• Journal of Technologic Dentistry
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• v.15 no.1
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• pp.27-41
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• 1993

Degree of noise by personal dental laboratory working process and degree of noise by complex dental laboratory working process were measured separtely. The time of exposure to noise greater than 70dB was analyzed. Then, the whole degree of noise in dental laboratory was estimated on the basis of afore-mentioned information. Questionaire were employed to investigate the mental, emotional and physiological effects of noise in dental technicians, The purpose of this study was to provide basic information on keeping dental techneicans who are exposed to noise pollution in good working condition and good health. Results obtained are as follows ; 1. Polishing process in each working part showed high degree of noise greater than 70dB in terms of degree of noise by personal working. 2. Degree of noise by complex working process in each working part was greater than that of personal working process. 3. Time of exposure to noise complex working process the part of porcelain 150min, partial denture 120 min, crown and bridge 100 min, full denture 80 min. 4. Degree of noise by time in dental laboratory was 80dB in general for polishing process and below 75dB for waxing process. 5. Effects of noise on mental and emotional state of dental technicians showed that they felt irritated every day(14%), irritated once in a while(29%) and easily ger mad(19%). 6. Effects of noise on heart and stomach were hyper-gastric acid(38%), gastric ulcer(11%), gastritis(5%), deuodenal ulcer(3%) and weak heart function(32%). 7. Effects of noise in the hearing ability were weak(39%), moderate(33%) and normal(14%) Data presented in this study demonstrated that noise in the dental laboratory exerts profound effect on dental technicians mentally, physiologically and emotionally, in light of the above results, therefore, it appears advisable to devots substantial on the management of working condition and put further(continuing) efforts in the investigation for reducing noise problem.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.04a
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• pp.787-790
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• 2012

In downtown, construction noise related claims are the most important issues. Sometimes noise related claims halt the construction process. Therefore, Introduction of noise reduction measures is common to construction process with a loud noise. This case is about concrete pouring for mat foundation of super tall building. Concrete pouring process using High Pressure Pumping machine causes high noise level in the vicinity of area. And large number of transit-mixer truck cause traffic congestion. This paper introduces effort and process to prevention of construction noise claims on massive scale concrete pouring.

• Structural Engineering and Mechanics
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• v.47 no.3
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• pp.361-381
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• 2013

A Bayesian probabilistic method is proposed for online estimation of the process noise and measurement noise parameters for Kalman filter. Kalman filter is a well-known recursive algorithm for state estimation of dynamical systems. In this algorithm, it is required to prescribe the covariance matrices of the process noise and measurement noise. However, inappropriate choice of these covariance matrices substantially deteriorates the performance of the Kalman filter. In this paper, a probabilistic method is proposed for online estimation of the noise parameters which govern the noise covariance matrices. The proposed Bayesian method not only estimates the optimal noise parameters but also quantifies the associated estimation uncertainty in an online manner. By utilizing the estimated noise parameters, reliable state estimation can be accomplished. Moreover, the proposed method does not assume any stationarity condition of the process noise and/or measurement noise. By removing the stationarity constraint, the proposed method enhances the applicability of the state estimation algorithm for nonstationary circumstances generally encountered in practice. To illustrate the efficacy and efficiency of the proposed method, examples using a fifty-story building with different stationarity scenarios of the process noise and measurement noise are presented.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.10 no.1
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• pp.54-61
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• 2011

Ball screw systems are largely used in industry for motion control and motor applications. But the problem of noise, which really perplexes us, is highly correlated with the quality in ball screw systems all the way. In this paper, machining process parameters were evaluated in respects of technique, business, produce and quality to verify which impact influences the noise most. In order to adjust and compare, two comparison groups were set with the present parameters bench mark. Different ball screws were produced as specimens for the noise tests. Through comparing the noise performance of different parameters in the machining process respectively, a group of optimized machining process parameters were obtained. Another noise test was proceeded to know how noise performance was improved by optimizing the machining process parameters. At last, surface roughness tests have been done to know how surface roughness improved by optimization. The improvement of surface roughness is the main factor influences the noise performances.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.24 no.5
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• pp.682-685
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• 2020

