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Characterizing pressure fluctuation into single-loop oscillating heat pipe

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Journal of Central South University 2012年第9期19卷 2578-2583页

作者： PARK Yong-ho Md.Riyad Tanshen Md.J.Nine chung han-shik JEONG Hyo-min Department of Mechanical Engineering Koje CollegeJangseungpoKojeGyeongnamKorea Department of Mechanical and Precision Engineering Gyeongsang National University 445 Inpyeong-dongTongyeongGyeongnam650-160Korea Department of Energy and Mechanical Engineering Institute of Marine IndustryGyeongsang National UniversityCheondaegukchi-Gil 38TongyeongGyeongnam650-160Korea

The pressure characteristics inside single loop oscillating heat pipe （OHP） having 4.5 mm inner diameter copper tube with the loop height of 440 mm were addressed. Distilled water was used as working fluid inside the OHP with different filling ratios of 40%, 60% and 80% of total inside volume. Experimental results show that the thermal characteristics are significantly inter-related with pressure fluctuations as well as pressure frequency. And the pressure frequency also depends upon the evaporator temperature that is maintained in the range of 60-96 ℃. Piezoresistive absolute pressure sensor （Model-Kistler 4045A5） was used to take data. The investigation shows that the filling ratio of 60% gives the highest inside pressure magnitude at maximum number of pressure frequency at any of set evaporator temperature and the lowest heat flow resistance is achieved at 60% filling ratio.

关键词： oscillating heat pipe pressure fluctuation heat flow resistance filling ratio

Numerical assessment on improving multistage centrifugal impeller performance by changing inlet skew angle at impeller inlet

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Journal of Central South University 2012年第4期19卷 953-961页

作者： M.N.Labib Woo Ju-sik Choi Du-youl T.Utomo B.Fajar chung han-shik Jeong Hyo-min Graduate School of Department of Mechanical and Precision Engineering Gyeongsang National UniversityTongyeong 650-160Korea Fluid and Thermal Engineering Co.Ltd. Kyungnam 621-843Korea Department of Mechanical Engineering Engineering FacultyUniversity of DiponegoroSemarang 1269Indonesia Department of Mechanical and Precision Engineering Gyeongsang National UniversityThe Institute of Marine Industr yTongyeong 650-160Korea Department of Mechanical and Precision Engineering Gyeongsang National UniversityThe Institute of Marine Industr yTongyeong 650-160Kore

Multistage centrifugal impellers with four different skew angles were investigated by using computational fluid *** purpose of this work is to investigate the influences of lean angle at the blade tip of the impeller *** variations of lean angles,that is,8°,10°,15° and 20°,were made at first stage *** Average Navier Stokes equation was used in simulation together with a shear?stress transport(SST) k-w turbulence model and mixing-plane approach,*** dimensional fluid flows were simplified using periodic model to reduce the computational cost and time required.A good performance was expected that the secondary flow can be effectively reduced in the flow passage of the impeller without excessive increase in manufacturing cost caused by the secondary *** results show that secondary flow affects the main flow intricately to form vortices or having non-uniform velocity in the flow passage,which in turn results in substantial fluid energy loss not only in the impeller but also in the guide vane downstream of *** numerical solutions were performed and allowed the optimum design and operating conditions to be obtained.

关键词： computational fluid dynamics secondary flow blade inlet skew angle multistage centrifugal compressor

Heat transfer characteristics of nanofluid through circular tube

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Journal of Central South University 2013年第1期20卷 142-148页

作者： WUSIMAN Ku-er-ban-jiang chung han-shik MD.J.Nine hanDRY Afrianto EOM Yoon-sub KIM Jun-hyo JEONG Hyo-min Department of Mechanical and Precision Engineering GyeongSang National University445 Inpyeong-dongTongYoungGyeongNam 650-160Korea Department of Energy and Mechanical Engineering The Institute of Marine IndustryGyeongSang National University445 Inpyeong-dongTongYoungGyeongNam 650-160Korea Division of Marine Engineering Mokpo National Maritime UniversityHaeyangdaehang-Ro 91Mokpo-siJeollanam-do530-729Korea

Nano fluid is considered to be a class of high efficient heat transfer fluid created by dispersing some special solid nanoparticles (normally less than 100 nm) in traditional heat transfer fluid. The present experiment was conducted aiming at investigating the forced heat transfer characteristics of aqueous copper (Cu) nanofluid at varying concentration of Cu nano-particles in different flow regimes (300hancement is available both in the laminar and turbulent flow with increasing the concentration. Especially, the enhancement rate increases dramatically in laminar flow regime, for instance, the heat transfer coefficient of Cu/water nanofluid increases by two times at around Re=2 000 compared with that of base fluid water, and averagely increases by 62% at 1% volume fraction. However, the heat transfer coefficient of Cu/water decreases sharply in the transition flow regime. Furthermore, it has the trend that the heat transfer coefficient displays worse with increasing the concentration.

