• Journal of Electrical Engineering and Technology
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• v.11 no.4
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• pp.860-868
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• 2016

A bidirectional DC-DC converter (BDC) is an indispensable electrical unit for the electric vehicles (EVs). High efficiency, high power density, isolation, light weight and reliability are all essential requirements for BDC. In this paper, a 3 kW BDC for the battery charger of EVs is proposed. The proposed converter consists of a half-bridge structure on the primary side and an isolation transformer and a synchronous rectifier structure on the secondary side. With this topology, minimum number of switching devices are required for bidirectional power flow between the two dc buses of EVs. The easy implementation of the synchronous rectification gives advantages in terms of efficiency, cost and flexibility. The proposed BDC achieves high efficiency when operating in both modes (step-up and step-down). A 3 kW prototype is implemented to verify theoretical analysis and the performance of the proposed converter.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07a
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• pp.162-164
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• 2004

Nanocrystalline silicon(nc-Si) thin films on the silicon substrates have been prepared by pulsed laser deposition(PLD). The optical and structural properties of films have been investigated depending on deposition temperature, annealing, and oxidation process. When the deposition temperature increased, photoluminescence(PL) intensity abruptly decreased and peaks showed red shift. Annealing process could reduce the number of defect centers. Oxidation had a considerable effect upon the formation and isolation of the nanocrystals. These results indicate that the formation mechanism of Si nanocrystals grown by PLD can be explained by three steps of growth, passivating defect centers, and isolation, sequentially.

• Earthquakes and Structures
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• v.25 no.4
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• pp.297-305
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• 2023

The conventional method of structural seismic design was based on increasing structural capacity, which usually didn't reduce earthquake seismic effects. By changing the philosophy of structure design, technologies such as passive seismic control have been used in structures. So far, a large number of seismic isolation systems have been introduced to dissipate earthquake energy that is applied to a structure. These systems act against earthquakes rather than increasing the strength and capacity of the structure. In the present paper, a suspended column called a "pendulum column" is investigated, and a new idea has been considered to improve the performance of the pendulum column isolator by changing the gravity effect by adding a spring under the isolator system. The behavior of the studied isolator system has been researched. Then the isolator system was investigated under different earthquakes and compared with a common pendulum column isolator. The results show that changing the gravity effect has an effective role in the response of the system by reducing the system stiffness. Equations for the system showed that even in a special state, complete isolation is possible. Finally, the tested model verified the theory.

• The Korean Journal of Mycology
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• v.26 no.2 s.85
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• pp.275-280
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• 1998

Factors affecting protoplasts isolation and regeneration of Fomitella fraxinea were investigated. Lytic enzyme mixture of Novozym 234, Cellulase onozuka R-10 and ${\beta}-Glucuronidase$ was found to be the best for the protoplasts isolation. Osmotic stabilizer of 0.6 M sucrose was observed as the best for protoplasts isolation. The highest number of protoplasts was obtained from the F. fraxinea mycelium with lytic enzyme mixture and osmotic stabilizer that had been cultured for 3 hours. The highest regeneration rate of 0.02 % was achieved when the 0.6 M sorbitol was employed as osmotic stabilizer.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.1 s.343
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• pp.143-148
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• 2006

This paper presents a high isolation and power-handling single-pole double-throw(SPDT) switch for dual band wireless LAN applications. The switch circuit has asymmetric topology which uses stacked-gate to have high power-handling and isolation for the Tx path. The proposed SPDT switch has been designed with optimum gate-width, bias, and number of stacked-gate FET. This SPDT switch has been implemented with $0.25{\mu}m$ GaAs pHEMT process which has Gmmax of 500mS/mm and fmax of 150GHz. The designed SPDT switch has the measured insertion loss of better than 0.9dB and isolation of better than 40dB for the Tx path and 25dB for the Rx path and the high power handling capability with PldB of about 23dBm for control voltage of -3/0V. The fabricated SPDT switch chip size is $1.8mm{\times}1.8mm$.

• Computers and Concrete
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• v.21 no.5
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• pp.495-504
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• 2018

The possibility of earthquakes in vulnerable regions indicates that efficient technique is required for seismic protection of buildings. During the recent decades, the concept is moving towards the insertion of base isolation on seismic prone buildings. So, investigation of structural behavior is a burning topic for buildings to be isolated in base level by bearing device. This study deals with the incorporation of base isolation system and focuses the changes of structural responses for different types of Lead Rubber Bearing (LRB) isolators. A number of sixteen model buildings have been simulated selecting twelve types of bearing systems as well as conventional fixed-base (FB) scheme. The superstructures of the high-rise buildings are represented by finite element assemblage adopting multi-degree of freedoms. Static and dynamic analyses are carried out for FB and base isolated (BI) buildings. The dynamic analysis in finite element package has been performed by the nonlinear time history analysis (THA) based on the site-specific seismic excitation and compared employing eminent earthquakes. The influence of the model type and the alteration in superstructure behavior of the isolated buildings have been duly assessed. The results of the 3D multistory structures show that the lateral forces, displacement, inertia and story accelerations of the superstructure of the seismic prone buildings are significantly reduced due to bearing insertion. The nonlinear dynamic analysis shows 12 to 40% lessening in base shear when LRB is incorporated leading to substantial allowance of horizontal displacement. It is revealed that the LRB isolators might be potential options to diminish the respective floor accelerations, inertia, displacements and base shear whatever the condition coincides. The isolators with lower force intercept but higher isolation period is found to be better for decreasing base shear, floor acceleration and inertia force leading to reduction of structural and non-structural damage. However, LRB with lower isolator period seems to be more effective in dropping displacement at bearing interface aimed at reducing horizontal shift of building structure.

