• 제목/요약/키워드: specific discharge

검색결과 611건 처리시간 0.026초

수리학적 홍수추적에 의한 댐 방류시 하류수위 및 주요 하도구간별 홍수도달 시간의 예측 (Forecasting of Peak Flood Stage at Downstream Location and the Flood Travel Time by Hydraulic Flood Routing)

  • 윤용남;박무종
    • 물과 미래
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    • 제25권3호
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    • pp.115-124
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    • 1992
  • 상류댐에서의 홍수량에 의한 하류지점에서의 첨두 홍수량과 홍수 도달 시간은 수리학적 홍수추적방법에 의해 계산될 수 있다. 본 연구는 한강 유역의 전구간을 대상으로 시행되었다. 계산된 춤두 홍수량과 댐사이의 홍수도달시간은 상류에서의 방류계속시간과 바류량의 크기에 관련되어 있고 각 댐구간 사이에서 이 관계를 이용하여 다중회기모형을 제안하였다. 댐하류에서의 첨두홍수량은 수위-유량 관계식에 의해서 첨두홍수위로 변환될 수 있다. 그러므로, 제안된 다중회기모형은 상류댐에서의 홍수 방류량과 방류 계속시간에 의한 하류지점에서의 첨두홍수위와 댐구간 사이의 홍수도달시간을 예측하는데 이용될 수 있을 것이다.

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대동맥 축착증 수술 1례 (A Case of Coarctation of the Aorta)

  • 노중기
    • Journal of Chest Surgery
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    • 제11권3호
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    • pp.321-325
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    • 1978
  • Coarctation of the aorta was rare condition among the congenital cardiovascular defects in Korea. We experienced a case of coarctatlon of the aorta [postductal type], which was successfully corrected by resection and end to end anastomosis. This patient, 21 years male patient, was admitted to the medical department for evaluation of hypertension, headache and exertional dyspnea during 4 years, and transferred to the department of chest surgery for operation. On physical examination, blood pressures were measured on both extremity, measuring 190/100mmHg on the arm and 100/80mmHg on the leg. Systolic murmur was heard on 2nd to 3rd left intercostal space and left sternal border. On simple chest x-ray, rib notching was seer/on low border of right 3rd and left 4th rib. Final preoperative diagnosis was made by the retrograde aortic catheterization and aortography, which showed the typical configuration of postductal type of coarctation with poststenotic dilatation of the aorta. On 20th, July, 1978, under the general anesthesia with endotracheal intubation, resection of coarctation of the aorta and end to end anastomosis was performed. During clamp for resection, blood pressure of upper extremity was elevated to 200/140mmHg, and controlled by Arfornad. During recovery, blood pressure over 160ramrig in systole was controlled by Reserpine for 8days postoperatively. At discharge, postoperative 8th day, brachial and femoral artery pressure was 145/85 mmHg and 135/80mmHg. After discharge, there was no evidence of specific symptoms and hypertension without antihypertensive drug.

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Exit Flow Measurements of a Centrifugal Pump Impeller

  • Hong, Soon-Sam;Kang, Shin-Hyoung
    • Journal of Mechanical Science and Technology
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    • 제16권9호
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    • pp.1147-1155
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    • 2002
  • Discharge flows from a centrifugal pump impeller with a specific speed of 150 [rpm, m$^3$/min, m] were experimentally investigated. A large axisymmetric collector instead of a volute casing was installed to obtain circumferentially uniform flow, i.e. without interaction of the impeller and the volute. The unsteady flow was measured at the impeller exit and vaneless diffuser using a hot film probe and a pressure transducer. The flow at impeller exit showed pronounced jet-wake flow patterns. The wake, which was on the suction/hub side at high flow rate, became enlarged pitchwisely on both the hub and the shroud side as the flow rate decreases. The pitchwise non-uniformity of the flow rapidly decreased along the downstream and the non-uniformity almost disappeared at radius ratio of 1.18 for medium flow rate. The mean vaneless diffuser flow was reasonably predicted using a one dimensional analysis when an empirical constant was used to specify the skin friction coefficient. The data can be used for a centrifugal pump impeller design and validation of CFD codes and flow modeling.

