• 대한조선학회논문집
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• 제53권1호
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• pp.62-68
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• 2016

A simple calculation tool for added resistance in waves is developed to utilize for initial design or embedded module for navigation support system. In order to select an appropriate calculation method for added resistance in waves, three methods (drift method, integrated pressure method, radiated energy method) based on strip method are applied to Wigley I and KVLCC2. The methods for added resistance in waves give the underestimated results because it is difficult to consider nonlinear effects due to reflected wave. We apply asymptotic (Faltinsen's method) and empirical formula (NMRI's method) to improve the accuracy for short wave length region. In comparison with experimental results, the combination of radiated energy method and short wave correction method of NMRI is the most reasonable. However, a simple sum of results calculated by two methods gives rise to the overestimation of added resistance for short wave length region because added resistance of radiated energy method exits in total reflection region. To overcome this problem, modified radiated energy method is proposed using correction coefficient defined by reflection coefficient of NMRI's method. Finally, added resistance in regular waves is composed of added resistance of modified radiated energy method and that of short wave correction method of NMRI. Estimated added resistance in regular waves is validated by comparison with experimental results of other research groups.

• 동력기계공학회지
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• 제14권6호
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• pp.83-88
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• 2010

The wear behavior of epoxy matrix composites filled with nano sized silica particles is discussed in this paper. Especially, the variation of the coefficient of friction and the wear resistance according to the change of apply load and sliding velocity were investigated for these materials. Wear tests of pin-on-disc mode were carried out and the wear test results exhibited as following ; The epoxy matrix composites showed lower coefficient of friction compared to the neat epoxy through the whole sliding distance. As increasing the sliding velocity the epoxy matrix composites indicated lower coefficient of friction, whereas the neat epoxy showed higher coefficient of friction as increasing the sliding velocity. The specific friction work of both materials were increased with apply load. In case of the epoxy matrix composites, the running in periods of friction were reduced as increase in apply load. The epoxy matrix composites were improved the wear resistance by adding the nano silica particles remarkably. It is expected that the load carrying capacity of the epoxy matrix composites will be improved by increase of Pv factor.

• 한국터널지하공간학회 논문집
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• 제20권1호
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• pp.39-53
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• 2018

일반적으로 터널 내 총환기저항계수는 입출구 손실계수, 벽면마찰계수 그리고 급격한 확대나 축소단면 등에 의해 발생하는 부차적 손실계수의 총합으로 구성된다. 개통 전 터널의 경우는 가동 중인 환기팬을 중단하게 되면, 터널 내 풍속은 총환기저항력에 의해 감소하는 현상이 나타난다. 즉, 속도감쇄법은 개통 전 터널에서 비교적 안정적이면서도 손쉽게 터널 내 벽면마찰계수를 추정하는 방법이다. 그러나 기존의 선행연구에서 환기팬의 가동을 중단 후 수렴되는 풍속이 음수일 경우는 속도감쇄법에 따른 벽면마찰계수의 추정이 곤란한 특성이 있다. 반면 교통환기력이 작용하는 공용 중인 터널에서는 좀더 복잡한 과정을 거치지만, 합리적인 벽면마찰계수를 추정할 수 있다. 본 연구에서는 교통환기력의 측정변수를 최소화할 수 있는 방법을 제안하였고, 공용 중 터널에 적용할 수 있는 방법을 고찰하였다. 또한 환기팬 정지 후 터널 내 풍속이 감소하는 동안에 외부 자연풍의 급격한 변화가 발생하여도 교통환기력이 일정할 경우에 대하여, 교통환기력의 증분을 계산할 수 있는 방법과 터널 내 벽면마찰계수를 추정할 수 있도록 동적 시뮬레이션이 가능한 프로그램 로직을 개발하였다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 추계학술대회 논문집 Vol.14 No.1
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• pp.558-561
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• 2001

Vanadium oxide ($VO_x$) thin films are very good candidate material for uncooled infrared (IR) detectors due to their high temperature coefficient of resistance (TCR) at room temperature. But, the deposition of $VO_x$ thin films showing good electrical properties is very difficult in micro bolometer fabrication process using sacrificial layer removal because of its low process temperature and thickness of thin films less than $1000{\AA}$. This paper presents a new fabrication process of $VO_x$ thin films having high TCR and low resistance. Through sandwich structure of $VO_{x}(100{\AA})/V(80{\AA})/VO_{x}(500{\AA})$ by sputter method and post-annealing at oxygen ambient, we have achieved high TCR more than $-2%/^{\circ}C$ and low resistance less than $10K\Omega$ at room temperature.

