• 제목/요약/키워드: Flow Impedance

검색결과 235건 처리시간 0.024초

온도특성을 고려한 저압간선의 경제적인 설계기법에 관한 연구 (A Study on the Economical Design of Low-Voltae feeder Considering the temperature character)

  • 최홍규;조계술
    • 한국조명전기설비학회:학술대회논문집
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    • 한국조명전기설비학회 2002년도 학술대회논문집
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    • pp.349-354
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    • 2002
  • A size of low-voltage conductor cables is determined by the voltage drop of a system, the cable impedance and the cable ampacity based on temperature correction factor in accordance with the condition of cable installation. Therefore, the proper temperature correction factor according to the condition of cable installation should be applied to determining the cable ampacity and also the skin effect and proximity effect, along with the kind and size of conductor and the condition of cable installation, should be properly considered to analyze the proper value of resistance and the reactance of the conductors. This paper addresses the systematic design flow for determining the size of low voltage level conductor cables in calculating the temperature character where error should be minimized in comparison with the general formula and which can be applied in design work for determining the size of conductor cables.

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Electrical Resistance Tomography: Mesh Grouping and Boundary Estimation Algorithms

  • Kim Sin;Cho Hyo-Sung;Lee Bong-Soo
    • International Journal of Contents
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    • 제1권1호
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    • pp.1-5
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    • 2005
  • This paper presents the development and application of electrical resistance imaging techniques for the visualization of two-phase flow fields. Two algorithms, the so-called the mesh grouping and the boundary estimation, are described for potential applications of electrical resistance tomography (ERT) and results from extensive numerical simulations are also presented. In the electrical resistance imaging for two-phase flows, numerical meshes fairly belonging to each phase can be grouped to improve the reconstruction performance. In many cases, the detection of phase boundary is a key subject and a mathematical model to estimate phase boundary can be formulated in a different manner. Our results indicated that the mesh grouping algorithm is effective to enhance computational performance and image quality, and boundary estimation algorithm to determine the phase boundary directly.

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심장운동부하 모델링과 의료장비 개발 (Modeling for the Work of Heart and Development of the WOH Medical device)

  • 노형운;서상호
    • 유체기계공업학회:학술대회논문집
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    • 유체기계공업학회 2006년 제4회 한국유체공학학술대회 논문집
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    • pp.501-504
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    • 2006
  • The estimation of the work of heart can be treated as one of the most important parameters for determining the amount of circulating blood needed for harmonious metabolism in the human body. By monitoring the work of heart, one can detect increased work load of heart and start the treatment at the early stage of CHF. Thus it is necessary to estimate the work of heart. The contractility of the left ventricle, the second important parameter for representing the motion of heart, can be estimated through information on the work of heart. In this study, the modified Windkessel model, which has been used for a measure of vascular hemodynamic impedance parameters, was adapted to estimate the work of heart.

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인후두역류질환의 실험실 검사의 재평가 (Inquiry into the Laboratory Diagnostic Tests in Larygopharyngeal Reflux Disease)

  • 김한수
    • 대한후두음성언어의학회지
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    • 제18권2호
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    • pp.102-107
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    • 2007
  • Laryngopharyngeal reflux disease (LPRD) is the result of retrograde flow of gastric contents to the laryngopharynx. Laryngoscopic findings and special questionnaires are first step of diagnosis of LPRD. Empiric trials of Proton pump inhibitor' test (PPI test) is recommended as treatment and diagnosis. However confirmation of reflux is then recommended primarily in patients with persistent symptoms despite acid-suppressive therapy. The 24 hour ambulatory double pH monitoring has been a gold standard method in diagnosis of LPRD even though it has some limitation. The combined multichannel intraluminal impedance and pH monitoring is a new-rising test tool. It can detect acid/non-acid, liquid/gaseous reflux and clearance of refluxate. The water siphon test is also used for diagnosis of LPRD.

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영상회로를 이용한 병행 송전선로에서의 고장점 추정 알고리즘 (Fault Location Algorithm in Parallel Transmission Line Using Zero Sequence Network)

  • 박홍규;이재규;유석구
    • 대한전기학회:학술대회논문집
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    • 대한전기학회 1999년도 추계학술대회 논문집 학회본부 A
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    • pp.282-284
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    • 1999
  • This paper presents an accurate algorithm for fault location of a single phase to earth fault on a two-parallel transmission line using only one-terminal data. It is impossible to calculate the accurate fault distance, because of the unknown fault resistance and fault current at the fault point. The faulted line circuit and the zero-sequence circuit of two-parallel line are used as a fault location model, which the source impedance of the remote end is not involved. The algorithm can eliminate the effect of load flow and the fault resistance in calculating the fault location.

