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High Temperature Mechanical Properties of Ni-Al-Cr Based Alloys for Advanced die-Materials Applications

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Journal of Materials Science & Technology 2008年第3期24卷 305-308页

作者： W.Y.kim H.S.kim Y.G.Yoo I.d.Yeo Advanced Materials R&d division Korea Institute of Industrial Technology7-47Songdo-dongYeonsu-gu

In this study, we report on advanced Ni3Al based high temperature structural alloys with Zr and B addition in order to apply in the fields of die-casting and high temperature press forming as die materials. Microstructures and mechanical properties of Ni3Al based intermetallic alloys produced by vacuum arc melting were investigated in terms of phase analysis by using a scanning electron microscope （SEM） equipped with an X-ray energy dispersive spectrometer （EdS）, an X-ray diffractometer （XRd） and tensile test. The duplex microstructural feature consisting of γ＇ matrix phase and small intermetallic dispersoids was observed to be distributed over the whole microstructure. The ultimate tensile strength of the present alloy was superior to commercial iron-based and Ni-based die-materials especially in the high temperature region.

关键词： Intermetallic die material Alloying effect Mechanical property

Effects of Mo and Zr on Microstructure,Mechanical Properties and Wear Resistance of Fe-Al Based Alloys

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Journal of Materials Science & Technology 2008年第3期24卷 309-312页

作者： I.d.Yeo H.S.kim Y.G.Yoo W.Y.kim Advanced Materials R&d division Korea Institute of Industrial Technology7-47Songdo-dongYeonsu-gu

In this work the microstructure, mechanical properties and wear resistance of Fe-Al based alloys with various alloying elements were studied. The microstructures were examined by optical and scanning electron microscopy （SEM） equipped with an energy dispersive X-ray spectroscope （EdS）. Two types of alloys were prepared by vacuum arc melting. One is Fe-28Al based alloys （d03 structured） with and without alloying elements such as Mo and Zr. The other one is Fe-35Al based alloys （B2 structured） produced with the same manner. For both types of alloys, Mo addition had found to exhibit an equiaxed microstructure, while dendritic structure was observed to show the effect of Zr addition. These microstructural features were more evinced with increasing content of alloying element. Concerning the mechanical properties and wear resistance, Fe-35Al based alloys were superior to Fe-28Al based alloys over the whole temperature range investigated.

关键词： Fe-Al alloy Intermetallic Mechanical properties Wear resistance

Study of Thermal and Hydraulic Performances of Circular and Square Ribbed Rough Microchannels Using LBM

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Journal of Thermal Science 2015年第6期24卷 549-556页

作者： M.A.Taher H.d.kim Y.W Lee department of Mechanical and Automotive Engineering Pukyong National University department of Mechanical Engineering Andong National University

The effects of roughness geometries and relative roughness height at the slip flow regime to investigate the thermal and hydraulic performances of microchannel have been considered in the present article using a thermal Lattice Boltzmann Method(TLBM).A two dimensional 9-bit(d2Q9)single relaxation time(SRT)model is used to simulate this *** micro-flows,the local density variation is still relatively small,but the total density changes,therefore,in order to account this density variation and its effect on the kinematic viscosityν,a new relaxation time proposed by Niu et al.[13]is *** roughness geometry is modeled as a series of square and circular riblets with a relative roughness height from 0%to 10%of the channel *** friction coefficients in terms of Poiseuille number(Pn)and the dimensionless heat transfer rate in terms of Nusselt number(Nu)have been discussed in order to analyze the roughness *** thermal-hydraulic performance(η)is calculated considering the simultaneous effects of thermal and fluid friction(pressure drop)at the slip flow regime at Knudsen number,Kn,ranging from 0.01 to 0.10 with other controlling parameters for both kind of *** results have been compared with previous published works and it is found to be in very good agreement.

