• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 추계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.92-94
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• 2003

The autotransformer currently used on the electric railway system is made of class A insulation material and uses the paper insulation method. As a power converter supplying power to the trolley wire, the autotransformer is one of critical equipment in the railway system. In the autotransformer, load irregularly changes and overload often occurs. These cause overheating of the autotransformer and facilitate deterioration of the autotransformer resulting in burnout accidents due to insulation breakdown. Also, the current autotransformer has poor insolation and short-circuit strength which often badly affect the service life of the transformer, and needs to improve its quality urgently. To overcome one of existing shortcomings of the mold transformer, manufacturers use epoxy resins that have superior flame retardancy to get rid of fro and explosion possibilities during accidents. Currently, new mold transformers are used in indoor distribution facilities with fire-fighting equipments. Coils molded in epoxy resins do not have their insulation performance compromised by humidity, dust, etc enabling easy inspection and maintenance. Comparing to the oil immersed transformer, the mold transformer does not have any concern about environmental pollutions by oil leak or replacement Therefore, to reduce breakdowns and improve reliability of the autotransformer, it is necessary to develop a new mold autotransformer with low loss suitable for our environment to suppress breakdowns of the autotransformer and improve the reliability. This study is about development of a low-loss mold autotransformer necessitated by reasons mentioned earlier.

• 정보과학회 컴퓨팅의 실제 논문지
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• 제23권4호
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• pp.238-243
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• 2017

본 논문은 WebRTC(Web Real-Time Communication) 기반의 화상회의 솔루션에 이기종 단말을 연동 시킬 수 있는 시스템의 구조에 관한 연구이다. 본 시스템은 WebRTC 기반의 단말과 미디어 협상에 필요한 시그널을 중계 해 주는 시그널 서버, 이기종 단말과의 연동 인터페이스를 제공하는 MCU, MCU에 연동되는 이기종 단말들로 구성 된다. 본 기술을 사용하면 WebRTC 기반의 화상회의 솔루션과 레거시 장비들간의 상호 호환성을 확보할 수 있게 해 준다. 또한, 새로운 기술로 개발 된 솔루션으로의 대체로 인해 발생되는 비용의 낭비를 줄일 수 있을 뿐만 아니라, 기존의 레거시 장비들도 다자간 회의 참여를 가능하게 해 주기 때문에 회의 시스템의 사용성 증대를 기대할 수 있게 해 준다.

• 의료ㆍ복지 건축 : 한국의료복지건축학회 논문집
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• 제25권4호
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• pp.27-35
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• 2019

Purpose: As the improvement in quality of medical environment and the spatial consideration for the prevention of infection in the hospital have become increasingly important in the recent years, specific and practical planning for air conditioning room's area has become a major issue accordingly. However, the air conditioning room tends to be discussed focusing on technical factors such as air conditioning systems that are irrelevant to building plans, while discussions of most departments related to the medical functions have actively taken placed. Therefore, this study aims to investigate the factors influencing the planning for the air conditioning room area, and through subsequent analysis of the area of the air conditioning room, to propose a way to improve effective planning for the air conditioning room area. Methods: This study examines the case hospitals that fall into two types: each floor supply system and concentrated supply system, and compares and analyzes the air conditioning room area-related factors and the characteristics of changes in the interior of air conditioning room before and after remodeling through air conditioning floor plan of those case hospitals. Results: The air conditioning room can be classified into the net area of the functional space such as duct passages, and the public area such as aisle space, and of those the public area is an important factor in calculating the area of the air conditioning room. The public area of the air-conditioning room should not be planned considering only the spaces for mobile passage or maintenance activities, but should be planned taking into account internal changes such as expansion and replacement of equipment in the future from the beginning. Implications: When planning a medical facility, it is used as basic data for the planning of the air conditioning room area, which is a significant fixed factor in the initial setting.

• 전기학회논문지
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• 제63권8호
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• pp.1064-1069
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• 2014

The railway signalling system plays an essential role in the headway and routing control for a safe and efficient train operation. The reliable and safe operation of the system is very important because the failure of the railway signalling system can lead to the collision, derailment, or unexpected stop of a train. So far, the conventional wayside signal mode (ATS: Automatic Train Stop) has been generally used as the railway signalling system. However, this system is highly linked to a risk of major accidents resulted from human mistakes such as missing a signal or careless control of train speed. Accordingly, the onboard signal mode (ATC: Automatic Train Control) as an alternative of ATS has been recently introduced and applied to transmit effectively the information on speed control of a train by using computers and communication equipment. In the process of replacing the obsolete signal system, it is necessary to switch over the system while providing passengers with normal services. Therefore, the integration of a railway signaling system compatible for both ATS and ATC and its interface is discussed in this study. In particular, the implementation scenario required for operation planning of the integrated system was designed, and the results as well as effects of its applicability test were also presented.

