• 한국신재생에너지학회:학술대회논문집
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• 2011.11a
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• pp.89.2-89.2
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• 2011

In automotive applicatons or water vehicles, the polymer electrolyte membrane fuel cell(PEMFC) stack is keep moving while their operation. Especially the inclination environment can take a effect to fuel cell stack perfromance, because this condition can cause a bad effect to water exhaust of fuel cell stack. In this study, a large scale stack(over 100kW power) is inclined upto 30 degree in lengthwise and crosswise using stack lift equipment. And the stack is operated in 10~100% load. No significant change has appeared in crosswise inclined condition and lenthwise low angle. But in lenthwise large angle tilting condition, the fuel cell performance has significantly decreased. And this performance decrease is aggravated in low load. An active water exhaust device is applied to the stack to prevent the performance decrease. And in lenthwise large angle tilting condition, this device cause a good effect to fuel cell stack performance.

• Proceedings of the Korea Information Processing Society Conference
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• 2020.11a
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• pp.866-869
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• 2020

소프트웨어 개발 환경이 빠르게 변화함에 따라 시스템의 복잡성이 증가하고 있다. 이에 따라 크고 작은 소프트웨어의 버그를 피할 수 없게 되며 이를 효율적으로 처리하기 위해 Bug report 를 사용한다. 하지만, Bug report 에서 개발자가 해당 Bug report 의 우선순위를 결정하는 과정은 노력과 비용 그리고 시간을 많이 소모하게 만든다. 따라서, 본 논문에서는 Bug report 내의 Stack trace 를 기반으로 Bug 의 우선순위를 자동적으로 추천하는 기법을 제안한다. 이를 위해 본 연구에서는 첫 번째로 Bug report 로부터 Stack trace 를 추출하였으며 Stack trace 의 3 가지 요소(Exception, Reason 그리고 Stack frame)에 TF-IDF, Word2Vec 그리고 Stack overflow 를 사용하여 특징 벡터를 정의하였다. 그리고 Bug 의 우선순위 추천 모델을 생성하기 위해 4 가지의 Classification 알고리즘을(Random Forest, Decision Tree, XGBoost, SVM)을 적용하였다. 평가에서는 266,292 개의 JDK library 의 Bug report 데이터를 수집하였고 그중 Stack trace 를 가진 Bug report 로부터 68%의 정확도를 산출하였다.

• Transactions of the Korean hydrogen and new energy society
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• v.34 no.5
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• pp.465-477
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• 2023

In proton exchange membrane fuel cell (PEMFC), proper thermal management of the stack and moisture generation by electrochemical reactions significantly affect fuel cell performance. In this study, the PEMFC dynamic characteristic model was developed through Simcenter AMESim, a development program. In addition, the developed model aims to understand the thermal resin balance of the stack and performance characteristics for input loads. The developed model applies the thermal management model of the stack and the moisture content and permeability model to simulate voltage loss and stack thermal behavior precisely. This study extended the C based AMESet (adaptive modeling environment submodeling tool) to simulate electrochemical reactions inside the stack. Fuel cell model of AMESet was liberalized with AMESim and then integrated with the balance of plant (BOP) model and analyzed. And It is intended to be used in component design through BOP analysis. The resistance loss of the stack and thermal behavior characteristics were predicted, and the impact of stack performance and efficiency was evaluated.

• Asian Journal of Atmospheric Environment
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• v.2 no.1
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• pp.1-13
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• 2008

A numerical simulation method has been developed to predict atmospheric flow and stack gas diffusion using a calculation domain of several km around a stack under complex terrain conditions containing buildings. The turbulence closure technique using a modified k-$\varepsilon$-type model under a non hydrostatic assumption was used for the flow calculation, and some of the calculation grids near the ground were treated as buildings using a terrain-following coordinate system. Stack gas diffusion was predicted using the Lagrangian particle model, that is, the stack gas was represented by the trajectories of released particles. The numerical model was applied separately to the flow and stack gas diffusion around a cubical building and to a two-dimensional ridge in this study, before being applied to an actual terrain containing buildings in our next study. The calculated flow and stack gas diffusion results were compared with those obtained by wind tunnel experiments, and the features of flow and stack gas diffusion, such as the increase in turbulent kinetic energy and the plume spreads of the stack gas behind the building and ridge, were reproduced by both calculations and wind tunnel experiments. Furthermore, the calculated profiles of the mean velocity, turbulent kinetic energy and concentration of the stack gas around the cubical building and the ridge showed good agreement with those of wind tunnel experiments.

