• Transactions of the Korean Society of Mechanical Engineers
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• v.9 no.1
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• pp.71-80
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• 1985

The various sizes of wires are attached to the outside of the inner tube in a double pipe heat exchanger to enhance the thermal performance. The diameters of the wires range from 0.5mm to 1.6mm while the pitches are chosen between 5mm and 50mm. Experiments have been performed with the range of Reynolds numbers from 15000 to 30000 in annular space where air flows. The friction factors are increased by 1.5 to 4.5 times depending on the sizes and the pitches of the wires. However, the Nusselt numbers are increased by the factors of 1.8 to 2.8 within this experimental range. It is suggested that there should be an optimum configuration rendered when the weighting values of the heat transfer promotion and the pumping power are given.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.41 no.6
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• pp.221-229
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• 2004

We present new digital watermarking scheme that embeds a watermark according to the characteristics of the image or video. The scheme is compatible with established image compression standard. We define a weighting function using a parent-child structure of the DCT coefficients in a block to embed a maximum watermark. The spatio-frequency localization of the DCT coefficients can be achieved with this structure. In the detection stage, we present an optimum a posteriori threshold with a given false detection error probability based on the statistical analysis. Simulation results show that the proposed algorithm is efficient and robust against various signal processing techniques. Especially, they are robust against widely used coding standards, such as JPEG and MPEG.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.209-213
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• 1997

This paper deals with sensing ability of $2^{nd}$ smart sensor that has a sensing ability of distinguish materials. We have developed new signal processing method that have distinguish different materials. We made the $2^{nd}$ smart sensor for experiment. The second type of smart sensor is HH type. We have developed a new signal processing method that can distinguish among different materials. The estimation method (RSAIIn dex) is developed for $2^{nd}$ smart sensor(HH smart sensor). Experiment and analysis are executed for estimation the new method. We estimated sensing ability of $2^{nd}$ smart sensor with RsA, method. Sensing Ability of the $2^{nd}$ smart sensor were evaluated relatively through a new RsAl method. According to frequency changing, influences of the $2^{nd}$ smart sensor are evaluated through a new recognition index RSAI. Applications of this method are for finding abnormal conditions of objects (automanufacturing), feeling of objects (medical product), robotics, safety diagnosis of structure, etc.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.14 no.11
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• pp.1195-1202
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• 2004

The international competition in refrigerator markets has continuously required the research for sound quality of a refrigerator to improve the quality of a life. In this paper, A new method for evaluation of the sound quality of a refrigerator is developed based on human sensibility engineering by using ANN(artificial neural network). In this paper, the loudness and the sharpness of the refrigerator's signals was used for the input value in ANN's training process because the loudness and the sharpness has a good correlation between the output of the ANN and the target of the individual evaluation In the training process. Two input factor was used repeatedly in the training process to get more optimum weighting value. And then finally we developed the sound quality index of a refrigerator. The developed sound quality index was confirmed by the 96.5 % of correlation between the output of the ANN and the real evaluation. It will be applied to evaluate the sound quality of a refrigerator in the industry.

• The Journal of the Acoustical Society of Korea
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• v.22 no.4
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• pp.315-322
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• 2003

We propose a channel-attentive Mel frequency cepstral coefficient (CAMFCC) extraction method to improve the recognition performance of speech that is partially corrupted in the frequency domain. This method introduces weighting terms both at the filter bank analysis step and at the output probability calculation of decoding step. The weights are obtained for each frequency channel of filter bank such that the more reliable channel is emphasized by a higher weight value. Experimental results on TIDIGITS database corrupted by various frequency-selective noises indicated that the proposed CAMFCC method utilizes the uncorrupted speech information well, improving the recognition performance by 11.2% on average in comparison to a multi-band speech recognition system.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.38 no.1
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• pp.43-53
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• 2001

WT(Wavelet Transform) is used to avoid blocking effect that is the disadvantage of JPEG using DCT(Discrete Cosine Transform). Because the proposed coding scheme is the same as JPEG, the proposed algorithm is compatible with that of JPEG. To achieve the goal, WT'ed image is reconstructed into 8$\times$8 coding block. Each coding block is quantized with the proposed weighting matrix that is derived from human visual characteristic and error analysis in WT'ed domain. By experiments, the proposed algorithm is superior to JPEG, in terms of PSNR(Peak Signal to Noise Ratio) and WMSE(Weighted Mean Square Error).

