• Journal of the Korean Society for Precision Engineering
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• v.28 no.5
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• pp.537-542
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• 2011

The thermo-mechanical interaction between brake block and wheel tread during braking has been found to cause thermal crack on the wheel tread. Due to thermal expansion of the rim material, the thermal cracks will protrude from the wheel tread and be more exposed to wear during the wheel/block contact than the rest of the tread surface. The wheel rim is in residual compression stress when is new. After service running, the region in the tread has reversed to tension. This condition can lead to the formation and growth of thermal cracks in the rim which can ultimately lead to premature failure of wheel. In the present paper, the thermal cracks of railway wheel, one of severe damages on the wheel tread, were evaluated to understand the safety of railway wheel in running condition. The residual stresses for damaged wheel which are applied to tread brake are investigated. Mainly X-ray diffusion method is used. Under the condition of concurrent loading of continuous rolling contact with rails and cyclic frictional heat from brake blocks, the reduction of residual stress is found to correlate well with the thermal crack initiation.

• Journal of Korean Physical Therapy Science
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• v.20 no.1
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• pp.17-25
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• 2013

The purpose of this research is to provide right information about deformation and to relieve fatigue of high-heels lovers. The research data includes 15 tests and survey on 71 female students. The result follows 1. Age of surveys is mostly 22, consisting 43.7% of all. The most frequently worn shoe kind is high heels that 45.1% of surveys wear 2. Female students those are 155~160cm high wear high heels most frequently, 40.8%. 3. The fatigue condition classified by hours of wearing: Surveys wearing high heels over 7 hours and 5~7 hours state starting to feel fatigue by 40.8%, 38.0% each, and the result was stastically significant 4. The appearance of pain on calf classified by hours of wearing: 35.2% of surveys answered they start to feel pain when worn high heels over 7 hours, and 33.8% of students answered 5~7 hours 5. The fatigue condition classified by kinds of shoes worn: 45.0% of the surveys felt tired when wearing high heels, 40.8% answered wearing heel inserted running shoes, and 14.0% for flat shoes. 6. The fatigue condition classified by heel height: 69.0% of survey answered they feel fatigue after wearing shoes with 5~9cm high heels, 21.1% answered under 3cm high heels, and 9.9% answered over 10cm heels(p<0.05) 7. The experience of cramp in calf cramp muscle classified by heel height: 69.0% of surveys experienced cramp when wearing 5~9cm high heels, 21.1% answered under 3cm high heels, 9.9% for over 10cm heels.

• Tribology and Lubricants
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• v.23 no.6
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• pp.306-311
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• 2007

This paper presents the friction characteristics of pb-fres pin bushing bearings for an automotive gasoline engine. The external load is 100 N to 600 N and the speed of the pin bushing bearing is 1000 rpm to 3000 rpm against the rubbing surfaces. And the contact modes of rubbing surfaces between a piston pin and a pb-free pin bushing specimen are a dry friction, an oil lubricated friction and a mixed friction that is starved by a lack of engine oil. Two influential factors of a contact rubbing modes and a material property are very important parameters on the tribological performance of a friction characteristic between a piston pin and a pb-free pin bushing. The experimental result shows that the pin bushing speed of 2000 rpm shows a typical oil film lubricated sliding contact mode in which means that as the applied load is increased, the friction loss is increasing. But other contact mode depending on the speed and the load may affect to the fiction coefficient without a regular and uniform trend. In summary, the oil lubricated rubbing surface definitely decreases a running-in period in short and increase oil film stiffness, and this may leads the reduction of a friction loss.

• The Research Journal of the Costume Culture
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• v.20 no.4
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• pp.549-559
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• 2012

The purpose of this study was to analyze the comfort of sports bras by style and bra cup size. The comfort of wear was measured with compression level. The displacement of breast points (BP) after wearing a sports bra was measured. Study subjects evaluated the comfort level of the compression type and encapsulation type sports bras after walking and running. The results showed that all types of experimental sports bras provided more coverage than everyday bras. The compression type bra placed more pressure on the breast, chest, and under-bust than the encapsulation type bra. The BP distance decreased for all types. The C cup subjects' breasts were raised after wearing the sports bras. The B cup subjects had less comfort with the compression style bra than C cup subjects. The racer back style bra with high neckline and small band girth placed more pressure than others. They were difficult to don and doff and the least comfortable. These results imply that the racer back compression style sports bra was uncomfortable for women with large breast, while the encapsulation style bra with the compressing panel at upper chest was the most comfortable. The bras that shortened BP distance placed more pressure on the breast. But the bra that raised and shorted the distance of BP provided better comfort for large-breasted subjects.

• Journal of Advanced Marine Engineering and Technology
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• v.31 no.3
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• pp.215-223
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• 2007

When the propulsion shafting system of marine diesel engine is designed. the vibratory stresses on shafts should be reviewed and be satisfied with limits which are laid down by classification societies In addition. the torsional vibration aspects for crankshaft of main engine are requested to be checked by engine designers. Especially. for the 4, 5, and 6-cylinder engines. the 2nd order moment compensator(s) may be installed to compensate the external moments of engine and not to excite the hull girder vibration. This moment compensator which is mounted on fore and/or after-end of engine is driven by the roller chain drive for some of MAN 2-stroke diesel engines. While the engine is running, the roller chain Is worn down, which causes the extension of roller chain. The chain therefore should be checked and tightened by periods in order to keep its functionality. However. when the torsional angular acceleration of chain drive exceeds the certain limit. the chain will suffer the excessive slack and transverse vibration. This may cause fatigue, wear or damage on the chain and the chain ultimately may be broken. The research object of this thesis is to review factors which affect the angular acceleration of chain drive and to find out how to decrease the angular acceleration of driving chain by checking factors which have a major contribution to acceleration reduction using the statistical method of DOE(design of experiment), correlation analysis and regression analysis methods.

