• 제어로봇시스템학회:학술대회논문집
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• 1998.10a
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• pp.318-322
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• 1998

An Electro Magnetic Suspension System, which has two floating masses connected with springs and dampers, can not keep its equilibrium when it is solved as an ordinary quartic mathematical model. So, a two dimensional con-troller, designed with quadratic mathematical model assuming the two mass model to be a rigid body, was used. As the result, the system floated stably. Therefore, we measured the transfer performances of this closed loop system contained this controller using the compression signal method proposed by N.Aoshima and identified the parameters of this system. Finally, we compared these parameters with the computing results of quartic mathematical model.

• Proceedings of KOSOMES biannual meeting
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• 2017.11a
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• pp.260-260
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• 2017

• Journal of Power Electronics
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• v.16 no.1
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• pp.74-83
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• 2016

A new family of zero-voltage-transition converters with synchronous rectification is introduced in this study. Soft switching condition for all the converter operating points is provided in the proposed converters. The reverse recovery losses of the rectifier switch body diode are also eliminated. In comparison with the main switch voltage stress, the auxiliary switch voltage stress is reduced significantly. The auxiliary switch does not need the floating gate drive. The auxiliary inductor is coupled with the main converter inductor, and the leakage inductor is used as the resonance inductor. Thus, all inductors of the proposed converter can be implemented on a single core. The other features of the proposed converters include no extra voltage and current stresses on the main converter semiconductor elements. Theoretical analysis for a synchronous buck converter is presented in detail, and the validity of the theoretical analysis is justified with the experimental results of a prototype buck converter with 180 W and 80 V to 30 V.

• International Journal of Naval Architecture and Ocean Engineering
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• v.10 no.2
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• pp.170-179
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• 2018

This paper introduces a new method to study the hydroelastic behavior of hinged Very Large Floating Structures (VLFSs). A hinged two-module structure is used to confirm the present approach. For each module, the hydroelasticity theory proposed by Lu et al. (2016) is adopted to consider the coupled effects of wave dynamics and structural deformation. The continuous condition at the connection position between two adjacent modules is also satisfied. Then the hydroelastic motion equation can be established and numerically solved to obtain the vertical displacement, force and bending moment of the hinged structure. The results calculated by the present new method are compared with those obtained using three-dimensional hydroelasticity theory (Fu et al., 2007), which shows rather good agreement.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.22 no.4
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• pp.635-642
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• 2013

We have prepared a DEMO conveyor device for conveying a large 8G class glass sheet using ahorizontal air-cushion system. This device consists of the body frame and the driving frame that are combined to realize a frame for conveying glass without any contact.The driving frame comprises an air flotation table (bed), drive roller supported at both ends, and ASU. Part of the ASU serves to control the airflow as the chamber consists of a porous pad and fan. Fiber filters replace the porous pad and axial fans serve as an air compressor. In addition, to determine the appropriate glass levitation from the air table, this study examined the design specifications of the applied filter (discharge speed of HEPA and ULPA filters, and flow rate) as well as the height of the and the proper supporting roller height (14mm). Then, after adjusting the position of the ASU and the number of ASUs required to configure the UNIT air floating C/V, we analyzed the height and flatness of the glass and derived the appropriate layout (1140-mm distance between ASUs).

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.2
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• pp.217-224
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• 2014

We have developed the novel device that can extract energy from ocean waves utilizing the heaving motion of a floating mass. The major components of the energy converter are: a floater, a counterweight, a cable, a driving pulley, two idler pulleys, a ratchet, and a generator. The device generates power through the tension force in the cable and the weight difference between the floater and the counterweight. When the system is at static free condition, the tension in the cable is equal to the weight of the counterweight which is minimum. Therefore it is desirable to keep the counterweight lighter than the floater. However, experiments show that during the rise of the water level, the torque generated by weight of the counterweight is insufficient to rotate the driving pulley which causes the cable on the floater side to slack. The proposed application of the tension pulley rectifies these problems by preventing the cable from becoming slack when the water level rises. In this paper, the dynamics model is modified to incorporate the dynamics of the tension pulley. This has been achieved by first writing the dynamical equations for the tension pulley and the energy converter separately and combining them later. This paper investigates numerically the effect of the tension pulley on various physical quantities such as the cable tension, the floater displacement, and the floater velocity. Results obtained indicate that this application is successful in suppressing large fluctuations of the cable tension.

