• Tunnel and Underground Space
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• v.33 no.6
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• pp.534-546
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• 2023

If the disc cutter is excessively worn or damaged, it becomes incapable of rotating and efficiently cutting rockmass. Therefore, it is important to appropriately manage the replacement cycle of the disc cutter based on its degree of wear. In general, the replacement cycle is determined based on the results of manual inspection. However, the manual measurements has issues related to worker safety and may lead to inaccurate measurement results. For these reasons, some foreign countries are developing the real-time measurement system of disc cutter wear by using different sensors. The ultrasonic sensors, eddy current sensors, magnetic sensors, and others are utilized for measuring the wear amount of disc cutters. In this study, the applicability of eddy current sensors for real-time measurement of wear amount in TBM disc cutters was evaluated. The distance measurement accuracy of the eddy current sensor was assessed through laboratory tests. In particular, the accuracy of eddy-current sensor was evaluated in various environmental conditions within the cutterhead chamber. In addition, the measurement accuracy of the eddy current sensor was validated using a 17-inch disc cutter.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.44 no.1
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• pp.49-62
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• 2024

Reckless development of the underground by rapid urbanization causes inspection delay on replacement of existing structure and installation new facilities. However, frequent accidents occur due to deviation in construction design planned by inaccurate location information of underground structure. Meanwhile, the electrical resistivity survey, knowns as non-destructive method, is based on the difference in the electric potential of electrodes to measure the electrical resistance of ground. This method is significantly advanced with multi-electrode and deep learning for analyzing strata. However, there is no study to quantitatively assess change in electrical resistance according to geometric conditions of structures. This study evaluates changes in electrical resistance through geometric parameters of electrodes and structure. Firstly, electrical resistance numerical module is developed using generalized mesh occurring minimal errors between theoretical and numerical resistance values. Then, changes in resistances are quantitatively compared on geometric parameters including burial depth, diameter of structure, and distance electrode and structure under steady current condition. The results show that higher electrical resistance is measured for shallow depth, larger size, and proximity to the electrode. Additionally, electric potential and current density distributions are analyzed to discuss the measured electrical resistance around the terminal electrode and structure.

• Journal of the Korean Society for Library and Information Science
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• v.30 no.1
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• pp.89-123
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• 1996

The world has moved from the Cold War between the east and the west and moved toward the age without idealogy. It places emphasis on economic benefit and welfare of its own nation as its main point With this world trend, in order to sam the competitiveness and the reconciliation of the divided nation the north and the south Korea should be united. Once the north and the south are united, information society will be altered with the huge flow of the civilization. At the same time, the issue of how to operate library policies and system, in which effective acquisition, manipulation, accumulation, and dissemination of information un would be very important. From this point of view, the following conclusions are obtained in this study. Firstly, when building a national library preparing for the national unification. it is essential to introduce 1) the concept of policy and system for information society and 2) that of policy and system which has national-culture as its focus. Secondly, it is essential to prepare the cooperative-structure between libraries prior to the national unification. This kind of cooperation should gradually expand to an extent that allows actual benefits such as building union catalog, inter-library loan system, resource sharing, standardized cataloging rules, and exchange of dissertation... etc. Thirdly, developing the library policies and systems for the national unification must be based on the concept of the mutual cooperation as inter-dependent model rather than on the concept of the incorporation-absorption as a dominant model. The next point the principles of the followings in preparing the library policies should be considered: 1) free-competition, 2) revolution of consciousness through the social education, 3) independence and love for humanity, 4) scientific or reasonable thinking, 5) job responsibility, 6) democratic citizenship, 7) mind far collective life, 8) spirit of public interest 9) globalization In addition, the model of the library systems preparing for thenational unification should include the followings : 1) uniformity of library system and its authority, 2) establishment of research institutes for library policy and system, 3) exchange of library establishment and information resources, 4) building library networks, 5) establishment of education systems for the library and information science and enhancement of its quality, 6) modernizing and developing information technology and its transfer. Finally, the libraries in the north and the south has different concepts, goals, information resources, and the different ways of using them. Considering the practical aspects of the libraries and the reasons for their existence, they must structure the mutual cooperative system so as to minimize the shock when confronting the social changes, so-called the national unification.

• KEPCO Journal on Electric Power and Energy
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• v.1 no.1
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• pp.39-46
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• 2015

A outdoor termination installed at the outdoor substation is required to connect undergroud cables and overhead transmission lines. The joint box for AC transmission system is already developed and widely used to interconnect overhead and undergroud systems. But the development of the joint box for DC transmission system was only introduced from China and Japan, but theire developemnt staus and core technologies were not fully reported. In order to implement HVDC systems connecting ovehead transmission lines and undergroud cables, a outdoor termination should be developed, but the detailed specifications and information of this device were not reported. It is estimated that the development of the joint box for DC environment has some technical obstacles including insulating materials, electric field mitigation, thermal temperature rise, and space charge accumuations. Among this, the most important one is the DC elctrical insualtion design. Therefore, in order to investigate the DC elctrical insualton design of outdoor termination, the design of AC slip-on type outdoor termination is reffered, and DC electric field analysis performed to verify the possiblity of application of AC joint box into DC joint box. Especially for DC electric field analysis, temperature rise of insualting materials of a joint box was considered, because the conductivity of materials could be changed due to temperature rise. Furthermore, DC electric field analysis considering transinet state, and polarity reversal state were also investigated to verify which state is the most severe condition for the DC joint box. From the simualtion resulsts, it was shown that the value and the position of maximum electric field was obtained comparing AC state, DC state without temperaure rise, and DC state with temperaure rise. And it was confimred that severe DC electric field was observed considing temperaure rise. Finally, in order to reduce DC eletric field intensifation, different configuration of the joint box was applied and it was not possible to obtain satisfactory results. It means that the slight change of configuration of AC joint box was not the suitable soluton for DC joint box. It is essential to establish novel DC insulaton design skills and method for DC joint box to commercialze this product in the near future.

• The Korean Journal of Archival Studies
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• no.17
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• pp.3-37
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• 2008

In this article, I outlined the archival management system in Early Joseon Dynasty and examined the characteristics of the system. At first, I explained the three aspects of the archival management; the memory of the past, the documentation of the contemporary, and the vision of the future through the documentation. Secondly, I tried to understand the character of the Veritable Record and its compilation by the concepts of archival science such as 'authenticity', 'reliability'. In the memory of the past, the History of a Dynasty(Koryo-Sa) and the Comprehensive History of Eastern Kingdom were included. The arrangement of the past was accompanied with the systematic study of the domestic and foreign histories. At the beginning of the state building, there was many practical need to the experiences of government and social re-construction. It was also the process of the legitimacy establishment of the new dynasty. And the Bureaucracy promoted the development of the records and archival management system because it needed the continuity and evidence of business. The dualistic structure of the records and archival management system was the most unique character of this age. The management of general administrative records was not different from the modern one. But the historical drafts and the compilation of Veritable record were different. Here, I had to examine the characteristics of these procedures by the concept authenticity, reliability, and custodianship. In doing so, I suggested the need of conceptualization of the historical terms such as 'the primary sources' and 'the secondary sources' in historical study. The archival concepts will be the most useful means to that issue. Through the memory of the past and the documentation of the contemporary, they made visions of the future, new vision of the Literati Governance. In this tradition, in spite of the revision of the Veritable records by the new changed political party, both the orignal and the revised remained as the comparative evidence for the future generation in the name of the Black-Red Revised History.