• Journal of Ocean Engineering and Technology
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• v.23 no.6
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• pp.17-22
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• 2009

This study presents an investigation of the characteristics of piezoelectric sensors whose main utilization is to measure impact pressure. The piezoelectric sensors were tested from several points of view. Their characteristics were investigated for repeatability, the effect of the diameter, temperature effect, water purity, flush mounting, and AC and DC coupling. Out of these, it was revealed that the temperature effect is very significant. The characteristics of the AC and DC coupling are also very important in understanding the time history of the impact pressure.

• Journal of information and communication convergence engineering
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• v.6 no.4
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• pp.417-420
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• 2008

Solar electric systems have very little impact on environment, making them one of the cleanest power-generating technologies available. While they are operating, PV systems produce no air pollution, hazardous waste, or noise, and they require no transportable fuels. In PV system design, the selection and proper installation of appropriately-sized components directly affect system reliability, lifetime, and initial cost. In this research, we have studied the PWM(Pulse Width Modulation) signals. I proposed an efficient photovoltaic power interface circuit incorporated with a DC-DC converter and a sine-pwm control method full-bridge inverter. In grid-connected solar power systems, the DC-DC converter operates at high switching frequency to make the output current a sine wave, whereas the full-bridge inverter operates at low switching frequency which is determined by the ac frequency. Thus, it can reduce the switching losses incurred by the full-bridge inverter. Full-bridge converter is controlled by using microprocessor control method, and its operation is verified through computer aided simulations.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.614-619
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• 2007

The importance of simulation of plastic flow in the injection mold is increasing as the parts are more complex, but the small-scale enterprises can't afford to invest for the infra individually. CAE (Computer Aided Engineering) service was naturally born based on these needs. This paper presents the engineering collaboration model between the large and the small/medium enterprises in the field of injection molds. Based on the engineering collaboration hub and CAE service, small-scale enterprises could research the necessary technology and develop the proper products. The analysis results of CAE are provided by the integrated visualization system on the web. This paper also deals with the delivery shorting process of CAE service for electric/electronic parts which should meet the needs of customers as soon as possible.

• Management Science and Financial Engineering
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• v.10 no.1
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• pp.77-96
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• 2004

In this paper, we present a dynamic matching methodology for the logistics brokerage agent that intermediates empty vehicles and freights registered to the logistics e-marketplace by car owners and shippers. In this matching methodology, two types of decisions should be made： one is when to match freights and vehicles and the other is how to match freights and vehicles at that time. We propose three strategies for deciding when to match, ie. real time matching (RTM) , periodic matching (PM), and fixed matching (FM) and use Hungarian method for solving the how-to-match problem. In order to compare the performance of the when-to-match strategies, computational experiments are done and the results show that the waiting-and-matching strategies, PM and FM, give better performance than real time matching strategy, RTM. We can expect that the suggested matching methodology may be used as an efficient and effective tool for the brokerage agent in the logistics e-marketplaces.

• Transactions of the Korean Society of Automotive Engineers
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• v.16 no.1
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• pp.152-157
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• 2008

The biodiesel becomes one of the favorite alternative fuel applied to diesel engines. This research aims to understand the physics of spray and combustion characteristics of a biodiesel fuel in a constant volume chamber. For spray visualization, biodiesel was injected into a combustion chamber and a high speed camera was applied at various combustion conditions. To investigate heat-release rates and flame propagations, spark was ignited on a hydrogen fuel for the premixed combustion and then biodiesel was injected directly. In addition, parametric study was made by various geometries of combustion chambers and temperatures of fuels and injection pressures. This technology may contribute to improve the performance of bio-diesel engine and reduce emissions in future.

