• 제목/요약/키워드: Comparison Research

검색결과 15,459건 처리시간 0.045초

Z-Source Inverter with SiC Power Semiconductor Devices for Fuel Cell Vehicle Applications

  • Aghdam, M. Ghasem Hosseini
    • Journal of Power Electronics
    • /
    • 제11권4호
    • /
    • pp.606-611
    • /
    • 2011
  • Power electronics is a key technology for electric, hybrid, plug-in hybrid, and fuel cell vehicles. Typical power electronics converters used in electric drive vehicles include dc/dc converters, inverters, and battery chargers. New semiconductor materials such as silicon carbide (SiC) and novel topologies such as the Z-source inverter (ZSI) have a great deal of potential to improve the overall performance of these vehicles. In this paper, a Z-source inverter for fuel cell vehicle application is examined under three different scenarios. 1. a ZSI with Si IGBT modules, 2. a ZSI with hybrid modules, Si IGBTs/SiC Schottky diodes, and 3. a ZSI with SiC MOSFETs/SiC Schottky diodes. Then, a comparison of the three scenarios is conducted. Conduction loss, switching loss, reverse recovery loss, and efficiency are considered for comparison. A conclusion is drawn that the SiC devices can improve the inverter and inverter-motor efficiency, and reduce the system size and cost due to the low loss properties of SiC devices. A comparison between a ZSI and traditional PWM inverters with SiC devices is also presented in this paper. Based on this comparison, the Z-source inverter produces the highest efficiency.

2017년 한국 보건의료의 상대적 위치와 추이: 경제협력개발기구 국가와 비교 (Position Value for Relative Comparison of Healthcare Status of Korea in 2017)

  • 이현지;오소연;박은철
    • 보건행정학회지
    • /
    • 제30권1호
    • /
    • pp.131-138
    • /
    • 2020
  • The purpose of this study was to compare the health status of South Korea with those of Organization for Economic Cooperation and Development (OECD) countries and examine the trends. Position vAlue for Relative Comparison (PARC) was used as a gauge for comparison, and five sectors of the health care system were measured: demand, supply, accessibility, quality, and cost. The Mann-Kendall test was used as a statistical analysis method to examine trend of PARC values obtained from 2000 to recent years. According to the results, the demand, supply, accessibility, and quality sectors were higher than the OECD average, while the cost was lower than the average. However, there is a recent trend of sharp increases in health care costs. Some indicators: health employment, quality of primary care and mental health care were lower than the OECD average, and health determinants showed a worsening trend. Therefore, policy-makers need to take this into account and make efforts for sustainable health care.

중국 및 국내 거주 한국인의 체형 비교 연구 -20대 남성을 중심으로- (The Research on the Body Type Comparison between the Koreans Living in China and the Ones in Korea - Focused on Male in Their Twenties -)

  • 석혜정;임순
    • 한국의류학회지
    • /
    • 제28권9_10호
    • /
    • pp.1219-1230
    • /
    • 2004
  • This study was conducted to compare the physical shapes of Korean males in their 20s between those residing in Yenbien, China and those living in Korea. Measurements were checked fur 57 items on 167 Korean male residents in Yenbien, China and 295 Korean male residents in Seoul and the other large cities around it. The conclusions are as follows: 1. The comparison of 58 items in physical measurements of Korean male residents in China and those in Korea showed differences in 49 items. Korean male residents in China had the smaller physical shapes short in limbs and height. 2. The comparison of the factor analysis results for physical measurements did not reveal big differences. In terms of the contribution of variables, however, obesity played an exceptionally large role fur Korean residents in China, while the importance of obesity and vertical length were similar for those in Korea. 3. The comparison of the physical shapes according to the grouping resulted in three types each for both groups, with different features for individual types. Korean residents in China were grouped according to the obesity factor rather than the changes in height, while those in Korea were classified according to both vertical length and obesity.

경화 콘크리트의 배합비 추정기법 개발에 관한 실험적 연구 (The Experimental Study on the Development of Estimation Technique for the Mix Proportion of Hardened Concrete)

