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Journal of Thermal Science 2007年第2期16卷 134-139页

作者： Shigeru MATSUO Kenbu TERAMOTO Miah MD.Ashraful ALAM Toshiaki SETOGUCHI Heuy dong kim Shen yu Department of Mechanical Engineering Saga University1Honjo-machiSaga-shiSaga 840-8502Japan Department of Mechanical Engineering Khulna University of Engineering & TechnologyKhulna-9203Bangladesh School of Mechanical Engineering Andong National University388Songchun-dongAndong 760749Korea Institute of Engineering Thermophysics Chinese Academy of SciencesP.O.Box 2706Beijing 100080China

The unsteady phenomena in the transonic flow around airfoils are observed in the flow field of fan, compressor blades and butterfly valves, and this often causes serious problems such as the aeroacoustic noise, the vibration. In the transonic or supersonic flow where vapour is contained in the main flow, the rapid expansion of the flow may give rise to a non-equilibrium condensation. However, the effect of non-equilibrium condensation on the transonic internal flows around the airfoil has not yet been clarified satisfactorily. In the present study, the effect of non-equilibrium condensation of moist air on the self-excited shock wave oscillation on a circular arc blade was investigated numerically. The results showed that in the case with non-equilibrium condensation, frequencies of the flow oscillation became smaller than those without the non-equilibrium condensation.

关键词： compressible flow transonic flow shock wave oscillation non-equilibrium condensation simulation

Effects of Cr doping on structural and electrochemical properties of Li_(4)Ti_(5)O_(12) nanostructure for sodium-ion battery anode

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Journal of Energy Chemistry 2021年第8期30卷 465-472,I0010页

作者： Sang Hyuk Gong Ji Hyeon Lee dong Won Chun Jee-Hwan Bae Sung-Chul kim Seungho yu Sahn Nahm Hyung-Seok kim Center for Energy Storage Research Korea Institute of Science and Technology5Hwarang-ro 14-gilSeongbuk-gu02792 SeoulRepublic of Korea Department of Materials Science and Engineering Korea University145Anam-roSeongbuk-gu02841 SeoulRepublic of Korea Department of Chemical and Biological Engineering Korea University145Anam-roSeongbuk-gu02841 SeoulRepublic of Korea Advanced Analysis Center Korea Institute of Science and Technology5Hwarang-ro 14-gilSeongbuk-gu02792 SeoulRepublic of Korea

Sodium-ion batteries are considered as promising alternatives to lithium-ion batteries,owing to their low cost and abundant raw *** the several candidate materials for the anode,spinel-type Li_(4)Ti_(5)O_(12)has potential owing to its superior safety originating from an appropriate operating voltage and the reversible Na^(+)intercalation ***,a low diffusion coefficient for Na^(+)and the insulating nature of LTO remains challenging for practical sodium-ion battery ***,we present a strategy for integrating physical and chemical approaches to achieve superior electrochemical properties in *** demonstrate that carefully controlling the amount of Cr doping is crucial to enhance the electrochemical properties of nanostructured *** Cr doped LTO shows a superior reversible capacity of 110 m Ah g^(-1) after 400 cycles at 1 C,with a three-fold higher capacity(75 m Ah g^(-1))at 10 C compared with undoped LTO *** suggests that appropriately Cr doped nanostructured LTO is a promising anode material for sodium-ion batteries.

关键词： Sodium-ion batteries Spinel type Li_(4)Ti_(5)O_(12) Anode materials Nanostructuring Cr-doping

Additive manufacturing of flexible 3D surface electrodes for electrostatic adhesion control and smart robotic gripping

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Friction 2023年第11期11卷 1974-1986页

作者： dong Geun kim Hyeongmin JE AJohn HART Sanha kim Department of Mechanical Engineering Korea Advanced Institute of Science and TechnologyDaejeon 34141Republic of Korea Department of Mechanical Engineering Massachusetts Institute of TechnologyCambridgeMA 02139USA

Mechanically flexible surface structures with embedded conductive electrodes are attractive in contact-based devices,such as those used in reversible dry/adhesion and tactile *** shapes of the surface structures strongly determine the contact behavior and therefore the resulting adhesion and sensing functionalities;however,available features are often restricted by fabrication ***,we additively manufacture elastomeric structure arrays with diverse angles,shapes,and sizes;this is followed by integration of conductive nanowire *** fabricated flexible three-dimensional(3D)surface electrodes are mechanically compliant and electrically conductive,providing multifunctional ability to sense touch and to switch adhesion via a combined effect of shear-and electro *** designed soft,anisotropic flexible structures to mimic the gecko’s reversible adhesion,which is governed by van der Waals forces;we integrated nanowires to further manipulate the localized electric field among the adjacent flexible 3D surface electrodes to provide additional means to digitally tune the electrostatic attraction at the contact *** addition,the composite surface can sense the contact force via capacitive *** our flexible 3D surface electrodes,we demonstrate a complete soft gripper that can grasp diverse convex objects,including metal,ceramic,and plastic products,as well as fresh fruits,and that exhibits 72%greater electroadhesive gripping force when voltage is applied.

