• Proceedings of the KSR Conference
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• 2007.11a
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• pp.1482-1504
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• 2007

An electrical railway system uses high voltage system for train traction and low voltage system for train control. Railway systems are broadly distributed across mountains, sea sides and cities. Electrical accidents provoke the death and injury of a human being and the damage of the equipment by the overcurrent due to the catenary dropping and by the overvoltage due to lightning. Grounding systems are adopted for the protections of the system from the overcurrent and the overvoltage. Isolation grounding for each system can be easily installed. However, the closed circuits between grounding systems can be occurred. The currents flow through the closed circuits cause the abnormal operation of the system. To overcome the problem of the isolation grounding, the equipotential bonding is usually adopted. The equipotential bonding should have very small grounding resistance. In this paper, we showed the transition from the isolation grounding system to the common grounding system and presented the comparison and the analysis of two grounding systems by simulation. In addition, we proposed the direction for a new grounding system of electric railway.

• Proceedings of the KSR Conference
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• 2007.11a
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• pp.658-670
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• 2007

Most railroad accidents are due to human errors. In particular, most of the causes of these accidents are faults of an engine driver, such as lack of signal confirmation, insecure braking, driving by guess or force of habit. This paper identifies a problem(s) by analyzing accidents for the past 10 years and also seeks a solution to train good engine drivers in order to prevent railroad accidents. In summary, what is needed are: 1) proper placement of various manpower, 2) proper training of engine drivers, 3) proper legislation for a 2-man on board system, and 4) proper reformation of personnel management.

• Proceedings of the KSR Conference
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• 2007.11a
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• pp.1610-1615
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• 2007

This paper presents a characteristics of linear induction motor considering airgap variation for railway transit in order to achieve high performance of the vehicle. The operating principle of a LIM(Linear induction motor) is identical to a rotary induction motor. Space-time variant magnetic fields are generated by the primary part across the airgap and induce the electro-motive force(EMF) in the secondary part, a conducting sheet. This EMF generates the eddy currents, which interact with the airgap flux and so produce the thrust force known as Loren's force. Even though the operating principal is exactly same as a rotary motor, the linear motor has a finite length of the primary or secondary parts and it causes static and dynamic end-effect which is the discontinuous airgap flux phenomenon. This end-effect causes the deterioration of the system performance, especially in high-speed operation. Another problem is that construction tolerance restricts the minimum airgap in order to prevent a collision between the primary part and the secondary reaction plate. More over, as the airgap length is getting smaller, the attraction force between the primary part and secondary parts is getting larger dramatically and the attraction force would be another friction against propulsion. Therefore, it is necessary to figure out the characteristics of linear induction motor considering airgap variation in order to achieve high performance of the vehicle. The dynamic model of LIM taking into account end-effects is derived. Then the modified mechanical load equation considering the effect of the attraction and thrust force according to the airgap variation is analyzed. The simulation results are presented to show the effect of the LIM according to the airgap variation.

• Geophysics and Geophysical Exploration
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• v.8 no.2
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• pp.129-136
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• 2005

The damped least-squares inversion has become a most popular method in finding the solution in geophysical problems. Generally, the least-squares inversion is to minimize the object function which consists of data misfits and model constraints. Although both the data misfit and the model constraint take an important part in the least-squares inversion, most of the studies are concentrated on what kind of model constraint is imposed and how to select an optimum regularization parameter. Despite that each datum is recommended to be weighted according to its uncertainty or error in the data acquisition, the uncertainty is usually not available. Thus, the data weighting matrix is inevitably regarded as the identity matrix in the inversion. We present a new inversion scheme, in which the data weighting matrix is automatically obtained from the analysis of the data resolution matrix and its spread function. This approach, named 'extended active constraint balancing (EACB)', assigns a great weighting on the datum having a high resolution and vice versa. We demonstrate that by applying EACB to a two-dimensional resistivity tomography problem, the EACB approach helps to enhance both the resolution and the stability of the inversion process.

• Journal of the Korea Society for Simulation
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• v.23 no.4
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• pp.75-83
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• 2014

Most warship combat systems inquire human operator to control several sensor and another equipments as well as decision-modeling. For this reason, many researches with multi-agent based M&S (Modeling and Simulation) have been increasingly conducted. However there cannot find any researches of M&S based analysis for anti-submarine warfare that requires a high level of mission complexity between multiple platforms. In this research, we have been developed various combat platform models such as warship, submarine and helicopter, etc. In order to apply the multi-agent-based M&S technology to the anti-submarine warfare i.e. a HVU (High Value Unit) escort mission scenario. Then we have successfully analyzed the measures of effectiveness according to the different tactics and different situations. In future, the defence engineer maybe employ our methodology and tools to analyze actual tactical problem by simply inserting actual data into our agent model.

