• 한국가시화정보학회지
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• 제12권1호
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• pp.43-48
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• 2014

This paper describes the measurement of performance evaluation of rotational flow varying chamber size and Reynolds number. Through the experimental visualization of the flow rotation, the number and position of flow rotation in the $2{\times}2$ microfluidic centrifuge were examined. At a chamber width of 250${\mu}m$, single flow rotation was obtained over at a Reynolds number of 300, while at a chamber width of 500 ${\mu}m$, single flow rotation did not appear. For performance evaluation, the intensity in microchamber was measured during 20 sec. At a chamber width of 250 ${\mu}m$, performance of rotational flow increased as Reynolds number increased. However, the variation of intensity in microchamber remained unchanged at a chamber width of 500 ${\mu}m$. The numerical analysis showed that the threshold centrifugal acceleration to obtain rotational flow for ejected particles was 200g.

• 조명전기설비학회논문지
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• 제27권11호
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• pp.76-81
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• 2013

In this paper, a corona motor with blade type electrodes has been employed as a wind blower. The rotation speed was influenced significantly by the polarity of applied voltage and the number of blades. Therefore the effect of polarity of applied voltage and the number of blades on the electrical and mechanical fundamental properties of corona motor were investigated experimentally. The rotation speed decreased for increasing of number of blades, because the mass of blades increased. But the amount of air blow increased despite decreasing of the rotation speed, because air volume is not only influenced by rotation speed but also the number of blades and ionic wind which generated between blade tips and a induction electrode. Although space occupied by blades of the corona motor is smaller than the whole area of the blast pipe, wind rises a whole range of a wind blower for such reasons.

• 대한인간공학회지
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• 제32권5호
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• pp.429-435
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• 2013

Objective: This study aims to analyze job satisfaction and accident prevention according to job rotation system types in a motor company. Background: The study of a motor company's job rotation system has come to attention with enhancing productivity, preventing musculoskeletal disorders, and improving quality. Method: In this study, a survey was conducted to show job satisfaction rates according to job rotation systems. Also an investigation was done regarding industrial accidents and previous workers who are receiving treatment for musculoskeletal disorder over the last five years. Results: The job rotation system in this study has been carried out by voluntary decision of workers. Out of the job rotation types, the medium rotation complexity type had high job satisfaction whereas in a high or low rotation complexity type, which many workers prefer, led to less number of accidents and days of sick leave. Application: The results of this study are expected to be a fundamental data to job design.

• 한국통신학회논문지
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• 제29권7A호
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• pp.794-806
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• 2004

본 논문에서는 IEEE 802.11a의 OFDM 통신시스템에 대한 송수신 주파수편차의 교정기법을 연구하고 편차주파 수들의 교정오차에 의한 잡음을 분석한다. 반송주파수편차에 의한 심볼당 회전위상을 짧은 훈련신호(short preamble)의 자기상관에서 추정한다. 잡음의 영향을 줄이기 위하여 짧은 훈련신호(short preamble)를 과도표본화 (over-sampling)한다. 파일롯(pilot) 신호를 도입하여 추정된 반송주파수편차의 오차와 표본화 주파수편차에 의한 OFDM 심볼당 회전위상을 추정한다. 이러한 회전위상의 추정과 교정에 CORDIC(Coordinated Rotational Digital Computer) 프로세서 또는 각도와 복소수의 환산표를 사용하고 이것들의 구현기법과 장단점을 비교한다. 복소수와 위상은 CORDIC 프로세서와 환산표에서 한정된 비트(bit) 개수로 계산되므로 각도양자화 오차가 있게 된다. 비트개수에 따른 각도양자화 오차를 OFDM 신호의 SNR로 나타내고 IEEE 802.11a의 편차주파수 교정에서 요구되는 최소한의 비트 개수를 제시한다. 끝으로, 모의실험을 통하여 짧은 훈련신호로 반송주파수편차를 추정하고 CORDIC 프로세서와 환산표에서 사용된 비트 개수에 따른 양자화 잡음을 검증한다.

