Earticle

고조파에 의한 전기설비 사고와 경제적 손실은 증가하고 있다. 고조파 수동 필터는 고조파를 억제하는데 효과적이고 경제적이지만, 많은 현장 엔지니어들은 고조파 증폭과 병렬 공진 발생 등의 문제점으로 인해 계통에 수동 고조파 필터를 설치하는 것을 꺼려한다. 본 논문에서는 이러한 문제점을 해결하기 위해 역률 보상을 기반으로 하는 고 조파 수동필터 제어기를 개발하였다. 개발된 시스템의 전압 및 전류 측정 정확도는 표준 전력 발생장비인 FLUKE 61000A를 이용하여 시험하였으며, 측정 정확도는 0.5% 이하로 나타났다.

Accidents of electric equipment and economical loss by harmonics show a rising tendency. A passive filter is economic and efficient in suppressing harmonics. But many engineers and designers are reluctant to install a passive filter to defect harmonics at their power system because of problems such as harmonic amplification and the probability of generating series or parallel resonance with the power system. This work have developed harmonic passive filter controller based on power factor correction that passive filters. The volated and current measurement accuracy of the developed system is tested by using electrical power standard devices FLUKE 61000A. The test results showed that accuracy of the developed system is less than 0.5 %

SiO2 첨가가 Fe-Si계 합금의 열전물성에 미치는 영향에 대해 연구하였다. Fe, Si, Mn(p형 불순물), Co(n형 불순물) 및 SiO2의 혼합 분말을 고주파 유도가열로를 이용해서 0～2wt% SiO2 첨가 Fe0.97Mn0.05Si2 및 Fe0.97Co0.03Si2 ingot을 제조하였다. Ingot을 분쇄해서 체가름한 분말을 성형하고, Ar+7%H2 분위기 1200℃에서 10 시간 소결시킨 후 반도성인 β-FeSi2상으로의 상전이를 위해 830℃에서 100시간 열처리 공정을 행하였다. Ar 분위 기 150～700℃에서 동일 시편에 대해 Seebeck 계수와 도전율을 측정하였다. 온도 상승과 함께 Seebeck 계수가 상승하였고, Mn 고용 p형 FeSi2는 650K 부근에서 최고값을 갖고 감소하였으며, Co 고용 n형 FeSi2는 750K 부근 을 경계로 점차 감소 또는 유지하는 경향을 나타내었다. 절연성 SiO2의 영향으로 SiO2 첨가량이 증가함에 따라 Seebeck 계수가 상승하였다. 반면에 도전율은 SiO2 첨가량이 증가함에 따라 감소하였으며, 금속전도성인 ε-FeSi 상의 잔존량과 함께 밀도 및 기공률 등의 미세구조의 영향도 상당히 크게 기여하였다. Power factor는 p형 FeSi2 에서는 SiO2를 0.5wt% 첨가한 시편이 800K 이상에서 10-5.14대, n형 FeSi2에서는 2wt% 첨가한 시편이 750K 이 상에서 10-5.05대로 가장 큰 값을 나타내었다.

The effect of SiO2 addition on the thermoelectric property of Fe-Si alloy was investigated. The starting Fe-Si alloy powders were obtained from ingots in the composition Fe0.95Mn0.05Si2 and Fe0.97Co0.03Si2 added 0～ 2wt% SiO2, which were prepared in a RF inductive furnace from Fe, Si, Mn, and SiO2 powders. The various starting powders were pressed into a compact, and sintered at 1200℃ for 10h, heat treated at 830℃ for 100h under Ar+7%H2 atmosphere to transform to the semiconducting β-FeSi2 phase. The Seebeck coefficient and electrical conductivity were measured for the same specimen at 150～700℃ under Ar atmosphere. The Seebeck coefficient increased with increasing temperature, that of Mn-doped FeSi2 exhibited the maximum value at about 650K and decreased with increasing temperature. The Seebeck coefficient of Co-doped FeSi2 exhibited the maximum value at about 750K and decreased slightly and/or little changed with increasing temperature. The Seebeck coefficient for all specimens increased with increasing the amount of SiO2 additive exhibited insulating behavior. On the other hand, electrical conductivity decreased with increasing the amount of SiO2 additive. Amount of ε-FeSi exhibited metallic conduction and microstructure(density, porosityb etc.) were considerably effective to electrical conductivity. The maximum value of power factor was the order of 10-5.14 at above 800K for p-type FeSi2 added 0.5 wt% SiO2, 10-5.05 at above 750K for n-type FeSi2 added 2wt% SiO2.