• Korean Journal of Optics and Photonics
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• v.28 no.2
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• pp.75-82
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• 2017

We present a new type of receiver-transmitter optical system that can be adapted to the sensor head of a displacement-measuring interferometer. The interferometer is utilized to control positioning error and repetition accuracy of a wafer, down to the order of 1 nm, in a semiconductor manufacturing process. Currently, according to the tendency of scale-up of wafers, an interferometer is demanded to measure a wider range of displacement. To solve this technical problem, we suggest a new type of receiver-transmitter optical system consisting of a GRIN lens-Collimating lens-Afocal lens system, compared to conventional receiver-transmitter using a single collimating lens. By adapting this new technological optical structure, we can improve coupling efficiency up to about 100 times that of a single conventional collimating lens.

• PNF and Movement
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• v.15 no.2
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• pp.209-216
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• 2017

Purpose: The purpose of this study was to compare the status of the dementia prevention programs, dementia support centers, and elderly welfare centers in major metropolitan cities to acquire data for future program development and dissemination and the specialization of dementia prevention personnel. Methods: Data were gathered through internet surveys and telephone questionnaires from 15 special demented elderly care centers and elderly welfare centers registered in five metropolitan cities from June 27 to Oct 25, 2016. Results: Dementia care programs were available at 15 centers. Seoul City was running the most diverse dementia programs, and all five cities were spending a significant amount of time on the cognitive therapy program within several dementia programs. In addition, many social workers hosted the program and the frequency of social welfare work was three times a week. Conclusion: To increase the dementia prevention policies' efficiency, an understanding of dementia has already been established. Experts who can provide client-centered, problem-solving programs will play the role of physical therapists and occupational therapists. However, more research is needed.

• Journal of the Korean Society of Clothing and Textiles
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• v.10 no.3
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• pp.83-93
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• 1986

This study is aimed at providing guidelines to settle unified terminologies that can be used in education, industry and factories by identifying the problems in the use of complicated terminologies concerning manufacture of western costumes. The results of the study reveal that educational terminologies tend to be more Korean languages whereas the terminologies used in practice consist of main streams of Japanese words which were transmitted erroneously, thus causing barriers of communication between the two fields, being same points to be called differently and being the terminologies pertinent to Korean costumes mistakenly used for western costumes. The confusion of use of professional terminologies is significant problem to be sotted in view point not only of the economic aspects of low productivity but also of the settlement and transmission of Korean culture. Therefore, the administrative measures are badly in need to solve all these problems. The following points are recommended to solve these problems on the basis of the findings of this study. 1) In principle the mistakenly transmitted Japanese words and the mixed up terminologies should be Koreanized, but those words for which there are no proper Korean words and complicated words difficult to commumicate can be replaced by the standardized pronunciation of the original words. 2) The words for Korean costumes which are mistakenly used for western costumes should be expressed by the standard of western costumes. 3) The readily localized foreign terminologies had better be used as they are. 4) The variety of terminologies indicating same points should be Koreanized in unification to best express the true meaning of the original words. 5) The misspelled Korean words and the dialect of Korean words should be standardized.

• Economic and Environmental Geology
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• v.29 no.5
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• pp.575-587
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• 1996

The purpose of this study is to develop geostatistical methods for selection of prospective areas of polymetallic nodule deposits in KODOS (Korea Deep Ocean Study) area of the North-East Pacific Ocean. In this study $110{\times}165$ grid system was used, and each node represents the center of an estimated block of $1km{\times}1km$. The ordinary kriging was applied to SeaBeam2000 data in order to evaluate the bathymetry. A structural analysis (variogram) of the bathymetry data was carried out for constructing digital terrain model (DTM) and the maximum slopes of the bathymetry were calculated by DTM data. The above method can be used to solve the problem that is resulted from the lack of theory of a change of support model for the maximum slope of the bathymetry. The ordinary kriging and the indicator kriging were used to evaluate the nodule abundance, and the different two kriging methods were compared to evaluate the accuracy for the estimation of the nodule abundance. It has been shown that indicator kriging was better estimation tool than the ordinary kriging. The overlay map is presented for the selection of potentially minable sites by combining the two indicator maps of the nodule abundance and the maximum slope of bathymetry. This overlay map could be utilized to establish follow-up survey and to investigate the potentially minable sites in the KODOS area.

• Journal of Korean society of Dental Hygiene
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• v.15 no.3
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• pp.461-475
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• 2015

Objectives: The purpose of the study is to investigate the related factors of oral health-related quality of life in the severely disabled people. Methods: The subjects were 205 severe disabled people in Busan and Gyeongnam. Data were collected by direct interview with the severe disabled persons from June to August, 2011. The study instruments included oral health impact profile(OHIP)-14 and Korean instrumental activities of daily living(K-IADL). Data were analyzed by SAS version 9.2. The questionnaire consisted of eight questions of the general characteristics of the subjects, five questions of oral health related problem, seven questions of K-ADL, ten questions of K-IADL, fourteen questions of oral health related quality of life. Results: The severely disabled's IADL was $19.9{\pm}7.8$ and the oral health-related quality of life was $17.5{\pm}10.5$. In multiple regression analysis, oral health-related quality of life was closely related to multiple disorders and IADL. Conclusions: The oral health-related quality of life was poor in the severely disabled people. It is necessary to provide the severely disabled people with self-supporting tools that help ADL and IADL.