• Journal of Ocean Engineering and Technology
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• v.24 no.1
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• pp.133-139
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• 2010

From the ancient times, there are waves in the ocean. And all the moving body have energy. We have a kind of hope to convert the wave energy into electric one. Finally we can find out a power generator mechanism that mainly use the principle of pulleys. We have made drawings for this and completed the wave energy converter. This wave energy converter consists of several pulleys, rope, generator, buoys and anchors. The distance between an anchor and buoy is changed according to the hight of waves. Several sets of anchors, pulleys and buoys can make the movement of rope, and the ropes wind up a converter axis. In case of 1 meter movement of the buoy, the winding distance will be amplified 2 or 3 times if we use several moving and fixed pulleys. Based on this concept, we developed 2 kind of prototypes. One is for the test in the laboratory and the other is for the field test. Through the two test, we could confirm the usability of this mechanism.

• The Journal of the Acoustical Society of Korea
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• v.24 no.5
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• pp.271-281
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• 2005

An electromagnetic type shock wave generator suitable for extracorporeal shock wave therapy has been constructed by employing a solenoid coil. The Property of the shock waves produced by the shock wave generator was evaluated using a needle hydrophone. It was shown that, as the capacitor discharging voltage increased from 8 to 18 kV, the Positive Peak Pressure (P+) of the shock wave increased non-linearly from 10 to 77 Wa. In contrast. the negative peak Pressure (f) varied between -3.2 and -6.8 MPa. had its absolute maximum of -6.9 ma at 14 kV The peak amplitudes P+ measured repeatedly under the same voltage setting varied within $5\;\%$ from mean values and this is very small compared to about $50\;\%$ for electrohydraulic type shock wave generators. It could be observed, from the hydrophone signal recorded over 1 ms. several sequential acoustic impulses representing bubble collapses. namely. acoustic cavitation. induced by the shock wave. A technique based on wavelet transformation was used to accurately measure the time delay between the 1st and 2nd collapse known to be closely related to the shock strength. It was observed that the measured time delay increased almost linearly from 120 to $700\;{\mu}s$ with the shock wave Pressure P+ increasing from 10 to 77 MPa.

• Journal of the Korean Society for Marine Environment & Energy
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• v.17 no.3
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• pp.174-181
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• 2014

Design procedure of LEG(Linear Electric Generator) is introduced by performing the time-domain analysis for the heaving motion of a floating buoy coupled with LEG. A vertical truncated buoy is selected as a point absorber and a double-sided Halbach array mover and cored slotless stator is adopted as a linear electric generator. LEG with a double-sided Halbach array mover and cored slotless stator is designed with the input data such as the heave motion velocity and wave exciting forces in time-domain. The validity of designed LEG is confirmed by performing generating-characteristic-analysis under the sinusoidal motion of a buoy, based on the numerical techniques such as FE(Finite Element) analysis. In particular, an ECM(Equivalent Circuit Method) is employed as the design tool for the prediction of generating characteristics under irregular wave conditions. Finally, we confirm that the ECM gives reasonable and fast results without sacrifice of accuracy.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.3
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• pp.771-783
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• 1996

A desing technique of 8 ports variable wave impedance generator (8P-VWIG) is described. The design technique employs not only a numerical algorithm to find the structure with arbitrary characteristic impedance, but also a numerical solution to analyze the uniform elementrognentic fields established inside the generator. The 8P-VWIG so obtained is shown to have good performance with the VSWR of less than 1.4 at any frequency of interest below which higher order mode begin to propagate. The measured first resonant frequency is 152.1 MHz. The 8P-VWIG is designed based on the concept of an expanded multi-transmission line(8 channel). It is especially useful for the electronmagnetic interference(EMI) and electronmagnetic susceptibility(EMS) testing since it maximizes usable test crosssectional area, and its is easy change the polarization, vertical or horizontal, of field.

