• ETRI Journal
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• 제32권6호
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• pp.921-931
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• 2010

It has been shown that the principal subspace-based multichannel Wiener filter (MWF) provides better performance than the conventional MWF for suppressing interference in the case of a single target source. It can efficiently estimate the target speech component in the principal subspace which estimates the acoustic transfer function up to a scaling factor. However, as the input signal-to-interference ratio (SIR) becomes lower, larger errors are incurred in the estimation of the acoustic transfer function by the principal subspace method, degrading the performance in interference suppression. In order to alleviate this problem, a principal subspace modification method was proposed in previous work. The principal subspace modification reduces the estimation error of the acoustic transfer function vector at low SIRs. In this work, a frequency-band dependent interpolation technique is further employed for the principal subspace modification. The speech recognition test is also conducted using the Sphinx-4 system and demonstrates the practical usefulness of the proposed method as a front processing for the speech recognizer in a distant-talking and interferer-present environment.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.2246-2251
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• 2003

This paper proposes shape design of frame structures for vibration suppression and weight reduction. The $H_{\infty}$ norm of the transfer function from disturbance sources to the output points where vibration should be suppressed, is adopted as the performance index to represent the magnitude of vibration transfer. The design parameters are the node positions of the frame structure, on which constraints are imposed so that the structure achieves given tasks. For computation of Pareto optimal solutions to the two-objective design problem, a number of linear combinations of the $H_{\infty}$ norm and the total weight of the structure are considered and minimized. For minimization of the scalared objective function, a Lagrange function is defined by the objective function and the imposed constraints on the design parameters. The solution for which the Lagrange function satisfies the Karush-Kuhn-Tucker condition, is searched by the sequential quadratic programming (SQP) method. Numerical examples are presented to demonstrate the effectiveness of the proposed design method.

• International Journal of Control, Automation, and Systems
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• 제5권6호
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• pp.614-620
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• 2007

This paper considers vibration suppression of a mechanical transfer system, where the work is connected with the hand flexibly. We adopt the idea of jerk reduction of the hand. From the equation of motion, we first derive a state equation including the jerk and acceleration of the hand, but excluding the displacement and velocity of the work. Then, we design optimal state feedback for a suitable cost function, and show by simulation that jerk reduction of the hand is effective for vibration suppression of the work and improvement of the settling time. Since state feedback including the jerk and acceleration is not practical, we propose a computation method for optimal feedback using displacements and velocities in the state only.

• 기본간호학회지
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• 제18권2호
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• pp.258-266
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• 2011

Purpose: The purpose of this study was to examine the relationships among negative emotion, emotion suppression, job satisfaction and organizational commitment in Hospital Nurses. Method: The participants were 155 registered nurses working in 1 hospital in Seoul. Data were obtained by self-report questionnaires. Data were collected from October 1 through October 9, 2010. Data were analyzed using frequency and percentage, t-test, ANOVA and Scheffe's test and stepwise multiple regression. Result: The influencing factors for organizational commitment of hospital nurses were job satisfaction, position, total clinical career, and negative emotion. These variables explained 56.6% of the variance of the organizational commitment. Conclusion: These results indicate that improving job satisfaction is the best way to enhance nurses' organizational commitment and thus, a need to improve the job satisfaction of hospital nurses.

• 전자공학회논문지
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• 제51권1호
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• pp.42-46
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• 2014

고조파를 제거하는 기능을 갖는 윌킨슨 전력분배기를 나타내었다. 종래의 윌킨슨 전력분배기에서 선로 변환기의 양단에 제거할 고조파의 수만큼의 전송선로를 추가한 후에 새로운 윌킨슨 전력분배기의 해를 구할 수 있다. 실험적인 결과는 기본 주파수에서는 종래의 기능을 유지하면서 2차 및 3차 고조파를 -45.3 dB 및 -37 dB의 억압비를 나타내었다.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제52권5호
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• pp.238-245
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• 2003

In this paper, a single Phase voltage source voltage-controlled active power filter(APF) for power quality improvement was proposed. The proposed APF has the performance of harmonic suppression and unity power factor correction. The performance of harmonic suppression can be obtained by controlling the waveshape of the APF output voltage to be sine wave. And, unity power factor is controlled by the reactive power control loop of the APF output. Simulation and experimental results using diode rectifier showed that the voltage-controlled APF, unlike the current-controlled APF, can reduce the voltage harmonics as well as current harmonics. Also the results showed that the input dover factor and power quality were greatly improved.

• 한국전자파학회:학술대회논문집
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• 한국전자파학회 2005년도 종합학술발표회 논문집 Vol.15 No.1
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• pp.197-202
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• 2005

In this paper, we analyzed the signal distortion incorporating meander-shaped transmission line on PCB in broadband frequency range, up to 50GHz. This broadband characteristic provides reasonable analysis of digital pulse having very short rising time. Simulation results reveal suppression characteristic at multiband which is dependent on only the width of meander arm. This width of arm also can be adjusted using different permittivity because it provides different effective wave-length. It is found that the suppression characteristic shows sharpness with as a function of the number of arms. However, these characteristics shown limitation for microstrip line structure rather than for stripline structure, so we can avoid these unwanted phenomena using stripline structure.

• 소음진동
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• 제10권2호
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• pp.280-290
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• 2000

The paper deals with vibration suppression and dynamic stability of a vertical cantilevered pipe conveying an internal flowing fluid and having an attached mass. Real pipe systems may have some valves or mechanical attached parts, which can be regarded as attached lumped masses. The effect of attached mass on the dynamic stability of a cantilevered pipe conveying fluid is investigated for different locations and magnitudes of the attached mass. The flow rate was controlled through motor pump output and measured by a flow meter. Experimental resutls in the vicinity of flutter fluid velocity were compared with theoretical predictions. It has been found that the experimental results are in substantial agreement with the theoretical predictions. Finally, in order to suppress the vibration of the pipe subjected to a disturbance, and control technique using an internal flowing fluid is introduced.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2004년도 추계학술대회 논문집
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• pp.151-157
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• 2004

In this paper, we propose a simple control scheme, based on second order sliding modes, which guarantees a fast and precise container transfer and the swing suppression during the container movement, despite of model uncertainties and unmodeled dynamic actuators. In the actual case, the swing suppression is obtained by constraining the system motion on a suitable surface which involves both the desired path and the swing angle. Strictly speaking, the trolley velocity is modified on-line, on the actual swing angle, to obtain the suppression of the oscillations not only at the end of the transport but during transfer as well. Such controller has been tested on a laboratory-size model of the 3Dcrane, and some experimental results are reported.

• 한국안전학회지
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• 제18권1호
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• pp.28-32
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• 2003

The present study investigates the spray characteristics of water mist nozzle with mid-low pressure for fire suppression. The examined nozzle types are swirl and spiral nozzle. The result shows that K factor of water mist nozzle is much smaller than those of general sprinkler. Spray angle of spiral nozzle is largest and more than $150^{\circ}$. SMD(Sauter Mean Diameter) of water mist nozzles is ranged between 100 and 200$\mu\textrm{m}$through measuring by image processing method. The spray pattern of spiral nozzle represent that water flux of first stream is 2 times larger than that of second stream. This study will contribute better understandings of the water-mist spray characteristics and useful daia for developing the water-mist nozzles.