• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.11 no.9
• /
• pp.718-726
• /
• 1998

J-E 특성 AC 임피더스 분석 그리고 주파수- 전도 특성들을 실험하여 임펄스 전류 서지가 ZnO 바리스터의 열화(degradation)에 미치는 영향을 고찰하였다. ZnO 바리스터 시편에 임펄스 전류(300A/$cm^24, 8/50$\mu s$)를 인가시킨 결과, 입계(grain boundary) 특성을 나타내는 비선형계수 $\alpha$와 E\ulcorner\ulcorner의 값은 크게 감소하였으나, 입자 특성을 나타내는 E_{100A}, E_{300A}$ 값에서는 큰 변화가 없었다. 이러한 열화 현상은 입계의 위치한 부성 전하 밀도, $N_s$의 감소에 한 쇼트키 장벽의 변화에 기인한 것으로 나타났다. 임펄스 서지에 의해 열화된 ZnO 바리스터는 AC 임피더스 분석에서 현저한 non-Debye 특성을 보이며, 이는 병렬 RC 네트워크로 모델링한 Cole-Cole 완화 관계식으로 입계의 열화 특성을 잘 설명할 수 있었다. 주파수-전도도 관계를 검토한 결과 Zno 바리스터는 호핑 전도(hopping conduction),\$sigma(\omega)\varpropto\omega^{\eta}$ 특성을 나타내면, 임펄스 서지가 인가된 이후 n 값이 감소하였다. 이는 임펄스 서지에 의해 입RP 결합 상태(defect states)가 호핑 전도가 발생하기 쉽고 다중(multiple)호핑에 의한 전도 메커니즘을 갖는 것으로 고찰되었다.

• Journal of Korean Society of Archives and Records Management
• /
• v.3 no.2
• /
• pp.98-113
• /
• 2003

In comparison with conventional types of documents, photographs present special problems in the management of any archives because of their physical properties and the nature and format of their informational content This paper is case study for the effective photographs management at the university archives. At first, sort out photographic images in the university publications, draw up work sheet by the bibliographic information of the photographic images and construct a bibliographic database based on the work sheet. Secondly, the photographic images is linked with bibliographic database. In result, users can confirm immediately photographic images on the screen by searching OPAC. This paper concludes with a problem and improvement of the photograph database at the university archives.

• Journal of the Korean Society for Library and Information Science
• /
• v.38 no.4
• /
• pp.149-166
• /
• 2004

This study make comparative analysis of the cataloging rules on the edition area included in the KCR4, NCR(2001), AACR2R, ISBD(M), and ISBD(ER). There is a delicate difference between the cataloging rules. The main features on the edition are as the follows. (1) In the bibliography description the concept of the edition is a general application. That is to say, the edition construct the new edition and the impression. The former comes the purview of a change content, the size, and a printing type. The latter publish newly- (2) The requisite for description of the edition area consists of a edition statement, statements of responsibility relating to the edition, additional edition statement, and statements of responsibility following an additional edition statement. Voluntary rules transcribe the parallel edition statement. (3) In the case of the electronic materials special versions on content and Auction indicates as the edition, but the environment of software does not indicate as it. (4) Parallel statement of responsibility relating to the edition, parallel additional edition statements, and parallel statements of responsibility following an additional edition statement are voluntary rules or not transcribed in the edition area.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.8 no.2
• /
• pp.18-24
• /
• 2004

A fuel spiking test was performed to measure the surge margin of the compressor in a gas turbine engine. During the test, fuel spiking signal is superposed on the engine controller demand signals and the combined signals are used to control a fuel control valve. For the superposition, a subsystem composed of a fuel controller and a function generator is used. The real engine test was performed at the Altitude Engine Test Facility (AETF) in Korea Aerospace Research Institute (KARI). In the preliminary test, the fuel spiking signals are in good agreement with the dynamic pressure at the fuel line and at the compressor discharge point. After the preliminary test, a fuel spiking test to measure the surge point at a specific engine speed was performed. The test results show that the fuel spiking test is very effective in the measurement of surge.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.21 no.1
• /
• pp.35-41
• /
• 2007

Recently, there are increasing social needs for stable supply of electric power and securing high quality of information and communication services. In this work, to propose the effective protection countermeasures of information-oriented equipments against lightning surges, the protection effects of surge protective devices(SPDs) were experimentally investigated using actual-sized test circuits in various installation conditions. As a result, it was found that the protection effect of SPDs is quite different depending on the factors, such as the grounding system of power source, numbers of branch circuits, wiring method of grounding leads, and etc. In case of installing SPDs for information-oriented equipments, including all electric power lines and communication lines, the common grounding should be the most effective. Wiring method containing grounding leads with power lines in metal conduit is suitable to improve the surge cutoff performance of SPDs.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.40 no.5
• /
• pp.297-304
• /
• 2016

When a control algorithm is developed to protect automotive compressor surges, the simulation model typically selects an empirically determined look-up table. However, it is difficult for a control oriented empirical model to show surge characteristics of the super charger. In this study, a dynamic supercharger model is developed to predict the performance of a centrifugal compressor under dynamic load follow-up. The model is developed using Simulink$^{(R)}$ environment, and is composed of a compressor, throttle body, valves, and chamber. Greitzer's compressor model is used, and the geometric parameters are achieved by the actual supercharger. The simulation model is validated with experimental data. It is shown that compressor surge is effectively predicted by this dynamic compressor model under various operating conditions.