Re-synthesis and Electrochemical Characteristics of LiFePO4 Cathode Materials Recycled from Scrap Electrodes

  • Kim, Hyung Sun;Shin, Eun Jung
    • Bulletin of the Korean Chemical Society
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    • 제34권3호
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    • pp.851-855
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    • 2013
  • This paper describes an environmentally friendly process for the recovery of $LiFePO_4$ cathode materials from scrap electrodes by a simple thermal treatment method. The active materials were easily separated from the aluminum substrate foil and polymeric binders were also decomposed at different temperatures ($400^{\circ}C$, $500^{\circ}C$, $600^{\circ}C$) for 30 min under nitrogen gas flow. The samples were characterized by X-ray diffraction (XRD), scanning electronic microscopy (SEM), Raman spectroscopy, Thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). The electrochemical properties of the recycled $LiFePO_4$ cathode were evaluated by galvanostatic charge and discharge modes. The specific charge/discharge capacities of the recycled $LiFePO_4$ cathode were similar to those of the original $LiFePO_4$ cathode. The $LiFePO_4$ cathode material recovered at $500^{\circ}C$ exhibits a somewhat higher capacity than those of other recovered materials at high current rates. The recycled $LiFePO_4$ cathode also showed a good cycling performance.

화력발전소 보일러 급수용 펌프 배관계의 이상소음 저감에 관한 연구 (Study on Noise Control for Piping System of BFP in a Power Plant)

  • 양경현;조철환;배춘희
    • 한국소음진동공학회:학술대회논문집
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    • 한국소음진동공학회 2004년도 춘계학술대회논문집
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    • pp.490-494
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    • 2004
  • The purpose of this paper was to identify the mechanism that caused abnormal vibration and noise on the piping system connected to discharge flow of BFP(Boiler Feed water Pump) in a coal fired power plant, and to develop the device that can reduce the level of abnormal vibration and noise. Major results of this project can be summarized as follows: First, we analyzed the acoustic mode for the discharge piping of BFP to trace a path of the noise, and assumed that noise and vibration on the piping system can be related with length of pipe. Second, a minimized model of the piping system was set up to simulate abnormal vibration and noise within the specific range of operating frequencies, and as a result we confirmed that the acoustic mode affected the piping system considerably. Finally the test device which can reduce the level of abnormal noise and vibration was built to verify validity applying for the piping system. Then we concluded that the noise and vibration generated from the piping system was attributed to the acoustic resonance in piping system, and so developed new device which can reduce the level of noise and vibration under 40%. Put Abstract here.

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Hydrodynamic performance of a pump-turbine model in the "S" characteristic region by CFD analysis

  • Singh, Patrick Mark;Chen, Chengcheng;Choi, Young-Do
    • Journal of Advanced Marine Engineering and Technology
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    • 제39권10호
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    • pp.1017-1022
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    • 2015
  • Specific hydrodynamic characteristic of pump-turbine during the start and load rejection process of generating mode causes anomalous increase of water pressure, along with large machine vibration, called "S" characteristic. The aim of this study is to understand and explain the hydrodynamic performance of pump-turbine at "S" characteristic region by using a model of pump-turbine system. The operation in the condition of runway and low discharge in a typical "S" characteristic curve may become unstable and complex flow appears at the passage of guide vane and impeller. Therefore, velocity and pressure distribution are investigated to give an all-sided explanation of the formation and phenomenon of this characteristic, with the assistance of velocity triangle analysis at the impeller inlet. From this study, the internal flow and pressure fluctuation at the normal, runway and low discharge points are explored, giving a deep description of hydrodynamic characteristic when the pump-turbine system operates with "S" characteristic.

22.9 kV XLPE 전력케이블에서 부분방전 측정을 위한 Planar Patch Sensor 설계 및 제작 연구 (A Study on the Design and Fabrication for Partial Discharge Measurement in 22.9kV XLPE Power Cable using Planar Patch Sensor)

  • 임광진;양상현;;박노준;박대희
    • 한국전기전자재료학회:학술대회논문집
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    • 한국전기전자재료학회 2008년도 하계학술대회 논문집 Vol.9
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    • pp.265-266
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    • 2008
  • The objective of this paper is to effectively detect partial discharges in XLPE power cables. In this field, we have been usually applied several sensors for such partial discharges. This study used a type of beyond compare antenna based on the influence of background noises. Also, we designed a new structure that is able to easily apply in the adhesion of planar patch types for XLPE power cables in measurement sensitiveness elevation. A high frequency simulation tool (CST-MWS) was applied to the antenna used in this study, and it was used to evaluate certain characteristics. We fabricated an antenna using the simulation data obtained from a specific test. After checking the sensitivity of this Planar Patch Sensor in the Lab, it was tested in an actual site. This paper analyzed the data as a part of time and frequency domain using an oscilloscope and spectrum analyzer, respectively.

