• 제목/요약/키워드: Rotating Time

검색결과 829건 처리시간 0.023초

구속된 단일 회전원판과 동시 회전원판 내부의 유동 특성 (Flow Characteristics in a Cavity Due to a Single Rotating Disk and Co-Rotating Disks)

  • 원정호;류규영;조형희
    • 대한기계학회논문집B
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    • 제23권9호
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    • pp.1192-1200
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    • 1999
  • The present study investigates flow characteristics in a cavity with one rotating disk and co-rotating disks for application to HDD. The experiments are conducted for rotating Reynolds numbers of $5.5{\times}104$ to $1.10{\times}105$ and for gap ratios of 0.059 to 0.175 in a single rotating and 0.047 to 0.094 in co-rotating disk. Time-resolved velocity components and turbulence intensity on the rotating disks are obtained by using LDA measurements. Detailed Knowledge of the flow characteristics is essential to analyze flow vibration and heat transfer and to design head-arm assembly and hub height in HDD. The results indicate that the velocity field in HDD is changed largely by the rotating Reynolds numbers and hub height of the disk.

빔 형성 방법을 이용한 회전하는 음원의 위치 판별에 관한 연구 (Localization of Rotating Sound Sources Using Beamforming Method)

  • 이재형;홍석호;최종수
    • 한국소음진동공학회:학술대회논문집
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    • 한국소음진동공학회 2004년도 춘계학술대회논문집
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    • pp.837-842
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    • 2004
  • The positions of rotating sound sources have been localized by experiments with the Doppler effects removed. In order to do-Dopplerize the sound signals emitted from moving sources, two kinds of signal reconstruction methods were applied. One is the forward propagation method and the other is the backward propagation method. Forward propagation method analyze the source emission time based on the instantaneous distance between sensors and the assumed source position, then the signals are reconstructed with respect to the emission time. On the other hand, the backward method uses time delay to do-Dopplerize the acquired data for the received time of reference. In both techniques, the reconstructed signal data were processed using beamforming algorithm to produce power distributions at the frequency of interest. Experiments have been carried out for varying frequencies, rotating speeds and the object distances. Forward propagation method has shown better performance in locating source position than the backward propagation method.

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CFD를 이용한 머드 탱크 2축 교반기의 회전방향에 따른 교반성능 연구 (Agitation Performance Study of 2-shafts Agitator Rotate Directio in the Mud Tank Based on CFD)

  • 임효남;이희웅;이인수;최재웅
    • 한국해양공학회지
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    • 제28권2호
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    • pp.111-118
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    • 2014
  • In drilling process of oil wells, the drilling fluid such as mud keeps the drill bit cool and clean during drilling, with suspending drill cuttings and lubricating a drill bit. In this paper, a commercial CFD package(ANSYS Fluent 15.0) was used to solve the hydrodynamic force and evaluate mud mixing time in the mud mixing tank on offshore drilling platforms. Prediction of power consumption in co-rotating and counter-rotating models has been compared with results of Nagata's correlation equation. This research shows the hydrodynamic effect inside the two phase mud mixing tank according to rotating directions(co-rotating and counter-rotating). These results, we can conclude that the co-rotating direction of the two shafts with mixing blade in the mud mixing tank can be a preferable in power consumption and mixing time reduction.

원심압축기 깃 없는 디퓨저에서의 선회실속에 관한 실험적 연구 (An experimental study on rotating stall in vaneless diffuser of a centrifugal compressor)

  • 신유환;김광호;손병진
    • 대한기계학회논문집B
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    • 제22권2호
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    • pp.153-161
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    • 1998
  • This study describes the results of the analysis of measured rotating stall signal in a centrifugal compressor with vaneless diffuser. Unsteady flow and rotating stall in vaneless diffuser were investigated by measuring of unsteady velocity fluctuation using hot-wire anemometer. Experiments were carried out in several impeller rotating speeds, at different radius ratios. Single hot -wire was used to study the characteristics of rotating stall. As a result, the abrupt rotating stall was detected at all measured impeller rotating speeds and the several flow coefficients which are less than 0.16. The number of the stall cell was one at all measured rotational speeds, and the rotating direction was the same as that of the impeller. As the flow rate decreased, the profile of the phase averaged radial velocity component with time changed from a sawtooth to a sine wave.

회전 창문함수를 적용한 위그너-빌 분포함수와 그 특성 (Wigner-Ville Distribution Applying the Rotating Window and Its Characteristics)

  • 박연규;김양한
    • 소음진동
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    • 제7권5호
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    • pp.747-756
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    • 1997
  • Wigner-Ville distribution which is a time-frequency analysis has a fatal drawback, when the signal has multiple components. This is the cross-talk and often causes a neagative value in the distribution. Wingner-Ville distriution is an expression of power, therefore the cross-talk must be avoided. Smoothing the Wigner-Ville distribution by convoluting it with a window, is most commonly used to reduce the cross-talk. There can be infinite number of distributions depending on the windows. But, the smoothing reduces resolution in time-frequency plane; this motives to design a more effective window in reducing cross-talk while remaining resolution. The domain in which the cross-talk and legitimate components can be easily distinguished, is the ambiguity function. In the ambiguity function domain, the legitimate components appear as linear lines passing through the orgine. But, the cross-talk is widely distributes in the ambiguity function plane. Based on the relative distributions of cross-talk and legitimate components, rotating window can be designed to minimize cross-talk. Applying the rotating window to the ambiguity function corresponds to smoothing the Wigner-Ville distribution. Therefore, the effects of rotating window is estimated in terms of the bias error due to smooting the Wigner-Ville distribution. By applying the rotating window, not only the Wigner-Ville distribution but also its properties are changed. The properties of the new distribution are checked, in order to complete analyzing the rotating window.

