• International Journal of Aeronautical and Space Sciences
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• v.18 no.2
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• pp.255-269
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• 2017

Free vibration analysis is presented for a simply-supported, functionally graded piezoelectric (FGP) nanobeam embedded on elastic foundation in the framework of third order parabolic shear deformation beam theory. Effective electro-mechanical properties of FGP nanobeam are supposed to be variable throughout the thickness based on power-law model. To incorporate the small size effects into the local model, Eringen's nonlocal elasticity theory is adopted. Analytical solution is implemented to solve the size-dependent buckling analysis of FGP nanobeams based upon a higher order shear deformation beam theory where coupled equations obtained using Hamilton's principle exist for such beams. Some numerical results for natural frequencies of the FGP nanobeams are prepared, which include the influences of elastic coefficients of foundation, electric voltage, material and geometrical parameters and mode number. This study is motivated by the absence of articles in the technical literature and provides beneficial results for accurate FGP structures design.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.11a
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• pp.47-48
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• 2006

Carbon nanotubes (CNTs)-doped homogeneously aligned nematic liquid crystal (LC) cells driven by in-plane field were fabricated and their electro-optic characteristics were investigated. Effective cell retardation values in an absence of an electric field between doped and undoped LC were the same each other. In the presence of an electric field, however, measured effective cell retardation value was smaller in the CNT-doped cell than in the undoped cell so that the transmittance was slightly smaller in the CNT-doped cell than in the undoped cell. In addition, the CNT-doped cell exhibited slight increase in driving voltage and decrease in response time compared to the undoped cell. The CNT effects on electro-optic characteristics of the cell were discussed.

• Journal of mucopolysaccharidosis and rare diseases
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• v.4 no.1
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• pp.21-25
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• 2018

Fabry disease is a hereditary lysosomal storage disorder caused by the reduction or absence of lysosomal enzyme alpha-galactosidase A and the accumulation of glycosphingolipids, such as globotriaosylceramide (Gb3), in various organs, including the heart. The prevention of cardiac involvement in Fabry disease can only be achieved by enzyme replacement therapy (ERT), and the method of assessing the efficacy of ERT should be confirmed. Changes in the electrocardiogram, such as the shortening of PQ interval, prolongation of QTc and repolarization abnormalities as well as left ventricular hypertrophy in voltage criteria, can be used to identify Fabry disease patients; however, the usefulness of electrocardiograms for evaluating the efficacy of ERT is limited. The assessment of left ventricular hypertrophy using echocardiography has been established to evaluate the efficacy of ERT during long-term period. A new technique involving speckled tracking method might be useful for detecting early cardiac dysfunction and identifying the effect of ERT for a relatively short period. The estimation of left ventricular hypertrophy using cardiac magnetic resonance (CMR) is also useful for assessing the efficacy of ERT. Identifying late gadolinium enhancement in CMR may affect the effectiveness of ERT, and the new technique of T1 mapping might be useful for monitoring the accumulation of Gb3 during ERT. Histopathology in cardiac biopsy specimens is another potentially useful method for identifying the accumulation of GB3; however, the use of histopathology to evaluate of the efficacy of ERT is limited because of the invasive nature of an endomyocardial biopsy.

• Journal of Power Electronics
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• v.9 no.2
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• pp.215-223
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• 2009

A design methodology for transformers including integrated and center-tapped structures for LLC resonant converters is proposed. In the LLC resonant converter, the resonant inductor in the primary side can be merged in the transformer as a leakage inductance. And, the absence of the secondary filter inductor creates low voltage stress on the secondary rectifiers and is cost-effective. A center-tapped structure of the transformer secondary side is widely used in commercial applications because of its higher efficiency and lower cost than full-bridge structures in the rectifying stages. However, this transformer structure has problems of resonance imbalance and transformer inefficiency caused by leakage inductance imbalance in the secondary side and the position of the air-gap in the transformer, respectively. In this paper, gain curves and soft-switching conditions are derived by first harmonic approximation (FHA) and operating circuit simulation. In addition, the effects of the transformer including integrated and center-tapped structures are analyzed by new FHA models and simulations to obtain an optimal design. Finally, the effects of the air-gap position are analyzed by an electromagnetic field simulator. The proposed analysis and design are verified by experimental results with a 385W LLC resonant converter.

