• Journal of Power Electronics
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• v.16 no.3
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• pp.872-882
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• 2016

A novel pseudo-continuous conduction mode (PCCM) voltage-fed single-stage power factor correction (PFC) full-bridge battery charger is proposed in this paper. By connecting a freewheeling transistor in parallel with an input inductor, the PFC cell can operate in the PCCM with a constant duty ratio. Thus, the dc/dc stage can be designed using this constant duty ratio and the restriction on the duty ratio of the PFC cell is eliminated. As a result, the input current distortion is less and the dc bus voltage becomes controllable over the wide output power range of the battery charger. Moreover, the operation principle of the dc/dc stage is designed to be similar to that of a conventional phase-shifted full-bridge converter. Therefore, it is easy to implement. In this paper, the operation of the new converter is explained, and the design considerations of the controller and key parameters are presented. Simulation and experimental results obtained from a 1 kW prototype are given to confirm the operation of the proposed converter.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2001.09a
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• pp.35-37
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• 2001

This study has investigated the chemical characteristics and the contamination of groundwater in relation to land use in Daejeon Metropolitan City. An attempt was made to distinguish anthrophogenic inputs from the influence of natural chemical weathering on the chemical composition of groundwater at Taejon. Groundwater samples collected at 170 locations in the Taejon area show very variable chemical composition of groundwater, e.9. electrical conductance ranges from 65 to 1,290 S/cm. Most groundwater is weakly acidic and the groundwater chemistry is more influenced by land use and urbanization than by aquifer rock type. Most of groundwater from green areas and new town residential districts has low electrical conductance, and is of Ca-HC $O_3$ type, whereas the chemical composition of groundwater from the old downtown and industrial district is shifted towards a Ca-Cl (N $O_3$+S $O_4$) type with high electrical conductance. A number of groundwater samples in the urbanized area are contaminated by high nitrate and chlorine, and exhibit high hardness. The Ep$CO_2$, that is the $CO_2$ content of a water sample relative to pure water, was computed to obtain more insight into the origin of $CO_2$ and bicarbonate in the groundwater. Factor analysis of the chemical data shows that the HC $O_3$ and N $O_3$ concentrations have the highest factor loadings on factor 1 and factor 2, respectively. Factors 1 and 2 represent major contributions from natural processes and human activities, respectively. The results of the factor analysis indicate that the levels of $Ca^{2+}$, $Mg^{2+}$, N $a^{+}$, Cl and SO4$^2$ derive from both pollution sources and natural weathering reactions.ons.

• The Journal of the Acoustical Society of Korea
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• v.36 no.3
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• pp.151-157
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• 2017

A general linearly constrained adaptive array is proposed to improve the nulling performance. The nulling performance is examined in the array weight vector space. It is shown that the constraint plane is shifted to the origin perpendicularly by the gain factor such that the increase of the gain factor results in the decrease of the distance from the constraint plane to the origin. Thus the variation of the gain factor has an effect on the extent of orthogonality between the weight vector and the steering vectors for the interferences such that the nulling performance of the general linearly constrained adaptive array is improved by the gain factor. It is observed that the proposed adaptive array with an optimum value of the gain factor yields a better nulling performance in coherent signal environment and a similar nulling performance in noncoherent signal environment compared to the conventional linearly constrained adaptive array.

• Proceedings of the KIEE Conference
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• 2008.10a
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• pp.169-170
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• 2008

In this study, low temperature sintering property of the $0.6TiTe_3O_8-0.4MgTiO_3$ ceramics with sintering adds were investigated for LTCC application which enable to cofiring with Ag electrode. $TiTe_3O_8$ mixed with $MgTiO_3$ to improve the temperature property. In the X-ray diffraction patterns, the columbite structure of $TiTe_3O_8$ phase and ilmenite structure of $MgTiO_3$ phase were coexisted in all specimens. In the case of SnO addition, the bulk density and dielectric constant were increased but quality factor was decreased with amount of SnO additions. The TCRF of the $0.6TiTe_3O_8-0.4MgTiO_3$+xwt%SnO ceramics were shifted to negative direction. The dielectric constant, quality factor and TCRF of the $0.6TiTe_3O_8-0.4MgTiO_3$ ceramics with 2.5wt% addition of SnO sintered at $830^{\circ}C$ for 1hr were 29.86, 35,800 GHz, -0.58 ppm/$^{\circ}C$, respectively.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.8
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• pp.641-644
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• 2009

We have studied on the microwave characteristics for the meander type inductors on the MgO substrates and $Al_2O_3$ substrates by employing 3-D high frequency simulation, respectively. Proper designs of meander type inductors were proposed and confirmed through the high frequency simulations, 5, 7, 9, 11, and 13 turns meander type inductors have been choose to analyze the electrical properties for the microwave passive component applications. The Al top electrodes have 282 nm length, 45 nm width, 100 nm thickness and 15 nm gap. The simulations were carried out from 50 MHz to 30 GHz, Frequency dependent inductances and quality factor were calculated by employing the equivalent circuit model of meander type inductors. The self resonances frequency of meander type inductor were shifted from high frequency to low frequency range as the number of the turn of inductors was increased. From the microwave simulations, the inductances and quality factors of meander type inductors were extracted through the scattering parameter.

