• 한국동물위생학회지
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• 제25권1호
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• pp.75-86
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• 2002

Outbreaks from September 1999 to July 2000 of blackleg in 4 milking and fatting cattle farms in the vicinity of Munkyong(northwestern part of Gyeongbuk province) were investigated biochemical characteristics of isolates and were surveyed epidemiological works during the period of 2 months from August to September 2000. Clostridium chauvoei, the etiological agent of blackleg is a serious pathogen of cattle and sheep causing fever, depression and lameness with high mortality in growing phase of 6 to 18 months old mainly beef cattle. Biochemical and cultural properties of 4 isolated Cl chauvoei were identical to those of reported results and isolates were susceptible to ampicillin, bacitracin, chlorarnphenicol, cephalothin, ciprofloxacin, erythromycin, norfloxacin, penicillin, and tetracycline, while they were resistant to amikacin, colistin, gentamicin, kanamycin, neomycin, streptomycin and trimethoprim-sulfamethoxazole. In the results of epidemiological survey, outbreak farms that concentrated region of milking or fatting cattle in each sites were so close contact within a radius of about 1km that they are separated only by wire fence or shrub harrier and flies, rodents, wild cats and birds could have the chance to move around between those farms. The origin of the outbreak blackleg were uncertain, but the transmission between farms were mainly through the movement of farm personnel, vehicles which were struck the feces or manures from farm and other mechanical factors such as flies, rodents and birds furthermore occurred 4 farms were not vaccinated. In conclusion, a periodic disinfection, vaccination and quarantine prevention are ideal methods of damage reduction by blackleg.

• 전기학회논문지
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• 제65권3호
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• pp.526-531
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• 2016

This paper presents an experimental study on the optimal settings for the selected DC fault relay (50F) to improve the operating performance for the high-speed circuit breaker on DC feeding system which ensure safety within rolling stock maintenance depot. In this study, current supplied to overhead contact wire was calculated on 1 ms interval to analyze the correction values of DC fault selective relay for the operation of current supply cutout. Particularly, standards for the accurate detection of accidents between an electric railway vehicle and the electric power facilities are shown by investigating the optimal correction values for detection of fault current, and the results indicated that it takes about 213 ms for the DC fault selective relay(50F) to fully open. In the future, the correction values of DC fault selective relay suggested in this paper will be used as the reference values of protective relay for the safe operation of DC electric railroad system such as urban railway.

• 대한기계학회논문집A
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• 제28권5호
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• pp.517-523
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• 2004

Recently, wheel slip controllers with controlling the wheel slip directly has been studied using the brake-by-wire actuator. The wheel slip controller is able to control the braking force more accurately and can be adapted to various different vehicles more easily than the conventional ABS systems. The wheel slip controller requires the information about the tire braking force and road condition in order to achieve the control performance. In this paper, the tire braking forces are estimated considering the variation of the friction between brake pad and disk due to aging of the brake, moisture on the contact area or heating. In addition, the road friction coefficient is estimated without using tire models. The estimated performance of tire braking forces and the road friction coefficient is evaluated in simulations.

• 전기학회논문지
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• 제60권3호
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• pp.674-679
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• 2011

In this paper, we experimented and analyzed about electric fire risk assessment methods of LED lightings for outdoor. LED lighting is composed of AC power lines, AC/DC converter, DC power lines and LED lamps. There are some risk factors of electric fire in LED lighting such as short circuit between power lines or power line and ground, dielectric breakdown, leakage current, abnormal voltage inflow, poor contacts(connections), etc. As a result of this study, insulation coverings of wire was ignited due to dielectric breakdown between power lines and molten marks were formed in copper conductor. LED lighting was blown out while short circuit, beside that, electrical disorder did not occur. When abnormal voltage was inflowed, electronic components such as varistor, condenser were damaged. Partial heating was produced and insulation was melted and carbonized by arc and heating while poor contacts were happened. We expect that the results of this study would be helpful for electrical safety of LED lightings for outdoor.

• 전기학회논문지
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• 제64권10호
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• pp.1517-1522
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• 2015

Since electric railroad vehicle pass through repeatedly on the railroad bridge, the dynamic load that causes the change of tension of contact wire affect it constantly. In this paper, we measured the dynamic displacement of the railroad bridges to analyze the effect of tension in the catenary. A result of dynamic measurement of the longitudinal displacement, it's maximum value was 39.9mm which was lower than the primary management criteria 378mm. Also on the based of a maximum temperature, it shows a feature that the longitudinal displacement value increased as temperature rise from April to October. In terms of behavior characteristics of a tensioning device, it was confirmed to be the value of 50mm stroke movement when the temperature changes ±5℃.

