• Structural Engineering and Mechanics
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• 제40권1호
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• pp.49-64
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• 2011

An analytical method is presented to investigate electromagnetothermoelastic behaviors of a hollow sphere composed of functionally graded piezoelectric material (FGPM), placed in a uniform magnetic field, subjected to electric, thermal and mechanical loads. For the case that material properties obey an identical power law in the radial direction of the FGPM hollow sphere, exact solutions for electric displacement, stresses, electric potential and perturbation of magnetic field vector in the FGPM hollow sphere are determined by using the infinitesimal theory of electromagnetothermoelasticity. Some useful discussion and numerical examples are presented to show the significant influence of material inhomogeneity. The aim of this research is to understand the effect of composition on electromagnetothermoelastic stresses and to design optimum FGPM hollow spheres.

• 한국농공학회:학술대회논문집
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• 한국농공학회 2002년도 학술발표회 발표논문집
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• pp.129-132
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• 2002

The purpose of this study was to disclose the problems of structural safety of small scale vinyl house through investigation of actural state of plastic greenhouses by region and growing crops and the objective of a field survey is to develop safety structural model of small scale vinyl house which accounts for the most part of local horticultural facility in order to reduce damage caused by strong wind and heavy snow repeatedly every year.

• 한국안전학회지
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• 제27권3호
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• pp.42-48
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• 2012

This paper is aimed to analysis of electrical fire risk by overcurrent and series arc signals in traditional market shops Firstly, the field state investigation was conducted for shops at the traditional market (30 shops). At each shop in the traditional market, load characteristics were investigated and thermal characteristics in Panel were analyzed. Thermal characteristics in Panel is an indicator that can determine the impact of overcurrent. Results of the field state investigation found out four shops which showed abnormal thermal characteristics in Panel. Electrical load characteristics of these 4 shops were simulated by experimental setup consists of generator, motor and heater. In order to verify the electrical fire risk by electrical loads of 4 shops, arc and overcurrent experiments were conducted. The waveshapes of arc and overcurrent are investigated in both the time and frequency domains to find signal characteristics. The results obtained in this paper will be very helpful for the prevention of electrical fires occurred at the shops in the traditional market.

• 교육시설 논문지
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• 제20권5호
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• pp.35-42
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• 2013

It has already been four years as of 2013 since the Departmentalized Classroom System was first introduced following the Korean government's policy. However, no investigation had been made yet on whether the system is properly being managed in practice according to the presented standards, guidelines, and policy direction. Hence, an in-depth investigation and analysis were called for. In line with this, documents were researched, deliberation meetings of experts were held, and the system pilot was tested to develop indices to investigate the state of block-scheduled classes and classes for each student's academic level for the educational classes field. For the school management field, we developed indices to investigate the teachers' organization and their division of labor, administrative officers and work reduction, improvement of teachers' expertise, and the guidance of the students' school life. Based on the indices, we investigated the state of 24 schools, which manage an advanced school system, nationwide. The results showed that the Departmentalized Classroom System has now reached the settling stage, which is beyond the introductory stage, and that it needs to be systematically supplemented for it to be settled in a stable manner.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 하계학술대회 논문집 A
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• pp.555-557
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• 2003

As electric power transmission systems grow to supply the increasing electric power demand, transmission capacity is larger. but that's really difficult to secure the location for power transmission and distribution to user. The high temperature superconducting(HTS) cable is a method to solve this problem. But for applying to real systems, it needs to investigate the effect of HTS cable. The most important things is the investigation of fault condition. the fault on HTS cable include the quench state. When a fault occur in a circuit, three critical parameters(temperature, current density, magnetic field) exist. when one of these parameters exceeds the critical value, the superconducting becomes normal-conducting. f the cooling power is insufficient to recover the superconducting state, the normal-conducting zone expands. In order to solve these problem, this paper present simulate the quench state considering the over-current and over-voltage in the informal circuit and analyze the quench state.

