• 전기전자학회논문지
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• 제7권2호
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• pp.253-259
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• 2003

좋은 3D 엔진이란 객체들의 상호 작용을 실세계와 유사하게 표현하는 물리학 엔진을 말한다. 충돌은 이런 상호작용 중의 하나이며, 충돌 유무 검사와, 충돌 지점, 충돌후의 반응을 다룬다. 대부분의 물리학 엔진과 같이 충돌 검사도 정확하게 검출하려면 많은 시간이 소요된다. 그러나 요구되는 정밀도만 만족하는 모델 사용으로 검출시간을 조절 할 수 있다. 그러므로 요구되는 정밀도와 시간에 따라 충돌 검출 모델을 선정하여야 한다. 본 논문에서는 충돌 검출 모델들을 정확도에 따라 7단계로 구분하여 구현하고 실험했다. 이를 통해 시간과 정확도의 연관 관계를 분석하고, 이에 따른 충돌 검출 모델을 선택하기 위한 기준을 제시하고자 한다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 춘계학술대회논문집
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• pp.407-412
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• 2000

Response surface method is employed in optimizing the acoustic performance of automotive engine-cooling axial fans. The effects of modifications in blade geometry on noise reduction are investigated. Taking the far-field noise level as the objective, a quadratic response surface is constructed utilizing D-Optimality condition as the candidate-points selection criteria. It is shown that the quadratic model exhibits an excellent fitting capability resulting in the blade design with low far-field noise level.

• 한국자동차공학회논문집
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• 제22권5호
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• pp.116-125
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• 2014

Pyrolysis oil (PO), derived from biomass through fast pyrolysis process have the potential to displace significant amounts of petroleum fuels. The PO derived from wood has been regarded as an alternative fuel to be used in diesel engines. However, the use of PO in a diesel engine is very limited due to its poor properties like low energy density, low cetane number, high acidity and high viscosity of PO. Therefore, one of the easiest way to adopt PO to diesel engine without modifications is blended with other fuels that have high centane number. However, PO that has high amount of polar chemicals is immiscible with non polar hydrocarbons of diesel or biodiesel. Thus, to stabilize a homogeneous phase of diesel/biodiesel-PO blends, a proper surfactant should be used. Nevertheless, PO which was produced from different biomass type have varied characteristics and this complicates the selection of a suitable additive for a specific PO-diesel emulsion. In this regard, a more simple approach such as the use of a co-solvent like ethanol or butanol to induce a more stable phase of the PO-diesel mixture could be a promising alternative. In this study, a diesel engine operated with diesel/biodiesel-PO-butanol blends was experimentally investigated. Performance and gaseous & particle emission characteristics of a diesel engine were examined under the engine loads of IMEP 0.2 ~ 0.8MPa.

• 한국추진공학회지
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• 제10권1호
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• pp.64-71
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• 2006

수직이착륙 및 고속 전진비행 능력을 갖는 스마트무인기를 개발하기 위해 채택된 틸트로터방식은 통상의 헬리콥터방식과 터보프롭방식을 모두 포함하고 있다. 엔진측면에서 보면 엔진운용방식, 엔진제어 방식, 동력계통의 동력학적 특성, 흡/배기구 개념, 엔진장착요구도 등과 같은 요인들이 헬리콥터와 터보프롭, 두 가지 방식의 요구조건을 모두 만족시킬 수 있어야 한다. 또한 틸트로터의 특성상 헬리콥터와 터보프롭, 두 모드에서의 최적 로터회전수가 상이하여 이를 만족시킬 수 있는 방안이 요구되었다. 본 연구에서는 기존의 상용터보샤프트 엔진으로부터 틸트로터방식을 위한 특이한 엔진요구사양을 충족 시킬 수 있는 방안을 모색하였으며 이를 위해 가장 적합한 엔진을 선정하게 되었다.

• 한국항공우주학회지
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• 제30권1호
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• pp.105-113
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• 2002

본 연구에서는 터보프롭 엔진의 정상상태 성능해석 프로그램을 개발하고 비 장창 및 장착조건에서 성능이 해석되었다. 개발프로그램의 검증을 위해 GASTURB 8.0프로그램의 해석결과와 엔진 제작사의 주어진 성능자료를 비교하였다. 개발 프로그램은 GASTURB 8.0과의 비교 결과 5%내의 오차를 나타내어 프로그램의 신뢰성을 확인할 수 있었다. 성능진단을 위해 선형 및 비선형 GPA프로그램을 개발하였으며, 최적계측변수의 선정을 위한 연구를 수행하였다. 계측변수의 종류의 수가 진단의 정확성에 미치는 영향을 알아보기 위하여 선형 및 비선형 GPA프로그램은 다양한 변수를 이용하여 해석 되었다. 그 결고 적절하게 선택된 계측변수는 보다 적은 계측장비로도 신뢰성있고 경제적인 손상 탐지가 가능함을 확인하였다.

