• 호남수학학술지
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• 제42권4호
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• pp.821-828
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• 2020

In this work, we prove an existence of an inertial manifold for a system of differential equations with a non-self adjoint leading part. The result follows from the existence and uniqueness of negatively bounded solutions. In fact, we show that a sharp spectral condition is sufficient for the proof.

• 대한기계학회논문집A
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• 제37권8호
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• pp.1007-1013
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• 2013

이 논문은 터빈 로터의 형상변화에 따른 공력 특성에 대하여 분석하였다. 본 논문의 터빈은 헬리콥터의 보조동력 장치로 사용되는 소형엔진이다. 소형엔진은 팁 형상의 구조적 취약성 때문에 성능을 향상시키기 어렵다. 그러므로, 터빈의 허브를 개선하는 것이 여러 가지 측면에서 유리하다. 터빈의 작동유체는 고온 고압의 가스이다. 터빈표면의 열전달률이 고려되었을 때, 열부하에 의한 블레이드의 손상을 줄이기 위해서는 블레이드 표면의 열전달률 분포를 고찰하여야 한다. 수치모사 결과를 검증용 실험값과 비교하였을 때, SST난류모델은 공력 특성을 잘 반영하고 열전달 예측성능도 우수하였다. 결론적으로, 허브측 선단에서 구륜설계(bulbous design)를 적용하였을 때 공력효율이 향상되었고, 전체 공력 손실 중 끝벽 손실은 15% 감소되었다.

• Ocean and Polar Research
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• 제39권3호
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• pp.205-211
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• 2017

This paper seeks to provide a dynamic analysis of a 150 ton winch based on ocean environmental data. The winch model that was subjected to analysis was modeled from CAD to each subsystem by the commercial software DAFUL. The winch model has tree brake systems (disk brake, band brake and ratchet brake). The rotation motion of the motor and contact elements of the brake are applied to the winch model in order to analyze its dynamic characteristics. In addition, a crane-barge was modeled to apply ocean environmental data. The motion data of the crane-barge was produced by means of the RAO(Response Amplitude Operator) of the barge and wave spectrum. The reaction force of the translational joint was measured instead of the tension of the cable. The brake performance of the winch was produced and assessed based on the operating motion of the crane-barge.

• 디자인학연구
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• 제18권4호
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• pp.45-52
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• 2005

인간과 컴퓨터 사이의 상호자웅(Human-Computer Interaction)에 있어 핵심적인 인터페이스 역할을 하고 있는 디스플레이는 미디어의 발전과 함께 보다 선명하고 생생한 화질을 전달하기 위해 계속해서 발전해 왔으며, 최근에는 중형크기 이상의 디스플레이로 LCD(Liquid Crystal Display)와 PDP(Plasma Display Panel)가 가장 보편적으로 사용되고 있다. 기술의 발달로 인해 디스플레이는 점차 대형화 슬림화 되어 마트, 역, 영화관 등과 같이 유동인구가 많은 공간에 설치되어 인쇄매체나 전광판보다 다양한 정보를 전달하고 있는데 디지털 디스플레이는 주로 멀티미디어 컨텐츠를 전달하며 문자정보는 대부분 제한된 공간에서 동적으로 제공되고 있다. Leading은 멀티미디어 컨텐츠를 배경으로 동적 문자정보를 전달하기 위해 가장 많이 사용되는 방법이며 실시간 정보를 나타내기 위해 주로 사용되고 있다. 본 연구에서는 최적의 trading 방법을 알아보기 저해 디스플레이 종류, 화면 관찰 상황, 문자색과 배경색, 문자 제시 속도의 변화에 따라 사용자가 평가하는 읽힘성, 이해도, 만족도를 살펴보았다. 디스플레이 종류에 있어서 모든 평가항목에서 LCD가 PDP 보다 효율적인 것으로 나타났으면 색상에 있어서는 횐색-검정색의 색상 조합이 다른 색상 조합보다 우수하게 평가되었다. 문자 제시 속도에 있어서는 문자정보만을 제공했을 때는 보통속도와 비교적 빠른 속도에서 좋은 결과를 보였으나 동영상과 문자가 동시에 제시되었을 때는 느린 속도가 효과적인 것으로 나타났다.

• 대한기계학회논문집
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• 제16권10호
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• pp.1979-1989
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• 1992

본 연구에서는 말굽와류에 대한 전반적인 사항을 고찰하는 한편, 실린더의 기 하학적 형상이 말굽와류에 미치는 영향을 정성적으로 고찰하는 데 있다. 그러므로 본 실험에서는 먼저 경계층이 형성되어 있는 평판에 원형 실린더를 설치하여, 말굽와 류에 의한 3차원 유동현상을 고찰하고, 또한 동일한 평판에 쐐기형상의 실린더를 설치 하여, 그 주위에서 발생하는 3차원 유동현상과 원형 실린더 주위에서 일어나는 3차원 유동현상과의 정성적인 비교를 통하여, 말굽와류에 의한 3차원 유동손실을 줄일 수 있 는 가능성을 제시하고자 한다.

• 한국자동차공학회논문집
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• 제25권1호
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• pp.51-59
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• 2017

In 2014, there were approximately 4,762 fatalities on Korean roads. The fatality rate has decreased by 6.5 %, as compared to that of the previous year. The pedestrian-vehicle fatalities (1,795) have also decreased by 6 % over the previous year. However, the percentage of the pedestrian fatalities has increased from 37.9 % to 38.7 % during the same period. This is why further research is required, even though the KNCAP pedestrian safety assessment and KMVSS for pedestrian protection currently exist. This paper studied the Upper Legform to Bonnet Leading Edge Test at the front of the vehicles, which has not been introduced yet in Korea. The test method and procedure of the new BLE test in the Euro NCAP test protocol have been reviewed, and the physical tests on SUV and sedan with different bonnet leading edge heights have also been conducted and reviewed. In addition, the test results and characteristics have been analyzed via comparison with the former BLE test and each vehicle type.

