• Title/Summary/Keyword: Effective load center

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An Experimental Study on Thermal Storage Performance of an Air Conditioning System with Slab Thermal Storage (슬래브축열 공조시스템의 축열성능에 관한 실험적 연구)

  • Jung Jae-Hoon;Shin Young-Gy
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.17 no.5
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    • pp.427-435
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    • 2005
  • This paper investigates the thermal storage performance of the office building which has adopted an air conditioning system with its slab structure as a regenerator. Four cases of the thermal storage performance experiment were conducted. Room air temperatures, floor slab temperatures, temperatures around the air conditioning unit were logged and analyzed. The load handling capacity of the air conditioning unit and the amount of heat stored in the slab were decided from those experiments. Several efficiencies were investigated to evaluate the performance of the thermal storage. The results concluded that the slab as a regenerator is very effective in cutting down peak loads of the office building.

Scheduling and Feedback Reduction in Coordinated Networks

  • Bang, Hans Jorgen;Orten, Pal
    • Journal of Communications and Networks
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    • v.13 no.4
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    • pp.339-344
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    • 2011
  • Base station coordination has received much attention as a means to reduce the inter-cell interference in cellular networks. However, this interference reducing ability comes at the expense of increased feedback, backhaul load and computational complexity. The degree of coordination is therefore limited in practice. In this paper, we explore the trade-off between capacity and feedback load in a cellular network with coordination clusters. Our main interest lies in a scenario with multiple fading users in each cell. The results indicate that a large fraction of the total gain can be achieved by a significant reduction in feedback. We also find an approximate expression for the distribution of the instantaneous signal to interference-plus-noise ratio (SINR) and propose a new effective scheduling algorithm.

Suppression of Load Pendulation Using Tagline Control System for Floating Crane (해상 크레인에 의해 인양되는 중량물의 거동 감쇠를 위한 Tagline 제어 시스템)

  • Ku, Nam-Kug;Cha, Ju-Hwan;Kwon, Jung-Han;Lee, Kyu-Yuel
    • Journal of the Society of Naval Architects of Korea
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    • v.46 no.5
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    • pp.527-535
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    • 2009
  • This paper describes the control system to suppress the load pendulation using tagline for the floating crane. Dynamic equation of motion of the floating crane and the load is derived using Newton's 2nd law and free body model. The floating crane and the load are assumed that they move in center plane. Each rigid body has 3 DOF (surge, heave, pitch), because it moves in two directions and rotates. Then, this system, which is composed of two rigid bodies, has 6 DOF. The gravitational force, the hydrostatic force, the hydrodynamic force and the tension of the wire rope are considered as external forces, which affect to the floating crane. To suppress the pendulation of the load, the tagline, which connects between the load and the float crane, is applied to the system. The tagline is composed of the spring and the wire rope. Proportional and Derivative control is used as a linear control algorithm. The results of the numerical analysis of the 3,600 ton floating crane show that the tagline system is effective to suppress the load pendulation.

Low-Load/Low-Eccentricity Performance Improvement Designs for Hydro Power Application of Cylindrical Turbine Guide Bearings - Introduction of Pad Leading-Edge Tapers (수력 원통형 터빈 가이드 베어링의 저부하/저편심 성능향상 설계 - 패드 선단 테이퍼의 도입)

  • Lee, An Sung;Jang, Sun-Yong
    • Tribology and Lubricants
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    • v.33 no.2
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    • pp.65-70
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    • 2017
  • In vertical hydro/hydraulic power turbine-generator applications, traditionally, cylindrical turbine guide bearings (TGBs) are widely used to provide turbine runner shafts with smooth rotation guides and supports. All existing cylindrical TGBs with simple plain pads have drawbacks such as having no pressure generation and film stiffness at the no-load condition and in addition, at the low-load/low-eccentricity condition, having very low film stiffness values and lacking design credibility in the stiffness values themselves. In this paper, in order to fundamentally improve the low-load/low-eccentricity performance of conventional cylindrical TGBs and thus enhance their design-application availability and usefulness, we propose to introduce a rotation-directional leading-edge taper to each partitioned pad, i.e., a pad leading-edge taper. We perform a design analysis of lubrication performance on $4-Pad{\times}4-Row$ cylindrical TGBs to verify an engineering/technical usefulness of the proposed pad leading-edge taper. Analysis results show that by introducing the leading-edge taper to each pad of the cylindrical TGB one can expect a constant high average direct stiffness with a high degree of design credibility, regardless of load value, even at the low-load/low-eccentricity condition and also control the average direct stiffness value by exploring the taper height as a design parameter. Therefore, we conclude that the proposed pad leading-edge tapers are greatly effective in more accurately predicting and controlling rotordynamic characteristics of vertical hydro-power turbine-generator rotor-bearing systems to which cylindrical TGBs are applied.

