• 한국철도학회논문집
• /
• 제12권5호
• /
• pp.806-810
• /
• 2009

병원, 호텔 및 철도역사 등과 같은 대형의 건물 및 차량내부에 사용되는 공조 시스템은 일반적으로 높은 소음을 발생시킨다. 이러한 공조용 발생소음을 저감시키기 위해서 흡음재가 부착된 쳄버를 공기 시스템에 설치한다. 그러나 이러한 쳄버에 설치된 흡음재는 유리섬유 혹은 폴리우레탄 폼이 많이 사용되기 때문에 최근에는 환경적 문제를 야기한다. 이러한 문제를 해결하기 위해서 환경친화적인 다공판 시스템이 내장된 소음쳄버를 개발하였다. 이 소음쳄버는 기존의 소음쳄버에 비해서 중고주파수 영역에서 통일한 소음저감 성능을 나타내지만, 200Hz~400Hz 영역에서는 최고 8dB(A)까지 소음저감 효과가 있다.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
• /
• 제49권1호
• /
• pp.1-8
• /
• 2000

Switched reluctance motor(SRM) has simple magnetic structure, and requires simple power electronic driving circuit. It is very useful for wide range adjustable speed drive system. But, SRM drive generates large vibration and acoustic noise because it is commutated individually by step pulse m.m.f of each phase pole. In the vibration and acoustic noise characteristics. The considerable vibration and noise is induced by radial deforming of stator, so the frequency of dominant vibration and noise is coincident with the frequency of natural mode frequency of mechanical structure. This radial vibration force is generated in the phase commutation region. This paper suggests the new electromagnetic structure of SRM with auxiliary commutation winding which is excited by direct current. This phase and commutation winding are coupled magnetically between one phase winding and the other. Therefore, the switch-off phase current is absorbed by the another phase winding. By this interaction of phase and commutation winding in commutation mechanism, vibration and noise is reduced. And this reduction effect is examined by the test of prototype machine. As a result, SRM with DC exciting commutation winding is very useful to reduce vibration and acoustic noise.

• 한국정보통신학회:학술대회논문집
• /
• 한국해양정보통신학회 2004년도 춘계종합학술대회
• /
• pp.682-684
• /
• 2004

Random Telegraph Signal(RTS)에 의한 1/f 잡음이 CMOS Ring Oscillator의 Phase Noise와 Jitter에 미치는 영향을 조사한다. 7단 Ring Oscillator의 각 노드에 병렬 연결된 10개의 Piece-Wise-Linear 전류원이 RTS 신호를 모델링 한다. RTS 전류원의 진폭과 Time Constant를 변화시키면서 Ring Oscillator 출력의 FFT 및 전력 스팩트럼 밀도, Jitter를 관찰한다. RTS 전류원의 진폭은 Phase Noise의 폭을 증가시키고 결과적으로 Jitter의 크기도 증가 시키는 것이 확인 되었다. 그리고 RTS Time Constant가 짧아질수록 출력 신호의 FFT peak의 폭이 커지고 Cycle to Cycle Jitter 값이 증가하였다.

• 지역사회간호학회지
• /
• 제16권1호
• /
• pp.59-67
• /
• 2005

This study was to investigate knowledge, attitude and the preventive behaviour of noise of workers exposed to harmful noise and to provide primary data for noise-exposed workers' hearing conservation and the prevention of noise induced hearing loss. Method: The subjects were 104 workers who participated voluntarily in the questionnaire. The instrument used in this study was knowledge, attitude and practice on noise-induced hearing loss tool by Rhee & Yi (1996). The data were collected from August to September, 2002 with a self-administered questionnaire. Data were analyzed by SPSS 10.0 win program for finding frequency, percentage, mean, standard deviation, t-test, and ANOVA. Results: The average age of workers was 35.9 and the current average year of working at the noise place was $5{\sim}$10 years. In the group of previous noise-exposed workers, they showed significant difference in preventive behaviors (t=4.087, p=.048). In the group of current noise-exposed workers, they showed significant difference in recognition and attitude of noise(F=4.707, p=.004). Also, the duration of wearing ear protection equipment(t=2.383, p=.019), the feeling of wearing ear protection equipment(F=3.602, p=.031) and comfortable sense of wearing ear protection (F=3.919, p=.023) was significant in the preventive behaviour of noise. Conclusion: Considering the results above, we can recognize that there are close relations among the knowledge, attitude and the preventive behaviour of noise. Therefore, it is necessary to develop education - programs for noise-exposed workers' better understanding of noise and preventive behaviors

