• 제목/요약/키워드: duty factor

검색결과 363건 처리시간 0.027초

3상 Z-소스 PWM 정류기의 입력 AC 전압 센서리스 제어 (Input AC Voltage Sensorless Control for a Three-Phase Z-Source PWM Rectifier)

  • 한근우;정영국;임영철
    • 전기학회논문지
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    • 제62권3호
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    • pp.355-364
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    • 2013
  • Respect to the input AC voltage and output DC voltage, conventional three-phase PWM rectifier is classified as the voltage type rectifier with boost capability and the current type rectifier voltage with buck capability. Conventional PWM rectifier can not at the same time the boost and buck capability and its bridge is weak in the shoot- through state. These problems can be solved by Z-source PWM rectifier which has all characteristic of voltage and current type PWM rectifier. By shoot-through duty ratio control, the Z-source PWM rectifier can buck and boost at the same time, also, there is no need to consider the dead time. This paper proposes the input AC voltage sensorless control method of a three-phase Z-source PWM rectifier in order to accomplish the unity input power factor and output DC voltage control. The proposed method is estimated the input AC voltage by using input AC current and output DC voltage, hence, the sensor for the input AC voltage detection is no needed. comparison of the estimated and detected input AC voltage, estimated phase angle of the input voltage, the output DC voltage response for reference value, unity power factor, FFT(Fast Fourier Transform) of the estimated voltage and efficiency are verified by PSIM simulation.

사회복지시설의 민간자원 동원에 영향을 주는 요인 분석: 후원을 중심으로

  • 김미숙
    • 한국사회복지학회:학술대회논문집
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    • 한국사회복지학회 2004년도 춘계학술대회 자료집
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    • pp.261-297
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    • 2004
  • Social welfare facilities where provide the socially disadvantaged with proper social services, face financial difficulties. This is because not only of the lack of governmental support, but also of social welfare facilities' lack of skills in developing abundant resources from the private sector. In this context, this study tried to find factors affecting resource mobilization of the social welfare facilities to devise policies in resource development. Mail survey was conducted with the structured questionnaire. Employees in charge of community resource development were asked to answer the questionnaire. The study population were two types of welfare facilities: community welfare centers and residential care facilities. A total of 293 community welfare centers and 632 residential care facilities responded to the survey. The response rate was about 62%. The dependent variable of the study was the amount of resource mobilization in the year 2001 which was measured as the number of donors, the total amount of donation, and estimated amount of gift-in-kind. Three types models were constructed per each welfare facility. Independent variables were selected based on the previous research findings: community environment factor, structural factor, and resource development factor. Multiple regression was utilized to analyze the data. The resource development factor turned out to be significant variable in various models. In the models of donors, the amount of donation, and the amount of gift-in-kind, at least one out of four variables in the resource development factor was significant. Welfare centers which establish the resource development department or hire employees to take care of resource development, and adopt computer software in managing donors, receive more donations than their counterparts. Interestingly, the centers where employees take the responsibility of resource development as well as other responsibilities (dual duty), did not have more resources mobilized than those with no employees for resource development. Using computer software in managing donors turned out to be a significant variable in many models, except for the donor model. In addition, residential care facilities located in urban area have more donors and donations, and among residential facilities those for the elderly, children, and the mentally retarded and those hiring more employees, receive more donations than those for the disabled and those hiring less employees. As for the gift-in-kind model, the centers located in high income area and residential facilities for the elderly, women and mentally retarded receive less gift-in-kind than those for the disabled. Based on the above findings, this study suggested that to mobilize resources the welfare centers as well residential care facilities need to have community resource development department or resource development staffs, and adopt computer software to systematically organize donors.

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패밀리레스토랑 조리 종사원의 이직원인에 관한 연구 (Study on The Turnover Reason of Family Restaurant Cook Part Employee)

