131页

作者： Inyong Cho hyeong-Chan Kim School of Liberal Arts Seoul National University of Science and Technology School of Liberal Arts and Sciences Korea National University of Transportation

We study a spherically symmetric spacetime made of an anisotropic fluid whose radial equation-of-state is given by p_1=-ρ. This case allows analytic solutions and is a good example for studying the static configuration of a black hole plus matter. For a given equation-of-state parameter w_2 = p_2/ρ for angular directions, we find the exact solutions of the Einstein equation described by two parameters. We classify the solutions into six types based on the behavior of the metric function. Depending on the parameters, the solutions can have event and cosmological horizons. One of the solution types corresponds to a generalization of the Reissner-Nordstr(o|¨)m black hole, the thermodynamic properties for which are obtained in a simple form. The solutions are stable under radial perturbations.

关键词： black hole exact solution general relativity

Rapid monitoring of indoor airborne influenza and coronavirus with high air flowrate electrostatic sampling and PCR analysis

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Frontiers of Environmental Science & Engineering 2024年第7期18卷 73-85页

作者： Sanggwon An Sangsoo Choi hyeong Rae Kim Jungho Hwang School of Mechanical Engineering Yonsei UniversitySeoul 02876Republic of Korea Gas Metrology Group Korea Research Institute of Standards and Science(KRISS)Daejeon 34113Republic of Korea

The World Health Organization has raised concerns about the possibility of airborne transmission in enclosed and poorly ventilated ***,rapid monitoring of airborne viruses is necessary in multi-use facilities with dense ***,an electrostatic air sampler(250 L/min)was developed in this work to obtain indoor viral aerosol samples for analysis via the Polymerase Chain Reaction(PCR).Aerosol tests with H1N1 and HCoV-229E were performed to evaluate the sample collection *** analysis,along with another aerosol test,was conducted to evaluate the recovery of the virus particles collected by the *** laboratory tests,our electrostatic sampler obtained viral samples that were detectable by PCR under the simulated viral pandemic scenario(3000 RNA copies per cubic meter of air)within 40 *** resulting cycle threshold(C)values were 35.07 and 37.1 for H1N1 and HCoV-229E,*** the performance evaluation in the laboratory,field tests were conducted in a university classroom from October 28 to December 2,*** A and HCoV-229E were detected in two air samples,and the corresponding C,values were 35.3 and *** PCR results are similar to those obtained from laboratory tests,considering the simulatedviralpandemic scenario.

关键词： Airborne virus Electrostatic sampler Rapid monitoring Indoor environment Field test

Prediction of Monthly Mean Surface Air Temperature in a Region of China

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Advances in Atmospheric Sciences 2007年第3期24卷 503-508页

作者： jeong-hyeong LEE Keon-Tae SOHN Division of Management Information Science Dong-A University Busan 604-714Korea Department of Statistics Pusan National University Busan 609-735Korea

In conventional time series analysis, a process is often modeled as three additive components： linear trend, seasonal effect, and random noise. In this paper, we perform an analysis of surface air temperature in a region of China using a decomposition method in time series analysis. Applications to the National Centers for Environmental Prediction/the National Center for Atmospheric Research （NCEP/NCAR） Collaborative Reanalysis data in this region of China are discussed. The main finding was that the surface air temperature trend estimated for January 1948 to February 2006 was not statistically significant at 0.5904℃ （100 yr）^-1. Forecasting aspects are also considered.

关键词： Chinese region surface air temperature time series decomposition method regression

Benefits of Stochastic Optimization for Scheduling Energy Storage in Wholesale Electricity Markets

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Journal of Modern Power Systems and Clean Energy 2021年第1期9卷 181-189页

作者： hyeong Jun Kim Ramteen Sioshansi Antonio J.Conejo the Department of Integrated Systems Engineering The Ohio State UniversityColumbusOhioUSA the Department of Electrical and Computer Engineering The Ohio State UniversityColumbus.OhioUSA

We propose a two-stage stochastic model for optimizing the operation of energy storage. The model captures two important features: uncertain real-time prices when day-ahead operational commitments are made;and the price impact of charging and discharging energy storage. We demonstrate that if energy storage has full flexibility to make real-time adjustments to its day-ahead commitment and market prices do not respond to charging and discharging decisions, there is no value in using a stochastic modeling framework, i.e., the value of stochastic solution is always zero. This is because in such a case the energy storage behaves purely as a financial arbitrageur day ahead, which can be captured using a deterministic *** show also that prices responding to its operation can make it profitable for energy storage to "waste" energy, for instance by charging and discharging simultaneously, which is normally sub-optimal. We demonstrate our model and how to calibrate the price-response functions from historical data with a practical case study.

关键词： Energy storage stochastic optimization value of stochastic solution electricity market

Design and analysis of electrothermal metasurfaces

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Frontiers in Energy 2023年第1期17卷 134-140页

作者： Xiu LIU Zhuo LI Zexiao WANG hyeong Seok YUN Sheng SHEN Department of Mechanical Engineering Carnegie Mellon UniversityPittsburghPA 15213USA

Electrothermal metasurfaces have garneredconsiderable attention owing to their ability to dynamicallycontrol thermal infrared radiation. Although previousstudies were mainly focused on metasurfaces with infiniteunit cells, in practice, the finite-size effect can be a criticaldesign factor for developing thermal metasurfaces withfast response and broad temperature uniformity. Here, westudy the thermal metasurfaces consisting of goldnanorods with a finite array size, which can achieve aresonance close to that of the infinite case with onlyseveral periods. More importantly, such a small footprintdue to the finite array size yields response time down to ananosecond level. Furthermore, the number of the unitcells in the direction perpendicular to the axis of nanorodsis found to be insensitive to the resonance and responsetime;thus, providing a tunable aspect ratio that can boostthe temperature uniformity in the sub-Kelvin level.

关键词： modulated thermal infrared radiation metasurface nanosecond response time sub-Kelvin temperature uniformity finite size aspect ratio

Practical Privacy-Preserving ROI Encryption System for Surveillance Videos Supporting Selective Decryption

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Computer Modeling in Engineering & Sciences 2024年第12期141卷 1911-1931页

作者： Chan hyeong Cho Hyun Min Song Taek-Young Youn Department of Cyber Security Dankook UniversityYonginGyeonggi-Do16890Republic of Korea

With the advancement of video recording devices and network infrastructure,we use surveillance cameras to protect our valuable *** paper proposes a novel system for encrypting personal information within recorded surveillance videos to enhance efficiency and *** proposed method leverages Dlib’s CNN-based facial recognition technology to identify Regions of Interest(ROIs)within the video,linking these ROIs to generate unique *** IDs are then combined with a master key to create entity-specific keys,which are used to encrypt the ROIs within the *** system supports selective decryption,effectively protecting personal information using surveillance ***,the system overcomes the limitations of existing ROI recognition technologies by predicting unrecognized frames through *** research validates the proposed technology through experimental evaluations of execution time and post-processing techniques,ensuring comprehensive personal information *** for setting the thresholds used in this process are also *** the proposed method could serve as an effective solution to security vulnerabilities that traditional approaches fail to address.

关键词： Privacy de-identification selective decryption surveillance video