• Journal of the Society of Naval Architects of Korea
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• v.61 no.1
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• pp.1-7
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• 2024

Underwater sound speed is an important analysis parameter on an estimation of the underwater radiated noise (URN) emitted from vessels. This paper aims to present an underwater sound speed measurement procedure using a cross-correlation of time-domain acoustic signals and validate the procedure through an experiment in a reverberant water tank. For the purpose, time-domain acoustic signals transmitted by a Gaussian pulse excitation from an acoustic projector have been measured at 20 hydrophone positions in the reverberant water tank. Then, the sound speed in water has been calculated by a linear regression using 190 cross-correlation cases of distances and time lags between the received signals and the result has been compared with those estimated by the existing empirical formulae. From the result, it is regarded that the presented experimental procedure to measure an underwater sound speed is reliably applicable if the time resolution is sufficiently high in the measurement.

• Journal of Korea Society of Digital Industry and Information Management
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• v.20 no.3
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• pp.13-23
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• 2024

For the purpose of predicting credit card customer churn accurately through data analysis Detecting and tracking objects in continuous video is essential in self-driving cars, security and surveillance systems, sports analytics, medical image processing, and more. Correlation tracking methods such as Normalized Cross Correlation(NCC) and Sum of Absolute Differences(SAD) are used as an effective way to measure the similarity between two images. NCC, a representative correlation tracking method, has been useful in real-time environments because it is relatively simple to compute and effective. However, correlation tracking methods are sensitive to rotation and size changes of objects, making them difficult to apply to real-time changing videos. To overcome these limitations, this paper proposes an object tracking method using the Histogram of Oriented Gradients(HOG) feature to effectively obtain object data and the Convolution Neural Network(CNN) algorithm. By using the two algorithms, the shape and structure of the object can be effectively represented and learned, resulting in more reliable and accurate object tracking. In this paper, the performance of the proposed method is verified through experiments and its superiority is demonstrated.

• KIPS Transactions on Software and Data Engineering
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• v.7 no.6
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• pp.205-220
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• 2018

Software defect prediction is helpful for allocating valuable project resources effectively for software quality assurance activities thanks to focusing on the identified fault-prone modules. If historical data collected within a company is sufficient, a Within-Project Defect Prediction (WPDP) can be utilized for accurate fault-prone module prediction. In case a company does not maintain historical data, it may be helpful to build a classifier towards predicting comprehensible fault prediction based on Cross-Project Defect Prediction (CPDP). Since CPDP employs different project data collected from other organization to build a classifier, the main obstacle to build an accurate classifier is that distributions between source and target projects are not similar. To address the problem, because it is crucial to identify effective similarity measure techniques to obtain high performance for CPDP, In this paper, we aim to identify them. We compare various similarity measure techniques. The effectiveness of similarity weights calculated by those similarity measure techniques are evaluated. The results are verified using the statistical significance test and the effect size test. The results show k-Nearest Neighbor (k-NN), LOcal Correlation Integral (LOCI), and Range methods are the top three performers. The experimental results show that predictive performances using the three methods are comparable to those of WPDP.

• The Journal of Korean Physical Therapy
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• v.23 no.3
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• pp.13-19
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• 2011

Purpose: In real life there are both straight-paths and curved-paths. To evaluate walking ability of both kinds, a figure-8 walking test (F8WT) was developed. The aim of this study was to validate the measure in hemiplegic patients with walking difficulties and to identify correlations of curved walking ability with straight walking ability, motor function, and walking performance ability. Methods: Twenty subjects participated in this study. Curved walking was measured by a F8WT. Straight walking ability was measured by a 10-meter walking test (10MWT). Dynamic balancea bility was measured by timed up and go (TUG) tests. Walking performance ability was measured using a modified motor assessment scale (MMAS). Motor function was measured by the Fugl-Meyer assessment (FMA) scale. Data were analyzed using Pearson correlation analysis. Linear regression analyses were performed to explore other functional tests in mobility ability by F8WT time, 10MWT (dependent variable). Results: There was a significant positive correlation of F8WT time with 10MWT and TUG. There was a significant negative correlation of F8WT time with MMAS and FMA-coordination. There was a significant positive correlation of 10MWT with TUG. There was a significant negative correlation of 10MWT with MMAS and FMA-coordination. The F8WT time for curved walking ability was attributed to 10MWT for straight walking ability as 94% level of contribution. Conclusion: The results suggest that the F8WT is a good instrument for measuring walking ability because there is a robust correlation of F8WT time with 10MWT, TUG, MMAS, and FMA-coordination in hemiplegic patients who, after stroke, have a mobility deficiency.

• Journal of the Korean Academy of Clinical Electrophysiology
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• v.10 no.1
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• pp.29-37
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• 2012

Purpose : The purpose of this study was to establish intra-rater, inter-rater, test-retest reliability, and concurrent validity of figure-of-8 walk test in people with stroke. Methods : The subjects of this study were 17 patients who were diagnosed with a stroke. Subjects were tested twice by the same raters, with 1 day between tests. Subjects were assessed by two physical therapists. Test-retest reliability was calculated using intraclass correlation coefficients (ICC). The concurrent validity was demonstrated by spearman correlation of F8WT with 10m walking test (10MWT), timed up and go test (TUG), Berg balance scale (BBS), dynamic gait index (DGI) and four square step test (FSST). Results : Intra-rater, inter-rater, test- retest of F8WT time, showed high reliability. Intra-rater, inter-rater, test-retest of F8WT steps demonstrated high reliability. Intra-rater, inter-rater, test-retest of F8WT total smoothness score showed below moderate reliability. There was a significant positive correlation of F8WT time with 10MWT, TUG, FSST. There was a significant negative correlation of F8WT time with DGI, BBS. There was a significant positive correlation of F8WT steps with 10MWT, TUG, FSST. There was a significant negative correlation of F8WT steps with DGI. There was a significant positive correlation of F8WT test total smoothness score with BBS. Conclusion : The time, and number of steps in F8WT show high inter, intra-rater, test-retest reliability. The F8WT smoothness shows below moderate reliability. The F8WT shows high concurrent validity with other comparable balance, and walking tests. The F8WT is a valid and reliable measure for assessing walking function in patients with a stroke.

