• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2010.05a
• /
• pp.489-490
• /
• 2010

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.5 no.2
• /
• pp.1-14
• /
• 1999

To find characteristics and areas of greater risk of oil spill at the coastal waters in Korea, some of risk factors were analyzed with historical data of oil spill and marine traffic. As a result, it is characterized that frequency of oil spill is increasing year by year and greatest percentage of spill source is fishing boat. It is proposed that the ports of Ulsan, Yeosu, Incheon and Pusan will be designated as primary area of risk as they have a higher risk of oil spills and its response authority is required to maintain appropriate regional response capability for prompt and effective response to a future spill incident. In addition, the regional response equipments at Ulsan are examined under a assumption of a medium size spill and it is found that the use of chemical dispersant can be an alternative when mechanical containment and recovery is not feasible in this area, and the existing response equipments may be appropriate to address that size of spill. However, the response authority is required to maintain more numbers of stronger boom for unsheltered waters and more quantity of concentrate dispersant to disperse all spilled oils on the water, furthermore the response authority should be prepared for a possible future catastrophic spill with sufficient equipments.

• Structural Engineering and Mechanics
• /
• v.76 no.3
• /
• pp.355-365
• /
• 2020

In this study, considering the hydroelastic response represented by the springing and whipping phenomena, we propose a method of estimating the fatigue damage in the longitudinal connections of ships. First, we screened the design sea states using a load transfer function based on the frequency domain. We then conducted a time domain fluid-structure interaction (FSI) analysis using WISH-FLEX, an in-house code based on the weakly nonlinear approach. To obtain an effective and robust analytical result of the hydroelastic response, we also conducted an experimental model test with a 1/50-scale backbone-based model of a ship, and compared the experimental results with those obtained from the FSI analysis. Then, by combining the results obtained from the hydroelastic response with those obtained from the numerical fatigue analysis, we developed a fatigue damage estimation method. Finally, to demonstrate the effectiveness of the developed method, we evaluated the fatigue strength for the longitudinal connections of the real ship and compared it with the results obtained from the model tests.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.12 no.5
• /
• pp.355-364
• /
• 2002

The goal of this research is to reduce noise level of an outdoor unit of air conditioner by changing its dynamic characteristics using SDM (structural dynamics modification) technique. At first, the emitting noise was measured and analyzed. The measurement records show the most critical frequency components which influences on the noise level. Then it was tried to move the natural frequencies outside the critical frequency region by SDM. Since it is very difficult to get a reliable FE model of air conditioner, experimentally measured frequency response functions were used to derive sensitivities that are very important to obtain design changes. The positions of modification and the thickness of modifying structures were determined to improve the dynamic characteristics of air conditioner. The recommended design guideline to move its natural frequencies outside the targeting frequency range was obtained. Then in order to prove its effectiveness, the changed design was experimentally tested and found that the SDM result is very effective to reduce not only its vibration but also its emitting noise.

• Journal of the Korean Institute of Telematics and Electronics A
• /
• v.32A no.10
• /
• pp.35-42
• /
• 1995

In this paper the driving-condition-dependent optical transmission characteristics of an STN LCD are studied. The optical transmission properties are measured for the applied voltage waveform is varied. Also, the optimum ranges of the M signal frequency and the frame frequency are investigated. An LCD is modeled by the equivalent circuit to study the effect of the parameter variation on the frequency response.

• Journal of Advanced Marine Engineering and Technology
• /
• v.16 no.5
• /
• pp.77-84
• /
• 1992

In the most of acoustic system with low flow rate and low pressure level, one-dimensional, linear modeling techniques are used very well. At low frequency, the tube is modeled as inertia element and cavity as capacitance element, and to extend the range of frequency normal mode oscillators are represented. Bond graph modelling techniques are proposed to predict TL (Transmission Loss) and time response which is impossible by transfer matrix in muffler system. A simple acoustic filter which consists of several tubes and cawities is analyzed in both time and frequency domain.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
• /
• 1993.10a
• /
• pp.71-75
• /
• 1993

The Modeling analysis and design of a high frequency LC-type series and LLCC-type parallel resonant converter oprating in the continous conduction is presented. The state-plane diagram representation of the converter response gives and good insight into the converter operation. A set of characterisric frequency are plotted which design parameters can be obtained.

• Journal of Advanced Marine Engineering and Technology
• /
• v.23 no.2
• /
• pp.210-215
• /
• 1999

The proposed detector is consists of three-phase sinusoidal signal generator and peak detector. This peak detector can detect the peak voltage value at the state of variable frequency. In experi-ment three-phase sinusoidal signals are generated from D/A converter using IBM PC and deliv-ered to the peak detector. Each signals are squared by multiplier and summed up Peak value is the square root of summed value extracted by square root circuit.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.60 no.6
• /
• pp.1128-1133
• /
• 2011

In a wind farm, a large number of small wind turbine generators (WTGs) operate whilst a small number of a large generator do in a conventional power plant. To maintain high quality and reliability of electrical energy, a wind farm should have equal performance to a thermal power plant in the transient state as well as in the steady state. The wind farm shows similar performance to the conventional power plant in the steady state due to the advanced control technologies. However, it shows quite different characteristics during fault conditions in a grid, which gives significant effects on the operation of a wind farm and the power system stability. This paper presents an analysis of response of a wind farm during grid fault conditions. During fault conditions, each WTG might produce different frequency components in the voltage. The different frequency components result in the non-fundamental frequencies in the voltage and the current of a wind farm, which is called by "beats". This phenomenon requires considerable changes of control technologies of a WTG to improve the characteristics in the transient state such as a fault ride-through requirement of a wind farm. Moreover, it may cause difficulties in protection relays of a wind farm. This paper analyzes the response of a wind farm for various fault conditions using a PSCAD/EMTDC simulator.

• Journal of Mechanical Science and Technology
• /
• v.16 no.12
• /
• pp.1627-1632
• /
• 2002

In this paper, a simplified ultrasonic CT system, which uses the information in three directions, that is, 90°, ＋45° and －45°about the inspection plane, is applied to the high strength steel, and the frequency analysis method for enhancing the C scan or CT image is developed. This frequency analysis method is based on the frequency response property of the material. By comparing the magnitudes in the frequency domain, the special frequency which shows a significant difference between the welded joint and base material was found and used to obtain a C scan or CT image. Experimental results for several kinds of specimens, having a welded joint by electron beam welding, a weld joint by arc welding, on a fatigue crack, showed that the obtained C scan or CT image has better resolution than the results of previous experiments using the maximum value of the received waveform.