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  • Title/Summary/Keyword: Optimal Operation

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Evaluating Carriers for Immobilizing Saccharomyces cerevisiae for Ethanol Production in a Continuous Column Reactor

  • Cha, Hye-Geun;Kim, Yi-Ok;Choi, Woon Yong;Kang, Do-Hyung;Lee, Hyeon-Yong;Jung, Kyung-Hwan
    • Mycobiology
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    • v.42 no.3
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    • pp.249-255
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    • 2014
  • We evaluated a more practical and cost-effective immobilization carriers for ethanol production using the yeast Saccharomyces cerevisiae. Three candidate materials-rice hull, rice straw, and sawdust-were tested for their cell-adsorption capacity and operational durability. Derivatizations of rice hull, rice straw, and sawdust with the optimal concentration of 0.5 M of 2-(diethylamino)ethyl chloride hydrochloride (DEAE HCl) resulted in > 95% adsorption of the initial yeast cells at 2 hr for DEAE-rice hull and DEAE-sawdust and in only approximately 80% adsorption for DEAE-rice straw. In addition, DEAE-sawdust was found to be a more practical carrier for immobilizing yeast cells in terms of operational durability in shaking flask cultures with two different speeds of 60 and 150 rpm. Furthermore, the biosorption isotherms of DEAE-rice hull, -rice straw, and -sawdust for yeast cells revealed that the Qmax of DEAE-sawdust (82.6 mg/g) was greater than that of DEAE-rice hull and DEAE-rice straw. During the 404-hr of continuous column reactor operation using yeast cells immobilized on DEAE-sawdust, no serious detachment of the yeast cells from the DEAE-sawdust was recorded. Ethanol yield of approximately 3.04 g/L was produced steadily, and glucose was completely converted to ethanol at a yield of 0.375 g-ethanol/g-glucose (73.4% of the theoretical value). Thus, sawdust is a promising practical immobilization carrier for ethanol production, with significance in the production of bioethanol as a biofuel.

A New Key Management Mechanism and Performance Improvement for Conditional Access System (제한수신시스템을 위한 키 관리 메카니즘과 성능향상 방안)

  • 조현숙;이상호
    • The KIPS Transactions:PartC
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    • v.8C no.1
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    • pp.75-87
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    • 2001
  • The Conditional Access System is the complete system for ensuring that broadcasting services are only accessible to those who are entitled to receive them. Four major parts to this system are scrambling, descrambling, authentication and encryption. For the proper operation, which means hard-to- break and uninterrupted service, secure key management and efficient delivery mechanism are very important design factors to this system. Performance analysis is another important factor to this system that is used in massive subscriber environment. In this thesis, one of the secure and efficient key management mechanisms is proposed. For the secrecy of this mechanism, hierarchical stacking of keys and key generation matrix are proposed. For the proof of efficient delivery of those keys, simulation results and performance analysis. which is based on queuing analysis, are presented. Lastly, optimal key generation and delivery period, maximal and minimal key deliver time, and communication capacity for data collection are presented for various subscriber volume.

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A Non-fixed Log Area Management Technique in Block for Flash Memory DBMS (플래시메모리 DBMS를 위한 블록의 비고정적 로그 영역 관리 기법)

  • Cho, Bye-Won;Han, Yong-Koo;Lee, Young-Koo
    • Journal of KIISE:Databases
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    • v.37 no.5
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    • pp.238-249
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    • 2010
  • Flash memory has been studied as a storage medium in order to improve the performance of the system using its high computing speed in the DBMS field where frequent data access is needed. The most difficulty using the flash memory is the performance degradation and the life span shortening of flash memory coming from inefficient in-place update. Log based approaches have been studied to solve inefficient in-place update problem in the DBMS where write operations occur in smaller size of data than page frequently. However the existing log based approaches suffer from the frequent merging operations, which are the principal cause of performance deterioration. Thus is because their fixed log area management can not guarantee a sufficient space for logs. In this paper, we propose non-fixed log area management technique that can minimize the occurrence of the merging operations by promising an enough space for logs. We also suggest the cost calculation model of the optimal log sector number minimizing the system operation cost in a block. In experiment, we show that our non-fixed log area management technique can have the improved performance compared to existing approaches.

