• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.226-226
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• 2010

Microstructure, magnetic and transport properties of as-deposited electron-doped $La_{1-x}Ce_xMnO_3$ and hole-doped $La_{1-x}Ce_xMnO_3$ films prepared by pulse laser deposition, with x = 0.1 and 0.3, have been investigated. The microstructural analysis reveals that the $La_{1-x}Ce_xMnO_3$ films have a column-like microstructure and a strip-domain phase with a periodic spacing of about 3c, which were not found for the $La_{1-x}Ce_xMnO_3$ ones. At the same time, the experimental results manifest that there is no fundamental difference in the magnetic and the transport properties between electron- and hole-doped manganite films, except the appearance of ferromagnetic response in the low-doped $La_{0.9}Ce_{0.1}MnO_3$ film at temperatures above the Curie point. The observed magnetic behavior, typical for the Griffiths-like phase, for this film is explained by the percolation mechanism of the ferromagnetic transition and by the presence of strip-domain phase which stimulates the magnetic phase separation.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.12 no.7
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• pp.510-519
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• 2002

The present study addresses a computational work of the weak shock wave propagating inside an automobile exhaust muffler. Several different types of the silencer systems are employed to investigate the magnitude of the shock wave during propagating through them. The Initial shock wave Mach number $M_s$ is varied between 1.01 and 1.30, and a normal shock wave is given at the inlet of the silencer systems. The second order total variation diminishing scheme Is employed to solve the two dimensional, compressible, unsteady Euler equations. The present computational results are compared with the previous experimental ones available. The present computations predict the experimental results with a quite good accuracy. Of the four silencer systems applied. the most desirable silencer system to reduce the peak pressure at the exalt of the exhaust pipe is discussed from the Point of view of the engineering design of the silencer systems.

• Journal of Power Electronics
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• v.17 no.4
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• pp.923-932
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• 2017

This paper proposes a novel scheme which can compensate the common-mode voltage (CMV) for five-level active neutralpoint clamped (5L-ANPC) inverters, which is based on modifying the space vector pulse width modulation (SVPWM) and adding an auxiliary leg to the inverter. For the modified SVPWM, only the 55 voltage vectors producing low CMV values among the 125 possible voltage vectors are utilized, which varies over the three voltage levels of $-V_{dc}/12$, 0 V, and $V_{dc}/12$. In addition, the compensating voltage, which is injected into the 5L-ANPC inverter system to cancel the remaining CVM through a common-mode transformer (CMT) is generated by the additional NPC leg. By the proposed method, the CMV of the inverter is fully eliminated, while the utilization of the DC-link voltage is not decreased at all. Furthermore, all of the DC-link and flying capacitor voltages of the inverter are well controlled. Simulation and experimental results have verified the validity of the proposed scheme.

• Proceedings of the Korea Water Resources Association Conference
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• 2018.05a
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• pp.327-327
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• 2018

돌발홍수, 집중호우 등 강우가 발생 원인되는 자연재해에 효과적으로 대응하기 위한 연구가 활발히 이루어지고 있으나 강우의 시공간 변동성과 발생과정의 복잡한 물리과정으로 인해 강우 추정에 한계를 가진다. 일반적으로 강우 추정은 물리적, 추계학적 모형을 이용하며 추계학적 모형의 점과정(point process)을 이용하여 강우를 생산한다. 추계학적 강우 모형은 관측 강우의 시간 스케일, 강우발생 빈도, 강우 강도 등 강우 구조의 특성을 반영 할 수 있다는 장점을 가지고 있으나 생산되는 강우의 구조가 추정되는 매개변수에 크게 의존한다는 점에서 실제 강우에 적합한 매개변수 추정이 중요하다. 본 연구에서는 낙동강 유역내에 있는 20개의 강우관측 지점을 대상으로 1973년-2017년까지의 강우 관측자료를 수집하였으며 추계학적 강우생성 모형으로 점과정을 이용하는 추계학적 강우생성 모형인 NSRPM(Neymann-Scott rectangular pulse model)을 선정하였다. NSRPM모형의 매개변수를 추정하기위한 최적기법으로 DFP(Davidon-Fletcher-Powell), GA(genetic algorithm), Nelder-Mead, DE(differential evolution)를 이용하여 추정된 매개변수의 적합성을 분석하고 지역특성을 고려한 매개변수 추정 기법을 제시하였다. 추정된 모형의 매개변수를 분석한 결과 DE와 Nelder-Mead 기법이 높은 적합성을 보였으며 DFP, GA기법이 상대적으로 낮은 적합도를 보였다.

