• Journal of the Korean Institute of Telematics and Electronics S
• /
• v.35S no.4
• /
• pp.128-138
• /
• 1998

This paper describes a principle of the conducted noise separator which can separate the conducted noise to the common mode and differential mode(normal mode), and presents the transfer characteristics of the separator designed and manufactured. We separated the conducted noise generated from switched mode converter to the CM and DM conducted noise, and also analyzed the source and path of conducted noise in the converter by the conducted noise separator. Since we could easily get the characteristics of the CM and DM conducted noise by the separator, we could efficiently determine the contermeasures for the reduction of the conducted noise and establish the foundation of the systematic procedure for the design of low pass filter.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.25 no.6
• /
• pp.853-856
• /
• 2021

In this paper, a low noise amplifier having high gain and low noise by using input and inter stage matching circuits has been designed. A current-reused two-stage common-source topology is adopted, which can obtain high gain and low power consumption. Deterioration of noise characteristics according to the source inductive degeneration matching is compensated by adopting additional matching circuits. Moreover trade-offs among noise, gain, linearity, impedance matching, and power dissipation have been considered. In this design, 0.18-mm CMOS process is employed for the simulation. The simulated results show that the designed low noise amplifier can provide high power gain and low noise characteristics.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.25 no.4
• /
• pp.275-283
• /
• 2015

The aim of this study is to estimate the noise exposure of roadside apartment complex according to the characteristics of apartment complex. The facade noise level of residential buildings and the ground noise level inside apartment complexes were predicted and analyzed using noise mapping based on a computerized noise model. In addition, the correlation analysis between these noise levels and the characteristics of apartment complex such as traffic volume, building coverage, the number of adjacent roads, etc. was done in a total of 21 apartment complexes. The results showed that building facade noise level and ground noise level were positively correlated with traffic volume (correlation coefficient, r=0.616~0.623) and the number of adjacent roads (r=0.340~0.496). On the other hand, they were negatively correlated with building coverage (r=-0.413~-0.477) and complex area per the number of roads (r=-0.478~-0.615).

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.19 no.11
• /
• pp.1222-1230
• /
• 2009

A theoretical model was developed to compute the effect of a bubble layer in reducing the radiation noise generated by a force applied on an infinite flat plate considering the noise of multi-bubbles. Using the model, the effectiveness of a bubble layer in reducing the structure-borne noise of the plate was evaluated to consider various parameters such as the source noise levels, the thickness of bubble layers, the volume fractions and the frequency characteristics of bubbly fluids. Considering the noise of multi-bubbles, the actual reduction effect of radiation noise using a bubble layer was expected in cases of high source levels, high volume fractions of bubbles and large thickness of the bubble layer above the resonance frequency of the bubble layer. Accordingly, it is recommended that the thickness of a bubble layer, the source noise level and the characteristics of bubbly fluids should be optimized cautiously to maximize noise reduction effects.

• Nuclear Engineering and Technology
• /
• v.51 no.3
• /
• pp.719-722
• /
• 2019

Gamma-ray images generally suffer from a lot of noise because of low photon detection in the gamma camera system. The purpose of this study is to improve the image quality in gamma-ray images using a gamma camera system with a fast nonlocal means (FNLM) noise reduction algorithm with an acceleration function. The designed FNLM algorithm is based on local region considerations, including the Euclidean distance in the gamma-ray image and use of the encoded information. To evaluate the noise characteristics, the normalized noise power spectrum (NNPS), contrast-to-noise ratio (CNR), and coefficient of variation (COV) were used. According to the NNPS result, the lowest values can be obtained using the FNLM noise reduction algorithm. In addition, when the conventional methods and the FNLM noise reduction algorithm were compared, the average CNR and COV using the proposed algorithm were approximately 2.23 and 7.95 times better than those of the noisy image, respectively. In particular, the image-processing time of the FNLM noise reduction algorithm can achieve the fastest time compared with conventional noise reduction methods. The results of the image qualities related to noise characteristics demonstrated the superiority of the proposed FNLM noise reduction algorithm in a gamma camera system.

• Journal of Korean Society of Environmental Engineers
• /
• v.31 no.12
• /
• pp.1123-1128
• /
• 2009

Noise radiated from medical treatment at dental clinic will affect the patients. On such point of view, We investigated the noise characteristics in case of medical treatment (scaling, tooth eliminating) and non-medical examination (idling) and also evaluated the degree of indoor noise using the evaluation index such as PSIL, NRN and made up a questionnaire about the reactions to noise. As a result of noise evaluation, it shows that the range of noise level is 67.7~78.3 dB(A) and frequency is very high (above 4 k Hz) and respondents are affected by noise (unpleasantness, hesitation to visit dental clinic, shivering with noise, being astonishment). Analysis by PSIL showed that it was no problem to conversation between worker and patient. But it exceeded the noise permit level in working space by NR-curve. To relieve a fear of noise in patients, they are considered to offer the ear protection, choose the low noisevibration equipment and use the masking effect. They are of great advantage to dental clinics to i prove dental service and competitiveness.

• The Korean Journal of Applied Statistics
• /
• v.31 no.5
• /
• pp.555-572
• /
• 2018

Noise reduction processes that reduce or eliminate noise (caused by a variety of reasons) in noise contaminated image is an important theme in image processing fields. Many studies are being conducted on noise removal processes due to the importance of distinguishing between noise added to a pure image and the unique characteristics of original images. Adaptive filter and sigma filter are typical noise reduction filters used to reduce or eliminate noise; however, their effectiveness is affected by accurate noise estimation. This study generates a distribution of noise contaminating image based on a Dirichlet normal mixture model and presents a Bayesian approach to distinguish the characteristics of an image against the noise. In particular, to distinguish the distribution of noise from the distribution of characteristics, we suggest algorithms to develop a Bayesian inference and remove noise included in an image.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.33 no.4
• /
• pp.1631-1638
• /
• 2013

Distress data, IRI, etc. are important factors in the evaluation of pavement condition. Recently, the need to consider tire-pavement noise in PMS (pavement management system) is raised. Generally, tire-pavement noise highly depends on the characteristics of pavement texture. Therefore, estimation of texture characteristics may give useful information to predict tire-pavement noise. Measurement of MPD (Mean Profile Depth) by using PLP (Portable Laser Profiler) provide very fast. The texture characteristics by means of MPD can be in a short time. hence, It can be a good alternative to give noise information, if MPD and tire-pavement noise have robust relationship. In this study, MPD and tire-pavement noise were simultaneously collected on the number of asphalt section to evaluate the tire-pavement noise due to the pavement texture characteristics. A set of statistical analysis was performed to propose relationship between tire-pavement noise and MPD for asphalt concrete pavement.

• Journal of KSNVE
• /
• v.8 no.1
• /
• pp.112-121
• /
• 1998

In this report, Experimental analysis for main factors and analyzing methods of electro-magnetic noise and no loading noise was conducted because of noise of AC generator, which is peripheral equipment by reduction of engine noise that would be the main cause of vehicle radiation noise. In addition, This is intended to suggest the noise reduction development basis of AC generator for actual fan and electro-magnetic noise by making-analyzing-testing it's sample.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2003.11a
• /
• pp.515-520
• /
• 2003

In these days, the civil appeal and dispute about environmental noise grows larger every year. But there are not suitable systems for measurement and management of environmental noise. This paper proposes environmental noise measurement, characteristic analysis and evaluation, management system using Internet. We can measure and manage the environmental noise also, analyze characteristics of noise by the environmental noise management system using Internet.