• Proceedings of the KIPE Conference
• /
• 2003.11a
• /
• pp.17-20
• /
• 2003

This paper presents a high frequency (HF) link current-fed inverter fur fuel cell applications. The circuit topology, operation and control method of the proposed HF link current-fed inverter are presented. The active cancellation technique of the 120Hz input harmonic current is also considered. The simulation results are provided to show the feasibility of the proposed inverter scheme.

• Corrosion Science and Technology
• /
• v.11 no.6
• /
• pp.247-256
• /
• 2012

Harmonic current was measured for a dummy cell with various values of resistance, and the procedure developed through the measurements was applied to the investigation of effects of the amplitude of applied frequency and applied potential on the harmonic current of a stainless steel and a carbon steel in chloride containing solutions. From the measurements of harmonic current in the dummy cell, the optimum values of applied frequency and applied potential in harmonic current measurements were found to be 1 mHz and 20 mV (or lower), respectively. Increase in harmonic current with applied frequency was observed in the case where the level of harmonic current is low as in a stainless steel. Decrease in polarization resistance was also noted in this corrosion system with either increasing applied frequency or decreasing applied potential. However, no obvious effects of applied frequency was observed on harmonic current and polarization resistance in a carbon steel in which the level of harmonic current is high.

• Current Photovoltaic Research
• /
• v.1 no.1
• /
• pp.11-16
• /
• 2013

The current solar cell industry is experiencing a temporary plateau due to a sluggish economy and oversupply. It is expected that the solar industry can see similar growth to that of the recent past by overcoming the current situation, as there is growing demand globally for solar energy. The current situation led to restructuring of the world's solar industry, and domestic firms will need to have competitiveness through strategic approaches and proprietary technology to survive in the global solar market. Crystalline and amorphous silicon based solar cells have led the solar industry and occupied half or more of the market thus far. They will do so in the future PV market as well by playing a pivotal role in the solar industry. In this paper, the current status and prospects of silicon based solar cells, from materials to comprehensive and high efficiency technology that can emerge in the future, are discussed.

• Current Photovoltaic Research
• /
• v.4 no.1
• /
• pp.1-7
• /
• 2016

Among the various types of solar cells, silicon based two terminal tandem solar cell is one of the most popular one. It is designed to split the absorption of incident AM1.5 solar radiation among two of its component cells, thereby widening the wavelength range of external quantum efficiency (EQE) spectra of the device, in comparison to that of a single junction solar cell. In order to improve the EQE spectra further and raise short circuit current density ($J_{sc}$) an optimization of the tradeoff between the top and bottom cell is needed. In an optimized cell structure, the $J_{sc}$ and hence efficiency of the device can further be enhanced with the help of light trapping scheme. This can be achieved by texturing front and back surface as well as a back reflector of the device. In this brief review we highlight the development of light trapping in the silicon based tandem solar cell.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2003.05a
• /
• pp.985-990
• /
• 2003

In order to demonstrate Advanced Spent Fuel Conditioning Process (ACP), shielding facilities such as hot cell suitable to handling radionuclides and process property will be necessary. But the construction of new facilities needs much money, man-power and time, it is now scheduled to remodel the hot cell, which has already been installed and maintained at Irradiated Material Experiment Facility (IMEF) in the Korea Atomic Energy Research Institute (KAERI). The basic structure and concrete shield wall of hot cell partly have been constructed on the base floor in IMEF building in current status. And hot cell after remodeling will be used for carrying out the lab-scale experiment of ACP. The hot cell was built in accordance with 35 curies of fe-59(1.2 MeV) as design criteria of radiation dose limit. But the radioactive source of ACP is expected to be much higher than design criteria of IMEF, shielding ability of the hot cell in the current status is unsatisfactory to the hot test of ACP. Therefore shield wall shall be reinforced with heavy concrete, steel or lead. In this paper, dose rates are calculated according to ACP source, shielding materials, etc., and reinforcement structures are determined considering the current situation of hot cells, installation of shield windows and the easiness of work.

• Korean Journal of Veterinary Research
• /
• v.32 no.2
• /
• pp.157-164
• /
• 1992