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2008년도 추계학술대회논문집
• /
• pp.303-310
• /
• 2008

In Korea, the current noise impact assessment has not yet considered the vertical noise propagation property by buildings and other obstacles. And noise control plan has been established without conducting the economic assessment for the noise control facilities. A noise map is used to calculate the noise level based on a theoretical formula or an empirical formula, and also predict the characteristics of vertical propagation by linking with a geometry data. And It is Possible to analyze cost-effect of noise control facilities by consider installation costs. In this study, we addressed the application of noise map for noise impact assessment and cost-effect analysis of noise control facilities.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2008년도 추계학술대회논문집
• /
• pp.311-316
• /
• 2008

It is needed to assess the impact of the road traffic noise for city planning. In Korea, the current noise impact assessment h3s not yet considered the impacts of the multiple reflection, the deflection and the ground attenuation caused by buildings and other obstacles. A noise map is useful tool to solve this problems. But before everything else, suitability of noise map must be assessed for variety of geometry conditions. In this study, we assessed suitability of road traffic noise map by compared measured noise levels with predicted noise levels from each road traffic noise map for Site A, B and C.

• 대한전자공학회:학술대회논문집
• /
• 대한전자공학회 2004년도 하계종합학술대회 논문집(2)
• /
• pp.465-468
• /
• 2004

In this paper, we describe the design and implementation of the new current-current negative feedback (CCNF) voltage-controlled oscillator (VCO), which suppresses 1/f induced low-frequency noise. By means of the CCNF, the high-frequency noise as well as the low-frequency noise is prevented from being converted into phase noise. The proposed CCNF VCO shows 11-dB reduction in phase noise at 10 kHz offset, compared with the conventional differential VCO. The phase noise of the proposed VCO is -87 dBc/Hz at 10 kHz offset frequency from 5.5-GHz carrier. The proposed VCO consumes 14.0 mA at 2.0 V supply voltage, and shows single-ended output power of -12.0 dBm.

• 한국소음진동공학회논문집
• /
• 제19권5호
• /
• pp.454-461
• /
• 2009

Internal aeroacoustics of an axial fan used for circulating cold air in refrigerators are computed by using the hybrid method where CFD, acoustic analogy and BEM techniques are utilized. The unsteady flow field around the axial fan is predicted by solving the incompressible RANS equations with the conventional CFD techniques. Then, main noise sources are extracted from this unsteady flow field predictions using Acoustic Analogy. Lastly, BPF noise generated from an axial fan are predicted using these modeled sources combined with the tailed Green function techniques, which are numerically solved by the BEM technique. This hybrid model is validated by comparing the prediction with the experiment. Then, parameter studies are carried out, which suggest a capability of the current method as a design tool for the low-noise of the current axial fan system in a refrigerator.

• 전력전자학회논문지
• /
• 제17권6호
• /
• pp.539-545
• /
• 2012

Due to merits cost and efficiency, the transformer-less type photovoltaic (PV) inverters have been popularized in the solar market. However, the leakage current flowing through a parasitic capacitor between PV array and ground can cause adverse effect in the transformer-less PV system. In this paper, a bi-directional PV inverter with high efficiency and low noise is proposed for the PV system with an energy storage device. The proposed inverter is a transformer-less type and performs the bi-directional power control between dc sources and grid with high efficiency. In addition, the proposed inverter can suppress the leakage current and obtain low noise characteristic. Finally, 3-kW prototype was implemented to confirm validity of the proposed inverter.

• JSTS:Journal of Semiconductor Technology and Science
• /
• 제7권4호
• /
• pp.241-246
• /
• 2007

This paper presents two novel compensation circuits for leakage current and power supply noise (PSN) in phase locked loop (PLL) using a nanometer CMOS technology. The leakage compensation circuit reduces the leakage current of the charge pump circuit and the PSN compensation circuit decreases the effect of power supply variation on the output frequency of VCO. The PLL design is based on a 32nm predictive CMOS technology and uses a 0.9 V power supply voltage. The simulation results show that the proposed PLL achieves 88% jitter reduction at 440 MHz output frequency compared to the PLL without leakage compensator and its output frequency drift is little to 20% power supply voltage variations. The PLL has an output frequency range of 40 $M{\sim}725$ MHz with a multiplication range of 1-1023, and the RMS and peak-to-peak jitter are 5psec and 42.7 psec, respectively.