• Title, Summary, Keyword: efficiency

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Wireless Energy Transmission High-Efficiency DC-AC Converter Using High-Gain High-Efficiency Two-Stage Class-E Power Amplifier

  • Choi, Jae-Won;Seo, Chul-Hun
    • Journal of electromagnetic engineering and science
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    • v.11 no.3
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    • pp.161-165
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    • 2011
  • In this paper, a high-efficiency DC-AC converter is used for wireless energy transmission. The DC-AC convertter is implemented by combining the oscillator and power amplifier. Given that the conversion efficiency of a DC-AC converter is strongly affected by the efficiency of the power amplifier, a high-efficiency power amplifier is implemented using a class-E amplifier structure. Also, because of the low output power of the oscillator connected to the input stage of the power amplifier, a high-gain two-stage power amplifier using a drive amplifier is used to realize a high-output power DC-AC converter. The high-efficiency DC-AC converter is realized by connecting the oscillator to the input stage of the high-gain high-efficiency two-stage class-E power amplifier. The output power and the conversion efficiency of the DC-AC converter are 40.83 dBm and 87.32 %, respectively, at an operation frequency of 13.56 MHz.

The slope effect of grade efficiency curve in a two-stage cyclone (등급집진효율 곡선의 기울기가 2단 사이클론의 집진효율에 미치는 영향)

  • Heo, Kwang-Su;Seol, Seoung-Yun;Kim, Min-Ha
    • Proceedings of the KSME Conference
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    • pp.1963-1968
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    • 2004
  • A collection efficiency of cyclone is influenced by cut-size and slope of grade efficiency curve. It has been recognized that the collection efficiency is improved when the cut-size is reduced. However, effects of the slope have never been studied so far. In this study, we analyze a relationship between slope of grade efficiency and collection efficiency in two-stage cyclones. In single stage cyclones, higher slope cyclones have high efficiency. On the contrary to single stage cyclone, collection efficiency of two-stage cyclone have the maximum value when the first cyclone has a lower slope and second cyclone is high.

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A Model of Evaluating the Efficiency of Container Terminals for Improving Service Quality (서비스 품질 향상을 위한 컨테이너 터미널의 효율성 평가 모형에 관한 연구)

  • 임병학;한윤환
    • Journal of the Korean Society for Quality Management
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    • v.32 no.2
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    • pp.77-92
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    • 2004
  • It is difficult but very necessary to measure the productivity of container terminals as logistics service provider. It is meaningful to find the appropriate inputs and outputs of the logistics service delivery systems and to measure the relationship between these inputs and outputs. This study proposes a model of evaluating the efficiency of container terminals. The evaluation consists of three phases. First, DEA(Data Envelopment Analysis) phase, determines the efficiency score and weights of DMUs(Decision Making Unit). This phase performs through four steps : selection of DMU, selection of DEA model, determination of input and output factors, calculation of efficiency score and weights for each DMU. Secondly, CEM (Cross Evaluation Model) phase, is to calculate the cross-efficiency scores of DMUs. This phase performs through three steps: selection of CEM, determination of cross-efficiency score for each DMU and development of cross-efficiency matrix. Finally, average cross-efficiency analysis phase is to compute the average cross-efficiency score. The proposed model discriminates among DMUs and ranks DMUs, whether they are efficient or inefficient.

The Analyses of the Operational Efficiency and Efficiency Factors of Retail Stores Using DEA Model (DEA 모형을 활용한 소매점의 효율성 및 결정요인 분석)

  • Ko, Kyungwan;Kim, Daecheol
    • Korean Management Science Review
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    • v.31 no.4
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    • pp.135-150
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    • 2014
  • This paper analyzes the operational efficiency of 91 individual retail stores in Seoul by a two-step procedure. In the first step, a data envelopment analysis (DEA) model is used to identify the efficiency scores. Three inputs (store size, number of items, and number of employees) and two outputs (sales and number of customers) are used for the efficiency measurement. In the second step, a Tobit regression model is used to identify the drivers of efficiency. DEA efficiency scores are used to test hypotheses on the impact of five independent variables, namely store age, number of items per store size, number of items per employee, trade area index, and number of competitors. Results of the Tobit analysis show that number of items per store size, number of items per employee, and number of competitors play a significant role in influencing the operational efficiency of retail stores. Managerial implications of the study are discussed.

