• Journal of the Korean Electrochemical Society
• /
• v.11 no.4
• /
• pp.273-283
• /
• 2008

GDL(Gas Diffusion Layer) is one of the main components of PEM fuel cell. It transports reactants from the channel to the catalyst and removes reaction products from the catalyst to the channels in the flow filed plate. It is known that higher permeability of GDL can make it possible to enhance the gas transport through GDL, leading to better performance. And MEA's temperature is determined by gas and heat transport. In this paper, three dimensional numerical simulation of PEM fuel cell of parallel channel and serpentine channel by the permeability of GDL is presented to analysis heat and mass transfer characteristics using a FLUENT modified to include the electrochemical behavior. Results show that in the case of parallel channel, performance variation with change of permeability of GDL was not so much. This is thought because mass transfer is carried out by diffusion mechanism in parallel channel. Also, in the case of serpentine channel, higher GDL permeability resulted in better performance of PEM fuel cell because of convection flow though GDL. And mass transfer process is changed from convection to diffusion when the permeability becomes low.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.12 no.1
• /
• pp.167-174
• /
• 2008

Number of long-span bridge construction has been increased recently so that seismic consideration of design has become significant. To adapt such significance to design, seismic design in the newly revised 'Cable Steel Bridge Design Handbook' specifies some of wave travelling effect and local site effect. In this study, a cable-stayed bridge with main span of 500m is analysed having variables of uniform excitation, wave travelling effect, and wave travelling effect plus local site effect. Result shows that wave travelling effect in cable-stayed bridge affects considerably to its seismic response under weak soil condition even though the span length is relatively short. What's more, regardless of soil type, the seismic response has become higher for analysis with wave travelling effect and local site effect than with wave travelling effect only. Consequently, in seismic response analysis of long-span bridge, consideration should be given to application of wave travelling effect and local site effect.

• Journal of the Korean Society of Clothing and Textiles
• /
• v.23 no.6
• /
• pp.820-828
• /
• 1999

The purpose of this study was to investigate the changes of pore area and water vapour transport by the changes of moisture regain and fabric structure of wool fabrics, As specimens 4 worsted wool fabrics were used. The pore area were measured by image analysis method and dinamic vapour transport and water reisitance was determined by clothing-environment-body modelling system. The pore area was changed by the moisture regain of wool fabrics. The change of pore area was influenced by the yarn twist thread count and cover factor and the weave type. The water vapour transport was changed by the moisture regain. The change of water vapour transport was influenced by the change of pore aree which was determined by image analysis.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.24 no.5
• /
• pp.401-408
• /
• 2012

Volumetric mass transfer coefficient was measured with carbon dioxide and deionized water for the gas-liquid cocurrent slug flow in 2, 5 and 8 mm tubes. Measurement was repeated with and without a vertical section in an experimental setup and entrance effect was found greater for smaller tubes. Volumetric mass transfer coefficient in the vertical section was found generally a strong function of gas- and liquid-phase superficial velocities. 5 mm- and 8 mm-tube data are highly consistent each other but not with 2 mm tube.

• Journal of Power System Engineering
• /
• v.16 no.1
• /
• pp.78-83
• /
• 2012

The authors suggest the algorithm for the static analysis of a three dimensional solid structure by using the finite element-transfer stiffness coefficient method (FE-TSCM) and the hexahedral element of the finite element method (FEM). MATLAB codes were made by both FE-TSCM and FEM for the static analysis of three dimensional solid structure. They were applied to the static analyses of a very thick plate structure and a three dimensional solid structure. In this paper, as we compare the results of FE-TSCM with those of FEM, we confirm that FE-TSCM introducing the hexahedral element for the static analysis of a three dimensional solid structure is very effective from the viewpoint of the computational accuracy, speed, and storage.

• 한국신재생에너지학회:학술대회논문집
• /
• 2009.06a
• /
• pp.550-553
• /
• 2009

도로 환경 모니터링을 위한 센서 노드의 전력원으로 유도풍을 이용한 압전에너지 하베스팅 기술은 기존 재생 에너지의 설치 및 작동 조건에 영향을 받지 않고, 도로상에 주오염원인 자동차에서 발생되는 폐에너지를 활용하는 친환경적 에너지 순환시스템을 구현하는 핵심 요소이다. 차량 유도풍에 의해 발생되는 풍압으로 도로 상의 구조물에 진동을 유발한다. 이 때 발생한 진동 에너지는 압전체를 통해 전기 에너지로 변환, 저장할 수 있다. 이렇게 저장된 에너지는 센서의 구동과 무선 데이터 송수신을 위한 센서 노드의 전력원으로 사용함으로써 별도의 전력원이 필요없게 된다. 본 연구에서는 60km/h로 주행하는 한 대의 차량에 의해 2.7m/s의 유도풍이 발생하여 0.6g로 도로 상의 구조물에 에너지를 전달하게 된다. 전달된 에너지가 압전체를 통해 15uJ 전기에너지로 저장된다.

• Journal of KSNVE
• /
• v.6 no.4
• /
• pp.481-491
• /
• 1996

In this paper, we formulated algorithm for free vibration analysis of cylindrical shells with stiffeners by applying the transfer influence coefficient method. This was developed as a vibration analysis method suitable for using personal computer(PC). The simple computational results form PC demonstrated the validity of the present algorithm, that is, the computational high accuracy and speed, and the flexibility of programming. We compared with results of the transfer matrix method and the reference. We also confirmed that the present algorithm could provide the solutions of high accuracy for system with a lots of intermediate rigid supports and stiffeners. And all boundary conditions and the intermediate stiff supports between shell and foundation could be treated only by adequately varying the values of the spring constants.

• 한국해양학회지
• /
• v.23 no.3
• /
• pp.146-157
• /
• 1988

Properties of porosity, compressional wave velocity, velocity anisotropy, electrical resistivity, and resistivity anisotropy are measured and calculated for two DSDP clay-rich hemipelagic sequences in the northwestern Pacific. Velocity and resistivity increase with burial depth at the expense of decreasing porosity. Profiles of velocity anisotropy and resistivity anisotropy show almost the same trend. Horizontally developed low aspect ratio pores may generate velocity and resistivity anisotropy. The preferred orientation of clay minerals is also believed to be responsible for the observed anisotropy.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.12 no.9
• /
• pp.674-684
• /
• 2002

In order to decrease remarkably the computation time and storage used in the direct integration method without the loss of accuracy, authors suggest a new transient analysis algorithm. This algorithm is derived from the combination of three techniques, that is, the transfer technique of the transfer stiffness coefficient method, the modeling technique of the finite element method, and the numerical integration technique of the Newmark method. In this paper, the transient analysis algorithm of a frame structure is formulated by the proposed method. The accuracy and computation efficiency of the proposed method are demonstrated through the comparing with the computation results by the direct integration method for three computation models under various excitations.

• The Journal of the Acoustical Society of Korea
• /
• v.21 no.1
• /
• pp.73-81
• /
• 2002

The transmission of vibration energy through beam-plate junctions in vibration intensity analysis called power new analysis (PFA) has been studied. PFA is an analytic tool for the prediction of frequency averaged vibration response of built-up structures at medium to high frequency ranges. The power transmission and reflection coefficients between the semi-infinite beam and plate are estimated using the wave transmission approach. For the application of the power coefficients to practical complex structures, the numerical methods, such as finite element method are needed to be adapted to the power flow governing equation. To solve the discontinuity of energy density at the joint, joint matrix is developed using energy flow coupling relationships at the beam-plate joint. Using the joint matrix developed in this paper, an idealized ship stem part is modeled with finite element program, and vibration energy density and intensity are calculated.