철도 역사는 고속, 일반, 광역, 물류역사 등 다양한 부하 환경과 많은 비선형부하 장치들이 도입됨에 따 라 전력품질에 악영향이 발생함으로 이를 반영하여 배전 전력품질을 개선할 필요성이 크게 요구된다. 본 논문에서 는 5개 철도 역사 및 변전건물에 대하여 각종 안내표시장치, LED등, 인버터, 컨버터 등의 증가에 의해 비선형 부 하측에 증가된 역률과 고조파 현황 및 삼성 서초사옥과 성남의료원의 전력품질 개선사례 대해 조사 및 측정과 분 석을 하였다. 전력품질 개선방안으로는 IGBT 소자 스위칭을 통해 역률을 개선하고, 고조파 제거 및 전력불평형 보상을 위해 특수설비(PSD, THF, AHF등)를 운영하는 방안을 제시한다. 본 연구를 바탕으로 전력분야의 전력품 질 개선을 위한 통합유지보수 관리시스템 개발이 필요하다고 판단된다.

Railway stations affect power quality as various load environments such as high-speed, general, wide area, and logistics stations, and many nonlinear load devices are introduced. Therefore, there is a great need to improve the quality of power distribution. In this paper, we investigate, measure and analyze the current status of power factor and harmonics for the increase in the nonlinear load side due to the increase of various information display devices, LED lights, inverters, converters for 5 railway stations and the case of power quality improvement at Samsung Seocho office and Seongnam Medical Center. To improve power quality, we proposes a plan to improve the power factor through IGBT device switching, and to operate special facilities(PSD, THF, AHF, etc.) to remove harmonics and compensate power unbalance. Based on this study, it is judged that it is necessary to develop an intergrated maintenance management system for power quality.

Purpose: This study examined the effects of golf rehabilitation exercise on swing power, swing speed, X-factor and club head speed between novice and expert golfer. Methods: The participants were 12 novice and 12 experts. They participated in a golf rehabilitation exercise program for 6 weeks. This program consisted of 5 steps and 4 items (sleeper stretch, full side plank, push-up to plank, high plank knee unders). A three-dimensional motion analyzer was used to measure the X-factor (angle between shoulder and pelvis at top of backswing). Primus RS was used to measure the swing power and swing speed. The golf simulator was used to measure the clubhead speed. In the study, we compared the dependent variables before and after the exercise between the novice and expert. Results: Swing power, swing speed, X-factor, and clubhead speed were significantly increased after the exercise in both groups. There was no significant difference in swing power, swing speed, and X-factor between the groups, but the clubhead speed of expert golfers was significantly increased than that of the novice. Conclusion: This study exhibits that the rehabilitation exercise for golfers was effective for increasing swing power, swing speed, X-factor, and club head speed for both novice and expert golfers.

Background: The radionuclides released by the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident 9 years ago are still being monitored by various research teams and the Japanese government. Comparison of different surveys’ results could help evaluate the exposure doses and the mechanism of radiocesium behavior in the urban environment in the area. In this study, we clarified the relationship between land use and temporal changes in the ambient dose rates (air dose rates) using big data. Materials and Methods: We set a series of 1 × 1 km2 meshes within the 80 km zone of the FDNPP to compare the different survey results. We then prepared an analysis dataset from all survey meshes to analyze the temporal change in the air dose rate. The selected meshes included data from all survey types (airborne, fixed point, backpack, and carborne) obtained through the all-time survey campaigns. Results and Discussion: The characteristics of each survey’s results were then evaluated using this dataset, as they depended on the measurement object. The dataset analysis revealed that, for example, the results of the carborne survey were smaller than those of the other surveys because the field of view of the carborne survey was limited to paved roads. The location factor of different land uses was also evaluated considering the characteristics of the four survey methods. Nine years after the FDNPP accident, the location factor ranged from 0.26 to 0.49, while the half-life of the air dose rate ranged from 1.2 to 1.6. Conclusion: We found that the decreasing trend in the air dose rate of the FDNPP accident was similar to the results obtained after the Chernobyl accident. These parameters will be useful for the prediction of the future exposure dose at the post-accident.