• 한국주거학회논문집
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• 제28권1호
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• pp.37-44
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• 2017

This study focuses on the university dormitory remodeled toward energy efficiency. The study has its purpose on deriving the aspects to be concerned for later green remodeling and enhancing the effects of green remodeling, by analyzing the changes of physical environment, changes of energy consumption amount, and needs of the residents. For this purpose, the study went through the review of project report from government office for green remodeling, field investigation of remodeling elements, and the occupancy evaluation by Focus Group Interview. FGI means interviewing small group of the residents who lived in the subjected dormitories both before and after the remodeling. As results, the elements of green remodeling in targeted dormitories were inner wall insulation, top-floor ceiling insulation, replacement of windows, installment of automatic entrance door and making transfer space connected the entrance door. As the parts of equipment system, EHP high-efficiency cooler, highly efficient radiator, upgraded LED lightings with covers, and automatic control system (only one building) were installed. Energy consumption was declined, and the satisfaction of residents was increased after the green remodeling. However, the aspects which were not improved or unsatisfying also have been detected. Therefore, the study states the suggestions each for the administrators, designers and planners, and residents to concern for enhancing the effects of green remodeling or construction of new dormitories.

• Asian-Australasian Journal of Animal Sciences
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• 제26권6호
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• pp.864-873
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• 2013

In developing countries, biogas energy production is seen as a technology that can provide clean energy in poor regions and reduce pollution caused by animal manure. Laboratories in these countries have little access to advanced gas measuring equipment, which may limit research aimed at improving local adapted biogas production. They may also be unable to produce valid estimates of an international standard that can be used for articles published in international peer-reviewed science journals. This study tested and validated methods for measuring total biogas and methane ($CH_4$) production using batch fermentation and for characterizing the biomass. The biochemical methane potential (BMP) ($CH_4$ NL $kg^{-1}$ VS) of pig manure, cow manure and cellulose determined with the Moller and VDI methods was not significantly different in this test (p>0.05). The biodegradability using a ratio of BMP and theoretical BMP (TBMP) was slightly higher using the Hansen method, but differences were not significant. Degradation rate assessed by methane formation rate showed wide variation within the batch method tested. The first-order kinetics constant k for the cumulative methane production curve was highest when two animal manures were fermented using the VDI 4630 method, indicating that this method was able to reach steady conditions in a shorter time, reducing fermentation duration. In precision tests, the repeatability of the relative standard deviation (RSDr) for all batch methods was very low (4.8 to 8.1%), while the reproducibility of the relative standard deviation (RSDR) varied widely, from 7.3 to 19.8%. In determination of biomethane concentration, the values obtained using the liquid replacement method (LRM) were comparable to those obtained using gas chromatography (GC). This indicates that the LRM method could be used to determine biomethane concentration in biogas in laboratories with limited access to GC.

• Tribology and Lubricants
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• 제33권2호
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• pp.37-44
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• 2017

A DE-side LBP tilting pad journal bearing of a 1-stage overhung heat-pump compressor in a propylene process exhibited abnormal high-temperature behavior. Its temperature had been relatively high at $78^{\circ}C$ from the beginning of operation. In 2014, after three years of operation, it increased suddenly and reached $103^{\circ}C$. Installing a varnish removal equipment and others managed to stabilize the temperature at $95^{\circ}C$. We undertook a troubleshooting approach for reviewing the comprehensive status and integrity of the temperature design of the bearing. We performed lubrication and heat-balance analysis, based on the design engineering data and documents supplied by the OEM. For the base design data of DE-side TPJB, evaluating the effects of key design variables on bearing metal temperature showed that firstly, increasing the bearing clearance and supply oil flow-rate, and next, changing the oil type, and finally, increasing the machined pad clearance and offset, are more effective in reducing the bearing metal temperature. Furthermore, a clarification meeting with the OEM revealed that an incorrect decision had been made to decrease the bearing clearance to eliminate the SSV harshness issue, while not maintaining a sufficient oil flow-rate. We conducted a detailed retrofit design analysis, wherein we increased the oil flow-rate and bearing clearance by decreasing the preload. We predicted that the bearing temperature would decrease to $63^{\circ}C$ from $75.7^{\circ}C$ even at the rerate condition. Finally, after installing and operating a retrofit replacement bearing in 2015, the bearing temperature stabilized at a low temperature of $65^{\circ}C$. Currently (January. 2017), two year later, the bearing metal temperature remains at $65^{\circ}C$. Therefore, we can conclude that the abnormal high-temperature behavior of the bearing has been resolved completely.