• Ocean and Polar Research
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• 제36권4호
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• pp.327-341
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• 2014

This study aims to analyze causality among Wando abalone producer prices by size using a vector autoregressive model to expiscate the leading-price of Wando abalone in various price classes by size per kg. This study, using an analytical approach, applies a unit-root test for stability of data, a Granger causality test to learn about interaction among price classes by size for Wando abalone, and a vector autoregressive model to estimate the statistical impact among t-1 variables used in the model. As a result of our leading-price analysis of Wando abalone producer prices by shell size using a VAR model, first, DF, PP, and KPSS tests showed that the Wando abalone monthly price change rate by size differentiated by logarithm were stable. Second, the Granger causality relationship analysis showed that the price change rate for big size abalone weakly led the price change rate for the small and medium sizes of abalone. Third, the vector autoregressive model showed that three price change rates of t-1 period variables statistically, significantly impacted price change rates of own size and other sizes in t period. Fourth, the impulse response analysis indicated that the impulse responses of structural shocks for price change rate for big size abalone was relatively more powerful in its own size and in other sizes than shocks emanating from other sizes. Fifth, the variance decomposition analysis indicated that the price change rate for big size abalone was relatively more influential than the price change rates for medium and small size abalone.

• 대한기계학회논문집B
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• 제29권5호
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• pp.590-598
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• 2005

The present study has been conducted to investigate the effect of discrete ribs and rotation on heat/mass transfer characteristics in a two-pass square duct with $90^{\circ}-rib$ turbulators. The rib turbulator has a square cross section of 1.5 mm. The rib height-to-hydraulic diameter ratio $({e/D_{h})$ is 0.056, and the rib pitch-to-rib height ratio (p/e) is 10. The gap width is the same as the rib height. The rotation number ranges from 0.0 to 0.2 while Reynolds number is fixed to 10,000. In a stationary duct, the heat/mass transfer on the surfaces with discrete ribs is enhanced because the gap flow promotes local turbulence and flow mixing near the ribbed surface. In a rotating duct, the gap flow affects differently the heat/mass transfer on leading and trailing surfaces with discrete ribs. On the leading surface of the first pass, heat/mass transfer is increased due to the gap flow. On the trailing surface of the first pass, however, heat/mass transfer is decreased because the gap flow disturbs reattachment of main flow. The phenomenon, that is, the difference of heat transfer between the leading and the trailing surfaces is distinctly presented by rotation.

• 대한기계학회논문집A
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• 제41권2호
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• pp.95-101
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• 2017

본 연구에서는 철도차량의 사고의 유형 중 가장 많이 발생되는 지그재깅 현상에 대해 이론 모델을 정립하여 선두차량의 지그재깅 거동에 대한 운동방정식을 도출하였다. 운동방정식을 풀기 위하여 미분방정식 수치해석법 중 가장 대표적인 Runge-Kutta 4차식을 사용하였고, 휠-레일 인터페이스에 의한 휠의 횡 변위는 운동에너지를 이용하여 추정하였다. 그리고 이론식을 검증하기 위하여 재그재깅 현상에서 가장 변위가 큰 연결기 위치에서의 횡 변위에 대해 시뮬레이션과 이론식을 비교한 결과 비 탈선 충돌조건에서 최대 편차율은 0.8 [%] ~ 4.7 [%] 발생하고, 탈선 충돌조건에서는 탈선이 일어나는 시점에서 차량의 횡 변위를 비교한 결과 최대 편차율이 0.6 [%] ~ 5.1 [%]로 잘 일치하는 것을 확인하였다. 이론식을 사용하여 사고나 현상을 시뮬레이션으로 재현할 때 필요한, 전체적인 거동에 부합하는 차량 간 연결의 초기 off-set량을 예측할 수 있다.

• 지식경영연구
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• 제18권3호
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• pp.1-35
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• 2017

This study conducted comparative study on autonomous car's industry policy and corporate strategy of US, China, Germany, Japan and Korea. By analyzing core technologies and industry paradigm shifts of autonomous car industry, I was able to figure out autonomous car has high potential to be dominant transportation in the future and it is important to construct core competency in technology area. The meaningful findings by analyzing various primary and secondary data are as followings: First, in case of US, Google was leading autonomous car industry by developing its own OS and Platform. US government has been actively supporting and interacting with private firms and Universities for stimulating industry/technology convergence and establishing standard. Second, in case of Germany, autonomous car development was leading by several auto makers such as Mercedes, BMW in Hardware and manufacturing area, and German government was focusing on deregulations for private company. Third, in case of Japan which quite similar with German situation, they were both independently developing technology and expanding alliances with MNCs. And Japanese government was supporting triple helix system construction between local companies and universities. Fourth, in case of China, autonomous car industry was leading by IT companies, and various cooperations between IT companies and automakers were established. Chinese government was regulating foreign companies and supporting domestic companies both in market and technologies Last, in Korean case, the active and extensive alliances were lacking in Korean companies while strategic and strong government supports were missing in public sector. For competing with other countries and players, more active collaboration between different countries and strong policy supports are needed in Korean auto industry.