• Journal of KSNVE
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• v.10 no.6
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• pp.971-976
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• 2000

High level random vibration environments induced while launching of spacecraft can damage sensitive electronic equipment, unless the equipment is properly packaged. Thus careful consideration on the launch environment, especially for high level random vibration, is required in the design stage of electronic equipment of spacecraft. This paper describes the development process of Solar Array Regulator for KOMPAT-2, which is designed and tested by Korean engineers. Both analytical and experimental techniques are introduced in this paper.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2013.04a
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• pp.135-140
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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.

• Explosives and Blasting
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• v.18 no.2
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• pp.14-22
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• 2000

The estimation of proper prediction method and the alteration of transformation method of environmental regulation standard were carried out by measuring blasting noise in construction field. The correlation of scaled distance with sound pressure level were better than with sound level, but it was proved to be difficult to control blasting noise because the correlation factor was too 1ow. three methods to transform sound pressure levee to sound level were examined. The method is the transformation by correlation equation of sound pressure level and sound level which are measured at the same time, and simplified transformation of A-weighting network corresponding to dominant frequency, and the transformation of sound pressure level by FFT. There were many errors to transform. The best effective method is the transformation using correlation equation of sound pressure level and sound level which are measured at the same time.

• Journal of IKEEE
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• v.5 no.1 s.8
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• pp.16-23
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• 2001

Passive noise reduction is a classical approach to attenuate industrial noise, and an active noise cancellation has several advantages over the passive noise cancellation. The active noise reduction system offers a better low frequency performance with a smaller and lighter system. This paper presents a simple active closed loop control system which consists of an controller for inverting and compensating the phase delay, a microphone for picking up the external noise, and a loudspeaker for radiating the acoustic out of phase signal to reduce the external noise, and external noise can be reduced after compensating the phase difference to be $180^{\circ}$ in the frequency of maximum value in the amplitude response. The noise of the phase delay covered from $50^{\circ}\;to\;310^{\circ}$ tends to be reduced in the active noise control system and it is possible to obtain a noise cancelling of up to approximately 20[dB] at the ears in the enclosurer.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.48-53
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• 2014

Rocket, held using the CCA for the mission, a plurality of recording devices, and navigation equipment. In case of a projectile which is entered the water after fired into the air, after performing stages and fairing separated in flight to enter the underwater. It is caused by the explosion of gunpowder mainly, vibration phenomenon of a large transition is induced structurally very, also on entering the water, have a significant shock structurally separated. If shock is transmitted directly to the CCA through the body, it can be caused malfunction of payloads, resulting in failure of the mission of the projectile. In order to ensure the stability against shock, in this paper, Calculating a target resonacne frequency of the CCA, and verified through modal test and analysis. Maximum acceleration position of CCA is checked by SRS analysis. In addition, effectiveness of shock isolation system through shock analysis.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.4
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• pp.397-404
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• 2010

The use of equivalent circuit models of piezoelectric energy harvesters is inevitable when power circuitry including rectifying and smoothing circuit elements is connected to them for evaluating DC electrical outputs. This is because it is difficult to incorporate the electro-mechanical coupling resulting from the additional circuitry into the conventional finite element analysis. Motivated by this observation, we propose a method to accurately extract the equivalent circuit parameters by using commercially available FEM software such as ANSYS which provides three-dimensional AC piezoelectric analysis. Then the equivalent circuit can be analyzed by circuit simulators such as $SimPowerSystems^{TM}$ of MATLAB. While the previous works have estimated the circuit parameters by experimental measurements or by analytical solutions developed only for limited geometries and boundary conditions, the proposed method has no such limitation because piezoelectric energy harvesters of any shapes and boundary conditions can be treated in FEM software. For the verification of the proposed method, multi-modal AC electrical power output by using a corresponding equivalent circuit is compared with that by ANSYS. The proposed method is then shown to be very useful in the subsequent evaluation of DC electrical output which is obtained by attaching a bridge diode and a storage capacitor to a piezoelectric energy harvester.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.10a
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• pp.144-148
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• 2001

