• Title/Summary/Keyword: Optimal Operation

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A Geometric Compression Method Using Dominant Points for Transmission to LEO Satellites

  • Ko, Kwang Hee;Ahn, Hyo-Sung;Wang, Semyung;Choi, Sujin;Jung, Okchul;Chung, Daewon;Park, Hyungjun
    • International Journal of Aeronautical and Space Sciences
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    • v.17 no.4
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    • pp.622-630
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    • 2016
  • In the operation of a low earth orbit satellite, a series of antenna commands are transmitted from a ground station to the satellite within a visibility window (i.e., the time period for which an antenna of the satellite is visible from the station) and executed to control the antenna. The window is a limited resource where all data transmission is carried out. Therefore, minimizing the transmission time for the antenna commands by reducing the data size is necessary in order to provide more time for the transmission of other data. In this paper, we propose a geometric compression method based on B-spline curve fitting using dominant points in order to compactly represent the antenna commands. We transform the problem of command size reduction into a geometric problem that is relatively easier to deal with. The command data are interpreted as points in a 2D space. The geometric properties of the data distribution are considered to determine the optimal parameters for a curve approximating the data with sufficient accuracy. Experimental results demonstrate that the proposed method is superior to conventional methods currently used in practice.

The Analysis of Quench Protection System through Thermo-Electrodynamics of Resistive Transition in SC Magnet (초전도자석내의 국부적 상변이에 대한 열적.전기역학적 해석 및 퀜치보호시스템의 설계 및 특성해석)

  • Chu, Y.;Bae, J.H.;Kim, H.M.;Jang, M.H.;Joo, M.S.;Ko, T.K.;Kim, K.M.;Jeong, S.K.
    • Proceedings of the KIEE Conference
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    • 1997.07a
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    • pp.86-88
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    • 1997
  • The detection of the normal zones in the coil winding and the initiation of the proper dump sequence have been one of the most important areas in the superconducting magnet technology. In this paper, the process to derive optimal dump sequence has been investigated through quench simulation and analysis of magnetically coupled superconducting magnet system. The magnet terminal voltage and maximum temperature rise in the quench initiated point are calculated with respect to various input variables such as operation current, dump resistance, etc. The experimental system is comprised of sc solenoidal coil, data aquisition device, external circuit breakers and dump resistor. The quench behavior of the magnet(e.g., temperature profile and the voltage signal) was measured. From this results, theoretical predictions were found to coincide with the experimental observations.

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UHF Sensor Location Optimization for Partial Discharge Signals Detection Method (UHF 센서 위치 최적화로 부분방전 신호 검출 방법)

  • Choi, Mun-Gyu;Cha, Hanju
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.63 no.3
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    • pp.409-413
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    • 2014
  • GIS partial discharge that occurred in the UHF band signal is effectively detected by the method to IEC60270 5pc the apparent minimum discharge can be detected over the GIS arrangement of the sensor interior and exterior of the UHF in accordance with the optimized position signal by considering the damping ratio is selected so that the signals can be obtained to be mounted. 362kV, 800kV GIS is installed on the internal and external sensors are UHF band signal attenuation is set by measuring the reference value, but the operation, 170kV case 362kV, 800kV on the basis of the measurement data and to be installed and operated. When 170kV per 1Bay by installing the built-in sensor 1 for detecting a partial discharge signal, But, GIS signal attenuation is large in the case of an internal partial discharge signal is not detected in some cases. Where the attenuation is great UHF signal of the sensor by increasing the quantity of partial discharge signals were acquired to allow relocation. The greater the spacing between the sensor and the sensor is applied simplifies the installation and reduces the cost in terms of maintenance of appropriate optimal position is calculated to detect the partial discharge signal is needed. Thus 170kV GIS signal power attenuation of a partial discharge by measuring the UHF sensor, and by relocating the proper position is calculated in accordance with the sensor signal decay rate and minimize the error of omission in detecting a partial discharge signal was optimized.

Eddy Current Bobbin Probe Design for Steam Generator Tubes in NPPs (원전 증기발생기 전열관 와전류검사 보빈탐촉자 설계)

  • Nam, Min-Woo;Lee, Hee-Jong;Jee, Dong-Hyun;Jung, Jee-Hong;Kim, Cheol-Gi
    • Journal of the Korean Society for Nondestructive Testing
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    • v.27 no.2
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    • pp.89-96
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    • 2007
  • The bobbin probe examination is basic and the important method among other ECT techniques for the steam generator tube integrity assesment that is practiced during each plant outage. The bobbin probe is one of the essential components which consist of the whole ECT examination system, and provides us a decisive data for the evaluation of tube integrity in compliance with acceptance criteria described in specific procedures. The selection of examination probe is especially important because the quality of acquired ECT data is determined by the probe design characteristics, such as geometry and operation frequency, and has enormous effects on examination results. In this study, An optimal differential bobbin probe is designed for the steam generator tube inspection in nuclear power plants(NPPs). Based on the test results for electrical and ECT signal characteristics, the prototype bobbin probe satisfies all the criteria.