• Earthquakes and Structures
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• 제10권1호
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• pp.73-89
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• 2016

The seismic performance of moment frames could vary according to the rotation capacity of their connections. The minimum rotation capacity of moment connections for steel intermediate moment frames (IMF) was defined as 0.02 radian in AISC 341-10. This study evaluated the seismic performance of IMF frames with connections having a rotation capacity of 0.02 radian. For this purpose, thirty IMFs were designed according to current seismic design provisions considering different design parameters such as the number of stories, span length, and seismic design categories. The procedure specified in FEMA P695 was used for conducting seismic performance evaluation. It was observed that the rotation capacity of 0.02 radian could not guarantee the satisfactory seismic performance of IMFs. This study also conducted seismic performance evaluation for IMFs with connections having the rotation capacity of 3% and ductile connections for proposing the minimum rotation capacity of IMF connections.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 G
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• pp.2821-2823
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• 1999

In this paper we proposed an algorithm for rotation-invariant pattern recognition and rotated angle estimation between two patterns by employing selective template matching. Generally template matching has been used in determining the location of pattern but template matching requires a number of calculating correlation. To reduce the number of correlation we used steady-state genetic algorithm which is effective in optimization problem. We apply this method to distinguish specific pattern from similar coin patterns and estimate rotated angle between patterns. Our result leads us to the conclusion that proposed method performed faster than classical template matching

• 대한기계학회논문집B
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• 제27권7호
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• pp.948-955
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• 2003

Pressure coefficient in rotating discharge hole was measured to gain insight into the influence of rotation to the discharge characteristics of rotating discharge hole. Pressure measurements were done by the telemetry system that had been developed by the authors. The telemetry system measures static pressure using piezoresistive pressure sensors. Pressure coefficients in rotating discharge hole were measured in longitudinal direction and circumferential direction with various rotating speed and 3 pressure ratios. From the results, the pressure coefficient, and therefore the discharge coefficient, is known to decrease with the increase of Ro number owing to the increase of flow approaching angle to the discharge hole inlet. However, there exists critical Ro number where the decrease rate of discharge coefficient with the increase of Ro number changes abruptly; flow separation occurs from the discharge hole exit at this critical Ro number. Critical Ro number increases with the increase of length-to-diameter ratio, but the increase is small where the length-to-diameter ratio is higher than 3. The decrease rate of discharge coefficient with the increase of Ro number depends on the pressure recovery at the discharge hole, and the rate is different from each length-to-diameter ratio; it has tendency that the short discharge hole shows higher decrease rate of discharge coefficient.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2000년도 춘계학술대회논문집 - 한국공작기계학회
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• pp.109-114
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• 2000

A new method for the determination of camera system rotation and translation from in 3-D space using recursive least square method is presented in this paper. With this method, the calculation of the equation is found by a linear algorithm. Where the equation are either given or be obtained by solving five or more point correspondences. Good results can be obtained in the presence if more than the eight point. A main advantage of this new method is that it decouple rotation and translation, and then reduces computation. With respect to error in the solution point number in the input image data, adding one more feature correspondence to required minimum number improves the solution accuracy drastically. However, further increase in the number of feature correspondence improve the solution accuracy only slowly. The algorithm proposed by this paper is used to make camera system rotation and translation easy to recognize even when camera system attached at end effecter of six degrees of freedom industrial robot manipulator are applied industrial field.

• 한국유체기계학회 논문집
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• 제10권2호
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• pp.32-40
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• 2007

The present study investigated local pressure drop in a rotating smooth square duct with turning region. The duct has a hydraulic diameter $(D_h)$ of 26.7mm and a divider wall of 6.0mm or $0.225D_h$. The distance between the tip of the divider and the outer wall of the duct is $1.0D_h$. The Reynolds number (Re) based on the hydraulic diameter is kept constant at 10,000, and the rotation number (Ro) is varied from 0.0 to 0.20. The pressure coefficient distribution $(C_p)$, the friction factor (f) and the thermal performance $({\eta})$ are presented on the leading, the trailing and the outer surfaces. It is found that the curvature of the $180^{\circ}-turn$ produces Dean vortices that cause the high pressure drop in the turning region. The duct rotation results in the pressure coefficient discrepancy between the leading and trailing surfaces. That is, the high pressure values appear on the trailing surface in the first-pass and on the leading and side surfaces in the second-pass. As the rotation number increases, the pressure discrepancy enlarges. In the fuming region, a pair of the Dean vortices in the stationary case transform into one large asymmetric vortex cell, and then the pressure drop characteristics also change.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.2095-2100
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• 2003

This Experimental study concerns the characteristics of vortex flow in a concentric annulus with a diameter ration of 0.52, whose outer cylinder is stationary and inner one is rotating. Pressure losses and skin-friction coefficients have been measured for fully developed flow of bentonite-water solution(5%) when the inner cylinder rotates at the speed $0{\sim}400rpm$. The results of present study reveal the relation of the bulk flow Reynolds number Re and Rossby number $R_o$ With respect to the skin friction coefficients. The effect of rotation on the skin friction coefficient is significantly dependent on the flow regime. In all flow regime, the skin friction coefficient is increased by the inner cylinder rotation. The critical (bulk flow) Reynolds number $Re_c$ decreases as the rotational speed increases. Thus, the rotation of the inner cylinder promotes the onset of transition due to the excitation of Taylor vortices.