• Fashion & Textile Research Journal
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• v.14 no.3
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• pp.371-380
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• 2012

Based on results using factor analysis, Women's definition of "Ideal beauty" can be materialize into four key factors, "Confident beauty", "Graceful beauty", "Lively beauty", and "Genuine beauty". Factor analysis was conducted to materialize Women's definition of "Ideal beauty"and the above four factors were representative of 56.31% of total variance. "Ideal beauty" defined by age category was also found significant difference, indicating existence of different "Ideal beauty "definition for age groups. Itemized age category's "Ideal beauty" definitions are as follows, 18-22 years, bright and lively, 23-27 years, cute and confident, 28-32 years, sensible and confident 33-37 years, hard-working, 38-42 years, ability and composure, 43-47 years, casual and graceful, 48-52 years, refined and noble, 53 years and above, healthy and proper as "Ideal beauty" definitions. The defined "ideal beauty" was steadily shifted with age group. Women 38 years and younger were defined external attributes to "Ideal beauty", as women 38 years and older were defined inner attributes to "Ideal beauty". Women's definition of "Ideal beauty" can materialize into four key factors, "Confident beauty", "Graceful beauty", "Lively beauty", and "Genuine beauty".

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.04a
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• pp.496-500
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• 1997

This paper describes an automated system for analyzing the stress intensity factors(SIFs) of three-dimensional (3D) cracks. A geometry model, i.e.a solid containing one or several 3D cracks is defined. Several distributions of local node density are chosen, and then automatically superposed on one another over the geometry model by using the fuzzy knowledge processing. Nodes are generated by the bucketing method, and ten-noded quadratic tetrahedral solid elements are generated by the Delauuay triangulation techniques. The singular elements such that the mid-point nodes near crack fornt are shifted at the quarter-points are automatically placed along the 3D crack front. THe complete finite element (FE) model generated, i.e the mesh with material properties and boundary conditions is given to one of the commercial FE codes, and a stress analysis is performed. The SIFs are calculated using the displacement extrapolation method. To demonstrate practical performance of the present system, a semi- elliptical surface crack in a plate subjected to tension is solved.

• The Journal of Asian Finance, Economics and Business
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• v.7 no.11
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• pp.759-768
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• 2020

The purpose of this study is to assess the state of competition in Nepalese banking over the period from 2010 to 2019. This study employs panel data and a non-structural Panzar-Rosse model to measure the degree of competition in the Nepalese banking industry. The first reduced-form equation is applied to gauge competition, and the second model is used to test the long-run equilibrium in the banking market. The finding reveals that the Nepalese banking market is equilibrium in the long-run. It implies that the factor prices do not affect ROA in the long-run. The result of the H-statistic shows that the Nepalese banking system is operating under the state of perfect competition and is shifted from monopolistic competition to perfect competition. The reduced-form model reveals that the interest income is positive and significantly affected by factor prices. Similarly, the macroeconomic variable GDP growth is positively related to interest income. On the contrary, the bank's specific factors risk and the number of bank branches are inversely associated with the regressand. The outcomes of the study may be advantageous to the policymakers, especially to Nepal Rastra Bank to implement monetary policy and M&A policy for the stability and growth of the financial system of Nepal.

• Journal of Power Electronics
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• v.19 no.2
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• pp.475-486
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• 2019

This paper proposes the modulation and control of a three-to-six-phase matrix converter with an asymmetrical six-phase output. The matrix converter (MC) outputs consist of two sets of three-phase spatially shifted by $30^0$, where the two sets have two isolated neutrals. The space vector approach is considered for the modeling and subsequent modulation of the three-to-six phase MC. The intelligent selection of voltage space vectors is made to synthesize the reference voltages and to obtain a sinusoidal output. The dwell times of selected voltage space vectors are adjusted in such a way that the effect of the second and the third auxiliary plane vectors (i.e., x1-y1, and x2-y2) are nullified. To achieve the maximum output voltage gain and to ensure that no reactive power is drawn from the utility supply, the input side power factor is maintained at unity. Nevertheless, the source side power factor is controllable. The modulation technique is implemented in dSPACE working in conjunction with a FPGA. Hardware results that validate the proposed control algorithm are discussed.

• Journal of Applied Biological Chemistry
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• v.66
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• pp.106-113
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• 2023

Plant extracts have been studied due to their potential as photoprotective agents against UV and blue light exposure. Previous studies have revealed that several plant extracts have photoprotection capacities and synergistic effects with synthetic products. However, such results for pu'er tea and Curcuma longa L. have not been reported yet for a cosmetic formulation. Thus, the objective of this study was to evaluate photoprotection capacities of pu'er tea and C. longa L. extracts for a sunscreen compound. The pu'er tea extract improved sun protection factor value of 2-ethyl-hexyl methoxycinnamate (a synthetic sunscreen compound) by 46% and showed a high antioxidant capability that could help skin recover from photo-induced damage. C. longa L. extract also showed a potential to protect skin from blue light-induced damage because it not only had a maximum absorption peak at the blue light range, but also protected human fibroblasts from blue light-induced damage. The addition of both extracts shifted the critical wavelength of 2-ethyl-hexyl methoxycinnamate from 350 nm to 386 nm, giving it a broad-spectrum feature. Thus, pu'er tea and C. longa L. extracts may enhance the photoprotection ability of synthetic sunscreen products.