• Journal of the Korean Society of Propulsion Engineers
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• v.17 no.1
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• pp.89-96
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• 2013

Combustion pressures were measured to study combustion stability for an oxygen rich preburner by both of static and dynamic pressure sensors. The resolutions of each static and dynamic pressure sensor are the 1,000 Hz and 25,600 Hz, respectively. The nominal combustion pressure of the preburner was 200 bar but 80 bar was used at the several initial tests for the safety reason. Two stage ignition was applied to reduce the ignition impact for every tests including the tests with 200 bar combustion pressure. The tests lasted for 10 sec. max. and a little fluctuations of pressure was observed during the main mode. The measured pressures were studied by FFT analysis and no noticeable frequency coupling was found. Thus the preburner can be regarded as stable and it can be utilized for further study on staged combustion cycle liquid rocket engine.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2012.05a
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• pp.76-80
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• 2012

Uni-element preburners using a oxidizer-rich triplex injector have been designed and tested. During combustion tests 1L mode high-frequency instability of 1100 Hz and low-frequency instability of 100 Hz were observed. High-frequency instability has been suppressed by reducing chamber diameter and applying turbulent rings in combustion chamber. Recently, research to reduce low-frequency instability is in progress.

• Journal of the Korean Society of Propulsion Engineers
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• v.17 no.3
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• pp.67-75
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• 2013

The numerical analysis for the verification of preburner's cooling characteristics applying to kerosene-LOx rocket engine has been fulfilled. The distribution of combustion gas properties in primary combustion zone was calculated by the mixture ratio based on head injector arrangement, the properties of oxygen flowing in wall channels as coolant were applied under real-gas conditions, and multi-phase mixing model was employed to calculate the mixing process of primary combustion zone with liquid oxygen which was used for wall cooling. The results of numerical analysis were compared with the experimental results, hence thermo-physical properties in cooling channels and a combustor could be quantitatively identified.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2012.05a
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• pp.65-69
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• 2012

An oxygen rich preburner was tested and the responses from the pressure sensors were studied with FFT analysis. Since the limited capability of the static sensor, less than 250 Hz frequency domain was investigated and compared to the results of the dynamic sensors. As a result, 60 Hz harmonics were presented dominant in the combustion pressure and oxygen inlet pressure. While similar harmonics were shown with the dynamic sensor, it indicated that harmonics less than 60 Hz were very minor and the high frequency is more important.

• KOREAN POULTRY JOURNAL
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• v.12 no.6 s.128
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• pp.95-98
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• 1980

최근 양계기술이 발전함에 따라 경영규모도 대단위 전업 양계업을 경영하는 수가 점차 증가추세에 있으나 실제적으로는 아직도 양계의 기초부문을 망각하고 사양관리 및 운영을 하는 경우가 종종 있음을 볼 수 있다. 양계업을 경영하는 사람이라면 누구나 알아야 하고 알 수 있는 상식적인 기초 마저도 응용하지 못하여 양계산물을 판매할 때 막대한 경제적 손실을 보면서도 모르고 지나가는 합리적인 경영이 못되는 모순을 안고 있다. 또한 전혀 양계분야를 모르는 사람이 양계에 뜻이 있어 시작하려고 할 때 무엇부터 하여야 할지 모르는 상황에 당황하여 사고를 유발시키고 소기의 목적도 달성치 못하고 도중에 중단하는 예가 많아지고 있다. 이와같은 경우에 조금이라도 도움이 되었으면 하는 마음으로 사양기술의 전문적인 것을 떠나 일반적이고 기초적인 부분을 서술하도록 하겠다.

