• International Journal of CAD/CAM
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• 제6권1호
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• pp.173-181
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• 2006

In this paper, an integration framework of Geometric Constraint Solving Engine and AutoCAD is presented, and a dynamic geometric constraint system is introduced. According to inherent orientation features of geometric entities and various Object Snap results of AutoCAD, the' proposed system can automatically construct an under-constrained geometric constraint model during interactive drawing. And then the directed constraint graph in a geometric constraint model is realtime modified in order to produce an optimal constraint solving sequence. Due to the open object-oriented characteristics of AutoCAD, a set of user-defined entities including basic geometric elements and graphics constraint relations are defined through derivation. And the custom-made Object Reactor and Command Reactor are also constructed. Several powerful characteristics are achieved based on these user-defined entities and reactors, including synchronously processing geometric constraint information while saving and opening DWG files, visual constraint relations, and full adaptability to Undo/Redo operations. These characteristics of the proposed system can help the designers more easily manage geometric entities and constraint relations between them.

• International Journal of CAD/CAM
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• 제6권1호
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• pp.3-8
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• 2006

The application of three-dimensional (3-D) CAD has been popularized for design and production and digital manufacturing has been spreading in many industrial fields. By simulation of the production process using 3-D digital models, which are the core of CIM (Computer Integrated Manufacturing) system, the efficiency and safety of production are improved at each stage of work, and optimization of manufacturing can be achieved. This paper firstly describes the concept of "simulation based production" in shipbuilding and also digital manufacturing; the 3-D CAD system is indispensable for effective simulation because ship structure is three dimensionally complex. By simulation, "computer optimized manufacturing" can be possible. The most effective fields of simulation in shipbuilding are in jobs where many parties have to cooperate, while existing two-dimensional drawings are hardly observed the whole structures due to interference between structures or equipment of complex shape. In this paper some examples of the successful application in IHIMU (IHI Marine United Inc.) are shown: assembly of a pipe unit, erection of a complex hull block, carriage of equipment, installation of a propeller, and access in an engine room.

• 한국가스학회지
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• 제25권2호
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• pp.34-41
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• 2021

국내에서 사용되는 천연가스가 저열량화 되면서 발생할 수 있는 문제점에 대응하기 위해서는 국내 산업용 가스기기에 미칠 수 있는 문제점을 사전에 파악하고, 이를 기반으로 에너지의 효율적인 사용을 위한 대응방안이 선행되어야 한다. 본 연구에서는 EURO-6 규제를 대응하는 희박연소방식의 천연가스 엔진을 이용할 경우, 저열량 가스의 도입으로 인한 엔진 출력성능과 효율의 저하 문제를 해결하기 위해, 실험을 토대로 한 구체적인 제어방안과 결과를 제시하고자 하였다. 전부하 운전조건인 1,400 rpm의 엔진 회전수에서 스로틀이 전부 개방된 전부하 조건과 정격운전조건의 엔진회전수인 2,100 rpm, 450 Nm의 토크 조건에서 점화시기로 대표되는 제어변수에 의한 개선효과 확인을 위해, 각 가스연료에 대해서 점화시기를 변경하여 열효율 및 배출가스특성을 파악하고 최적화하였다. 전부하조건에서 토크를 기준으로 가장 낮은 값을 보이는 순수메탄의 경우 기준 조건에서 약 2 CAD 정도 점화시기를 진각하면 NOx 배출의 큰 증가 없이 토크를 보상할 수 있다.

• 대한기계학회논문집B
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• 제25권8호
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• pp.1097-1102
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• 2001

For the purpose of development of high performance gasoline engine, the design technique of the 5-valve(3 intake valves) combustion chamber for a subcompact vehicle has been studied. 3 intake valves cylinder heads were designed by using a 3-dimension CAD program, and steady state flow experiments have been performed with these model. The 5-valve engines, which have larger valve opening areas, have larger intake flow rates and higher flow coefficient than the 4-valve engines. The effects of intake port design parameters of a 5-valve engine on the intake flow rate and bore size were studied, and the design guidelines for the 5-valve engine were established.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1993년도 한국자동제어학술회의논문집(국내학술편); Seoul National University, Seoul; 20-22 Oct. 1993
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• pp.1018-1023
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• 1993

In mechanical structure design area, many FEM (Finite Element Method) packages are used. But the design using FEM packages depends on an iterative trial and error manner and general CAD systems cannot cope with the change of parameters. This paper presents a methodology for building a designing system of a mechanical structure. This system can generate the drawing for a designed structure automatically. It consists of three steps: generation of a structure by selection of the parameters, stress analysis, and generation of a drawing using CAD system. FEM module and parametric CAD module are developed for this system. Inference engine module generates the parameters with a rule base and a model base, and also evaluates the current structure. The parametric design module generates geometric shapes automatically with given dimension. Parametric design is implemented with the artificial intelligent technique. In older to the demonstrate the effectiveness of the developed system, a frame set of bicycle was designed. The system was implemented on an SUN workstation using C language under OpenWindows environment.

