매쉬-심 용접 판재의 성형 한계

김형목,허영무,양대호,서대교 기계기술연구소 1999 성균관대학교 논문집 기계기술편 Vol.1 No.1

This paper describes experimental investigation on the forming limit for mash-seam welded sheets. The uniaxial tensile test was conducted to evaluate the mechanical properties of weld bead. Experimental forming limit diagrams were investigated for the different thicknesses and properties of welded sheets.

대퇴-대퇴동맥간 우회로술 후 하지 허혈증상 재발 및 이식편 폐색의 원인

김형기,김영욱,허승,나목찬 대한혈관외과학회 2002 Vascular Specialist International Vol.18 No.1

With increasing number of high-risk advanced atherosclerotic patients, crossover femoro-femoral pypass (FFB) became commonly chosen extra-anatomic bypass for symptomatic iliac artery occlusive disease. But the causes FFB graft failure have not been clarified yet. Purpose: We aimed to investigate the natural course of native artery disease, the causes of graft occlusion and recurrent leg ischemia after FFBs. Method: Among 162 primary FFBs for ??atherosclerotic iliac occlusive disease, 45 patients who underwent follow-up arteriography for recurrent ischemic symptom were enrolled. We investigated the interval changes between initial preoperative and follow-up angiograms and categorized then as inflow, outflow and/or graft lesion into stenosis >50% or occlusion. And the patients were divided into 2 groups as patent FFB group and occluded FFB group. We compared interval changes on angiograms between patient and occluded FFB groups to find out any difference and tried to determine the ultimate causes of recurrent leg ischemia considering not only the interval changes but the preexisting, untreated leg arterial lesions. Result: The follow-up angiography was most commonly performed within 1 year after FFV with mean interval of 21.2 ± 21.6 months. Interval changes between 2 angiograms were 24 (53.3%) FFB grafts occlusion, 8 (17.8%) inflow iliac disease progression, and 26 (57.8%) outflow arterial occlusion. Comparing the interval changes between patent and occluded FFB groups, the significantly higher frequency of outflow occlusion was noted in occluded FFB group (75% ??vs 38.1%, P=0.012). The most common finding on follow-up ??angiongram responsible for the recurrent ischemia was also outflowarterial occlusion even in patent FFB group. Conclusion: The most common cause of graft occlusion and recurrent leg ischemia was outflow arterial occlusion after FFB.

회로 및 수식 기반의 혼합 모델링 기법을 이용한 7상 영구자석 브러시리스 교류전동기의 시뮬레이션 모델

묵형수,김상훈 강원대학교 산업기술연구소 2007 産業技術硏究 Vol.27 No.A

The counter emf(electromotive forces) of a permanent magnet multi-phase brushless motor is generally a non-sinusoidal wave or a non-ideal trapezoid. So, conventional modeling using a sinusoidal wave or an ideal trapezoid counter emf can result in errors. In order to reduce modeling errors for simulation and analysis the properties of a multi-phase brushless AC motor, this paper proposes a phase variable model that is a mixed modeling technique using both Finite Element Analysis(FEA) based circuits and motor voltage equations. The phase model parameters including the counter emf voltage waveform are obtained by using of FEA, and the mixed modeling technique based on circuits and equations is used to implement a simulation model for multi-phase brushless AC motors with any counter emf voltage waveforms. Adequacy of the proposed model is established from the simulation and experimental results for a seven-phase brushless motor.

국부 마모 부품을 위한 레이저 표면강화 열처리에 관한 연구

이목영,김형준,김기철,김재웅 한국레이저가공학회 2002 학술발표대회 Vol.2002 No.1

두께 10mn 일반기계구조용강재를 사용하여 레이저 종류에 따른 표면경화 열처리특성에 관하여 알아보았다. 경화층의 형성은 레이저의 종류에 크게 영향을 받았는데, 표면경화 열처리를 위해서는 파장이 짧은 Nd-YAG 레이저를 사용하는 것이 유리하였다. 경화층의 최고경도는 700Hv 가량으로 높게 나타났으며, 레이저 표면경화 열처리는 상온에서 사용되는 부품의 내마모성 향상 특히 국부 마모를 겪는 부품에 효과적일 것으로 판단되었다.

목모-시멘트판의 제조와 응용 연구(Ⅱ)

서정목,김형중 公州大學校工科大學生産技術硏究所 1998 論文集 Vol.6 No.-

Inexpensive and retrofittable insulation materials for existing home and buildings are urgently needed to provide the means of our nation's effort to conserve the energy. In this study our objectives were focused on collecting the data in setting up a manufacturing facilities and in evaluating the properties for the applications of wood-wool cement board. Wood wool from various kinds of wood sources was produced by using a designed wood wool making machine. Also, wood wool-cement boards were made by using various wood wools, cements, and additives. The properties of manufactured wood wool-cement board, such as fire resistance, specific gravity, thermal conductivity, acoustic insulation, and bending strength were evaluated. Considering the product cost and the insulation cost, we strongly believe that the wood wool cement board will be served as a retrofittable insulation materials successfully.

