• 한국자동차공학회논문집
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• 제3권1호
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• pp.129-135
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• 1995

This study aims to compare the heat release calculated using the ensemble average of pressure data with the heat release calculated using the least squares method for pressure data. This paper propose a heat release computation method that can analyze the most correct, straight and simple method to analyse combustion phenomenon. In conclusion, we found that the least squares method of third-order was the best computational method for heat release calculation.

• 정보처리학회논문지:소프트웨어 및 데이터공학
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• 제2권4호
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• pp.239-250
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• 2013

가용 센서를 내장하고 있는 모바일 디바이스의 사용이 많아지고 자동화, 자율화, 사용자 맞춤식 서비스의 요구가 커짐에 따라 컨텍스트 인지 모바일 컴퓨팅 (Context-Aware Mobile Computing)의 필요성이 증대하고 있다. 하지만 추론 시스템 설계는 컨텍스트 분석, 인지하고자 하는 상황분석 등의 복잡한 과정을 요구한다. 또한 모바일 디바이스의 제한된 자원 때문에 컴퓨팅 파워가 높은 서버에 탑재된 추론 엔진을 통해 추론을 수행하는 것이 적합하다. 본 논문에서는 이러한 과정을 간결하고 정확하게 표현하기 위한 컨텍스트-상황 추론 요소의 범용적 정형 모델을 제안하고 추론 요소들의 정형 모델을 실사례에 적용하여 본 논문에서 제안하고 있는 추론 요소들의 정형 모델이 실효성을 가지고 있으며 범용적임을 보여준다. 또한 제한한 추론 요소들을 컴퓨팅 환경에서 실현화하기 위해 제안한 정형 모델들을 기반으로 추론 엔진을 설계 및 구현하고 추론 실험을 통해 추론 엔진의 실효성과 재사용성을 검증한다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 추계학술대회논문집
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• pp.78-83
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• 2003

General algorithm is developed for the prediction of internal flow-induced noise. This algorithm is based on the integral formula derived by using the General Green Function, Lighthills acoustic analogy and Curls extension of Lighthills. Novel approach of this algorithm is that the integral formula is so arranged as to predict frequency-domain acoustic signal at any location in a duct by using unsteady flow data in space and time, which can be provided by the Computational Fluid Dynamics Techniques. This semi-analytic model is applied to the prediction of internal aerodynamic noise from a throttle valve in an automotive engine. The predicted noise levels from the throttle valve are compared with actual measurements. This illustrative computation shows that the current method permits generalized predictions of flow noise generated by bluff bodies and turbulence in flow ducts.

• 한국게임학회 논문지
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• 제21권4호
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• pp.109-116
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• 2021

In this paper, we considered that recently 3D game characters have been almost alike realistic expression because of a great mathematical computation and efficient techniques on GPU hardware. We presented the rendering technique and analysis for 3D game characters to simulate and render mathematical approach model from recent researches to perform the game engine for the surface reflection of lighting model. We compare our approach with the existing variant rendering techniques here using Open GL shader language on game engine. The experimental result will be provided the view-dependent visual appearance of variant and effective modeling characters for realistic expression using existing methods on the GPU for effective simulations and rendering process. Since there are many operations that are used redundantly while performing mathematical operations, the necessary functions and requirements have been to compute in advance.

• KEPCO Journal on Electric Power and Energy
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• 제8권2호
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• pp.159-179
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• 2022

Often a network becomes complex, and multiple entities would get in charge of managing part of the whole network. An example is a utility grid. While the entire grid would go under a single utility company's responsibility, the network is often split into multiple subsections. Subsequently, each subsection would be given as the responsibility area to the corresponding sub-organization in the utility company. The issue of how to make subsystems of adequate size and minimum number of interconnections between subsystems becomes more critical, especially in real-time simulations. Because the computation capability limit of a single computation unit, regardless of whether it is a high-speed conventional CPU core or an FPGA computational engine, it comes with a maximum limit that can be completed within a given amount of execution time. The issue becomes worsened in real time simulation, in which the computation needs to be in precise synchronization with the real-world clock. When the subject of the computation allows for a longer execution time, i.e., a larger time step size, a larger portion of the network can be put on a computation unit. This translates into a larger margin of the difference between the worst and the best. In other words, even though the worst (or the largest) computational burden is orders of magnitude larger than the best (or the smallest) computational burden, all the necessary computation can still be completed within the given amount of time. However, the requirement of real-time makes the margin much smaller. In other words, the difference between the worst and the best should be as small as possible in order to ensure the even distribution of the computational load. Besides, data exchange/communication is essential in parallel computation, affecting the overall performance. However, the exchange of data takes time. Therefore, the corresponding consideration needs to be with the computational load distribution among multiple calculation units. If it turns out in a satisfactory way, such distribution will raise the possibility of completing the necessary computation in a given amount of time, which might come down in the level of microsecond order. This paper presents an effective way to split a given electrical network, according to multiple criteria, for the purpose of distributing the entire computational load into a set of even (or close to even) sized computational loads. Based on the proposed system splitting method, heavy computation burdens of large-scale electrical networks can be distributed to multiple calculation units, such as an RTDS real time simulator, achieving either more efficient usage of the calculation units, a reduction of the necessary size of the simulation time step, or both.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2002년도 proceedings of the second asia international conference on tribology
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• pp.425-426
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• 2002

