• Advances in Energy Research
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• 제4권4호
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• pp.275-284
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• 2016

In the present work, ZnO nanoparticles (NPs) have been dispersed alone in the same solvent of the active layer for improving performance parameters of the organic solar cells. Different concentrations of the ZnO NPs have been blended inside active layer of the solar cell based on poly(3-hexylthiophene) (P3HT), which forms the hole-transport network, and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM), which forms the electron-transport network. In the present investigations, the ZnO NPs may represent an efficient tool for improving light harvesting through light scattering inside active layer, electron mobility, and electron acceptance strength which tend to improve photocurrent and performance parameters of the investigated solar cell. The fill factor (FF) of the ZnO-doped solar cell increases nearly 14% compared to the non-doped solar cell when the doping is 50%. The present investigations show that ZnO NPs improve power conversion efficiency of the solar cell from 1.23% to 1.64% with increment around 25% that takes place after incorporation of 40% as a volume ratio of the ZnO NPs inside P3HT:PCBM active layer.

• Biomolecules & Therapeutics
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• 제4권2호
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• pp.148-153
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• 1996

Activation of the T lymphocytes results in a variety of early biochemical events ultimately leading to cell proliferation and lymphokine production. Stimulation of the signal transduction cascade in T cells through the T cell receptor coincides with activation of the phosphatidylinositol-phospholipase C (PI-PLC) pathway. Therefore, we have established a model system to screen immune-simulator that can increase the hydrolysis of phosphoinositides in human T cell leukemia Jurkat cells. As a result of screening from herbal medicine extract, 4 extracts (O1ibanum, Ephedrae Herba, Real Gar, Saussureae Radix) were found 14 increase the production of inositol phosphates. All the active fraction from the four kinds of extract were fluted in a different retention time on C-18 HPLC and these active fraction also showed difference in cell specificity. And all the active fractions increased DNA synthesis in T cell. Therefore, it is suggested that the active fraction among 4 extracts might contain a compound having different properties one another.

• 전기학회논문지
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• 제58권3호
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• pp.531-538
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• 2009

The paper deals with an operation scheme to improve the forecasting of output range and to regulate the active power output of the hybrid system consisting of a doubly fed induction generator (DFIG) and a fuel-cell. The power output of the wind turbine fluctuates as the wind speed varies and the slip power between the rotor circuit and power converter varies as the rotor speed change. The power fluctuation of a DFIG makes its operation difficult when a DFIG is connected to grid. A fuel cell system can be individually operated and adjusted output power, hence the wind turbine and fuel cell hybrid system can overcome power fluctuation by using a fuel-cell power control. In this paper, a fuel-cell is performed to regulate the active power output in comparison with the regulated active power output of a DFIG. And it also improves the forecasting of output range. Based on PSCAD/EMTDC tools, a DFIG and a proton exchange membrane fuel cell(PEMFC) is simulated and the dynamics of the output power in hybrid system are investigated.

• 대한기계학회논문집B
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• 제32권5호
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• pp.359-366
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• 2008

A two-dimensional thermal model of proton exchange membrane fuel cell with large active area is developed to investigate the performance of fuel cell with large active area over various thermal management conditions. The core sub-models of the two-dimensional thermal model are one-dimensional agglomerate structure electrochemical reaction model, one-dimensional water transport model, and a two-dimensional heat transfer model. Prior to carrying out the simulation, this study is contributed to set up the operating temperature of the fuel cell with large active area which is a maximum temperature inside the fuel cell considering durability of membrane electrolyte. The simulation results show that the operating temperature of the fuel cell and temperature distribution inside the fuel cell can affect significantly the total net power at extreme conditions. Results also show that the parasitic losses of balance of plant component should be precisely controlled to produce the maximum system power with minimum parasitic loss of thermal management system.

• 전력전자학회논문지
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• 제23권4호
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• pp.273-280
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• 2018

This paper proposes a zero-voltage-transition pulse-width modulation (PWM) DC-DC converter that uses a new active-snubber-cell. The converter main switch can be turned on and off with ZVS, while the snubber switch is turned on with ZCS and turned off with ZVS. Other semiconductor devices are operated under the soft-switching condition. Normal PWM control can be used, the proposed active-snubber-cell does not impose any additional voltage and current stresses. The active-snubber-cell is suitable for high-power applications due to its easy integration into interleaved converters. This paper discusses the operation of the converter, presents some design guidelines, and provides the results of an experiment with a 100 kHz and 1 kW prototype. A peak efficiency of 97.8% is recorded.

