• 제목/요약/키워드: low-loss

검색결과 5,088건 처리시간 0.036초

입사각의 변화에 따른 터빈 캐스케이드에서 손실계수에 관한 실험적 연구 (An Experimental Study on Loss Coefficient of Turbine Cascade with Incidence Angles)

  • 이주형;허원회;전창수
    • 한국유체기계학회 논문집
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    • 제2권4호
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    • pp.48-56
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    • 1999
  • For the study on loss coefficients of turbine cascade with variation of incidence angle, the wind-tunnel tests were performed under the ranges in velocity of 10 m/s, 15 m/s, 20 m/s and incidence angles from $-20^{\circ}\;to\;20^{\circ}$ by intervals of $5^{\circ}$. Comparing our results with Soderberg's prediction, differences in loss coefficient were $2.5\%\;and\;2.8\%$ each for 10 m/s and 15 m/s. A large disagreement of $30.3\%$ was showed at 20 m/s freestream velocity. The comparisons of these test results with Ainley's prediction showed an $8\%$ difference in the case of 20 m/s freestream velocity. Test results were approximately comparable with Ainley's loss prediction's in incidence angles. Generally, averaged total pressure loss seemed to be decreased as Reynolds number increased. The total pressure loss coefficients were increased parabolically, as incidence angles were increased negatively and positively from $0^{\circ}$, in all speed ranges. At the far low freestream velocities, minimum loss accurred between $-5^{\circ}\;and\;+5^{\circ}$. But this minimum range narrowed the location of this range by shifting to the direction of the angle as freestream velocity was increased.

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Measurement of magnetization loss according to the winding pitch of CORC®

  • Han, Jinwoo;Choi, Kyeongdal;Kim, Woo-Seok;Lee, Ji-Kwang
    • 한국초전도ㆍ저온공학회논문지
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    • 제23권4호
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    • pp.25-29
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    • 2021
  • For the application of HTS wire to AC power equipment, a conductor with high current capacity and low loss is required. CORC®, one of the high-current conductors manufactured using several HTS wires, is made by winding the wires in a spiral on a cylindrical former. Because the magnetization loss of a CORC® conductor depends on the degree of magnetic coupling between the wires constituting the CORC®, it is necessary to know the value of the magnetization loss of the CORC® itself. In order to obtain an accurate loss value, it is necessary to know the effect of the ratio of the winding pitch of the CORC® conductor in the pickup coil region sampling the magnetization loss signal. To confirm this effect, we prepare CORC® samples having various winding pitches, and measure and compare the magnetization losses. In addition, the magnetization loss was measured while rotating the CORC® samples and it was examined whether there was a difference in the magnetization loss according to the rotation.

WiFi와 BLE 를 이용한 Log-Distance Path Loss Model 기반 Fingerprint Radio map 알고리즘 (Radio map fingerprint algorithm based on a log-distance path loss model using WiFi and BLE)

  • 성주현;권택구;이승희;김정우;서동환
    • Journal of Advanced Marine Engineering and Technology
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    • 제40권1호
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    • pp.62-68
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    • 2016
  • 실내 위치인식 기술 중 하나인 WiFi Fingerprint는 기존의 WiFi access point(AP)의 거리에 따른 신호 세기를 활용하여 위치를 추정하는 편리함 때문에 많은 연구가 이루어지고 있다. 하지만 이 방식은 Radio map에 저장된 Reference point에 의존하기 때문에 다른 방식에 비해 위치의 분해능이 떨어지고 연산량이 많다. 본 논문에서는 이러한 문제를 해결하기 위하여 WiFi와 BLE를 융합한 Log-Distance Path Loss Model 기반의 Radio map 설계 알고리즘을 제안한다. 제안한 알고리즘은 Log-Distance Path Loss Model이 적용된 변수 값을 추출하여 Radio map을 설계하는 방식이며 Median Filter를 적용하여 오차를 개선하였다. 기존 Fingerprint와 비교하여 실험한 결과, 위치의 정확도는 평균 2.747m에서 2.112m로 0.635m 감소되는 것을 확인하였으며 연산량은 AP 환경에 따라 33%이상 감소하는 것을 확인하였다.