Mock-up experiments on permeability measurement of concrete and construction joints for air tightness assessment

Kim, Hyung-Mok,Lettry, Yanick,Ryu, Dong-Woo,Song, Won-Kyong Rilem Publications 2014 Materials and Structures Vol.47 No.1

Coupled Viscous Fluid Flow and Joint Deformation Analysis for Grout Injection in a Rock Joint

Kim, Hyung-Mok,Lee, Jong-Won,Yazdani, Mahmoud,Tohidi, Elham,Nejati, Hamid Reza,Park, Eui-Seob Springer-Verlag 2018 Rock mechanics and rock engineering Vol.51 No.2

<P>Fluid flow modeling is a major area of interest within the field of rock mechanics. The main objective of this study is to gain insight into the performance of grout injection inside jointed rock masses by numerical modeling of grout flow through a single rock joint. Grout flow has been widely simulated using non-Newtonian Bingham fluid characterized by two main parameters of dynamic viscosity and shear yield strength both of which are time dependent. The increasing value of these properties with injection time will apparently affect the parameters representing the grouting performance including grout penetration length and volumetric injection rate. In addition, through hydromechanical coupling a mutual influence between the injection pressure from the one side and the joint opening/closing behavior and the aperture profile variation on the other side is anticipated. This is capable of producing a considerable impact on grout spread within the rock joints. In this study based on the Bingham fluid model, a series of numerical analysis has been conducted using UDEC to simulate the flow of viscous grout in a single rock joint with smooth parallel surfaces. In these analyses, the time-dependent evolution of the grout fluid properties and the hydromechanical coupling have been considered to investigate their impact on grouting performance. In order to verify the validity of these simulations, the results of analyses including the grout penetration length and the injection flow rate were compared with a well-known analytical solution which is available for the simple case of constant grout properties and non-coupled hydraulic analysis. The comparison demonstrated that the grout penetration length can be overestimated when the time-dependent hardening of grout material is not considered. Moreover, due to the HM coupling, it was shown that the joint opening induced by injection pressure may have a considerable increasing impression on the values of penetration length and injected grout volume.</P>

Characterization of charging effect of citrate-capped Au nanoparticle pentacene device

Hyung-Jun Kim,Sung Mok Jung,Bong-Jin Kim,윤태식,김용상,이현호 한국공업화학회 2010 Journal of Industrial and Engineering Chemistry Vol.16 No.5

Capacitance–voltage hysteresis for a non-volatile memory was realized in a metal–pentacene–insulator–silicon (MPIS) device using gold (Au) nanoparticles (NPs) intervened between pentacene and SiO2 insulator. A memory window higher than 2.0 V was obtained under () 5 V programming sweeping range. The SiO2 as thick as 30 nm was adopted as the dielectric layer, and 3-aminopropyl-triethoxysilane (APTES) was used for self-assembling of Au NPs monolayer. In addition, citrate-functionalized Au NPs was dip-coated and used as charge storage elements. Formation of a monolayer of the Au NPs was confirmed by HR-SEM and AFM. Capacitance–voltage hysteresis in this study was resulted from the charge storage in the layer of Au NPs. 2010 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.

Understanding the Effect of Intersecting Fault on Induced Seismicity during EGS Stimulation Job from a Coupled Modeling Approach

( Hyung-mok Kim ),( Arshad S. A. Shahid ) 대한지질공학회 2019 대한지질공학회 학술발표회논문집 Vol.2019 No.2

Fault zones are most of the time sealed because of the gauge-minerals and the frictional forces between the fault planes. When these fault zones are injected with fluid for stimulation, these initially stable faults can reactivate. For instance, the Pohang EGS field was injected with 12,800 ㎥ of water for stimulation of the fault zone in January 2016. Intense seismic activity was detected by the geophone arrays near the Pohang EGS site, which is now believed to be triggered by the water injection into the rock for EGS. On the 15th November 2017 an earthquake of 5.4 (Mw) was observed accompanied with foreshocks and aftershocks. The proper modelling of induced seismic activity is needed to describe the reasons behind the technically unexpected earthquake magnitude, and to allow future prediction of induced seismicity as well. A detailed coupled geomechanics and fluid-flow-modelling approach is required to describe both, fluid flow behaviour during injection and fault deformation causing the seismicity. Shahid (2015) developed a coupled modelling approach for fracture reactivation in shale-gas reservoirs and predicting micro-seismicity during hydraulic fracturing. In this study, the same modelling approach was extended for simulating induced seismicity of EGS stimulation job. We demonstrate that presence of initially unknown secondary fault influence how the main fault zone failed during stimulation. Parametric studies also suggested that uncertainty of mechanical and hydraulic parameters on secondary fault result in much different seismicity profile. This study gives insight into the reasons for the unexpected seismicity observed for many EGS cases.

ERRATUM : Outcome of Inhaler Withdrawal in Patients Receiving Triple Therapy for COPD

Kim, Sae Ahm,Lee, Ji-Hyun,Kim, Eun-Kyung,Kim, Tae-Hyung,Kim, Woo Jin,Lee, Jin Hwa,Yoon, Ho Il,Baek, Seunghee,Lee, Jae Seung,Oh, Yeon-Mok,Lee, Sang-Do The Korean Academy of Tuberculosis and Respiratory 2016 Tuberculosis and Respiratory Diseases Vol.79 No.3