• Applied Science and Convergence Technology
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• 제23권4호
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• pp.179-186
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• 2014

Fluid model based numerical simulation was carried out for an inductively coupled plasma assisted sputter deposition system. Power absorption, electron temperature and density distribution was modeled with drift diffusion approximation. Effect of an electrically conducting substrate was analyzed and showed confined plasma below the substrate. Part of the plasma was leaked around the substrate edge. Comparison between the quasi-neutrality based compact model and Poisson equation resolved model showed more broadened profile in inductively coupled plasma power absorption than quasi-neutrality case, but very similar Ar ion number density profile. Electric potential was calculated to be in the range of 50 V between a Cr rod source and a conductive substrate. A new model including Cr sputtering by Ar+was developed and used in simulating Cr deposition process. Cr was modeled to be ionized by direct electron impact and showed narrower distribution than Ar ions.

• International Journal of Fluid Machinery and Systems
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• 제8권2호
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• pp.113-123
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• 2015

The efficiency of the ventilation system is a key point for durable and reliable electric generators. The design of such system requires a detailed understanding of the air flow in the generator. Computational fluid dynamics (CFD) has the potential to resolve the lack of information in this field. The present work analyses the air flow inside a generator model. The model is designed using a CFD-based approach, and manufactured by taking into consideration the experimental and numerical requirements and limitations. The emphasis is on the possibility to accurately predict and experimentally measure the flow distribution inside the stator channels. A major part of the work is focused on the design of an intake and a fan that gives an evenly distributed flow with a high flow rate. The intake also serves as an accurate flowmeter. Experimental results are presented, of the total volume flow rate, the total pressure and velocity distributions. Steady-state CFD simulations are performed using the FOAM-extend CFD toolbox. The simulations are based on the multiple rotating reference frames method. The results from the frozen rotor and mixing plane rotor-stator coupling approaches are compared. It is shown that the fan design provides a sufficient flow rate for the stator channels, which is not the case without the fan or with a previous fan design. The detailed experimental and numerical results show an excellent agreement, proving that the results reliable.

• 소성∙가공
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• 제24권3호
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• pp.187-193
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• 2015

The objective of the current study is to determine cross-sectional profile of intermediate dies in order to improve the plastic strain homogeneity which directly affects not only the dimensional accuracy but also the mechanical properties of final product by redesigning the intermediate dies using the conventional electric field analysis (EFA) method. Initially, the multi-pass shape wire drawing was designed by using the equivalent potential lines from EFA. The area reduction ratio was calculated from the number of passes in multi-pass shape wire drawing but constrained by the capacity of the drawing machine and the drawing force. In order to compensate for a concentration of strain in a region of the cross section of the wire, the process for multi pass wire drawing from initial round material to an intermediate die was redesigned again using the electric field analysis. Both drawing process designs were simulated by the finite element method in which the strain distribution and standard deviation plastic strain of the cross section of drawn wires were examined.

• 국제학술발표논문집
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• The 9th International Conference on Construction Engineering and Project Management
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• pp.937-944
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• 2022

Electric vehicles (EVs) have been growing to reduce energy consumption and greenhouse gas (GHG) emissions in the transportation sector. The increasing number of EVs requires adequate recharging infrastructure, and at the same time, adopts low- or zero-emission electricity production because the GHG emissions are highly dependent on primary sources of electricity production. Although previous research has studied solar photovoltaic (PV) -integrated EV charging stations, it is challenging to optimize spatial areas between where the charging stations are required and where the renewable energy sources (i.e., solar photovoltaic (PV)) are accessible. Therefore, the primary objective of this research is to support decisions of siting EV charging stations using a spatial data clustering method integrated with Geographic Information System (GIS). This research explores spatial relationships of PV power outputs (i.e., supply) and traffic flow (i.e., demand) and tests a community in the state of Indiana, USA for optimal sitting of EV charging stations. Under the assumption that EV charging stations should be placed where the potential electricity production and traffic flow are high to match supply and demand, this research identified three areas for installing EV charging stations powered by rooftop PV in the study area. The proposed strategies will drive the transition of existing energy infrastructure into decentralized power systems. This research will ultimately contribute to enhancing economic efficiency and environmental sustainability by enabling significant reductions in electricity distribution loss and GHG emissions driven by transportation energy.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2006년도 춘계학술대회 논문집
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• pp.82-85
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• 2006

