• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2007.11a
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• pp.125-130
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• 2007

Firing tests have been performed for a 30 tonf-class full-scale regeneratively cooled combustion chamber. It was the first model which has welded construction of the injection head and the combustion chamber. A number of firing tests have been performed to evaluate combustion efficiency, regenerative cooling performance and durability of the combustor. This paper describes the results of firing tests performed at the design and off-design conditions which correspond to the chamber pressure of 60 bar, 68 bar respectively and the O/F ratio of 2.5 and 2.8 respectively. The data at each test condition have provided successful results in terms of combustion performance, combustion stability and durability. The tests are considered to be quite meaningful in the sense that the technologies for kerosene regeneratively cooled combustion chamber are successfully proven.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.869-872
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• 2008

Recently, the effects of high temperature on compressive strength, elastic modulus and strain at peak stress of high strength concrete were experimentally investigated. The present study is aimed to study the effect of elevated temperatures ranging from 20 to $700^{\circ}C$ on the material mechanical properties of high-strength concrete of 40, 60, 80MPa grade. In this study, the types of test were the stressed test and stressed residual test that the specimens are subjected to a 25% of ultimate compressive strength at room temperature and sustained during heating and when target temperature is reached, the specimens are loaded to failure. Or specimens are loaded to failure after 24hour cooling time. tests were conducted at various temperatures ($20{\sim}700^{\circ}C$) for concretes made with W/B ratios 46%, 32% and 25%. Test results showed that the relative values of compressive strength and elastic modulus decreased with increasing compressive strength grade of specimen.

• Composites Research
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• v.34 no.4
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• pp.257-263
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• 2021

Composite materials have been widely applied for fabricating pressure vessels used for storing gaseous and liquid fuel because of their high specific stiffness and specific strength. Accordingly, the accurate measurement of their mechanical property, particularly the burst pressure or fracture strain, is essential prior to the commercial release. However, verification of the safety of composite pressure vessels using conventional test methods poses some limitations because it may lead to the deformation of the load transferring media or provoke an additional energy loss that cannot be ignored. Therefore, in this study, the segment-type ring burst test device was designed considering the theoretical load transferring ratio and applicable displacement of the vertical column. Moreover, to verifying the uniform distribution of pressure of the segment type ring burst test device, the hoop stress and strain distribution of ring specimens were compared with that of the hydraulic pressure test method via FEM. To conduct a simulation of the fracture behavior of the composite pressure vessel, a Hashin failure criterion was applied to the ring specimen. Furthermore, the fracture strain was also measured from the experiment and compared with that of the result from the FEM.

• Journal of the Korean Institute of Gas
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• v.22 no.5
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• pp.72-78
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• 2018

Recent trends in gas safety devices are actively developing and researching wireless gas safety devices in response to the development of wireless technologies and the needs of customers. Although there is controversy over the reliability of wireless, the strength of wireless convenience is increasing the introduction of gas safety devices, a reasonable performance evaluation method is needed to verify the safety and reliability of these devices. This paper amis to propose designing and manufacturing performance assesment equipment and methods for evaluating performance so that the safety and reliability of wireless gas safety devices can be verified and distributed smoothly. So, this study reviews the functions and methods of verifying reliability and safety by investing domestic and foreign the related wireless gas safety devices, produces equipments capable of testing major functions, and presents key performance assessment item and test methods that satisfy the reliability and safety requirements of wireless gas safety devices.

• Journal of the Korean Society for Nondestructive Testing
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• v.21 no.2
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• pp.197-203
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• 2001

Micro-defects induced by design and production failure or working environments are known as the cause of SCC(Stress Corrosion Cracking) in aged structures. Therefore, the evaluation of structural integrity based on micro-cracks is required not only a manufacturing step but also in-service term. So we introduce a new nondestructive inspection method using the magneto-optical film to detect micro-cracks. The method has some advantage such as high testing speed, real time data acquistion and the possibility of remote sensing by using of a magneto-optical film that takes advantage of the change of magnetic domains and domain walls. This paper introduces the concept of the new nondestructive inspection method using the magneto-optical film, also proves the possibility of this method as a remote testing system under oscillating load considering application on real fields by applying the method to four types of specimens.