• Journal of IKEEE
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• v.20 no.3
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• pp.299-302
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• 2016

In this paper, we designed the stack monitoring system with improved performance. To block the incoming pulse noise to the amplifier, shield and the power supply impedance are reduced and the power circuit is isolated. The control unit is developed with variable high voltage, adaptive gain, offset and threshold in order to match the scintillation detector characteristic to the apparatus. 300-1500V variable high voltage power circuit is configured applicable to various scintillation detector. Stack monitoring system with improved performance guarantee the efficiency and the reliability by considering the characteristic of various scintillation detector. Developed stack monitoring system is evaluated with certified testing equipment and shows excellent performance with respect to the uncertainty of the sensor test results.

• International Journal of Air-Conditioning and Refrigeration
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• v.11 no.2
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• pp.91-103
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• 2003

The objective of this study is to analyze and evaluate the impact of the stack effect in high-rise buildings for solving the various problems resulting from it. For the evaluation of the impacts on the stack effect, computer program simulations based on the network model were performed for a typical high-rise office building. The results of the simulations show that the impact caused by the stack effect is mainly dependent on building envelope air-tightness and internal air flow resistance. Therefore the problems due to the stack effect may be solved to some extent by installing vestibules around entrance doors and doors serving elevators, and by zoning the elevators.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 2008.11a
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• pp.235-238
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• 2008

High-rise buildings with stack effect caused by the foreclosure, which significantly delayed the spread of a fire in effects of these stack effect driving force said. In this research on the stack effect of the lobby if the pressurization of the stairwell analysis of the pressure distribution of the CONTAMW. Overall, the pressurization of the lobby makes it stairwell amount of pressure(+) to the zone in pressure designed to prevent the spread of smoke control performance and found that, the way a normal state and sub-pressurization in the stairwell with stack effect of the turbulence Such as the formation of the upper flow, but, in the upper atmosphere with pressurization was formed by the underlying trend.

• Journal of Advanced Marine Engineering and Technology
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• v.35 no.7
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• pp.881-890
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• 2011

Analyses of performance and behavior of the individual PEM fuel cells (PEMFC) under different operating conditions are of importance optimally to design and efficiently to operate the stack. The paper focuses on experimental analyses of a two-cell stack under different operating conditions, which performance and behavior are measured by the voltage of a cell as well as the stack. Experimental parameters include stoichiometric ratio, temperature of the air supplied under different working stack temperatures and loads. Results showed that the cell voltages are dominantly influenced by the temperature of the air supplied among others. In addition, an inherent difference between the first and the second cell voltage exists because of the tolerances of the cell components and the resulting different over-potentials at different equilibrium states. Furthermore, it is shown that the proton conductivity in the membranes conditioned by the humidity in the cathode channel highly affects the voltage differences of the two cells.

• 한국신재생에너지학회:학술대회논문집
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• 2007.06a
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• pp.553-556
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• 2007

Hyundai${\cdot}$Kia Motors have developed PEMFC stack technologies for passenger car application in 1998. The developed 80kW class stack, which was installed Kia's Sportage FCV in 2005, has been modified for -10$^{\circ}C$ cold start-up and ensuring the stability and durability by using new technologies such as newly designed separator, manifold block, end plate, and so on. And also, the stack durability has been verified over 1,500hrs with the condition of combined vehicle driving mode. Hyundai${\cdot}$Kia Motors will keep continuing the stack R&D to reach the goal of FCV commercialization.

• KIEAE Journal
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• v.10 no.3
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• pp.97-102
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• 2010

With the building is higher and higher, the stack effect is more and more remarkable. The stack effect accompanies many problems in high-rise building such as draft, troublesome in door opening, uncomfortable noise, contaminants dispersion, etc. In this study, the air movement and accompanied contaminants dispersion by stack effect in high-rise building, and diluting the contaminants concentration were analyzed. The analysis was performed for high-rise residential building in Seoul, Korea and the network simulation method was used. The results show that the indoor contaminants concentration and air movement caused by stack effect have interdependent relationship.