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Material Characterization of Ni Base Alloy for Very High Temperature Reactor

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Journal of Materials Science & Technology 2013年第12期29卷 1184-1190页

作者： Dong-jin kim Gyeong-Geun Lee Dae Jong kim Su jin Jeong Nuclear Materials Division Korea Atomic Energy Research Institute

The generation of highly efficient electricity and the production of massive hydrogen are possible using a very high temperature reactor （VHTR） among generation IV nuclear power plants. The structural material for an intermediate heat exchanger （IHX） among numerous components should be endurable at high temperature of up to 950 °C during long-term operation. Impurities inevitably introduced in helium as a coolant facilitate the material degradation by corrosion at high temperature. In the present work, the surface reactions available under controlled impure helium at 950 °C were investigated based on the thermodynamics and the corrosion tests were performed in a temperature range of 850-950 °C during 10-250 h for commercial Alloy 617 as a candidate material for an IHX. Moreover, the mechanical property and microstructure for nickel-based alloys fabricated in laboratory were evaluated as a function of the processing parameters such as hot rolling and heat treatment conditions. From the reaction rate constant obtained from an impure helium control system for a material evaluation, it was predicted that the outer oxide layer thickness, internal oxide depth, and carbide- depleted zone depth reach about 116, 600 and 1000 μm, respectively when Alloy 617 is exposed to an impure helium environment at 950 ~C for 20 years. For Ni-Cr-Co-Mo alloy, subsequent annealing and a combination of cold working and subsequent annealing following solution annealing caused increases in the grain boundary carbide coverage and size. The angular distribution of the grain boundary as well as the carbide distribution was also changed leading to a consequent improvement of the mechanical property at 950 °C in air.

关键词： Nickel base alloy Intermediate heat exchanger High temperature reactor Corrosion Mechanical property

Super-resolution localization photoacoustic microscopy using intrinsic red blood cells as contrast absorbers

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Light(Science & Applications) 2019年第1期8卷 212-222页

作者： Jongbeom kim jin Young kim Seungwan Jeon jin Woo BAIK Seong Hee Cho Chulhong kim Departments of Creative IT Engineering Electrical EngineeringMechanical Engineeringand Interdisciplinary Bioscience and BioengineeringPohang University of Science and Technology(POSTECH)77 Cheongam-roNam-guPohangGyeongbuk 37673Republic of Korea

Photoacoustic microscopy(PAM)has become a premier microscopy tool that can provide the anatomical,functional,and molecular information of animals and humans in ***,conventional PAM systems suffer from limited temporal and/or spatial ***,we present a fast PAM system and an agent-free localization method based on a stable and commercial galvanometer scanner with a custom-made scanning mirror(L-PAM-GS).This novel hardware implementation enhances the temporal resolution significantly while maintaining a high signal-to-noise ratio(SNR).These improvements allow us to photoacoustically and noninvasively observe the microvasculatures of small animals and humans in ***,the functional hemodynamics,namely,the blood flow rate in the microvasculature,is successfully monitored and quantified in *** importantly,thanks to the high SNR and fast B-mode rate(500 Hz),by localizing photoacoustic signals from captured red blood cells without any contrast agent,unresolved microvessels are clearly distinguished,and the spatial resolution is improved by a factor of 2.5 in ***-GS has great potential in various fields,such as neurology,oncology,and pathology.

关键词： resolution absorber scanner

Physical Experiments to Investigate the Effects of Street Bottom Heating and Inflow Turbulence on Urban Street-Canyon Flow

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Advances in Atmospheric Sciences 2005年第2期22卷 230-237页

作者： Jae-jin kim Jong-jin BAIK Climate Environment System Research Center Seoul National University Seoul 151-742 KoreaSchool of Earth and Environmental Sciences Seoul National University Seoul 151-742 Korea

The effects of street bottom heating and inflow turbulence on urbanstreet-canyon flow are experimentally investigated using a circulating water channel. Threeexperiments are carried out for a street canyon with a street aspect ratio of 1. Results from eachexperiment with bottom heating or inflow turbulence are compared with those without bottom heatingand appreciable inflow turbulence. It is demonstrated that street bottom heating or inflowturbulence increases the intensity of the canyon vortex. A possible explanation on how street bottomheating or inflow turbulence intensifies the canyon vortex is given from a fluid dynamicalviewpoint.