With the fast growing number of skyscrapers and large ultrahigh apartment complexes, the concerns on fire caused by electricity also grow. Among about 30,000 fires recorded annually, roughly one third of them are hewn to be caused by electricity. If one of such high and densely populated buildings or apartments catches a fire, the consequence can potentially be quite catastrophic. However, with the rapid development of the techniques in the fields of communications and computers, electric power distribution systems for such buildings and apartments have been largely digitalized in recent years. More detailed informations on the operating status are now available, which enables more sophisticated monitoring and early detection of potential fire caused by electricity. In this paper, we present an inference technique that can be used as one of the basic techniques in building intelligent distribution panel systems that can effectively monitor, prevent and detect the occurrence of fire caused by electricity. The technique can accommodate production rules in linguistic expressions on high abstraction levels. Fire finding strategies can be easily modified to provide more effective countermeasures. Simulation results show that inference capabilities and thus the capability of fire monitoring in power distribution panel systems can be significantly enhanced with our approach.

• 마이크로전자및패키징학회지
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• 제30권1호
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• pp.71-78
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• 2023

외부로부터 전원이 인가되지 않은 바이폴라 전극의 정량적 고찰을 통해 도금 두께 산포 개선의 가능성을 살펴보고자 하였다. 헐셀은 양극에 대해 기울어진 음극을 가짐으로써, 음극의 각 영역에서 양극에 대한 경로차에 의한 iR drop의 차이로 음극 근처의 전해액에서는 전위 분포가 다르게 되어 한눈에 다양한 반응 과전압에서의 전기화학적 반응성을 평가할 수 있다. 본 연구는 이러한 헐셀의 불균일한 전위분포에 대해 보조 양극이 있는 경우에 바이폴라 특성을 관찰하고자 하였다. 특히 이러한 바이폴라 특성을 활용하여 음극의 불균일 두께 산포를 개선할 수 있는 가능성을 평가하기 위해, 실험 및 시뮬레이션을 통해 검증하였으며, 이를 통해 바이폴라가 형성된 주변의 전위 및 전류밀도 분포를 분석해 보았다. 10 mA/cm² 전류밀도로 75분동안 도금을 진행하여, 평균 두께가 약 16 ㎛로 도금을 진행하였다. 보조 양극을 사용하지 않은 일반 헐셀에서는 두께의 표준 편차가 10 ㎛인 반면에 보조 양극을 사용한 경우에는 3.5 ㎛로 나타났다. 시뮬레이션 계산에서도 8.9 ㎛와 3.3 ㎛로 나타났으며, 비교적 실험결과와 시뮬레이션 결과의 정합성이 높은 것으로 나타났다. 이러한 보조 양극을 통해 외부에서 전원 인가를 하지 않더라도 바이폴라 현상에 의해 두께 산포가 개선될 수 있음을알 수 있었다.

• Geomechanics and Engineering
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• 제2권3호
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• pp.191-202
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• 2010

The porosity (including the specific surface area and pore volume-diameter distribution) of montmorillonitic soft rock (MSR) was studied experimentally with an electrochemical treatment, based on which the change in porosity was further analyzed from the perspective of its electrokinetic potential (${\zeta}$ potential) and the isoelectric point of the electric double layer on the surface of the soft rock particles. The variation between the ${\zeta}$ potential and porosity was summarized, and used to demonstrate that the properties of softening, degradation in water, swelling, and disintegration of MSR can be modified by electrochemical treatment. The following conclusions were drawn. The specific surface area and total pore volume decreased, whereas the average pore diameter increased after electrochemical modification. The reduction in the specific surface area indicates a reduction in the dispersibility and swelling-shrinking of the clay minerals. After modification, the ${\zeta}$ potential of the soft rock was positive in the anodic zone, there was no isoelectric point, and the rock had lost its properties of softening, degradation in water, swelling, and disintegration. The ${\zeta}$ potential increased in the intermediate and cathodic zones, the isoelectric point was reduced or unchanged, and the rock properties are reduced. When the ${\zeta}$ potential is increased, the specific surface area and the total pore volume were reduced according to the negative exponent law, and the average pore diameter increased according to the exponent law.