• Bulletin of the Society of Naval Architects of Korea
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• v.26 no.2
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• pp.25-31
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• 1989

Two-dimensional large-amplitude motions in regular harmonic wave are treated in time domain, by satisfying the exact body boundary condition and the linear free surface condition. For the present numerical calculation, the method of free-surface spectral representation with simple source distribution on the instantaneous body surface has been extended to include the effect of the incident wave. Calculations of the wave exciting force are performed for a submerged circular cylinder fixed or oscillating with large amplitude. Especially, nonlinear effects on the time-mean forces are studied in detail. It is shown that relative motion between the body and the fluid particle gives a significant effect on the lift and drift forces. Also, large-amplitude motion of a submerged circular cylinder and that of a floating Lewis-form cylinder are directly simulated in time domain. In the calculation results, some nonlinear effects are shown.

• Journal of the Korea Fashion and Costume Design Association
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• v.17 no.4
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• pp.1-14
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• 2015

This study mainly analyzes that designing patterns of an adult women Jeogori that takes advantage of patterns from each textbooks and complements the disadvantages based on the analysis of data from the dress evaluation and comparison of materials. The modification of a size specification is needed for the standard body as an adjust of the length of Jogori between front and back, mediation for bust width between front and back, a movement for the based line of Sup and Godae. As a result, the suitable pattern according to the standard somatotype is as below. Jeogori Length of front is determined by the length of back which was measured from side neck point to bust point plus three centimeters, and give three and half centimeters more in front. This three and half centimeters is for the curved in front of your body due to the chest. Bust width of front and back have to show the differences of human body. Bust width of front is calculated as bust girth into quarters and add two centimeters. Bust width of back gives one centimeter behind the curve from the center line in order to reduce the floating phenomenon. So, the amount of center back line dart is one centimeter. Arm hole girth measures as dividing bust girth into four. Also, Goedae width has two methods to measure. First, divide bust girth into ten equal parts and subtract 0.5 centimeters from it. Second, measure neck girth and divide it by four. Sleeve length is equal to Hwajang minus bust width of front. Hand wrist calculates in using bust girth. Make bust girth into quarters and multiply three fifths. Side line measures as deducting from Jeogori length of back to Arm hole girth and multiply two thirds.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.31 no.2
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• pp.202-209
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• 1998

A three-dimensional numerical method based on the Green's integral equation is developed to predict the motion response and drift force in waves for the ocean monitoring facilities. In this method, we use source and doublet distribution, and triangular and rectangular eliments. To eliminate the irregular frequency phenomenon, the method of improved integral equation is applied and the time-mean drift force is calculated by the method of direct pressure integration over the body surface. To conform the validity of the present numerical method, some calculations for the floating sphere are performed and it is shown that the present method provides sufficiently reliable results. As a calculation example for the real facilities, the motion response and the drift force of the vertical cylinder type ocean monitoring buoy with 2.6 m diameter and 3,77 m draft are calculated and discussed. The obtained results of motion response can be used to determine the shape and dimension of the buoy to reduce the motion response, and other data such as the effect of motion reduction due to a damper can be predictable through these motion calculations. Also, the calculation results of drift force can be used in the design procedure of mooring system to predict the maximum wave load acting on the mooring system. The present method has, in principle, no restriction in the application to the arbitrary shape facilities. So, this method can be a robust tool for the design, installation, and operation of various kinds of the floating-type ocean monitoring facilities.

• Journal of Aquaculture
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• v.17 no.3
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• pp.180-186
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• 2004

This study was carried out to obtain the fundamental data for the mass seedling production of grunt, Hapalogenys nitens in terms of the natural spawning and some characteristics of the eggs spawned. The wild grunt were reared at indoor tanks for three years. The adults spawners were 34.0∼44.0 cm (38.6$\pm$4.0 cm, n=7) in total length, 1.00∼2.23 kg (1.62$\pm$0.50 kg, n=7) in body weight. Spawning were observed 9 times from September 22 to October 1, 2000 and 37 times from August 22 to October 3, 2001, with a water temperature range of 19.8$\pm$28.5$^{\circ}C$. The total number of eggs collected was 2.29${\times}$10$^{7}$ (1.7${\times}$10$^{3}$/ml). The relative proportion of floating eggs to total eggs was 41.7%. The fertilization rate of floating eggs was ranged between 85.0 and 99.9% and the hatching rate was ranged between 2.9 and 93.0%. Fertilized eggs were buoyant and spherical in shape, and were 0.85∼0.98 mm in diameter. Each egg contained 1-5 oil globules which were, 0.18∼0.25 mm in diameter. The incubation time from fertilization to blastodisc formation was 10 minutes, to blastula was 3 hours, and to the hatched larvae at 26$^{\circ}C$ was 20 hours 30 minutes. The newly hatched larvae attained total length of 1.81$\pm$0.18 mm. The time required from fertilization to hatching was 31∼34 hours at 23$^{\circ}C$ and 17∼20 hours at 29$^{\circ}C$.