• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2002.02a
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• pp.185-188
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• 2002

In the design of superconducting power equipments such as transformer, cable and fault current limit, knowledge of the dielectric behavior of both liquid and gaseous at very low temperatures is very importance. Especially, Electrical properties of liquid nitrogen($LN_{2}$) and gaseous nitrogen($GN_{2}$) have become of great interest again since the discovery of high temperature superconductors. However, many sources of $LN_{2}$and $GN_{2}$ problems in the test of pancake coil model arising form the deficiency of insulation data. Therefore, this paper describes the results of an experimental study on the ac breakdown voltage($V_{B}$) properties of $LN_2$ and Air under the electrode of simulated HTS pancake coil. The ac breakdown voltage of $GN_{2}$ have been measured by pancake coil-pancake coil gaps over the temperature range of 293 K to 77 K.

• Journal of environmental and Sanitary engineering
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• v.18 no.2
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• pp.67-74
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• 2003

In 15 schools where were chosen each location (East, West, South, North, Central) of Seoul area, 9 items were measured such as thermo circumstance(temperature, relative humidity, air current, intensity of illumination) particulate matter, carbon monoxide, sulfur dioxide, and nitrogen dioxide being based on the school indoor environment standard. It was showed that indoor temperature, relative humidity and air movement were suitable in comparison with school indoor environment standard. Intensity of illumination was suitable in comparison with all schools, only exception 2 schools. In all investigated schools were adequate for carbon monoxide, sulfur dioxide and nitrogen dioxide, in which each indoor environment standard (10ppw, 0.25ppm/hr, 0.15ppm/hr), but in 5 schools the carbon dioxide were exceeded for standard limit 1,000ppm of Korea. Indoor concentration of dust(PM-10) induced from respiration dust the standard of Korea ($150{\mu}g/m^3$) at all schools.

• Journal of Food Hygiene and Safety
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• v.11 no.3
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• pp.189-196
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• 1996

Based on microbiological-chemical test results under simulated time-temperature conditions, total plate count, coliform, and volatile basic nitrogen were selected as effective quality indicators for estimating probable shelf-life on Kim Pab dosirak marketed in convenience stores, and shelf-life at each storage temperature was calculated from regression equation between effective quality indicator standard limit and storage time. Estimated shelf lives of Kim Pab Dosirak were 17, 3 and 2 hours respectively under 1$0^{\circ}C$, 2$0^{\circ}C$ and 3$0^{\circ}C$. Because shelf-life was especially affected by intial values, regression analysis between initial effective quality indicator values and storage hours was performed for the estimation of probable shelf-life on Kim Pab during storage at 10, 20, or 3$0^{\circ}C$.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.1
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• pp.173-180
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• 2004

This paper presents the effect of varying boundary conditions such as ground subsidence, internal pressure and temperature variation for buried pipelines on failure prediction by using a failure probability model. The first order Taylor series expansion of the limit state function incorporating with von-Mises failure criteria is used in order to estimate the probability of failure mainly associated with three cases of ground subsidence. Using stresses on the buried pipelines, we estimate the probability of pipelines with von-Mises failure criterion. The effects of varying random variables such as pipe diameter, internal pressure, temperature, settlement width, load for unit length of pipelines, material yield stress and pipe thickness on the failure probability of the buried pipelines are systematically studied by using a failure probability model for the pipeline crossing ground subsidence regions which have different soil properties.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.773-776
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• 2005

In this paper, For improving the positioning accuracy of hydrostatic table, relationship between temperature of atmosphere and thermal characteristics of hydrostatic table is analyzed, and influence of thermal characteristics on positioning accuracy is also analyzed experimentally. From the experimental results, it is confirmed that positioning error and repeatability is $0.21{\mu}m\;and\;0.18{\mu}m$ when the laser scale which has $0.01{\mu}m$ of resolution is used as feed-back unit. and also confirmed that thermal deformation of scale and supporter, which occurs by the temperature variation of atmosphere, works as limit of repeatability in long time operation.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2004.11a
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• pp.375-380
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• 2004

This paper presents the basic quench protection idea for the HTS(High-Temperature Superconducting) cable. In Korea power system, the transfer capability of transmission line is limited by the voltage stability, and HTS cable could be one of the countermeasure to solve the transfer limit as its higher current capacity and lower impedance[1]. However, the quench characteristic of HTS cable makes HTS cable to loss its superconductivity, and therefore change the impedance of the line and power system operating condition dramatically. This pheonominum threats not only HTS cable safety but also power system security, therefore a proper protection scheme and security control counterplan have to be established before HTS cable implementation. In this paper, the quench characteristics of HTS cable for the fault current based on heat balance equation was established and a proper protection method by FCL(Fault Current Limiter) was suggested.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2009.10a
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• pp.335-338
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• 2009

In this study, in order to investigate the thermal and electrical properties of ZnO arrester block against 60[Hz] AC voltage, the changes in leakage current were measured. The temperature distribution appearing on the ZnO arrester blocks was observed using a forward looking infrared camera. In particular, the correlation between the thermal and electrical properties of a ZnO arrester block was analyzed experimentally. From this analysis, the thermal phenomena resulting from the heat generation and dissipation of the ZnO arrester block were interpreted. The degradation and thermal runaway phenomena of ZnO arrester block are closely related to the temperature limit of the ZnO arrester block. The installation of an additional metal electrode has resulted in the decrease of the leakage current due to the heat dissipation.

• Journal of the Korean Society of Combustion
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• v.11 no.4
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• pp.14-21
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• 2006

In this study, syngas which is reformed from fossil fuel and has hydrogen as a major component, was added to a gasoline engine to improve combustion stability and exhaust emissions of idle state. Syngas fraction of the total supplied fuel varied to 0 %, 25 %, 50 % with various ignition timing and excess air ratio. Combustion stability, exhaust emissions, fuel consumption and exhaust gas temperature were measured to investigate the effects of syngas addition on idle performance. Results showed that syngas has ability to widely extend lean operation limit and ignition retard range with dramatical reduction of engine out emissions. It is supposed that the usage of syngas in the internal combustion engine is an effective solution to meet the future strict emission regulations.

• Journal of the Korean Professional Engineers Association
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• v.32 no.6
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• pp.60-67
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• 1999

299 chemical analyses are used to study the characteristics of mineral and thermal waters in South Korea. Even though the concentration of chemical components in thermal waters are generally very low, mineral waters having components more than 1,000 ppm of dissolved total solid(TDS) are reached up to 19% total analyses data, In Germany, Japan or some other countries, mineral and thermal waters are detined not only by water temperature, but also by chemical components. The principle of Law in Japan in also almost same with the German regulations. However, the Law for thermal spring In Korea permit thermal water to be qualifiled only by water temperature. For including chemical characters into the regulations or Law of thermal spring, the limit values of TDS and other 9 micro components related to mineral and thermal waters was selected through this study.

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.3
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• pp.19-26
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• 2004

A prior fundamental study was executed using a constant volume chamber to improve the burning properties of lean pre-mixture by the injection of active radicals generated in the sub-chamber. In consequence, RI method shows remarkable progress in the aspects of burning velocity and combustible lean limit compared with SI method. In this study, the necessary additional works have been performed to be based on the former results. We changed parameters as the initial temperature and the initial pressure of mixture. And the effects of residual gas at issue in a real engine were investigated. As a result, the effects of initial temperature were significant, but on the other hand, those of initial pressure were slight. The correlation of passage hole number between overall passage hole area was grasped. And the more detailed analysis is required on residual gas.