• International Journal of Highway Engineering
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• v.19 no.5
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• pp.89-96
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• 2017

PURPOSES: This study aims to develop a rational procedure for estimating the pavement roughness index considering vehicle wandering. METHODS : The location analysis of the passing vehicle in the lane was performed by approximately 1.2 million vehicles for verification of the wandering distribution. According to verification result, the distribution follows the normal distribution pattern. The probability density function was estimated using each lane's wandering distribution model. Then the procedure for applying a weighted value into the lane profile was conducted using this function. RESULTS : The modified index, MRIw, with consideration towards applying the wandering weighted value application was computed then compared with MRI. It was found that the Coefficient of Variation for distribution of lateral roughness index in the lane was high in the case of a large difference between each index (i.e., MRIw and MRI) observed. CONCLUSIONS : This result confirms that the new procedure with consideration of the weight factor can successfully improve the lane representative characteristics of the roughness index.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.13 no.7
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• pp.539-547
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• 2003

The prototype of Korean high speed train(KHST), composed of two power cars, two motorized cais and three trailer cars, has been designed, fabricated and tested. In this paper. the body vibration has been reviewed from the viewpoint of the vehicle's safety, the ride comfort and the vibration limits for components and sub-assemblies mounted on the car-body using by analytical method and experimental method. The on-line test of KHST has been tarried out up to 260 ㎞/h in the KTX line and the results of the on-line test show that KHST has no problems in the vehicle's safety. the comfort ride and the vibration limits at this speed. And the characteristics of body vibrations has been Predicted at 300 ㎞/h and 350 ㎞/h by fitting curve about the measured acceleration signals.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.1752-1761
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• 2000

This paper describes the far-field estimation using the near-field measurement data. Measurement in far-field region gives us the acoustical characteristics of the source but in general measurement is made in near-field such as acoustic water tank or anechoic chamber, so far-field acoustical characteristics of the source should be predicted from near-field data. In this case, the number of measurement points in the near field which relates to the accuracy of the predicted field and the amount of data processing, should be optimized. Existing papers say that measurement points is proportional to kL and depends on geometry and directivity of the source. But they do not give us any definite criterion for the required number of measurement points. Boundary Collocation Method which is one of the far-field prediction methods, is analyzed based on Helmholtz integral equation and Green function and it has been found that the number of measurement points is optimized as 0.54kL which is about one half of the existing results.

• Phonetics and Speech Sciences
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• v.11 no.4
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• pp.63-70
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• 2019

This study investigated individual variability of L2 learners' categorical judgments of L2 stops by exploring English learners' perceptual processing of two acoustic cues (voice onset time [VOT] and f0) and working memory capacity as sources of variation. As prior research has reported that English speakers' greater use of the redundant cue f0 was responsible for gradient processing of native stops, we examined whether the same processing characteristics would be observed in L2 learners' perception of Korean stops (/t/-/t^h/). 22 English learners of L2 Korean with a range of L2 proficiency participated in a visual analogue scaling task and demonstrated variable manners of judging the L2 Korean stops: Some were more gradient than others in performing the task. Correlation analysis revealed that L2 learners' categorical responses were modestly related to individuals' utilizations of a primary cue for the stop contrast (VOT for L1 English stops and f0 for L2 Korean stops), and were also related to better working memory capacity. Together, the current experimental evidence demonstrates adult L2 learners' top-down processing of stop consonants where linguistic and cognitive resources are devoted to a process of determining abstract phonemic identity.