Strengthening RC frames subjected to lateral load with Ultra High-Performance fiber reinforced concrete using damage plasticity model

  • Kota, Sai Kubair;Rama, J.S. Kalyana;Murthy, A. Ramachandra
    • Earthquakes and Structures
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    • v.17 no.2
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    • pp.221-232
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    • 2019
  • Material non-linearity of Reinforced Concrete (RC) framed structures is studied by modelling concrete using the Concrete Damage Plasticity (CDP) theory. The stress-strain data of concrete in compression is modelled using the Hsu model. The structures are analyzed using a finite element approach by modelling them in ABAQUS / CAE. Single bay single storey RC frames, designed according to Indian Standard (IS):456:2000 and IS:13920:2016 are considered for assessing their maximum load carrying capacity and failure behavior under the influence of gravity loads and lateral loads. It is found that the CDP model is effective in predicting the failure behaviors of RC frame structures. Under the influence of the lateral load, the structure designed according to IS:13920 had a higher load carrying capacity when compared with the structure designed according to IS:456. Ultra High Performance Fiber Reinforced Concrete (UHPFRC) strip is used for strengthening the columns and beam column joints of the RC frame individually against lateral loads. 10mm and 20mm thick strips are adopted for the numerical simulation of RC column and beam-column joint. Results obtained from the study indicated that UHPFRC with two different thickness strips acts as a very good strengthening material in increasing the load carrying capacity of columns and beam-column joint by more than 5%. UHPFRC also improved the performance of the RC frames against lateral loads with an increase of more than 3.5% with the two different strips adopted. 20 mm thick strip is found to be an ideal size to enhance the load carrying capacity of the columns and beam-column joints. Among the strengthening locations adopted in the study, column strengthening is found to be more efficient when compared with the beam column joint strengthening.

Water Quality Management Planning for the Lake Sapgyo by Stream Grading Method (하천등급화 모델을 이용한 삽교호 수질관리 방안에 관한 연구)

  • Choi, Jeongho;Kim, Hongsu;Cho, Byunguk;Park, Sanghyun;Lee, Mukyu
    • Journal of Korean Society on Water Environment
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    • v.36 no.3
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    • pp.245-254
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    • 2020
  • Water quality improvement projects are being implemented without predicting the effect of water quality improvement on Lake Sapgyo. As the method of selecting the target stream for the effective conduct of water quality improvement projects the method of rating the streams were studied. To build a stream grading method, 60 major streams in the Lake Sapgyo system were monitored. The selection method of rivers subject to priority management for water quality improvement was applied to the stream grading method using the Analytic Hierarchy Process (AHP). The analysis of importance by site by stream grading method revealed the following: water quality (36.0%), flow (26.1%), travel load (13.4%), TMDL density (12.0%), TMDL (8.9%), and area (3.7%). The pollution level of the river was scored by using the stream grading method, and the ranking of 51 streams was calculated. Based on this, the group was classified into six grades (A-F). Among the groups, the F and E groups were selected as the priority management streams. Cheonan-Cheon (Cheonan City) was selected as the first stream to establish water quality improvement measures in the Lake Sapgyo system, and Seowoo-Cheon (Dangjin City) was selected as the second site, and Oncheon-Cheon (Asan City) was selected as the third site. Each local government is expected to improve the water quality improvement effect with limited resources when establishing and implementing water quality improvement measures for the streams (F group, E group) to be managed in this study.

CS-PDM Series Resonant High Frequency Inverter for Copy Machine

  • Sugimura, Hisayuki;Eid, Ahmad Mohamad;Hiraki, Eiji;Kim, Sung-Jung;Lee, Hyun-Woo;Nakaoka, Mutsuo
    • 제어로봇시스템학회:학술대회논문집
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    • 2005.06a
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    • pp.1066-1071
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    • 2005
  • This paper presents the two lossless auxiliary inductors-assisted voltage source type half bridge (single ended push pull: SEPP) series resonant high frequency inverter for induction heated fixing roller in copy and printing machines. The simple high-frequency inverter treated here can completely achieve stable zero current soft switching (ZCS) commutation for wide its output power regulation ranges and load variations under its constant high frequency pulse density modulation (PDM) scheme. Its transient and steady state operating principle is originally described and discussed for a constant high-frequency PDM control strategy under a stable ZCS operation commutation, together with its output effective power regulation characteristics-based on the high frequency PDM strategy. The experimental operating performances of this voltage source SEPP ZCS-PDM series resonant high frequency inverter using IGBTs are illustrated as compared with computer simulation results and experimental ones. Its power losses analysis and actual efficiency are evaluated and discussed on the basis of simulation and experimental results. The feasible effectiveness of this high frequency inverter appliance implemented here is proved from the practical point of view.

