• Proceedings of the KIEE Conference
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• 1989.07a
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• pp.518-521
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• 1989

Recently, PWM cycloconverters that are frequency conversion system have been studied for eliminating do links of conventional converter and inverter systems. A new real-time method for generating PWM patterns is proposed in this paper. This method realizes sinusoidal input and output currents, controllable input displacement factor regardless of load power factor, and maximum output voltage range. Finally, feasibility of the proposed method is confirmed by simulation and experiments.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.411-414
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• 2000

An ultrasonic linear motor was composed of a slider and a stator vibrator including piezoelectric material and elastic material. The ultrasonic linear motors mainly consist of an ultrasonic oscillator which generates elliptical oscillations. Elliptical oscillations are generated by synthesizing two degenerated modes. Direction of vibratory displacement was analyzed by employing the finite element method. So, we could recognize that the direction of the slider's movement was controlled by changing the Phase difference of the drive voltage.

• Archives of Pharmacal Research
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• v.14 no.4
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• pp.298-304
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• 1991

Isoprinosine, an antiviral agent with a bitter taste, has been clinically used up to a maximum of 4 g daily in 4-8 doses. In this investigation, isoprinosine was microencapsulated with ethylcellulose 22 cps, 50 cps and 100 cps by means of polymer deposition from cyclohexane through temperature change. Complete removal of cyclohexane from the microcapsules was necessary, since ethylcellulose-coated microcapsules obtained from cyclohexane medium were heavily solvated with cyclohexane and formed lumps even after drying. The displacement of cyclohexane by n-hexane during isolation of microcapsules (Method III) or the freezing of the anal-washed microcapsules before drying (Mothod II) provided the dried products which were more discrete microcapsules than those which were simply dried in the air overnight (Method I). Method III was especially the most effective procedure in preparing finer and more discrete microcapsules. The drug-release from microcapsules was influenced by the ratio of core to wall, the viscosity grade of ethylcellulose and the overall microcapsule size. The release rate was adequately fitted to both the first-order and the diffusion-controlled processes. It is therefore possible to design the release-controlled microcapsules with ethylcellulose of different viscosity along with various core to wall ratio.

• Proceedings of the KIEE Conference
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• 2000.07b
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• pp.760-762
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• 2000

Hybrid type LPM can be widely applied in the precise position controlled devic because precise linear motion can be directly obtained by the simple control circuit without backlash in the rotary-type stepping motor. Also, LPM can increase the Position resolution, which was limited by mechanical manufacturing limit and characteristic of magnetic material. using micro-step drive method to decrease the noise and vibration further. Especially, Double-side LPM may be replaced the solenoid as the valve driving device without difficulty and give full play to control the valve accurately. Hence, In this paper, magnetic circuit of double-side LPM was confirmed and static thrust force curve according to the relative displacement between stator and mover, was analyzed by the two dimensional finite element method. From this results, we can suppose the excitation current to be controlled optimally.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.3
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• pp.503-512
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• 1990

In this study, a penalty method effective for the case that has no snap-back phenomenon, is proposed and an adaptive method which choose the penalty method or Riks' type method, is suggested for the case of snap-back problem. And for the case that loads are applied to one or more points of a structure, the Riks' method is applied in general, but under certain condition choice of new incremental load parameter is suggested to accelerate the convergence rate. Finally, for the case that displacements of a structure are controlled at one or more points Riks' type method is proposed. In this case, the proposed method is applied in general but under certain condition it is recommended to choose other incremental displacement parameter to eliminate probable divergence. Five examples are analysed and compared with the result of published literature.

• Journal of the Earthquake Engineering Society of Korea
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• v.23 no.6
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• pp.289-299
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• 2019

The tendency to use a probabilistic design method rather than a deterministic design method for the design of nuclear power plants (NPPs) will increase because their safety should be considered and strictly controlled in relation to various causes of damage. The distance between a seismically isolated NPP structure and a moat wall is called the clearance to stop. The clearance to stop is obtained from the 90th percentile displacement response of a seismically isolated NPP subject to a beyond design basis earthquake (BDBE) in the probabilistic design method. The purpose of this study is to analyze the effects of heating and buckling effects on the 90th percentile displacement response of a lead-rubber bearing (LRB) subject to a BDBE. The analysis results show that considering the heating and buckling effects to estimate the clearance to stop is conservative in the evaluation of the 90th percentile displacement response. If these two effects are not taken into account in the calculation of the clearance to stop, the underestimation of the clearance to stop causes unexpected damage because of an increase in the collision probability between the moat wall and the seismically isolated NPP.