• 대한전자공학회논문지SD
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• 제40권5호
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• pp.290-297
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• 2003

전자와 정공의 온도 관련 이온화 계수로부터 추출한 온도 함수의 유효 이온화 계수 및 전자 이동도를 이용하여 실리콘 전력 MOSFET의 항복 전압과 on 저항을 위한 온도 함수의 해석적 표현식을 유도하였다. 온도 함수의 해석적 항복 전압 결과를 4x10/sup 14/ cm/sup -3/, 1x10/sup 15/ cm/sup -3/, 6x10/sup 16/ cm/sup -3/의 도핑 농도에 대해 각각 실험 결과와 비교하였고, 온도 및 항복 전압 함수의 on 저항 변화도 각각 실험 결과와 비교하였다. 각농도에 따른 온도 함수의 해석적 항복 전압은 77∼300k의 온도 범위에서 실험 결과와 10% 이내의 오차로 잘 일치하였다.

• 한국신뢰성학회지:신뢰성응용연구
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• 제8권4호
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• pp.155-166
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• 2008

PTH cracks are caused by the mismatch of coefficient of thermal expansion(CTE) between polymer and laminated materials, and are one of the main failure mechanisms of multi layer boards. In spite of its importance, it is usually hard to measure or detect them because of its small size and invisibility. To detect PTH cracks more effectively, this paper proposes a theoretical model that can estimate the resistance value from crack size of PTHs. Using four-point probe resistance measurement method, the resistance value of test coupons is measured. Through measured data, we verify the validity of the proposed theoretical model and set up criteria of failure.

• 대한전자공학회논문지SD
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• 제46권6호
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• pp.1-5
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• 2009

6H-SiC 전자 및 정공의 이온화계수로부터 유효이온화계수를 추출하여 6H-SiC PN 다이오드의 항복전압과 온-저항을 위한 해석적 표현식을 유도하였다. 해석적 모형으로부터 구한 항복전압을 $10^{15}{\sim}10^{18}\;cm^{-3}$의 도핑 농도 범위에서 실험 결과와 비교하여 10% 이내의 오차로 일치하였고, 농도 함수의 온-저항의 해석적 결과도 $5{\times}10^{15}{\sim}10^{16}\;cm^{-3}$의 범위에서 이미 발표된 수치적 결과와 매우 잘 일치하였다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 추계학술대회 논문집
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• pp.558-561
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• 2001

Vanadium oxide ($VO_{x}$) thin films are very good candidate material for uncooked infrared (IR) detectors due to their high temperature coefficient of resistance (TCR) at room temperature. But, the deposition of $VO_{x}$ thin films showing good electrical properties is very difficult in micro bolometer fabrication process using sacrificial layer removal because of its low process temperature and thickness of thin films less than 1000${\AA}$. This paper presents a new fabrication process of $VO_{x}$ thin films having high TCR and low resistance. Through sandwich structure of $VO_{x}$(100${\AA}$)/V(80${\AA}$)/$VO_{x}$(500${\AA}$) by sputter method and post-annealing at oxygen ambient, we have achieved high TCR more than -2%/$^{\circ}C$ and low resistance less than $10K\Omega$ at room temperature.

• 대한금속재료학회지
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• 제50권11호
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• pp.809-815
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• 2012

Recently, as the interest in improving energy efficiency has grown, the demand for vehicle and machine parts that are resistant in high temperature corrosive conditions and abrasive environments has increased. Pack chromizing treatment of sintered steels is a profitable method that satisfies both corrosion resistance and low friction properties. Since austenitic stainless steels have good corrosion resistance but low mechanical hardness, if they are replaced by sintered steel parts with pack chromizing treatment, all the desirable properties such as low price, easy molding, high hardness, low frictional coefficient, and high corrosion resistance, can be obtained. The higher corrosion resistance of the chromized parts over that of the austenitic stainless steels was acquired by coating chromium carbides and a thin chromium oxides layer on the surface. Moreover, the surface morphology of chromized parts, which were composed of chromium rich phases and hardened chromium carbides by diffusing and alloying, had a peak-and-valley shape so that the dimple effect by the wrinkled morphology and high hardness induced a low friction coefficient.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 춘계 학술발표회 제16권1호
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• pp.802-805
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• 2004

This study was performed to investigate the effect of mineral admixture' type and replacement ratios on the chloride penetration resistance of concrete which was immersed in the artificial chloride solution. The chloride penetration resistance was evaluated by penetration depth and chloride diffusion coefficient. As a result, all of the mineral admixtures were effective on the chloride penetration resistance of concrete compared to ordinary portland cement only.