• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.17 no.6
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• pp.160-168
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• 2003

In Korea, a large portion of aerial power-transmission cables is installed in the mountains. In the case of a fire in the mountains, steel wires coated with zinc and aluminum wires of those power cables exposed to the fire or near around will be deteriorated by the blaze and the high temperature. Deterioration proceeds by interactions of a variety of factors like quality, manufacturing process, the condition of installation and exposure environment of a wire, and so on. Generally, the characteristic of a conductor affect by a forest fire can not be analyzed without the effect through simulating a forest fire. However, there are little research accomplishments of that kind of simulation about it, and there's been no analysis of a sample exposed to an actual forest fire. This thesis shows the experimental results that apply to a new wire by an artificial flame-maker because it's difficult to directly analyze the characteristic of deterioration by a forest fire. Those results include the intensity of extension and wrench for a conductor. In addition, there's been an experiment and analysis about the mechanical characteristics of the wire of ACSR 480[$\textrm{mm}^2$] which was removed from Pohang area by a forest fire. Then, the database will be made to predict the state of deteriorated wires by a forest fire using those two data, and data necessary to diagnose the life state of an ACSR wire affected by a forest fire will be given.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.17 no.6
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• pp.95-104
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• 2003

The electric traction systems are quite differ from general power systems which is single-phase and heavy load. Therefore, there are inevitably power quality problems such as steady state or transient voltage drop, voltage imbalance and harmonic distortion. Among these problems, since steady-state volatge drop is the one of most important factor in electric power quality, many researches about on the compensation of volatge drop by using SVC(Static Var Compensator) and/or STACOM(Static Compensator) have been studied and proposed Also, it is expected that transient voltage drop(voltage sag) could affect the control and safety of high speed traction load. In this paper, voltage sag compensation of AT(Auto Transformer) feeding system are studied The detailed transient models of utility source, scott transformer, AT, and traction load are estabilished. The application of DVR(Dynamic Voltage Restorer) in electric traction system is proposed to compensate the voltage sag of traction network which is occured by the fault of utility source. It can be shown that application of the DVR in electric traction system is very useful to compensate the volatge sag from the result of related simulation works.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.5
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• pp.431-439
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• 2013

A cooling system is adopted to control the thermal load from the avionic equipments in an aircraft for stable operation. In this study, an avionic cooling system was designed and manufactured by adopting a vapor compression cycle with a closed-loop air-circulation system to investigate the operating characteristics of an alternative refrigerant. The performance characteristics of a cooling system adopting R236fa as an alternative refrigerant were experimentally determined by varying the refrigerant charging amount, expansion valve opening, and compressor rotation speed. The experimental results were analyzed and compared with those of a cooling system adopting R124 as a refrigerant. The possibility of the adoption of R236fa as an alternative refrigerant was verified, and design solutions were suggested to improve the system efficiency.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.155-155
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• 2011

