• 소성∙가공
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• 제16권4호
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• pp.293-298
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• 2007

Recently, there is a need to produce a large forged part for the flight, shipping, some energies, and military industries, etc. Therefore, an open die forging technique of cast ingots is required to obtain higher quality of large size forged parts. Cogging process is one of the primary stages in many open die forging processes. In the cogging process prior to some open die forging processes, internal cavities have to be eliminated for defect-free. The present work is concerned with the elimination of the internal cavities in large ingots so as to obtain sound products. In this study, hot compression tests were carried out to obtain the flow stress of cast microstructure at different temperature and strain rates. The FEM analysis is performed to investigate the overlap defect of cast ingots during cogging stage. The measured flow stress data were used to simulate the cogging process of cast ingot using the practical material properties. Also the analysis of cavity closure is performed by using the $DEFORM^{TM}-3D$. The calculated results of cavity closure behavior are compared with the measured results before and after cogging, which are scanned by the X-ray scanner. From this result, the criteria for deformation amounts effect on the cavity closure can be investigated by the comparison between practical experiment and numerical analysis.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제30권2호
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• pp.157-161
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• 2004

본 방법을 통해 수술할 경우 몇 가지 장점이 있다. Y needle의 경우 5mm간격으로 고안되어 있어 3부위에서 일정량의 조직결찰이 가능하고 고안에 따라 여러 가지 간격으로 만들어 질 수 있어 환자의 상태에 따라 적용가능하다. 또한 피부부위에서 결막으로 들어가는 부위가 수직이어서 원하는바 정확한 이중검 위치를 만들어 줄 수 있다. 초심자가 시행하더라도 관통부위를 eyelash 경계와 비교적 평행하게 만들어 줄 수 있다. Needle의 삽입이 2개가 한꺼번에 삽입되므로 환자가 느끼는 통증이 감소되며 술자의 편의도도 증가하리라 생각된다. 부분절개법을 사용하여 잉여지방 및 조직을 제거하였고 매몰하여 흉터와 부작용을 최소화하였고 회복기간과 수술시간을 감소시킬 수 있었다. 본 방법은 모든 경우의 이중검수술에 이용될 수는 없겠으나 고찰에서 기술한 비절개식이나 부분절개식 이중검수술의 적응증에 해당되는 경우에 이용할 경우 아주 간단하고 임상적으로 표준화 될수 있는 방법으로 응용될 수 있을 것으로 사료되어 문헌고찰과 함께 보고하는 바이다.

• The Journal of Asian Finance, Economics and Business
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• 제7권6호
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• pp.409-416
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• 2020

The research has been conducted to explore the combination of three intangible resources, including social capital, entrepreneurship, and resilience capability on the performance of State Capital Enterprises (SCEs) in Vietnam. Both qualitative and quantitative approaches are applied in the study. An in-depth interview of ten CEOs at SCEs in Vietnam was made to explore new indicators for the contextual latent variables in the research models. By employing the data from the authors' survey of 568 SCEs in Vietnam in 2019, using Cronbach's alpha, confirmatory factor analysis (CFA) and path analysis (SEM), the mechanism that social capital impacts on SCE performance has been analyzed. In addition to the direct role, social capital indirectly affects corporate performance through entrepreneurship and resilience capability. It was found that social capital has a larger impact on entrepreneurship than resilience capacity. However, the contribution of resilience capacity to the firm performance is much more than the entrepreneurship's in Vietnamese context. This study enriches the theory by proposing a measurement scale of the contextual latent variables as a result of in-depth interviews with experts using a qualitative analysis technique. In addition, the path analysis findings suggest practical implications for managers to effectively use their resources in SCEs.

• Journal of Chest Surgery
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• 제50권6호
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• pp.467-470
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• 2017

Extensive mitral annulus calcifications are considered a contraindication for valve surgery. We describe the case of a 76-year-old female with severe mitral and aortic stenosis associated with extensive calcifications of the heart. The patient underwent an open mitroaortic valve replacement using transcatheter aortic valve implantation with an Edwards SAPIEN XT valve (Edwards Lifesciences Corp., Irvine, CA, USA) in the mitral position. The aortic valve was replaced using a stentless valve prosthesis (LivaNova S OLO; LivaNova PLC, London, UK). Postoperative echocardiography showed that the prosthetic valve was in the correct position and there were no paravalvular leaks. A bailout open transcatheter valve implantation can be considered a safe and effective option in selected cases with an extensively calcified mitral valve.

• 한국환경과학회지
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• 제20권5호
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• pp.581-587
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• 2011

Industrial natural ventilation systems consist of gravity ventilator, the high/low windows and doors. Especially, the high windows play an important role in the industrial natural ventilation systems. Generally speaking, industrial high windows are divided into 3 types; louver type, $45^{\circ}$ open type and $90^{\circ}$ open type. This study was numerically and experimentally conducted. Three types of windows were tested to know the ventilation characteristics and estimate the ventilation efficiencies. Numerically, computational fluid dynamics software (AIR PAK Ver. 2.0) was used to observe the flow characteristics inside the industrial building and the concentration contours generated by the tracer gas method. Experimentally, the flow visualization technique and the tracer gas method were applied with the model building to characterize the flow pattern inside the model building and to estimate the ventilation efficiencies with the different windows. It was found that $90^{\circ}$ open type window was most effective for the discharge of pollutants from the industrial building. On the other hand, the louver type window was found to be less effective than any other windows.