• 대한전자공학회논문지SD
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• 제44권10호
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• pp.49-54
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• 2007

최근 많은 디지털 콘텐츠들이 3차원 그래픽을 기반으로 제작됨에 따라 모바일 기기에 적용 가능한 저 전력 3차원 그래픽 하드웨어에 대한 관심이 증가하고 있다. 본 논문에서는 이러한 시대 흐름에 맞추어 모바일 기기에 적용 가능한 3차원 그래픽 기하변환 엔진을 설계하였다. 설계된 기하변환 엔진은 매핑 변환 유닛을 투영 변환 유닛에 통합하고 클리핑 유닛을 선별 유닛으로 대체하여 구조를 단순화하고 면적을 줄었다. 설계된 엔진은 IEEE-754 표준을 만족하는 32 bit 부동소수점 형식과 데이터 폭을 줄인 24 bit 부동소수점 형식의 연산을 수행할 수 있으며 이는 파라미터의 변환으로 선택할 수 있도록 하였다. 또한 파이프라인 방식을 설계에 적용하여 초기 지연을 제외하고는 매 사이클 입력되는 정점의 좌표 성분(x, y, z, w)을 연산하여 4 사이클 마다 하나의 변환된 정점 좌표 성분을 출력할 수 있도록 하여 동작의 속도 및 효율을 높였다. 설계된 기하변환 엔진은 FPGA를 이용한 시스템으로 구현되었으며 설계된 엔진을 통해 변환된 3차원 객체가 TFT-LCD에 정상적인 3차원 그래픽 영상을 출력하는 것을 통해 검증하였다.

• Journal of Biosystems Engineering
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• 제43권4호
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• pp.296-302
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• 2018

Purpose: The aim of this study was to determine appropriate threshing and selection conditions for sorghum harvesting using a rice combine-harvester. Methods: Sorghum harvesting performance was tested using an actual rice combine. Through this test, the grain loss rate and the composition of crops according to the engine and fan speeds of the combine were investigated. Furthermore, the optimal threshing and selection conditions were determined by carrying out a harvest test based on the opening size factor of the concave in a test field. Results: The grain loss rate for the sorghum using a concave ($18{\times}18mm$) of the rice combine was the lowest at 0.1% at a chaffer angle of $40^{\circ}$, engine speed of 2000 rpm, and fan speed of 20 m/s, but the sorting sieve clogged frequently. Furthermore, as the engine speed and fan speed increased, the grain loss rate also increased. The sorghum harvesting test results of the combine according to the concave opening size showed that the grain loss rate was 0.5% at a driving speed of 0.5 m/s, with a concave opening diameter of 13 mm, a chaffer angle of $40^{\circ}$, a concave sieve oscillation frequency of 4.8 Hz, a fan speed of 20 m/s, and an engine speed of 2000 rpm. Conclusions: Findings showed that sorghum could be harvested using a head feeding rice combine.

• 한국정밀공학회지
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• 제9권3호
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• pp.53-60
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• 1992

This paper deals with developing an Expert system for tool selection using knowledge base system approach, and its application. For the sake of building of knowledge base, the information from process through sensor, tool handbook and interview with expert are referrenced and managed. The system developed shows good application flexibility in providing the actual cutting process with the selection of tool(insert, holder) and cutting conditions(feed, speed, rake type, and so on), is found as a useful system for real-time machining process. The Expert system for tool selection is written in TURBO PROLOG ver. 2.0 for inference engine capability, and can be run in interactive mode for user friendliness. In order to apply the system developed in actual cutting process, more parameters should be considered and scrutinized, and the system should be further extended in modular basis.

• 한국해양공학회지
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• 제13권3B호
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• pp.38-46
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• 1999

Increasing stringent emissions legislation and requirement of more effective energy used for diesel engine demand the fine control of the fuel injection system. Recently, the electromagnetic fuel injection control system for diesel engine is tried to realize the optimum diesel combustion by the feel back sensing as optical signal of combustion flame. The photo detectors were made for the feed back signal of electromagnetic fuel injection control for small DI diesel engine. Their abilities to detect defining combustion events were examined. By evaluating test results, it was shown that the wider acceptable optical range design of optical probe window face, and selection of installation position and installation method of detector were important point for improving sensing ability. The detector was shown to detect start and end of diffused combustion and maximum point of flame intensity impossible for pressure sensor, and also shown that the maximum point of flame intensity was 75% of accumulated heat release point within the experimental conditions.

• Journal of Information Science Theory and Practice
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• 제5권4호
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• pp.6-25
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• 2017

In this paper, a large-scale study on users' understanding of search-based advertising is presented. It is based on (1) a survey, (2) a task-based user study, and (3) an online experiment. Data were collected from 1,000 users representative of the German online population. Findings show that users generally lack an understanding of Google's business model and the workings of search-based advertising. 42% of users self-report that they either do not know that it is possible to pay Google for preferred listings for one's company on the SERPs or do not know how to distinguish between organic results and ads. In the task-based user study, we found that only 1.3 percent of participants were able to mark all areas correctly. 9.6 percent had all their identifications correct but did not mark all results they were required to mark. For none of the screenshots given were more than 35% of users able to mark all areas correctly. In the experiment, we found that users who are not able to distinguish between the two results types choose ads around twice as often as users who can recognize the ads. The implications are that models of search engine advertising and of information seeking need to be amended, and that there is a severe need for regulating search-based advertising.