• Journal of the Korean Society for information Management
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• v.24 no.4
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• pp.267-283
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• 2007

In this study, measures of distributional similarity such as KL-divergence are applied to cluster documents instead of traditional cosine measure, which is the most prevalent vector similarity measure for document clustering. Three variations of KL-divergence are investigated; Jansen-Shannon divergence, symmetric skew divergence, and minimum skew divergence. In order to verify the contribution of distributional similarities to document clustering, two experiments are designed and carried out on three test collections. In the first experiment the clustering performances of the three divergence measures are compared to that of cosine measure. The result showed that minimum skew divergence outperformed the other divergence measures as well as cosine measure. In the second experiment second-order distributional similarities are calculated with Pearson correlation coefficient from the first-order similarity matrixes. From the result of the second experiment, secondorder distributional similarities were found to improve the overall performance of document clustering. These results suggest that minimum skew divergence must be selected as document vector similarity measure when considering both time and accuracy, and second-order similarity is a good choice for considering clustering accuracy only.

• Journal of Korea Multimedia Society
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• v.21 no.5
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• pp.609-616
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• 2018

In this paper, we designed a multimodal bio-signal measurement system to observe changes in the brain nervous system and vascular system during sleep. Changes in the nervous system and the cerebral blood flow system in the brain during sleep induce a unique correlation between the changes in the nervous system and the blood flow system. Therefore, it is necessary to simultaneously observe changes in the brain nervous system and changes in the blood flow system to observe the sleep state. To measure the change of the nervous system, EEG, EOG and EMG signal used for the sleep stage analysis were designed. We designed a system for measuring cerebral blood flow changes using functional near-infrared spectroscopy. Among the various imaging methods to measure blood flow and metabolism, it is easy to measure simultaneously with EEG signal and it can be easily designed for miniaturization of equipment. The sleep stage was analyzed by the measured data, and the change of the cerebral blood flow was confirmed by the change of the sleep stage.

• Research in Community and Public Health Nursing
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• v.19 no.4
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• pp.622-635
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• 2008

Purpose: The purpose of this study was to measure the level of job stress and health status and find out factors affecting the health status among circulation enterprise workers. Method: This study was a cross-sectional descriptive study. The subjects were 128 workers whose mean age was 33.2 years. Korean occupational stress questionnaire Short Form was used to measure job stress. Todai Heath Index that was made by Aoki in 1977 and translated by Kim(1997) was used to measure the health status. Results: The total job stress scores of men and woman fell in the lower 50% of Korean workers. Job autonomy and interpersonal conflicts as a subcategories fell in upper level 50% in both men and women and job insecurity fell in the upper level 50% in women. The mean score of health status was 51.47, indicating slightly higher frequency of complains of health symptoms. There was no significant correlation between total job stress and total health status. Finally, factors influencing the health status were organizational system and age. Conclusion: Based on the results of this study, it is necessary to develop comprehensive stress management programs including interventions of personal and organizational levels for promoting workers' health.

• Aerospace Engineering and Technology
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• v.8 no.2
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• pp.8-12
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• 2009

It is absolutely necessary to measure the inlet pressure and temperature of a turbine or a compressor to evaluate the performance of it. And to measure the representative-averaged pressure and temperature of turbine inlet flow, rake is normally used. Rake has several elements for temperature and pressure and several rakes are installed at the inlet to average the radial and circumferential distribution of inlet flow. However the rakes cause unexpected losses and flow distortion at the turbine inlet which make the measured rake data different from true inlet value. So the evaluation of a turbine or a compressor performance becomes not accurate. This study suggest a correlation method which measure the loss by inlet rake and incorporates it in evaluating the performance of turbomachinery.

• Korean Journal of Acupuncture
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• v.33 no.1
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• pp.18-32
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• 2016

Objectives : This study aims to analyze the co-occurrence of pathological symptoms and corresponding acupoints as documented by the comprehensive acupuncture and moxibustion records in the classical texts of Far East traditional medicine as an aid to a more efficient understanding of the tacit treatment principles of ancient physicians. Methods : The Classic of Nourishing Life with Acupuncture and Moxibustion(Zhenjiu Zisheng Jing; hereinafter ZZJ) was selected as the primary reference book for the analysis. The pathology-acupoint co-occurrence analysis was performed by applying 4 values of vector space measures(weighted Euclidean distance, Euclidean distance, $Cram\acute{e}r^{\prime}s$ V and Canberra distance), which measure the distance between the observed and expected co-occurrence counts, and 3 values of probabilistic measures(association strength, Fisher's exact test and Jaccard similarity), which measure the probability of observed co-occurrences. Results : The treatment records contained in ZZJ were preprocessed, which yielded 4162 pathology-acupoint sets. Co-occurrence was performed applying 7 different analysis variables, followed by a prediction simulation. The prediction simulation results revealed the Weighted Euclidean distance had the highest prediction rate with 24.32%, followed by Canberra distance(23.14%) and association strength(21.29%). Conclusions : The weighted Euclidean distance among the vector space measures and the association strength among the probabilistic measures were verified to be the most efficient analysis methods in analyzing the correlation between acupoints and pathologies found in the classical medical texts.