In this paper, we analyze the dominant noise source of conventional inductively degenerated common-source (CS) cascode low noise amplifier (LNA) when width and gate length of stacked transistors vary. Analytical MOSFET and its noise model are used to estimate the contributions of noise sources. All parameters are based on measured data of 60nm, 90nm and 130nm CMOS devices. Based on the noise analysis for different frequencies and device parameters including process nodes, the dominant noise source can be analyzed to optimize noise figure on the configuration. We verified analytically that the intuctively degenerated CS topology can not sustain its benefits in noise above a certain operation frequency of LNA over different process nodes.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.13 no.7
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• pp.532-538
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• 2003

This paper studies on the noise reduction for a small automobile DC Motor (a window motor) using the 6 sigma process. The application of 6 sigma process suggested reliable and valuable statistical data for the quality of the DC motor at the production line. In the measurement step in 6 sigma process. the FMEA(failure mode effect analysis) were used for the detection of noise sources. The application of 6 sigma Process gave not only the improving method for the quality of the DC motor but also the confidence of improvement Itself since it was done on the basis of the test results for a number of DC motors at the production line. Consequently the 6 sigma process was proved very effective for the noise reduction at the production line.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.790-795
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• 2002

The object of this research is limited to the reduction of compression process noise only among the main sources of compressor noise such as motor noise, compression process noise, and valve port flow noise. Thus the research is focused on the wave motion rather than the particle motion of sound wave travels. A muffler is a commonly used device to reduce the compression process noise, generated by the pressure pulsations caused by the cyclic compression process. In this research, the acoustic characteristics of the muffler are analyzed by using the normal gradient integral equation proposed by Wu and Wan. Moreover, a commercial code SYSNOISE developed by indirect variational boundary integral equation is also used to validate the results. For the noise reduction, the topology optimization technique using a genetic algorithm is used. The number, size and position of the muffler holes are considered as design variables. Compared with original design, the optimized design has very improved acoustic characteristics. Both numerical and experimental analyses are used to evaluate new design.

• 유체기계공업학회:학술대회논문집
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• 2006.08a
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• pp.259-262
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• 2006

This paper introduces the process of reducing the automobile wind noise by using acoustic holography. First, a microphone array scans a side or plane under an automible step-by-step. Second, a pressure on a source plane is calculated. Third process is to analyze how much individual sources contribute to interior noise. Fourth process is to control important noise sources determined by the contribution analysis. This paper deals with the entire process, theoretical and experimental problems.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.509-514
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• 2002

This paper studies on the noise reduction for a small automobile DC Motor (a window motor) using the 6 sigma process. The application of 6 sigma process suggested reliable and valuable statistical data for the quality of the DC motor at the production line. In the measurement step in 6 sigma process, the FMEA(Failure Mode Effect Analysis) were used for the detection of noise sources. The application of 6 sigma process gave not only the improving method for the quality of the DC motor but also the confidence of improvement itself since it was done on the basis of the test results for a number of DC motors at the production line. Consequently the 6 sigma process was proved very effective for the noise reduction at the production line.

• Journal of the Korean Statistical Society
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• v.29 no.3
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• pp.319-336
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• 2000

A mixed model with a white noise process and an IMA(0,1,1) process is considered as a process model. It is assumed that the process is a white noise in the absence of a special cause and the process changes to an IMA(0,1,1) due to a special cause. One useful scheme in measuring the process level is to use the variable measurement interval (VMI) between measurement times according to the value of the previous chart statistic. The advantage of the VMI scheme is to measure the process level infrequently when in control to save the measurement cost and to measure frequently when out of control to save the off-target cost. This paper considers the VMI scheme in order to detect changes in the process model from a white noise to an IMA(0,1,1). The VMI scheme is shown to be effective compared to the standard fixed measurement interval (FMI) scheme in both statistical and economic contexts.