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하천폭의 국부적 축소 및 확대에 따른 수리특성 연구 (A Study of the Stream Specific by River Width's Downsizing & Extension)

  • 최한규;김주석;백효선
    • 산업기술연구
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    • 제27권B호
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    • pp.229-233
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    • 2007
  • This research investigated the way of generating the flowing of water in case of artificial fluctuation of river width by the unidimensional numerical analysis in order to reconstruct vertical and expanse features of flowing, and the problem of existing numerical analysis in accordance with local enlargement and reduction of river through hydraulic model experiments with results of numerical analysis. The result revealed that when the local section change in the same river is exist, it showed 0.93m in the case of no change of local section in the hydraulic model experiments and numerical analysis, however, it presented 1.645m on the occasion of local section changes in the hydraulic model experiments and numerical analysis. In other words, there was a significant difference in the existing numerical analysis, when there was a local section change. As a result of the experimental section for the enlargement and reduction of local river width, due to the sensitive change for fluctuation of flood discharge, there was a significant difference between numerical analysis and hydraulic model experiments. In addition, the result of comparison between the enlargement and reduction of local river width confirmed that the result of numerical analysis with hydraulic model experiments showed larger generation of deviation in case of enlargement of section than in case of reduction of section.

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Characterization of Electric Double-Layer Capacitor with 0.75M NaI and 0.5 M VOSO4 Electrolyte

  • Chun, Sang-Eun;Yoo, Seung Joon;Boettcher, Shannon W.
    • Journal of Electrochemical Science and Technology
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    • 제9권1호
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    • pp.20-27
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    • 2018
  • We describe a redox-enhanced electric double-layer capacitor (EDLC) that turns the electrolyte in a conventional EDLC into an integral, active component for charge storage-charge is stored both through faradaic reactions with soluble redox-active molecules in the electrolyte, and through the double-layer capacitance in a porous carbon electrode. The mixed-redox electrolyte, composed of vanadium and iodides, was employed to achieve high power density. The electrochemical reaction in a supercapacitor with vanadium and iodide was studied to estimate the charge capacity and energy density of the redox supercapacitor. A redox supercapacitor with a mixed electrolyte composed of 0.75 M NaI and 0.5 M $VOSO_4$ was fabricated and studied. When charged to a potential of 1 V, faradaic charging processes were observed, in addition to the capacitive processes that increased the energy storage capabilities of the supercapacitor. The redox supercapacitor achieved a specific capacity of 13.44 mAh/g and an energy density of 3.81 Wh/kg in a simple Swagelok cell. A control EDLC with 1 M $H_2SO_4$ yielded 7.43 mAh/g and 2.85 Wh/kg. However, the relatively fast self-discharge in the redox-EDLC may be due to the shuttling of the redox couple between the polarized carbon electrodes.

22.9kV급 지중전력케이블의 부분방전 측정을 위한 평면루프센서 설계 및 제작 연구 (A Study on the Design and Fabrication for Partial Discharge Measurment in 22.9kV Underground Power Cable using Planar Loop Sensor)

  • 신동훈;임광진;;박노준;박대희
    • 한국전기전자재료학회:학술대회논문집
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    • 한국전기전자재료학회 2007년도 추계학술대회 논문집
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    • pp.210-211
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    • 2007
  • The objective of this paper is to effectively detect partial discharges in underground power cables. In this field, we have been usually applied several sensors for such partial discharges. This study used a type of beyond compare antenna based on the influence of background noises. Also, we designed a new structure that is able to easily apply in the adhesion of planar loop types for underground power cables in measurement sensitiveness elevation. A high frequency simulation tool (CST-MWS) was applied to the antenna used in this study, and it was used to evaluate certain characteristics. We fabricated an antenna using the simulation data obtained from a specific test. After checking the sensitivity of this Planar Loop Sensor in the Lab, it was tested in an actual site. This paper analyzed the data as a part of time and frequency domain using an oscilloscope and spectrum analyzer, respectively.

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