자동차의 발전과 함께 유지 보수를 위한 사용자의 요구는 급증하고 있으나 정비사의 부족으로 인해 경제성 및 신속성 등 이 문제가 되고 있고 이를 해결하기 위해 현재 개발되고 있는 장치들은 대부분 전자 제어 유닛에서 발생시키는 신호를 분석하거나 운전자와의 대화를 통하여 진단하는 방식으로 고장으로 인한 소음이나 진동등 운전자들의 주관적인 평가대상에 대해서는 적절한 해결책으로 제시해 주지 못하고 있다. 그러므로 계측에 의한 소음과 진동 데이터를 이용하여 전문가의 판단을 가지고 고장의 원인을 규명하며 운전자를 위한 오디오적인 표현을 해 줄 수 있는 진단 전문가 시스템이 필요하게 되었다. 본 논문에서는 자동차의 여러 단품중 쇼크 옵서버와 에어컨에 대하여 소음 진동 현상의 정상 및 이상 증상과 신호 계측 방법을 연구하였고 계측된 신호에 대해 패턴 화하여 인공 신경 회로망과 퍼지 추론을 통한 진단을 할 수 있는 알고리즘을 개발하였으며 차후 계속되는 연구에 사용될 정상 및 이상신호에 대한 기본적인 데이터 베이스를 구축하였다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.11a
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• pp.624-629
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• 2003

In this paper, broadband shunt technique for increasing transmission loss is experimentally investigated. Piezoelectric shunt damping is studied using resonant shunt circuit and negative capacitor shunt circuit. A resonant shunt circuit is implemented by using a resistor and inductor. Negative Capacitor shunt damping is similar in nature to resonant shunt damping techniques, as a single piezoelectric material is used to dampen multi-mode. Performance of both methods is experimentally studied for noise reduction. This is based upon SAE J1400 test method and a transmission loss measurement system is provided for it. This paper will present the test setup fer transmission loss measurement and the tuning procedure of shunt circuits. Finally the results of sound transmission tests will be shown.

• Proceedings of the KIEE Conference
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• 1999.07g
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• pp.3227-3229
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• 1999

수신된 초음파 파형이 표준 파형과 정합되는 시간을 수신 시점으로 사용함으로써 정확한 거리측정을 가능하게 하는 초음파 센서 거리계의 성능 개선을 제안하였다. 근거리 측정용으로 많이 사용되는 초음파센서는 다른 거리측정 시스템에 비해 하드웨어 구현이 용이하고 가격이 저렴한 장점이 있으나 센서 수신부측 Limit 회로의 threshold level의 선택 문제에 따른 거리 측정의 오차와 소음에 의한 거리 측정 오차가 매우 큰 문제가 되고 있다. 본 논문에서는 수신된 초음파 파형에 표준 파형을 정합하여 최대의 정합값을 가지는 시점을 수신 시간으로 간주하여, 소음환경비서도 거리 측정이 가능한 파형 정합 방법을 제한하였다. 본 논문의 실험을 통하여, 잡음이 심한 소음환경에서도 제안한 파형 정합 방법이 Threshold 방법 보다 초음파센서 거리 측정 성능이 개선됨을 확인할 수 있었다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.5
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• pp.87-92
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• 2019

This study is the analysis of causes of printed circuit board (PCB) in collective protection equipment failure and quality improvement. The equipment is a component of the weapon system currently in operation and serves to defend against enemy chemical and biological attack as well as heating and cooling functions. However, during operation in the military, fans of condensate assembly failed to operate. The cause of the failure is the burning of PCB. It was found that the parts were heated according to the continuous cooling operation under the high temperature environmental conditions. Accordingly, the electronic components exposed to high temperature were deteriorated and destroyed. To solve this problem, PCB apply to heatsink. The performance test of improved PCB has been completed. Futhermore system compatibility, positive pressure maintenance and noise test were performed. This improvement confirmed that no faults have occurred in PCB so far. Therefore, the quality of the equipment has improved.