• 전력전자학회논문지
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• 제8권5호
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• pp.389-396
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• 2003

직류진원 장치의 부하에 단락이 발생하는 경우 직류전원을 부하로부터 신속히 차단하고 재인가 가능한 새로운 방식의 ac/dc 컨버터를 제안하였다. 제안한 방식의 컨버터 출력전윈은 부하단락시 차단 및 정상상태로 회복시 직류전원을 재인가하여 정격출력전압으로 확립되는데 소요되는 시간이 각각 수백 $\mu\textrm{s}$ 이내에 이루어지는 특징이 있다. 또한 컨버터 출력필터 커패시터는 부하가 단락된 상태에서도 방전하지 않고 거의 정격출력전압을 유지할 수 있으므로 직류전원을 단락상태가 소멸된 정상부하에 재인가시 전압의 오버슈트 없이 신속한 부하전압 확립이 가능하다. 제안한 방식의 컨버터는 기존 방식에 비해 구조가 간단하고 소형경량화 가능한 장점이 있다. 제안한 회로방식에 대한 동작원리 설명 및 특성해석을 하였으며 실험을 통하여 그 유용성을 입증하였다.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2008년도 춘계 학술논문 발표대회
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• pp.99-102
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• 2008

This study investigates the properties of the flow, air content, strength, hydration heat, and the autogenous shrinkage, and the results are summarized as following. As a properties of fresh concrete, the flow increased and the air content decreased as the replacement ratio of BS increased. The time of set delayed as the replacement ratio of BS increased by latent hydraulicity. The compressive strength of hardening concrete was smaller than OPC as the replacement ratio of BS increased at young concrete, however it was more than equal after 28th day and from then on. The rising temperature ratio which occurs by simplicity insulation decreased as the replacement ratio of BS increased, but it increased by latent hydraulicity reaction at the latter half. The length ratio of autogenous shrinkage of OPC was 319×10^-6, however it was shorter when the replacement ratio was 40% as showing 290×10^-6.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2003년도 학술.기술논문 발표회
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• pp.69-72
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• 2003

This study is intended to investigate the fundamental properties of concrete which AE water reducing agent for reduction of bleeding is used, and the properties of bleeding reduction. According to the results, when the adding ratio of AE water reducing agent for reduction of bleeding increases, a range of normal fluidity and aimed air content arc satisfied, setting time is faster than that of normal AE water reducing agent. And bleeding amount decreases, bleeding speed is highest between 60 and 90 min, and sinking depth increases drastically in 60 min. When, AE water reducing agent for reduction of bleeding is added, compressive strength shows a slight variation by air content, but there is not a large influence by addition of AE water reducing agent for reduction of bleeding. Synthetically, it proves that AE water reducing agent for reduction of bleeding satisfies aimed air content in the range of normal slump and can reduce only bleeding without quality variation of compressive strength.

• 대한전기학회논문지
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• 제33권11호
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• pp.456-463
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• 1984

The fast-rising high-voltage pulse generation circuit system of a theta pinch is both theoretically and experimentally investigated. The idealized model of this circuit system is a hybrid circuit system composed of three parts: a lumped circuit part being consisted of a capacitor bank and a spark switch connected in series, another lumped circuit part being consisted of the Blumlein transmission line, whose end load is the pinch coil. the voltage difference between two ends of the pinch coil is formulated by analyzing this hybrid circuit system by means of the law of the signal propagation in the transmission line and Kirchhoff's laws. The expedient numerical method for computer calculation is developed to generate the pulse profile of the voltage difference across the pinch coil. The period of the experimentally measured main pulse is a fourth of the theoretical one neglecting the resistance of the pinch coil. We attribute this discrepancy to the modelling in the theoretical calculation that hte resistance and inductance of the spark switch and capacitor bank are assumed to be constant through discharge. Therefore, we can see that the rise time of the imploding magnetic-field pulse is mainly dependent on the spark switch and capacitor bank.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제53권1호
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• pp.47-54
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• 2004

A new high voltage DC power supply is proposed. The proposed power supply is constructed with several power converters connected in series. It is easy to obtain high DC voltage for the same structure of each power converter. The output DC power of the proposed power supply can be disconnected from the load within several hundred microseconds at the instant of a load short-circuit fault. The rising time of the output DC voltage is also as small as several hundred microseconds, and there is no overshoot of the voltage because all of the output filter capacitors keep undischarged state even in load short-circuit condition. Therefore, the proposed scheme is suitable for the protection of frequent output short-circuit and fast on/off switching of output DC voltage. The proposed power supply has improved features such as simple structure, high power factor, and reduced size and volume compared with the conventional schemes. The operating principle is described and the validity of the proposed scheme is proved through simulations and experiments.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 하계학술대회 논문집 C
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• pp.1710-1713
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• 2002

Recently, the pulsed power system has been used to many applications. Such as remediation of environmental hazards, food sterilization, air pollution control E/P (Electrostatic Precipitator), DeNOx/DeSOx power system, ozone generator, high energy physics, and other power source applications. A pulse energy efficiency for load depends on the rising time, peak value. Pulse duration and impedance matching etc. The pulsed power system generally required for short pulse duration and high peak value was forced to consider its volume and economy. In this paper, we investigated operating characteristics of the CO2 laser using an inductively pulsed power system.

