• Journal of the Korean Society of Propulsion Engineers
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• v.21 no.1
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• pp.36-43
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• 2017

In this study, a pintle injector rocket engine which uses kerosene and liquid oxygen as propellants was manufactured by collecting basic design data and establishing a design procedure. Combustion performance of the liquid rocket engine was investigated by characteristic velocity efficiency with characteristic length of the combustion chamber and total momentum ratio. As a result of hot fire tests, it showed that the engine had shorter characteristic length comparing to those of other type injectors, which was known as recommended value with the propellant combination. Also, the characteristic velocity efficiency was greatly affected by total momentum ratio and almost constant within 1.0~1.5.

• 유체기계공업학회:학술대회논문집
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• 2003.12a
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• pp.361-366
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• 2003

For regenerative pump performance test we made 5 times enlarged and 3 different kinds blade types impeller with similarity. Due to geometrical characteristic of regenerative pump, there are two kinds of groups which effect on performance of it. One is geometric shape of impeller blade and the other is clearance and inlet/outlet head loss. To study performance of regenerative pump with impeller shape changes, we tested it with reducing clearance. And we reconcile performance data in the case of zero clearance and zero inlet/outlet head loss. Finally we could verify the influence of each group.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.38 no.4
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• pp.142-148
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• 2015

Due to advancements in technology and manufacturing capability, it is not uncommon that life tests yield no or few failures at low stress levels. In these situations it is difficult to analyse lifetime data and make meaningful inferences about product or system reliability. For some products or systems whose performance characteristics degrade over time, a failure is said to have occurred when a performance characteristic crosses a critical threshold. The measurements of the degradation characteristic contain much useful and credible information about product or system reliability. Degradation measurements of the performance characteristics of an unfailed unit at different times can directly relate reliability measures to physical characteristics. Reliability prediction based on physical performance measures can be an efficient and alternative method to estimate for some highly reliable parts or systems. If the degradation process and the distance between the last measurement and a specified threshold can be established, the remaining useful life is predicted in advance. In turn, this prediction leads to just in time maintenance decision to protect systems. In this paper, we describe techniques for mapping product or system which has degrading performance parameter to the associated classical reliability measures in the performance domain. This paper described a general modeling and analysis procedure for reliability prediction based on one dominant degradation performance characteristic considering pseudo degradation performance life trend model. This pseudo degradation trend model is based on probability modeling of a failure mechanism degradation trend and comparison of a projected distribution to pre-defined critical soft failure point in time or cycle.

• Journal of the Korea Society of Computer and Information
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• v.20 no.4
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• pp.119-130
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• 2015

This study empirically analyzed at domestic manufacturing and service firms to find any moderating effects of enterprise management strategies and information-oriented development strategies between enterprise characteristic factors and IT adoption performance. Task characteristics were analyzed based on information provision extent, system quality and perceived effects while environmental characteristics based on competition extent, external pressure, environmental uncertainty, etc. As a result it was found that strategic suitability factors had a moderating effect between adoption performance and task characteristic variables such as system quality and perceived effect, environmental characteristics such as competition level, external pressure and environmental uncertainty. However, strategy suitability was found not to have any moderating role between task characteristic information provision extent and adoption performance. These findings indicate that enterprises need to plan and implement corporate management strategies and information-oriented development strategies in close coordination for new IT adoption and spread.

• The Transactions of the Korean Institute of Power Electronics
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• v.6 no.1
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• pp.82-89
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• 2001

This paper proposes several methods to analyze dynamic and static characteristics of HVDC inverter system. The characteristic analysis is essential of the controller and filter design of the HVDC inverter system. Dynamic characteristic can be analyzed with EMTP simulation and static characteristic can be obtained by solving newly proposed load flow equation which includes the filter and load characteristic. New simple per-phase-equivalent circuit is also proposed. In this circuit, HVDC inverter is considered as a current source depending on the on-off status of switch. Dynamic and static characteristic can be analyzed by the proposed per-phase-equivalent circuit. For the optimal filter design, various performance criteria are proposed. The performance index, based on the per-phase-equivalent circuit, is calculated. Voltage harmonics and filter power loss are selected as criteria. Optimization procedure is explained to find optimal passive filter parameters.

• 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 Korea Safety Management & Science
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• v.9 no.3
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• pp.153-163
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• 2007

Over the fast few years, web-based e-Learning have made remarkable progress. According to advance of e-Learning, the evaluation of e-Learning effectiveness and success model become more important. This study had a focus on the effect of system characteristic of e-Learning systems and self-efficacy on learning performance. Data has been collected from 192 person experienced in e-Learning. The questionnaire method was adopted to collect the data for this study. The research was conducted by using SPSS 12.0 and AMOS 4.0. The research results and suggestions of the study are as follow. First of all, system quality and information quality of e-Learning system had positive relationship with perceived usefulness. Second, information quality was related positively to user satisfaction. Third, perceived usefulness was positively connected with user satisfaction. Fourth, user satisfaction and self-efficacy had relation to learning performance.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.8A
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• pp.794-801
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• 2007

In this paper, in order to enhance the performance improvements of both BER and PAPR characteristic for the conventional OFDM system, both circularly polarized waves and carrier interferometry signals which shows the robustic fading reduction effect are applied to the system, and then the performance of the proposed system has been evaluated by computer simulation. From the analysis, it can be seen that the system BER performance can be improved by 2 or 3 dB. Furthermore, it can be also seen that the PAPR characteristic can be markedly reduced.

• Korean Institute of Interior Design Journal
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• v.15 no.2 s.55
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• pp.127-137
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• 2006

In the viewing of public performance arts, it needs to make space construction appropriate for performance purposes, because the section type has an effect on audience's inspection. Therefore, this study researches the intentional characteristics and comprehends the relationship between correlation factors to influence on section type of audience space in performance facilities. In addition to, this study comes under fundamental research to propose the course of standard plan, accord with diverse requirement, in the special performance facilities which will be built up. The results as following; 1) The factors that influence the section type of the audience's space in performing facilities are divided as two elements. The first element is construction of space, viewing environment, and the second element is visual characteristic, and acoustic characteristic. 2) The section type are classified as six types, A-type(Flated type), B-type(Sloped type), C-type(Gabled type), D-type(Arched type), E-type(Reverse arched type), and F-type(Reverse sloped type). 3) Characteristics are deduced by the section type, construction of space and viewing environment are restricted by the characteristics of the section type.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.05a
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• pp.66-70
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• 2010

The performance of 75 ton liquid rocket engine combustion chamber for a space launch vehicle was predicted through firing tests at low pressure. In low pressure tests of 75 ton LRE combustor chamber, the combustion characteristic velocity of 1750 m/sec and the specific impulse of 240 sec were obtained which are higher than the low pressure performance of 30ton combustion chamber. The combustion characteristic velocity of 1770 m/sec and the specific impulse of 278 sec at design point for 75 ton LRE combustion chamber were predicted by using the low/high pressure performance correlation of 30ton LRE combustion chamber.