제안된 회로는 교류 입력 전원부와 무손실 스너버 회로가 부가된 DC-DC 컨버터와 DC-AC 변환을 위한 인버터로 구성하였다. 변환된 등가회로를 이용하여 형광램프의 특성을 만족시킬 수 있는 최적의 회로상수를 결정해서 설계함으로써 기존의 인버터 직류측에서 발생되는 맥동주파수에 의한 왜형파 발생을 제거하고 인버터의 입력전류를 불연속이 되도록 하므로써 맥동율과 스위칭 손실을 현저히 감소시켰다. 이러한 모든 결과를 증명하기 위하여 40 W 직관형 형광램프를 대상으로 실험하여 고조파의 발생을 측정한 결과 제안된 전자식 안정기의 우수성을 확인하였다.

Proposed electronic ballast circuit for harmonic reduction includes adding lossless snubber circuit to DC-DC converter. To get inverter for changing DC-AC, a lamp has been changed to equivalence resistance in the standard lamp voltage and current data, also inverter circuit has been interpreted by being changed to R, L, C equivalence circuit. Using converted equivalent circuit, the most suitable circuit constant which can satisfy the characteristics of fluorescent lamps has been decided on and finally designed. It could not only eliminate distortion waveform from pulsation frequency in inverter direct side current but also reduce considerably pulsation rate and switching loss by making input current of inverter discontinuous. The validity for the results of this study has been verified through the experiment to measure harmonic occurrence after applying a newly-manufactured product of electronic ballast to 40 W line tube style fluorescent lamps.

This study was performed to investigate the effect of low power laser irradiation on epidermal growth factor(EGF) expression in the burned skin of the rats. Burns of about 3cm in diameter were created with 75'c water on the back of the rats, and the lesion of experimental group were irradiated on days 1, 2, and 3 postwounding. Control tensions were not irradiated. After burns, low power laser irradiation was applied by using 1000Hz, 830nm GaAlAs (Gallium-aluminum- arsenide) semiconductor diode laser. The expression of epidermal growth factor evaluated immunohistochemistry on mouse anti-EGF. The results of this study were as follows 1. In expression of EGF, the lesion of experimental group made EGF to more induce significantly than control tensions. 2. EGF immunoreactivity in burned skin were increased markedly 3 days after burns, and increased gradually from 1 day to 2 days in burns which is laser irradiation These data suggest that low power laser have wound healing effect in the burned skin of the rats.

The current paper proposes fast distributed constrained power control (FDCPC) with a non‐stationary relaxation factor as the next power update for CDMA cellular power control systems. A review is also given of unconstrained control algorithms: distributed power control (DPC), unconstrained second‐order power control (USOPC), and DPC with a stationary relaxation factor (DPCSRF). To improve the performance of outage probability convergence, DCPC with a non‐stationary relaxation factor (FDCPC) is proposed. Under constrained conditions, the convergence rate of FDCPC is shown to outperform that of DCPC and constrained second order power control(CSOPC).

