• The Transactions of the Korean Institute of Electrical Engineers B
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• v.49 no.5
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• pp.345-351
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• 2000

To improve the current waveform of diode rectifiers, we propose a new operating principle of the voltage diode rectifiers. In the conventional voltage rectifier circuit, relatively large capacitors are used to boost the output voltage, while the proposed circuit uses ones and a small reactor not boost the output voltage but improve the input current waveform. A circuit design method is shown and confirmed simulation. It explained that compared conventional PWM(Pulse-width modulated)inverter with HPWM(Half Pulse-width modulated)inverter. Proposed HPWM inverter eliminated dead-time by lowering switching loss and holding over-shooting. Output voltage and current of this paper were applied for real air-conditioner.

• Proceedings of the KIEE Conference
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• 2000.11b
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• pp.381-383
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• 2000

The photovoltaic power generation system has a great future as clean energy instead of fossil fuel which has many environmental problems such as exhausted gas or air pollution. In a utility interactive photovoltaic generation system, a three-phase inverter is used for the connection between the photovoltaic array and the utility. This paper presents a three phase inverter for photovoltaic power system with current controller, voltage controller, PLL control system and the phase detector of interactive voltage by using da transformation. The proposed inverter system provides a sinusoidal ac current for domestic loads and the utility line with unity power factor. The results of the operated from January to October show the system characteristics.

• Proceedings of the KIEE Conference
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• 1995.07a
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• pp.379-381
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• 1995

Many new electronic products are required to have a near unity power factor and a distortion free input current waveform. In this paper, a high performance single phase PWM AC/DC converter with input power factor correction is proposed. This proposed control strategy has many advantages which include one semiconduction switch, simplified control circuit, high performance features and continuous input current. The experimental results are included to verify the validity of this approach.

• Journal of the Korean Society for Precision Engineering
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• v.11 no.4
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• pp.26-37
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• 1994

A kinematically admissible velocity field for the numerical analysis of closed-die forging process of spur gear is proposed. The velocity field is divided into three regions of deformation. In the analysis, the involute curve is approximated to be straight line and the upper-bound method is used to calculate energy dissipation rate. A constant frictional frictional factor has been assumed on the contacting surfaces. The effects of root diameter, number of teeth, and friction factor are determined on the relative forging pressure. The frictionless relative pressure is independent of root diameter for the same number of teeth, but increases with the number of teeth on a given root diameter. In the presence of friction, the relative forging presure increasing root diameter at the start of forging, but decreases with increasing root diameter in the processing of forging.

• Proceedings of the Korea Water Resources Association Conference
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• 2017.05a
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• pp.183-183
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• 2017

Pan evaporation (Epan) is an important indicator of water and energy balance. Despite global warming, decreasing annual Epan has been reported across different continents over last decades, which is claimed as pan evaporation paradox. However, such trend is not necessarily found in seasonal data because the level of contributions on Epan vary among meteorological components. This study investigates long-term trend in seasonal pan evaporation from 1908 to 2016 across South Korea. Meteorological variables including air temperature (Tair), wind speed (U), vapor pressure deficit (VPD), and solar radiation (Rs) are selected to quantify the effects of individual contributing factor to Epan. We found overall decreasing trend in Epan, which agrees with earlier studies. However, mixed tendencies between seasons due to variation of dominant factor contributing Epan were found. We also evaluated the reference evapotranspiration based on Penman-Monteith method and compared this with Epan to better understand the physics behind the evaporation paradox.

• Communications for Statistical Applications and Methods
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• v.28 no.5
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• pp.521-536
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• 2021

As life expectancies increase continuously over the world, the accuracy of forecasting mortality is more and more important to maintain social systems in the aging era. Currently, the most popular model used is the Lee-Carter model but various studies have been conducted to improve this model with one of them being 6-parametric factor model (6-PFM) which is introduced in this paper. To this new model, long short-term memory (LSTM) and regularized LSTM are applied in addition to vector autoregression (VAR), which is a traditional time-series method. Forecasting accuracies of several models, including the LC model, 4-PFM, 5-PFM, and 3 6-PFM's, are compared by using the U.S. and Korea life-tables. The results show that 6-PFM forecasts better than the other models (LC model, 4-PFM, and 5-PFM). Among the three 6-PFMs studied, regularized LSTM performs better than the other two methods for most of the tests.