• 한국재난정보학회 논문집
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• 제11권1호
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• pp.149-162
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• 2015

오늘날 도시공간의 확보와 정보 집약형 도시발전을 위하여 고층 건축물의 필요성은 점점 증가하고 있다. 동시에 고층건축물 안전의 중요성이 더욱 부각되어 인위재난 중 고층건물 재난의 관심은 높아지고 있다. 본 연구에서는 전국에서 고층건물이 가장 많은 강남소방서와 가장 적게 소재한 지역에서 재난을 관할하는 중랑소방서를 선정하여 각각의 소방서 소속 현장출동 소방공무원을 설문조사를 실시하여 기술통계를 통해 고층건물 재난관리체제가 가장 잘 갖추어져 있다고 판단되는 강남소방서와 상대적으로 잘 갖추어지지 않다고 판단되는 중랑소방서로 구분하여 비교연구를 하여 고층건물 재난관리체제에 영향을 주는 요인을 실증분석하였다.

• 방송공학회논문지
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• 제2권1호
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• pp.16-23
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• 1997

HDTV의 다음세대 TV로서 주목받고 있는 3D TV의 구현을 위한 주요 기술중 보는이의 시점에 해당하는 영상을 보여주는 다시점 입체영상표시가 중요한 연구대상으로 대두되고 있다. 본 논문에서는 다시점 입체영상표시를 구현하기 위한 기존방법들의 문제점으로 지적되는 많은 연산량 문제를 해결할 수 있는 새로운 알고리즘을 제안한다. 다시점 영상모음을 영상 공간축에서 을로 다운 샘플링(down sampling )하여 다해상도 영상 피라미드를 만들고, 이를 바탕으로 저해상도 EPI에서부터 대응점들을 탐색하고, 그에 해당하는 상위 해상도에서는 하위 해상도에서 탐색한 결과를 확인·교정해 가는 방법을 사용하므로써, 기존의 방법보다 고속처리가 가능하며, 잡음에도 강인한 기법을 제안한다.

• 지역연구
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• 제13권2호
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• pp.45-54
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• 1997

A regional economy is characterized as a spatial economy. However the literature shows that it has been treated as a point economy since space is little recognized in regional modeling due to mathematical complication. This leads to the fact that regional model does not sufficiently represent regional characteristic. This paper attempts to construct a regional growth model in a partial equilibrium framework specifically taking into consideration land as a primary factor. The model is formulated largely neoclassical. Labor is assumed to move in response to differences in the wage rate, while capital is perfectly mobile across regions. The paper shows that two growth equilibrium points exist, one stable equilibrium point and the other unstable equilibrium point. The unstable growth equilibrium indicates the existence of minimum threshold that a region must overcome the minimum threshold to grow constantly. Consequently, directions of regional growth are characterized by two growth paths depending on the initial condition of a region. That is to say, a region below the minimum threshold is converging toward the lower stable equilibrium point over time. When a regional economy initially lies above the minimum threshold, it will grow forever. A regional economy is not thus necessarily converging a stationary is not thus necessarily converging a stationary equilibrium point through factor movement. Finally, the impacts of the presence of agglomeration economies and diseconomies are analyzed through the phase diagram. The paper also shows that agglomeration economies result in lowering the minimum threshold and in escalating the level of stable equilibrium However, when agglomeration diseconomies prevail, the results are opposite, i.e., rising the minimum threshold of growth and lowering the growth level of stable equilibrium.

• 동력기계공학회지
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• 제14권3호
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• pp.77-82
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• 2010

In general, the control valves are essential components in hydraulic systems. Structural changes within the valves remain a challenge because many parameters of valve tend to interact in terms of static and dynamic performance. Therefore, the valve characteristics is applied directly to the stability of hydraulic system. Inner structure of the valve which is used mainly in the industries is made up poppet type and spool type. This paper made a description of the method for numerical analysis and modeling of the valve with a built-in moving part of four-type. Based on the physical parameters of the valves, a numerical model of objected valve is developed using the bond graph method. It is to verified the results that the moving part of four-type has an effect on pressure and flow characteristics. Also, It is analyzed the results which has an effect on response characteristic by angular of poppet valve face and inertia variation of the valve with a built-in moving part. In the results, it is confirmed that the rising and settling time vary with the shape of moving part in valve.