• Journal of the Korean Society of Propulsion Engineers
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• v.18 no.1
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• pp.42-49
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• 2014

Performance evaluation was carried out for the 70 N-class hydrazine thruster whose design performance had been already verified. The pulse-mode firing test was conducted for the development model thrusters with various thrust chamber diameters. Evaluation was made by the performance parameters such as specific impulse, impulse bit, and characteristic velocity, etc: specific impulse and characteristic velocity were deteriorated as the thrust chamber diameter deviates from a standard model. Consequently, it is revealed that the performance characteristics of standard model is most superior among the test models.

• Transactions of the Korean Society of Automotive Engineers
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• v.17 no.5
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• pp.1-6
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• 2009

The temperature of exhaust gas was raised by increasing of engine movement on developing engine. Thermal of high temperature and pressure reverse in bellows, because of increasing of engine movement and the thermal performance of converter in combustion. As a result, thermal loss is increased and thermal efficiency is decreased rapidly in bellows, it can occur to damage in mechanical structure. In this study, it was necessary to analyze back pressure performance and thermal characteristic on driving condition in exhaust system. It was adapted braid type bellows and straight type exhaust pipe. It was compared with curve type exhaust pipe for lay-out on considering to design of exhaust system. It was necessary to improve thermal characteristic and back pressure performance so that expansion cavity pipe(ECP) was installed between bellows and catalyst convert. Not only decreasing back pressure was solved but also thermal characteristic problems in exhaust pipe because of increasing capacity. According to this study, the basis of data is presented when new exhaust system is designed.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.2
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• pp.94-100
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• 2009

In diesel engines, it is inevitable that the torsional vibration is produced by the fluctuation of engine torque. Therefore, it is necessary to establish preventive measures to diminish the torsional vibration. The sleeve spring type damper is one of the preventive measures for reducing the torsional vibration. In this study, a closed form equation to predict spring constant of the sleeve spring and torsional characteristic of the torsional vibration damper was proposed to calculate stiffness of the damper and verified their availability through the finite element analysis. The theoretical values have a good agreement with the results obtained by the finite element analysis. The results obtained from the equation derived enable the designers in actual fields to be more efficient.

• Transactions of the Korean hydrogen and new energy society
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• v.19 no.1
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• pp.1-9
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• 2008

Human has faced in lack of fossil fuel and environmental crisis because of high population growth and development of industry. Hydrogen, unlimited amount and clean resource from water electrolysis, is remarkably known as the solution of recent energy crisis. One of the special characteristics of hydrogen is that a little amount of catalytic such as platinum and palladium makes nonflammable combustion, in other words catalyst combustion. Catalytic combustion fueled by hydrogen is environmentally friendly. This paper considers some comparisons of characteristic of catalytic combustion between a single layer of platinum catalyst, double layer of platinum and nickel catalysts and mixture of platinum and nickel catalysts. Some experiments of temperature distribution at different positions and characteristic of combustion in low temperature region were done in order to find an applicable possibility as a house-cooking burner.

• Korean Journal of Computational Design and Engineering
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• v.18 no.5
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• pp.367-373
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• 2013

In this study, the penetration characteristic from the cubic and cylindrical penetrator consisting of tungsten material with the velocity of 2,300 m/s is evaluated and the penetration possibility into the target is confirmed. The design of shape and size of penetrator is directly related to space and weight of the warhead. AUTODYN-3D simulation is used to study the penetration effect of penetrator. The purpose of numerical analysis is to verify the penetration characteristic with various L/D penetrator. The penetration performance of penetrator with identical weight due to the shape is also confirmed. The cylindrical and cubic penetrator has enough penetration energy on constant target body. Because the possibility of 2'nd penetration is important factor after 1'st penetration into target body, residual velocity of residual mass must be existed as much as possible. As geometrical shape ratio increases, penetration performance is confirmed to improve.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.4
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• pp.554-560
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• 2001

Hydrophilic treatment of the packing materials in a cooling tower has been made by the ion assisted reaction (IAR) method to increase the wettability of the packing materials. The effects of hydrophilic treatment of packing materials on the performance of a cooling tower have been investigated in a wide range of operating parameters, such as water flow rate, air flow rate, and the water inlet temperature. A pilot cooling tower has been designed and built to model a counter-flow cooling tower. The results obtained indicate that the packing characteristic value with hydrophilic packing could be substantially increased by 6∼19.3% than that with conventional packing in the operating ranges considered. The correlations of the packing characteristic value as a function of water-to-air ratio are suggested for a counter-flow cooling tower with hydrophilic packing as well as with conventional packing.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.12
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• pp.1033-1038
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• 2006

We carried out the experiments on particle deposition onto the cleanroom wall panels. And then we investigated the particle deposition characteristic coefficients for electrostatic voltages and particle size. It was found that there is little difference in characteristics of the particle deposition between the steel panel and the anti-static coating panel. In case of that the particle size is under $1.0{\mu}m$, the particle deposition characteristic coefficient becomes larger as the electrostatic voltage induced to the cleanroom wall panel is increasing. Where in case of that the particle size is over $3.0{\mu}m$, the particle deposition characteristic coefficients do not show any differences with the electrostatic voltages. It is due to that the electrostatic force is the major particle transport mechanism for submicron particles, while the gravitational settling is the major particle transport mechanism for overmicron particles when the electro-static voltages are induced to the cleanroom wall panel.

• Transactions of the Korean Society of Automotive Engineers
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• v.23 no.6
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• pp.591-600
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• 2015

The efficiency of a powertrain system of hybrid vehicle is highly dependent on the design and control of the hybrid powertrain system. In other words, the optimal design of the powertrain systems is coupled with optimal control of the powertrain system. Therefore, the solution of an optimal design problem for hybrid vehicles is computationally and timely very expensive. For example, dynamic programming, which is a recursive optimization method, is usually used to evaluate the best fuel economy of certain hybrid vehicle design, and, thus, the evaluation takes tens of minutes to several hours. This research aims to accelerate the speed of efficiency evaluation of hybrid vehicles. We suggest a mathematical treat and a methodological treat to reduce the computational load. The mathematical treat is that the dynamics of system is discretized with sparse sampling time without loss of energy balance. The methodological treat is that the efficiency of the hybrid vehicle is inferred by characteristic loss evaluation that is computationally inexpensive. With the suggested methodology, evaluating a design candidate of hybrid powertrain system is taken few minutes, which was taken several hours when dynamic programming is used.

• Journal of the Korean Geotechnical Society
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• v.25 no.5
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• pp.29-37
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• 2009

Examining the mechanical characteristic of the bamboo net structure is necessary in order to evaluate the influence of bending rigidity of bamboo on bearing capacity, however, there is no equipment to examine such mechanical behavior of the bamboo net structure in the world. In this study, a specific equipment to examine stress-strain behavior characteristics of the structure of bamboo net is developed. In comparison with Bamboo's stress-strain behavior characteristic and vertical stress caused by various dozer equipments, the case of estimating minimum embedded depth considering ground settlement is analyzed.

• Proceedings of the KIEE Conference
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• 2000.11b
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• pp.253-255
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• 2000

This paper describes the operating characteristic analysis of PM-type magnetic circuit breaker for electromagnetic field, electric circuit and mechanical motion problems. Transient calculations based up 2D finite element magnetic field solution including non-linearity of materials. Change of dynamic characteristic from eddy current in mover is quantified from FEM analysis.