A study on the Conceptual Design for the Real-time wind Power Prediction System in Jeju (제주 실시간 풍력발전 출력 예측시스템 개발을 위한 개념설계 연구)

  • Lee, Young-Mi;Yoo, Myoung-Suk;Choi, Hong-Seok;Kim, Yong-Jun;Seo, Young-Jun
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.59 no.12
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    • pp.2202-2211
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    • 2010
  • The wind power prediction system is composed of a meteorological forecasting module, calculation module of wind power output and HMI(Human Machine Interface) visualization system. The final information from this system is a short-term (6hr ahead) and mid-term (48hr ahead) wind power prediction value. The meteorological forecasting module for wind speed and direction forecasting is a combination of physical and statistical model. In this system, the WRF(Weather Research and Forecasting) model, which is a three-dimensional numerical weather model, is used as the physical model and the GFS(Global Forecasting System) models is used for initial condition forecasting. The 100m resolution terrain data is used to improve the accuracy of this system. In addition, optimization of the physical model carried out using historic weather data in Jeju. The mid-term prediction value from the physical model is used in the statistical method for a short-term prediction. The final power prediction is calculated using an optimal adjustment between the currently observed data and data predicted from the power curve model. The final wind power prediction value is provided to customs using a HMI visualization system. The aim of this study is to further improve the accuracy of this prediction system and develop a practical system for power system operation and the energy market in the Smart-Grid.

A Comparative Analysis of Status on the Selection and Evaluation of Field Manager in Apartment and Office Building Project (공동주택과 오피스 건설현장의 조직원선정 및 평가실태 비교분석)

  • Lee Jung-Yong;Kim Byeong-Lae;Son Chang-Baek
    • Proceedings of the Korean Institute Of Construction Engineering and Management
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    • autumn
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    • pp.290-293
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    • 2003
  • The field organization management in construction industry is very important factor improvement and cost reduction. But, until now, evaluation methods on the existing field organization did not make ready and endeavor of organization betterment was insufficient in construction industry. The purpose of this study to provide basic data for reasonable selection and evaluation of the field manager through analyzing operation status of the existing field organization in apartment and office building project by interview and questionnaire on the 22 construction companies. This study presented optimal proposal on the selection and evalution of field manager for productivity improvement and cost reduction by means of efficient construction progress in apartment and dffice building project.

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A 3-Step Speed Control for Minimizing Energy Consumption for Battery-Powered Wheeled Mobile Robots (배터리로 구동되는 이동 로봇의 에너지 소모 최소화를 위한 3-구간 속도 제어)

  • Kim Byung-Kook;Kim Chong-Hui
    • Journal of Institute of Control, Robotics and Systems
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    • v.12 no.3
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    • pp.208-220
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    • 2006
  • Energy of wheeled mobile robot is usually supplied by batteries. In order to extend operation time of mobile robots, it is necessary to minimize the energy consumption. The energy is dissipated mostly in the motors, which strongly depends on the velocity profile. This paper investigates various 3-step (acceleration - cruise - deceleration) speed control methods to minimize a new energy object function which considers the practical energy consumption dissipated in motors related to motor control input, velocity profile, and motor dynamics. We performed an analysis on the energy consumption various velocity profile patterns generated by standard control input such as step input, ramp input, parabolic input, and exponential input. Based on these standard control inputs, we analyzed the six 3-step velocity profile patterns: E-C-E, P-C-P, R-C-R, S-C-S, R-C-S, and S-C-R (S means a step control input, R means a ramp control input, P means a parabolic control input, and E means an exponential control input, C means a constant cruise velocity), and suggested an efficient iterative search algorithm with binary search which can find the numerical solution quickly. We performed various computer simulations to show the performance of the energy-optimal 3-step speed control in comparison with a conventional 3-step speed control with a reasonable constant acceleration as a benchmark. Simulation results show that the E-C-E is the most energy efficient 3-step velocity profile pattern, which enables wheeled mobile robot to extend working time up to 50%.