  • 유양자;윤지연
    • 한국식품조리과학회지
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    • 제17권1호
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    • pp.13-22
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    • 2001
  • 서울시내에 소재하고 있는 패밀리레스토랑 중 7개 업체 12개 점포의 조리 부서에 근무하는 147명을 대상으로 성별, 연령, 학력, 직위, 재직기간에 의한 이직 원인의 차이를 분석한 결과는 다음과 같다. 1. 패밀리레스토랑 조리 부서 직원은 남성이 60명, 여성 87명으로 구성되어 있고, 20-29세가 차지하는 비율이 95.2%로 가장 많았다. 학력은 2년제 대졸 여성의 비율은 50.3%로 패밀리레스토랑 조리 부서 직원의 반 이상을 차지하고 있는 것으로 나타났다. 직위는 매니저 4.1%, 캡틴 13.6%, 직원 82.3%로 나타났으며, 재직기간은 2년 이하가 84.4%로 나타났다. 2. 성별에 따른 이직의 원인 차이를 분석한 결과는 여성(3.06)이 남성(3.00)에 비해 이직요인에 대한 전체 평균이 다소 높은 것으로 나타났다. 3. 연령에 따른 패밀리레스토랑 조리 부서 종사자들의 이직 원인 차이는 전체적으로 50세 이상의 연령층(3.039)에서 이직에 대해 심각하게 받아들이고 있으며, 그 중 근무지 요인(4.000)과 경영불신 요인(4.000)이 가장 영향력 있는 변수로 나타났다. 4. 학력에 따른 이직의 원인 차이를 분석한 결과, 국내 석사 이상의 학력을 가진 종사자가 대부분의 요인에서 높게 나타났다. 통계적으로 유의한 차이를 보인 요인으로는 근무 체계 요인(0.001), 타진로 모색요인(0.005), 개인적 문제 요인(0.034), 거주지 요인(0.014)로 모두 F값이 3.04보다 크게 나왔다. 5. 직위에 따른 이직 원인 요인별 차이를 분석한 결과, 근무체계 요인 캡틴급(3.63), 내부적 문제 요인매니저급(3.21), 조직내 인간관계 요인 캡틴급(3.45), 타진로 모색 요인 매니저급(3.17), 개인적 문제 요인 매니저급(3.22), 거주지 문제 요인 캡틴급(2.88), 경영불신 요인 캡틴급(3.20), 근무환경 요인 캡틴급(3.08)에서 가장 높게 나타났다. 6. 재직기간에 따른 이직 원인 요인별 차이를 분석한 결과, 대부분 5년 이상 근무집단이 가정 높게 나타났다. 7. 기타 이직에 관한 견해의 차이를 성별로 분석한 결과, 이직 현상이 현재와 같이 지속될 것이라고 예상되는지의 여부에 대해서 대부분(85.0%)이 그럴 것이라고 응답했고, 이직이 소멸될 것이라고 생각하는지의 여부에 대해서도 소멸되지 않을 것이라고 대답한 응답자가 85.0%였다. 현재 재직 중인 직장이 어떻게 되길 바라는지 여부에 대해서는 대부분(91.2%) 잘되기를 바란다고 응답했다. 8. 전체적으로 각 이직 원인 요인 중에 가장 높은 평균값이 나타난 요인은 근무체계 요인(3.45)이였고, 조직내 인간관계 요인(3.18), 타진로 모색 요인(3.11), 경영불신 요인(3.04) 순서였다. 나머지 요인들은 3점(보통이다) 이하로 이직에 큰 영향을 미치지 않는 것으로 나타났다. 이상의 결과에서 패밀리레스토랑 조리 부서 종사원은 높은 이직 성향이 보여 전문 인력 부족 현상을 겪고 있는 외식업계에서 이직이라는 문제가 여전히 해결해야할 중대한 과제로 남아있음을 시사하고 있다. 남성에 비해 높은 여성의 이직 성향은 근무 여건에 있어 성 차별적 요소의 잔재에 대해 간과할 수 없음을 보여주고 있으며, 자신의 직업에 대해 안정기로 접어들어야 할 50세 이상의 연령층에서 가장 높은 이직 성향을 보이고 있는 것이나, 5년 이상 근속한 종사자의 높은 이직 성향, 그리고, 매니저급에서의 높은 이직 성향은 국내 외식업계가 평생 직장으로서의 위치까지 오르지 못하고 있음을 간접적으로 보여주고 있다.