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동심관형 공명기 내부의 천공 요소의 불규칙한 배열이 전달손실 및 배압에 미치는 특성 연구 (Effect of nonuniform perforation in the concentric resonator on the transmission loss and back pressure)

  • 이성현;;이정권
    • 한국소음진동공학회:학술대회논문집
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    • 한국소음진동공학회 2002년도 춘계학술대회논문집
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    • pp.515-519
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    • 2002
  • 자동차 및 유체기계의 흡기계나 배기계에 사용되는 소음기의 음향성능은 전달손실로 기계성능은 배압으로 표현된다. 유체가 흐르는 관 사이의 임피던스 부정합을 이용하는 반사형 소음기의 경우, 내부 유로에 천공을 주어 음향감쇠를 시키거나 유동을 안정시키는 경우가 많다. 본 연구에서는 동심관형 공명기의 내부 관에 존재하는 천공의 분포 양상이 소음기의 전달손실과 배압에 미치는 영향을 실험을 통하여 고찰하였다. 내부관의 평균 천공율은 일정하지만 길이 방향을 따라서 천공율이 변하는 다섯가지의 공명기에 대한 실험을 수행하고, 성능에 미치는 영향을 살펴보았다. 전달손실은 천공요소의 임피던스 모델을 고려하여 예측한 결과와 비교하였고, 측정된 배압은 모의 해석 결과와 비교하였다. 분석 결과, 천공율이 점점 작아지는 분포나, 작았다가 커진후 다시 작아지는 형태의 분포를 가질 경우, 배압 측면에서 매우 유리하고, 음향 전달손실도 큰 차이가 없음을 밝혔다.

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유체기인 방사소음 저감용 소음기 개념설계 이론 (CONCEPT DESIGN THEORY OF SHOCK ABSORBING MUFFLERS FOR AIR-BORNE NOISE)

  • Kim, Sang-Myeong
    • 한국소음진동공학회:학술대회논문집
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    • 한국소음진동공학회 2002년도 춘계학술대회논문집
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    • pp.627-632
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    • 2002
  • The paper considers acoustic analysis of the shock absorbing muffler within a rotary compressor. The internal space of the compressor is modelled as a combination of cavities and pipes. A simple one-dimensional impedance approach is used fur the acoustic analysis in the low frequency range, with ignoring the effects of gas flow and temperature gradients that are closely related to power efficiency of the compressor. Using the similarity between the vibration isolator and the shock absorbing muffler, the source strength transmissibility is newly proposed as a performance measure of the muffler and its validity is supported by power analysis. Some Important muffler design rules obtained are; (1) a muffler cavity and its opening throat should be used as a pair, (2) a long thin throat is desirable for high frequency noise isolation, (3) a large muffler cavity should be used with care since it shortens the working frequency range of the muffler. The rules were applied to redesign a compressor muffler currently in use, and a significant improvement was achieved by simply attaching a throat to the outlet holes of the muffler.

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전기 저항법을 이용한 Micro Particle Counter Micro Fluidic Device 개발

  • 이준;윤덕원;채호철;한창수
    • 한국반도체및디스플레이장비학회:학술대회논문집
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    • 한국반도체및디스플레이장비학회 2005년도 춘계 학술대회
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    • pp.134-138
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    • 2005
  • Recently many researches related with biotechnology are processed and it is the situation that research about micro fluidic devices is active. Micro fluidic devices has been one of the most widely used devices for the analysis in biotechnology because they have many advantages, flexibility, transparency, thermal and electrical stability, nontoxic, etc. In this study, micro fluidic device with PDMS is developed for particle counter which separates a small quantity of particles, The principle of micro particle counter is electrical-impedance method, and it was also applied hydrodynamic flow focusing. It is more efficient method to analyzing particles furthermore it can be applied to cell count ins for biotechnology.

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빔형성 기법을 이용한 공동수조 내부의 소음원 탐지 (Detection of Noise Sources in a Cavitation Tunnel by using Beam-Forming Method)

  • 이정학;서종수
    • 한국소음진동공학회:학술대회논문집
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    • 한국소음진동공학회 2003년도 춘계학술대회논문집
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    • pp.749-754
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    • 2003
  • In this paper, we introduce the measurement of the underwater noise with 32channel hydrophone array of Samsung CAvitation Tunnel (SCAT) and the detection technique of noise sources by using the beam-forming method. Measurement and way signal Processing under fluid flow are essential works for the underwater acoustics, especially for the detection of noise sources. As the acoustic impedance of the water is relatively high and the tunnel is an enclosed system, we have to consider the interaction between tunnel and water together with the reflection of noise in the beam-forming technique. Also, for a hydrophone array system that is fixed on one side of tunnel wall as done in SCAT is liable to suffer from some limitations in the detection of the noise sources with the array, we discuss these limitations particularly on the frequency range and spacing of noise sources.

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Reconfigurable Circularly Polarized Microstrip Antenna on a Slotted Ground

  • Yoon, Won-Sang;Han, Sang-Min;Pyo, Seong-Min;Lee, Jae-Hoon;Shin, In-Chul;Kim, Young-Sik
    • ETRI Journal
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    • 제32권3호
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    • pp.468-471
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    • 2010
  • A compact square patch antenna with reconfigurable circular polarization (CP) at 2.4 GHz is proposed. Circular polarization is generated by an arc-shaped slot on the ground plane. In order to switch the CP orientation, the current flow direction of the patch is reconfigured via the PIN diodes mounted on the slot. As the slot and bias circuit are not placed on the patch side, the proposed antenna radiates a CP wave without alteration in the main beam direction. From the experimental results, the impedance and CP bandwidths of the proposed antenna have been demonstrated for up to 80 MHz and 25 MHz, respectively.