용융탄산염 연료전지(MCFC)는 $650^{\circ}C$에서 작동하는 고온형 연료전지 시스템이다. 이 시스템은 천연가스 등을 개질하여 생산된 수소를 바로 전기로 생산할 수 있는 시스템으로 열효율이 높으며, 현재 대체 발전시스템으로 각광을 받고 있다. MCFC는 개질방식에 따라 내부개질 방식과 외부개질 방식이 있다. 내부개질 방식은 수소를 생산하는 개질기가 스택내부에 장착된 형식으로 천연가스를 스택내부에서 개질하여 바로 전기를 생산하는 방식이다. 이 내부개질반응에 사용되는 촉매로는 알루미나에 고함량 (약 50 wt.%)으로 담지된 니켈(Ni) 계열촉매이 주로 쓰이고 있다. 이 고함량으로 담지된 촉매는 대부분 높은 활성을 보인다. 비교적 낮은 온도 운전조건 (약 $580{\sim}620^{\circ}C$)을 가지는 MCFC 내부개질에 적용하기 위해서는 활성점인 니켈을 최대한 담지체에 고르게 분산 시켜야한다. 이를 위해서 MgO를 이용하여 촉매의 활성점을 높게 분산시키는 연구를 진행 하였다. 촉매를 제조하는 방법으로 요소(urea)를 이용한 균일용액침전법을 이용하였다. 니켈함량은 50 wt.%로 고정을 한 다음, MgO 양과 $Al_2O_3$ 양을 각각 0 ~ 45 wt.%와 5 ~ 50 wt.%로 조절하면서 촉매를 제조하여 그 특성들을 분석하였다. 물성을 비교하기 위해서, X-선 회절분석 (XRD) 및 TPR, 물리화학흡착 실험을 하였다. 촉매의 활성을 살펴보기 위해서, fresh 상태 및 피독 상태에서 메탄수증기 개질활성 실험을 실시하였다. MgO 함량이 없거나 적은 촉매에서는 높은 BET surface area와 작은 NiO, metallic Ni 결정 크기가 나타났다. 반면 MgO 함량이 높은 촉매에서 낮은 BET surface area와 비교적 큰 NiO, metallic Ni 결정 크기가 나타났다. 또한 XRD 분석에서 MgO 함량이 증가할 수 록 MgO 결정 피크가 명확히 나타났으며, $MgAl_2O_4$ 피크는 나타나지 않았다. TPR 분석에서 촉매들의 환원 피크를 측정한 결과, 저함량의 MgO를 포함한 촉매는 $700^{\circ}C$ 부근에 환원 피크가 관찰되었고 MgO가 고함량인 촉매는 환원 피크가 $400^{\circ}C$ 부근에서 관찰되었다. 촉매의 초기 fresh 상태에서의 활성은 고함량 MgO를 포함한 Ni-90M10A 샘플을 제외하고 모든 촉매가 거의 비슷하게 나타났다. 그러나 $K_2CO_3$ 피독 상태에서는 MgO 함량이 증가할 수 록 활성이 좋지 않았음을 알 수 있었다. 따라서 MgO가 소량 포함된 촉매의 경우 fresh 상태에서는 우수한 물성과 활성을 보이지만, 피독상태에서는 MgO가 포함되지 않은 Ni-$Al_2O_3$ 촉매가 우수한 활성을 보였다.

• Journal of Korean Society of Environmental Engineers
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• v.38 no.7
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• pp.387-394
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• 2016

Commercial 28 algae removal technologies that have been applied in domestic rivers and lakes with green tide were investigated, analyzed and classified. The classification of algae removal technologies was based on the three criteria (i.e., principle, flow rate of water body, and application period). Also, algae removal technologies were evaluated in terms of cost effectiveness, field applicability, effect durability, and eco friendliness. From the analysis results, technologies using physical, chemical, biological, and convergent controls were 32.2%, 25%, 21.4%, and 21.4%, respectively. The 75% of technologies have been applied to stagnant water body (${\leq}0.2m/s$). Also, algae harvesting ship with dissolved air flotation, conveyor belt and filtration processes and natural floating coagulant were found to have better field applicability, compared to other technologies. However, proper algae removal technology in specific rivers and lakes should be chosen after the evaluation of long-term pilot scale field test. Also, development of energy and resource recovery technologies from algae biomass is warranted.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.12
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• pp.6427-6433
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• 2013

For trains to run safely and quickly, the train should always follow the preceding train at a proper spacing. For this purpose, a certain distance between the stations is set for each block section. For the safe operation of trains in one block section, only one train service for an automatic block system is needed. The existing block system is composed an ABS, which is a linked track circuit and line sideway system through the interlocking system. The interlocking system is being replaced with a domestic electronic interlocking system. On the other hand, the block system still uses the relay format of an analog system, and is independently installed of the line sideway systems. Therefore, the existing block system has many problems in terms of construction and maintenance. In addition, the existing domestic line is used for ABS and LEU , which is installed separately, despite the train being controlled by the information of the same signal at the same location. This is not efficient in terms of each product price and the maintenance costs. This paper introduces an integrated electronic block system and the field test results. The field test was carried out through a periodic inspection performed eight times from January to late August.