당뇨 환자의 체중감량을 위한 가미태음조위탕의 임상적 활용: 후향적 차트 리뷰 (Gamitaeeumjowee-Tang for weight loss in diabetic patients: A retrospective chart review)

  • 이아름;이다연;김민지;이향숙;최가혜;김서영;임영우;박영배
    • 대한한의학회지
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    • 제42권1호
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    • pp.46-58
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    • 2021
  • Objectives: The purpose of this study is to report weight changes and analyze adverse events in diabetic patients with Gamitaeeumjowee-Tang for weight loss. Methods: A retrospective chart review of weight change and adverse events was performed during the 10-week weight loss program using Gamitaeeumjowee-tang with low-calorie diets for diabetics(n=61). Weight and BMI changes were compared before and after the program and calculated the percentage of people who lost more than 5% of their weight, also identified whether subjects felt satiated or not. Adverse events were evaluated in terms of causality, severity and system-organ classes. Results: After 10-week weight loss program, significant weight loss (5.9±2.32kg, 7.73% reduction from baseline) and BMI reduction (2.9±0.86) were reported (n=61). Those who lost more than 5 percent of their body weight accounted for 88.5%, and also 88.5% of the participants felt full to help control their appetite. In assessing the causality of adverse events, 'Unlikely' was the most common (66%) and in severity evaluations, almost all symptoms were mild. Insomnia was the most frequently reported during the first 8 weeks, and constipation was reported the most afterwards. Conclusions: A combination of Gamitaeeumjowee-tang and low-calorie diets for 10 weeks appears to help weight reduction without serious adverse events in diabetic patients. Future well-designed prospective clinical studies testing the effectiveness and safety of this weight loss program are warranted.

Measurement and Analysis of Loss in Optical Directional Couplers

  • Leepila, R.;Jangsilp, R.;Noppanakeepong, S.
    • 제어로봇시스템학회:학술대회논문집
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    • 제어로봇시스템학회 2004년도 ICCAS
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    • pp.484-487
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    • 2004
  • Symmetric directional couplers are widely used in interferometers, switches, and various signal processing devices. Recently, several optical couplers using multimode fibers were reported, but these suffer from inefficient coupling of light into a branching fiber and/or low directivity. This paper presents the measurement and analysis of loss in the connection of optical fibers via the optical directional couplers. The functionality of the device is based on the principle that is symmetrical, the power in excited mode can be unambiguously directed into one of the output channel by varying and of its parameters. In this experiment, we measure the power of loss in the optical directional coupler at various radius of curvature. Before the measurement of loss in x-coupler, we polish the contact of the fiber surface in order that light can penetrate through another port. The results show that, when the radius of curvature is increased, the loss power is decreased and also approaches of the straight line case.

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22.9kV 배전선로 전력손실산출 기법에 관한 연구 (A Study on Calculation Method of Power Losses in 22.9kV Power Distribution Lines)

  • 황인성;홍순일;문종필
    • 전기학회논문지P
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    • 제66권4호
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    • pp.219-223
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    • 2017
  • In this paper, we calculated the losses in the high voltage lines of power distribution system. The losses caused by high voltage lines are calculated using maximum current, resistance, loss factor, and dispersion loss factor. The accurate extraction of these factors are very important to calculate the losses exactly. Thus, the maximum loads are subdivided to regions and calculated monthly for more accurate maximum current calculation. Also, the composite resistance is calculated according to the ratio of the used wire types. In order to calculate the loss factor, the load factors according to the characteristics of each region were calculated. Finally, the losses of the distribution system is calculated by adding the losses by the transformers and the low voltage lines.

