• Structural Monitoring and Maintenance
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• v.6 no.3
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• pp.219-235
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• 2019

Scheduled inspections of common crossings are one of the main cost drivers of railway maintenance. Prognostics and health management (PHM) approach and modern monitoring means offer many possibilities in the optimization of inspections and maintenance. The present paper deals with data driven prognosis of the common crossing remaining useful life (RUL) that is based on an inertial monitoring system. The problem of scheduled inspections system for common crossings is outlined and analysed. The proposed analysis of inertial signals with the maximal overlap discrete wavelet packet transform (MODWPT) and Shannon entropy (SE) estimates enable to extract the spectral features. The relevant features for the acceleration components are selected with application of Lasso (Least absolute shrinkage and selection operator) regularization. The features are fused with time domain information about the longitudinal position of wheels impact and train velocities by multivariate regression. The fused structural health (SH) indicator has a significant correlation to the lifetime of crossing. The RUL prognosis is performed on the linear degradation stochastic model with recursive Bayesian update. Prognosis testing metrics show the promising results for common crossing inspection scheduling improvement.

• Journal of Environmental Science International
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• v.11 no.9
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• pp.907-914
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• 2002

Various Eulerian-Lagrangian models for the one-dimensional longitudinal dispersion equation in nonuniform flow were studied comparatively. In the models studied, the transport equation was decoupled into two component parts by the operator-splitting approach; one part is governing advection and the other is governing dispersion. The advection equation has been solved by using the method of characteristics following fluid particles along the characteristic line and the results were interpolated onto an Eulerian grid on which the dispersion equation was solved by Crank-Nicholson type finite difference method. In the solution of the advection equation, Lagrange fifth, cubic spline, Hermite third and fifth interpolating polynomials were tested by numerical experiment and theoretical error analysis. Among these, Hermite interpolating polynomials are generally superior to Lagrange and cubic spline interpolating polynomials in reducing both dissipation and dispersion errors.

• Journal of Navigation and Port Research
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• v.34 no.9
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• pp.693-698
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• 2010

In port and its approach channel, traffic accidents such as collision, aground, minor collision have reached about 77% of total marine casualty in the area. In this paper, an attempt to enhance the safe navigation was proposed by offering marine traffic supporting system which helps VTS operator assist vessel effectively with the quantitative assessment on difficulty of each vessel. The system collects navigation data from onboard AIS, assesses the data in assessment mode to analyze the navigation difficulties of each vessel and displays the degree of danger of each vessel on the ECDIS in real-time to decide the intervention time or order of priority for VTS operator. The effectiveness of the system was verified by the VTS operators in Korea.

• Proceedings of the Korea Technology Innovation Society Conference
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• 2000.11a
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• pp.69-87
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• 2000

Models and Strategies for Network Operator's B2B Ecommerce The B2B ecommerce market is one of the fastest growing areas in the telecom industry. However network operators have been slow to enter the arena, Network operator have been held back by their general unsurety about the Internet business. Network operators'core business(the supply of connectivity and transport service) is becoming unprofitable. As a result they are looking to diversify into areas where margins are higher. B2B ecommerce offers them a major way to achieve this. It is possible to identify various business models for offering ecommerce services to end user, ranging from the provision of complete packaged applications to the implementation and management of customized ecommerce solution. In this study the three main approaches available to network operators are the traditional IT outsourcing model, the ASP model and the community builder model.

• Journal of the Korean Home Economics Association
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• v.35 no.3
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• pp.287-305
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• 1997