  • 이준구;박광수;김석열;김명원;김관호;박미현
    • 한국콘크리트학회:학술대회논문집
    • /
    • 한국콘크리트학회 2000년도 가을 학술발표회 논문집(II)
    • /
    • pp.961-966
    • /
    • 2000
  • It is difficult to change or remedy concrete structure after hardened. It is usual to evaluate the quality of hardened concrete using several test method. This study was performed to make fundamental data that could be used to evaluate the quality of hardened concrete. This study is to estimate mix proportion of hardened concrete. Each elements of concrete needed different estimation methods. First, the cement that handled by the most important compounds measured by XRF(X-ray fluorecence) machine with scanning Ca-K${\alpha}$. Second, the coarse aggregate that divided by maximum size measured by the area comparison method that starts from the assumption of uniform distribution. Third, the fine aggregate measured by the weight comparison method that needs several prerequsite constants which concerned cement hydration reaction. Fourth, the water content would be estimated by expert system that has data base of design data, the contents of above estimation results, the characteristics of concrete strength. As the result of the above research, some conclusions are as follows. The cement estimation method resulted by reliability of mean 96.7%, standard deviation 3.92. The area comparison method resulted by reliability of mean 95.3%, standard deviation 2.08. The weight comparison method resulted by reliability of mean 93.3%, standard deviation 3.35.

Comparison of Totally Prefabricated Bridge Substructure Designed According to Korea Highway Bridge Design (KHBD) and AASHTO-LRFD

  • Kim, Tae-Hoon
    • International Journal of Concrete Structures and Materials
    • /
    • 제7권4호
    • /
    • pp.319-332
    • /
    • 2013
  • The purpose of this study was to investigate the design comparison of totally prefabricated bridge substructure system. Prefabricated bridge substructure systems are a relatively new and versatile alternative in substructure design that can offer numerous benefits. The system can reduce the work load at a construction site and can result in shorter construction periods. The prefabricated bridge substructures are designed by the methods of Korea Highway Bridge Code (KHBD) and load and resistance factor design (AASHTO-LRFD). For the design, the KHBD with DB-24 and DL-24 live loads is used. This study evaluates the design method of KHBD (2005) and AASHTO-LRFD (2007) for totally prefabricated bridge substructure systems. The computer program, reinforced concrete analysis in higher evaluation system technology was used for the analysis of reinforced concrete structures. A bonded tendon element is used based on the finite element method, and can represent the interaction between the tendon and concrete of a prestressed concrete member. A joint element is used in order to predict the inelastic behaviors of segmental joints. This study documents the design comparison of totally prefabricated bridge substructure and presents conclusions and design recommendations based on the analytical findings.

다중지능을 활용한 학습이 학생들의 과학탐구능력 및 과학적 태도에 미치는 효과 (The Effects of the Science Process Skill and Scientific Attitudes by multiple-Intelligence)

  • 홍순원;이용섭
    • 대한지구과학교육학회지
    • /
    • 제3권1호
    • /
    • pp.76-85
    • /
    • 2010
  • The purpose of this study is to examine the effect of higher grades in elementary the science process skill and scientific attitudes by multiple-intelligence. To verify research problem, the subject of this study were sixth-grade students selected from two classes of an elementary school located in U1san : the search group is composed of twenty-nine students who were participated in multiple-Intelligence situation, and the other is composed of thirty-two students(comparison group) who were participated in teacher map based learning situation. During six weeks, the multiple-Intelligence was executed in th search group while the teacher map based instruction in comparison group Post-test showed following results: First, the search group showed a significant improvement in the science process skill compared th the comparison group. Second, the search group did not showed a significant improvement in the scientific attitudes compared th the comparison group. In conclusion, multiple-Intelligence teaching model was more effective than the teacher map based teaching model on science process skill. However, since the study has a limit on an object of the study and the applied curriculum, the additional studies need to be conducted with an extended comparative group and curriculum.

  • PDF

영양상담을 위한 전산화 프로그램 개발연구 (Development of computer programs for Nutrition Counseling)

  • 홍순명
    • Journal of Nutrition and Health
    • /
    • 제22권4호
    • /
    • pp.275-289
    • /
    • 1989
  • The purpose of this study is to develop a computer system with data file and computerized programs for nutrition counseling. In this research, a 16 / XT personal computer (word : COBOL) compatible with IBM-PC/XT was used. Computer system developed for this study was as follows: Data files(food composition list, food exchange list, nutrition management comment, special diet therapy) were used for analysis the nutritional status and the ntrition education comment. (1) Programs for the nutritional status assessment 1) General information a) Name, age, sex, higher, weight, activity, disease and special diet b) Ideal body weight and Obesity assessment(Kaup index and Broca index) c) Rest and athletics status d) Biochemical data comparision with standard 2) Food Intakes 3) Nutrient Intakes a) Comparison of the amounts intaked with the recommended dietary allowances for present weight. b) Comparison of the energy composition rate intaked with the recommended dietary allowances for present weight. b) Comparison of the energy composition rate intaked with the recommended for present weight and ideal weight. c) Nutrient analysis by each meal and snack. 4) Food intakes from each food group and comparison with recommended 5) Special nutrient analysis. (2) Programs for the nutrition education based on nutritional status assessment. 1) Suggestion of number of food exchange group 2) Nutritional assessment and advise comments 3) Nutritional management comments 4) Special diet therapy In the study, the nutritioal status and nutrition education comments are based on individual data from nutrition counseling.

