• 한국소음진동공학회논문집
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• 제20권2호
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• pp.153-159
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• 2010

This work focuses on finding a method to reduce the noise of a hermetic reciprocating compressor during start-up using an acoustical analysis. The noise of compressor during start-up, which is a higher level than that of a normal operating condition, has transient and non-stationary characteristics. The acoustical analysis of compressor cavity is performed to find an effective method to reduce the noise level. In the acoustical analysis, the shape variations of frequency response function in the neighborhood of resonances are tested for three parameters: the height of remained oil, the suction position of refrigerant and the position of driving part. As a conclusion of this result, to reduce the emission noise of compressor during start-up, the height of remained oil should be kept at 16 mm, the refrigerant should be sucked at the cross point of nodal lines of X and Y directional cavity modes, and the driving part should be positioned in the center of cavity.

• KIEAE Journal
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• 제9권1호
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• pp.55-60
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• 2009

This study was carried out to propose the optimum technologies that can be applicable to noise and fugitive dust controlling in construction sites by comparative analysis in cases. The ninety three environmental management technologies applied to fifty-five construction projects conducted during 2005~2007 in Korea were analyzed by checklist method. The construction companies paid more attention to the noise and fugitive dust controlling technologies than the waste and wastewater. The diverse pollution controlling techniques were applied to the architectural projects than the civil projects to meet the environmental requirements in residential area. The fugitive dust controlling technologies(75.3%) were more widely applied to all construction projects than the noise controlling technologies(24.7%). As the noise controlling techniques, the noise barriers in wall-form which are set up as boundary in construction site were more widely used than the noise barriers in curtain-form, in cabin and silencers. Water spraying systems, wind barriers and mechanical sweepers were the preferred technologies for controlling fugitive dust emission.

• Journal of Power Electronics
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• 제19권1호
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• pp.278-287
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• 2019

In this study, a zero-crossing spike current issue in a totem-pole bridgeless power factor correction (PFC) converter is comprehensively investigated for the first time. Spike current occurs when input voltage crosses zero, becomes a noise source, and causes severe common mode emission issues. A generation mechanism for electromagnetic interference (EMI) is presented to investigate the EMI problem caused by zero-crossing issue, and a noise spectrum due to this issue is predicted by a theoretical analysis based on the Fourier coefficient of an approximate spike current waveform. Furthermore, a noise reduction method is proposed and then improved to reduce the spike current. Experimental measurements are implemented on a GaN-based totem-pole bridgeless PFC converter, and the spike current can be effectively suppressed through the proposed method. Furthermore, the noise spectrums measured without and with the reduced zero-crossing spike current are compared. Experimental results validate the analysis of the noise spectrum caused by the zero-crossing spike current issue.

• 한국소음진동공학회논문집
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• 제14권4호
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• pp.276-286
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• 2004

현재. 미 연방도로부에서는 도로교통소음분석을 위한 예측모형 (TNM ＆ STAMINA)을 미 전 지역에 제공하고 있고, 이와 관련된 여러가지 연구논문들이 수행되고 있는바, 모델을 이용한 예측치와 실측치 간의 비교$.$분석 연구논문을 통하여 차이점이 존재하는 것을 증명하고 있다. 따라서 본 연구논문은 소음예측모형의 핵심자료로 사용될 수 있는 루이빌대(UofL) 회귀모형들을 차종별 (소형, 중형, 대형) 그리고 주별 (아리조나. 콜로라도, 조지아, 캔사스, 와싱톤)로 구분하여 그 차이점을 통계적으로 비교$.$분석$.$결론을 도출하였다. 그 결과 아리조나와 콜로라도(중대형)를 제외한 나머지 개별 State-specific데이터는 통계적으로 서로 다른 것으로 나타났다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 F
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• pp.2106-2107
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• 1998

This paper analyzes the sources of EMI noise, and Presents the noise reduction method using the modulation of switching frequency. Modulating the switching frequency makes the noise of side bands by shattering emission spectrum, and then can reduce the size of EMI filter at input line of power supply.