Relationship Between Farm Land Structure and Machine Efficiency

  • Singh, Gajendra;Ahn, Duck-Hyun
    • Proceedings of the Korean Society for Agricultural Machinery Conference
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    • pp.119-128
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    • 1993
  • Effective machine capacity is affected by the physical and geometrical conditions of the fields. In the small and scattered farmland structure field efficiency is greatly influenced by plot geometry. In this paper, a method for estimating field efficiency and effective machine capacity was developed . The developed method was applied to Korean paddy cultivation. Various time elements related to farm operations for small and scattered plots are discussed in this paper . Available working time is divided into two parts, viz. the preparation time for machine operation and actual working time. Two kinds of machine efficiencies, namely , Machine Efficiency 1, applicable on a single large plot or set of well consolidated plots ; and Machine Efficiency 2, applicable on small and scattered multiple plots, are considered. Based assumptions made and steps followed to construct the model are discussed. Effective capacity of each machine based on different plot geometries are calculated y the model. Machine efficiency on a single plot increases with increase in the dimension of longer side of the plot . Low speed, low theoretical capacity machines have higher machine efficiency which is only slightly influenced by plot geometry. As plot geometry is improved , the machine efficiency of high speed, high capacity machines increases rapidly. The effects of short side length and plot size on machine efficiency on a single plot depend on the type of farm operation. For a particular plot shape, as plot size increases, machine efficiency on multiple plots increases rapidly. The effects of consolidation on machine efficiency is highly significant if the plot size is small and/or machine size is large.

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A Study on the Marking Efficiency of Jacket & Slacks by CAD System - Focused on the Check-Pattern - (CAD 시스템 활용을 위한 여자 바지 정장의 Marking 효율 고찰 - 체크무늬 원단 마킹을 중심으로 -)

  • Hong, Eun-Hee;Ryu, Kyoung-Ok;Suh, Mi-A
    • The Research Journal of the Costume Culture
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    • v.18 no.1
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    • pp.13-28
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    • 2010
  • This study is focused on the elucidation of efficient and correct marking methods by comparing and analyzing marker efficiency depending on the marking job condition such as interval of checking-pattern and marker orientation using woman's Jacket and Slacks. Research Method intended to compare the marking efficiency of Jacket and Slacks, check-less and check- patterned materials with the intervals of $1.5{\times}1.5cm$ and $5{\times}5cm$ were selected. First, in the comparison of marking efficiency depending on check-pattern interval, regardless of the direction of marker position, single-item makers and set-item makers, the efficiency of check-less materials was higher than those of check-patterned materials and increasing the intervals decreased marking efficiency and vice versa. Marking efficiency of Slacks was less influenced than marking efficiency of Jacket by check-pattern interval. Second, in the comparison of marking efficiency depending on the direction of marker position, regardless of check-pattern interval and number of maker pieces, the efficiency of nap-up-and-down position was higher than those of nap-one-way position. Third, the marking efficiency of single-item was more effective than one of set-item in all working condition except nap-one-way position in checkless materials.

Exergy analysis of R717 high-efficiency OTEC power cycle for the efficiency and pressure drop in main components

  • Yoon, Jung-In;Son, Chang-Hyo;Yang, Dong-Il;Kim, Hyeon-Uk;Kim, Hyeon-Ju;Lee, Ho-Saeng
    • Journal of the Korea Society For Power System Engineering
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    • v.17 no.5
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    • pp.52-57
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    • 2013
  • In this paper, an analysis on exergy efficiency of high-efficiency R717 OTEC power system for the efficiency and pressure drop in main components were investigated theoretically in order to optimize the design for the operating parameters of this system. The operating parameters considered in this study include turbine and pump efficiency, and pressure drop in a condenser and evaporator, respectively. As the turbine efficiency of R717 OTEC power system increases, the exergy efficiency of this system increases. But pressure drop in the evaporator of R717 OTEC power system increases, the exergy efficiency of this system decreases, respectively. And, in case of exergy efficiency of this OTEC system, the turbine efficiency and pressure drop in a condenser on R717 OTEC power system is the largest and the lowest among operation parameters, respectively.