• Journal of the Korean Society of Clothing and Textiles
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• v.41 no.5
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• pp.883-900
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• 2017

This study provides basic reference data to develop sports brassieres appropriate for women in their forties and fifties. The study focused on analyzing the exercise status, brassiere-wearing conditions, purchase conditions, preferred design and functionality by age as well as exercise strength based on 393 questionnaires. Middle-aged women favorite exercises included running, yoga and golfing; in addition the most important purpose to exercises was healthcare. The largest number of respondents exercised once to three times a week for 3 years or longer. The analysis on sports brassiere-wearing conditions by exercise strength showed that those who favor intense exercise tended to wear sports brassieres more frequently. In addition, many complained about breast-shaking and an unsatisfactory shape when they wore a sports brassiere. The analysis on purchase conditions showed that increased interest in intense sports led to more use of specialized sports shops. The analysis of the design and functionality preference showed that increased interest in intense sports increased interest in a body-wrapping sports brassiere design. The most frequently required functions also included the prevention of breast-shaking and a fixed brassiere-position.

• Journal of the korean Society of Automotive Engineers
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• v.15 no.2
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• pp.130-143
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• 1993

Engineering ceramics have some excellent properties as the material for the mechanical components. It is, however, very difficult to grind ceramics with high efficiency because of their high strength, hardness and brittleness. In this paper, experiments are carried out to obtain the effect of "In-process dressing" to grind the Engineering ceramics with high efficiency. To save running time for dressing process and obtain restraint effect of diamond grain wear, "In-process dressing" system using WA stick type honing stone is proposed. Representative Engineering ceramics, such as AI$_{2}$O$_{3}$, Si$_{3}$N$_{4}$, are ground with diamond wheel. Also bending strength test is carried out to check upward tendancy of mecahnical properties as the result of machining defact restraint through the grinding machining method using "In-process dressing" process. Some results obtained in this study provide useful information to attain the high efficiency grinding and the high mechanical properties of Engineering ceramics.rties of Engineering ceramics.

• Journal of Biosystems Engineering
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• v.40 no.2
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• pp.95-101
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• 2015

Purpose: During the start-up period, the response time of a hydraulic system increases in the winter because of the increased oil viscosity caused by the cold weather. The problems of delayed tractor starting and excessive wear of the clutch disk occur for these reasons. Therefore, this study develops an analysis model using the commercial hydraulic analysis program AMESim to examine the characteristics of delays in power shuttle starting at different oil temperatures. Methods: In the experiment, a tractor was stationary on a flat surface with the engine running at a constant speed of 1,080 rpm. The forward lever was then pressed to activate the power shuttle at three different oil temperatures, and the pressure changes were measured. The pressure on the forward clutch control valve was measured by a pressure gauge installed on the hydraulic line supplied to the transmission from the main valve. An analysis model was also developed and verified with actual tests. Results: The trend of the simulated pressures of the power shuttle is similar to that of the measured pressures, and a constant modulation period was observed in both the simulation and test results. However, the difference found between the simulation and test results was the initial pressure required to overcome the initial force of the clutch spring. Conclusions: This study also examines the characteristics of the delayed startup of the power shuttle at different oil temperatures through simulations.

• Journal of the Korean Society for Railway
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• v.15 no.3
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• pp.224-230
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• 2012

The wearing slider of the rail motor car's pantograph is considerable changed by the type and the material properties. Especially, precipitation and arc influences are main factors decided to life time of wearing slider and contact wire. This study is wearing phenomenon analysis of Cu-type wearing slider with high electric conductivity and resistance arc through experiment by running train. Author observed that wearing phenomenon of Cu-type wearing slider with normal and abnormal wearing characteristics and comparatively analysis precipitation, mileage and weight influences of exchanged Cutype and Fe-type wearing sliders. In this paper result showed that necessity for the application which is the Fe-type of wearing slider had superior wear resisting capacity etc., through tribology approach.

• Proceedings of the KSR Conference
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• 2009.05b
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• pp.225-230
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• 2009

From the view point of railway vehicle dynamics, the interaction between wheel and rail have an huge effect on the behavior of the vehicle. This phenomenon is an unique motion, only for railway vehicles. Furthermore, close investigation of the backgrounds of the interaction is the key to estimate the dynamic behavior of the vehicle, successfully. To evaluate the model including flexible bodies such as car body and catenary system of the next generation express train, it is necessary to develop proper dynamic solver including a wheel rail contact module. In this study, wheel-rail contact module is developed using the general purpose dynamic solver. First of all, the procedure for calculation of the wheel-rail contact force has been established. Generally, yaw angle of the wheelset is ignored. Sets of information are summarized as tables and splined for further uses. With this information, normal force and creep coefficient can be extracted and used for FASTSIM algorithm, which has been shown good reliability over years. Normal force and longitudinal, lateral force at the contact surface are also calculated. Those data are verified by commercial railway simulation program 'VAMPIRE'. This procedure and program can offer a basic process for estimation of the dynamic behavior and wear of the wheel-rail system, even while running on the curved rail. Finally, multi-dimensional inspection tool will be developed including the prediction of the derailment.