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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

Aerodynamic design optimization of helicopter rotor blades including airfoil shape for hover performance

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Chinese Journal of Aeronautics 2013年第1期26卷 1-8页

作者： Ngoc Anh Vu Jae woo Lee Jung il Shu Department of Aerospace Engineering Ho Chi Minh City University of Technology Department of Aerospace Information Engineering Konkuk University

This study proposes a process to obtain an optimal helicopter rotor blade shape for aerodynamic performance in hover flight. A new geometry representation algorithm which uses the class function/shape function transformation （CST） is employed to generate airfoil coordinates. With this approach, airfoil shape is considered in terms of design variables. The optimization process is constructed by integrating several programs developed by author. The design variables include twist, taper ratio, point of taper initiation, blade root chord, and coefficients of the airfoil distribution function. Aerodynamic constraints consist of limits on power available in hover and forward flight. The trim condition must be attainable. This paper considers rotor blade configuration for the hover flight condition only, so that the required power in hover is chosen as the objective function of the optimization problem. Sensitivity analysis of each design variable shows that airfoil shape has an important role in rotor performance. The optimum rotor blade reduces the required hover power by 7.4% and increases the figure of merit by 6.5%, which is a good improvement for rotor blade design.

关键词： Airfoil Design optimization Helicopter design Hover performance Planforms Rotor blades design

Frequency comb-to-comb stabilization over a 1.3-km free-space atmospheric optical link

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Light(Science & Applications) 2022年第9期11卷 2207-2216页

作者： JAEWON yang DONG il LEE DONG-CHEL SHIN JAEHYUN LEE BYUNG SOO KIM HYUN JAY KANG YOUNG-JIN KIM SEUNG-woo KIM Department of Mechanical Engineering Korea Advanced Institute of Science and Technology(KAIST)291 Daehak-roYuseong-guDaejeon 34141Republic of Korea Presently with Korea Research Institute of Standards and Science(KRISS) 267 Gajeong-roYuseong-guDaejeon 34113Republic of Korea

Stabilizing a frequency comb to an ultra-stable optical frequency reference requires a multitude of optoelectronic peripherals that have to operate under strict ambient ***,the frequency comb-to-comb stabilization aims to synchronize a slave comb to a well-established master comb with a substantial saving in required equipment and ***,we report an utmost case of frequency comb-to-comb stabilization made through a 1.3 km free-space optical(FSO)link by coherent transfer of two separate comb lines along with a feedback suppression control of atmospheric phase *** FSO link offers a transfer stability of 1.7×10-15 at 0.1 s averaging,while transporting the master comb,s stability of 1.2×10-15 at 1.0 s over the entire spectrum of the slave *** remote comb-to-comb stabilization is intended to expedite diverse long-distance ground-to-ground or ground-to-satellite applications;as demonstrated here for broadband molecular spectroscopy over a 6THz bandwidth as well as ultra-stable microwaves generation with phase noise of-80dBc Hz-1 at 1 Hz.

关键词： optical stabilization microwave

Optimal Checkpoint Placement on Real-Time Tasks with Harmonic Periods

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Journal of Computer Science & Technology 2012年第1期27卷 105-112页

作者： Seong woo Kwak Jung-Min yang Department of Electronic Engineering Keimyung University Department of Electrical Engineering Catholic University of Daegu

This paper presents an optimal checkpoint strategy for fault-tolerance in real-time systems where transient faults occur in Poisson distribution. In our environment, multiple real-time tasks with different deadlines and harmonic periods are scheduled in the system by rate-monotonic algorithm, and checkpoints are inserted at a constant interval in each task. When a fault is detected, the system carries out rollback to the latest checkpoint and re-executes tasks. The maximum number of re-executable checkpoints and an equation to check schedulability are derived, and the optimal number of checkpoints is selected to maximize the probability of completing all the tasks within their deadlines.

关键词： checkpoint scheme real-time system fault-tolerance harmonic period rate-monotonic (RM) scheduling

Effect of grain refinement on phase transformation behavior and mechanical properties of Cu-based alloy

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中国有色金属学会会刊：英文版 2009年第4期19卷 979-983页

作者： Gwon-Seung yang Jong-Kook LEE woo-yang JANG Department of Advanced Materials Engineering Chosun University Department of Metallurgical Engineering Chosun University

A small amount of misch metal was added to Cu-Zn-Al alloy in order to study its effect on grain refinement,mechanical properties,phase transformation behavior and stabilization of *** is found that the addition of misch metal is very effective for reducing the grain *** coarse grains over 1 000 μm are refined to the size of 30 μm by the addition of 0.43%(mass fraction) misch *** grain size of thermo-mechanically treated alloys is barely affected by cold *** fracture strength and ductility increase significantly with the increase of misch metal content when tensile test is carried out below Mf ***,the fracture strength is larger in the case of post-quench ageing treatment than that in the case of direct quench ageing *** fracture mode is changed from transgranular brittle fracture to ductile fracture with void formation and coalescence by the addition of misch metal.