Lineal and angular movements of many engine components make the lubricant absorb air and the aerated lubricant greatly influences the clearance performance of contacting behaviors of engine components such as big-end bearing, cam and tappet, etc. This study investigates the behaviors of aerated lubricant in the gap between con-rod bearing and proceeding which is one of the most frictional energy consuming components in the engine. Our assumption for the analysis of aerated lubricant film is that the film formation is influenced by the two major factors. One is the density characteristics of the lubricant due to the volume change of lubricant by absorbing the bubbles and the other is the viscosity characteristics of the lubricant due to the surface tension of the bubble in the lubricant. In our investigation, it is found that these two major factors surprisingly increase the load capacity in certain ranges of bubble sizes and densities. Frictional forces are also influenced by the aerated bubble size and density, which eventually enlarge the shear resistance due the surface tension, Modified Reynolds' equation is developed for the computation of fluid film pressure with the effects of aeration ratio under the dynamic loading condition. From the calculated load capacity by solving modified Reynolds' equation, proceeding locus is computed with Mobility method at each time step.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.1986-1989
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• 2003

This paper proposes the information retrieval improvement for the Web using the structure and hyperlinks of HTML documents along with user profile. The method bases on the rationale that terms appearing in different structure of documents may have different significance in identifying the documents. The method partitions the occurrence of terms in a document collection into six classes according to the tags in which particular terms occurred (such as Title, H1-H6 and Anchor). We use genetic algorithm to determine class importance values and expand user query. We also use this value in similarity computation and update user profile. Then a genetic algorithm is used again to select some terms from user profile to expand the original query. Lastly, the search engine uses the expanded query for searching and the results of the search engine are scored by similarity values between each result and the user profile. Vector space model is used and the weighting schemes of traditional information retrieval were extended to include class importance values. The tested results show that precision is up to 81.5%.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집B
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• pp.806-811
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• 2001

Since the characteristics of combustion and pollutant in Diesel engines were mainly effected by the characteristics of in-cylinder gas flow and fuel spray, an understanding of those was essential to the design of the D.I. Diesel engines. The improvement of volumetric efficiency of air charging into combustion chamber is a primary requirement to obtain better mean effective pressure of an engine. Since parameters such as the air resistances in intake and exhaust flow passages, valve lift and valve shape influence greatly to the volumetric efficiency, it is very important to investigate the flow characteristics of intake and exhaust port which develops air motion in the combustion chamber. In this study, two approach methods were used for design intake and exhaust port; experiment and computation which were made by using steady flow test rig and commercial CFD code. This paper presents the results of an experimental and analytical investigation of steady flow through the prototype cylinder head ports and valves of the HHI's H21/32 HIMSEN Engine.

• 한국해양공학회지
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• 제24권2호
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• pp.47-52
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• 2010

The proper surface pressure on the pistons rings in the diesel engine of a ship is very important, because the pressure controls the oil that is needed to maintain friction at acceptable levels between the pistons and the cylinders. In this paper, basic and theoretical concepts to compute the ring pressure were formulated and applied to obtain the proper surface pressures on selected sample piston rings. During the calculation of the pressure on the piston rings, the computation of the accurate free shape of the piston ring was required. Earlier, Arnold and Prescott introduced theories to compute the free shapes of piston rings, and their approach used rectangular and polar coordinates. In this paper, the free shapes of piston rings using two different theories were computed and compared. The results were quite close, representing the free shape of the piston ring. Ring pressure was computed using the Arnold's free shape that was obtained. A simple GUI was made to compute the surface pressure on the piston rings.

• Journal of Advanced Marine Engineering and Technology
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• 제34권6호
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• pp.887-893
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• 2010

기관실 시뮬레이터에서 3상유도전동기에 대한 모델링을 단순하게 처리하는 경우에는 왜곡된 특성에 의해 각종 전기 기계적 모의 성능 수준이 크게 저하된다. 한편, 전동기 특성을 1, 2차 측 파라미터로 구분하는 기존의 등가회로 방식들은 복잡한 실험을 거치거나 상세 기술 자료가 확보되지 않고는 현장 전동기에 대한 회로에서의 파라미터 값들을 확정하지 못한다는 점에서 정격제원 정도만 주어지는 기관실 시뮬레이터의 개발 작업 환경에서는 사용할 수가 없다. 이러한 문제의 해결을 위해 본 논문에서는 최소 파라미터에 의한 전원 직결의 2 회로정수 방식 등가회로를 제시하였으며 이로부터 정격제원에 의해 회로정수가 결정되기까지의 조건과 과정 및 관련 식들을 해석하였다. 또한 실제 전동기에 이를 적용하여 얻어지는 특성곡선들을 통해 임의의 전동기에 대한 근사특성과 실용성을 확인하였다.