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Ni-P 합금의 전기전도도와 경도에 대한 도금 조건의 영향 (Effect of Electroplating Parameters on Conductivity and Hardness of Ni-P Alloy)

  • 김남길;선용빈
    • 마이크로전자및패키징학회지
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    • 제24권3호
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    • pp.77-81
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    • 2017
  • Pulse electroplating of Ni-P alloy was studied to fulfill the material requirement to the advanced vertical probe tip in wafer probe card. The major concerns are for the electrical conductivity and yield strength. Plating parameters such as current density, duty cycle and solution components were examined to obtain the nanocrystal structure and proper percentage of phosphorus, leading to how to control the nanocrystal grain growth and precipitation of $Ni_3P$ after heat treatment. Among the parameters, the amount of phosphorus acid was the main factor affecting on the grain size and sheet resistance, and the amount of 0.1 gram was appropriate. Since hardness in Ni-P alloy is increased by as-plated nanocrystal structure plus precipitation of $Ni_3P$, the concentration of P less than 15 at% was better choice for the grain coarsening without minus in hardness value. The following heat treatment made grain growth and dispersion of precipitates adjustable to meet the target limit of resistance of $100m{\Omega}$ and hardness number of over 1000Hv. The Ni-P alloy will be a candidate for the substitute of the conventional probe tip material.

SCR 및 LNT가 적용된 Euro-6 소형 경유차의 실제도로 주행과 인증모드에서의 CO2 및 NOx 배출특성의 비교 (Characteristics of Real-Driving CO2 and NOx Emissions Compared to Test Modes on Euro-6 LDVs Equipped with SCR and LNT)

  • 이종태;김정수;전문수;차준표
    • 한국분무공학회지
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    • 제21권4호
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    • pp.200-206
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    • 2016
  • Recently, the certification procedure for exhaust emission regulation of LDV has tested with the NEDC mode in the laboratory. But the on-road exhaust emissions exceed the standard emission limits. Therefore, it is important to analyze the real-driving emissions (RDE) with a portable emissions measurement system (PEMS). In present study, the on-road emissions were measured with a PEMS and evaluated by moving averaging window (MAW) method. Also, it was compared with the $CO_2$ and $NO_x$ emissions for real-driving and test modes from euro-6 light-duty vehicles equipped with SCR and LNT systems. In results, on-road $NO_x$ emission has been 2.3-10.0 times higher than the standard $NO_x$ emission limit on NEDC mode. The reason was that the test modes did not reflect traffic and various real-driving patterns sufficiently.

Countermeasures of Specimens Showing below Reference Value in APTT Result

  • Choi, Hyun Oh;Kim, Seung Gu;Park, Sang Hee;Lee, Jae Ki;Koo, Bon Kyung;Park, Chang Ho
    • 대한임상검사과학회지
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    • 제45권3호
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    • pp.87-90
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    • 2013
  • The activated partial thromboplastin time (APTT) is used primarily to evaluate coagulation abnormalities in the intrinsic pathway. The proper specimen is very important factor for precise results of blood coagulation analysis. The objective of this study was to get to the conclusion of whether to analyze again and to collect blood sample over again when APTT result shows below the reference value. We evaluated 126 samples showing a value below 20.0 sec at ATPT result, which consist of 48 males and 78 females candidates during night duty from March 2012 to December 2012. Average comparisons of APTT result between first and retested analysis among study subjects were significantly different in male samples. APTT results comparison of recollected subjects among clotted samples were also significantly different with both sexes (p<0.000). We suggest that we should carefully check the samples to get accurate results and collect samples again in case of only obtaining improper samples; even though the APTT result show below reference value.

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항해사의 피로도 분석모델에 관한 기초연구 (A Basic Study on the Fatigue Analysis Model for Marine Officers)

  • 양원재
    • 해양환경안전학회지
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    • 제15권3호
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    • pp.217-222
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    • 2009
  • 선박을 운항하는 항해사의 피로도(Fatigue)는 안전항해와 매우 밀접한 관계를 가지고 있다. 또한, 당직항해사의 피로는 중대한 해양사고를 초래할 수 있다. 본 연구에서는 항해사의 근무환경, 피로유발요인 및 피로증세 등에 대하여 문헌조사를 실시하였다. 그리고 실습항해사를 대상으로 졸음, 정신적 육체적 작업부하도에 대한 피로도 관련 설문조사를 실시하고 그 결과를 분석하였다. 마지막으로 이와 같은 피로도 조사 및 설문조사 분석결과를 바탕으로 항해사의 피로도 분석항목을 선정하고 이를 기반으로 향후 항해사의 업무수행능력을 평가하기 위한 피로도 분석모델을 제안하였다.

