• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.559-564
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• 2002

Cross-talk cancellation, inverse filter design or deconvolution in a generic term, is a vital process for a virtual sound realization in the stereo sound reproduction system. Most, if not all, of the design algorithms available for the inverse filter are based on a linearized model of the real physical plant. The result of such a plant-based design method, which may be referred to here as the indirect method, is biased due to both modelling and inversion errors. This paper presents a novel direct cross-talk cancellation method that may be free from the inversion error. The direct method can directly models the inverse filter by a suitable rearrangement of the input and output ports of the original plant so that no inversion is required here. Advantages are discussed with various experiments in an anechoic chamber using a PC soundcard. Binaural reproduction tests conducted showed that the conventional indirect method yields about 8 % reproduction performance error on both ear positions, whereas the direct method offers about 3 %.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.1212-1217
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• 2006

This study is concerned with static and sinusoidal disturbance rejection for a single periodic input disturbance with known period. In the area of active elimination of a disturbance force, the control input should have two different kinds of gains: one is to deliver a stable control and the other is a force component to cancel the external disturbance force. In this paper we employ a simple state feedback control law to make the balance beam stable and employ a linear observer to estimate the states which represent the external disturbance force components. Simulation results verify our proposed control method to reject a static and sinusoidal disturbance force.

• Journal of the Korean Society for Precision Engineering
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• v.11 no.2
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• pp.120-133
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• 1994

홀로그래픽 간섭계측기로터 나오는 영상 데이터를 해석하는 전문가시스템에 대하여 기술하였다. 그동안 간섭 띠무늬(fringe)를 해석하는 방법들이 어느 정도의 자동화를 이룩하며 개발되어왔다. 그러나, 복잡한 간섭 띠무늬 패턴(fringe pattern)및 심한 잡음이 생기게 되는 고속도 항공공학 분야 또는 실험기계공학 분야에서는 신뢰할 만한 자동화를 이룩하기가 매우 힘들었다. 현재 사용가능한 방법중에는 간섭띠무늬 추적, 위상전이, 푸리에 변환, 회귀분석 등이 있는데, 이들은 소음제거나 데이터 수정을 하는데 있어서 극히 국부적인 정보에만 의존하였다. 결과적으로, 특별히 심한 소음이 있는 경우, 부정확한 위상중첩이나 간섭띠무늬 순차배열문제에 부딪히게 되고 따라서 작업자의 수작업이 심각하게 필요하게 된다. 본 논문에서는 간섭띠무늬 추적방법의 자동화 를 위한 새롭고 포괄적인, 규칙기반 전문가시스템에 대하여 기술하였다. 새로 개발된 전문가 시스템은 간섭띠무늬 패턴에 대한 전체적인 또는 지연적인 정보를 추출해 내고 또 전문가가 가지고 있는 지식을 이용한다. 이 전문가 시스템은 저수준 및 고수준 처리를 동시에 할 수 있도록 상호연결기구를 채택하여 간섭띠무늬를 해석하는 적절한 해결책을 마련하였다. 또한 위상전이나 푸리에 변환 방법에서 문제가 되는 자동위상 중첩에 대해 개발된 전문가 시스템의 응용의 가능성에 대해서도 기술하였다.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.14 no.7
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• pp.586-603
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• 2004

One of the subtle problems that make noise control difficult for engineers is “the invisibility of noise or sound.” The visual image of noise often helps to determine an appropriate means for noise control. There have been many attempts to fulfill this rather challenging objective. Theoretical or numerical means to visualize the sound field have been attempted and as a result, a great deal of progress has been accomplished, for example in the field of visualization of turbulent noise. However, most of the numerical methods are not quite ready to be applied practically to noise control issues. In the meantime, fast progress has made it possible instrumentally by using multiple microphones and fast signal processing systems, although these systems are not perfect but are useful. The state of the art system is recently available but still has many problematic issues : for example, how we can implement the visualized noise field. The constructed noise or sound picture always consists of bias and random errors, and consequently it is often difficult to determine the origin of the noise and the spatial shape of noise, as highlighted in the title. The first part of this paper introduces a brief history, which is associated with “sound visualization,” from Leonardo da Vinci's famous drawing on vortex street (Fig. 1) to modern acoustic holography and what has been accomplished by a line or surface array. The second part introduces the difficulties and the recent studies. These include de-Dopplerization and do-reverberation methods. The former is essential for visualizing a moving noise source, such as cars or trains. The latter relates to what produces noise in a room or closed space. Another mar issue associated this sound/noise visualization is whether or not Ivecan distinguish mutual dependence of noise in space : for example, we are asked to answer the question, “Can we see two birds singing or one bird with two beaks?"