关键词：铜基合金力学性能相变行为晶粒细化金属拉伸试验晶粒尺寸断裂强度时效处理

Augmenting freshwater availability in mountain headwater streams:Assessing the sustainability under baseline and future climate change scenarios

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International Soil and Water Conservation Research 2022年第2期10卷 293-307页

作者： Bisrat Ayalew Yifru il-Moon Chung Min-Gyu Kim Sun woo Chang Department of Land Water and Environment ResearchKorea Institute of Civil Engineering and Building TechnologyGoyang10223South Korea Department of Civil and Environmental Engineering University of Science and TechnologyDaejeon34113South Korea

Mountain headwater streams are important freshwater sources,but they are mostly intermittent and highly susceptible to climate *** paper examines the sustainability of augmented freshwater availability in mountain headwater streams for water supply under baseline and future climate change scenarios using an integrated modeling *** climate change data in the 2040s(2030e2059),under Representative Concentration Pathway 4.5 and 8.5 scenarios,were downscaled for the impact *** the region,climate change raises the average precipitation by 5e7%and the temperature by 13e15%in the *** model,integrating Soil and Water Assessment Tool(SWAT2012)and finite-difference Modular Groundwater Flow(MODFLOW)models in a single package,was used to assess the water *** show that extracting a minimum of 16.2 m^(3)/day from the sand storage and 30 m^(3)/day from the aquifer was possible without affecting the groundwater table and water *** average annual catchment recharge was 6%of the precipitation under the baseline *** change is projected to reduce the average water yield and groundwater recharge by 26%and 19%,***,the water supply-demand is significantly small compared to the exploitable rate of water in the *** study was based on limited data,and therefore the findings need to be interpreted with caution,though the model output was validated using satellite *** of a series of sand dams is suggested to maximize the benefit under the potential climate change and water supply-demand increase.

关键词： Headwater stream Sand dam Korea SWATeMODFLOW Water conservation Climate change

Emerging wearable flexible sensors for sweat analysis

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Bio-Design and Manufacturing 2022年第1期5卷 64-84页

作者： Wenzheng Heng Geng yang woo SooKim Kaichen Xu State Key Laboratory of Fluid Power and Mechatronic Systems School of Mechanical EngineeringZhejiang UniversityHangzhou 310027China Andrew and Peggy Cherng Department of Medical Engineering California Institute of TechnologyPasadenaCA 91125USA School of Mechatronic Systems Engineering Simon Fraser UniversitySurreyBC V3T 0A3Canada

Sweat,as a biofluid with the potential for noninvasive collection,provides profound insights into human health conditions,because it contains various chemicals and information to be utilized for the monitoring of well-being,stress levels,exercise,and ***,wearable sweat sensors have been developed as a promising substitute to conventional laboratory sweat detection *** sensors are promising to realize low-cost,real-time,in situ sweat measurements,and provide great opportunities for health status evaluation analysis based on personalized big *** review first presents an overview of wearable sweat sensors from the perspective of basic components,including materials and structures for specific sensing applications and *** strategies and specific methods of the fabrication of wearable power management are also ***,current challenges and future directions of wearable sweat sensors are discussed.

关键词： Flexibleelectronics Wearablesensors Sweat sensors Electrochemical analysis Noninvasivehealth monitoring Powersupply

Quick Line Outage Identification in Urban Distribution Grids via Smart Meters

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CSEE Journal of Power and Energy Systems 2022年第4期8卷 1074-1086页

作者： Yizheng Liao yang Weng Cin-woo Tan Ram Rajagopal Department of Civil and Environmental Engineering Stanford UniversityStanfordCA94305USA School of Electrical Computingand Energy EngineeringArizona State UniversityTempeAZ85287USA

The growing integration of distributed energy resources(DERs)in distribution grids raises various reliability issues due to DER's uncertain and complex *** large-scale DER penetration in distribution grids,traditional outage detection methods,which rely on customers report and smart meters'“last gasp”signals,will have poor performance,because renewable generators and storage and the mesh structure in urban distribution grids can continue supplying power after line *** address these challenges,we propose a datadriven outage monitoring approach based on the stochastic time series analysis with a theoretical ***,we prove via power flow analysis that dependency of time-series voltage measurements exhibits significant statistical changes after line *** makes the theory on optimal change-point detection suitable to identify line ***,existing change point detection methods require post-outage voltage distribution,which are unknown in distribution ***,we design a maximum likelihood estimator to directly learn distribution parameters from voltage *** prove the estimated parameters-based detection also achieves optimal performance,making it extremely useful for fast distribution grid outage ***,since smart meters have been widely installed in distribution grids and advanced infrastructure(e.g,PMU)has not widely been available,our approach only requires voltage magnitude for quick outage *** results show highly accurate outage identification in eight distribution grids with 17 configurations with and without DERs using smart meter data.

关键词： Power distribution network outage detection outage identification voltage measurement change point detection graphical model

Crushing behavior of lightmass structural member

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中国有色金属学会会刊：英文版 2009年第B09期19卷 276-279页

作者： Kil-Sung LEE Yong-June yang woo-Chae HWANG In-Young yang Department of Mechatronics Chosun University of Science and Technology Department of Advanced Part and Materials Engineering Chosun University Department of Mechanical Design Engineering Chosun University

Carbon fiber reinforced plastic (CFRP) of the advanced composite materials is widely used in lightmass structural materials of air planes, ship and automobiles because of high strength and stiffness. In this study, experimental investigation was performed for each specimen. The square section members consist of aluminum, CFRP and hybrid (aluminum/CFRP) member, and hat-shaped section members consist of CFRP and hybrid (aluminum/CFRP) members specimen. Based on the collapse characteristics of aluminum square section member, the collapse characteristics and energy absorption capability of hat-shaped section members were analyzed. The axial static collapse tests were carried out for each section member. The collapse modes and the energy absorption capability of the members were analyzed. In the lightmass design aspect, the collapse characteristics and energy absorption capability of the members were compared.

关键词：碳纤维增强复合材料碳纤维复合材料能量吸收能力行为构件破碎航空飞机 CFRP