Fault Detection of Rolling Element Bearing for Low Speed Machine Using Wiener Filter and Shock Pulse Counting (위너 필터와 충격 펄스 카운팅을 이용한 저속 기계용 구름 베어링의 결함 검출)

  • Park, Sung-Taek;Weon, Jong-Il;Park, Sung Bum;Woo, Heung-Sik
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.22 no.12
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    • pp.1227-1236
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    • 2012
  • The low speed machinery faults are usually caused by the bearing failure of the rolling elements. As the life time of the bearing is limited, the condition monitoring of bearing is very important to maintain the continuous operation without failures. A few monitoring techniques using time domain, frequency domain and fuzzy neural network vibration analysis are introduced to detect and diagnose the faults of the low speed machinery. This paper presents a method of fault detection for the rolling element bearing in the low speed machinery using the Wiener filtering and shock pulse counting techniques. Wiener filter is used for noise cancellation and it clearly makes the shock pulse emerge from the time signal with the high level of noise. The shock pulse counting is used to determine the various faults obviously from the shock signal with transient pulses not related with the bearing fault. Machine fault simulator is used for the experimental measurement in order to verify this technique is the powerful tool for the low speed machine compared with the frequency analysis. The test results show that the method proposed is very effective parameter even for the signal with high contaminated noise, speed variation and very low energy. The presented method shows the optimal tool for the condition monitoring purpose to detect the various bearing fault with high accuracy.

Two-Stage Latissimus Dorsi Flap with Implant for Unilateral Breast Reconstruction: Getting the Size Right

  • Feng, Jiajun;Pardoe, Cleone I;Mota, Ashley Manuel;Chui, Christopher Hoe Kong;Tan, Bien-Keem
    • Archives of Plastic Surgery
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    • v.43 no.2
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    • pp.197-203
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    • 2016
  • Background The aim of unilateral breast reconstruction after mastectomy is to craft a natural-looking breast with symmetry. The latissimus dorsi (LD) flap with implant is an established technique for this purpose. However, it is challenging to obtain adequate volume and satisfactory aesthetic results using a one-stage operation when considering factors such as muscle atrophy, wound dehiscence and excessive scarring. The two-stage reconstruction addresses these difficulties by using a tissue expander to gradually enlarge the skin pocket which eventually holds an appropriately sized implant. Methods We analyzed nine patients who underwent unilateral two-stage LD reconstruction. In the first stage, an expander was placed along with the LD flap to reconstruct the mastectomy defect, followed by gradual tissue expansion to achieve overexpansion of the skin pocket. The final implant volume was determined by measuring the residual expander volume after aspirating the excess saline. Finally, the expander was replaced with the chosen implant. Results The average volume of tissue expansion was 460 mL. The resultant expansion allowed an implant ranging in volume from 255 to 420 mL to be placed alongside the LD muscle. Seven patients scored less than six on the relative breast retraction assessment formula for breast symmetry, indicating excellent breast symmetry. The remaining two patients scored between six and eight, indicating good symmetry. Conclusions This approach allows the size of the eventual implant to be estimated after the skin pocket has healed completely and the LD muscle has undergone natural atrophy. Optimal reconstruction results were achieved using this approach.

Comparison of Coronary Artery Bypass Graft-First and Percutaneous Coronary Intervention-First Approaches for 2-Stage Hybrid Coronary Revascularization

  • Choi, Hang Jun;Kang, Joonkyu;Song, Hyun;Kim, Do Yeon;Choi, Kuk Bin
    • Journal of Chest Surgery
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    • v.50 no.4
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    • pp.247-254
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    • 2017
  • Background: Hybrid coronary revascularization (HCR) was developed to combine the advantages of coronary artery bypass graft (CABG) with percutaneous coronary intervention (PCI). However, it is still controversial whether it is more optimal to perform CABG or PCI first. The purpose of this study was to compare the clinical outcomes of these 2 approaches. Methods: Eighty patients who underwent HCR from May 2010 to December 2015 were enrolled in this retrospective analysis. The CABG-first group comprised 12 patients and the PCI-first group comprised 68 patients. Outcomes of interest included in-hospital perioperative factors, major adverse cardiac and cerebrovascular events (MACCEs), and the incidence of repeated revascularization, especially for the target vessel lesion. Results: No significant difference was found in the amount of postoperative bleeding (p=0.239). The incidence of MACCEs was similar between the CABG-first and PCI-first groups (1 of 12 [8.3%] vs. 5 of 68 [7.4%], p>0.999). Repeated revascularization was performed on 3 patients (25%) in the CABG-first and 9 patients (13.2%) in the PCI-first group (p=0.376). Conclusion: There were no significant differences in postoperative and medium-term outcomes between the CABG-first and PCI-first groups. Based on these results, it can be inferred that it is safe to opt for either CABG or PCI as the primary procedure in 2-stage HCR.