A Study on Improvement of the Light Emitting Efficiency on Flip Chip LED with Patterned Sapphire Substrate by the Optical Simulation (광학 시뮬레이션을 이용한 Patterned Sapphire Substrate에 따른 Flip Chip LED의 광 추출 효율 변화에 대한 연구)

  • Park, Hyun Jung;Lee, Dong Kyu;Kwak, Joon Seop
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.28 no.10
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    • pp.676-681
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    • 2015
  • Recently many studies being carried out to increase the light efficiency of LED. The external quantum efficiency of LED, generally the light efficiency, is determined by the internal quantum efficiency and the light extraction efficiency. The internal quantum efficiency of LED was already reached to more than 90%, but the light extraction efficiency is still insufficient compared with the internal quantum efficiency because the total internal reflection is generated in the interface between the LED chip and air. Thus, we studied about flip chip LED with PSS and performed the optical simulation which find more optimized PSS for flip chip LED to increase the light extraction efficiency. Decreasing of the total internal reflection and effect of diffused reflection according to PSS improved the light extraction efficiency. To get more higher the efficiency, we simulated flip chip with PSS that the parameters are arrangement, edge spacing, radius, height and shape of PSS.

Thermodynamic Analysis of the Diabatic Efficiency of Turbines and Compressors (터빈과 압축기의 비단열 효율에 대한 열역학적 해석)

  • Park, Kyoung Kuhn
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.40 no.3
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    • pp.139-148
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    • 2016
  • Thermodynamic analysis is conducted on the first-order approximation model for turbines and compressors. It is shown that the adiabatic efficiency could be greater than unity, depending on the entropic mean temperature, entropy generation, thermal reservoir temperature, and heat transfer. Therefore, adiabatic efficiency applied to a diabatic control volume results in an error overestimating its performance. To resolve this overestimation, it is suggested that a reversible diabatic process be referred to as an ideal process to evaluate diabatic efficiency. The diabatic efficiency suggested in this work is proven to always be less than unity and it is smaller than the exergy efficiency in most cases. The diabatic efficiency could be used as a more general definition of efficiency, which would include adiabatic efficiency.

A Study on the Marking Efficiency of Check-Patterned Shirts (체크무늬 Shirts의 Marking 효율성에 관한 연구)

  • Hong, Eun-Hee;Suh, Mi-A
    • The Research Journal of the Costume Culture
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    • v.17 no.5
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    • pp.746-757
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    • 2009
  • This study is focused on the elucidation of efficient and correct marking methods by comparing and analyzing marker efficiency depending on the marking job condition such as interval of checking-pattern, width of materials, and marker orientation using man's shirts. To compare the marking efficiency of shirts, plain and check-patterned materials with the intervals of $1.5{\times}1.5cm$, $3{\times}3cm$, and $5{\times}5cm$ were selected. First, in the comparison of marking efficiency depending on materials width, the highest efficiency was obtained with nap-either-way position of 150cm, plain materials and lowest efficiency with nap-one-way position of 150cm, $5{\times}5cm$ check-pattern materials. Regardless of the direction of marker position, the marking efficiency of 150cm width was higher than 110cm width in the plain, $1.5{\times}1.5cm$ and $3{\times}3cm$ check-pattern interval, but the marking efficiency of 110cm width was higher than 150cm width in the $1.5{\times}1.5cm$ check-pattern interval. Second, in the comparison of marking efficiency depending on the direction of marker position, regardless of check-pattern interval and material width, the highest efficiency was obtained with nap-either-way position. And nap-up-and-down and nap-one-way follows next. Third, in the comparison of marking efficiency depending on check-pattern interval, the efficiency of plain materials was higher than those of check-patterned materials. And increasing the intervals decreased marking efficiency and vice versa. So the lowest efficiency was obtained with $5{\times}5cm$ check patterned materials.

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