关键词： urban street-canyon flow street bottom heating inflow turbulence circulating water channel

Fruit quality,anthocyanin and total phenolic contents,and antioxidant activities of 45 blueberry cultivars grown in Suwon,Korea

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Journal of Zhejiang University-Science B(Biomedicine & Biotechnology) 2013年第9期14卷 793-799页

作者： jin Gook kim Hong Lim kim Su jin kim Kyo-Sun PARK Department of Horticulture College of Agriculture and Life SciencesGyeongsang National University Institute of Agriculture and Life Sciences Gyeongsang National University Namhae Sub-Station National Institute of Horticultural and Herbal Science Fruit Research Division National Institute of Horticultural and Herbal Science

Blueberry fruits from 45 commercial cultivars (39 northern highbush and 6 half highbush blueberry) grown in Suwon,Korea were analyzed for fruit size,soluble solids content,titratable acidity,total anthocyanin content,total phenolic content,and antioxidant *** characteristics varied widely among the 45 blueberry *** weight ranged from 0.9 to 3.6 g,soluble solids content from 8.3 to 14.3 °Brix,and titratable acidity from 0.8% to 3.6%.Antioxidant activity ranged from 0.7 to 2.1 mg of quercetin equivalents per gram of fresh berries in different blueberry *** the 45 blueberry cultivars,high amounts of anthocyanins and polyphenols,and high antioxidant activity were observed in 'Elliott','Rubel','Rancocas',and 'Friendship'.

关键词： Northern highbush blueberry Half highbush blueberry Functional food Fruit quality

Effect of reduction in area per pass on strain distribution and microstructure during caliber rolling in twinning-induced plasticity steel

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Journal of Iron and Steel Research International 2020年第1期27卷 62-74页

作者： Joong-ki Hwang Sung jin kim School of Mechanical Engineering Tongmyong UniversityBusan 48520Republic of Korea Department of Advanced Materials Engineering Sunchon National UniversitySuncheon 57922Republic of Korea

The effects of reduction in area(RA)per pass during caliber rolling on microstructure and strain distribution of twinninginduced plasticity steel have been investigated to find solutions to make a more homogeneous material along the radial direction for wire rod *** steel wires subjected to an average RA per pass of 2.5%(skin pass caliber rolling)and 10.0%(conventional caliber rolling)were *** skin pass caliber-rolled wire was characterized as a duplex fiber texture of majorand minor.and the textures were almost same at/between center and surface area,which is totally different from those of conventional caliber rolling and wire *** skin pass caliber rolling led to more homogeneous microstructure and mechanical properties along the radial direction in comparison with the conventional caliber rolling and wire drawing due to the more homogeneous Hall-Petch hardening,dislocation hardening,and texture behavior with area,resulting in higher formability.

关键词： Twinning-induced plasticity steel Caliber rolling Deformation twin Reduction in area Skin pass

Effects of a Building’s Density on Flow in Urban Areas

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Advances in Atmospheric Sciences 2009年第1期26卷 45-56页

作者： Jae-jin kim Do-Yong kim Department of Environmental Atmospheric Sciences Pukyong National University Busan Korea Center for Atmosphere Science and Earthquake Research Korea Meteorological Administration Busan Korea