• Journal of the Korean Geosynthetics Society
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• v.10 no.4
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• pp.81-92
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• 2011

In order to understand evaluation of the seismic stability of a fill dam, we made chambers of 1:100, 1:70, and 1:50 (the ratio of the miniature), considering the law of similarity based on drawings of three representative cross sections. And we measured an increase in acceleration, excess pore water pressure, and vertical/horizontal displacement after applying Hachinohe wave (long period), Ofunato wave (short period), and artificial wave, complying with the domestic standards, in order to evaluate the stability and interaction between the ground, the structure, and fluids based on the measurements. As a result, we could observe that displacement of the target cross section was relatively small compared to the allowed level of 30 cm, ensuring proper stability for an earthquake. Regarding the acceleration measurements, the increase rate was 20% for Hachinohe wave and Ofunato wave but 30% for the artificial wave. With respect to the excess pore water pressure, it was lower than 1 (which is the permissible ratio for liquefaction) ensuring proper stability as well.

• Proceedings of the Korean Society of Computer Information Conference
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• 2008.06a
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• pp.217-224
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• 2008

본 논문에서는 기술자격시스템에 대한 관리 운영상의 효율성을 향상시키기 위하여 내부관리시스템을 설계하고 구현하였다. 비정기성 기술자격시스템은 정보처리 관련기업에 개발 및 구현에 대한 전체적인 사항을 위탁업무로 수행하고 처리 결과에 대한 자료를 시행기관에서 인수하여 내부업무를 처리한다. 이러한 관리체계는 추가적 요구정보에 대한 재처리에 많은 문제점을 내포한다. 부가적인 추가적 요구사항에 대하여 재개발 절차가 필요하며 효율적인 업무처리와 관리체계를 수행하는데 불안정한 요소들을 가지고 있는바, 이러한 문제점을 해결하기 위한 방안으로 특수 자격 분야에 시범적으로 적용한 내부관리시스템을 제안하였다. 제안된 내부관리 시스템의 기능 평가는 시뮬레이션 방식으로 최소 규모의 파일럿시스템에서 구현 기술을 적용하고 검증 한 후 실시간 기술자격 시험에 시범 적용한 결과 처리 과정상의 안정성과 실용성이 인증되어 대단위 자격시스템에 확대 적용할 계획이다. 위탁기관과 연계하여 부가적 요구정보 처리 시 발생되는 추가 개발기간에 대한 문제점을 해결하였으며 안정적인 시스템 운영상태와 최대의 효율성을 보여주었다. 특히 내부관리시스템을 사용하는 전문가와 비전문가그룹으로 이루어진 자격시행기관의 시스템 평가에서 사용자 편리성과 확장성 부문에 탁월한 평가를 도출하였다. 본 논문에서 설계 및 구현한 내부관리 시스템은 다양한 방식과 구성요소를 통합하여 공통영역을 표준화 한 후, 체계적으로 실시간 자격관리시스템에 적용 될 수 있을 것으로 분석되었다.

• Journal of Energy Engineering
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• v.17 no.4
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• pp.212-217
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• 2008

This study carried out the safety evaluation of non-refillable butane can for portable gas range equipped with relief valve for prevention of explosion. The can is heated by electric heater at the real using condition and the extreme condition after installing at a portable gas range for checking the operating pressure and the evaluating suitability of releasing flux. And the possibility of fire or explosion was tested when the gas was released from the relief valve at the real condition. As a result of this safety evaluation test, a non-refillable butane can with relief valve prevents the can from exploding by control of internal pressure.

• Journal of Korea Society of Industrial Information Systems
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• v.9 no.3
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• pp.11-18
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• 2004

It is making researches in questions selection method for examination in web-based education system. Most questions made for these remote examinations use methods of making questions using fixed questions or randomly using item pools or automatically using degree of difficulty. This paper proposes a new examination questions selection algorithm in web-based education system for engineer test. Generally, Engineer test is characterized by adequate examination questions selection for degree of difficulty and equally between all units. Therefore this algorithm selected examination questions equally well as regards degree of difficulty and distribution between all units. This algorithm providers more effective education examination method as compared with previous algorithm.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.16 no.5
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• pp.97-103
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• 2002

The assessment of the condition of a transformer winding which is suspected of having suffered short circuit damage can be difficult. Conventional test such as winding resistance, magnetic current or insulation resistance will only detect damage if a permanent electrical fault exists. Visual inspection of windings necessitates the removal of oil and in many cases only a very small proportion of the winding can be seen. We describe the characteristic of LVI test system and methods to detect the deformation of windings in the power transformers. As the front rise time of recurrent-surge generator pulse less than 1000 ㎱ and the peak value of pulse is about 500 V, we have the good results of detecting winding deformation in the LVI test of transformers.