• 한국전기전자재료학회논문지
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• 제22권3호
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• pp.239-247
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• 2009

In AC-PDP, it is necessary to achieve high luminance efficacy, high luminance and high resolution by adopting technologies such as high Xenon concentration, MgO doping, and long gap. However, it is very difficult to apply above technologies because they reduce driving voltage margin. For example, doping of MgO reduces driving voltage but introduces new problems such as increased temperature dependency of discharge, which result in larger variations in driving margin at different temperatures. In this paper, we present the experimental results of the characteristics of temperature-dependent discharges. In addition, we suggest the mechanism of bright noise, black noise, and high temperature mis-discharge, which depend on temperature-dependent characteristics of MgO.

• 전자공학회논문지A
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• 제31A권6호
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• pp.70-77
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• 1994

A low noise erbium doped fiber amplifier for optical preamplification has been demonstrated. The amplifier incoporates an optical isolator in its midway to prevent decrease of population inversion at the input port due to backward traveling amplified spontaneous emission. Then, high gain and low noise can be achieved simultaneously. A small signal gain of 34dB and a noise figure of 5.5dB have been achieved. With this amplifier, we obtained a receiver sensitivity of -39.7dBm with back to back configuration and -39.3dBm with 47km normal fiber for 10$^{-9}$BER at 2.5Gbps direct modulated optical signal.

• 전력전자학회논문지
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• 제22권5호
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• pp.382-389
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• 2017

The development of electronic technology has been rapidly achieved in the automotive industry. A trend that attaches electric equipment, including ECUs at vehicles, is observed. However, decrepit vehicles have several electrical noises and errors. The effect of electric noise on vehicles that are focused on smoke was investigated. Many researchers have argued that one of the reasons of the occurrence of smoke in vehicles is the inexact time of the occurrence of ignition. Moreover, various physical, chemical, and thermodynamic solutions were attempted to approach and many improvements were accomplished. However, in this study, the reduction of electrical and electronic noise is confirmed to improve the accuracy of the injection time on decrepit vehicles with electrical and electric technologies. Previous studies suggest that the distance between the pilot and main ignitions affect the occurrence of smoke and control the variance value of the distance between pilot and main ignitions with electric filter. Thus, the effect of reducing smoke occurred.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2002년도 동계연구발표회 논문개요집
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• pp.200-201
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• 2002

Recently, a countermeasure for the electromagnetic noise emission on RF integrated transmission line using the loss generation of ferromagnetic thin films is briefly suggested$\^$1,2/. Without the magnetic film, the noise harmonics of the signal pass through the transmission line with only a little attenuation. The ideal role of magnetic film is not to raise insertion losses in the pass-band and to give as large attenuation as possible to eliminate the noise harmonics at the stop-band, the frequency range higher than the meaningful signal as shown in Fig. 1. and Fig. 2. (omitted)

• ETRI Journal
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• 제38권1호
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• pp.1-8
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• 2016

A large incoherent crosstalk (IC) caused by amplified spontaneous emission (ASE) noise power from Tx-disabled optical network units and a differential path loss has been shown to degrade upstream transmission performance in time-division multiplexing passive optical networks. This paper considers the IC-induced power penalty of an upstream signal both in an XG-PON and in a TWDM-PON. We investigate the degradation of the extinction ratio and relative intensity noise through a simulation and experiments. For the XG-PON case, we observe a 9.6 dB difference in the level of ASE noise power from Tx-disabled ONUs (hereafter known simply as ASE noise) between our result and the ITU-T XG-PON PMD recommendation. We propose an optical filtering method to mitigate an IC-induced power penalty. In the TWDM-PON case, the IC-induced power penalty is naturally negligible because the ASE noise is filtered by a wavelength multiplexer at the optical line terminal. The results provide design guidelines for the level of ASE noise in both XG-PONs and TWDM-PONs.