• Proceedings of the PSK Conference
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• 2003.10b
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• pp.169.2-170
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• 2003

Erythropietin (EPO), a hematopoietic factor is also required for normal brain development, and its receptor is localized in brain. Therefore, it is possible that EPO could act as a neurotropic factor inducing differentiation of neurons. The present study, we therefore investigated whether EPO can increase differentiation of undifferentiated cortical neuron isolated from postneonatal (Day 1) rat brains and PC12 cell, undifferentiated dopaminagic cell line. EPO dose (1-100 U/ml) dependently increased cell differentiation and expression of differentiation marker gene (neurofilament and tyrosine hydroxylase) in both cells. (omitted)

• KDI Journal of Economic Policy
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• v.46 no.1
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• pp.1-19
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• 2024

This paper evaluates explanations for China's growth slowdown. The natural tendency for rapidly growing economies to slow down is a major factor, along with problems bequeathed by unbalanced growth, including a declining ICOR, slowing total factor productivity growth, and rising indebtedness. A number of other mechanisms are of lesser importance: demographics, President Xi's centralization of political power and anti-corruption campaign, and U.S. export controls. Sustaining growth in the longer term will require China to step away from investment, debt and export-fueled growth in favor of a balanced growth model with household consumption playing a larger role. Doing so will require hardening of the budget constraints of regional and local governments and restructuring of the nonperforming debts of property and construction companies.

• Journal of the Korean Magnetics Society
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• v.7 no.1
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• pp.13-18
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• 1997

The effects of the various raw material composition and sintered temperature on the physical properties of Ni-Zn ferrite have been investigated. They turned out to be spinel structure by X-ray diffraction and the size of grain from microscope was from 6 ${\mu}{\textrm}{m}$ to 16 ${\mu}{\textrm}{m}$. As the sintering temperature was increased from 1030 $^{\circ}C$ to 1070 $^{\circ}C$, the initial permeability and magnetic induction has increased and the both of Q factor and coercive force has decreased. The coercive force and curie temperature were almost the same at each specimen. Their values were about 0.20 Oe and 220 $^{\circ}C$. The frequency of specimen will used in the range from 400 kHz to 20 MHz. The basic composition of $Ni_{0.14}Zn_{0.64}Cu_{0.22}Fe_2O_4$ (specimen B) sintered at 1050 $^{\circ}C$ shows the best results at magnetic induction($B_r & B_m$).

• The Journal of Korean Medicine
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• v.31 no.3
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• pp.107-121
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• 2010

Objective: This study aimed to ascertain the curative effects of Gamisipjeon-tang (GST) used for wound healing on the skin regeneration of deep second degree burns in mice. Material & Methods: In vitro, the $I{\kappa}B$ kinase (IKK) mRNA expression, inducible nitric oxide synthase (iNOS) mRNA expression, and cyclooxygenase-2 (COX-2) mRNA expression in the GST concentration from 1 mg/$m{\ell}$ to 10 mg/$m{\ell}$ were measured. In vivo, the mice were divided into four groups : the normal group, the BE group (burn-elicited group, control group), the DC group (Duoderm CGF-treated group after burn elicitation), and the GST group (Gamisipjeon-tang treated group after burn elicitation). To determine the anti-inflammatory effects, nuclear factor (NF)-${\kappa}B$ p65, iNOS, COX-2 positive reaction were measured by immunohistochemistry. To estimate the skin regenerative effects, change of burn area, 5-bromo-2'-deoxyuridine (BrdU), and fibroblast growth factor (FGF) positive reaction were analyzed. Results: In vitro, the iNOS, IKK, COX-2 mRNA expression decreased according to the increase of GST concentration. The significant decrease of COX-2, iNOS, NF-${\kappa}B$ positive reaction were the highest in the GST group, followed by the DC group and the BE group (p<0.05). The diameter of burn area was significantly decreased in the GST group as compared to that in the DC and BE group (p<0.05). The BrdU and FGF positive reaction increased more significantly in the GST group than in the DC group, and more significantly in the DC group than in the BE group on the 3rd and 7th day after burn (p<0.05). FGF positive reaction increased in the BE and DC group, whereas it decreased significantly in the GST group on the 14th day (p<0.05). The BrdU positive reaction increased in the BE group, whereas it decreased significantly in the DC and GST group on the 14th day (p<0.05). Conclusions: This study shows that GST could decrease the inflammatory response and accelerate the skin regeneration as compared to the duoderm CGF in mice with deep second degree burns.