• 한국전기전자재료학회논문지
• /
• 제25권6호
• /
• pp.467-473
• /
• 2012

A functionally graded material (FGM) spacer, which the distribution of dielectric permittivity inside an insulator changes spatially, can considerably reduce the electric field concentration around a high-voltage electrode and along the gas-insulator interface when compared to a conventional spacer with a uniform permittivity distribution. In this research, we propose the FGM spacer with an elliptical permittivity distribution instead of that with a distribution of dielectric permittivity varying along a radial direction only in order to improve efficiently the insulation capability. The optimal design of the elliptical FGM spacer configuration is performed by using the response surface methodology (RSM) combined with the steepest descent method (SDM).

• 한국경제지리학회지
• /
• 제5권1호
• /
• pp.5-24
• /
• 2002

본 연구는 경질제품의 유통구조와 물류체계를 공간적 관점에서 분석하였다. 석유제품은 정유사, 대리점, 주유소의 유통기관들을 통해서 공급되지만, 제품의 특성과 용도별로 상이한 유통경로를 갖고 있다. 석유제품의 수송은 정유공장에서 주요 소비지역에 입지하고 있는 저유소까지의 1차 수송과 주유소로부터 주유소나 중소수요처까지의 2차 수송으로 이루어진다. 1차 수송에는 유조선, 유조화차, 송유관, 유조차가 이용되고, 대리점이나 수송용역 업체가 담당하는 2차 수송은 대부분 유조차가 수송을 전담하고 있다. 본 논문에서는 SK와 LG 정유사의 저유소 분포와 저유소 유형별 공급권역을 분석하였다. 또한 하나의 저유소가 관할하는 공급권역내에 포함된 인구수와 자동차수, 주유소수를 도출하였고, 이를 바탕으로 하나의 주유소가 공급을 담당하는 최소요구치 수요인 인구수와 자동차수를 산출하였다.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1999년도 하계학술대회 논문집 E
• /
• pp.2274-2276
• /
• 1999

In this work, temperature rise and eddy current distribution on the enclosure and conductor of 3 pole gas insulated switchgear were investigated using analytical and experimental measures. The design of the diameters of the conductors and the enclosures of a meal clad gas insulated switchgear is primarily based on the insulation requirements. It is very difficult problem to predict the temperature rise of enclosed switchgear due to the complexity of the phenomena of heat transfer and existence of eddy current loss. To overcome this situations, we focused on the eddy current distribution on the enclosure of switchgear caused by high current 3 pole conductor as a fundamental basis. The experimental results about temperature distribution of 3 pole gas insulated switchgear were reported and measurements are compared with predictions of three-dimensional thermal model for eddy current analysis. As a result, three dimensional numerical analysis found to be in close relationship with experimental results and thermal model is efficient to predict the abnormal temperature rise in switchgear.

• 한국태양에너지학회 논문집
• /
• 제32권1호
• /
• pp.32-39
• /
• 2012

New and renewable energy systems(solar thermal system, photovoltaic system, geothermal system, wind power system) are environmentally friendly technologies and these in South Korea are very important measures to reduce greenhouse-gas(GHG) and to push ahead with Green Growth. The purpose of this paper is to analyze GHG mitigation potential by distribution of solar thermal system in housing sector with bottom-up model called 'Long-range Energy Alternative Planning system'. Business as usual(BAU) was based on energy consumption characteristic with the trend of social-economic prospects and the volume of housing. The total amount of GHG emission of BAU was expected to continuous increase from 66.0 million-ton $CO_{2e}$ in 2007 to 73.1 million-ton $CO_{2e}$ in 2030 because of the increase of energy consumption in housing. The alternative scenario, distribution of solar thermal system in housing sector had GHG mitigation potential 1.54 million-ton $CO_{2e}$ in 2030. The results of this study showed that new and renewable energy systems made a contribution of reducing the use of fossil fuel and the emission of greenhouse-gas in building.

• 대한금속재료학회지
• /
• 제46권10호
• /
• pp.662-671
• /
• 2008

The behavior of hydrogen in the steel making process was investigated. The relation between the composition of ladle slag and hydrogen concentration in molten steel was considered. The hydrogen distribution ratio between ladle slag and molten steel was increased with increasing basicity of the slag; it was about 20 when the basicity of slag was 15. Hydroxyl capacity measured from the hydrogen distribution ratio between slag and the molten steel was comparatively corresponding to the value of hydroxyl capacity measured by the equilibrium reaction of slag and $H_2O$ gas. However, it is considerably different from the value calculated by regular solution model. The influence of hydrogen on a sticking type breakout is considered. The effect of hydrogen and $H_2O$ gas on the crystallization behavior of mold powder was investigated by DHTT (Dual hot thermocouple technique). As a result, it was proved that mold powder could be crystallized by $H_2O$ gas in the atmosphere. Therefore, it is concluded that $H_2O$ gas in the atmosphere can be a possible cause of the sticking type breakout that occasionally occurs in the continuous casting process.