A Design of the Cooling Channel in the Bipolar Plate of PEMFC Using Experimental Design Method (실험설계법을 이용한 연료전지 분리판 냉각채널 설계)

  • Zhang, Xia;Kwon, Oh-Jung;Oh, Byeong Soo
    • Transactions of the Korean Society of Automotive Engineers
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    • v.23 no.5
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    • pp.545-552
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    • 2015
  • The heat generation in PEMFC is proportional to the electrical power output. Therefore, when the fuel cell produced the maximum output, the maximum heat was generated. In order to maintain the performance of the fuel cell, thermal management is as important as pressure and humidity conditions of the reactive gas. In this study, considering the thermal management for the maximum output operation, the optimal cooling channel design specifications of bipolar plate are found for the highest cooling performance. In the current bipolar plate research, many studies focused on analyzing various factors individually but there is no more study on the interaction between design factors. In this study, the heat transfer was simulated by COMSOL Multiphysics with the main design factors which are designated shape, width and rib length. One of the experimental design methods, general full factorial design method, was used to analyze the main factor and interaction on average temperature and maximum temperature for the design specification of fuel cell bipolar plate. When analysis result shows that all of these three factors are highly important, it can confirm that the interaction occurs between the factors.

Characteristics of Combustion and Thermal Efficiency for Premixed Flat Plate Burner Using a Porous Media (다공성 소재 종류에 따른 예혼합 평판버너의 연소 및 열효율 특성에 관한 연구)

  • Kum, Sungmin;Yu, Byeonghun;Lee, Chang-Eon;Lee, Seungro
    • Journal of Energy Engineering
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    • v.21 no.4
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    • pp.385-392
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    • 2012
  • The purpose of this study is investigated on the combustion and the thermal characteristics of porous media burners which are many using for a condensing boiler recently. In addition, results of this study will be used the fundamental information to decide the burner type which will be applied to the future development of EGR(Exhaust gas recirculation) condensing boiler. Two flat type of burners made of a the metal fiber(MF) and the ceramic(CM) were selected and examined, experimentally. As experimental results, the emitted CO concentration of CM was higher than that of MF. However, the NO concentration of MF was higher than that of CM. The efficiencies of both burners were increased as increasing the burner capacity. While the efficiency of MF was higher than that of CM, regardless of the burner capacity. In the experimental range, MF is appropriated for the burner material and 0.8 of equivalence ratio is an optimal operation condition, regarding of the proportional control, the thermal efficiency and emitted NO and CO concentration based on the regulations of KS B standard and EN 677 standard.

A Study on the Repair Parts Inventory Cost Estimation and V-METRIC Application for PBL Contract (PBL 계약을 위한 수리부속 재고비용 예측과 V-METRIC의 활용에 관한 연구)

  • Kim, Yoon Hwa;Lee, Sung Yong
    • Journal of the Korean Society of Systems Engineering
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    • v.13 no.1
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    • pp.79-88
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    • 2017
  • For the PBL contract, it is necessary for the contracting parties to share information regarding the reasonable inventory-level and the cost of its repair parts for the estimated demand. There are various models which can be used for this purpose. Among them, V-METRIC model is considered to be the most efficient and is most frequently applied. However, this model is usually used for optimizing the inventory level of the repair parts of the system under operation. The model uses a time series forecast model to determine the demand rate, which is a mandatory input factor for the model, based on past field data. However, since the system at the deployment stage has no operational performance record, it is necessary to find another alternative to be used as the demand rate of the model application. This research applies the V-METRIC model to find the optimal inventory level and cost estimation for repairable items to meet the target operational availability, which is a key performance indicator, at the time of the PBL contract for the deployment system. This study uses the calculated value based on the allocated MTBF to the system as the demand rate, which is used as input data for the model. Also, we would like to examine changes in inventory level and cost according to the changes in target operational availability and MTBF allocation.