• Nuclear Engineering and Technology
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• v.41 no.6
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• pp.841-848
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• 2009

A simple model to analyze non-linear density-wave instability in a sodium-cooled helically coiled steam generator is developed. The model is formulated with three regions with moving boundaries. The homogeneous equilibrium flow model is used for the two-phase region and the shell-side energy conservation is also considered for the heat flux variation in each region. The proposed model is applied to the analysis of two-phase instability in a JAEA (Japan Atomic Energy Agency) 50MWt No.2 steam generator. The steady state results show that the proposed model accurately predicts the six cases of operating temperatures on the primary and secondary sides. The sizes of three regions, the secondary side pressure drop according to the flow rate, and the temperature variation in the vertical direction are also predicted well. The temporal variations of the inlet flow rate according to the throttling coefficient, the boiling and superheating boundaries and the pressure drop in the two-phase and superheating regions are obtained from the unsteady analysis.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.26 no.12
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• pp.80-86
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• 2012

The high-voltage pulse generator is consist of transformers of fundamental wave and harmonic waves, and shunt capacitances. The pulse has the fundamental wave and the harmonic waves that have been increased as a series circuit by the transformers to make high voltage pulse. This paper shows the high-voltage pulse generator simulation using a circuit program with experiment data. In the equivalent circuit, magnetized inductances and loss resistances which affect output voltage, have been obtained. The output capacitor circuits have characteristics of band pass. The output voltages of the pulse width 50% and 25%(PWM) were obtained. The output of the high-voltage pulse generator is 2.5kHz, 1.8kV.

• Journal of the Korean Society for Marine Environment & Energy
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• v.19 no.2
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• pp.120-128
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• 2016

This paper describes power generation from sea waves by using linear permanent magnet generator. A buoy is placed on the ocean surface and connected to the generator. The wave energy is carried out from the movement of a buoy. An electrical conversion system is needed between the generator and the grid. For an analysis of the power system, the modeling of the linear generator and converter system was proceeded. This paper proposes vector control method for wave power generation system using linear generator. In order to verify the proposed method, simulation and experiment performed and the results support the validity of the control scheme.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.28 no.5
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• pp.82-91
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• 2014

The combined generator system by integrating several renewable energy sources can share the electrical infrastructure and therefore have the advantage of constructing not only the transmission system but also the power conversion system. Among the various combined renewable system, the wind power and wave power has a high possibility of future growth due to the economic feasibility in offshore environment. This kind of large-scale combined systems might be follow the determination by the transmission system operator's directions and control the output profile by focusing at PCC. However, both renewable energies are depend on the unpredictable environmental variation; it is needed to do the compensation devices. In this paper, the ESS compensation plan is proposed to do output determination of the combined generator system by paying attention to active power of utility grid with the analysis of the controllable elements of the wind and wave power generator. The improvement of the new application technique of the combined system is confirmed through using the PSCAD/EMTDC. The entire simulation process was designed by adopting the active power control according to the reference signal of TSO.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.19 no.3
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• pp.157-163
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• 2019

A small millimeter-wave tracking radar is a pulse radar that searches, detects, and tracks a target in real time through a TWS (Track While Scan) method on a sea-going traps target with a large RCS running at low speed. This paper describes the development of a simulated signal generator to verify the performance of a small millimeter wave tracking radar in laboratory anechoic chamber environment. We describe a GUI program for testing and performance analysis in conjunction with hardware configuration and tracking radar, and verified the simulated signal generator implemented through performance test.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.17 no.2
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• pp.30-37
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• 2008

An object transport system is driven by a conveyor belt system or a magnetic levitation system. It is an indispensable device in many fields and especially it is very important in the factory automation. However, the conventional transport system can damage precision optical components by the contact force and destroy the inner structure of semiconductor by the magnetic field. The new transport system for transporting without damage is required. The ultrasonic transport system is a device that transports objects on the elastic body using ultrasonic wave. In this paper, an object transport system using the ultrasonic wave is developed for transporting precision elements without damage. Traveling waves are generated by the ultrasonic wave generator fixed in both ends of the beam. The traveling wave of the ultrasonic transport system is theoretically analyzed. Transport direction of the object is examined according to phase difference and frequency. The theoretical results are verified by experiments.