Fama and French(1993)의 3요인 모형은 미국을 비롯한 여러 나라 증권시장에서 유용한 설명력을 가지고 있는 것으로 검증되어 왔다. 하지만, 국내 주식시장에서는 HML의 횡단면적 설명력이 유의하지 않다라는 결과를 여러 연구들이 보여주고 있고, 또한 1990년대 이후로 갈수록 SMB와 HML이 상당히 큰 절대값의 상관관계를 보이고 있다는 사실 등을 감안할 때, 적어도 국내 주식시장의 공통적인 변동을 설명하기 위해 Fama-French 3요인 모형을 사용하는 것이 과연 적절한가에 대한 의문이 제기된다. 따라서 본 연구에서는 주식거래회전율(Turnover)을 유동성위험의 측정치로 하는 모방포트폴리오를 구성하여 시장위험포트폴리오, SMB와 함께 모형에 포함시켜 대안적(Alternative) 3요인 모형을 구성한 후 국내 주식시장을 분석해 본 결과, 이 대안적 3요인 모형이 Fama-French 3요인 모형보다 더 우월한 설명력을 보였을 뿐 아니라, Turnover 요인 또한 횡단면적으로 유의한 설명력을 가지고 있다는 사실을 발견하였다. 이러한 현상은 표본기간을 2000년 이전과 이후로 나눈 두 기간 모두에서 나타났으며, 2000년 이후의 기간에서 Turnover 요인의 횡단면적 설명력은 더 강하게 나타났다. 이것은 적어도 국내 주식수익률의 변동을 설명하는 공통위험요인으로 시장위험프리미엄, SMB와 함께 유동성 위험요인이 HML보다 더 비중 있게 고려되어야 함을 의미하는 것으로 볼 수 있다.

Fama and French (1993) propose a three-factor asset pricing model which uses a proxy for the market portfolio and mimicking portfolios designed to capture the size and book-to-market effects in stock returns. Empirical applications of this threefactor model in Korea, however, can be problematic because i) the book-to-market effect in the cross section of stock returns is not significant, and ii) the size factor (SMB) and the book-to-market factor (HML) are highly correlated. In this paper, we propose a three-factor asset pricing model which uses a mimicking portfolio designed to capture liquidity risk in place of HML as an alternative to the Fama-French threefactor model. We find that our alternative model performs better than the Fama- French model in explaining the cross section of average stock returns in primarily due to the significant explanatory power of the proposed liquidity factor proxy. The results are robust in both sub-samples (before and after the year 2000), and the significance of the liquidity factor proxy is stronger for the post-2000 sample period.

본 연구는 SNS를 통한 마케팅커뮤니케이션으로 신규브랜드의 인지도 구축이 가능할 것인가에 대한 것으로, 실무에 사용되는 티핑포인트 개념을 근거로 하였다. 연구결과를 통해 다음과 같은 시사점을 제시한다. 첫째, SNS를 통해 노출되는 제품이나 브랜드 정보에 대한 소비자들의 반응은 대중성이 있는 제품보다는 소수의 사용자들끼리 정보를 주고받는 비대중성 제품에 호응도가 더 높았다. 둘째, SNS를 통한 정보노출 및 커뮤니케이션의 특징은 정보수용자의 상황적 관여가 메시지 노출의 기회와 메시지에 대한 인게이지먼트를 조절한다. 셋째, SNS를 통해 노출된 브랜드 및 제품 정보에 대한 소비자들의 구전의도는 브랜드 인지도나 구매의도보다 높았는데, 이는 SNS가 구전확장의 채널로서 효과적이라는 방증이다. 본 연구결과는 시장진입에 어려움을 겪고 있는 개인 및 중소상인들이 광고 및 마케팅 활동을 효율적으로 전개할 수 있는 근거로 활용하기를 제안한다.

This study seeks to find the possibility of building brand awareness by marketing communication using social network service (SNS). This study is based on tipping point used in practical area. The results are as follows. First, the response of consumers into a non popular brand exposed by SNS is more higher than into a popular brand used by a few consumers. Second, situational involvement of consumers moderated message exposure and engagement against message. Third, intention to word of mouth toward brand and product by SNS is higher than brand awareness and intention to purchase. This indicated that SNS is an effective channel for word of mouth. This study provided SNS is efficient marketing tool for individual and medium scale company.