关键词： electroadhesion tactile sensing robotic gripper additive manufacturing dry adhesive

Dynamic soil-structure interaction analysis in time domain based on a modified version of perfectly matched discrete layers

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Journal of Rock Mechanics and Geotechnical Engineering 2020年第1期12卷 168-179页

作者： dong Van Nguyen Dookie kim Department of Civil Engineering Kunsan National University558 Daehak-roGunsan-si54150Republic of Korea

Analysis of soil-structure interaction is commonly conducted by dividing the infinite domain of the soil into two domains:interior and exterior *** interior domain is bounded in a small region,while the exterior domain is replaced by artificial boundary *** choice of artificial boundary conditions is a critical issue in the analysis of soil-structure interaction *** matched discrete layer(PMDL)has been proved as a good approach for modeling the exterior *** this study,a modified version of the PMDLs,*** with analytical wavelengths(AW-PMDLs),is used in the soil-structure interaction analysis in time domain,which essentially can be regarded as an extension of the analysis in frequency domain,being previously proven to be *** verifications are *** results demonstrate that the proposed method performs well in the analysis of soilstructure interaction problems in time domain.

关键词： Soil-structure interaction Time domain Wave propagation Wavelength Infinite domain Perfectly matched discrete layer(PMDL)

Shear deformable finite beam elements for composite box beams

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Acta Mechanica Sinica 2014年第2期30卷 223-240页

作者： Nam-Il kim dong-Ho Choi Department of Architectural Engineering Sejong University Department of Civil and Environmental Engineering Hanyang University

The shear deformable thin-walled composite beams with closed cross-sections have been developed for coupled flexural, torsional, and buckling analyses. A theoretical model applicable to the thin-walled laminated composite box beams is presented by taking into account all the structural couplings coming from the material anisotropy and the shear deformation effects. The current composite beam includes the transverse shear and the restrained warping induced shear deformation by using the first-order shear deformation beam theory. Seven governing equations are derived for the coupled axial-flexural-torsional-shearing buckling based on the principle of minimum total potential energy. Based on the present analytical model, three different types of finite composite beam elements, namely, linear, quadratic and cubic elements are developed to analyze the flexural, torsional, and buckling problems. In order to demonstrate the accuracy and superiority of the beam theory and the finite beam elements developed by this study,numerical solutions are presented and compared with the results obtained by other researchers and the detailed threedimensional analysis results using the shell elements of ABAQUS. Especially, the influences of the modulus ratio and the simplified assumptions in stress-strain relations on the deflection, twisting angle, and critical buckling loads of composite box beams are investigated.

关键词： Thin-walled Composite box beam Deflection Twisting angle Buckling load Shear deformation

Study on the Wiping Gas Jet in Continuous Galvanizing Line

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Journal of Thermal Science 2011年第3期20卷 242-247页

作者： Yong-Hun Kweon Heuy-dong kim POSCO Technical Research Laboratories 699 Gumho-dong GwangyangJeonnam 545-090 Korea School of Mechanical Engineering Andong National UniversityAndong 760-749 Korea

In the continuous hot-dip galvanizing process, the gas-jet wiping is used to control the coating thickness of moving steel strip. The high speed gas-jet discharged from the nozzle slot impinges on the strip, and at this moment, wipes the liquid coating layer dragged by a moving strip. The coating thickness is generally influenced on the flow characteristics of wiping gas-jet such as the impinging pressure distribution, pressure gradient and shear stress distribution on the surface of strip. The flow characteristics of wiping gas-jet mentioned above depends upon considerably both the process operating conditions such as the nozzle pressure, nozzle-to-strip distance and line speed, and the geometry of gas-jet wiping apparatus such as the height of nozzle slot. In the present study, the effect of the geometry of nozzle on the coating thickness is investigated with the help of a computational fluid dynamics method. The height of nozzle slot is varied in the range of 0.6mm to 1.7mm. A finite volume method (FVM) is employed to solve two-dimensional, steady, compressible Navier-Stokes equations. Based upon the results obtained, the effect of the height of nozzle slot in the gas-jet wiping process is discussed in detail. The computational results show that for a given standoff distance between the nozzle to the strip, the effective height of nozzle slot exists in achieving thinner coating thickness.