• Proceedings of the KSR Conference
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• 1999.11a
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• pp.318-325
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• 1999

Modern AC electric car has PWM(Pulse Width Modulation)-controlled converters, which give rise to higher harmonics. The current harmonics injected from AC electric car is propagated through power feeding circuit, As the feeding circuit is a distributed constant circuit composed of RLC, the capacitance of the feeding circuit and the inductance on the side of power system cause a parallel resonance and a magnification of current harmonics at a specific frequency. The magnified current harmonics usually brings about various problems. That is, the current harmonics makes interference in the adjacent lines of communications and the railway signalling system. Furthermore, in case it flows on the side of power system, not only overheating and vibration at the power capacitors but also wrong operation at the protective devices can occur. Therefore, the exact assessment of the harmonic current flow must be undertaken at design and planning stage for the electric traction systems. From these point of view, this study presents an approach to model and to analyse traction power feeding system focused on the amplification of harmonic current The proposed algorithm is applied to a standard AT(Auto-transformer)-fed test system in which electric car with PWM-controlled converters is running.

• Journal of Power Electronics
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• v.19 no.1
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• pp.146-157
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• 2019

The inverter is an essential part of permanent magnet synchronous motor (PMSM) drive systems. The performance of an inverter is greatly influenced by its modulation strategy. Using a proper management of modulation strategies can guarantee high performance from a PMSM under various speed conditions. Switching between modulations is a pivotal technique that determines the performance of a PMSM. Most works on hybrid methods focus on two-level induction motors drive systems. In this paper, in order to improve the performance of PMSMs under various speed conditions, a hybrid method of a pulse width modulation (PWM) control scheme based on a neutral-point-clamped (NPC) three level topology was proposed. This hybrid PWM modulation comprised space vector PWM (SVPWM) and selective harmonic elimination PWM (SHEPWM). Under low speed conditions, the SVPWM is employed to cause the PMSM to start smoothly, and to obtain a rapid response from the control system. Under high speed conditions, the SHEPWM is employed to reduce the switching frequency and to eliminate particular current harmonics. Moreover, the harmonic characteristics of different modulations are analyzed to obtain a smooth transition between the SHEPWM and the SVPWM. Experimental and simulation results indicated the effectiveness of the proposed control method.

• Current Optics and Photonics
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• v.7 no.3
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• pp.297-303
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• 2023

In this paper, we demonstrated a high-energy (285 mJ) mid-infrared flashlamp-pumped electro-optically 𝚀-switched Er:YAG master oscillator power amplifier (MOPA) system and comprehensively investigated its temporal, spectral, and spatial characteristics. To increase the output energy, we optimized the delay between the timings at which the flashlamps of the master oscillator and power amplifier were triggered. In addition, the output energy was improved while minimizing thermal effects by cooling the MOPA system to a temperature slightly above the dew point. Consequently, the MOPA structure boosted the output energy without damaging the lithium niobate Pockels cell, which is a crucial element in 𝚀-switching. This design realized pulses with energies up to 0.285 J and pulse durations of approximately 140 ns at a wavelength of 2,936.7 nm. This high-energy mid-IR Er:YAG MOPA system can be used for various scientific, engineering, and military underwater applications.

• Journal of Physiology & Pathology in Korean Medicine
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• v.17 no.5
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• pp.1157-1176
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• 2003

The following conclusions are induced from a study on the acupuncture therapy depending on hyungsang of the persons. The study is made on the basis of 'Internal classic (內經)& and &Clinical Lectures by Dr. Jeesan&. The acupuncture originated from the treatment of spasm with numbness in the southern area. The acupuncture is basically a remedy for the exterior disease of meridian but also it can be a cure for the interior disease of Jang and obstinate disease with accurate method. Three mechanisms of acupuncture are described in 'Internal classic'. The first is to make meridian circulate smoothly. The second is to regulate Ki and Hyul. The third is to regulate points through which the meridian-Ki goes in and out smoothly or adversely. There are two ways of acupuncture in 'Internal classic'. One is based on pulse and symptom and the other on the Hyungsang. The former is more generally used therapy, to which depletion method, Asi point method(阿是穴 療法), Inyoung-kigu pulse comparison method (人迎氣口脈法) and method depending on jang-bu disease belong. Acupuncture is done on Su points(輸穴) and back-su point(背兪穴) in case of jang-disease. In case of bu-disease, the treatment is done on Hap points(合穴) and Mo-points(募穴). The latter includes two methods; one according to invariable Hyungsang. And the other to variable Hyungsang. The method of acupuncture according to invariable Hyungsang usually selects Won-points(原穴). Different Hyungsang requires different method of acupuncture; In case of Dam type, the acupuncture is mainly practiced on four-Kwan points with reinforcing and reducing methods achieved by the direction of the needle tip pointing to. In case of Bangkwang type, the acupuncture is usually done on Jungwan(中脘) and Poongyung(豊隆) with reinforcing and reducing methods by means of respiration. In case of female, more effective are the acupoints on the right and lateral parts of the body selected on the basis of five su-points of the twelve meridians matching the heavenly stems and earthly branches. In case of male, more effective are the acupoints on the left, front and rear parts of the eight extra meridians. In case of acupuncture to the person with Hyungsang of five jang and six bu, each person's intrinsic Hyung, color, pulse, must be observed. Because symptoms of jang-bu disease also must be checked up. Acupuncture is done on the Won-points of the meridians related to the jang and bu where the disease starts. The disease of five jang is so obstinate that it requires both of medication and acupuncture for a long time. In case of acupuncture to the person with Hyungsang of animal types, diagnosis is made on the basis of shape, temper, function and color. And the treatment is given on the Won-points of corresponding exterior and interior meridians. For the fish type, the acupuncture is done on the kidney meridian of foot-soyin and the urinary bladder of foot-taiyang. For the bird type, on the heart meridian of hand-soyin, the pericardium meridian of hand-gualyin, and the small intestine meridian of hand-taiyang For the deer type, on the liver meridian of foot-gualyin and the gallbladder meridian of foot-soyang. For the turtle type, on the lung meridian of hand-taiyin and the large intestine meridian of hand-yangmyung.