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빛 이용효율 향상을 위한 광생물반응기 설계 기준에 관한 연구 (A Study on the Design Criteria of Photobioreactor for the Efficiency of Light-Utilization)

  • 류현진;이진석;오경근
    • KSBB Journal
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    • 제19권4호
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    • pp.257-262
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    • 2004
  • 최근, 미세조류에 대한 생물공학적 관심이 급격히 증가하고 있으며 이의 응용범위는 식품이나 제약, 화장품 등 다양한 구도로 확장되어지고 있다. 고농도의 미세조류 배양을 위해서는 빛이 핵심적 제한요소로 작용되어지며 빛의 투과 깊이나 강도에 따라 균체의 성장속도가 결정되어지게 된다. 본 연구에서는 다양한 빛의 투과경로와 빛을 받는 면적/배양액의 부피 비율, 조도 그리고 단계적 조사에 따른 Chlorella sp.의 성장률을 조사하여 빛이 미세조류에 미치는 영향을 알아보았으며, 본 연구에 적용된 값들 중 4 cm의 직경, 57.6%의 면적/부피 비율, 62 $\mu$mo1/$m^2$/s의 조도에서 Chlorella sp. 성장에 필요한 빛 에너지를 가장 효율적으로 이용함을 확인할 수 있었다.

Single Phase Utility Frequency AC-High Frequency AC Matrix Converter Using One-Chip Reverse Blocking IGBTs based Bidirectional Switches

  • Hisayuki, Sugimura;Kwon, Soon-Kurl;Lee, Hyun-Woo;Mutsuo, Nakaoka
    • 대한전기학회:학술대회논문집
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    • 대한전기학회 2006년도 추계학술대회 논문집 전기기기 및 에너지변환시스템부문
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    • pp.125-128
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    • 2006
  • This paper presents a novel type soft switching PWM power frequency AC-AC converter using bidirectional active switches or single phase utility frequency AC-high frequency AC matrix converter. This converter can directly convert utility frequency AC (UFAC, 50Hz/60Hz) power to high frequency AC (HFAC) power ranging more than 20kHz up to 100kHz. A novel soft switching PWM prototype of high frequency multi-resonant PWM controlled UFAC-HFAC matrix converter using antiparallel one-chip reverse blocking IGBTs manufactured by IXYS corp. is based on the soft switching resonance with asymmetrical duty cycle PWM strategy. This single phase UFAC-HFAC matrix converter has some remarkable features as electrolytic capacitor DC busline linkless topology, unity power factor correction and sine-wave line current shaping, simple configuration with minimum circuit components, high efficiency and downsizing. This series load resonant UFAC-HFAC matrix converter, incorporating bidirectional active power switches is developed and implemented for high efficiency consumer induction heated food cooking appliances in home uses and business-uses. Its operating performances as soft switching operating ranges and high frequency effective power regulation characteristics are illustrated and discussed on the basis of simulation and experimental results.

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서울시 주요 터널내 기체상 오염물질 농도 측정 (Measurements of Gaseous Pollutants in Major Tunnels in Seoul)

  • 김영성;경남호;손재익;문길주;김용표;백남준;김태오
    • 한국대기환경학회지
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    • 제9권4호
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    • pp.320-328
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    • 1993
  • Gaseous pollutants in Namsan Nos. 1, 2, and 3 tunnels and Pukak tunnel were measured along the road by an air-monitoring van from the evening of February 9 to the morning of February 12 in 1993. Average concentrations of pollutants in Namsan tunnels were 9.2-13.5 ppm CO and 0.037-0.047 ppm SO$_{2}$. Average concentrations of SO$_{2}$ in Pukak tunnel was 0.79 ppm, higher than those in Namsan tunnels, due to the traffic of heavy-duty buses and trucks. The pollutant concentrations in Namsan tunnesl could be explained by emission of passenger cars using unleaded gasolin and LPG taxies. Average concentration of NO$_{x}$ in Namsan tunnels was at least 1.1 ppm, estimated from the emission factor of pasenger cars using unleaded gasoline. Pollutant concentrations in Namsan No. 3 tunnel were higher at the exit because of the piston action of air mass in the tunnel provided by the traffic. Fans installed at Namsan and Pukak tunnes could be useful, but their flushing action of ambient air in the tunnel was not clearly observed.d.

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