In this thesis, a boost chopper using PV (Photovoltaics) system and PWM (Pulse Width Modulation) voltage type power converter were constructed to provide a pleasant environment to the patients in the hospital wards by controlling temperature, humidity and air-conditioning & heating. For the stable modulation of solar cell, synchronizing signal and control signal were processed using one chip microprocessor. Power converter system was constructed with booster chopper and voltage source inverter and test was carried out for both devices. Constant voltage control method was used to track a maximum power point at boost converter control. For the inverter control, synchronizing signal and control signal were processed by microprocessor for the stable modulation according to the switching theory of SPWM (Sinusoidal Pulse Width Modulation) and directions to each sector. Test was carried out for inverter control using SPWM control method. In addition, grid voltage was detected and this grid voltage and inverter output were operated at the same phase for the phase locking with PWM voltage source inverter so that surplus power could be linked to grid. This characteristic was applied on the temperature and humidity sensors in the general buildings and buildings having specific purposes such as hospitals. The good dynamic characteristic of inverter could be obtained by these applications. Also, PWM voltage inverter maintains a high power factor and low-frequency harmonic output so that power can be supplied in the load as well as system.

This paper proposes fluorescent electronic ballast with high power factor and low line input current harmonics. The system performance can be improved by a charged pump circuit. Details of design and circuit operation are described. The proposed electronic ballast is modified from single - stage half bridge class D electronic ballast by adding capacitor parallel with each power switch and setting the circuit parameter to operate under class DE inverter condition. By using this proposed method the DC bus voltage can be reduced around by 50% compare with conventional class D inverter circuit. Because the power switches are operated at zero voltage switching condition and low dv/dt of class DE switching. The experimental results show that the proper frequency of the prototype is around 50 kHz with input power factor of 0.982, THDi 10.2% at full load and efficiency of more than 90%.

In this paper, the proposed system is to improve power factor of switched reluctance drive and also battery charging capability in regenerative mode of a two-stage power converter based on current source rectifier (CSR). At the CSR stage in the input of SRM converter, eliminate dc link's capacitors and the charging capability of energy saving in regenerative operation mode of SRM drive. And also it controls the speed and current. This paper describes the design of new converter, consisting of half-bridge IGBT modules and Current source rectifiers with battery charging capability of SRM for closed loop control of switched reluctance drive are proposed. The validity and effectiveness of the proposed approach is shown by MATLAB /simulation.

This paper presents a single-stage LED converter with high power factor. The proposed converter utilizes a single-stage power circuit that combinesthe boost DC-DC converter topology and theflyback converter topology. The control of the proposed converter operates using critical conduction mode and fixed on-time voltage control techniques. In this way the proposed converter is much simpler than currentconventional LED converters. An operational principle and a design example of the proposed converter are explained, briefly. Also, it is shown through experimental results that the proposed converter built based on the design example has good performance for driving LEDs.

본 논문에서는 SMPS(Switch-Mode Power Supply)의 역률을 개선할 수 있는 power factor correction(PFC) IC를 설계하였다. 설계된 PFC IC에는 전원장치의 power MOSFET을 구동할 수 있는 기능 이외에도 과전압, 과전류 및 단락보호 기능이 포함되어 있다. 또한 시스템이 대기상태에 있는 경우, 전압 및 전류 feedback 제어에 의해 효과적으로 대기전력을 절감할 수 있도록 설계하였다. 설계된 PFC IC는 시스템이 대기상태에서 일정시간동안 부하변동이 없을 경우 이를 감지하여 자동으로 시스템을 off 시켜 대기전력 소모를 최소화 하는 기능을 포함하고 있다.

In this paper, we design and implement the monolithic power factor correction IC for system power modules using a high voltage(50V) CMOS process. The power factor correction IC is designed for power applications, such as refrigerator, air-conditioner, etc. It includes low voltage logic, 5V regulator, analog control circuit, high-voltage high current output drivers, and several protection circuits. And also, the designed IC has standby detection function which detects the output power of the converter stage and generates system down signal when load device is under the standby condition. The simulation and experimental results show that the designed IC acts properly as power factor correction IC with efficient protective functions.

In this paper, we design and implement the monolithic zero crossing detection power factor correction IC using a high voltage 30V BCD process. The ZCD PFC IC is designed for power applications, such as notebook, LCD monitor, etc. It includes power factor correction function and several protection circuit, regulator, high-voltage high current output drivers. And also, the designed IC has restart timer function which the output pulse is generated if the output signal of IC is not in a 200us. The simulation results show that the designed IC acts properly as power factor correction IC with efficient protective functions.