• Journal of the Korean Society of Safety
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• v.30 no.3
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• pp.13-19
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• 2015

Railway vehicle equipment goes back again to the state just before when failure by the repair. In repairable system, we are interested in the failure interval. As such, a statistical model of the point process, NHPP power law is often used for the reliability analysis of a repairable system. In order to derive a quantitative reliability value of repairable system, we analyze the failure data of the air brake system of the train line 7. The quantitative value is the failure intensity function that was modified, converted into a cost-rate function. Finally we studied the optimal number and optimal interval in which the costs to a minimum consumption point as cost-rate function. The minimum cost point was 194,613 (won/day) during the total life cycle of the braking system, then the optimal interval were 2,251days and the number of optimal preventive maintenance were 7 times. Additionally, we were compared to the cost of a currently fixed interval(4Y) and the optimum interval then the optimal interval is 3,853(won/day) consuming smaller. In addition, judging from the total life, "fixed interval" is smaller than 1,157 days as "optimal interval".

• Journal of Applied Reliability
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• v.16 no.3
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• pp.224-230
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• 2016

Purpose: Military maintenance involves corrective and preventive actions carried out to keep a system in or restore it to a predetermined condition. This research develops an optimal maintenance cycle for aviation oil testing equipment with acceptable reliability level and minimum maintenance cost. Methods: The optimal maintenance policy in this research aims to satisfy the desired reliability level at the lowest cost. We assume that the failure process of equipment follows the power law non-homogeneous Poisson process model and the maintenance system is a minimal repair policy. Estimation and other statistical procedures (trend test and goodness of fit test) are given for this model. Results: With time varying failure rate, we developed reliability-based maintenance cost optimization model. This model will reduce the ownership cost through adopting a proactive reliability focused maintenance system. Conclusion: Based on the analysis, it is recommended to increase the current maintenance cycle by three times which is 0.5 year to 1.5 years. Because of the system's built-in self-checking features, it is not expected to have any problems of preventative maintenance cycle.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.15 no.6
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• pp.485-493
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• 1990

Timing recovery for recently proposed nonlinear minimum-bandwidth systems is of concern since most conventional methods fail for these systems. As a method to surmount this retiming difficulty, this paper proposes the fourth-power-law method. The feasibility of the proposed method for minimum-bandwidth systems is shown through a rigorous analysis. Furthermore, extensive computer simulations are used to determine the best configurational strategy for various filters around the fourth-power nonlinear process. It is found that no intermediate filtering is necessary in general and even the pre-filtering can be omitted for systems having symmetric power spectral densities.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.762-767
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• 2007

As a macromolecule material, melted rubber flow shows characteristics of shear thinning fluid. The dynamic viscosity of this rubber fluid is influenced by temperature and shear strain rate. In this study, the numerical simulation of rubber extrusion forming process has been performed using commercial CFD code, Polyflow. Power-law model considering the effect of shear rate is used for the computer simulation of this non-Newyonian flow. Also Non-isothermal behavior is considered as Arrhenius-law model. Distributions of velocity and temperature are predicted through the simulation.

• Convergence Security Journal
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• v.11 no.5
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• pp.41-51
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• 2011

The objective of this study is to generally check the present situation of private security industry by analyzing the current situation of private security industry in Korea so as to find which policy base is reflected to amend law by analyzing the amendment process of private security law in order to suggest policy direction of private security industry in Korea. Viewing through amendment process of private security law, enhancing publicity and enterprise are not judged to form any definite policy base. They are merely interpreted to partially reflect enterprise under the strong base of publicity. Such policy base may cause overall stagnation of private security industry. For sound development of private security industry, it is required to get out of the existing policy direction so as to change policy base to the direction of enhancing enterprise of private security industry. The power of police for instruction and supervision should be largely transferred to Korea Security Association so as to cultivate autonomous purifying function of private security industry. Police should strive to develop policy in the level of joint production of security service.

