• Title, Summary, Keyword: Dynamic Efficiency

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Dynamic Analysis of National R&D Projects' Qualitative Efficiency (국가연구개발사업 질적 효율성의 동태적 분석)

  • Kim, Kyungsoo;Cho, Namwook
    • Journal of the Korea Society of Digital Industry and Information Management
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    • v.15 no.1
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    • pp.9-20
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    • 2019
  • Korea's R&D investment has significantly increased in recent years. However, the efficiency of R&D investment is still in question. In order to examine the ways to improve the efficiency of R&D investment, this paper presents dynamic analysis on both quantitative and qualitative efficiency of R&D projects. A Data Envelopment Analysis(DEA)/Window method is used to analyze static and dynamic efficiencies of Industrial Material R&D projects in Korea from 2012 to 2016. As a result, statistically significant differences between quantitative and qualitative efficiency have been found. It has been observed that characteristics of Decision Making Units(DMUs) have an impact on both static and dynamic efficiencies. In particular, textile and ceramic projects showed relatively stable qualitative efficiency for a short-term perspective, while steel and chemical projects showed such stability for a long-term perspective. Among the types of project principals, universities showed relatively stable efficiency, compared with private sectors and research institutes. The results of this paper can be used as a guideline to manage the performance and stability of R&D projects' efficiency.

High-Efficiency DC-DC Converter with Improved Dynamic Response Characteristics for Modular Photovoltaic Power Conversion (모듈형 태양광 발전을 위한 개선된 동적응답 특성을 지닌 고효율 DC-DC 컨버터)

  • Choi, Jae-Yeon;Choi, Woo-Young
    • The Transactions of the Korean Institute of Power Electronics
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    • v.18 no.1
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    • pp.54-62
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    • 2013
  • This paper proposes a high-efficiency DC-DC converter with improved dynamic response characteristics for modular photovoltaic power conversion. High power efficiency is achieved by reducing switching power losses of the DC-DC converter. The voltage stress of power switches is reduced at primary side. Zero-current switching of output diodes is achieved at secondary side. A modified proportional and integral controller is suggested to improve the dynamic responses of the DC-DC converter. The performance of the proposed converter is verified based on a 200 [W] modular power conversion system including the grid-tied DC-AC inverter. The proposed DC-DC converter achieves the efficiency of 97.9 % at 60 [V] input voltage for a 200 [W] output power. The overall system including DC-DC converter and DC-AC inverter achieves the efficiency of 93.0 % when 200 [W] power is supplied into the grid.

The mechanism of thrust generation by dynamic stall in flapping flight

  • Lee Jung Sang;Kim Chongam;Rho Oh-Hyun
    • 한국전산유체공학회:학술대회논문집
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    • pp.291-293
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    • 2003
  • This paper deals with a thrust generation of flapping-airfoil by dynamic stall. From many other previous research results, phase angle $ between pitching and plunging mode of flapping motion must be 90 deg. to satisfy maximum propulsive efficiency. In this case, leading edge vortex is relatively small. This phenomenon is related dynamic stall. So preventing leading edge vortex induced by dynamic stall guarantees maximum propulsive efficiency. But, in this paper we insist the leading edge vortex yields quite a positive influence on thrust generation and propulsive efficiency. In order to certify our opinion, pitching and plunging motions were calculated with the parameter of amplitude and frequency by using the unsteady, incompressible Navier-Stokes flow solver with a two-equation turbulence model. For more efficient computation, it is parallelized by MPI programming method.

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Dynamic Analysis of PEM fuel cell system (PEM 연료전지시스템의 동특성 해석)

  • Kim Beomsoo;Jeon Soonil;Lim Wonsik;Park Yeong-il
    • 한국신재생에너지학회:학술대회논문집
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    • pp.353-356
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    • 2005
  • We developed a dynamic model of PEM fuel cell system which can analyze its transient response to dynamic load current. System components such as compressor, air cooler, humidifier, and stack were modeled based on their dynamic equations and performance maps by using Matlab Simulink platform. Through this simulation model, dynamic characteristics of fuel cell system including oxygen excess rat io, stack voltage, and system efficiency were shown. In addition to that, we briefly analyzed the humidity effect on cathode pressure and system efficiency, expecting that this model can be further used to optimize fuel cell system parameters just like operating pressure and temperature, humidity and oxygen excess ratio.

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A Study on High Efficiency Vector Controlled Induction Motor Drive System (고효율 벡터제어 유도전동식 구동 시트템에 관한 연구)

  • Kim, Heung-Geun
    • The Transactions of the Korean Institute of Electrical Engineers
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    • v.39 no.11
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    • pp.1174-1182
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    • 1990
  • A hgih efficiency and good dynamic performance drive system of an induction motor is presented in this paper using vector control technique. If the induction motor is driven under light loads with rated flux, the iron loss is excessively large compared with the copper loss, resulting in poor motor efficiency. High efficiency drive of an induction motor can be achieved by adjusting the flux level which leads the total motor loss to be a minimum value. Generally reducing the flux degrades the dynamic performance, but the dynamic performance of the proposed system is also maintained high. If the d-axis is coincident with rotor flux phasor in synchronous rotating reference frame, the stator current can be decoupled as flux component and torque component. At steady state, the developed motor torque is proportional to the product of the flux and torque component. The combination of the two components minimizing the motor loss could be found with numerical method. As the procedure to obtain the optimal combination is too hard, it is found experimentally. The system block diagram is suggested for maximum efficiency control. The proposed system is studied through digital simulation and verified with experiment. The experimental results show the possiblity of a high efficiency drive with good dynamic performance of maximum efficiency control.