• Journal of Korea Water Resources Association
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• v.52 no.4
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• pp.291-300
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• 2019

If pipes are damaged in a water distribution network (WDN), adjacent valves are closed to isolate the pipes for repair. Due to the closed valves, parts of WDN are isolated from water supply sources. The isolated area is divided into Intended Isolation Area (IIA) and Unintended Isolation Area (UIA). The IIA occurs by intention to isolate the damaged pipe, while UIA is unintentionally disconnected from the sources due to IIA. Thus, the extension of isolated area and suspended flows are mainly affected by number and location of installed valves in WDN. In this study, optimization models were developed to determine optimal valve locations in WDN. In a single-objective model, total water supply suspension is minimized, while a multi-objective model intends to simultaneously minimize the suspended flow and valve installation cost. Optimal valve placement results obtained from both models were compared and analyzed using a sample application network.

• Archives of Reconstructive Microsurgery
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• v.16 no.2
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• pp.57-62
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• 2007

Non-vascularized free composite graft is one of the simple and effective reconstructive options, but its clinical use has been limited due to questionable survival rate. Early vascularization is essential for graft survival and is mainly carried out via recipient bed or repaired sites. This study was designed to investigate the effect of the lateral marginal approximations on the survival of the free composite flap using a model of skin-subcutaneous composite graft in rats. Thirty 1.5 ${\times}$ 1.5 $cm^2$ sized square shape composite flaps were elevated freely and reposed in place immediately on the dorsum of five Sprague-Dawley rats, and divided into five groups of six flaps. In all groups, graft bed was isolated with silastic sheet. In the group I, all sides of flap were repaired with blockage of silastic sheet insertion. Three, two, and one sides of flap were treated with same method in the group II, III, and IV respectively. Other sides of flaps were repaired without blockage, so all sides of flap were repaired in the group V. At 14 days later, the survived rate of each flap was evaluated according to the numbers of the repair sites. Histological examination was done for the evaluation of new vessel development quantitatively. Overall survived rates were increased with the number of repaired sites, but the group V only showed increased survival rate up to more than fifty percentile of the flap size with a significant difference statistically. New vessels were also increased in proportion with the number of repaired sites, and the repair site more than two had significant effect on the increased number of new vessels. In conclusion, at least more than three-fourth of flap circumference should be repaired in order to increase flap survival effectively under the condition of bed isolation.

• Structural Engineering and Mechanics
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• v.66 no.3
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• pp.411-421
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• 2018

Although a rubber isolation cushion can reduce the dynamic response of a structure itself, it has little influence on the height of a sloshing wave and even may induce magnification action. Vertical baffles are set into a base-isolated Concrete Rectangular Liquid Storage Structure (CRLSS), and baffles are opened as holes to increase the energy dissipation of the damping. Problems of liquid nonlinear motion caused by baffles are described using the Navier-Stokes equation, and the space model of CRLSS is established considering the Fluid-Solid Interaction (FSI) based on the Finite Element Method (FEM). The dynamic response of an isolated CRLSS with various baffles under an earthquake is analyzed, and the results are compared. The results show that when the baffle number is certain, the greater the number of holes in baffles, the worse the damping effects; when a single baffle with holes is set in juxtaposition and double baffles with holes are formed, although some of the dynamic response will slightly increase, the wallboard strain and the height of the sloshing wave evidently decrease. A configuration with fewer holes in the baffles and a greater number of baffles is more helpful to prevent the occurrence of two failure modes: wallboard leakage and excessive sloshing height.

• Journal of Food Hygiene and Safety
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• v.22 no.4
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• pp.388-394
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• 2007

This study was conducted to evaluate the selective media listed in currently available Food Code in Korea. The 29 different types of media of five different types of foodborne bacteria including Salmonella spp., Bacillus cereus, Listeria monocytogenes, Vibrio parahaemolyticus, Staphylococcus aureus were tested in the broth and food. The recovery test for five different types of foodborne bacteria was performed in the artificially inoculated into chicken, rice, pork and mackerel. There was no significant differences in isolation capabilities among twenty nine different types of isolation selective media for five different types of foodborne bacteria in broth condition, while there was significantly a little differences in isolation capabilities among those on foods (P<0.05). The higher number of foodborne pathogens were isolated from conventional selective media approved in Food Code than newly developed selective media such as chromogenic media. This results suggest that there was differences of selectivities among currently available isolation selective media in many countries and further studies are needed to be approved by Korean Food and Drug Administration.