• Journal of Microbiology and Biotechnology
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• 제15권6호
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• pp.1221-1228
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• 2005

Carbon electrode was applied to a wastewater treatment system as biofilm media. The spatial distribution of heterotrophic bacteria in aerobic wastewater biofilm grown on carbon electrode was investigated by scanning electron microscopy, atomic force microscopy, and biomass measurement. Five volts of electric oxidation and reduction potential were charged to the carbon anode and cathode of the bioelectrochemical system, respectively, but were not charged to electrodes of a conventional system. To correlate the biofilm architecture of bacterial populations with their activity, the bacterial treatment efficiency of organic carbons was measured in the bioelectrochemical system and compared with that in the conventional system. In the SEM image, the biofilm on the anodic medium of the bioelectrochemical system looked intact and active; however, that on the carbon medium of the conventional system appeared to be shrinking or damaging. In the AFM image, the thickness of biofilm formed on the carbon medium was about two times of those on the anodic medium. The bacterial treatment efficiency of organic carbons in the bioelectrochemical system was about 1.5 times higher than that in the conventional system. Some denitrifying bacteria can metabolically oxidize $H_{2}$, coupled to reduction of $NO_{3}^{-}\;to\;N_{2}$. $H_{2}$ was produced from the cathode in the bioelectrochemical system by electrolysis of water but was not so in the conventional system. The denitrification efficiency was less than $22\%$ in the conventional system and more than $77\%$ in the bioelectrochemical system. From these results, we found that the electrochemical coupling reactions between aerobic and anaerobic reactors may be a useful tool for improvement of wastewater treatment and denitrification efficiency, without special manipulations such as bacterial growth condition control, C/N ratio (the ratio of carbon to nitrogen) control, MLSS returning, or biofilm refreshing.

• 에너지공학
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• 제20권1호
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• pp.1-7
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• 2011

전기자동차(Electric Vehicle, EV)와 하이브리드 전기자동차(Hybrid Electric Vehicle, HEV)의 성능과 수명주기 비용은 배터리 팩에 좌우된다. 팩 내부의 비정상적인 온도분포는 전지간의 전기적인 불균형을 가져오고 팩의 성능을 떨어뜨리기 때문에 팩 내부의 온도 균일성은 EV와 HEV용 전지 팩의 최적 성능을 위한 중요한 요소이다. 본 연구에서는 EV와 HEV용 리튬이온전지 팩의 열적 거동을 예측하기 위해 삼차원 전산 모사를 하였다. 전지 팩의 열전도도는 각종 구성요소의 열전도 저항이 직렬과 병렬로 연결되어 있는 것으로 간주하였다. 셀에서의 열 발생량은 전지내부의 전기화학적 반응에 의한 반응열과 전류의 흐름과 내부저항에 의한 열을 고려하여 계산 하였다.

• 자원ㆍ환경경제연구
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• 제33권1호
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• pp.33-57
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• 2024

본 연구는 전기 소형화물차에 대한 구매보조금이 환경편익의 측면과 총보유비용 동등성 측면에서 볼 때 적정한 수준인지에 대하여 분석하였다. 환경편익에 대해서는 발전믹스에 따라 발생하는 환경오염물질 배출량을 고려하였으며, 기온분포에 따른 전기차의 효율변화도 반영하였다. 소형화물차의 경우, 경유차 대신 전기차를 운행함에 따른 환경편익은 차량의 총운행기간에 걸쳐 217~530만 원 수준으로 추정되었다. 또한, 현행 구매보조금 제도하에서 경유차 대비 전기차의 총보유비용은 사업용은 약 360만 원, 비사업용은 약 660만 원 낮은 것으로 추산되었다. 즉, 환경편익의 관점에서든 총보유비용의 관점에서든 보다 효율적으로 재정을 활용하고자 한다면 같은 예산이라도 전기 소형화물차에 대한 구매보조금 단가를 낮추는 것이 합리적이다. 그 대신 남은 예산은 화물차 전용 충전기의 확보와 같이 충전인프라를 고도화하는 데에 좀 더 집중한다면 잠재적인 구매자들의 금전적인 부담뿐만 아니라 충전 관련 불편함까지 줄여 전기 소형화물차 보급에 더 비용효과적일 것으로 판단된다.