• Tribology and Lubricants
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• 제14권1호
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• pp.85-93
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• 1998

The Bair & Winer's limiting shear stress rheological model is incorporated into the Reynolds equation to successfully predict the traction and film thickness for an isothermal line contact using the primary rheological properties. The modified WLF viscosity model and Barus viscosity model are also adapted for the realistic prediction of EHD tractional behavior. The influences of the limiting shear stress and slide-roll ratio on the pressure spike, film thickness, distribution of shear stress and nonlinear variation of traction are examined. A good agreement between the disc machine experiments and numerical traction prediction has been established. The film thickness due to non-Newtonian effects does not deviate significantly from the fdm thicknesss with Newtonian lubricant.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1993년도 하계학술대회 논문집 B
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• pp.773-776
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• 1993

The thyristor turn-off model plays an important part in the design of thyristor snubber circuit. However, it is difficult to determine the thyristor turn-off characteristics. In this paper two methods to establish the simple thyristor turn-off model are proposed based on the reverse recovery characteristics given in the data sheets. Using the simple thyristor turn-off model, the optimum thyristor snubber circuit design procedures are presented considering maximum voltage spike, maximum reverse dv/dt, and turn-off loss.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1993년도 하계학술대회 논문집 B
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• pp.781-783
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• 1993

The GTO model is based on the Ebers-Moll equation extened to include the three-junction devices and a detailed description of the implementation of the model equation as well as defferent tests are discussed. Problems to be considered for the snubber design, such as voltage spike reduction, maximum GTO anode current, and switching power, were discussed using the calculation model. The macro model is very useful for simulation of GTO circuit and high power circuit switch in high frequency and complex structure.

• 수산경영론집
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• 제49권3호
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• pp.85-99
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• 2018

This study is to compare and evaluate the estimating method of WTP(willingness to pay) for the valuation of oceans and fisheries resources with non-market goods characteristics using contingent valuation method. In general, when estimating parameters of the WTP function, we should take into account the assumption of probability distribution, inclusion of covariates, method of inducement of payment, and the treatment of 0 payment intention and resistance responses. This study utilizes survey data that was used to estimate the value of fisheries resource protection zones, with a total of 1,200 samples. The main results of this study are summarized as follows: First, the final willness to pay amount is estimated at a statistical significance of less than 1 percent, and the distribution of the final willness to pay amount is from \6,926 of the double bounded dichotomous model to \10,721 of the spike model. Second, the willness to pay amount based on assumptions about the normal and logistic probability distributions are estimated to be \9,429 and \9,370 respectively, so there was no significant difference. Third, the willness to pay amount of the single bounded dichotomous model and the double bounded dichotomous model are estimated to be \8,951 and \6,926 respectively, making a relatively large difference. Fourth, the willness to pay amount of the model without covariates and the model with covariates are estimated to be \9,429 and \8,951, respectively, so the willness to pay amount is underestimated when the covariates are included. Fifth, the Spike model that considers zero payment intention and resistance response estimates \10,405 as the highest payment in this study. Finally, the CVM analysis guidelines proposed by the Korea Development Institute (KDI) are estimated to be \9,749 and \10,405 respectively, depending on including no covariates and with covariates. Compared to other models, the final willness to pay amount is not estimated underestimated. Therefore this study suggests the use of KDI's guidance under government public policy projects. In view of these results, the estimating model for willness to pay amount model will be selected by considering the sample size, the suitability of the model, the sign of the estimated coefficient, the statistical significance, the ratio of the zero payment intention and the payment rejection. And, for CVMs on government public policy projects, it is desirable to estimate by the method proposed by the KDI.

• The Korean Journal of Physiology and Pharmacology
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• 제15권6호
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• pp.415-422
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• 2011

Previously, we reported that besides retinal ganglion cell (RGC) spike, there is ~10 Hz oscillatory rhythmic activity in local field potential (LFP) in retinal degeneration model, rd1 mice. The more recently identified rd10 mice have a later onset and slower rate of photoreceptor degeneration than the rd1 mice, providing more therapeutic potential. In this study, before adapting rd10 mice as a new animal model for our electrical stimulation study, we investigated electrical characteristics of rd10 mice. From the raw waveform of recording using $8{\times}8$ microelectrode array (MEA) from in vitro-whole mount retina, RGC spikes and LFP were isolated by using different filter setting. Fourier transform was performed for detection of frequency of bursting RGC spikes and oscillatory field potential (OFP). In rd1 mice, ~10 Hz rhythmic burst of spontaneous RGC spikes is always phase-locked with the OFP and this phase-locking property is preserved regardless of postnatal ages. However, in rd10 mice, there is a strong phase-locking tendency between the spectral peak of bursting RGC spikes (~5 Hz) and the first peak of OFP (~5 Hz) across different age groups. But this phase-locking property is not robust as in rd1 retina, but maintains for a few seconds. Since rd1 and rd10 retina show phase-locking property at different frequency (~10 Hz vs. ~5 Hz), we expect different response patterns to electrical stimulus between rd1 and rd10 retina. Therefore, to extract optimal stimulation parameters in rd10 retina, first we might define selection criteria for responding rd10 ganglion cells to electrical stimulus.