关键词： Lattice-Boltzmann Friction factor Knudsen number Surface Roughness

Purification,application and current market trend of natural graphite:A review

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International Journal of Mining Science and Technology 2019年第5期29卷 671-689页

作者： Allah d.Jara Amha Betemariam Girma Woldetinsae Jung Yong kim School of Materials Science and Engineering Jimma Institute of TechnologyJimma UniversityJimma P.O.Box 378Ethiopia defense Engineering College Bishoftu P.O.Box 1041Ethiopia The Ministry of Mines Petroleum and Natural GasAddis Ababa P.O.Box 486Ethiopia School of Chemical Engineering Jimma Institute of TechnologyJimma UniversityJimma P.O.Box 378Ethiopia

Graphite has a stacked planar sp2-hybridized C6 ring structure,displaying a polymorphism with rhombohedral,hexagonal,and *** on its structure-property relationship,it affords a variety of technologically innovative applications or performances in industries,such as lithium-ion batteries,fuel cells,two dimensional graphene,water purification,electronics,fiber optics,spintronics,refractories,electrical products,electric vehicles,*** monetary value of graphite depends largely on carbon content and flake ***,the physical separation of graphite from its ore body is known to be very expensive,energy intensive and ***,this study extensively describes a current purification method for producing high-quality graphite material with impurities reaching about 10–100 mg/kg,attracting a lot of end *** also describes the potential applications of graphite materials and identifies the future scope of a new market,depending on material ***,the current and future graphite-mining countries are investigated in details.

关键词： Graphite Purification Graphene Lithium-ion battery Market Technology

MOLECULAR dESIGN OF LIGHT EMITTING POLYMERS

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Chinese Journal of Polymer Science 2000年第3期18卷 227-237页

作者： J.W.Yu J.K.kim J.MHong Y.C.kim H.N.Cho d.Y.kim C.Y.kim Polymer Materials Laboratory Korea Institute of Science and TechnologyP.O.Box 131CheongryangSeoul 130-650.Korea

Fluorene-based alternating and statistical copolymers were synthesized by employing reaction methods of Wittig,Heck and *** copolymers were classified into three groups with the photoluminescence(PL)emission maxima at420,475 and 500 nm,*** copolymers with two chromophores having PL emission maxima at 420 and475 nm emitted light with the emission maximum at 475 nm on photoexcitation at 365 nm and improved the quantumefficiency by the energy ***,the intramolecular energy transfer was inefficient compared to the intermolecularenergy transfer when the two chromophores were apart from each other in the range of the Forster critical ***-pyridinedivinylene alternating copolymer was synthesized by the Wittig reaction and found to have physical,electronic andelectrochemical properties of the individual units *** double-layered light emitting diode(LEd)with the statisticalcopolymer as an emitting layer and the pyridine-containing copolymer as an electron transporting-hole blocking layer,whichwere sandwiched between ITO and Al,displayed a quantum efficiency of 0.1%.

关键词： Light emitting polymers

Optimization Study of a Coanda Ejector

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Journal of Thermal Science 2006年第4期15卷 331-336页

作者： H.d.kim G.Rajesh T.Setoguchi S.Matsuo School of Mechanical Engineering Andong National University388Songcheon-dongAndongGyeongbuk 760-749Korea department of Mechanical Engineering Saga University1HonjoSaga 840-8502Japan

The Coanda effect has long been employed in the aerospace applications to improve the performances of various devices. This effect is the ability of a flow to follow a curved contour without separation and has well been utilized in ejectors where a high speed jet of fluid emerges from a nozzle in the ejector body, follows a curved surface and drags the secondary flow into the ejector. In Coanda ejectors, the secondary flow is dragged in the ejector due to the primary flow momentum. The transfer of momentum from the primary flow to the secondary flow takes place through turbulent mixing and viscous effects. The secondary flow is then dragged by turbulent shear force of the ejector while being mixed with the primary flow by the persistence of a large turbulent intensity throughout the ejector. The performance of a Coanda ejector is studied mainly based on how well it drags the secondary flow and the amount of mixing between the two flows at the ejector exit. The aim of the present study is to investigate the influence of various geometric parameters and pressure ratios on the Coanda ejector performance. The effect of various factors, such as, the pressure ratio, primary nozzle and ejector configurations on the system performance has been evaluated based on a performance parameter defined elsewhere. The performance of the Coanda ejector strongly depends on the primary nozzle configuration and the pressure ratio. The mixing layer growth plays a major role in optimizing the performance of the Coanda ejector as it decides the ratio of secondary mass flow rate to primary mass flow rate and the mixing length.