• International Journal of Fluid Machinery and Systems
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• 제4권1호
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• pp.209-216
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• 2011

The flow upstream of a centrifugal pump impeller has been investigated by both experimental test and numerical simulation. For experimental study, the flow field at four sections in the pump suction is measured by using PIV method. For calculation, the three dimensional turbulent flow for the full flow passage of the pump is simulated based on RANS equations combined with RNG k-$\varepsilon$ turbulence model. From those results, it is noted that at both design lo ad and quarter load condition, the pre-swirl flow whose direction is the same as the impeller rotation exists at all four sections in suction pipe of the pump, and at each section, the pre-swirl velocity becomes obviously larger at higher rotational speed. It is also indicated that at quarter load condition, the low pressure region at suction surface of the vane is large because of the unfavorable flow upstream of the pump impeller.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 춘계학술대회 논문집 초전도 자성체 연구회
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• pp.13-16
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• 2003

Magnetic and magneto-optical properties of Fe/Pt/Fe, Co/Pd/Co trilayers and also the sandwiches with wedge-shaped magnetic (Fe, Co) and nonmagnetic (Pt, Pd) layers were investigated. The oscillatory behavior of the saturation field $H_{s}$ of the studied trilayers with changing the thickness of the nonmagnetic layer (NML) $t_{NML}$ was revealed. That was explained by the exchange coupling between ferromagnetic layers (FML) through the nonmagnetic spacer. For the first time, oscillations of the transverse Kerr effect (TKE) with changing the Pt- and Pd-wedge thickness were discovered. Period of these oscillations was found to depend on the FML thickness and the photon energy of the incident light. TKE spectra of the examined samples were discovered to modify very strongly with increasing $t_{NML}$. The discovered peculiarities of magneto-optical properties of thin-film systems were explained by a concept of the spin-polarized quantum well states in the pt and Pd layers.

• 한국안전학회지
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• 제27권6호
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• pp.54-58
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• 2012

This paper is purposed to analyze electric leakage component which can prevent electrical fires on breaker capacity expansion and power failure by operation of ELB(Earth leakage breaker) for stable sizes. In order to analysis for electric leakage component for stable sizes, this paper studied field state investigation which are at stable companies( 10 companies) in cheong-won location to deduce the problems of electric leakage component is analyzed. The field state experiment method is measured with electric leakage component which load part of ELB detected by electric loads(electrical fan, lighting, auto waterer, feeder and halogen lighting) and stable sizes. Results show that electric leakage component suggested in this paper are valuable and usable to electrical fire in leakage current based on environment factor, which will prevent severe damage to human beings and properties and reduce the electrical fires in stable.

• 농촌계획
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• 제20권2호
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• pp.127-137
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• 2014

Self-sufficiency rate of food in South Korea is almost at the lowest level among OECD countries, and the decrease tend of farmland is expected to be continued. In this situation, the government has been revised the target self-sufficiency rate of food, and carried forward various policies in order to achieve it. One of those policies is the restoration business of idle farmland which is planned to carry forward after 2015. This study set up indicators evaluating effective use of idle farmland, and tried to apply in the field before carrying forward restoration business. The result of this study may be summarized as follows. First of all, it reset an evaluation indicator that was based on the evaluation indicator developed in order to set application directions of idle farmland. Next, it selected 30 idle farmlands with reset evaluation indicator among 11,635 which were inspected nationwide in 2012. Before applying indicator, it measured the condition of recycling such as accessibility of farmland, condition of irrigation and drainage system, land state, and surroundings by field investigation. Then, it calculated composite score in each target area through applying indicators, and verified the indicator by comparing calculated result with the one which was decided from field investigation. Finally, it carried out field investigation, correct and upgrade some problems of the standard of score calculation that was found during applying previously set evaluation indicator to target area, and established the final standard of calculation for evaluation indicator.

• International Journal of Naval Architecture and Ocean Engineering
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• 제11권2호
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• pp.923-938
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• 2019

Surge motion of top-end platform induced by periodic wave makes marine flexible riser encounter equivalent sheared-oscillatory flow, under which the Vortex-induced Vibration (VIV) response will be more complicated than pure sheared flow or oscillatory flow cases. Based on a time domain force-decomposition model, the VIV response characteristics under sheared-oscillatory flows are investigated numerically in this paper. Firstly, the adopted numerical model is validated well against laboratory experiments under sheared flow and oscillatory flow. Then, 20 sheared-oscillatory flow cases with different oscillation periods and top maximum current velocities are designed and simulated. Under long and short oscillation period cases, the structural response presents several similar features owing to the instantaneous sheared flow profile at each moment, but it also has some different patterns because of the differently varying flow field. Finally, the effects and essential mechanism of oscillation period and top maximum current velocity on VIV response are discussed systematically.