• Journal of Electrical Engineering and Technology
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• v.13 no.5
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• pp.1935-1944
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• 2018

With the increase of the production of energy from renewable, it becomes important to look at techniques to store this energy. Therefore, a single winding bearingless flywheel motor (SWBFM) specially for flywheel energy storage system is introduced. For the control system of SWBFM, coupling between the torque and the suspension subsystems exists inevitably. It is necessary to build a reasonable radial force mathematical model to precisely control SWBFM. However, SWBFM has twelve independently controlled windings which leads to high-order matrix transformation and complex differential calculation in the process of mathematical modeling based on virtual displacement method. In this frame, a Maxwell tensor modeling method which is no need the detailed derivation and complex theoretical computation is present. Moreover, it possesses advantages of universality, accuracy, and directness. The fringing magnetic path is improved from straight and circular lines to elliptical line and the rationality of elliptical line is verified by virtual displacement theory according to electromagnetic torque characteristics. A correction function is taken to increase the model accuracy based on finite element analysis. Simulation and experimental results show that the control system of SWBFM with radial force mathematical model based on Maxwell tensor method is feasible and has high precision.

• Journal of Ocean Engineering and Technology
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• v.27 no.2
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• pp.1-7
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• 2013

This paper aims at contributing to the field of ship design by introducing new systematic variation methods for ship hull forms. Hull form design is generally carried out in two stages. The first is the global variation considering the sectional area curve. Because the geometric properties of a sectional area curve have a decisive effect on the global hydrodynamic properties of ships, the design of a sectional area curve that satisfies various global design conditions, e.g., the displacement, longitudinal center of buoyancy, etc., is important in the initial hull form design stage. The second stage involves the local design of section forms. Section forms affect the local hydrodynamic properties, e.g., the local pressure in the fore- and aftbody. This paper deals with a new method for the systematic variation of sectional area curves. The longitudinal volume distribution of a ship depends on the sectional area curve, which can geometrically be controlled using parametric variation and a variation that uses the modification function. Based on these methods, we suggest a more generalized method in connection with the derivation of the lines for a new design compared to those for similar ships. This is the so-called the volumetric balanced variation (VOB) method for ship forms using a B-spline modification function and an optimization technique. In this paper the global geometric properties of hull forms are totally controlled by the form parameters. We describe the new method and some application examples in detail.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.29 no.6
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• pp.563-569
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• 2016

This paper presents the resizing method of columns and beams that considers column-to-beam strength ratios to simultaneously control the initial stiffness and ductility of steel moment frames. The proposed method minimizes the top-floor displacement of a structure while satisfying the constraint conditions with respect to the total structural weight and column-to-beam strength ratios. The design variable considered in this method is the sectional area of structural members, and the sequential quadratic programming(SQP) technique is used to obtain optimal results from the problem formulation. The unit load method is applied to determine the displacement participation factor of each member for the top floor lateral displacement; based on this, the sectional area of each member undergoes a resizing process to minimize the top-floor lateral displacement. Resizing members by using the displacement participation factor of each member leads to increasing the initial stiffness of the structure. Additionally, the proposed method enables the ductility control of a structure by adjusting the column-to-beam strength ratio. The applicability of the proposed optimal drift design method is validated by applying it to the steel moment frame example. As a result, it is confirmed that the initial stiffness and ductility could be controlled by the proposed method without the repetitive structural analysis and the increment of structural weights.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.04a
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• pp.733-739
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• 1999

A theoretical model for flexural behavior of strengthened reinforced concrete beam is developed based on displacement controlled nonlinear finite element method in this study. The developed model is shown to reasonably reproducing the experimental results of variously strengthened reinforced concrete beam. Parametric studies for the strengthened reinforced concrete beam at different loading stages are then performed using this model in order to assess the effect of loading stages at the time of strengthening on characteristic values of strengthened beam under flexure. It was found that depending on loading stages of a beam, deflections at yielding and at ultimate loads are more influenced than corresponding load capacities.