• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.6
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• pp.495-501
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• 2013

This paper deals with noise reduction on a light source driving board in a projector. We analyze causes of noise/vibration in the circuit with the present increasing use of LD and LED driving boards. The main source of noise is the MLCC in the driving board. Our aim is to investigate how the mechanical arrangement of the circuit elements affects noise reduction. The result of our experiment shows that noise can be reduced by symmetrical arrangement and slots in PCB. This result is expected to facilitate a variety of applications for manufactures without a need to change circuit elements.

• Journal of Korea Society of Industrial Information Systems
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• v.7 no.5
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• pp.190-194
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• 2002

The aim of development is system having convenient, cheap, reliable and better good measurements. The cozy environments in auto and architects is essentiable requirements. This study focuses on system developments of test equipment for better performance of noise protection in automobiles. Sound cards using makes easily to acquire the sound in each room, especially reduced the complexities of the circuits. The developed system have easily been measured and have characteristics of rapid mecanical response. The menu of rough scan method makes efficiently to test the shielding performance of auto rubber in whole frequency scales.

• Proceedings of the KIPE Conference
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• 2016.07a
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• pp.97-98
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• 2016

일반적으로 산업체에서 사용되는 전압형 PWM(Pulse Width Modulation) 인버터는 2개의 스위칭 소자가 직렬 연결된 단상하프 브릿지 회로를 기본 회로로 사용한다. 보통 극(pole), 암(arm) 또는 레그(leg)라 불리며 상보적으로 스위칭한다. 하지만 게이팅 신호 전달의 시지연과 스위치의 온-오프 시간차이에 의해 두 스위치가 동시에 켜지는 단락 사고를 방지하기 위해 데드 타임을 사용한다. 데드 타임은 직렬 연결된 두 스위치를 동시에 끔으로써 인버터의 안정적인 동작을 보장하지만 인버터 출력 전압 제어가 불가능하여 전압 및 전류 왜곡과 소음, 진동을 야기한다. 본 논문에서는 데드 타임 보상을 위한 적절한 전압 선정 방법에 대해 알아본다. 데드 타임 보상 전압 선정을 위해 부하 전류의 6고조파 성분을 추출, 비교하여 적절한 데드 타임 보상 전압을 선정하였으며 실험을 통해 그 유효성을 검증하였다.

• Electronics and Telecommunications Trends
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• v.29 no.6
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• pp.22-30
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• 2014

전기에너지를 기계에너지로 변환하는 기존의 브러시 있는 직류모터보다 고효율, 저소음, 제어용이성, 고내구성 특징을 가지는 브러시 없는 직류(BLDC: Brushless Direct Current)모터의 응용분야의 확대로 지속적으로 성장하는 BLDC 모터시장에 대응하기 위한 에너지 절감형 BLDC 모터구동시스템 기술개발이 절실히 요구되는 실정이다. 이에 따라, 본고에서는 일반차량 및 PHEV(Plug-in Hybrid Electric Vehicle)/EV(Electric Vehicle) 등 그린자동차용, 에어컨, 세탁기, 냉장고 등 그린백색 가전용, 산업용 건조기, ATM, 자판기 등 그린산업 기기용 BLDC 모터에 적용할 수 있는 에너지 절감기능이 우수한 BLDC 모터, BLDC 모터구동회로, 고전압 파워소자구동회로, 고전압 파워소자로 구성된 BLDC 모터구동시스템 기술동향에 대해 논의하고자 한다.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.13 no.8
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• pp.651-657
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• 2003

A new mechanical-electrical hybrid passive damping treatment is proposed to improve the performance of structural vibration control. The proposed hybrid passive damping system consists of a constrained layer damping treatment and a shunt circuit. In a passive mechanical constrained layer damping, a viscoelastic material damping layer is used to control the structural vibration modes in high frequency range. The passive electrical damping is designed for targeting the nitration amplitude in the low frequency range. The governing equations of motion are derived through the Hamilton's principle. The obtained mathematical model Is validated experimentally. The presented theoretical and experimental techniques provide invaluable tools for controlling the multiple modes of a vibrating structure over a wide frequency band.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.273-278
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• 2002

Booming sound is one of the most important interior sound of a passenger car. The conventional booming noise research was focused on the reduction of the A-weighted sound pressure level. However A-weighted sound pressure level can not give the whole story about the booming sound of a passenger car. In this paper, we employed sound metric which is the subjective parameter used in psycoacoustics. According to recent research results, the relation between sound metrics and subjective evaluation is very complex and has nonlinear characteristics. In order to estimate this nonlinear relationship, artificial neural network theory has been applied to derivation of sound quality index for booming sound of a passenger car.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.902-907
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• 2002

An equivalent electroacoustic circuit approach of estimating the sound absorption coefficient for parallel perforated plate system is proposed. The proposed approach is validated by comparing the calculated absorption coefficients of a parallel single layer perforated plate system with the values measured by the two-microphone impedance tube method for various porosity and the number of perforated plate. The sound absorbing performances of parallel and series perforated plate systems are compared and discussed from a standpoint of frequency bandwidth with sound absorption. The proposed approach is further extended to the parallel double layer perforated plate system.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.1000-1003
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• 2002

For high density optical storage, there should be a high NA objective lens and a shorter wavelength laser diode. To secure the disc tilt margin related to the coma aberration, moreover, it's difficult to apply the tilt compensation mechanism into the portable PC. In this paper, we proposed the 3-axis asymmetry pickup actuator with high efficiency symmetric magnetic circuit, which consisted of the top cover type inner yoke for high magnetic flux density, the coil stack unit for the 3-axis independent operation and vertically polarized magnets. This newly suggested actuator features DVD-RAM recording, we achieved the high focus & track AC sensitivity and the greatly stabilized system.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.04a
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• pp.374-378
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• 2014

The piezoelectric materials convert from mechanical energy to electrical energy. The piezoelectric materials are used in various engineering applications such as piezoelectric ultrasonic actuators. Since the piezoelectric coupling characteristics of the actuator systems should be considered at the initial design stage, it is essential to analyze the piezoelectric coupling characteristics of the ultrasonic actuators. In this study, we analyzed the electromechanical characteristics of piezoelectric stacked actuator using the equivalent circuit model with modal mass stiffness parameters. It was compared the admittance of piezoelectric stack actuators with the analytical circuit model and the finite element model. Also, the coupling coefficient of piezoelectric stack actuator was discussed according to the number of stacks of actuators.

• The KSFM Journal of Fluid Machinery
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• v.10 no.3 s.42
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• pp.33-38
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• 2007

Fan selection procedure and fan noise evaluation method are presented for the system electronic cooling by combining FNM(Flow Network Model) and fan noise correlation model. Internal flow paths and distribution in electronic system we analyzed by using the FNM with the flow resistances for flow elements of the system. Based on the fan operation point predicted from the FNM analysis results, the present fan noise model predicts overall sound power, pressure levels and spectrum. The predictions of the flow distribution, the fan operation and the noise level in electronic system by the present method are well agreed with 3-D CFD and actual test results.