• 한국해양공학회지
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• 제27권5호
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• pp.77-81
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• 2013

The effects of the welding parameters, contact tip-to-workpiece distance (CTWD), current, and voltage on the diffusible hydrogen content in weld metal deposited by self-shielded flux cored arc welding were investigated and rationalized by comparing the amount of heat generated in the extension length of the wire. This showed that as CTWD increased from 15mm to 25mm, the amount of heat generated was increased from 71.1J to 174.8J, and the hydrogen content was decreased from 11.3mL/100g to 5.9mL/100 g. Even if little difference was observed in the amount of heat generated, the hydrogen content was increased with an increase in voltage because of the longer arc length. A regression analysis showed that the regression coefficient of voltage in self-shielded flux cored arc welding is greater than that in $CO_2$ arc welding. This implies that voltage control is more important in self-shielded flux cored arc welding than in $CO_2$ arc welding.

• Journal of Welding and Joining
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• 제28권2호
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• pp.54-59
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• 2010

The effects of welding parameters such as contact tip-to-work distance (CTWD), voltage, and current on the weld metal diffusible hydrogen contents (HD) were investigated and rationalized by the calculation of heating time and amount of heat generated in the extension length of flux cored wire. As CTWD increased from 15 to 25mm, HD decreased from 8.46 to 5.45mL/100g deposited metal. Calculations showed that, with an increase of CTWD, the amount of heat generated increased from 46 to 92J in addition to an increase of heating time. Increase of current from 250 to 320A, however, gave little variation of HD. It showed that no significant change in the amount of heat generated was found, and heating time was decreased with an increase of current. It also showed that CTWD is more influential than voltage in relatively lower heat input ranges, while voltage is more in higher input ranges

• 한국철도학회:학술대회논문집
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• 한국철도학회 1999년도 추계학술대회 논문집
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• pp.333-343
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• 1999

When a high speed train enters a tunnel, wind speed passing through the train in a tunnel section becomes higher due to the reverse flow to the direction of the train. The higher wind speed gives more aerodynamic forces to the pantograph on the train. Therefore, it is necessary to perform aerodynamic and dynamic analyses in order to check whether the current collection of the high speed train, entering the tunnel, still remain permissible or not. In this paper, the aerodynamic analysis has been performed under the assumption that a high speed train at 300 km/h enters a tunnel whose cross sectional area Is 107/㎡ and length is 1000m. In consideration of the aerodynamic analysis results, the dynamic analysis has been performed based on the catenary and pantograph dynamic models in SEOUL-PUSAN high speed rail, using the GASENDO developed by RTRI. In addition, the fatigue life of the contact wire has been reviewed using the Goodman diagram. Based on the analysis results, it is concluded that the increase of the aerodynamic forces on the pantograph in the tunnel section shall not affect characteristics of current collection adversely except that motions of the pantograph may be constrained by bump-stops.

• Korean Chemical Engineering Research
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• 제48권2호
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• pp.172-177
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• 2010

본 논문에서는 SOFC 금속연결재로서 Crofer22APU를 적용하고자 표면에 전도성 산화막($La_{0.8}Sr_{0.2}CoO_3$)을 습식코팅 후, SOFC 작동환경에서 산화거동, 전기적 특성변화 및 미세구조 변화를 관찰하였다. 코팅 전 샌드블러스트 장치를 이용한 Crofer22APU 표면처리를 통하여 코팅막/금속의 접합특성을 개선시킬 수 있었으며, 320 mesh의 입자크기를 갖는 알루미나 분말을 이용하여 표면처리한 경우 접착특성이 극대화되었다.$La_{0.8}Sr_{0.2}CoO_3$ 코팅된 시편의 전기적 특성 평가는 4-wire 법을 이용하여 SOFC 작동환경에서 약 4,000 시간 장기성능 평가하였으며 $12mW{\cdot}cm^2$의 낮은 면저항값을 얻을 수 있었다. 실험종료 후 미세구조 분석결과에서도 전도성 산화막($La_{0.8}Sr_{0.2}CoO_3$) 코팅이 금속의 부식으로 인한 산화층의 생성속도를 늦추고 이로 인한 금속의 전기적 특성이 감소하는 것을 방지하는데 유효함을 확인하였다.

• Current Photovoltaic Research
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• 제2권1호
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• pp.1-7
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• 2014

We developed a method of growing thin Si film at $600^{\circ}C$ by hot wire CVD using a very thin large-grained poly-Si seed layer for thin-film Si solar cells. The seed layer was prepared by crystallizing an amorphous Si film by vapor-induced crystallization using $AlCl_3$ vapor. The average grain size of the p-type epitaxial Si layer was about $20{\mu}m$ and crystallographic defects in the epitaxial layer were mainly low-angle grain boundaries and coincident-site lattice boundaries, which are special boundaries with less electrical activity. Moreover, with a decreasing in-situ boron doping time, the mis-orientation angle between grain boundaries and in-grain defects in epitaxial Si decreased. Due to fewer defects, the epitaxial Si film was high quality evidenced from Raman and TEM analysis. The highest mobility of $360cm^2/V{\cdot}s$ was achieved by decreasing the in-situ boron doping time. The performance of our preliminary thin-film solar cells with a single-side HIT structure and $CoSi_2$ back contact was poor. However, the result showed that the epitaxial Si film has considerable potential for improved performance with a reduced boron doping concentration.