• 대한전자공학회논문지
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• 제12권4호
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• pp.46-49
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• 1975

Mallory의 회로를 변형하여 변압기를 사용하지 않은 새로운 배전압회로를 구성하였고 직류출력전압의 regulation에 있어서 Mallory의 회로보다 훨씬 우수한 결과를 얻었다. 또 출력파형을 해석하고, 직류출력전압과 출력전류와의 관계를 간결한 반사식으로서 표현하였고 이 관계식이 실험결과와 잘 부합되어 있음을 보였다. In this paper, a new transless voltage doubler circuit which is a modification of Mallory circuit is proposed, Regulation characteristics of the new circuit is much superior to that of Mallory's. The analysis of output waveform is applied, an4 a simple and practical relation between dc output voltage and dc output current is derived. It is shown that this formula is coincide with the experimental results.

• Steel and Composite Structures
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• 제2권2호
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• pp.129-146
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• 2002

This paper describes a series of compression tests carried out on concrete filled double skin tubes (CFDST). Both outer and inner tubes are cold-formed circular hollow sections (CHS). Six section sizes were chosen for the outer tubes with diameter-to-thickness ratio ranging from 19 to 57. Two section sizes are chosen for the inner tubes with diameter-to-thickness ratio of 17 and 33. The failure modes, strength, ductility and energy absorption of CFDST are compared with those of empty single skin tubes. Increased ductility and energy absorption have been observed for CFDST especially for those having slender outer tubes with larger diameter-to-thickness ratio. Predictions from several theoretical models are compared with the ultimate strength of CFDST stub columns obtained in the tests. The proposed formula was found to be in good agreement with the experimental data.

• 대한안전경영과학회지
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• 제4권3호
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• pp.167-175
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• 2002

There are two methodologies to increase transport capacity of railway. One is to invest railroad equipment or vehicles, and the other is to improve operation efficiency through optimization. All of these is intended to increase transport capacity by improving the line capacity. So far, we treat the line capacity as the criteria for evaluating investment alternatives or for restricting train frequencies, and this criteria is calculated statical and experimental numerical formula. But, line capacity has special attribute that changes dynamically according to operational conditions, so there is a need of new line capacity estimation system. The Purpose of this paper is to present a new estimation system of line capacity based on the probability simulation and its applications.

• KCI Concrete Journal
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• 제11권3호
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• pp.211-221
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• 1999

A method to determine the fracture energy of concrete is investigated. The fracture energy may be calculated from the area under the complete load-deflection curve which can be obtained from a stable three-point bend test. Several series of concrete beams have been tested. The Present experimental study indicates that the fracture energy decreases as the initial notch-to-beam depth ratio increases Some problems to be observed to employ the three-point bend method are discussed. The appropriate ratio of initial notch-to-beam depth to determine the fracture energy of concrete is found to be 0.5. It is also found that the influence of the self-weight of a beam to the fracture energy is very small A simple and accurate formula to predict the fracture energy of concrete is proposed.

• 전기의세계
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• 제17권1호
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• pp.21-31
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• 1968

The variation of the voltage has been known to be harmful in the sound operation of motors. It also results in the variation in slip. If the voltage and slip are known, every characteristics of motors can be determined. This paper, therefore, analyzed numerically the characteristics of motors by the formula expressed in the function of both slip and voltage, and then satisfactorily compared with the experimental values. A new per-unit method derived in this paper is shown to be easier and simpler than the conventnional one in determining the relative running characteristics. It has also suggested the minimum allowable voltage when voltage below the rated value was applied to the motor. It is expected to apply to the determination of the characteristics under the voltage variation.

• Steel and Composite Structures
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• 제14권5호
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• pp.453-472
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• 2013

This paper presents the structural behavior of CFRP (carbon fiber reinforced polymer) strengthened CFT (concrete-filled steel tubes) columns under axial loads. Circular and square specimens were selected to investigate the retrofitting effects of CFRP sheet on CFT columns. Test parameters are cross section of CFT, D/t (B/t) ratios, and the number of CFRP layers. The load and ductility capacities were evaluated for each specimen. Structural behavior comparisons of circular and rectangular section will be represented in the experimental result discussion section. Finally, ultimate load formula of CFRP strengthened CFT will be proposed to calculate the ultimate strength of CFRP strengthened circular CFT. The prediction values are in good agreement with the test results obtained in this study and in the literature.

• 전기학회논문지
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• 제62권1호
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• pp.43-48
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• 2013

In this paper, magnetic buoyancy force on nonmagnetic solid object submerged in magnetic liquid was simulated and measured. For the evaluation of the force, a multi-physics approach of hydrostatic equilibrium considering magnetic body force as well as gravity is presented. The magnetic body force should be regarded as an additional forcing term in the momentum equation of hydrodynamics. It is also shown that the virtual air-gap based Kelvin's force formula is a useful method for the calculation of force distribution in the magnetic liquid. The experimental result which was performed by a load-cell measurement system agreed quantitatively well with the numerical one.

• 대한전기학회논문지:전력기술부문A
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• 제48권8호
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• pp.1022-1030
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• 1999

This paper is concerned with the balancing motion formulation and the control of ZMP (zero moment point) for a biped walking robot with balancing joints. The balancing equation of a biped robot can be modeled as the second order non-homogeneous differential equation, which makes it possible to plan the desired trajectories for various gaits or motions. Also, the balancing motion can be defined easily by solving the differential equation without pre-processing or heuristic procedures. The actual experiments are performed on biped walking robot system IWR-III, developed in our Automatic Control Lab. The system has the structure of three pitches in each leg, and one roll and one prismatic type in balancing joints. The walking simulations and the experimental results on IWR-III are shown using the proposed formula and control algorithm.

• Journal of Power Electronics
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• 제16권1호
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• pp.173-181
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• 2016

In this paper, a new technique for harmonic optimization in cascaded H-bridge 7-level inverters is proposed. The suggested strategy is based on minimizing an objective function which simultaneously optimizes the converter utilization and Total Harmonic Distortion (THD). The Switch Utilization Ratio (SUR) is formulized for both the phase and line-line voltages of a 7-level inverter and is considered in the final objective functions. Based upon the SUR formula, utilization ratio enhancement will reduce the value of feeding DC links, which improves the efficiency and lifetime of the circuit components due to lower voltage stresses and losses. In order to achieve more effective solution in different modulation indices, it is assumed that the DC sources can be altered. Experimental validation is presented based on a three-phase 7-level inverter prototype.

• 한국자동차공학회논문집
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• 제14권5호
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• pp.9-16
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• 2006

The present study is to simulate coolant flow in IC engine cooling passages under subcooled nucleate boiling conditions and investigate thermal stress analysis of the solid part. To consider nucleate boiling heat transfer effect, Chen's empirical formula is used through user subroutine programing in CFD code and then nucleate boiling model is compared with Robinson's experimental results, which shows reasonable agreement. This Chen's nucleate boiling model is applied to single cylinder IC engine model and we do cylinder liner thermal stress analysis using commercial FEM code.