• International Journal of Highway Engineering
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• v.12 no.1
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• pp.87-98
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• 2010

Surface of fine-size exposed aggregate Portland cement concrete pavements is consists of exposed coarse aggregate by removing upper 2~3mm mortar of concrete slab. Fine-size exposed aggregate PCC pavements have advantages of maintaining low-noise and adequate skid-resistance level during the performance period. In order to provide the successful exposed concrete aggregate pavement, uniform distribution of the coarse aggregate on pavement surface through adequate the mix design and exposing method. In this study, evaluated initial performance of fine-size exposed aggregate PCC pavement by experimental construction. And it was known that fine-size exposed aggregate concrete pavement which can reduce the noise and maintain the adequate level of skid resistance and strength.

• The Journal of the Korea institute of electronic communication sciences
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• v.18 no.5
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• pp.859-866
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• 2023

This paper focuses on configuring a user-friendly system of LED systems by applying improvement measures such as gamma correction, non-flicker, and driving noise removal using MCUs and LED drivers. As a result of the experiment, the 22kHz PWM mode of the LED driver generated noise outside the audible frequency range, making it practically imperceptible to users. The appropriate pull-up resistor values within the normal operating delay ratio of 5% were found to be 1kΩ to 10kΩ for the 3kHz PWM mode and 1kΩ to 2kΩ for the 22kHz PWM mode. In addition, gamma correction can be optimized for nonlinear human visual systems to express accurate contrast and as a result, it is expected to develop an LED system that can be expressed more naturally and accurately than conventional LED systems and improve users' visual experience.

• Proceedings of the Korea Water Resources Association Conference
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• 2009.05a
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• pp.282-286
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• 2009

1979년 준공된 수도권 광역상수도 1단계 시설은 상당한 노후화가 진행되었을 것으로 예상되며, 또한 향후 한강하류권 용수공급계획이 예정되어 있어 내부부식 및 관로손상부 개량의 시급성이 제기되었다. 이에 따라 직경 2,800${\sim}$800mm의 초대구경 도수관 53.9km의 개량을 위한 사업이 추진되었으며 시공성, 환경성, 경제성 등의 여러 항목에 대한 검토 결과 신개념 녹색공법인 비굴착식 건식일체형 공법이 최종 선정되었다. 그동안 기존관 개량공사에서 주로 사용되었던 굴착공법이 굴착에 따른 공기지연, 소음 분진 악취 등의 환경오염, 전구간 굴착에 따른 공사비 증가 등 많은 문제점을 안고 있는 것에 반해, 동사업에서 채택된 비굴착공법은 관로내에서 작업이 이루어지므로 공기단축, 환경오염 최소화에 따른 민원발생 최소화, 작업구만 굴착함에서 오는 공사비 절감 등 상대적으로 훨씬 우수한 것으로 평가된다. 동공법에 따르면 관내부 갱생공사는 '배수 및 잔류토사 제거'${\to}$'관내건조'${\to}$'표면처리'${\to}$'프라이머도장'${\to}$'본도장'의 순으로 진행된다. 일체형 장비에 의한 이와 같은 초대형관의 자동화시공은 세계에서 처음 적용되는 것이다.

• The Journal of the Acoustical Society of Korea
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• v.15 no.4
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• pp.105-112
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• 1996

A linear acoustic analysis for baffled rocket combustion chambers has been developed. This study provides the comprehensive theoretical background for the baffle as one of the stabilizing devices in a liquid rocket propulsion system. Several specific effects of baffles are presented as mechanisms by which baffles eliminate instability. Included are longitudinalization of transverse waves inside baffle compartments, severe restriction of velocity fluctuations near the injector face, and decreased normal mode frequency of the chamber.

• Journal of the Korean Society for Railway
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• v.11 no.4
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• pp.398-403
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• 2008

The propulsion for locomotive application has changed from the DC motor system to the induction motor system. Although the induction motor system has almost reached the stage of maturity, this system also needs to be changed to the PM motor system for the direct drive without using reduction gear. Thus, the IPMSM (Interior buried Permanent Magnet Synchronous Motor) has been adopted to meet the locomotive driving specification. Where the wheel is directly dirven by the traction motor. In this paper, the investigation on IPMSM satisfying driving specifications for the direct drive has been performed using the advanced FEM.

• Geophysics and Geophysical Exploration
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• v.23 no.3
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• pp.117-130
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• 2020

Noises can distort acquired geophysical data, leading to their misinterpretation. Potential noises sources include anthropogenic activity, natural phenomena, and instrument noises. Conventional denoising methods such as wavelet transform and filtering techniques, are based on subjective human investigation, which is computationally inefficient and time-consuming. Recently, many researchers attempted to implement neural networks to efficiently remove noise from geophysical data. This study aims to review and analyze different types of neural networks, such as artificial neural networks, convolutional neural networks, autoencoders, residual networks, and wavelet neural networks, which are implemented to remove different types of noises including seismic, transient electromagnetic, ground-penetrating radar, and magnetotelluric surveys. The review analyzes and summarizes the key challenges in the removal of noise from geophysical data using neural network, while proposes and explains solutions to the challenges. The analysis support that the advancement in neural networks can be powerful denoising tools for geophysical data.