• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.4 s.121
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• pp.317-323
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• 2007

Non-contact underwater explosions against surface ships could cause extensive equipment damage and render the ship inoperative. As an analytical method, DDAM(dynamic design and analysis method) is used for ship shock design. In this paper, in order to verify the finite element model of large shipboard equipment, modal test of equipment was performed. Major objective of this paper is to describe shock analysis methodology for large shipboard equipment attacked to the top and bottom foundations.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.4
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• pp.645-650
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• 2007

This paper proposes a parameter estimation technique of a power transformer. Based on the combined equation, it estimates separately the primary and secondary leakage inductances using the least square method from the instantaneous voltages and currents in the steady state. The performance of the proposed technique was investigated by varying the cut-off frequency of the filter and the number of samples per cycle. The estimated values are obtained based on the average value for 41 cycle.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2000.11b
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• pp.75-80
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• 2000

본 논문은 영상복원을 역확산 과정으로 해석하여 복원된 영상을 역확산 방정식의 해로 구하는 알고리즘을 제안한다. 역확산 과정은 물리적으로 불량위치(ill-posed)과정이기 때문에, 이를 정규화 해주어야 하는데 이를 위해서 역확산 과정을 고유함수(eigenfunction)들의 전개로 나타낸 후에 고유함수들의 계수들을 조작하였다. 본 논문에서는 계수들을 조작할 때 영상이 가지고 있는 주파수 특성을 고려하여 한계주파수(cut-off frequency)를 넘은 경우에 계수들을 시간과 주파수의 감소함수로 나타내어 불량위치문제를 해결하였다. 계수를 주파수에 대한 감소함수로 나타낸 것은 영상에 저주파 성분이 많고, 고주파 성분이 영상의 형성에 끼치는 영향이 상대적으로 적다는 영상의 특성을 고려한 것이다. 이러한 감소함수를 사용하였을 때 불량위치 문제를 해결할 수 있다는 것을 증명하였고, 실험적으로 양질의 영상을 산출함을 보였다.

• Proceedings of the KIPE Conference
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• 2004.07b
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• pp.822-825
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• 2004

This paper describes the improvement of performance of power supply for ship's emergency lighting system(SELS). Proposed system is composed of power factor correction (PFC) circuit, emergency power supply system (EPSS), half bridge(HB) inverter, fluorescent lamp(FL) starting circuit and microprocessor control system. Experimental works using proposed system confirm that speedy and stable power to be supplied when main power source cut-off, compared with conventional relay type, and control power factor up to $97.5[\%]$ and input power up to $35.0[\%]$ by adjusting of pulse frequency of the HB inverter.

• Journal of Power Electronics
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• v.9 no.3
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• pp.418-429
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• 2009

In this paper an optimal damped input filter is designed based on a Genetic Algorithm (GA) for an electrolytic capacitor-less AC-AC converter. Sufficient passive damping and minimum losses in passive damping elements, minimization of the filter output impedance at the filter cut-off frequency, minimization of the DC-link voltage and input current fluctuations, and minimization of the filter costs are the main objectives in the multi-objective optimization of the input filter. The proposed filter has been validated experimentally using an induction motor drive system employing an electrolytic capacitor-less AC-AC converter.

• Journal of the Korean Vacuum Society
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• v.8 no.4B
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• pp.536-540
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• 1999

We have developed a refractory WNx self-aligned gate GaAs metal-semiconductor field-effect transistor(MESFET) using $SiO_2$ side-wall process. The MESFET hasa fully ion-implanted, planar, symmetric self-alignment structure, and it is quite suitable for integration. The uniform trans-conductance of 354nS/mm up to Vgs=+0.6V and the saturation current of 171mA/mm were obtained. As high as 43GHz of cut-off frequency hs been realized without any de-embedding of parasitic effects. The refractory WNx self-aligned gate GaAs MESFET technology is one of the most promising candidates for realizing linear power amplifier ICs and multifunction monolithic ICs for use in the digital mobile communication systems such as hand-held phone(HHP), personal communication system (PCS) and wireless local loop(WLL).

• Proceedings of the IEEK Conference
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• 1998.06a
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• pp.405-408
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• 1998

Due to the large conduction band discontinuity between emitter base, OmGaAs HBT has an advantge to enable the hot electrons to inject into the base. In this paper, InAlGaAs/InGaAs HBT with the various emitter junction gradings and the modified collectors are simulated and analyzed by HMC(hybrid monte carlo) simulator in order to find a optimal structure for the shortest transit time. A minium base transit time (.tau.$_{b}$ ) of 0.21 ps was obtained for HBT with the grading layer, which is parabolically graded from x=1.0 to x=0.5. The minimum collector transit time (.tau.$_{c}$ ) of 0.31ps was found when the collector was modified by inserting p$^{[-10]}$ and p$^{+}$ layers. Thus HBT in combination with the emitter grading and the modified collector layer showed the cut-off frequency (f$_{T}$) of 183GHz.z.z.

• Proceedings of the KIEE Conference
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• 2001.11c
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• pp.176-179
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• 2001

A portable bio-signal measurement system for 24-hours continuous health monitoring of the elderly and the disabled is presented. The measurement system has the functions of acquisition of various bio-signals such as ECG, EMG and EEG, wireless data transmission/receive and adjustment of parameters such as gain and cut-off frequency. The data is sent to a host computer or other device via a Bluetooth. The design targets of the developing system for volume and power consumption are $20{\times}30{\times}5(mm^3)$ and 8mW.

• Proceedings of the KIEE Conference
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• 2001.05a
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• pp.34-37
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• 2001

This paper presents some results after comparing the characteristics of 3 algorithms, which are discrete Fourier transform based algorithm, least square method, and modified differential approximation algorithm, used at most distance relays all over the world. In case of the DFT based distance relaying algorithm, the length of the algorithm data window and the cut-off frequency of an anti-aliasing low-pass filter adopted are fixed. On the other hand, the data window lengths are changed according to the corresponding low-pass filters in the rest two algorithms. In series of tests, the apparent impedance estimated by the modified differential approximation algorithm shows faster and more stable characteristics of convergence than the two others.

• The KSFM Journal of Fluid Machinery
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• v.13 no.2
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• pp.18-23
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• 2010

This paper presents a procedure for the aerodynamic and aeroacoustic characteristics of a sirocco fan. For the aerodynamic and aeroacoustic analyses of the sirocco fan, three-dimensional steady and unsteady Reynolds-averaged Navier-Stokes equations are solved with a shear stress transport turbulence model for turbulence closure. The flow analyses were performed on a hexahedral grid using a finite-volume solver. The validation of the numerical results is performed by comparing with experimental data for the pressure, efficiency and power. The internal flow analyses of the sirocco fan are performed to understand the unstable flow phenomenon on the casing for the wall pressure and internal flow characteristics at each position. It was found that fluctuation of pressure and locally concentrated noise source are observed near the cut-off and expansion regions of the casing.