• International Journal of Naval Architecture and Ocean Engineering
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• 제2권3호
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• pp.139-145
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• 2010

In the present study, we conducted resistance test, propeller open water test and self-propulsion test for a ship's resistance and propulsion performance, using computational fluid dynamics techniques, where a Reynolds-averaged Navier-Stokes equations solver was employed. For convenience of mesh generation, unstructured meshes were used in the bow and stern region of a ship, where the hull shape is formed of delicate curved surfaces. On the other hand, structured meshes were generated for the middle part of the hull and the rest of the domain, i.e., the region of relatively simple geometry. To facilitate the rotating propeller for propeller open water test and self-propulsion test, a sliding mesh technique was adopted. Free-surface effects were included by employing the volume of fluid method for multi-phase flows. The computational results were validated by comparing with the existing experimental data.

• Journal of Electrical Engineering and Technology
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• 제10권6호
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• pp.2277-2287
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• 2015

In recent times, multilevel inverters are given high priority in many large industrial drive applications. However, the reliability of multilevel inverters are mainly affected by the failure of power electronic switches. In this paper, open-switch and short-switch failure of multilevel inverters and its identification using a high performance diagnostic system is discussed. Experimental and simulation studies were carried out on five level cascaded H-Bridge multilevel inverter and its output voltage waveforms were analyzed at different switch fault cases and at different modulation index values. Salient frequency domain features of the output voltage signal were extracted using the discrete wavelet transform multi resolution signal decomposition technique. Real time application of the proposed fault diagnostic system was implemented through the LabVIEW software. Artificial neural network was trained offline using the Matlab software and the resultant network parameters were transferred to LabVIEW real time system. In the proposed system, it is possible to precisely identify the individual faulty switch (may be due to open-switch (or) short-switch failure) of multilevel inverters.

• International Journal of Fluid Machinery and Systems
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• 제7권4호
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• pp.174-182
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• 2014

The ultimate objective of this study is to develop a water turbine appropriate for low-head open channels to effectively utilize the unused hydropower energy of rivers and agricultural waterways. The application of a cross-flow runner to open channels as an undershot water turbine has been considered and, to this end, a significant simplification was attained by removing the turbine casing. However, the flow field of an undershot cross-flow water turbine possesses free surfaces, and, as a result, the water depth around the runner changes with variation in the rotational speed such that the flow field itself is significantly altered. Thus, clear understanding of the flow fields observed with free surfaces to improve the performance of this turbine is necessary. In this study, the performance of this turbine and the flow field were evaluated through experiments and numerical analysis. The particle image velocimetry technique was used for flow measurements. The experimental results reflecting the performance of this turbine and the flow field were consistent with numerical analysis. In addition, the flow fields at the inlet and outlet regions at the first and second stages of this water turbine were clarified.

• 대한공간정보학회지
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• 제5권2호
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• pp.45-54
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• 1997

도시녹지공간의 수목은 체계적이고, 신속한 관리를 함으로써 인간에게 더 많은 혜택을 부여한다. 현재 도시 녹지공간에 있어서의 수목관리의 방법론적인 방안을 고려해 볼 때 수목관리의 유지관리를 위한 자료의 수집과 처리, 첨단 System을 활용한 관리체계가 극히 미흡한 실정이다. 이를 위해서는 먼저 녹지자원 관리를 위한 효율적이고 체계적인 자료의 수집 및 처리와 합리적인 분석과정이 필요하며 그 다음으로 이러한 자료를 토대로 하여 적절한 도시녹지공간에 있어서의 수목관리를 효율적으로 처리할 수 있는 시스템과 그 활용이 필요하다. 이러한 시스템으로 본 연구에서는 최근 여러 분야에서 이용되고 있는 GIS을 이용하여 도시녹지관리모델을 제시하고 이를 통하여 그 효율성을 극대화하였다.

• 한국정보시스템학회지:정보시스템연구
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• 제24권4호
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• pp.83-97
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• 2015

Purpose: Traditionally, information technology acceptance have been considered one of the most important research issues. However non-acceptance, which was main objective of acceptance theories, have not been included in main research area by communities of information systems. This study is to identify the factors influencing non-acceptance of information technology and suggest a total research model for explaining the phenomena of non-acceptance. Design/methodology/approach: Grounded theory was adopted as a principal research method. which is an inductive technique of interpreting qualitative data about a social phenomenon to build theories about that phenomenon. Data were collected by depth interview and open question on potential non-adopters during 3 months. The collected data were coded by two main coding paradigm in ground theory, open coding and axis coding. Findings: Factors influencing non-acceptance, status quo, imitation, value evaluation, and concerning risk were extracted from open coding. These factors were integrated into system 1 thinking and system 2 thinking, which were from axis coding. More specifically, status quo and imitation are system 1 thinking which are more responsive and emotional thinking and value evaluation and concerning risk are system 2 thinking which are more rational and reasoning thinking.