• Journal of Electrical Engineering and Technology
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• v.9 no.5
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• pp.1686-1693
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• 2014

In this paper, oil-paper samples composed of transformer windings were used to investigate the insulation degradation process subjected to partial discharge (PD), with artificial defects inside to simulate the PD induced insulation degradation. To determine appropriate test voltages, the breakdown time obtained through a group of accelerated electrical degradation tests under high voltages was firstly fitted by two-parameter Weibull model to acquire the average breakdown time, which was then applied to establish the inverse power law life model to choose advisable test voltages. During the electrical degradation process, PD signals were synchronously detected by an ultra-high frequency (UHF) sensor from inception to breakdown. For PD analysis, the whole degradation process was divided into ten stages, and chaos theory was introduced to analyze the variation of three chaotic parameters with the development of electrical degradation, namely the largest Lyapunov exponent, correlation dimension and Komogorov entropy of PD amplitude time series. It is shown that deterministic chaos of PD is confirmed during the oil-paper degradation process, and the obtained results provide a new effective tool for the diagnosis of degradation of oil-paper insulation subjected to PD.

• Journal of Korea Water Resources Association
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• v.32 no.1
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• pp.31-40
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• 1999

After investigating the basic problems of seepage flow, the friction factor equation of power form was developed for solving them. The use of power law for the estimation on friction factor enabled to develop the explicit form of equations without any iteration process being related to various non-dimensional physical numbers. For the derivation of friction factor equations, the existing data were re-analyzed, and the simple method of seepage flow design was devised with the power law equations for the estimation of slope, discharge, and diameter.

• The Korean Journal of Rheology
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• v.11 no.2
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• pp.159-167
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• 1999

Sandwich injection molding is one of the remarkable polymer processes recently developed from conventional injection molding. But it is almost impossible to do theoretical investigation that we've researched it through numerical simulation. In this paper, numerical simulation on the study of sandwich injection molding is based on Finite Element Method and FAN/Control Volume method. In addition to conventional filling parameter that can confirm skin polymer melt front, new filling parameters have been introduced to confirm core polymer melt front advancement. These filling parameters are defined in each layer which is divided to solve temperature field along the thickness direction. One can notice different filling patterns resulted from the variation of material properties such as viscosities and power-law indexes, and processing conditions such as switch-over times and wall temperatures. It gives us a better understanding of the sandwich injection molding process. And we can recognize that it's the core polymer spatial distribution after the completion of filling that is the most important key point to use this process for industrial molding process.

• Journal of Arbitration Studies
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• v.12 no.2
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• pp.153-184
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• 2003

‘Schiedsgutachten’ is more of a law phenomenon that appears frequently in privity of contract rather than a concept that is .generally established in the positive law. There is no definition of this in the positive law which makes it difficult to put a finger on the concept but when the concerned party of the conflict puts the establishment of a fact that is a premise to the legal relationship or the right about the legal right's content or the supplementation of the legal relationship to a third party and makes an agreement to follow the third party's judgement, the process is called the contract of schiedsgutachten. At this point, the judgement of the third party is called the schiedsgutachten. This thesis strives to search for an activation of the schiedsgutachten system in Korea by analyzing and researching the systems in various European countries including Germany where the above mentioned schiedsgutachten system is relatively well-developed. First of all, the three types of schiedsgutachten in the German law will be looked into. Based on this, the theories and judicial precedents of Swiss law, French law, Italian law, and British law will be looked into as well. By doing this, similarities and distinction standards between the various countries' legal systems will be further analyzed. Along with this, the legal qualities and the binding power of the schiedsgutachten will be searched out. In Korea, the term schiedsgutachten itself is not customary as the system itself is not actively being carried out. However, in car damage compensation lawsuits which occupy a big percentage, if the schiedsgutachten system were to be used, the problem would be easily solved without progressing to lawsuits. Korea should actively seek out this system with the various models of different countries including Germany which has been introduced in this thesis as a model.

• Journal of Arbitration Studies
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• v.25 no.2
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• pp.97-118
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• 2015

As China has quickly emerged as a global economic power, the total number of international commercial disputes arbitrated by Chinese arbitral institutions has increased dramatically. Along with this, the annulment procedure of arbitral awards in China have been newly brought to the fore. In accordance with the historical background and the demand of the times, the Chinese annulment procedure of arbitral awards reveals distinctive Chinese features. Although it was enacted in the face ofof an unwarranted prejudice against the dispute settlement system by arbitration as well as a deep mistrust of domestic arbitral institutions, the annulment procedure of arbitral awards showed a certain degree of justification and rationality in its initial stages of legislation. However, it is also the case that it has not adapted well to new domestic or foreign arbitration circumstances in the last twenty years. At present, there is a keen interest in revisions to and debates on arbitration law of China. It is necessary to take an active part in the amendment discussion and process of arbitration law. Moreover, we need to reform the annulment procedure of arbitral awards in order to meet the global trend of arbitration law.