• Journal of Sericultural and Entomological Science
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• v.18 no.2
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• pp.89-93
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• 1976

The physiological saline solution for animals is known as Ringer's solution which is used for keeping the function of cold blooded vertebrate animals. Primaily the saline solution is used for the purpose of perfusion experiment in frogs. Later the saline solution is applied in several kinds of animals including human being with satisfactory results. However, this saline solution was introduced to silkworm and it was found that the result was not as successful as in the case of other animals and human being. Normally, in the case of silkworm, the physiological saline solution is prepared in order to maintain the normal function of separated organs and tissues. To this end, the saline solution is adjusted to contain the certain amount and strength of ions, osmosis pressure and hydrogen concentration. The most of cases, the physiological saline solution should be prepared so that the constituent of the solution be the same with the blood selium and body fluid. The hydrogen concentration in the ion element of the saline solution is adjustable by adding Na$\^$＋/, K$\^$＋/, Ca$\^$＋＋/, Mg$\^$＋＋/ which are followed by adding of buffer solution such as NaHCO$_3$and NaH$_2$PO$_4$. Determination of optimum concentration of cation in the physiological saline solution, and the optimum mixing rate of more than two kinds of cations are based on the movement of dorsal vessel in the silkworm larvae. The optimum concentration of cations in the solution is prepared by adding NaCl solution which is under zero point. However, this solution was further added with the different concentration of KCl and CaCl$_2$. By dropping the prepared solution on the 5th larvae, the effects of solution was measured. The measurement was done by observation of movement' of dorsal vessel and its time length, and the number of pulses. According to the experiment, it was found that when only NaCl solution was applied, the number of pulses is increased for a moment, and the pulse stopped after one hour or so. When KCl solution was added the time of pulse was prolonged and in the contrast, the number of pulses was slow down. If KCl and CaCl$_2$solutions are added the time of pulse was further prolonged. Even though the adding of KCl and CaCl$_2$are found to be effectible, the correlation between the concentration of solution and the movement of dorsal vessel was not observed. However, it was same in the case of adding Ca$\^$＋＋/ or K$\^$＋/. It was found that when Mg$\^$＋＋/ was added to dorsal vessel the number of the pulses was not decreased although the prolonged time pulse was observed.

• Journal of Acupuncture Research
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• v.25 no.2
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• pp.165-177
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• 2008

Objectives : Headache is one of the most common symptom in primary medical care. The purpose of this research is to examine persisting effects of acupuncture treatment for CTTH. Methods : In this randomized, single blind, placebo-controlled study, we compared active acupuncture with sham acupuncture method for the treatment of chronic tension-type headache. Volunteers who satisfied the requirements were enrolled in study. Evaluation of CTTH was measured by VAS, and Headache Disability Inventory(HDI), Six point Likert Scale, Algometer score(Rt, Lt) before and after treatments. Results : 32 subjects finished study. There were no difference between two group on age, sex, weight, height, blood pressure, pulse, respiratory rate, differentiation of symptoms, surmise of treatment. In change of VAS, after treatment decreased than before treatment in two group, but there were no statistical significance compared with two group and time. In change of HDI(Total score, Emotional score, Functional score) and Six point Likert scale, after treatment decreased than before treatment in two group, but there were no statistical significance compared with two group and time. In change of two sides Algometer score, after treatment increased than before treatment in two group, and Lt algometer score was statistical significance compared with two group(p<0.001). And both sides Algometer score, threr were statistical significance compared with time. Conclusions : Acupuncture treatment has persisting effects that improve the symptoms and decrease the temporal muscle tenderness in patient with chronic tension-type headache.