The effects of a building＇s density on urban flows are investigated using a CFD model with the RNG k - ε turbulence closure scheme. Twenty-seven cases with different building＇s density parameters （e.g., building and street-canyon aspect ratios） are numerically simulated. As the building＇s density parameters vary, different flow regimes appear. When the street canyon is relatively narrow and high, two counterrotating vortices in the vertical direction are generated. The wind speed along streets is mainly affected by the building＇s length. However, it is very difficult to find or generalize the characteristics of the street-canyon flows in terms of a single building＇s density parameter. This is because the complicated flow patterns appear due to the variation of the vortex structure and vortex number. Volume-averaged vorticity magnitude is a very good indicator to reflect the flow characteristics despite the strong dependency of flows on the variation of the building＇s density parameters. Multi-linear regression shows that the volume-averaged vorticity magnitude is a strong function of the building＇s length and the street-canyon width. The increase in the building＇s length decreases the vorticity of the street-canyon flow, while, the increase in the street- canyon width increases the vorticity.

关键词： urban flow characteristics building's density parameter volume-averaged vorticity CFD model

Environmental Sound Event Detection in Wireless Acoustic Sensor Networks for Home Telemonitoring

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China Communications 2017年第9期14卷 1-10页

作者： Hyoung-Gook kim jin Young kim The Dept. of Electronics Convergence Engineering Kwangwoon University The Dept. of Electronics and Computer Engineering Chonnam National University

In this paper, we present an approach to improve the accuracy of environmental sound event detection in a wireless acoustic sensor network for home monitoring. Wireless acoustic sensor nodes can capture sounds in the home and simultaneously deliver them to a sink node for sound event detection. The proposed approach is mainly composed of three modules, including signal estimation, reliable sensor channel selection, and sound event detection. During signal estimation, lost packets are recovered to improve the signal quality. Next, reliable channels are selected using a multi-channel cross-correlation coefficient to improve the computational efficiency for distant sound event detection without sacrificing performance. Finally, the signals of the selected two channels are used for environmental sound event detection based on bidirectional gated recurrent neural networks using two-channel audio features. Experiments show that the proposed approach achieves superior performances compared to the baseline.

关键词： sound event detection wirelesssensor network gated recurrent neural net-work multichannel audio

High-efficiency design of a mixed-flow pump

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Science China(Technological Sciences) 2010年第1期53卷 24-27页

作者： kim jin-Hyuk AHN Hyung-jin kim Kwang-Yong Department of Mechanical Engineering Inha University253Yonghyun-DongIncheon402-751Republic of Korea Industrial Machinery Division Iljin Electric Co.Ltd5-5Hwasu-DongIncheon401-020Republic of Korea

High-efficiency design of a mixed-flow pump has been carried out based on numerical analysis of a three-dimensional viscous *** analysis,the Reynolds-averaged Navier-Stokes equations with a shear stress transport turbulence model were discretized by finite-volume *** grid system was constructed in the computational domain,which has O-type grids near the blade surfaces and H/J-type grids in other *** numerical results were validated with experimental data for the heads and hydraulic efficiencies at different flow *** hydraulic efficiency at the design flow coefficient was evaluated with variation of the geometric variables,i.e.,the area of the discharge and length of the vane in the *** result has shown that the hydraulic efficiency of a mixed-flow pump at the design condition is improved by the modification of the geometry.

关键词： mixed-flow pump numerical analysis impeller vane diffuser head hydraulic efficiency

REVIEW 6G and Internet of Things:a survey

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Journal of Management Analytics 2021年第2期8卷 316-332页

作者： jin Ho kim College of Business Lewis UniversityRomeovilleILUSA

The 5G networks which have begun to spread worldwide are expected to contribute to an increase in the use of Internet of Things(IoT)technologies and applications,which require massive connectivity,security,and ultra-low ***,it is known that 5G alone is not sufficient for many IoT devices to exchange various types of data in real *** constraints promote the emergence of 6G technologies which can support higher network capacity,lower latency,and faster data transmission than 5G *** understand the current trends in 6G research and their relation to IoT,this paper introduces the main drivers of 6G technology,describes 6G’s enabling technologies,summarizes current 6G research,and introduces the possible applications of 6G to IoT technologies and service areas.

关键词： 6G Internet of Things IoT terahertz extended reality