• Korean Chemical Engineering Research
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• v.48 no.1
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• pp.68-74
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• 2010

In this study, fluidized-bed pyrolysis has been conducted in order to recover the bitumen contained in the oil sand. Canada Alberta oil sand contains 11.9% of bitumen and the bitumen-derived heavy oil produced in fluidizedbed tends to be upgraded relative to the bitumen. The continuous operation has been performed using $N_2$ as a fluidization gas at 1 atm and $500^{\circ}C$ in a reactor of 170 cm height. The results showed 87.76% of bitumen conversion, where liquid products are 74.45% and gas products are 13.31%. $H_2$, $O_2$, CO, $CO_2$, $CH_4$, and NO and $C_1{\sim}C_4$ hydrocarbons in the gas products were analyzed by on-line gas analyzer and gas chromatography, respectively. The pyrolysis oil was analyzed by using proximate analysis, heavy metal analysis, SIMDIS, asphaltenes, and heating value. By SIMDIS analysis, naphtha was 11.50%, middle distillation was 44.83% and heavy oil was 43.66%. It was obvious that the pyrolysis oil was upgraded compared with bitumens.

• Journal of the Korean Society of Marine Environment & Safety
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• v.22 no.5
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• pp.547-553
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• 2016

Black carbon (BC) contained in particulate matter (PM) originating from the exhaust gases of ships' diesel engines has been receiving great attention as a cause of glacial melting and warming in the polar regions. In this study, we took samples from various locations of PM emitted from the training ship (T/S) HANBADA's main engine, in cooperation with the Korea Maritime and Ocean University. We analyzed the structure and characteristics of these samples using high-resolution transmission electron microscopy (HR-TEM) and applied our findings as fundamental research for developing PM reduction technology. We also employed our results to determine appropriate preemptive action to meet upcoming PM/BC regulations. In addition, we confirmed the emission trend of pollutants from exhaust gases under various engine operating conditions using an exhaust gas analyzer. Results obtained from the analysis of HR-TEM images showed that the structure of the PM is chain-like wispy agglomerates consisting of a number of individual spherical particles. As the sampling location was moved away from the turbo charger (T/C) towards the funnel, more condensates were observed at a low temperature and the molecular structure of the PM lost its characteristic BC structure as an amorphous structure gradually appeared. Furthermore, through the analysis of exhaust gases, we predicted a decrease in PM concentration in the exhaust stream as engine rpm increase.

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.6
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• pp.674-680
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• 2014

Monitoring systems of informations for ship performance have become important gradually for economical management of existing ship. Monitoring of NOx emission from marine diesel engines is one of them. The measurement of NOx emission, however has been many difficulties due to technical and costly problems. A monitoring by prediction method of NOx on-board ship according to sailing condition of ship could be an useful method. In this paper, it is discussed about modified method of one-zone model which has been utilized usually for analyzing the combustion process. The modified method is able to calculate the temperature of burned region from the result by one-zone model. Influences which excess air ratio during combustion process affected for the gas temperature and NOx emission were investigated. From the results variation of excess air ratio during combustion process could be estimated inversely through the comparison with measurement of NOx emission.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.11
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• pp.1437-1443
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• 2013

Railways are currently subject to the enforcement of speed limits for each curve as prescribed by the Railway Operating Rules in Korea. However, research is required to determine the maximum speed of trains passing through each curve that allows them to run without the risk of derailment in relation to the speed enhancement of existing railway tracks. In addition, factors affecting the running safety of railway vehicles can be classified into those in terms of vehicle aspects and those in terms of track aspects. This study sought to analyze the running safety of railway vehicles according to changes in the inclination of the rail from among the factors affecting the enhancement of safety against derailment. To increase the speed of trains passing through curves that have high derailment risk, this study also analyzed the running safety of railway vehicles according to the inclination of the rail and changes in running speed while a vehicle passes through each curve section in both the up and the down train line sections between Namsunghyun and Chungdo, which represent the actual conditions of railway tracks.