The purpose of this study was to analyze a causal effect on the housewife's leisure activity participation, leisure expenditure and leisure life satisfaction. Data was collected 249 housewives in Pusan. Data were analysed using descriptive statistics, one-way Anova, multiple regression, Pearson's correlation and path analysis. The main findings of the research were as follows: First, there were significant differences in leisure activity participation according to socio-demographic and economic variables. Physical type showed significant differences when housewife was 30's and unemployed, size of family was 3 and 4, age of the lastborn child was under 6, occupation of husband was professionals and technicians, educational attainment of housewife was under highschool graduate, pattern of housing was collective, income was higher. There were significant differences that occupation of husband was professionals and technicians, educational attainment of housewife was over junior college graduate, pattern of housing was collective, income was higher in self-developing type. restful type showed significant differences when housewife was 40's, age of the lastborn child was under 13-18, educational attainment of housewife was under highschool graduate. There were significant differences that housewife was unemployed in home-oriented type. There were significant differences that housewife was 30's and unemployed, size of family was 4, age of the lastborn child was under 6, occupation of husband was market and sales worker, educational attainment of housewife was over junior college graduate, pattern of housing was collective in time-spending type. Second, there were significant differences in leisure time, leisure expenditure and leisure life satisfaction according to socio-demographic and economic variables. Leisure time showed significant differences when housewife was unemployed, age of the lastborn child was under 13-18, occupation of husband was service, educational attainment of housewife was under highschool graduate, income was higher. Leisure expenditure showed significant differences when housewife was 30's, size of family was under 3, age of the lastborn child was under 6, occupation of husband was senior officials and manager, educational attainment of housewife was over junior college graduate, pattern of housing was collective, income was over 5,000,000 won. There were significant differences that housewife was unemployed in leisure life satisfaction. Third, casual effect was path analysed according to path model. Employment and unemployment of housewife, income and occupation of husband (product & transport equipment operator) had an effect on phycial type. Age of housewife, employment and unemployment of housewife and occupation of husband (product & transport equipment operator) had an effect on children-concerned type. Age of housewife had an effect on social-concerned type. Education of husband, income, age of lastborn child and occupation of husband (professor and teacher) had an effect on self-developing type. Age of lastborn child, employment and unemployment of housewife and occupation of husband(product & transport equipment operator) had an effect on children-concerned type. Age of lastborn child and children number had an effect on religious-social type. Employment and unemployment of housewife had an effect on home-oriented type. Age of housewife, education of husband had an effect on time-spending type. Restful type, employment and unemployment of housewife, and occupation of husband(service) have an effect on leisure time. Income, leisure time, self-developing type, children concerned type and occupation of husband(senior officials and manager) had an effect on leisure expenditure. Leisure expenditure, self-developing type, employment and nemploymentof housewife, income had an effect on leisure life satisfaction.

• Journal of Korean Society of Transportation
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• v.25 no.1 s.94
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• pp.37-47
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• 2007

The Integrated Public Transport Reforms of the Seoul Metropolitan Government, which were implemented on the $1^{st}$ of July. 2004, launched a new fare allocation method. However, when a Private transit operator or a new transport system is introduced into the existing system, it will cause an allocation problem. Therefore, this study aims to Propose a rational fare allocation method which can be applicable regardless of the number of Public transportation modes or operators. To create alternatives, this study has adopted a fundamental principle of revenue allocation methods for the transit or communications sectors, and has applied it to the current transit system of Seoul. This study kas analyzed results of the cost recovery ratios and characteristics of each alternative through case studies. This study kas Presented an assessment criterion Z in order to select an optimal alternative. The criterion consists of the sum of the cost recovery ratio of each operator and the difference of the cost recovery ratio for each agency in inter-agency transit. Using the assessment criterion. the results showed that Alternative 1 is superior to the others : Alternative 1 is considering passenger-km of each operator and unit cost of passenger-km for each operator.

• Journal of Navigation and Port Research
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• v.35 no.6
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• pp.523-531
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• 2011

The recent increase in international car-ferry lines between Korea and Japan as well as China brings needs for proper transportations of special cargo, such as machinery and luxury yacht, etc. International multimodal transport, especially international car ferry through truck-sea-truck system enables to fulfill shippers' needs for "Door to Door Service", of such special goods. However, this international multimodal transport of bulk cargo will cause a possible claim for concealed damages during such transportation. For this reason, this study aims to examine the liability system of the multimodal transport operator as well as to investigate liability for concealed damages theoretically and finally to seek proper measures for them. Futhermore, this paper intends to verify the claims for concealed damages to further the international multimodal transport by car ferries between Korea and Japan.

• Nuclear Engineering and Technology
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• v.2 no.4
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• pp.249-254
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• 1970

A time-energy transient characteristics of pulsed neutron transport problem with an inelastic kernel in the fast domain is solved exactly with a continuous energy transfer operator. A discrete time eigenvalue is found which is asymptotically dominant. The complete solution consists of three parts: a time-energy separable mode which is asymptotically dominant and a non-separable mode which is made up by two parts； a pure energy slowing-down transient and a mixture of time and energy transient which is negligible asymptotically.

• Nuclear Engineering and Technology
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• v.2 no.4
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• pp.263-268
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• 1970

The spectrum of continuous transfer operator arising in a time-energy dependent neutron transport equation is analyzed. Four theorems concerning on the spectrum are proved. A convolution theorem of the generalized Mellin energy transform is given. Also the completeness theorem necessary for a final solution is proved. A unique time decay constant 1 - c is found, which is dominant asymptotically.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.34D no.3
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• pp.93-104
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• 1997

Steady-state I-V characteristics of a resonant tunneling diode (RTD) is calculated by numerical analysis using quantum liouville equation based on wigner function which is derived from density operator. Modifications to the conventional discrete model are made to calculate more accurate quantum correlations. It is pointed out that we must include inelastic processes and the resistivity of the contacting layers to get a much more credible potential which can be theoretically obtained from the simple screening theory. The effects of spatially-varying effective mass is also checked briefly.