• Proceedings of the KSR Conference
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• 2011.05a
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• pp.277-282
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• 2011

Bogie frame is typical safety part of railway vehicle. Total serviceable life of bogie frame will be evaluated by Cumulative Damage Approach Method that is defined by dynamic strain measurement during revenue service under the actual track conditions. As a result of the standardization process developed in British Standard Institution, BS 7608 defines for fatigue design and test method of steel structure by fatigue test results over the long period. This paper evaluates the total serviceable life applying BS 7608 for the bogie frame of Electric Multiple Unit to verify structural safety of the bogie frame.

• Journal of Korean Institute of Industrial Engineers
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• v.36 no.4
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• pp.212-218
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• 2010

This paper shows accuracy comparison results of reliability estimation methods for one-shot systems with respect to sample sizes. To compare accuracy in reliability estimation methods, quantal-response data, characterizing one-shot systems, were simulated using failure times of LED obtained through the accelerated life test, and then the true reliability over time was evaluated using the failure times. The simulated quantal-response data were used to estimate the true reliability through applying reliability estimation methods in open literature. Accuracy of each reliability estimation method was compared in terms of both SSE (Sum of Squared Error) and MSE (Mean Squared Error), and then estimation trend for each method is found. Feasible bounds which true reliability would exist within were estimated through applying the found trends to quantal-response data set of a real weapon system.

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.3
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• pp.122-129
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• 2004

In plastic working, as working becomes speedy, automatic and working condition deteriorates, the increase of forging working has been remarkable. Therefore, we need the estimation of mold lift in detail, in order to counterplan of effective mold life extension. In this study, on the SKH51, mold steel which is forged by cold working and the KCW1, tool steel of low alloy, we estimated mold life on the base of FEM analysis and investigated mold lift by low cycle fatigue test. Also, this paper suggested a new method of estimation of mold lift.

• International Journal of Reliability and Applications
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• v.6 no.1
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• pp.1-12
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• 2005

A new test for testing that a life distribution is exponential against the alternative that it is harmonic new better (worse) than used in expectation upper tail HNBUET (HNWUET), but not exponential is presented based on the highly popular 'Kernel methods' of curve fitting. This new procedure is competitive with old one in the sense of Pitman's asymptotic relative efficiency, easy to compute and does not depend on the choice of either the band width or kernel. It also enjoys good power.

• Journal of the Korean Society of Industry Convergence
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• v.21 no.3
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• pp.141-147
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• 2018

In a time when product development cycles are getting shorter and shorter, many companies are making efforts to develop products with high reliability in a short period of time, accelerated life test is widely used as a method to quickly evaluate reliability. Accelerated life test reduces the test life or the life of the product from the observed data by shortening the lifetime of the product or abruptly lowering the performance under the worse condition than the actual condition in order to shorten the test cost or the test time. In this paper, BL3640A-06P+RB35, DC12V model, which is used in the support device of an automatic rotation type digital signage, which display various information such as textures and images on a display screen in a public place or a commercial space, BLDC motors were subjected to a constant stress test and at the rotational speed of 1rpm, $180^{\circ}$ rotation and reverse rotation under actual use conditions, the stress was imposed on the rotating speed of 2rpm and the weight of the actual installed product from 22.2kgf to 10kgf were installed. The lifetime of the actual use environment condition is 23,545 hours and the rotation speed is accelerated. The life time of the acceleration condition with the additional weight is 1,380 hours. The acceleration factor is calculated as 17.06, the one year guarantee test day is 235 days to 14 days, of the period from 470 days to 28 days, and the third year from 704 days to 42 days. The test date of the BLDC motor was tested on the shortened test date, and the rotational speed and the current value were measured. It is found that there is no defect even if it operates as the test date corresponding to the specified one year warranty period and the 3 year accelerated life test which is experimented. Using the statistical technique of the regression analysis the expected time for the motor to defect to #4 samples was 20 years.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.4
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• pp.44-50
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• 1998

The creep life fraction can be evaluated by the degree of grain deformation since the grain of Cr-Mo base metal deforms in the direction of stress. The grain deformation method using image processing technique is developed for life assessment of in-service high-temperature components. The new assessment model of grain deformation method is presented to apply to in-service components and is verified by interrupted creep test for ex-serviced material of 1Cr-0.5Mo steel. The proposed model, which is irrespective of stress direction, is to evaluate mean of the absolute deviation for the measured ratios which are diametrical maximum to minimum dimensions for grains.

• Journal of Korean Biological Nursing Science
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• v.17 no.2
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• pp.159-168
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• 2015

Purpose: The purpose of this study was to determine the effects of auricular acupressure on menstrual pain, difficulties in daily life, negative feelings and autonomic nervous responses among college students. Methods: A Randomized Controlled Trial design was used. The treatment group A (n=12) receivedauricular acupressure therapy on the first or second day of their menstrual period. Treatment group B (n=18) regularly received an auricular acupressure therapy once a week for a month. The control group (n=19) received no auricular acupressure therapy. An independent t-test was used to examine pre-post test differences in the group. The ANOVA and Scheffe test were used to examine pre-post test differences among the group. Results: Subjects in treatment group A showed significantly less menstrual pain, difficulties in daily life, and negative feelings than the control group did. The participants in treatment group B also showed significantly less difficulties in daily life and negative feelings than the control group. Conclusion: The findings support that auricular acupressure therapy on menstrual periods is effective in controlling menstrual pain, difficulties in daily life, and negative feelings. As the method is simple, it would be useful for female students to learn to use this method to alleviate the symptoms related to menstruation through self care.

• Korean Journal of Child Studies
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• v.22 no.4
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• pp.315-330
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• 2001

The purpose of this study is to research for the educational method developing morality of the preschool children. For this purpose, the embodiment method based on Confucianism was conceptualized and compared with the existing methods of instruction. The research was conducted by dividing into 3 groups such as embodiment group, discussion group and usual group with 161 subjects of 4~5 years old preschool children. Six week program was composed from "Yangjungpyon(養正篇)" and was compared to the curriculum of kindergarten and primary school as the educational content. To measure the effectiveness of the Confucian method, the Test of Basic Life Habituation and Autonomy Rating Scale were used. The result showed that the embodiment group which followed the present method was more effective than the other two groups of existing usual methods in both ages.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 1996.04a
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• pp.262-265
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• 1996

An ALT(accelerated life testing) method is to test a product in over-stressed conditions, and then the test result is extrapolated to an usual (normal stressed) condition. It is the major disadvantage of ALT method that the more extrapolation to an usual condition applies the bigger error is indispensable. Therefore a reliability model combining field failure data and laboratory test data is required in pratice. We propose several methods of estimating the failure rate of a product life which is assumed to follow an exponential distribution. Structural similarity and technological advances are also cosidered. Finally, We derive the acceleratio factor which can be used to predict the failure rate for a new product.

• International Journal of Aeronautical and Space Sciences
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• v.1 no.1
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• pp.92-102
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• 2000

In this study, the 750kW medium scale composite blade for the horizontal axis wind turbine system was designed and manufactured, and it was tested and evaluated by the specific structural test rig. In the test, it was found that local bucklings at the trailing edge of the blade and excessive deflections at the blade tip were happened. In order to solve these problems, the design of blade structure was modified. After improving the design, the abrupt change of deflection at the blade tip was reduced by smooth variation of the spar thickness and the local buckling was removed by extending the web length. The modified design was analyzed by the FEM, the safety and stability of the blade structure. And Fatigue life over 20 years was confirmed by using S-N linear damage method, Spera's method, etc.