• Journal of Microbiology and Biotechnology
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• 제17권1호
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• pp.110-115
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• 2007

Electrochemically active bacteria were successfully enriched in an electrochemical cell using a positively poised working electrode. The positively poised working electrode (+0.7 V vs. Ag/AgCl) was used as an electron acceptor for enrichment and growth of electrochemically active bacteria. When activated sludge and synthetic wastewater were fed to the electrochemical cell, a gradual increase in amperometric current was observed. After a period of time in which the amperometric current was stabilized (generally 8 days), linear correlations between the amperometric signals from the electrochemical cell and added BOD (biochemical oxygen demand) concentrations were established. Cyclic voltammetry of the enriched electrode also showed prominent electrochemical activity. When the enriched electrodes were examined with electron microscopy and confocal scanning laser microscopy, a biofilm on the enriched electrode surface and bacterium-like particles were observed. These experimental results indicate that the electrochemical system in this study is a useful tool for the enrichment of an electrochemically active bacterial consortium and could be used as a novel microbial biosensor.

• Journal of Electrochemical Science and Technology
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• 제10권4호
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• pp.381-386
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• 2019

Zn-air battery uses oxygen from the air, and hence, air holes in it are kept open for cell operation. Therefore, loss of water by evaporation through the holes is inevitable. When the water is depleted, the battery ceases to operate. There are two water consumption routes in Zn-air batteries, namely, active path (electrolysis) and passive path (evaporation and corrosion). Water loss by the active path (electrolysis) is much faster than that by the passive path during the early stage of the cycles. The mass change by the active path slows after 10 h. In contrast, the passive path is largely constant, becoming the main mass loss path after 10 h. The active path contributes to two-thirds of the electrolyte consumption in 24 h of cell operation in 4.0 M KOH. Although water is an important component for the cell, water vapor does not influence the cell operation unless the water is nearly depleted. However, high oxygen concentration favors the discharge reaction at the cathode.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2009년도 춘계학술대회 논문집
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• pp.286-286
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• 2009

A small PEM fuel cell has two different stack configurations such as active and passive stacks. The active stack has a distintion of high power density although it makes system complex by using alr blower and related BOPs resulting in large system volume. On the contrary, passive stack has an advantage of compact system because it doesn't need air supplying devices although it reveals relatively low stack power density. In this study we fabricated two 10W PEMFC stacks with different stack configurations, active and passive stacks, and tested their performance and stability. The active stack consists of 13cells with an active area of $5cm^2$. The passive stack has 12cells with an active area of $16cm^2$. When we compared the stack performance of those stacks, the active stack showed higher power density compared to the passive stack, particularly at high voltage regions. However, at low voltage and high current regions, the passive stack performance was comparable to the active stack. The stack stability was largely dependent on the fuel humidity, particularly for active stack. At low humidity conditions, the active stack performance was decreased continuously and the cell voltage distribution was not uniform showing seriously low cell voltage at center cells mainly due to the cell drying. The passive stack showed relatively stable behavior at low humidity and the stack performance was largely dependent on the atmospheric conditions.

• 한국미생물학회:학술대회논문집
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• 한국미생물학회 2000년도 추계학술발표대회
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• pp.92-99
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• 2000

In this study biofuel cell is classified into 5 generation fuel cell system based on structural and structural difference. I optionally named the biofuel cell with electron mediators prototype, that with electrochemical active bacterium 2nd generation, that with modified electrode with NR 3rd generation, that with catalytic active electrode 4th generation, and that using air as a catholyte instead of ion selective membrane and cathode, respectively. The electricity production was compared among 5 types biofuel cell and was confirmed to be $50-100\%$ higher in 4th and 5th generation than in 1st to 3rd generation.

• 전력전자학회논문지
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• 제24권4호
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• pp.279-285
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• 2019

This study proposes an enhanced switching pattern that can improve energy transfer efficiency in an active cell-balancing circuit using a multiwinding transformer. This balancing circuit performs cell balancing by transferring energy stored in a specific cell with high energy to another cell containing low energy through a multiwinding transformer. The circuit operates in flyback and buck-boost modes in accordance with the energy transfer path. In the conventional flyback mode, the leakage inductance of the transformer and the stray inductance component of winding can transfer energy to an undesired path during the balancing operation. This case results in cell imbalance during the cell-balancing process, which reduces the energy transfer efficiency. An enhanced switching pattern that can effectively perform cell balancing by minimizing the amount of energy transferred to the nontarget cells due to the leakage inductance components in the flyback mode is proposed. Energy transfer efficiency and balancing speed can be significantly improved using the proposed switching pattern compared with that using the conventional switching pattern. The performance improvements are verified by experiments using a 1 W prototype cell-balancing circuit.