Changes in the both inward current and conductance of membrane by the fertilization were observed using the one microelectrode voltage clamp(or switch clamp) technique. Unfertilized eggs and both 1- and 2-cell stage eggs after fertilization were donated from the superovulated mouse (ICR, more than 6 weeks old) treated with PMSG(pregnant mare serum gonadotropin, Sigma) and HCG(human chorionic gonadotropin, Sigma) and naturally mated ones, respectively in this experiment. Membrane potential was held at -90mV and the voltage step was applied from -80mV to 50mV with interval of 10mV or 20mV for 300ms. since both of amplitudes and time courses in the membrane currents were various according to the states of cells and clamping condition, results were presented by their $averages{\pm}SEM$(standard mean error)and ratios or percentages. Inward currents began to appear in response to the step depolarization from -60mV and reached its maximum at -50mV. However, since the potential was not clamped evenly during the voltage step, current-voltage(I-V) relationship might be positively shifted 10 or 20mV. From the steady-state currents plotted in the I-V curve, outward rectification was markedly observed. Peak inward currents$(i_{in})$ at -50mV were $-0.62{\pm}0.23nA$(n=4),$-0.52{\pm}0.25nA$(n=5) and $-0.37{\pm}0.25nA$(n=6), in the 1-cell stage, 2-cell stage fertilized eggs and in the unfertilized eggs, respectively. Pure inward current (difference between steady-state and peak, $i_{in. pure}$) were $-1.01{\pm}0.23nA$, $-0.69{\pm}0.43nA$ and $-0.68{\pm}0.29nA$, respectively in the 1-cell stage fertilized eggs, unfertilized eggs and 2-cell stage fertilized eggs. These results suggested that the outward current in fertilized eggs of 2-cell stage was more increased than those in the unfertilized eggs. Pure inward currents in the all stages of eggs showed a similar fashion in the I-V relationship from -50mV to 50mV and reversal potential at 50mV. Time constant of inactivation$({\tau})$ in the inward current was decreased as the membrane potential was depolarized in the unfertilized and 2-cell stage eggs but in the 1-cell stage eggs t was not likely to be affected significantly. Slope conductances were 14.2nS, 8.9n5 and 7.7nS in the 1-cell, 2-cell stage fertilized eggs and the unfertilized eggs, respectively. Membranes between two cells within a zona pellucida seem to be electrical-connected in the 2-cell stage eggs from the observation made in the analysis for the electronic spread and decay to the current stimuli. Both of inward current and membrane conductance were increased after fertilization in the mouse eggs. Inward current seems to be carried by the same ion or through the same channels up to the 2-cell stage and ion that carried inward current was thought to play important function after fertilization in the mouse eggs.

• Current Photovoltaic Research
• /
• v.8 no.3
• /
• pp.94-101
• /
• 2020

This study was trying to focus on achieving high efficiency of multi junction solar cell with thin film silicon solar cells. The proposed thin film Si-Ge/c-Si tandem junction solar cell concept with a combination of low-cost thin-film silicon solar cell technology and high-efficiency c-Si cells in a monolithically stacked configuration. The tandem junction solar cells using amorphous silicon germanium (a-SiGe:H) as an absorption layer of upper sub-cell were simulated through ASA (Advanced Semiconductor Analysis) simulator for acquiring the optimum structure. Graded Ge composition - effect of E_g profiling and inserted buffer layer between absorption layer and doped layer showed the improved current density (J_sc) and conversion efficiency (η). 13.11% conversion efficiency of the tandem junction solar cell was observed, which is a result of showing the possibility of thin film Si-Ge/c-Si tandem junction solar cell.

• International Journal of Automotive Technology
• /
• v.1 no.1
• /
• pp.9-16
• /
• 2000

The growing concerns on environmental protection have been constantly demanding cleaner and more energy efficient vehicles without compromising any conveniences provided by the conventional vehicles. The recent significant advances in proton-exchange-membrane (PEM) fuel cell technology have shown the possibility of developing such vehicles powered by fuel cells. Several prototype fuel cell electric vehicles (FCEV) have been already developed by several major automotive manufactures, and all of the favorable features have been demonstrated in the public roads. FCEV is essentially a zero emission vehicle and allows to overcome the range limitation of the current battery electric vehicles. Being motivated by the laboratory and field demonstrations of the fuel cell technologies, variety of fuel cell alliances between fuel cell developers, automotive manufactures, petroleum companies and government agencies have been formed to expedite the realization of commercially viable FCEV. However, there still remain major issues that need to be overcome before it can be fully accepted by consumers. This paper describes the current fuel cell vehicle development status and the staggering challenges for the successful introduction of consumer acceptable FCEVS.

• Proceedings of the KIEE Conference
• /
• 1999.07d
• /
• pp.1870-1872
• /
• 1999

Performance of 20-cell stack for direct methanol fuel cell (DMFC) was tested at constant temperature. Electrode evaluation used to the stack was tested by the performance of a single cell. A new composite electrode prepared from active carbon cloth and high porous active carbon was developed for hydrophilic layer of the cell. Characteristics of a single cell using the composite electrode showed the current density of $500mA/cm^2$ at the cell voltage of 0.4V at $120^{\circ}C$. For the operating of 20 days. the cell voltage at constant cell current densty of $100mA/cm^2$ was slightly reduced from 0.62V to 0.53V with the cell voltage decay rate of 14.5%. Power of 20-cell stack at 5.3V, $100^{\circ}C$ was about 180W.

• The Korean Journal of Physiology and Pharmacology
• /
• v.1 no.5
• /
• pp.477-484
• /
• 1997

Intracellular recordings of oscillatory firing (bursting activity) were obtained from Purkinje cells (PCs) in rat cerebellar slices. Apamin inhibited post-burst hyperpolarizations (PBHs) progressively and finally terminated oscillatory firing activity of PCs. Apamin did not affect the amplitude or duration of the after-hyperpolarization (AHP) between spikes within the burst. In the voltage clamp mode, apamin shifted the whole-cell, quasi-steady state I/V relationship in an inward direction and abolished the zero slope resistance (ZSR) region by blocking outward current. Nickel ($Ni^{2+}$) terminated oscillatory activity and also abolished the ZSR region. However, $Ni^{2+}$ did not have progressive blocking action on the post-burst hyperpolarization before it blocked oscillatory activity. $Ni^{2+}$ blocked an inward current at potentials positive to approximately -65 mV, which was responsible for the ZSR region and outward current at more negative potentials. These data indicated that oscillatory activity of PCs is sustained by a balance between a slow $Ni^{2+}$-sensitive inward current and an apamin-sensitive outward current in the region of ZSR of the whole-cell I/V curve.