• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.22 no.12
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• pp.36-46
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• 2008

This paper is to study on the Construction of Test circuit and Unification of Experiment Method for high voltage gas-insulated load switch using high power testing system The high power testing system is a equipment to verify electrical and mechanical performance on electrical product. The system consist of short-circuit generator, back-up breaker, making switch, impedance, high voltage transformer, low voltage transformer, measuring and protection system, etc. Using this system, we can test related to high power, for example, short-time current test, active load Current test, magnetizing Current test, capacitive current test, closed loop current test, etc. Standards of high voltage gas-insulated load switch that is in use domestic distribution line are ES 5925-0002, IEC 60265-1, IEC 62271-1 and IEEE C 37.74, etc. In this paper, we standardized on the test procedure, organization of test circuit and analysis of measured data prescribed many difference standards, and applied this test method to 600[MVA] high power testing system. So that we can test the load switch satisfied standards.

• Journal of the Korean Society of Safety
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• v.34 no.5
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• pp.31-36
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• 2019

This study made a testing device to evaluate the distribution board management system. Power was supplied to the testing device using a loading-back method and the voltage applied to it was 440 V at the same turn ratio. When the human body electric shock current is 30 mA, the breaking time is set to be less than 240 ms while 30~45 mA current is flowing. The test result shows that in the case of the R-phase it was measured to be 5.19 Hz (193 ms). And the S-phase and T-phase were perfectly cut off at 5.39 Hz (186 ms) and 5.71 Hz (175 ms), respectively. When the human body electric shock current is 60mA, the breaking time is set to be less than 120 ms while 45~75 mA current is flowing. The test result shows that the R-phase, S-phase, and T-phase were accurately cut off at 8.39 Hz (11 ms), 8.87Hz (113 ms) and 9.69 Hz (103 ms), respectively. When the human body electric shock current is 90 mA, the breaking time is set to be less than 48 ms while 75 mA current is flowing. The test result shows that the R-phase, S-phase, and T-phase were accurately cut off at 19.8 Hz (50.4 ms), 16.9 Hz (59.2 ms), and 17.9 Hz (56.0 ms), respectively. That is, the developed testing device satisfied all the requirements of the distribution board evaluation criteria, and it becomes available for the performance evaluation of the distribution board management system.

• Proceedings of the KSR Conference
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• 2011.05a
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• pp.1049-1058
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• 2011

Current status of the low-to-medium speed Urban MagLev Systems were studied, for Korean UTM(Urban Transit Maglev), Japanese HSST(High Speed Surface Transport) and Chinese CMS(Chinese Maglev System). Mainly, process of development, testing facilities, specifications of maglev systems and public service program were compared respectively.

• The Journal of Korean Physical Therapy
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• v.17 no.3
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• pp.311-327
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• 2005

The purpose of this study was to investigate the effects of diaphragmatic breathing on activation of trunk muscles of patients with low back pain. Diaphragmatic breathing may affect activation of trunk muscles. The assumptions are as follows: the crural diaphragm attatches to the lumbar vertebrae from L1 to L3, the voluntary downward pressurization of the diaphragm increases intra-abdominal pressure, and this increases the stiffness of the spine. Diaphragmatic breathing increases intra-abdominal pressure and the increased intra-abdominal pressure may contribute to the lumbar stability. Sixty patients with low back pain were randomly divided into two groups. Experimental group performed diaphragmatic breathing exercise with six breathing positions and control group performed only the breathing positions for five times per week during six weeks. % maximal voluntary contraction(% MVC) of trunk muscles on six breathing positions of experimental and control group was measured according to testing period of pre test, three weeks, and six weeks. The repeated measures of one-way ANOVA were used to analyze % MVC on trunk muscles of experimental and control group according to testing period. The results of this study were as follows: First, % MVC of right and left erector spinae in the right leg extension position indicated the statistically significant difference in experimental group which performed diaphragmatic breathing exercise rather than control group (p<0.05). Second, % MVC of right and left erector spinae in all-four positions indicated the statistically significant difference in experimental group which performed diaphragmatic breathing exercise rather than control group (p<0.05). Third, % MVC of right and left erector spinae, external oblique in the sitting position indicated the statistically significant difference in experimental group which performed diaphragmatic breathing exercise rather than control group (p<0.05). Fourth, % MVC of right and left erector spinae, external oblique in the standing position indicated the statistically significant difference in experimental group which performed diaphragmatic breathing exercise rather than control group (p<0.05). Fifth, % MVC of right and left erector spinae, external oblique in the supine position indicated the statistically significant difference in experimental group which performed diaphragmatic breathing exercise rather than control group (p<0.05). Sixth, % MVC of right and left erector spinae, external oblique in the lying on prone position indicated the statistically significant difference in experimental group which performed diaphragmatic breathing exercise rather than control group (p<0.05). In conclusion, as experimental group performed diaphragmatic breathing exercise according to the period of pre-test, post three weeks, and post six weeks, experimental group showed the greater significant effect on the activation of right, left erector spinae, and external oblique muscle. Diaphragmatic breathing exercise which resulted in activation of trunk muscles can be effective for managing the patients with back pain and should be utilized as the new therapeutic intervention.

