• The Journal of the Acoustical Society of Korea
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• v.35 no.2
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• pp.102-109
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• 2016

This paper proposes a noise suppression method through SNR (Singal-to Noise Ratio) estimation in the two microphone array environment of close spacing. The conventional method uses a noise suppression method for a gain function obtained through the SNR estimation based on coherence function from full band. However, this method cause performance decreased by the noise damage that affects all the feature vector component. So, we propose a noise suppression method that allocates a frequency domain signal into N constant multi frequency band and each frequency band gets a gain function through SNR estimation based on coherence function. Performance evaluation of the proposed method is shown by comparison with PESQ (Perceptual Evaluation of Speech Quality) value which is an objective quality evaluation method provided by the ITU-T (International Telecommunications Union Telecommunication).

• PNF and Movement
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• v.18 no.3
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• pp.383-392
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• 2020

Purpose: Balance and gait dysfunction caused by aging affect elderly individuals' independent life, which, in turn, can reduce their overall quality of life. The purpose of this study is to compare the differences in the vestibular function of healthy elderly and young adults based on the subjective visual vertical (SVV) test as well as to compare and analyze the gait ability between these two groups to study the differences and association between vestibular, dizziness, and balance ability. Methods: The subjects were 18 young and 16 elderly adults with no neurological or musculoskeletal damage. To evaluate vestibular function, a subjective visual vertical test was performed. To evaluate the gait function, the step time, step length, stride length, stance phase ratio, and swing phase ratio were measured. Balance was evaluated using the Berg Balance Scale (BBS), and dizziness was evaluated using a dizziness handicap inventory (DHI). Results: There were significant differences in the SVV, BBS, and DHI between the young and elderly adults (p < 0.05). The gait variables of the older adults were all significantly different (except for the swing phase ratio) than those of the young adults (p < 0.05). As the result of correlation analysis, the SVV values of the young adults showed a significant negative correlation with step length and stride length (p < 0.05), while the SVV values of the elderly adults only showed a significant positive correlation with the DHI (p < 0.05). Conclusion: The elderly appeared to show a decrease in vestibular function when compared to the young adults, and it is thought that walking and balance function declined, while dizziness increased. Moreover, it is believed that these results can be used as basic data for vestibular rehabilitation in the future.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2002.09a
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• pp.306-309
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• 2002

Micellar-enhanced ultrafiltration was investigated to remediate groundwater contaminated with chromate using a cationic surfactant, cetylpyridinium chloride (CPC). Removal of chromate was expressed as a function of molar ratio of CPC to chromate. With 10 molar ratio of CPC, removal efficiency of chromate was reached to over 99%. The rejection of CPC was 90% at 1 molar ratio, gradually increased as the molar ratio increased.

• Proceedings of the KIPE Conference
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• 2001.10a
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• pp.418-422
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• 2001

To achieve a high performance in direct vector control of induction motor, it is essential to correct estimation of rotor flux. The accuracy of flux observers for induction machines inherently depends on parameter sensitivity. This paper presents an analysis method for conventional flux observers using Parameter Sensitivity. The Parameter sensitivity is defined as the ratio of the percentage change in the system transfer function to the percentage change of the parameter variation. We define the ratio between real flux and estimated flux as the transfer function, and analyzed a parameter sensitivity of this transfer function by simulation.

• Journal of Korean Society for Quality Management
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• v.31 no.4
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• pp.239-246
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• 2003

Dynamic robust design has been regarded as the most powerful design methodology for improving product quality, Dynamic SN ratio adopted in dynamic robust design combines two major quality attributes, the variability around the linear function and the slope of the linear function, into a single design metric. The principal shortcoming associated with the dynamic SN ratio is that the metric is independent of designer's preferences for the quality attributes due to priori sets of attribute tradeoff values inherent in it. Therefore, a more rigorous preference­based design metric to accurately capture designer's intent and preference is needed. A new design metric that can be used in dynamic robust design is proposed. The effectiveness of the proposed design metric is examined with the aid of a demonstrative case study and the results are discussed.

• Proceedings of the KIPE Conference
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• 2001.12a
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• pp.7-10
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• 2001

To obtain a high performance in a direct vector controlled induction machine, it is essential to correct estimation of rotor flux. The accuracy of flux observers for induction machines inherently depends on parameter sensitivity. This paper presents an analysis method for conventional flux observers using Parameter Sensitivity. The Parameter sensitivity is defined as the ratio of the percentage change in the system transfer function to the percentage change of the parameter variation. We define the ratio between real flux and estimated flux as the transfer function, and analyzed a parameter sensitivity of this transfer function.

• Journal of the Korean Statistical Society
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• v.24 no.1
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• pp.45-64
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• 1995

When a random sample is taken from a certain class of discrete and continuous distributions whose support depend on two parameters, we could find that there exists the complete and sufficient statistic for parameters which belong to a certain class, and fomulate the uniformly minimum variance unbiased estimator (UMVUE) of any estimable function. Some UMVUE's of parametric functions are illustrated for the class of the distribution. Especially, we find that the UMVUE of some estimable parametric function from the truncated normal distribution could be expressed by the version of the Mill's ratio.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.10a
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• pp.659-663
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• 1995

The fiber oriented conditied inside fiber reinforced composite material is a basic factor of mechanical properties of composite materials. It is very important to measure the fiber orientation angel for the determination of molding conditions, mechanical charactistics, and the design of composite materials. In the work, the fiber orientation distribution of simulation figure plotted by PC is measured using image processing in order to examine thr accuracy of intersection counting method. The fiber orientation function measured by intersection countingmethod using image processing is compared with the calculated fiber orientation function. The results show that the measured value of fiber orientation function using intersection counting method is lower than the calculated value, because the number of intersection between the secant line and the fiber with smaller fiber aspect ratio is counted less than with larger fiber aspect ratio.

• Proceedings of the KIEE Conference
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• 2001.07b
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• pp.1176-1178
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• 2001

To obtain a high performance in a direct vector controlled induction machine, it is essential to correct estimation of rotor flux. The accuracy of flux observers for induction machines inherently depends on parameter sensitivity. This paper presents an analysis method for conventional flux observers using parameter Sensitivity. The Parameter sensitivity is defined as the ratio of the percentage change in the system transfer function to the percentage change of the parameter variation. We define the ratio between real flux and estimated flux as the transfer function, and analyzed a parameter sensitivity of this transfer function.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2001.09a
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• pp.171-176
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• 2001

Recent building structures are superior in its ability but they are light and flexible, and so have problems of vibration. In general, the problem of vertical vibration is not considered in structural design. However, in terms of serviceability for inhabitants in buildings, the estimation of vibration in design stage is important. Characteristics of vertical vibration is changed by modeling method of beam-column joint. To check the characteristics of vertical vibration, many tests and analyses were conducted on constructing building in Seoul. Results of tests and analyses were compared using transfer function. As a results, to check the vertical vibration, the cramp ratio of beam-column joint must be considered and reduced in structural design.