关键词： nanofluid heat transfer characteristic circular tube metallic particles

Liquid film falling behaviour on horizontal circular cylinder

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Journal of Central South University 2012年第5期19卷 1353-1358页

作者： chung han-shik K.Wusiman KIM Seong-soo B.Nasan H.Afrianto Hafizur Rehman CHOI Du-youl JEONG Hyo-min Department of Energy and Mechanical Engineering The Institute of Marine IndustryGyeongSang National UniversityTongYoungGyeongNam 650-160Korea Department of Mechanical and Precision Engineering GyeongSang National UniversityTongYoungGyeongNam 650-160Korea Fluid and Thermal Engineering Co. Ltd.GimHae-siGyungNam 621-843Korea

The flow pattern behaviour of falling liquid film over three horizontal cylinders was *** flows can take three forms:discrete droplets,individual jets,and continuous sheet,and special attention is paid to the effects of the physical properties and geometrical parameters of the first two forms(droplets and jets) because these forms are more important in heat-transfer behaviour and less research has been published for these forms,The flow modes and experimental results were successfully compared with previous experimental literatures,and also the effects of liquid flow rate,tube diameter,and tube spacing on departure site spacing,in both drop and jet modes,were evaluated in the low Galileo number and high viscosity fluid(cooking oil),to help developing criteria for determining falling film modes and their transitions,and to understand the heat transfer characteristics associated with each mode.

关键词： falling film flow mode cylinder

Crystallization Modulation and Holistic Passivation Enables Efficient Two‑Terminal Perovskite/CuIn(Ga)Se_(2)Tandem Solar Cells

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Nano-Micro Letters 2025年第1期17卷 205-215页

作者： Cong Geng Kuanxiang Zhang Changhua Wang chung Hsien Wu Jiwen Jiang Fei Long Liyuan han Qifeng han Yi‑Bing Cheng Yong Peng State Key Laboratory of Advanced Technology for Materials Synthesis and Processing Wuhan University of TechnologyWuhan 430070People’s Republic of China Triumph Photovoltaic Materials Co. Ltd.No.1001 Yannan AvenueHigh‑Tech Development DistrictBengbuAnhui 233000People’s Republic of China College of Materials Science and Engineering Guilin University of TechnologyGuilin 541004People’s Republic of China State Key Laboratory of Metal Matrix Composites Shanghai Jiao Tong UniversityShanghai 200240People’s Republic of China

Two-terminal(2-T)perovskite(PVK)/CuIn(Ga)Se_(2)(CIGS)tandem solar cells(TSCs)have been considered as an ideal tandem cell because of their best bandgap matching regarding to Shockley–Queisser(S–Q)***,the nature of the irregular rough morphology of commercial CIGS prevents people from improving tandem device *** this paper,D-homoserine lactone hydrochloride is proven to improve coverage of PVK materials on irregular rough CIGS surfaces and also passivate bulk defects by modulating the growth of PVK *** addition,the minority carriers near the PVK/C60 interface and the incompletely passivated trap states caused interface recombination.A surface reconstruction with 2-thiopheneethylammonium iodide and N,N-dimethylformamide assisted passivates the defect sites located at the surface and grain ***,LiF is used to create this field effect,repelling hole carriers away from the PVK and C60 interface and thus reducing *** a result,a 2-T PVK/CIGS tandem yielded a power conversion efficiency of 24.6%(0.16 cm^(2)),one of the highest results for 2-T PVK/CIGS TSCs to our *** validation underscores the potential of our methodology in achieving superior performance in PVK/CIGS tandem solar cells.

关键词： PVK/CIGS TSCs Irregular rough surfaces Modulating the growth PVK/C60 interface recombination

The Study on Effect of Exhaust Performance According to Active Muffler Valve Spring as Followed Spring Constant

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Journal of Thermal Science 2002年第4期11卷 372-377页

作者： Seuk Cheun Choi Tae Woo Kong han shik chung Hyo Min Jeong Young Heung Chun Graduate School of Mechanical and Precision Engineering Gyeongsang National UniversityInpyeongdong 445 Tongyong Kyongnam 650-160Korea School of Transport Vehicle Engineering Gyeongsang National UniversityThe Institute of Marine IndustryInpyeongdong 445 Tongyong Kyongnam 650-160Korea

This study represents the influence on exhaust performance by active muffler valve *** main experimental parameters were engine speeds and torsion coil spring constants in the active *** the muffler valve spring has a low spring constant of k=0.75,the sound pressure level was low at the region of engine speed 2000 to 2500 r/min,and the velocity of exhaust gas was high at spring constant k=*** the engine speed was under 1500 r/min,the mean concentration of CO was high in case without muffler *** the engine speed in the range of 1600 to 2600 r/min with spring constant k=0.75,the mean HC concentration showed the lowest *** muffler valve,the temperature in the muffler was higher than the case with muffler *** research represented that the performance of the active muffler valve spring constant k=0.75 was higher than that without muffler valve and valve spring constant k=*** the three cases of experimental condition,with a spring constant k=0.75,0.70 and without muffler valve,the exhaust performance was high in case active muffler valve spring constant k=0.70.