• Journal of Information Display
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• v.11 no.3
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• pp.109-112
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• 2010

The solid phase compositions and dielectric properties of silicon nitride ($SiN_x$) films prepared using the plasma enhanced chemical vapor deposition (PECVD) technique at a low temperature ($200^{\circ}C$) were studied. Controlling the source gas mixing ratio, R = $[N_2]/[SiH_4]$, and the plasma power successfully produced both silicon-rich and nitrogen-rich compositions in the final films. The composition parameter, X, varied from 0.83 to 1.62. Depending on the film composition, the dielectric properties of the $SiN_x$ films also varied substantially. Silicon-rich silicon nitride (SRSN) films were obtained at a low plasma power and a low R. The photoluminescence (PL) spectra of these films revealed the existence of nano-sized silicon particles even in the absence of a post-annealing process. Nitrogen-rich silicon nitride (NRSN) films were obtained at a high plasma power and a high R. These films showed a fairly high dielectric constant ($\kappa$ = 7.1) and a suppressed hysteresis window in their capacitance-voltage (C-V) characteristics.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.10
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• pp.6666-6672
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• 2015

Various reflectometry methods to locate power cable fault have been studied. But, most related studies has been verifying by simulation and laboratory test and study in conditions similar with real cable fault filed was not performed due to the absence of cable fault test field. Therefore, this paper design and construct test field for the standardized performance test and the operating education of cable fault location equipments. In the constructed test, open, short, half open and poor contact fault at 100m, 200m location of cable was produced and 1km cable role was installed for maximum distance measurement test. The test field will be used in the development and standardization of cable fault location technology, and te performance evaluation and certificate test of the related equipments.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.26 no.4
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• pp.82-87
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• 2012

In this paper, flashover characteristics of air in the vertical arrangement of cylinder-shaped rod and plane gap in the case of combustion flame on the plane electrode were examined under the application of a.c. and d.c. high-voltages. In order to investigate the effect of propane flame on the flashover characteristics of air, flashover voltages in accordance with the variation of the gap length and the horizontal distance between the flame and the high-voltage rod electrode were measured. As the result of the experiment, flashover voltages in the presence of the flame were substantially lowered than those in the absence of flame, and the polarity effects with the d.c. voltages on appeared owing to the flame. Flashover voltages of air were increased in the proportion of the gap length and the horizontal distance in the case of both a.c. and d.c. voltages, but the flame was extinguished by such corona wind that was produced from the rod electrode when the gap length and the horizontal distance reached to a certain degree.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.51 no.8
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• pp.379-384
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• 2002

In the competitive electricity market, various pricing methods are developed and practiced in many countries. Among these pricing methods, marginal loss factor(MLF) can be applied to reflect the marginal cost of network losses. For the calculation of MLF, power flow method has been used to calculate system loss deviation. However, this power flow method shows some shortcomings such as necessity of regional reference node, and absence of an ability to consider network constraints like line congestion, voltage limit, and generation output limit. The former defect might affects adversely to the equity of market participants and the latter might generate an inappropriate price signals to customers and generators. To overcome these defects, the utilization of optimal power flow(OPF) is suggested to get the system loss deviation in this paper. 30-bus system is used for the case study to compare the MLF results by the power flow and the OPF method for 24-hour dispatching and pricing, Generator payment and customer charge are compared with these two methods also. The results show that MLF by OPF reflects the power system condition more faithfully than that of by the conventional power flow method

• Applied Science and Convergence Technology
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• v.23 no.2
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• pp.72-82
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• 2014

Lithium-ion batteries (LIBs) have become popular electrochemical devices. Due to the unique advantages of LIBs in terms of high operating voltage, high energy density, low self-discharge, and absence of memory effects, their application range, which was primarily restricted to portable electronic devices, is now being extended to high-power applications, such as electric vehicles (EVs) and hybrid electrical vehicles (HEVs). Among various anode materials, $Li_4Ti_5O_{12}$ (LTO) is believed to be a promising anode material for high-power LIBs due to its advantages of high working potential and outstanding cyclic stability. However, the rate performance of LTO is limited by its intrinsically low electronic conductivity and poor $Li^+$ ion diffusion coefficient. This review highlights the recent progress in improving the rate performance of LTO through doping, compositing, and nanostructuring strategies.

• Journal of the Korean housing association
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• v.12 no.3
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• pp.141-148
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• 2001

To design mechanical ventilation for bathroom of apartment houses where air supply and exhaust are taken into consideration, mock-ups of ventilation systems, widely used in bathroom of apartment houses with an area of 100$\textrm{m}^2$, were made and installed in a laboratory. These ventilation mock-ups were available for control of air supply and exhaust, and the sizes of supply openings were 40cm${\times}$1cm, 40cm${\times}$3cm, and 40cm${\times}$5cm. They were installed at five positions, spaced 45cm at a height of 5cm from the floor. The exhaust fan was designed for its operating voltage to be set to five steps(100V, 130V, 150V, 180V and 220V) in order to control its air flow rates. When the size and position of each supply opening were changed with the wind velocity of the exhaust fan set to the step 5, the ventilation rates were measured and analyzed by the concentration decay method of tracer gas method, in order to present an efficient mechanical ventilation system. The results of the study revealed that the ventilations rates would increase in the presence of supply openings, compared to the absence of supply openings, and that the larger the size of the supply opening, the more the ventilation rates. Therefore, it was found necessary to take air supply into consideration.