• Advances in nano research
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• v.5 no.1
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• pp.61-67
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• 2017

A semi-empirical approach to model the temperature effects on I-V characteristics of Carbon Nanotube Field Effect Transistors (CNTFETs) is proposed. The model includes two thermal parameters describing CNTFET behaviour in terms of saturation drain current and threshold voltage, whose values are extracted from the simulated and trans-characteristics of the device in different temperature conditions. Our results are compared with those of a numerical model online available, obtaining I-V characteristics comparable but with a lower CPU calculation time.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 1998.10a
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• pp.331-342
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• 1998

본 연구에서는 공간정보를 활용한 전산망 관리시스템을 개발하고자 한다. 이 시스템은 Spatial Data Manager, Network Manager, 3D Viewer 세 부분으로 구성되었다. Spatial Data Manger는 공간상의 Network 장비 및 각종 시설물의 위치와 속성정보를 보여준다. 속성정보 중에서 IP(Internet Protocol)정보는 Network Manager와 연결된다. Network Manager는 ICMP(Internet Control Message Protocol)를 사용하여 네트워크 상태를 파악한다. 3D Viewer는 사용자가 원하는 위치 및 방향에서 시설물을 볼 수 있도록 한다. Spatial Data Manager의 좌표는 3D Viewer의 Camera 좌표와 연동하여 사용자가 원하는 지역을 동시에 2차원과 3차원형태로 볼 수가 있다. 기존 전산망 관리시스템이 단지 수치적으로 네트워크의 상태에 관한 정보를 보여주던 것에 비하여, 개발된 시스템은 공간 위치를 같이 보여줌으로써 누전, 누수 등과 같이 다른 시설물이 전산망에 미칠 수 있는 영향과 전산망 케이블의 종류에 따라 다른 길이의 제약에 따른 영향 등을 분석할 수가 있다. 또한 다른 시설물의 도면 및 시설물에 관련된 기타 정보를 빠르게 검색할 수 있으므로 전산망관리 뿐만 아니라 통합적인 관리를 할 수 있다. 이를 통해 전산망 관리비용을 줄일 수 있을 것으로 기대된다.

• Korean Journal of Human Ecology
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• v.18 no.5
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• pp.1103-1113
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• 2009

Now in the 21st century, all the industries in our world are rapidly changing, including fashion trends and customers' needs as well. Fashion textile planning is also developing towards the direction where it could satisfy the merged sensitivity and incentive of the customers through an idea. The purpose of this study is to accentuate the importance of fashion material planning in fitting conventional patterns and eco-benign fabric materials. Accordingly, this study is mainly focused on the reflection of fabric planning characteristics to show tradition containing comfort and naturalness. As mixing with established fabrics and blending with natural/functional fabrics, and conforming to the trend of the seasonal fabric, it has developed a new structure and pattern by changing the basic source of traditional patterns to a computer aided design system. Therefore, four different types of items were basically up-graded by fitting it in with traditional patterns.

• Journal of Positioning, Navigation, and Timing
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• v.6 no.2
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• pp.59-70
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• 2017

Since GPS signals are vulnerable to interference and obstruction, many alternate aiding systems have been proposed to integrate with an inertial navigation system. Among these alternate systems, the vision-aided method has become more attractive due to its benefits in weight, cost and power consumption. This paper proposes a loosely-coupled vision/INS integrated navigation method which can work in GPS-denied environments. The proposed method improves the navigation accuracy by correcting INS navigation and sensor errors using position and attitude outputs of a landmark based vision navigation system. Furthermore, it has advantage to provide redundant navigation output regardless of INS output. Computer simulations and the van tests have been carried out in order to show validity of the proposed method. The results show that the proposed method works well and gives reliable navigation outputs with better performance.

• 제어로봇시스템학회:학술대회논문집
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• 1995.10a
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• pp.328-331
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• 1995

A successful, computer-aided design support system can help a process designer focus on making effective design decisions, not merely tedious routine calculations. Such a system is essential to enhance quality of design in terms of economics, environmental benignity, reliability, robustness, and operability. Such a statement is even more accepted when applied to conceptual design problems, where gross design specifications are given while a combinatorial number of design alternatives exists. This paper presents an agent-based approach as a systematic and efficient way to design a design support system for the synthesis of conceptual chemical processes. An agent-based approach allows us to handle design knowledge as an object and thus greatly improve the modularity and reusability of that knowledge. Such modularity and reusability lead to the increased productivity in the development of a design support system and the increased ease in the relaxation of design decisions and the generation of design alternatives, both of which functions are critically important in dealing with the complexity and uncertainty of conceptual design problems.