무효전력 손실감도를 이용한 정적 전압 안정도 해석 (Static Voltage Stability Analysis using Reactive Power Loss Sensitivity)

  • 김원겸;이복용;이상철
    • 대한전기학회:학술대회논문집
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    • 대한전기학회 1999년도 추계학술대회 논문집 전문대학교육위원 P
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    • pp.52-55
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    • 1999
  • In recent years, much attention has been paid to the voltage collapse phenomena. There has been reported many cases about the voltage collapse in many countries. These voltage collapse phenomena are known as the event that can occur due to reactive power deficits. This paper proposes an efficient method that can pursue the reactive power loss changes and gives the simple voltage collapse proximity indicator(VCPI) based on the reactive power loss sensitivities using optimal techniques. By comparing reactive power loss sensitivity with active power loss sensitivity, it is also proved that VCPI based on reactive power loss sensitivities is more effective. The developed VCPI is derived from the Jacobian matrix of Load Flow and the computational burden is very low and on-line implementation is possible. The proposed method is applied to a IEEE-14 bus test system and reliable and promising results are obtained.

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광섬유 접속기 실습을 통한 공학 교육 연구 (A study of the Engineering Education Method Using Fiber Optic Splicing Experiments)

  • 이승홍;이종길
    • 한국실천공학교육학회논문지
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    • 제2권1호
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    • pp.42-46
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    • 2010
  • 공학교육의 한 방법으로 광섬유 센서 제작 시 반드시 필요한 광섬유 접속기 사용은 보다 감도가 높은 센서를 제작하는데 필수적이다. 본 연구에서는 광섬유 접속기를 이용한 광 접속 손실을 실제 실험을 통하여 평가하고 실습에 사용된 방법이 교육적 효과를 거두기 위한 여러 가지 요소들을 분석하였다. 많은 실습을 통하여 광접속기 손실은 실습지들의 학습태도와 실험 환경의 변화에 많이 의존됨을 확인하였다.

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ATM 망에서 공평한 지연 및 손실 우선순위 제어 (Fair delay and loss priority control in ATM networks)

  • 박창욱;임인칠
    • 전자공학회논문지A
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    • 제33A권6호
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    • pp.23-32
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    • 1996
  • This paper proposes a new buffer management scheme to service delay-sensitive traffic and loss-sensitive traffic fairly in ATM networks. The proposed scheme uses tow buffers for delay-sensitive traffic and loss-sensitive traffic. To satisfy the average delay time of delay-sensitive traffic, cells in real-time buffer are served first. When congestion occurs in nonreal-time buffer, low loss priority cell in real-time buffer can be pushed out by high loss priority cell in nonreal-time buffer can be transferred to real-time buffer considering threshold value in real-time buffer. Using computer simulation, the existing methods and proposed scheme are compared and analyzed with respect to cell loss rate and average delay time. Simulation results show that the proposed scheme have superior performance to conventional schemes.

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Study of Optimal Location and Compensation Rate of Thyristor-Controlled Series Capacitor Considering Multi-objective Function

  • Shin, Hee-Sang;Cho, Sung-Min;Kim, Jin-Su;Kim, Jae-Chul
    • Journal of Electrical Engineering and Technology
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    • 제8권3호
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    • pp.428-435
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    • 2013
  • Flexible AC Transmission System (FACTS) application study on enhancing the flexibility of AC power system has continued to make progress. A thyristor-controlled series capacitor (TCSC) is a useful FACTS device that can control the power flow by adjusting line impedances and minimize the loss of power flow and voltage drop in a transmission system by adjusting line impedances. Reduced power flow loss leads to increased loadability, low system loss, and improved stability of the power system. This study proposes the optimal location and compensation rate method for TCSCs, by considering both the power system loss and voltage drop of transmission systems. The proposed method applies a multi-objective function consisting of a minimizing function for power flow loss and voltage drop. The effectiveness of the proposed method is demonstrated using IEEE 14- and a 30-bus system.