Analysis of Customer Power Quality Characteristics Using PV Test Devices (태양광전원 계통연계시험장치에 의한 수용가 전력품질특성에 관한 연구)

  • Kim, Byungmok;Kim, Byungki;Park, Jeabum;Rho, Daeseok
    • Journal of the Korea Convergence Society
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    • v.2 no.4
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    • pp.21-27
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    • 2011
  • Recently, new distributed power sources such as photovoltaic, wind power, fuel cell systems etc. are energetically interconnected and operated in the distribution feeders, as one of the national projects for alternative energy. When new power sources are considered to be interconnected to distribution systems, bi-directional power flow and interconnection conditions of new power sources may cause several power quality problems like voltage sag, voltage swell, harmonics, since new power sources can change typical characteristics of distribution systems. Under these situations, this paper deals with the analysis the power quality problems at primary and secondary feeders in distribution systems, when new power sources like photovoltaic (PV) systems are interconnected, by using the test devices for PV systems based on the LabVIEW S/W. This paper presents the test device which is consisted with model distribution system and model PV systems. By performing the simulation for power quality operation characteristic based on the test facilities, this paper presents the optimal countermeasures for power quality.

A Study on Design of 50kW PMSG for Micro-grid Application (마이크로그리드용 50kW급 PMSG 설계에 관한 연구)

  • Jeong, Moon-Seon;Moon, Chae-Joo;Kim, Hyoung-Gil;Chang, Young-Hak;Park, Tae-Sik
    • The Journal of the Korea institute of electronic communication sciences
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    • v.9 no.4
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    • pp.527-536
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    • 2014
  • In this paper, the 50kW aerogenerator which is applicable to the microgrid was designed and analyzed by using commercial simulation program Maxwell 2D. Particularly, the suggested PMSG to reduce the cogging torque introduced the offset and skew concept. The suggested optimal value of offset and skew was decided by 2mm and 60 degree of electric angle. The simulation results of the PMSG when load operation condition showed the average harmonic distortion 1.3%, voltage 322.41V, current 94.95A, and iron loss 9.73W, eddy current loss 73.68W, copper loss 3.52kW. The capacity of aerogenerator calculated 61.56kW, and the suggested design process can be applied to higher capacity generator.

Development of RTDS-MATLAB Integrated Simulation Environment for Development and Verification of Voltage Measurement based CVR Control Algorithm (전압계측기반 CVR제어 알고리즘 개발 및 검증을 위한 RTDS-MATLAB 연동 시뮬레이션 환경 개발)

  • Go, Seok-Il;Ahn, Seon-Ju;Choi, Joon-Ho;Nam-Koong, Won;Shin, Chang-Hoon
    • KEPCO Journal on Electric Power and Energy
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    • v.2 no.4
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    • pp.549-556
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    • 2016
  • CVR is a technique for reducing power consumption by reducing the voltage of the system and many demonstrations and studies have been conducted in the past. Recently, SCADA-based or AMI-based VVC have been developed and the CVR is used as an important operation mode. Using a variety of instruments, CVR determines the optimal VVC control references by closed loop control. In this paper, we implemented RTDS-MATLAB integrated simulation environment for development and verification of CVR control algorithm based on voltage measurement. The voltage control device of distribution system was modeled using RTDS and MATLAB has constructed a controller that can measure and control the voltage of the simulation system of RTDS. After the capacitor, which is a reactive power control device, flattens the voltage of the system, the control algorithm reduces the voltage of the system by tap control of the OLTC based on the flatten voltage. The proposed system was verified by simulations.

Estimation of Reasonable Price of Battery Energy Storage System for Electricity Customers Demand Management (전력소비자 수요관리용 전지전력저장시스템의 적정 가격 산정)

  • Kim, Seul-Ki;Cho, Kyeong-Hee;Kim, Jong-Yul;Kim, Eung-Sang
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.62 no.10
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    • pp.1390-1396
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    • 2013
  • The paper estimated the reasonable market price of lead-acid battery energy storage system (BESS) intended for demand management of electricity customers. As time-of-use (TOU) tariffs have extended to a larger number of customers and gaps in the peak and off-peak rates have gradually risen, deployment of BESS has been highly needed. However, immature engineering techniques, lack of field experiences and high initial investment cost have been barriers to opening up ESS markets. This paper assessed electricity cost that BESS operation could save for customers and, based on the possible cost savings, estimated reasonable prices at which BESSs could become a more prospective option for demand management of customers. Battery scheduling was optimized to maximize the electricity cost savings that BESS would possibly achieve under TOU tariffs conditions. Basic economic factors such as payback period and return on investment were calculated to determine reasonable market prices. Actual load data of 12 industrial customers were used for case studies.