• Journal of the Korean Society for Library and Information Science
• /
• v.36 no.3
• /
• pp.49-68
• /
• 2002

Througout the literature, various opinions and recommendations are presented concerning educational backgrounds for subject specialist librarianship. However, the Korean library and information science education is designed as the college program, and n, utilization of either minor or double major programs is regarded as the best to produce qualified subject specialist librarians. Nevertheless, the courses in the library and information science should be promoted first. Accordingly, this study starts with the assumption that the subject bibliography course in the library and information science is designed directly or indirectly to educate students as subject specialist librarians. For this, law and law firm library were explored as examples, and then, finally a law bibliography was provided for the training of the law specialist librarians.

• Proceedings of the KIEE Conference
• /
• 2004.05b
• /
• pp.186-191
• /
• 2004

전력계통에서 역률개선을 위해 사용하는 전력용 콘덴서(이하 SC bank)는 전력계통의 운전상 전압 제어와 역율개선이라는 두가지 측면에서 매우 중요한 전력설비이다. 또한 최근에 전력산업 구조조정에 의해 발전분야가 분할되는 시점에서 SC bank의 역할의 중요성이 강조되고 있다. 본 논문에서는 SC의 고장원인이 무엇인지를 현장조사를 통해 수행하였다. 그 결과 SC bank를 구성하고 있는 리액터, 콘덴서, PT, 혹은 CT 흑은 방전코일의 열화원인이 대부분 차단기의 투입서지와 차단서지에 의해 발생되고 있음을 확인하였다 또한 기존의 보호시스템은 SC Bank의 보호에 적합하지 않음을 검토하였다 차단기 서지에 대한 대책으로는 투입시 전압영점투입과 중성점 저항기의 취부로 투입서지 및 차단서지를 효과적으로 감소되는 현상을 모의와 현장실측을 통해 확인하였다. 또한 기존의 보호방식이 과전류와 과전압 부족전압 혹은 CT와 PT를 이용한 차동방식에 의해 셀의 경련변화를 감지하고 있으나 이 경우 보호맹점이 존재하게 됨을 검토하였다. 이러한 보호상의 문제점을 보완하는 방법으로 SC bank는 임피던스가 늘 일정하는 점에 착안하여 전압과 전류를 이용하여 임피던스의 변화량을 감시하고, 또 한가지 방법은 SC bank의 운전특성상 무효전력만을 발생시킨다는 점에 착안하여 만일 유효전력 성분이 SC bank에서 감지된다면 소자의 이상이나 비정상적은 전류경로가 된다는 결론에 도달하고 유효전력감시를 통한 SC bank의 열화감지가 가능하다는 결론에 도달하였다. 본 논문에서 제안한 3가지의 방법, 즉, 첫째 영점투입차단기 채택, 둘째, 중성점 저항기의 도입, 셋째 새로운 보호방식에 의한 기존의 보호맹점의 보완을 제안하였다. 위의 새로운 제안을 현장에 적용하는 경우 제작사의 제작불량을 제외한 운전상의 SC bank의 문제점 및 고장빈도는 현저히 감소하게 될 것으로 사료된다.

• Journal of the Korean BIBLIA Society for library and Information Science
• /
• v.32 no.3
• /
• pp.23-44
• /
• 2021

This research proposed an approach for interlinking bibliographic data used in the existing multicultural institutions in order to support information services of multicultural institutions. It constructed a set of linkage properties that can link the FRBR-based BIBFRAME structure with the existing metadata standards currently adopted in multicultural institutions, including MODS, EAD, and CDWA. As a result, the descriptive elements for the Work level, Instance level, Item level, statement of responsibility, subjects were established in the BIBFRAME syntax. A total of 19 upper level elements, 18 sub-elements, and 12 linkage properties were proposed for the linking of bibliographic data, so that a bibliographic environment was established that can interconnect heterogeneous metadata adopted depending on the types of collections. Through the proposed structure, it is expected that it can be applied to provide sufficient information services more efficiently by linking the dispersed bibliographic data of multicultural institutions in an integrated way.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.17 no.3
• /
• pp.459-466
• /
• 2022

Switching surges are a common type of phenomenon that occur on any sort of power system network. These are more pronounced on long transmission lines and in high voltage converter stations. At AC/DC hybrid transmission lines, the insulation coordination of such lines is mainly dictated by the peak level of switching surges, the most dangerous of which include three phase line energization and AC/DC converter station. The power system structure consist of AC/DC hybrid transmission lines which is combination of AC 765kV and ±500kV HVDC 1 bipole system for contingency analysis. The power system under study and its components are simulated using EMTDC software package, the effects of the various AC/DC mixing power lines are reviewed. The developed models of EMTDC conversion lines based on combination of AC/DC system are simulated and the characteristics of switching surge over-voltage from its results are discussed.