关键词： active muffler torsion coil spring spring constant sound pressure level

A Power-Aware Branch Predictor by Accessing the BTB Selectively

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Journal of Computer Science & Technology 2005年第5期20卷 607-614页

作者： Cheol Hong Kim Sung Woo chung Chu shik Jhon Mobile System Laboratory Department of Electrical Engineering and Computer Science Seoul National University Seoul 151-742 Korea Department of Computer Science University of Virginia Charlottesville Virginia 22904 U.S.A.

Microarchitects should consider power consumption, together with accuracy, when designing a branch predictor, especially in embedded processors. This paper proposes a power-aware branch predictor, which is based on the gshare predictor, by accessing the BTB （Branch Target Buffer） selectively. To enable the selective access to the BTB, the PHT （Pattern History Table） in the proposed branch predictor is accessed one cycle earlier than the traditional PHT if the program is executed sequentially without branch instructions. As a side effect, two predictions from the PHT are obtained through one access to the PHT, resulting in more power savings. In the proposed branch predictor, if the previous instruction was not a branch and the prediction from the PHT is untaken, the BTB is not accessed to reduce power consumption. If the previous instruction was a branch, the BTB is always accessed, regardless of the prediction from the PHT, to prevent the additional delay/accuracy decrease. The proposed branch predictor reduces the power consumption with little hardware overhead, not incurring additional delay and never harming prediction accuracy. The simulation results show that the proposed branch predictor reduces the power consumption by 29-47%.

关键词： branch predictor BTB embedded processor low power design PHT

Kinetics study on photochemical oxidation of polyacrylamide by ozone combined with hydrogen peroxide and ultraviolet radiation

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Journal of Environmental Sciences 2006年第4期18卷 660-664页

作者： REN Guang-meng SUN De-zhi chung Jong shik School of Municipal and Environmental Engineering Harbin Institute of Technology Harbin 150090 China Department of Chemical Engineering Pohang University of Science and Technology Pohang 790-784 South Korea

An investigation on the process of ozone combined with hydrogen peroxide and ultraviolet radiation has been carried out in order to establish the kinetics for photochemical oxidation of polyacrylamide （PAM） in aqueous solution. Effects of operating parameters, including initial PAM concentration, dosages of ozone and hydrogen peroxide, UV radiation and pH value on the photochemical oxidation of PAM, have been studied. There was an increase in photochemical oxidation rate of PAM with increasing of dosages of 03, H2O2 and ultraviolet radiation. Upon increasing of the initial PAM concentration, the photochemical oxidation rate of PAM decreased. Slight effect of pH value on the photochemical oxidation rate of PAM was observed in the experiments. The kinetics equation for the photochemical oxidation of PAM by the system has been established.

关键词： photochemical oxidation polyacrylamide kinetics ozone/hydrogen peroxide/ultraviolet radiation

Modeling and Adaptive Neural Network Control for a Soft Robotic Arm With Prescribed Motion Constraints

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IEEE/CAA Journal of Automatica Sinica 2023年第2期10卷 501-511页

作者： Yan Yang Jiangtao han Zhijie Liu Zhijia Zhao Keum-shik Hong the School of Intelligence Science and Technology University of Science and Technology BeijingBeijing 10083 the Institute of Artificial Intelligence University of Science and Technology BeijingBeijing 100083China IEEE the School of Mechanical and Electrical Engineering Guangzhou UniversityGuangzhou 510006China the School of Mechanical Engineering Pusan National UniversityBusan 46241South Korea

This paper presents a dynamic model and performance constraint control of a line-driven soft robotic *** dynamics model of the soft robotic arm is established by combining the screw theory and the Cosserat *** unmodeled dynamics of the system are considered,and an adaptive neural network controller is designed using the backstepping method and radial basis function neural *** stability of the closed-loop system and the boundedness of the tracking error are verified using Lyapunov *** simulation results show that our approach is a good solution to the motion constraint problem of the line-driven soft robotic arm.

关键词： Adaptive control cosserat theory prescribed motion constraints soft robotic arm