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Ha, Taehun,Kim, Sangdae,Lee, Sungho Council on Tall Building and Urban Habitat Korea 2017 International journal of high-rise buildings Vol.6 No.1
High-rise buildings move during construction due to time-dependent material properties of concrete (creep and shrinkage), construction sequences, and structural shapes. The building movements, including vertical and horizontal displacements, result from the sum of axial and lateral deformation of vertical members at each level. In addition to the vertical shortenings, the lateral movement induced by differential shortening can have adverse effects on the construction tolerance and serviceability of non-structural elements such as elevators and curtain walls. In this study a construction stage analysis method is developed to predict lateral movement induced by shortening, including the effect of creep and shrinkage. The algorithm of construction stage analysis is combined with the FE analysis program. It is then applied to predict lateral movement of a 58-story reinforced concrete building that was constructed in Kuala Lumpur, Malaysia. Gravity induced lateral movement of this building is predicted by the construction stage analysis. A field three-dimensional laser scanning survey is carried out to verify the prediction results, and satisfactory agreement is obtained.
Investigation on the liquid water droplet instability in a simulated flow channel of PEM fuel cell
Ha Taehun,Kim Bokyung,김한상,민경덕 대한기계학회 2008 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.22 No.5
To investigate the characteristics of water droplets on the gas diffusion layer from both top-view and side-view of the flow channel, a rig test apparatus was designed and fabricated with prism attached plate. This experimental device was used to simulate the growth of a single liquid water droplet and its transport process with various air flow velocity and channel height. Not only dry condition but also fully humidified condition was also simulated by using a water absorbing sponge. The detachment height of the water droplet with dry and wet conditions was measured and analyzed. It was found that the droplet tends towards becoming unstable by decreased channel height, increased flow velocity or making a gas diffusion layer (GDL) dryer. Also, peculiar behavior of the water droplet in the channel was presented like attachment to hydrophilic wall or sudden breaking of droplet in case of fully hydrated condition. The simplified force balance model matches with experimental data as well.
DEVELOPMENT OF DRIVER FUEL ECONOMY INDEX FOR REAL ROAD FUEL ECONOMY
Taehun Ha,Seonwoo Choi,Yoonwoo Lee,최회명 한국자동차공학회 2019 International journal of automotive technology Vol.20 No.3
Although a 5-cycle testing was adopted to address the gap between the reported fuel economy from certification tests and fuel economy during real-world driving, the gap still remains and is difficult to be resolved without the consideration of the fuel consumption influencing parameters such as driver’s behavior, driving pattern and road condition. In this study, two types of driver fuel economy indices, the MAW (Moving Average Window) Power Ratio Index and the Constant Driving Index are newly defined to invent the index which can reflect the real-road conditions and simulate the realworld fuel economy. Both indices are defined as the ratio of actual driving to ideal (constant speed) driving in common but the former is based on the engine output and the latter is based on the work. Two types of indices are verified with 5-cycle testing results on chassis dynamometer. According to the verification, the MAW Power Ratio Index with window size of 60 seconds shows the highest correlation with the certified fuel economy and is the reasonable starting point of index for reflecting the real-road conditions.
고분자전해질형 연료전지용 막 가습기의 가습 성능 실험 및 모델링
하태훈(Taehun Ha),김한상(Han-Sang Kim),민경덕(Kyoungdoug Min) 한국자동차공학회 2006 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
Proper humidification of supplied air and hydrogen is one of the key issues for PEM fuel cell performance or efficiency. Although water is generated by electrochemical reaction at the cathode side in the fuel cell, external humidification of supplied air along the operating conditions is needed to humidify the MEA sufficiently. Membrane humidifier is well known as the steadiest and the most efficient for external humidification. In this study, membrane humidifier using the liquid water to humidify dry air was studied. However, appropriate operating condition of membrane humidifier is highly required for desirable humidification performance. Therefore, first, operating temperature, air flow rate, water flow rate were chosen as the operating parameters and the experiments of those operating conditions were carried out. Secondly, the membrane humidifier was simulated in commercial program named as COMSOL. Humidification performance of membrane humidifier by calculation compared with experimental results.
Experimental Study on Carbon Corrosion of Gas Diffusion Layer in PEM Fuel Cell
하태훈(Ha, Taehun),조준현(Cho, Junhyun),박재만(Park, Jaeman),민경덕(Min, Kyoungdoug),이은숙(Lee, Eunsook),정지영(Jyoung, Jy-Young) 한국신재생에너지학회 2010 한국신재생에너지학회 학술대회논문집 Vol.2010 No.11
Recently, many efforts to solve the durability problem of PEM fuel cell are carried on constantly. However, despite this attention, durability researches of gas diffusion layer (GDL) are not much reported yet. Generally, GDL of PEM fuel cell experiences three external attacks, which are dissolution of water, erosion of gas flow, corrosion of electric potential. In this study, among these degradation factors, carbon corrosion of electric potential was focused and investigated with accelerated carbon corrosion test. Through the test, it is confirmed that carbon corrosion occurred at GDL, and corroded GDL decreased a performance of operating fuel cell. The property changes of GDL were measured with various methods such as air permeability meter, pore distribution analyzer, thermo gravimetric analyzer, and tensile stress test to discover the effects of carbon corrosion. Carbon corrosion caused not only loss of weight and thickness, but also degradation of mechanical strength of GDL. In addition, to analysis the reason of GDL property changes, a surface and a cross section of GDL were observed with scanning electron microscope. After 100 hours test, the GDL showed serious damage in center of layer.
GC를 이용한 고분자전해질형 연료전지의 공기극 채널 내 산소 농도 분포에 관한 실험적 연구
하태훈(Ha, Taehun),김한상(Kim, Han-Sang),민경덕(Min, Kyoungdoug) 한국신재생에너지학회 2005 한국신재생에너지학회 학술대회논문집 Vol.2005 No.06
Fuel cell has been well known as a clean alternative power for vehicles. Recently, an experimental technique has been developed measurement of species and distributions by using gas chromatograph. In this study, cathode channel oxygen distributions as various conditions were investigated using gas chromatograph and cell visualization. And discussed relation between flooding and oxygen concentrations. As a result of experiment, oxygen consumpt ion is affected wi th flooding. Flooding is observed in channel near hydrogen inlet, and oxygen consumption is low at that region.