• 대한전기학회:학술대회논문집
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• 대한전기학회 1988년도 전기.전자공학 학술대회 논문집
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• pp.402-405
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• 1988

With dichromated bleacher and alcohol drying, over effi. of 81% has been achieved for holographic gratings. It is recorded by two plane waves at 632.8 nm in Agfa 8E75 film. Swollen emulsion and rapid dehydration make a strong modulation. The model works well close to the Bragg condition. It is suggested modified parameters of coupled-wave theory which have good agreement with experimental results.

• 한국분무공학회지
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• 제8권2호
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• pp.7-15
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• 2003

The effects of fuel density and fuel viscosity on spray characteristics were investigated under two different gas turbine fuels and various fuel supply pressure conditions through measurement of SMD, number density and volume flux by using PDPA system in dual orifice injector for gas turbine engines. In this study, we found out that the droplet size and spray structure are strongly depend on fuel density for dual orifice injector. The spray characteristics of high density fuel in dual orifice injector are similar with the characteristics of low density fuel in single orifice injector. The shear region between primary main fuel stream and secondary main fuel stream is examined in low density fuel condition but not exist in high density fuel condition, then this shear region is very important in quality of gas turbine spray. There are worth consideration for the effect of fuel density on spray characteristics in frontal device design to improve combustion efficiency.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2001년도 제17회 학술발표회 논문초록집
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• pp.61-67
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• 2001

Hybrid propulsion systems provide many advantages in terms of stable operation and safety. However, classical hybrid rocket motors have lower fuel regression rate and combustion efficiency compared to solid propellant rocket motor. The recent research efforts are focused on the improvement of volume limitation and regression rate in the hybrid rocket engine. The present study has numerically investigated the combustion processes in the hybrid rocket engine. The turbulent combustion is represented by the eddy breakup model and Hiroyasu and Nagle and Strickland-Constable model are used for soot formation and soot oxidation. Radiative heat transfer is modeled by finite volume method. To reduce the uncertainties for convective heat transfer near solid fuel surface having strong blowing effect, the Low Reynolds number k-$\varepsilon$ turbulent model is employed. Based on numerical results, the detailed discussion has been made for the turbulent combustion processes in the vortex hybrid rocket engine.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 춘계학술대회 논문집
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• pp.147-150
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• 2008

Changes in land uses at urbanizing areas are causing flooding, increase in NPS pollutants. Thus, Low Impact Development (LID) concept is now being employed in urban planning for sustainable development. Compared with the conventional BMPs, the LID is a new concept in urban planning to minimize the impacts of urbanization for site-specific LID IMPs. The objective of this study is to analyze the efficiency of LID adoption in study watershed in peak rate runoff and runoff volume reduction perspectives. The analysis revealed that the peak rate runoff and runoff volume decreased significantly with the LID adoption. This indicates that the Bimodal tram route with grass installed at the center of the road will contribute reduction in surface runoff and peak rate runoff, and also in NPS pollutant generation from the Bimodal tram route.

• 지능정보연구
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• 제4권1호
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• pp.1-10
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• 1998

Process planning is a very complex task and requires the dynamic informatioon of shop foor and market situations. Process plan selection is one of the main problems in the process planning. In this paper, we propose a new process plan selection model considering operation flexibility for the computer aided process planing. The model is formulated as a 0-1 integer programming considering realistic shop factors such as production volume, machining time, machine capacity, transportation time and capacity of tractors such as production volume, machining time, machine capacity, transportation time capacity of transfer device. The objective of the model is to minimize the sum of the processing and transportation time for all parts. A genetic algorithm a, pp.oach is developed to solve the model. The efficiency of the proposed a, pp.oach is verified with numerical examples.

• 한국초전도ㆍ저온공학회논문지
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• 제14권1호
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• pp.34-37
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• 2012

In this paper, configurations and performance of a pulse tube engine (PTE) are investigated. The configuration of PTE is basically designed by using a concept of energy flow. The configurations of PTE are classified as a PTE with two pistons and a PTE with one piston. First, the PTE with two pistons is simulated and the Carnot efficiency is about 41 %. The phase difference of between motion of two pistons located at expander and compressor mainly effects the performance of the PTE. Second, the PTE with one piston is designed. From a concept of analogy, the piston of compressor is replaced by a compliance tube and a resonator. The PTE with one piston is identical with a thermoacousic engine and has the large volume because the compliance tube and resonator are consisted of large volume tubes. Therefore, we will consider each usefulness of the compact PTE with two pistons and the huge PTE with one piston for PTE applications and the judgement of feasibility.

• 해양환경안전학회:학술대회논문집
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• 해양환경안전학회 2001년도 춘계학술발표대회
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• pp.105-133
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• 2001

World trade has been increasing continuously in total volume, on the other hand, environmental protection on sea and conservation of fishery resources has been rising up the major issue. All of the world are pushing their efforts two major purposes to the full, one is taking competitive place in marine transportation throughout the world and another Is environment protection. Pusan Port as world leading Port put its all effort in bring more ocean going vessels and securing their traffic route by providing them more information related marine traffics through PTMS in port. During two years of operation, statistics of marine traffic accidents showed that many dynamic casualties such as collisions, groundings, and rammings has been decreased. However, due to increasing cargo volume, limited water area and unpredictable weather condition, potential risks still exist high. In this paper, in order to maximize the efficiency of PTMS and reduce various risks in the future, we examine risk factors over operational results and experience, and propose reasonable operational methods of PTMS.

• Advances in environmental research
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• 제5권4호
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• pp.263-282
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• 2016

Contaminant transport in groundwater induces major threat and harmful effect on the environment; hence, the fate of the contaminant migration in groundwater is seeking a lot of attention. In this paper a two dimensional numerical flow and transport model through saturated layered soil is developed. Groundwater flow and solute transport has been simulated numerically using proposed model. The model implements the finite volume time splitting method to discretize the main equations. The performance, accuracy and efficiency of the out coming numerical models have been successfully examined by two test cases. The verification test cases consist of two-dimensional, groundwater flow and solute transport. The final purpose of this paper is to discuss and compare the shape of contaminant plume in homogeneous and heterogeneous media with different soil properties and control of solute transport using a zone for minimizing the potential of groundwater contamination; furthermore, this model leads to select the effective and optimum remedial strategies for cleaning the contaminated aquifers.

• Steel and Composite Structures
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• 제27권2호
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• pp.177-184
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• 2018

This study contributes to evaluate multiphase topology optimization design of plate-like structures on elastic foundations by using classic plate theory. Multi-material optimal topology and shape are produced as an alternative to provide reasonable material assignments based on stress distributions. Multi-material topology optimization problem is solved through an alternative active-phase algorithm with Gauss-Seidel version as an optimization model of optimality criteria. Stiffness and adjoint sensitivity formulations linked to thin plate potential strain energy are derived in terms of multiphase design variables and Winkler-Pasternak parameters considering elastic foundation to apply to the current topology optimization. Numerical examples verify efficiency and diversity of the present topology optimization method of elastic thin plates depending on multiple materials and Winkler-Pasternak parameters with the same amount of volume fraction and total structural volume.

• 대한기계학회논문집A
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• 제27권9호
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• pp.1546-1554
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• 2003

Efficient layout in a fixed work volume reduces build time when multiple parts are built at once in stereolithography systems. An efficient algorithm is developed for 3D layout planning. And it reduces build time and increases efficiency of SLA system. Genetic algorithm is implemented to locate as many parts as possible in the fixed work volume. A 3D collision detection algorithm, k-DOPs Tree, is implemented for the fast evaluation of a layout plan.