• 한국CDE학회논문집
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• 제2권1호
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• pp.1-10
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• 1997

Finding the optimum route of ship's pipes is complicated and time-consuming process. Experience of designers is the main tool in this process. To reduce design man-hours and human errors a design expert system shell and a geometric modeler is used to automate the design process. In this paper, a framework of the intelligent CAD system for pipe auto-routing is suggested, which consists of general-purpose expert system shell and a geometric modeler. The design expert system and the geometric modeling kernel have been integrated. The CADDS5 of Computervision is used as the overall CAD environment. The Nexpert Object of Neuron Data is used as the expert system shell. The CADDS5 ISSM is used as the interface that creates and modifies geometric models of pipes. Existing algorithms for the routing problem have been analyzed. Most of them are to solve the 2-D circuit routing problems. Ship piping system, specially within the engine room, is a complicated, large scale 3-D routing problem. Methods of expert system have been used to find the route of ship pipes on the main deck.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1997년도 춘계학술대회 논문집
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• pp.589-594
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• 1997

We have already presented the constraint satisfaction algorithm which could solve the losed loop problem in constraint network by using local constraint propagation, variable elimination and constraint modularization. With this algorithm, we have implemented a knowledge-based system (intelligent CAD) for supporting machine design interactively. In this paper, we present newer constraint satisfaction algorithm which can solve inequalities or under-constrained problems in constraint network, interactively and efficiently. This algorithm is a hybrid type of using both declarative description (constraint represention) and optimization algorithm (Simulated Annealing), simultaneously. The under-constrained problems are represented by constraint networks and satisfied completely with this algorithm. The usefulness of our algorithm will be illustrated by the application to a gear design.

• 한국수소및신에너지학회논문집
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• 제31권3호
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• pp.307-313
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• 2020

The 3.9 liter diesel engine with a mechanical fuel injection system was converted to di-methyl ether (DME) engine and performance optimized. In order to switch to the DME engine, the plunger of the high pressure fuel pump was replaced and the diameter of the injector nozzle was increased. Through this, the disadvantage of DME having low calorific value per volume can be compensated. To optimize the performance, the number of injector nozzle holes, injector opening pressure, and fuel injection timing were changed. As a result, the optimum number of injector nozzle holes was 5, the injector opening pressure was from 15 MPa to 18 MPa, and the injection timing was 15 crank angle degree before top dead center (CAD BTDC). The power was at the same level as the base diesel engine and nitrogen oxides (NOx) emissions could be reduced.

• 한국자동차공학회논문집
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• 제14권4호
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• pp.149-156
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• 2006

This paper investigates the steady state combustion characteristics of LPG homogeneous charge compression ignition(HCCI) engine with variable valve timing(VVT) and dimethyl ether(DME) direct injection, to find out the benefits in exhaust gas emissions. VVT is one of the attractive ways to control HCCI engine. Hot internal residual gas which is controlled by VVT device, makes fuel is evaporated easily, and ignition timing is advanced. Regular gasoline and liquefied petroleum gas(LPG) were used as main fuel and dimethyl ether(DME) was used as ignition promoter in this research. Operating range and exhaust emissions were compared LPG HCCI engine with gasoline HCCI engine. Operating range of LPG HCCI engine was wider than that of gasoline HCCI engine. The start of combustion was affected by the intake valve open(IVO) timing and the ${\lambda}TOTAL$ due to the latent heat of vaporization, not like gasoline HCCI engine. At rich operation conditions, the burn duration of the LPG HCCI engine was longer than that of the gasoline HCCI engine. CAD at 20% and 90% of the mass fraction burned were also more retarded than that of the gasoline HCCI engine. And carbon dioxide(CO2) emission of LPG HCCI engine was lower than that of gasoline HCCI engine. However, carbon oxide(CO) and hydro carbon(HC) emission of LPG HCCI engine were higher than that of gasoline HCCI engine.

• 한국자동차공학회논문집
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• 제14권4호
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• pp.39-48
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• 2006

In this research, in order to study the spray, combustion, and emission characteristics of the common rail DME engine, the target engine was disassembled, and 3D CAD file was constructed using a 3D measurement machine and a rapid prototyping machine. Using the obtained 3D geometry, fine moving meshes are generated, and three dimensional non-steady turbulence flow field and combustion phenomenon including spray were numerically analyzed. As a result, IMEP of DME and diesel in medium and high speed revolution showed similar performance. As the DME fuel start to burn in spray area, the vaporized fuel rapidly spreads squish area in low speed revolution. In the case of DME engine, CO and NOx are relatively consistent with experiment results. It was found that the break-up, evaporation, collision model of DME fuel need to be properly adjusted through matching the characteristics of fuel and injector for further improvement.