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3-Point MPPT Algorithm under Dynamic Irradiation for Photovoltaic PCS (일사량 급변 시 유용한 3-Point 태양광 인버터 MPPT 알고리즘)

  • Kim, Dong-Gyun;Park, Kwan-nam;Cho, Sang-Yoon;Lee, Young-Kwoun;Yu, Gwon-Jong;Song, Seung-Ho;Choy, Ick;Choi, Ju-Yeop
    • Proceedings of the KIPE Conference
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    • pp.469-470
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    • 2016
  • Since efficiency of maximum power point tracking (MPPT) is important for photovoltaic systems, a number of MPPT algorithms have already been researched for other environment, however, the most of MPPT algorithms can't track maximum point in dynamic irradiation. In this paper, P&O and 3-Point MPPT which is more specialized in dynamic irradiation are compared in basis of European Efficiency Test(EN50530). The efficiency of 3-Point MPPT algorithm is proved by simulation and experiment. In result, 3-Point MPPT shows higher efficiency in dynamic irradiation and less affected by environment than P&O.

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Analyzing the Dynamic Productive Efficiency of Large Purse Seine Fishery in Korea (대형선망어업의 동태적 생산효율성 분석)

  • Seo, Ju-Nam;Kim, Do-Hoon
    • The Journal of Fisheries Business Administration
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    • v.43 no.1
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    • pp.11-18
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    • 2012
  • This study is aimed to estimate a dynamic productive efficiency by vessel of large purse seine fishery and analyze changes of them over times using a window/DEA method. In addition, based on estimation results, it aims to suggest production management implications for an viable development of fisheries. Results indicated that an annual efficiency change of large purse seine fishery was estimated at 0.77 for 2007~2008, 0.83 for 2008~2009, and 0.77 for 2009~2010, showing a decreasing trend. As returns on sales of vessels of large purse seine fishery showed a decreasing trend, the degree of efficiency of a vessel might be closely related to the fishing profitability. The Window/DEA method was used in this study to estimate the efficiencies of vessels for large purse seine fishery. This method is well known and widely used to analyze the dynamic efficiency and it can provide useful implications for management of input factors. As a limitation of this study, it was not able to provide detailed management ways to reduce inefficiencies. However, they can be investigated with data on managerial factor, human factor, distribution factors as a future study.

A study on Dynamic Gait Quadruped Walking Robot (사각 보행 로봇의 동적 걸음새에 관한 연구)

  • 김진섭;오준호;조진철
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • pp.78-81
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    • 1997
  • In this study, we prepose the dynamic gait in consideration of emerge efficiency. The proposed dynamic gait is applied to the quadruped walking robot and experiments are performed for real robot. We proposed the dynamic gait is diagonal gait which is modified the trot gait in consideration of energy efficiency. The proposed gait is composed of two steps. In one step, the robot walks in the trot gait. In the other step, the robot walks with making the center of gravity lie on the two legs supporting line. Realization of the diagonal intermittent trot gait is performed by open loop contal and motion planning of the proposed gait. The validity of the purposed gait is confirmed by our experiment.

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A Dynamic Utilization method of FSM for Adaptive NPC Generation (적응형 NPC 생성을 위한 FSM의 동적 활용 방안)

  • Yang, Jeong-Mo;Cho, Kyung-Eun;Um, Ky-Hyun
    • Journal of Korea Multimedia Society
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    • v.11 no.9
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    • pp.1258-1266
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    • 2008
  • Most game players obtain more satisfactions by interacting with human players that have fluxed behavior patterns, than with NPC(Non-Player Character)s that have fixed behavior patterns. Since it is impossible that game players always interact with human players, adaptive NPCs that can variously behave are required. In this paper, we present a method to create adaptive NPCs using a dynamic FSM(Finite State Machine). This method configures a dynamic FSM by using behavior information at behavior database, and repeatedly updates the dynamic FSM so that the dynamic FSM's total efficiency approaches to a given target efficiency. NPC adapts to game players through this process. For an experiment, we have implemented a 2D game with this strategy, and experimented with various target efficiencies. We show that a dynamic FSM's total efficiency approaches to target efficiency by updating a dynamic FSM several times over. It means that the adaptive NPC to be generated, adapts to game players.

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Ratio of Hammer Energy and Dynamic Efficiency of Standard Penetration Test (표준관입 시험 해머의 에너지비와 동적효율)

  • Lee, Chang-Ho;Lee, Woo-Jin
    • Journal of the Korean Geotechnical Society
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    • v.21 no.9
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    • pp.5-12
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    • 2005
  • SPT hammer energy and its delivery are hon to influence the N value. The SPT hammer energy is classified into theoretical energy, velocity energy, rod energy and dynamic efficiency. In this study, the rod energy and the velocity energy are measured directly by PDA and Digital Line-Scan Camera which are most widely used type of SPT apparatus in Korea. The Dynamic efficiency is calculated through measured data. As the results of this study, the averages of rod energy ratio of donut, safety and automatic hammer are measured at 49.57, 61.60, and at $87.04\%$ by FV method. The averages of hammer velocity of donut, safety and automatic hammer are measured at $3.177{\pm}0.872$, $3.385{\pm}0.681$, and at $3.651{\pm}0.550$ m/s by Digital Line-Scan Camera, with the dynamic efficiencies at 0.732, 0.801, and 0.973 respectively.