• 한국수자원학회논문집
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• 제46권10호
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• pp.989-995
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• 2013

본 연구는 상관 다기능 저류지의 조성을 가상적으로 설정하여 환경개선용수 공급편익을 추정하고자 한다. 이를 위해 국민들의 지불의사액(WTP, willingness to pay)을 유도할 수 있는 설문조사기법인 조건부 가치측정법을 적용한다. 조사결과 많은 응답자들은 영의 WTP를 밝혔다. 이러한 영의 WTP를 다루기 위해 본 연구에서는 스파이크 모형을 적용한다. 분석결과 환경개선용수 공급편익은 사업지에 대해 가구당 연간 1,393.7원, 비사업지에 대해 가구당 연간 2,237.7원으로 추정되었다. 이 값을 전국으로 확장하면 연간 383.6억원에 달한다. 이러한 분석결과는 환경개선용수의 공급편익과 관련된 투자의 적정수준 결정 및 관리정책 결정에 있어서 유용하게 활용될 수 있을 것이다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집A
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• pp.760-765
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• 2000

The study deals with the development of a computational procedure for evaluating the temperature rise in dry and lubricated multi-layered contacts of head/disk interface. A transient computational model with a transformed rectangular computational domain is utilized. A model and a computational method for micro-contact with sub-lubricated zone, including friction heat generation, have been presented. The model was applied, taking full account of the changes in contact area and contact load due to frictional heating. The computational distribution of temperature is obtained with the analytical findings for various composition and contact conditions. Especially, a rapid rise ($220^{\circ}C$ or above) in read head temperature lese to a saturation in the influence of a thermal spike on signal performance. This general class of problems can be treated provided that heat generation distribution and layer properties are known.

• 호남수학학술지
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• 제44권3호
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• pp.402-418
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• 2022

Noise is a fundamental factor to increased validity and regularity of spike propagation and neuronal firing in the nervous system. In this paper, we examine the stochastic version of the Izhikevich-FitzHugh neuron dynamical model. This approach is based on techniques presented by Luo and Guo, which provide a general framework for the bifurcation and stability analysis of two dimensional stochastic dynamical system as an Itô averaging diffusion system. By using largest lyapunov exponent, local and global stability of the stochastic system at the equilibrium point are investigated. We focus on the two kinds of stochastic bifurcations: the P-bifurcation and the D-bifurcations. By use of polar coordinate, Taylor expansion and stochastic averaging method, it is shown that there exists choices of diffusion and drift parameters such that these bifurcations occurs. Finally, numerical simulations in various viewpoints, including phase portrait, evolution in time and probability density, are presented to show the effects of the diffusion and drift coefficients that illustrate our theoretical results.

• 자원ㆍ환경경제연구
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• 제12권3호
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• pp.453-467
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• 2003

CVM 연구에서 설문자료로부터 WTP 분포를 근사화하는 작업은 표본내에 포함된 0의 응답 때문에 문제가 발생할 수 있다. 이 때 WTP의 이중적 분포를 무시하면, 즉 연속적인 분포를 가정하면 후생치 도출에 있어 왜곡이 있을 수 있다. 본 연구는 이런 문제를 해결하기 위해 혼합모형을 제안하고 적용한다. 혼합모형은 영에서 점질량으로 이루어진 분포와 양의 연속적 분포를 혼합하는 특징을 갖고 있다. 이 경우 지불의사가 전혀 없는 확률은 모수 ${\rho}$로 표현되고, 별도로 식별가능하며, 최우추정법을 이용하면 일치추정량을 얻을 수 있다. 본 연구에서는 한려해상국립공원을 대상으로 혼합모형의 적합성에 관한 실증연구를 수행하였는데 그 결과 혼합모형의 적용이 바람직한 것으로 나타났다.

• 터널과지하공간
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• 제5권1호
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• pp.70-76
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• 1995

Two types of deformations can occur on the cable during the monitoring of the rock displacement by the time domain reflectometry. One is the impedance model for tensile deformation, and the other is the capacitance model for the shear deformation. The former gives a response signal with a gradual change in the amplitude of the reflected voltage, meanwhile the latter produces a signal with a blunted spike. The resolution of the TDR can be improved to 0.125% using calibration crimps on the cable of 60 meters long. It is recommended that the diameter of the cable should be 18 mm at least in order to induce a better reflected pulse without any open-circuit. The actual TDR technique cannot characterize the type and the magnitude of rock displacement quantitatively. Systematic investigation of the TDR parameters, such as the exact of cable diameter, cable length, number of crimps, combination of shearing and extension, and environment of the TDR equipment, will be able to improve the resolution to 0.01 mm.