关键词： Coanda ejector compressible mixing layer flow dragging mixing length induced flow

The H∞ Robust Stability and Performance Conditions for Uncertain Robot Manipulators

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IEEE/CAA Journal of Automatica Sinica 2025年第1期 270-272页

作者： Geun Il Song Hae Yeon Park Jung Hoon kim the department of Electrical Engineering Pohang University of Science and Technology (POSTECH) the department of Electrical Engineering Pohang University of Science and Technology (POSTECH) the Institute for Convergence Research and Education in Advanced Technology Yonsei University

dear Editor,H∞This letter develops a new framework for the robust stability and performance conditions as well as the relevant controller synthesis with respect to uncertain robot *** often exist model uncertainties between the nominal model and the real robot manipulator and disturbances. Hence, dealing with their effects plays a crucial role in leading to high tracking performances, as discussed in [1]–[5].

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dynamic behavior of stormwater quality parameters in South Texas

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Frontiers of Environmental Science & Engineering 2012年第6期6卷 825-830页

作者： Xubin PAN Jingyi ZHANG Wei-Ta FANG kim d.JONES Institute of Plant Quarantine Chinese Academy of Inspection and QuarantineBeijing 100029China department of Environmental Engineering Texas A&M University-KingsvilleKingsvilleTX 78363USA Graduate Institute of Environmental Education Taiwan Normal UniversityTaipei 116China

To control water impairment in urban storm- water, it is important to evaluate changing patterns of water quality parameters in stormwater runoff. Thus, the authors performed a series of experiments to investigate the dynamics of common water parameters during storm events in semi-arid areas, with multiple samples collected and analyzed in field stormwater applications. At this field monitoring site within McAuliffe Park, McAllen, Texas, in the United States, a storm event increased the concentra- tions of Escherichia coli （E. coli）, but this event represented a decreasing trend over the entire event period. Besides, peak intensity of different pollutants in the stormwater runoff occurred at different times other than at any peak flows, representing a complexity of the temporal and spatial measurements. Multi-sample per- event approaches recommended based on the complexity of the hydrograph and different peak intensity times of pollutants. In addition, high bacteria and total suspended solids （TSS） concentrations in the initial stage of the storm event should be considered when designing Best Manage- ment Practices （BMPs） and Low Impact developments （LIds）. New strategies and solutions for addressing ecohydrological challenges should be proposed to avoid collateral damages to their both common wealth in ecosystems and human well-beings.

关键词： event mean concentration first flush multi-sample per event ecohydrology

Molecular dynamics Simulation for Grain Boundary deformation under Tensile Loading Condition

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Journal of Materials Science & Technology 2001年第1期17卷 145-146页

作者： kim, Y.S. Choi, d.Y. Won, S.Y. dep. of Mech. Eng. Kyungpook Natl. Univ. Kyungpook South Korea

Md (molecular dynamics) simulations have been performed to observe the behavior of a grain boundary in the α-Fe plate under 2-dimensional loading. In Md simulation, the acceleration of every molecule can be achieved from the potential energy and the force interaction between this molecule and other molecules , and the integration of the motion equation by using Verlet method gives the displacement of each molecule. Initially, four α-Fe rectangular plates having different misorientation angles of the grain boundary are modeled by using the Johnson potential and the Morse potential. The potential energy of the grain boundary system is compared with that of the perfect structure model. Also, the width of the grain boundary can be obtained by investigating the local potential energy distribution. The tensile loading for each grain boundary model is applied and the behavior of the grain boundary is studied. From this study it is clarified that in the case of using the Johnson potential, the obvious fracture mechanism occurs along the grain boundary, and in the case of using the Morse potential, the diffusion of the grain boundary appears instead of the grain boundary fracture.

关键词： Simulation Molecular dynamics Simulation for Grain Boundary deformation under Tensile Loading Condition