  • PDF

2019년 한국 보건의료의 상대적 위치와 추이: 경제협력개발기구 국가와 비교 (Position Value for Relative Comparison of Healthcare Status of Korea in 2019: Comparison with Countries of the Organization for Economic Cooperation and Development)

  • 박민아;윤흰뫼;박은철
    • 보건행정학회지
    • /
    • 제32권1호
    • /
    • pp.113-121
    • /
    • 2022
  • This study aims to compare the healthcare status of South Korea and other member of the Organization for Economic Cooperation and Development (OECD) using the OECD health statistics 2021. We used the position value for relative comparison (PARC) index to measure the five elements of the healthcare system, demand, supply, accessibility, quality, and cost. For the statistical analysis, Mann-Kendall test was performed to examine the trend of the PARC values from 2000 to the most recent year. The results showed that supply, demand, accessibility, and quality were above median than the OECD median and the cost was below median. In sectors such as primary care, health employment and mental health care were below median average. With these result, necessary steps for a sustainable healthcare should be taken into effort by policy makers.

Evaluation and Comparison of the Solubility Models for Solute in Monosolvents

  • Min-jie Zhi;Wan-feng Chen;Yang-bo Xi
    • Korean Chemical Engineering Research
    • /
    • 제62권1호
    • /
    • pp.53-69
    • /
    • 2024
  • The solubility of Cloxacillin sodium in ethanol, 1-propanol, isopropanol, and acetone solutions was measured at different temperatures. The melting property was also tested by using a differential scanning calorimeter (DSC). Then, the solubility data were fitted using Apelblat equation and λh equation, respectively. The Wilson model and NRTL model were not utilized to correlate the test data, since Cloxacillin sodium will decompose directly after melting. For comparison purposes, the four empirical models, i.e., Apelblat equation, λh equation, Wilson model and NRTL Model, were evaluated by using 1155 solubility curves of 103 solutes tested under different monosolvents and temperatures. The comparison results indicate that the Apelblat equation is superior to the others. Furthermore, a new method (named the calculation method) for determining the Apelblat equation using only three data points was proposed to solve the problem that there may not be enough solute in the determination of solubility. The log-logistic distribution function was used to further capture the trend of the correlation and to make better quantitative comparison between predicted data and the experimental ones for the Apelblat equation determined by different methods (fitting method or calculation method). It is found that the proposed calculation method not only greatly reduces the number of test data points, but also has satisfactory prediction accuracy.

색도 측정방법의 적합성 평가 (Conformity Assessment of Color Measurement Methods)

  • 정관조;조범수;송만식;박현;이종규;최영준
    • 대한환경공학회지
    • /
    • 제35권6호
    • /
    • pp.442-448
    • /
    • 2013
  • 물속의 색도 측정방법에는 비색법과 분광학적방법이 있다. 비색법은 농도가 알려진 백금-코발트 표준용액과 시료의 색을 비교하여 색도를 측정하는 방법이며 분광학적 색도 측정방법은 단일 또는 다중파장을 선택하여 색도를 측정하는 방법이다. 그러나 비색법의 경우, 분석자의 시력에 의한 단순 비교를 통해 색도를 측정하는 방법으로 측정결과의 신뢰성과 재현성이 우수하지 못할 뿐만 아니라 5 TCU 이하의 색도 측정이 불가능하다. 분광학적 색도 측정방법 중 단일파장법은 주로 색도 성분이 천연유기물질(휴믹물질)인 지표수나 지하수에만 적용이 가능한 것으로 나타났으며 하수와 같이 인위적인 화학적 색도 성분이 함유될 경우 색도 측정이 불가능하였다. 다중파장법은 지표수, 하수 등 다양한 시료에 대해 우수한 색도 측정결과를 나타냈으나 1개의 시료에 대해 수십 번의 측정과 복잡한 계산으로 실제 현장 적용에 어려움이 있었다. 따라서 본 연구에서는 지표수, 정수, 하수 등 다양한 시료에 대해 신속하고 정확한 색도 측정방법을 비교하였다. 그 결과, 다중파장 프로그램이 내장되어 3~4초 이내에 지표수, 하수 등 다양한 시료에 대해 신속하고 정확하게 색도 측정이 가능한 색도계 색도 측정방법이 가장 적합한 것으로 나타났다.