• The Korean Journal of Financial Management
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• v.26 no.3
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• pp.103-138
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• 2009

In this article we examine a unique data set of intraday fair disclosure(FD) releases to shed light on market efficiency within the trading day. Specifically, this paper analyze the response of stock prices on fair disclosure disseminated in real-time through KIND(Korea Investor's Network for Disclosure) on Korea stock exchange during the period from January 2003 to September 2004. We find that the prices of stock experiences a statistically and economically significant increase beginning seconds after the fair disclosure is initially announced and lasting approximately two minutes. The stock price responds more strongly to fair disclosure on smaller firm but the response to fair disclosure on the largest firm stock is more gradual, lasting five minutes. We also examine the profitability of a short-term trading strategy based on dissemination of fair disclosure. After controlling for trading costs we find that trader who execute a trade following initial disclosure generate negative profits, but trader buying stock before initial disclosure realize statistically significant positive profit after two minute of disclosure. Summarizing overall results, our evidence supports that security prices on Korea stock exchange reflects all available information within two minutes and the Korea stock market is semi-strongly efficient enough that a trader cannot generate profits based on widely disseminated news unless he acts almost immediately.

• Journal of the Korean Society of Propulsion Engineers
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• v.17 no.4
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• pp.81-88
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• 2013

It was designed and tested at the design point that an oxidizer rich preburner for a staged combustion liquid rocket engine propelled by kerosene and LOx. The oxidizer rich preburner was designed as some of LOx injected from the mixing head was burned with kerosene and the rest of LOx injected from injection holes in the regenerative cooling chamber was vaporized by combustion gas. The preburner is operated at OF ratio of 60 and combustion pressure of 20 MPa. The Preburner has a honey-comb type mixing head with simplex swirl injectors, a turbulence ring improving combustion stability and uniformity of product gas temperature distribution, and a nozzle simulating the duct. With the combustion test results at the design point, the oxidizer rich preburner showed high combustion stability and uniformity of product gas temperature distribution.

• Proceedings of the Korean Information Science Society Conference
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• 2005.11a
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• pp.295-297
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• 2005

EDI는 기업과 기업간의 거래에서 종은 방법이지만 중소기업이나 소기업에서는 EDI의 도입이 기술적으로나 비용적으로 어려운 게 사실이다. 이 경우 ebXML을 이용하여 EDl를 대신할 수 있다. ebXML을 이용하여 B2B환경을 구축할 경우 ebXML문서를 서로 주고 받는데 메시징 서비스 엔진이 필요하게 된다. 본 연구에서는 ebXML기반의 B2B환경에서 활용할 수 있는 메시징 서비스 엔진을 설계하고 구현하였다. 또한 실제 ebXML메시지를 전송할 때 발생하는 오류를 해결하기 로그를 기록하여 분석할 수 있도록 개발하였다.

• The Journal of Society for e-Business Studies
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• v.6 no.3
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• pp.17-40
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• 2001

In this study we tried to measure the user satisfaction with IT in small firms. Though the number of small firms is not negligible, most studies on the IT satisfaction focused on medium and large-sized firms. Using Palvia's model in 1999 we measured If satisfaction of the employee in small firms in the manufacturing and telecommunication industry. We included seven constructs such as S/W pertinence, information content and accuracy, information format, system usefulness, system continuance, and system support to measure IT satisfaction. The result suggests that the If users in small firms are generally dissatisfied with the information technology and the areas of deep dissatisfaction are system usefulness and system support. Type of business, the gender and education of the users are found to affect the level of satisfaction.

• Journal of Families and Better Life
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• v.19 no.4
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• pp.121-135
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• 2001

This study examines the real states of family businesses through the interview to the owners and their family members of 15 family businesses. Contents of the interview are starting process, goal and long-run plan, marketing, human resource management and financial management. Many owners usually start their business because of unemployment or shortage of job opportunity. So they dont have an business experience or management skill. And owners act passively in sales because they think the sales area is restricted and their stores are well-known. Family members, especially housewives, suffer role conflict and dissatisfaction because there are no rules on wage and responsibility. And many owners use the resource of household to business and vice versa. This is an advantage of family business in the viewpoint of effective use of resource, but it is a confusion of resources in the viewpoint of financial management.