• Journal of rehabilitation welfare engineering & assistive technology
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• v.11 no.3
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• pp.119-126
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• 2017

In the clinical setting, the pressure bio-feedback device is used for the spinal rehabilitation of patients with back pain, but it has several disadvantages. The purpose of this study was to develop a digitalized pressure biofeedback system that provides precise exercise method and posture in real time during the spinal rehabilitation exercise by sensing and monitoring body movements and balance of users and providing biofeedback to users. After that, the usability testing for a digitalized pressure biofeedback system will be conducted to identify problems such as safety, performance, operability, and satisfaction, and suggest improvement directions. A total of 33 subjects were participated in the usability testing. The experts group and the users group evaluated the developed digitalized pressure biofeedback system on a scale of 5 points after using the equipment. In the user group, safety was 3.59, operability was 4.38, satisfaction was 4.49. In the expert group, safety was 2.86, operability was 3.91, and performance was 4.28. Based on the usability evaluation, if the problems of stability of the cradle for tablet PC, air injection, screen display, etc. are solved, it becomes a exercise device capable of accurately exercising and evaluating the function of the spine by checking its own motion state while the spinal stabilization exercise.

• Journal of the Korean Data and Information Science Society
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• v.20 no.6
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• pp.1061-1073
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• 2009

Stock price index option investing is a scientific investment method and various index and investment strategies have been developed. The purpose of this study is to apply the variety of option investment strategies that have been introduced in the market and validate them using past option trading data. Option data was based on an actual stock exchange market tick data ranging from September 2001 to January 2007. Visual Basic is used to propose an option back-testing model. Validation process was carried out by transferring the tick data into ten-minute intervals and empirically analyzed. Furthermore, most option-related strategies have been applied to the model, and the usefulness of each strategies can be easily evaluated. As option investment has high leverage followed by high risks and profit, the optimal option investment strategy should be used according to the market condition at the time to make stable profit with minimum risk.

• The Korean Journal of Applied Statistics
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• v.19 no.3
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• pp.481-504
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• 2006

VaR, a tail-related risk measure is now widely used as a tool for a measurement and a management of financial risks. For more accurate measurement of VaR, recently we are particularly concerned about the approach based on extreme value theory rather than the traditional method based on the assumption of normal distribution. However, many studies about the approaches using extreme value theory was done only for the univariate case. In this paper, we discuss portfolio risk measurements with modelling multivariate extreme value distributions by combining copulas and extreme value theory. We also discuss the estimation of ES together with VaR as portfolio risk measures. Finally, we investigate the relative superiority of EVT-copula approach than variance-covariance method through the back-testing of an empirical data.