关键词： Gas-Jet Wiping Hot-Dip Galvanizing Impact Pressure Coating Thickness

CHEBYSHEV WEIGHTED NORM LEAST-SQUARES SPECTRAL METHODS FOR THE ELLIPTIC PROBLEM

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Journal of Computational Mathematics 2006年第4期24卷 451-462页

作者： Sang dong kim Byeong Chun Shin Department of Mathematics Kyungpook National University Taegu 702-701 Korea Department of Mathematics Chonnam National University Kwangju 500-757 Korea

We develop and analyze a first-order system least-squares spectral method for the second-order elhptic boundary value problem with variable coefficients. We first analyze the Chebyshev weighted norm least-squares functional defined by the sum of the Lw^2- and Hw^-1- norm of the residual equations and then we eplace the negative norm by the discrete negative norm and analyze the discrete Chebyshev weighted least-squares method. The spectral convergence is derived for the proposed method. We also present various numerical experiments. The Legendre weighted least-squares method can be easily developed by following this paper.

关键词： Least-squares methods Spectral method Negative norm.

Weldability evaluation and tensile strength estimation model for aluminum alloy lap joint welding using hybrid system with laser and scanner head

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中国有色金属学会会刊：英文版 2012年第S3期22卷 596-604页

作者： dong-Yoon kim Young-Whan PARK Department of Mechanical Engineering Pukyong National University

Aluminum welding using a hybrid system with a laser and scanner welding head was performed under various welding conditions to verify the feasibility of applying an aluminum alloy to a car *** experimental material was 5J32 aluminum alloy,and the laser power,welding speed,and laser incidence angle were used as the control *** weld bead shape and the tensile shear strength were evaluated in order to understand the aluminum lap joint weld *** of variance (ANOVA) was conducted to identify the effect of the process variables on the tensile shear *** strength estimation models using three different regression models were also *** input variables were the laser power,welding speed,and laser incidence angle,and the output was the tensile shear *** the models,the second-order polynomial estimation model had the best estimation performance,and the average error rate of this model was 0.058.

关键词： laser welding scanner remote welding 5J32 aluminum alloy regression model

EXPLICIT BOUNDS OF EIGENVALUES FOR STIFFNESS MATRICES BY QUADRATIC HIERARCHICAL BASIS METHOD)

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Journal of Computational Mathematics 2003年第2期21卷 113-124页

作者： Sang dong kim Byeong Chun SHIN Department of Mathematics Kyungpook National UniversityTaegu 702-701KoreaDepartment of MathematicsChonnam National UniversityGwangju 500-757Korea

The bounds for the eigenvalues of the stiffness matrices in the finite element discretization corresponding to Lu := - u' with zero boundary conditions by quadratic hierarchical basis are shown explicitly. The condition number of the resulting system behaves like O(1/h) where h is the mesh size. We also analyze a main diagonal preconditioner of the stiffness matrix which reduces the condition number of the preconditioned system to O(1).

关键词： hierarchical basis multilevel

Complete characterization of ultrafast optical fields by phase-preserving nonlinear autocorrelation

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Light(Science & Applications) 2022年第10期11卷 2451-2462页

作者： Alexander Gliserin Soo Hoon Chew Seungchul kim dong Eon kim Department of Optics and Mechatronics Engineering College of Nanoscience and NanotechnologyPusan National University2 Busandaehak-ro 63beon-gilBusan 46241South Korea Department of Cogno Mechatronics Engineering College of Nanoscience and NanotechnologyPusan National University2 Busandaehak-ro 63beon-gilBusan 46241South Korea Max Planck Center for Attosecond Science Max Planck POSTECH/Korea Research Initiative77 Cheongam-roPohang 37673South Korea Department of Physics Center for Attosecond Science and TechnologyPohang University of Science and Technology77 Cheongam-roPohang 37673South Korea

Nonlinear autocorrelation was one of the earliest and simplest tools for obtaining partial temporal information about an ultrashort optical pulse by gating it with ***,since the spectral phase is lost in a conventional autocorrelation measurement,it is insufficient for a full characterization of an ultrafast electric field,requiring additional spectral information for phase ***,we show that introducing an intensity asymmetry into a conventional nonlinear interferometric autocorrelation preserves some spectral phase information within the autocorrelation signal,which enables the full reconstruction of the original electric field,including the direction of time,using only a spectrally integrating *** call this technique Phase-Enabled Nonlinear Gating with Unbalanced Intensity(PENGUIN).It can be applied to almost any existing nonlinear interferometric autocorrelator,making it capable of complete optical field characterization and thus providing an inexpensive and less complex alternative to methods relying on spectral measurements,such as frequency-resolved optical gating(FROG)or spectral phase interferometry for direct electric-field reconstruction(SPIDER).More importantly,PENGUIN allows the precise characterization of ultrafast fields in non-radiative(e.g.,plasmonic)nonlinear optical interactions where spectral information is *** demonstrate this novel technique through simulations and experimentally by measuring the electric field of~6-fs laser pulses from a Ti:sapphire *** results are validated by comparison with the well-established FROG method.

关键词： autocorrelation nonlinear characterization