• 대한방사선기술학회지:방사선기술과학
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• 제14권2호
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• pp.15-21
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• 1991

Experiment was conducted on the image quality and exposure dose following replacement of $CaWO_4$ system screen BH-III and BX-III which have so far been used for high-voltage hard-radiation quality radiography, with rare earth system screen KO750, combined with high contrast film SRH, while additional filter was altered, Cu 0.8 mm+Al 1.4 mm(HVL : Al 8.8 mm), Cu 1.3 mm+Al 1.0 mm(HVL : Al 10.6 mm) and Cu 1.8 mm+Al 1.5 mm(HVL : Al 11.4 mm). AS a result, visual evaluation did not detect extreme changes in image quality under the respective condition(HVL : $Al\;8.8\;mm{\sim}Al\;11.4\;mm$). It was noted, however, that surface exposure dose declined with an increase in the thickness of the additional filter, as it was $18.9\;{\mu}Gy$ at HVL Al 8.8 mm, $17.5\;{\mu}Gy$ at Al 10.6 mm and $15.7\;{\mu}Gy$ at Al 11.4 mm. Considering the limited rating of X-ray equipment and wear of machinery, however, the range of $Cu\;1.3\;mm{\sim}1.8\;mm+Al\;1.0\;mm{\sim}1.5\;mm(1/16\;VL{\sim}1/32\;VL)$ seemed to be a limit.

• 한국콘텐츠학회논문지
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• 제18권1호
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• pp.422-430
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• 2018

최근 유가 상승과 건물 에너지 소비 증가는 에너지 자원 해외 의존도가 높은 우리나라에 큰 부담이 되고 있다. 이런 상황에서 에너지 소비량의 40% 수준을 차지하는 빌딩건물의 에너지절감은 매우 중요한 이슈가 되는데, 본 연구는 ICT를 활용하여 건물에너지 소비량 및 전력사용요금 절감을 하는 최적제어방법을 구현한 실증 분석을 병원을 대상으로 수행하였다. 먼저 기존의 냉난방용 흡수식 냉온수기와 급탕용 보일러시설 일부를 수축열 히트펌프로 대체하고 사용하는 요금제의 조정을 통해 에너지소비량을 줄이고 요금을 절감하였다. 여기에 환경(외기온도, 사용량 증감 등) 변화를 고려한 ICT 기반 최적제어 기능을 추가적으로 적용함으로 기존 설비 대체 중심의 에너지절감 방법과 ICT 기반의 최적제어방법까지 고려한 효과를 분석하였다. 그 결과 본 연구에서 병원 대상의 최적제어방법은 에너지효율화 설비 적용으로 인한 절감량(53.6%)에 최적자동제어 효과(18.2%)까지 추가적으로 절감할 수 있는 것을 확인하였다. 본 연구 결과를 바탕으로 건물 에너지 절감 성과를 높이는 다양한 방안을 검토해 볼 수 있을 것이다.

• 자원리싸이클링
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• 제6권4호
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• pp.11-16
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• 1997

x-ray 필름 정착과정에서 발생하는 폐액 중에 함유된 은의 평균농도는 약 1,500mg/$\ell$ 정도이므로 폐수를 처리없이 방류할 경우 수생태계에 독성을 나타낼 수 있어 방류전에 처리할 필요가 있다. x-ray 필름 정착과정에서 발생하는 폐수를 처리하는 방법으로는 전기분해, 화학침전법, 금속치환법 등이 알려져 있으나 본 연구에서는 시약용 이산화망간과 폐건전지에서 회수한 이산화망간을 흡착제로 하여 정착폐액에 함유된 은 성분을 흡착하였다. 회분식 및 연속식 실험에서 시약용 이산화망간(MDO)을 사용하였을 경우 흡착결과가 우수하였으나 폐건전지에서 회수한 이산화망간(RMDO)도 흡착제로서 우수함을 알 수 있었다.