• Archives of Reconstructive Microsurgery
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• 제22권2호
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• pp.48-51
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• 2013

Purpose: The lessor saphenous vein is an anatomical index in various surgical methods involving an approach to the popliteal fossa. However, occasionally, there have been some cases where the surgical process was difficult because the lessor saphenous vein was not found in the popliteal fossa during the operation process. The aim of this study is to determine the frequency of the anatomical variation of lessor saphenous vein not found in the popliteal fossa with a review of the literature. Materials and Methods: This study was conducted on 83 cases of selective neurectomy for hypertrophic calf performed in our clinic from March 1997 to June 2013. There were 42 patients, with a mean age of 32.8 years old. We confirmed the existence of the lessor saphenous vein in the popliteal fossa during the operation process. Results: Among 83 cases during this study period, the lesser saphenous vein was not found in four cases. In one patient, no lesser saphenous vein was found on either side of the popliteal fossa, and in two patients, no lesser saphenous vein was found on the left side of the popliteal fossa. As a result, the frequency of variation was found to be 4.8%. Conclusion: Due to the anatomical variation of the lessor saphenous vein, it may not be found in the midline of the popliteal fossa. Based on the literature review, several possibilities for failure to observe the lesser saphenous vein could be suggested. If surgeons are well aware of these possibilities, the steadier operation could be performed.

• 한국분말재료학회지
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• 제23권3호
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• pp.207-212
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• 2016

In this study, Fe-Cu-Ni-Mo-C low alloy steel powder is consolidated by spark plasma sintering (SPS) process. The internal structure and the surface fracture behavior are studied using field-emission scanning electron microscopy and optical microscopy techniques. The bulk samples are polished and etched in order to observe the internal structure. The sample sintered at $900^{\circ}C$ with holding time of 10 minutes achieves nearly full density of 98.9% while the density of the as-received conventionally sintered product is 90.3%. The fracture microstructures indicate that the sample prepared at $900^{\circ}C$ by the SPS process is hard to break out because of the presence of both grain boundaries and internal particle fractures. Moreover, the lamellar pearlite structure is also observed in this sample. The samples sintered at 1000 and $1100^{\circ}C$ exhibit a large number of tiny particles and pores due to the melting of Cu and aggregation of the alloy elements during the SPS process. The highest hardness value of 296.52 HV is observed for the sample sintered at $900^{\circ}C$ with holding time of 10 minutes.

• 한국인터넷방송통신학회논문지
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• 제16권5호
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• pp.33-38
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• 2016

현재 안드로이드는 유저 레벨의 데몬들을 통하여 시스템에 필요한 기능을 서비스 함수로 지원하고 IPC를 사용해 호출되도록 한다. 그런데 서비스 함수를 관리하는 작업이 빈번하게 사용되는 Critical Path 임에도 불구하고, 유저 레벨 프로세스가 수행하도록 되어 있다. 이러한 분리된 구조는 모듈성과 유연성의 관점에서 효율적이지만 복잡한 소프트웨어 스택 및 컨텍스트 스위치 오버헤드 등으로 서비스 응답 시간이 상당히 저하된다. 본 논문에서는 안드로이드 IPC 매커니즘의 병목점이 되는 부분을 분석하고 개선함으로써 이러한 문제를 해결한다. 우리는 IPC 지연 시간 중 55%가 커널과 컨텍스트 매니저 사이의 커뮤니케이션 오버헤드인 것을 발견하고, 서비스 함수 중 자주 접근되는 것들에 대한 정보는 커널 내에 캐쉬 형태로 유지하는 기법을 제안한다. 제안된 IPC 캐쉬는 안드로이드 5.0에 구현되었으며, 다양한 모바일 벤치마크를 통해 성능평가를 수행한 결과 52.9%의 성능이 향상되었다.

• 한국CDE학회논문집
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• 제18권1호
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• pp.36-48
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• 2013

In general, the product is used under several circumstances including environmental and usage conditions. According to the circumstances, the product has various performance degradation processes. In order to optimize the lifecycle of product usage, it is important to observe the degradation process and make suitable decisions on product operations. However, there are not much research works in evaluating the degree of product degradation based on product usage data. Recently, due to emerging ICT (Information and Communication Technology) technologies, it becomes possible to get the product usage data. Based on the gathered data, it is possible to analyze the degree of product degradation. The analysis of product usage data can improve product use and product design with advanced decisions. To this end, this study addresses one approach based on FMEA/FMECA method, called PDMCA (Performance, Degradation Modes and Criticality Analysis) for evaluating product degradation status and making suitable decisions.

• 전기의세계
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• 제29권8호
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• pp.524-531
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• 1980

In order to investigate the effect of inorganic dielectric fine particle mixed in Low Density Polyethylene on the deterioration by treeing, a comparative study for initiation and development of the tree has been carried out between the pure thin film specimen and the same geometrical specimen mixed with a constant weight percent by a defiend particle size of $Al_{2}$O$_{3}$ and SiO$_{2}$, having larger dielectric constants than that of the base material. According to the results, it has been observed that as increasing dielectric constant, the initiation of tree is expedited, however, the development of the tree reached at the surface of filler particles shows the suppressive trends. From these facts, a reasonable interpretation may be possible by considering the effect of intensified electrical field around the tip in the presence of filler particles, that the initiation and the development of tree are a mechanical break down process caused by Maxwell stress due to the concentration of electrical field at the tip. This suppressive effect is specifically suggestive for the reason that a discharge route must be constructed around the particle surface because of the intensified field strength near filler, which, in turn, reduces the geometrical curvature of the tip so that the local intensity of electrical field can be relaxed. Further more an experimental evidence for this assumption was able to observe in this investigation.