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고속 레일리 페이딩 채널에 적합한 개선된 초직교 시공간 격자 부호 (Improved Super-Orthogonal Space Time Codes for Fast Rayleigh Fading Channels)

  • 김창중;허서원;이호경
    • 한국통신학회논문지
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    • 제32권9C호
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    • pp.820-825
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    • 2007
  • 초직교 시공간 격자 부호(Super-Orthogonal Space-Time Trellis Codes; SOSTTC)는 직교 행렬의 집합을 확장하여 부호율의 손실 없이 부호 이득과 다이버시티 이득을 동시에 얻는 방법이다. SOSTTC에서 신호 집합 확장은 부호 행렬의 첫째 열을 회전시킴으로써 이루어진다. 기존에 사용된 회전각은 성능 개선보다 신호 성좌의 확장을 피하기 위한 목적으로 선택되었다. 본 논문에서는 고속 레일리 페이딩 채널에서 SOSTTC의 성능을 개선하기 위해 적당한 회전각을 선택하기 위한 설계 요건을 만들었다. 또한, 적당한 회전각을 사용하여 개선된 SOSTTC를 설계하였다. 그리고 모의실험을 통하여 본 논문에서 설계된 SOSTTC가 기존의 SOSTTC 보다 BER 성능 면에서 더 뛰어남을 입증하였다.

Design, Development and Analysis of Embedded Systems for Condition Monitoring of Rotating Machines using FFT Algorithm

  • Dessai, Sanket;Naaz, Zakiyaunnissa Alias Naziya
    • Journal of international Conference on Electrical Machines and Systems
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    • 제3권4호
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    • pp.428-432
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    • 2014
  • Rotating machines are an integral part of large electrical power machinery in most of the industries. Any degradation or outages in the rotating electric machinery can result in significant losses in productivity. It is critical to monitor the equipment for any degradation's so that it can serve as an early warning for adequate maintenance activities and repair. Prior research and field studies have indicated that the rotating machines have a particular type of signal structure during the initial start-up transient. A machine performance can be studied based on the effect of degradation in signal parameters. In this paper a data-acquisition system and the FFT algorithm has been design and model using the MATLAB and Simulink. The implementation had been carried out on the TMS320 DSP Processor and various testing and verification of the machine performance had been carried out. The results show good agreement with expected results for both simulated and real-time data. The real-time data from AC water pumps which have rotating motors built-in were collected and analysed. The FFT algorithm provides frequency response and based on this frequency response performance of the machine had been measured.The FFT algorithm provides only approximation about the machine performances.

회전원판을 이용한 디프드로잉용 프레스 개발에 관한 연구 (A Study on the Development of Deep Drawing Press using a Rotating Disk)

  • 황병복;강성호;김진목
    • 한국소성가공학회:학술대회논문집
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    • 한국소성가공학회 1994년도 박판성형기술의 진보
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    • pp.69-78
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    • 1994
  • A rotating disk is introduced to be applied to the deep drawing press. Several characteristics are summarized to see the basics of deep drawing of sheet metal in terms of load-stroke relationship and formability. Many conventional drawing presses, which are mostly link-type presses, are also shown to be compared with the rotating disk-type press. Performances of the new press are kinematically analyzed it terms of load-main gear angle relationship, stroke-gear angle relationship, and slide velocity-gear angle relationship and they are compared with those of conventional types', e. g. crank press and so on. The comparison show kinematically better performance of rotating disk-type press than that of conventional ones. Also, the new press are proven to be one of the best press for mass production in terms of cycle time. Applicability of the rotating disk press to deep drawing and cold forging work is introduced. The new press is described in terms of economy such that the cost of new press would be much lower than those of conventional types'.

수평회전형 도립진자의 제어 및 실시간 해석 (The Control and the Real-time Analysis of a Horizontally Rotating Inverted Pendulum)

  • 김효중;김헌진;강철구
    • 한국정밀공학회:학술대회논문집
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    • 한국정밀공학회 1996년도 추계학술대회 논문집
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    • pp.341-345
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    • 1996
  • This paper presents the dynamics and the teal-time control of a horizontally rotating inverted pendulum. The dynamic equations representing three degrees of freedom rigid body motion of the pendulum are derived, and the state feedback controller is applied to the motion control of the pendulum. A 32 bit counter board with 16 bit hardware communication ability is developed to improve the real-time control performance and is applied to a horizontally rotating inverted pendulum. The simulation and experimental studies are conducted to evaluate the performance of the developed pendulum system and the timing in the real-time control is analyzed.

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빔형성방법을 이용한 회전하는 음원의 위치 판별에 관한 연구 (Localization of Rotating Sound Sources Using Beamforming Method)

  • 이재형;홍석호;최종수
    • 한국소음진동공학회논문집
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    • 제14권12호
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    • pp.1338-1346
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    • 2004
  • The positions of rotating sound sources have been localized by experiments with the Doppler effects removed. In order to de-Dopplerize the sound signals emitted from moving sources, two kinds of signal reconstruction methods were applied. One is the forward propagation method and the other is the backward propagation method. Forward propagation method analyze the source emission time based on the instantaneous distance between sensors and the assumed source position, then the signals are reconstructed with respect to the emission time. On the other hand, the backward method uses time delay to do-Dopplerize the acquired data for the received time of reference. In both techniques. the reconstructed signal data were processed using beamforming algorithm to produce power distributions at the frequencies of interest. Experiments have been carried out for varying frequencies, rotating speeds and the object distances. It is shown that the forward propagation method gives better performance in locating source position than the backward propagation method.