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Watershed Management Plan through Water Quality Monitoring for Main Branches of 4 Water Systems in Chungcheongnamdo (충청남도 4대수계 주요 지류하천 수질 모니터링을 통한 유역 관리 방안)

  • Park, Sanghyun;Kim, Hongsu;Cho, Byunguk;Moon, Eunho;Choi, Jinha
    • Journal of Korean Society on Water Environment
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    • v.32 no.2
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    • pp.163-172
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    • 2016
  • This study aimed to develop a plan for effective performance of a watershed through correct identification of a river watershed by using the flowrate of the river and water quality data, which is the basis for the establishment of the water environment policy. The target river for water quality improvement was selected based on the monitoring result for 4 water systems in Chungcheongnamdo province in the recent 3 years. The result of analysis for the distribution of discharge capacity by a pollution source group for the water quality improvement target river showed that most of the target river has a high discharge capacity in the water system for living and livestock. Analysis for the density of the total discharge capacity of the whole watershed of Chungcheongnamdo indicated that the river that needs water quality improvement has high BOD concentration and high discharge load density at the point that this river is located. Thus, for efficient watershed management through selection and concentration, Chungcheongnamdo needs to improve the target river in priority. Stepwise planning is also required to establish and execute the water quality improvement in order to satisfy said target water quality, and establish the index for the water improvement rate for its evaluation.

A Study on the Water Quality Improvement of Major Tributaries in Seoul, Applying Watershed Evaluation Techniques (총량관리 단위유역 평가기법을 활용한 서울특별시 주요 유입 지천의 수질개선효과에 관한 연구)

  • Shim, Kyuhyun;Kim, Gyeonghoon;Im, Taehyo;Kim, Youngseok;Kim, Seongmin
    • Journal of Korean Society on Water Environment
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    • v.37 no.1
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    • pp.32-46
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    • 2021
  • South Korea has been divided into quantities and water quality, and due to a revision of the Government Organization law in June 2018, the controversial water management system was integrated into the Ministry of Environment. The total Maximum Daily Loads System has been called the flower of water quality control, and since 2004, all three major river systems which have been introduced into the Han River system, despite its various difficult environments, and subsequently leading to all of the four major rivers undergoing obligatory implementation since 2013. Currently, the target TMDL (Han River Phase 1 and Other Water Systems Phase 3) for the 2020 stage has been implemented. The domestic TMDL established a basic plan for calculating the load which complies with the unit watershed's target water quality, as well as an implementation plan for annual load management, both which have been institutionalized in order to evaluate load compliance on a repeated annual basis. Local governments ask external organizations to conduct investigations every year in order to assess the transition, which thereby requires tens of millions of won every year. Therefore, an assessment and management model that can be easily operated at the TMDL personnel level is required. In this study, when the Han river Water System TMDL was implemented in earnest, we confirmed the the water quality improvement effect when TMDL was introduced to major inflow tributaries (TancheonA, JungnangA, AnyangA) under the Seoul City's jurisdiction through the use of the total amount control unit basin evaluation technique. By presenting customized management measures, we propose the guidelines that are necessary for determining more effective water environmental policies.

Characteristics of the Multi-kW Class Polymer Electrolyte Membrane Fuel Cell Stack for a Hybrid Electric Golf Cart

  • I.H. Oh;S.J. Shin;J.H. Jo;Park, S.K.;H.Y. Ha;S.A. Hong;S.Y. Ahn;Lee, Y.C.;S.A. Cho
    • Journal of Energy Engineering
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    • v.11 no.3
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    • pp.254-261
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    • 2002
  • The fabrication method for the main components of the polymer electrolyte membrane fuel cell stack such as electrodes, membrane-electrode assemblies, and bipolar plates was established for the effective electrode area of 240 ㎠. A counter-flow type 100-cell stack was fabricated by using the above components and then a maximum power of 7.44 kW for H$_2$/O$_2$ and 5.56 kW for H$_2$/air could be obtained at 70$\^{C}$ and 1 atm. It was seen that the distribution of the OCV for unit cells in the stack was uniform but the voltage deviation increased as the load increased due to the IR drop and the electrode polarization. The stack was applied to the power source of the fuel cell/battery hybrid electric golf car. It produced about 1 kW at a room temperature operation during the test run, which occupied about 43% of the total power required by the 2.3 kW motor.