• 수산해양기술연구
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• 제33권1호
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• pp.27-37
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• 1997

The aim of the present study is to investigate experimentally the mechanism of an exploding wire in water and also to observe the bubble motion induced by an exploding wire. The experiment of an exploding wire is carried out in a water tank. As a metallic wire, a tungsten wire of 0.2mm in diameter and 10mm in length is employed. The electric energy of 50-300J is fed to the wire from a capacitor of 100$\mu$F charged up to 1-2.5kV. The explosion is recorded by a CCD camera with the resolution of 1$\mu$sec. The explosion process of metallic wire is divided into three phases. Phase 1 : As the voltage is applied to the wire, the temperature increases due to Joule heating and the wire emits light. Phase 2 : Then the wire melts and the cylindrical plasma is formed between the electrodes. Up to this stage, strong light emission is observed. Phase 3 : The light emission goes out and a vapor bubble begins to grow spherically. The radius of a bubble oscillates in time, but the amplitude of oscillation diminishes in several cycles.

• 한국연소학회지
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• 제13권4호
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• pp.47-53
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• 2008

The reaction mechanism of methane dry reforming has been investigated using an arc-jet reactor. The effects of input power, $CO_2/CH_4$ and added $O_2$ were investigated by product analysis, including CO, $H_2$, $C_{2}H_{Y}$ and $C_{3}H_{Y}$ as well as $CH_4$ and $CO_2$. In the process, input electrical power activated the reactions between $CH_4$ and $CO_2$ significantly. The increased feed ratio of the $CO_2$ to $CH_4$ in the dry reforming does not affect to the $CH_4$ conversion. but we could observe increase in CO selectivity together with decreasing $H_2$ generation. Added oxygen can also increase not only CO selectivity but also $CH_4$ conversion. However, hydrogen selectivity was decreased significantly due to a increased $H_{2}O$ formation.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1992년도 추계학술대회 논문집
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• pp.136-144
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• 1992

Recently, Silicon Nitrde ceramic is regarded as the representative engineering ceramic with the excellent mechanical properties and many functions for mechanical components and parts among various kinds of ceramics in the mechanical industry. But, during the manufacturing of engineering ceramics, there is many volumetric shrinkage coupled with a distortion of the parts which is produced. Due to the requirement for high accuracy of size, form, and surface finish of the components, machining is needed surely. Nowdays, grinding with a resin bond type diamond wheels has been generally applied to machining of the engineering ceramics in the whole world because that it can be conveniently proceeded for workers to dress of tool and made with high reliability in producing factories among many bond type super-abrasive wheels yet. It is important task for attaining prescribed mechanical components with high reliability to observe the grinding mechanism of ceramics as like generation of cracks and chipping of material during process. Because they considerably effects on the strength characteristic of machined mechanical components. In this study, various surface grinding experiments using resin bond type diamond wheels are carried out for Silicon Nitride ceramic. Grinding mechanism of ceramics is observed experimentally and the relationship with various conditions is also attained. Form this experimental study, some useful machining data and information to determine proper machining condition for grinding of Silicon Nitride ceramic is obtained.

• 한국전자통신학회논문지
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• 제11권7호
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• pp.717-722
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• 2016

본 논문은 집중력에 대한 문제를 해결할 수 있는 과정으로서 뇌파의 변화를 관측하는 것을 목적으로 하고 있다. 본 연구에서의 실험에서는 뇌파 실험의 피험자들에게 두 가지 과제를 수행하도록 하였는데, 첫 번째 과제는 스마트폰으로 일정시간동안 게임을 하도록 한 후 단어를 암기하는 것이고, 두 번째 과제는 종이책을 읽은 후 단어를 암기하는 것이다. 본 논문에서는 피험자의 과제 수행 중에 발생하는 뇌파를 집중력과 관련된 성분인 SMR파와 중간 베타파로 나누어 분석한 결과를 제시한다.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2017년도 춘계학술대회 논문집
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• pp.148-148
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• 2017

Surface modification is a type of mechanical manipulation skills to achieve extensive aims including corrosion control, exterior appearance, abrasion resistance, electrical insulation and electrical conductivity of substrate materials by generating a protective surface using electrical, physical and chemical treatment on the surface of parts made from metallic materials. Such surface modification includes plating, anodizing, chemical conversion treatment, painting, lining, coating and surface hardening; this study conducted cavitation experiment to assess improvement of durability using anodizing. In order to observe surface characteristics with applied current density, the electrolyte temperature, concentration was maintained at constant condition. To prevent hindrance of stable growth of oxide layer due to local temperature increase during the experiment, stirring was maintained at constant speed. In addition, using galvanostatic method, it was maintained at processing time of 40minutes for 10 to $30mA/cm^2$. The cavitation experiment was carried out with an ultra sonic vibratory apparatus using piezo-electric effect with modified ASTM-G32. The peak-to-peak amplitude was $30{\mu}m$ and the distance between the horn tip and specimen was 1mm. The specimen after the experiment was cleaned in an ultrasonic bath, dried in a vacuum oven for more than 24 hours, and weighed with an electric balance. The surface damage morphology was observed with 3D analysis microscope. As a result of the study, differences were observed surface hardness and anti-cavitation characteristics depending on the development of oxide film with the anodizing process time.