• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 춘계학술대회논문집
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• pp.332-339
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• 2007

As the economy has grown and the main industry in Korea has been changed from secondary industry to tertiary industry, the importance of indoor environment has been a matter of common concern, in which one of the main concerns is to improve the indoor acoustic conditions. However, even though this is required more than before, there are no measures to protect the human being from the noise of electric home appliances. This is owing to the absence of the data about sound power level of electric home appliances. So, we investigate the sound power level of them and analyze the acoustical characteristics of each one. First, we tried to investigate the sound power measurement method of each electric home appliance. After it we test the sound power level of them. From the survey, we can know that the vacuum cleaner is the most noisy electric home appliance, and the refrigerator is the least noisy one. The noise of a range hood is distributed over a wide range frequency. Lastly, we intented to propose the proper method measuring sound power level on each electric home appliance.

• 전력전자학회논문지
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• 제14권4호
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• pp.261-267
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• 2009

최대전력점 추적기는 태양광 발전시스템의 대표적인 기능이다. 최대 전력점을 추종하기 위해서는 태양전지의 전압과 전류의 측정을 필요로 한다. 만약 측정 신호에 노이즈가 포함되어 있으면 발생되는 전력이 감소되어 태양광 발전의 효율이 감소하게 된다. 노이즈가 포함된 신호에 확장 칼만 필터 이론을 적용하여 최적의 추정된 신호를 얻어 낼 수 있다. 칼만 필터는 랜덤 노이즈가 포함된 신호에서 최적의 신호를 얻어내는데 사용된다. 또한 칼만 필터의 적용결과로 인덕터 전류와 같은 측정하지 않는 신호도 센서리스 추정이 가능하다. 본 논문에서는 시스템 모델링 방법과 확장 칼만 필터 설계 방법이 소개된다. 실험 결과로서 제안된 제어기의 성능을 확인하였다.

• JSTS:Journal of Semiconductor Technology and Science
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• 제9권4호
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• pp.216-224
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• 2009

The endless scaling down of the semiconductor process made the impact of the power network noise on the performance of the state-of-the-art chip a serious design problem. This paper compares the performances of two popular circuit reduction approaches used to improve the efficiency of power network noise analysis: moment matching-based model order reduction (MOR) and node elimination-based MOR. As the benchmarks, we chose PRIMA and R2Power as the matching-based MOR and the node elimination-based MOR. Experimental results indicate that the accuracy, efficiency, and memory requirement of both methods very strongly depend on the structure of the given circuit, i.e., numbers of the nodes and sources, and the number of moments to preserve for PRIMA. PRIMA has higher accuracy in general, while the error of R2Power is also in the acceptable range. On the other hand, PRIMA has the higher efficiency than R2Power, only when the numbers of nodes and sources are small enough. Otherwise, R2Power clearly outperforms PRIMA in efficiency. In the memory requirement, the memory size of PRIMA increases very quickly as the numbers of nodes, sources, and preserved moments increase.

• 한국소음진동공학회논문집
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• 제11권8호
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• pp.303-313
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• 2001

The identification of power flow in dynamically loaded structures Is essential in the analysis of structure-borne noise. However there are no general purpose tools to estimate powers flow. To make matters worse. It is very difficult to measure it. The power flow can be formulated in terms of balance forces(ELFORCE) at each element and velocities at the associated node obtained with MSC/NASTHAN. In this paper the procedure which is consist of the computations of the balance forces of al1 elements and the velocities at all nodes using MSC/NASTRAN. The calculations of the power f1ow at each element using PCL(PATRAN Command Language) and the Preparation of post -processes is set UP.