• Korean Journal of Materials Research
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• v.26 no.3
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• pp.154-159
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• 2016

A roll-bonding process was applied to fabricate an AA1050/AZ91/AA1050 laminate complex sheet. Two AA1050 and one AZ91 magnesium sheets of 2 mm thickness, 30 mm width and 200 mm length were stacked up after surface treatment that included degreasing and wire brushing; material was then reduced to a thickness of 3 mm by one-pass cold rolling. The laminate sheet bonded by the rolling was further reduced to 2 mm in thickness by conventional rolling. The rolling was performed at 623K without lubricant using a 2-high mill with a roll diameter of 210 mm. The rolling speed was 15.9 m/min. The AA1050/AZ91/AA1050 laminate complex sheet fabricated by roll bonding was then annealed at 373~573K for 0.5h. The microstructure of the complex sheets was revealed by electron back scatter diffraction (EBSD) measurement; the mechanical properties were investigated by tensile testing and hardness testing. The strength of the complex sheet was found to increase by 11 % and the tensile elongation decreased by 7%, compared to those values of the starting material. In addition, the hardness of the AZ91 Mg region was slightly higher than those of the AA1050 regions. Both AA1050 and AZ91 showed a typical deformation structure in which the grains were elongated in the rolling direction; however, the mis-orientation distribution of grain boundaries varied greatly between the two materials.

• Geomechanics and Engineering
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• v.37 no.4
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• pp.307-321
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• 2024

This paper delves into the critical assessment of predicting sidewall displacement in underground caverns through the application of nine distinct machine learning techniques. The accurate prediction of sidewall displacement is essential for ensuring the structural safety and stability of underground caverns, which are prone to various geological challenges. The dataset utilized in this study comprises a total of 310 data points, each containing 13 relevant parameters extracted from 10 underground cavern projects located in Iran and other regions. To facilitate a comprehensive evaluation, the dataset is evenly divided into training and testing subset. The study employs a diverse array of machine learning models, including recurrent neural network, back-propagation neural network, K-nearest neighbors, normalized and ordinary radial basis function, support vector machine, weight estimation, feed-forward stepwise regression, and fuzzy inference system. These models are leveraged to develop predictive models that can accurately forecast sidewall displacement in underground caverns. The training phase involves utilizing 80% of the dataset (248 data points) to train the models, while the remaining 20% (62 data points) are used for testing and validation purposes. The findings of the study highlight the back-propagation neural network (BPNN) model as the most effective in providing accurate predictions. The BPNN model demonstrates a remarkably high correlation coefficient (R2 = 0.99) and a low error rate (RMSE = 4.27E-05), indicating its superior performance in predicting sidewall displacement in underground caverns. This research contributes valuable insights into the application of machine learning techniques for enhancing the safety and stability of underground structures.

• The Journal of Korean Medicine
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• v.30 no.2
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• pp.104-116
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• 2009

Objectives: This experimental study was designed to show the relationship between kidney qi deficiency and hypoadrenia. A comparative study between Sa-am and local area acupuncture stimulation was conducted. The test results help to show the relationship between kidney qi deficiency and hypoadrenia as well as the recuperation of the patient with the use of VAS, ROM, Sch ber test, ODI and salivary cortisol testing. Methods: 1. Twenty-four adults with chronic low back pain were recruited. Once selected the test population was divided into two different groups. One group was treated only with the use of local area acupuncture and the other with Sa-am acupuncture. 2. At the completion of each acupuncture treatment both groups underwent a VAS, ROM, ODI, $Sch{\ddot{o}}ber$ Test and salivary cortisol test. Results: 1. Both the Sa-am acupuncture group and the local area acupuncture group had statistical significance in VAS decrease and flection ROM increase. 2. Only the Sa-am acupuncture group had statistical significance in extension ROM increase. Only the local area acupuncture group had statistical significance in both lateral flection ROM increase and ODI test. 3. There was statistical significance of correlation between morning salivary cortisol test and adrenal fatigue questionnaire. Conclusions: Both local area acupuncture as well as Sa-am acupuncture treatments were effective for treating lower back pain caused by kidney qi deficiency. In addition, each patients recuperation level can be verified with the results seen from the salivary cortisol test results. The cortisol results suggest a similarity between kidney qi deficiency and hypoadrenia.