• 유통과학연구
• /
• 제16권4호
• /
• pp.83-88
• /
• 2018

Purpose - This study conducts an empirical analysis on gasoline pricing of Korean retail gas stations focusing on spatial effects. Unlike previous studies, the study uses an official land price for a proxy of the importance of location, and also allows the spatial effects from other competing gas stations as well. Research design, data, and methodology - In collection of data, we obtain more abundant data than those of previous studies. The gasoline prices used in the study are 909,084 observations as daily data from January 1 to July 31 of the year 2016. A proxy for the land price is collected by linking official public land price data with address information on each gas station. For the estimation, the study employs the Panel Spatial Dubin Model to make the best use of the collected location information. Results - As expected, spatial properties of gas stations have significant effects on the gasoline price. As the price per square meter increases by 100 thousands won, the price of gasoline rises 9 won per liter. Among other characteristics, the price increases by 16 won per liter if the station has a convenience store, and about 5 won if it has a car wash service. Gasoline price in Singapore accounted for 26% of variations in domestic gasoline prices. SK Energy and GS Caltex are the top brands in terms of price. The study also finds prices and other important properties of competing gas stations have significant effects on others' prices. Prices of competing gas station have a positive relationship with those of others. If a competing gas station raises the price, the gas station also raises the price, and lowering the price lower the price. Among brands, GS Caltex has the greatest downward pressure on nearby gas stations. Conclusions - The study confirms that location value of gas stations affect their gasoline prices, and the prices of the competing gas stations also have a significant effects on their prices. It suggests that the prices in the competing retail areas tend to be synchronized with each other.

• Journal of Electrical Engineering and Technology
• /
• 제13권4호
• /
• pp.1663-1672
• /
• 2018

In recent times, gas insulated medium voltage (MV) circuit breakers (CB) form a vital component in power system network, considering its advantages such as reduced size and safety margins. Gas insulation characteristics of circuit breakers are generally measured by lightning impulse (LI) test according to IEC standard 60060-1 as a factory routine test. Considering the environmental issues of $SF_6$ gas, many research works are being carried out towards the mixture of $SF_6$ gases for high voltage insulation applications. However, few reports are only available regarding the LI withstand and streamer propagation characteristics (at both positive and negative polarity of waveform) of $SF_6/N_2$ gas mixture insulated medium voltage circuit breakers. In this paper, positive and negative polarity LI tests are carried out on 22 kV medium voltage circuit breaker filled with $SF_6/N_2$ gas mixture at different gas pressures (1-5 bar) and at different gas mixture ratios. Important LI parameters such as breakdown voltage, streamer velocity, time to breakdown and acceleration voltage are evaluated with IEC standard LI ($1.2/50{\mu}s$) waveform. Weibull distribution analysis of LI breakdown voltage data is carried out and 50% probability breakdown voltage, scale parameter and shape parameter are evaluated. Results illustrate that the $25%SF_6+75%N_2$ gas filled insulation considerably enhances the LI withstand and breakdown strength of MV circuit breakers. LI breakdown voltage of circuit breaker under negative polarity shows higher value when compared with positive polarity. Results show that maintaining the gas pressure at 0.3 MPa (3 bar) with 10% $SF_6$ gas mixed with 90% $N_2$ will give optimum lighting impulse withstand performance of 22 kV MV circuit breaker.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2007년도 춘계학술대회B
• /
• pp.2038-2043
• /
• 2007

Analysis of the internal state of the blast furnace is needed to predict and control the operating condition. Especially, it is important to develop modeling of blast furnace for predicting cohesive zone because shape of cohesive zone influences on overall operating condition of blast furnace such as gas flow, temperature distribution and chemical reactions. Because many previous blast furnace models assumed cohesive zone to be fixed, they can't evaluate change of cohesive zone shape by operation condition such as PCR, blast condition and production rate. In this study, an axi-symmetric 2-dimensional steady state model is proposed to simulate blast furnace process using the general purpose-simulation code. And Porous media is assumed for the gas flow and the potential flow for the solid flow. Velocity, pressure and temperature distribution for gas and solid are displayed as the simulation results. The cohesive zones are figured in 3 different operating conditions.

• 한국전산유체공학회지
• /
• 제7권2호
• /
• pp.33-42
• /
• 2002

Numerical estimation for concentration of mono-carbon oxygen (CO) gas inside an underground parking lot with auxiliary jet fans for enhancement of ventilation is carried out by using a commercial program. Main interest lies on the diagnosis of the present ventilation system including position and selection of auxiliarly fans in addition to main suppliers and exhausts. Details of both flows and concentration of CO gas that is most important component among car exhaust gases are illustrated in this investigation and those are presented for engineering construction of an underground parking pool. Prediction data of computational work is also validated by real measurements of concentration of CO gas.

• 대한용접접합학회:학술대회논문집
• /
• 대한용접접합학회 2006년 추계학술발표대회 개요집
• /
• pp.29-31
• /
• 2006

Stainless steel sheets are widely used as the structural material for the railroad cars and the commercial vehicles. These kinds structures used stainless steel sheets are commonly fabricated by using the gas welding. For fatigue design of gas welded joints such as fillet and plug type joint, it is necessary to obtain design information on stress distribution at the weldment as well as fatigue strength of gas welded joints. And also, the influence of the geometrical parameters of gas welded joints on stress distribution and fatigue strength must be evaluated. the ${\Delta}P-N_f$ curves were obtained by fatigue tests. Using these results, ${\Delta}P-N_f$ curves were rearranged in the ${\sigma}-N_f$ relation with the maximum stress at the edge of fillet welded joint.