• Journal of Power Electronics
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• 제12권4호
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• pp.632-642
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• 2012

This paper presents a filter analysis of conducted Electro-Magnetic Interference (EMI) in switching power converters (SPC) based on noise impedances. The EMI characteristics of SPC can be analytically deduced from a circuit theoretical viewpoint. The analytical noise model is investigated to get a full understanding of the EMI mechanism. It is shown that with suitable and justified model, filters pertinent to EMI noise is investigated. The EMI noise is identified by time domain measurements associated with an isolated half-bridge ac-dc converter. Practical filters like LC filter, ${\pi}$ filter and complete EMI filters are investigated. The proposed analysis and results can provide a guideline for improving the effectiveness of filtering schemes in SPC. Experimental results are also included to verify the validity of the proposed method. The results obtained satisfy the Federal Communications Commission (FCC) class A and class B regulations.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2005년도 ICCAS
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• pp.2362-2367
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• 2005

This paper reports a technique for discriminating double talk and echo path change using the stochastic characteristics of power change for an adaptive noise canceller. The causes of rapid error increasing are double talk and echo path change. When the echo path is changed, the system corrects the impulse response in order to reduce the error. However, in the case of double talk, the system has to suspend the updating impulse response in order to maintain the quality of the voice signal. In the conventional system, it was difficult to discriminate between the two situations. In this research, the stochastic characteristics of the voice power change in the double talk period were experimentally verified to be different from the power change during echo path changing. Based on the results, a new double talk detection method is proposed.

• Current Optics and Photonics
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• 제7권6호
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• pp.708-713
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• 2023

A robust all-fiber nonlinear amplifying loop-mirror-based mode-locked femtosecond laser is demonstrated. Power-dependent nonlinear phase shift in a Sagnac loop enables stable and power-efficient mode-locking working as an artificial saturable absorber. The pump power is adjusted to achieve the lowest intensity noise for stable long-term operation. The minimum pump power for mode-locking is 180 mW, and the optimal pump power is 300 mW. The lowest integrated root-mean-square relative intensity noise of a free-running mode-locked laser is 0.009% [integration bandwidth: 1 Hz-10 MHz]. The long-term repetition-rate instability of a free-running mode-locked laser is 10^-7 over 1,000 s averaging time. The repetition-rate phase noise scaled at 10-GHz carrier is -122 dBc/Hz at 10 kHz Fourier frequency. The demonstrated method can be applied as a seed source in high-precision real-time mid-infrared molecular spectroscopy.

• 환경영향평가
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• 제16권1호
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• pp.99-105
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• 2007

Since 1990s, the railway noise has been researched and developed in our nation. First of all, what's causing the noise and how to eliminate the cause of the noise must be found out. Secondly, cutting off the propagation path of the noise from the noise source to the receiving points. In this study the characteristics of prediction formula for the assessment of railway noise used in some nations including Korea were investigated. In order to develop the prediction formula of the railway noise, the noise radiated from railway vehicle, rails and sleepers, characteristics of noise barrier, velocity of train, ground effects, roughness should be analyzed and predicted. Especially, on the basis of acoustics, the characteristics of source are applied to acoustic power and directivity information.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2008년도 춘계학술대회논문집
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• pp.345-349
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• 2008

In this paper, environmental noise analysis was performed for large power plant and desalination plant. Ray tracing method was used to predict inside noise of turbine building. It is important to design the plant with the allowable noise level. To improve the accuracy, main noise sources were estimated based on the field data. As the results of analysis, it was concluded that noise levels slightly exceed the specified noise limit in turbine building inside. In order to reduce the noise level, adding sound-absorbing materials to inside wall of turbine building was suggested and verified with the confirmed analysis model.

• International Journal of Railway
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• 제4권3호
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• pp.70-73
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• 2011

Controlling the exterior and interior noise emission has become an important issue in the research and development of high speed trains. As the operating speed of the train increases, the noise emission characteristics are expected to deviate from that of the existing trains due to several changes in the basic train layout. For train speed in excess of 350 km/h in particular, the aerodynamic noise component starts to exceed the structure-borne noise component, and even an incremental speed increase is accompanied by a rapid elevation in the noise level. The present study presents an engineering approach for predicting the aerodynamic noise level at the design stage for high speed trains. The experimental noise measurements from test run of Korean high speed train under development are presented as a partial validation of the proposed approach. While the overall aerodynamic noise can be cast in a single power law relationship against the train speed, different parts of the train show power law relationships unique to each component.