• Journal of Advanced Marine Engineering and Technology
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• v.33 no.7
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• pp.1026-1033
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• 2009

Fine ceramics have high strength, excellent wear resistance, chemical stability and high strength at high temperature and are receiving attention in various fields such as construction, engineering, aerospace and marine science. Finish machining process is required to obtain precise ceramics components because sintering process necessary for obtaining high strength and high quality ceramics reduces the dimensions of components and precision of shape. But high strength and brittleness of ceramics materials cause difficulty in processing. So a process for obtaining wanted dimensions is studying using high temperature which makes ceramics softened and thermal affected recently. Laser beam is a very useful optical device for these kinds of processes. Laser process such as laser cutting, laser machining, laser heat treatment and laser-assisted machining(LAM) is researching to manufacture practical ceramics components using intense laser source which can cause local softening and damage of workpiece. In this paper, microstructural and mechanical properties of silicon nitride heated are studied as a basic study for researching of ceramics process by laser beam. The surface variation of HIP and SSN-silicon nitride was analyzed with SEM and EDS. A processing at $1,300^{\circ}C$ or above causes N element to combine into $N_2$ gas and the gas busts from surface. These phenomena make bloat, craters and heat defects on the surface of silicon nitride. Also, oxygen content is largely increased to oxidize the surface and it causes changing of phases and reducing of hardness of surface.

• The Journal of Korean Academy of Prosthodontics
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• v.54 no.2
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• pp.160-166
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• 2016

Although physiologic abrasion in normal range need not to be corrected, when hard tissue of teeth are worn abnormally fast, it can cause severe damage and destroy esthetics and, functional structure of occlusion consequently. To establish a correct occlusal plane and space for the patient with worn dentition, it is necessary to increase vertical dimension. However, actual occlusal vertical dimension remains unhanged with compensation for the increase of alveolar bone height equivalent to the decrease of teeth length. A 74-year-old male presented with worn dentition and fractured tooth. Based on the assessment of OVD including clinical findings, full-mouth rehabilitation without increase of OVD was planned. This case presents that a satisfactory clinical result was achieved by restoring the worn dentition without changing occlusal vertical dimension.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.12
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• pp.15-21
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• 2019

The worm reducer is capable of quadrature power transmission when the shafts are disposed at right angles to each other. Since a large reduction ratio can be obtained of up to approximately 1/100 and a sliding movement is performed during operation compared with other gears, the noise and vibration are small, and there is the advantage that reverse rotation can be prevented. On the other hand, severe wear and damage are displayed on the gear and worm tooth surface, and many defects, such as intense heat generation of the reducer, occur. In the reducer case, the four-piece casing method was selected to solve the problems of heat generation, transmission efficiency, and assemblability. In this paper, we analyzed the problems of the worm and worm wheel (the core parts of a 5-Ton worm reducer) and casing through these methods and researched how to solve them.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.4
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• pp.268-275
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• 2020

In domestic mountain resort areas, a catenary system cannot be installed for the protection of the natural environment and view. Therefore, mountain trams must be operated wireless. In this study, a local ground pantograph, which supplies electricity to the battery on board, was developed for this purpose, and its performance was verified by tests. The system is installed on ground at stops or repair shops. While a bogie goes to the pantograph, the arms and collection shoes are raised by a spring force to make contact with the collection bar under the bogie so electric power can be supplied to the battery. Because it is a local ground type, it does not require a roof pantograph and catenary system. The system enables the mountain tram to run wireless. In addition, there is no separation and arc because it collects current while standing at stops or shops. The system has a long life because moving contact, which generates wear and damage to shoes, is avoided. The insulation resistance was above the criteria of 10 ㏁, and there was no abnormal temperature increase when a current of 335A was supplied for one hour.

• Journal of Fashion Business
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• v.19 no.4
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• pp.92-108
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• 2015

This study aimed at developing a down jacket prototype that utilized sunlight as an alternative energy source with no air pollution. The jacket is filled with flexible solar panels and has a heat-generating function and LED function. In this study, three smart down jacket prototypes were developed, and the jacket's capabilities were demonstrated through the thermal effect on the performance test. The typical output voltage of the flexible solar panels was 6.4V. By connecting the 2 solar cell modules in series, the final output voltage was 12.8V. A battery charge regulator module was used the KA 7809 (TO-220) of 9V. Three heating pads were to be inserted into the belly of the jacket as direct thermal heating elements, and the LED module was configured, separated by a flash and an indicator. The smart down jacket was designed to prevent damage to the down pack without the individual devices' interfering with the human body's motion. Because this study provides insulation from extreme cold with a purpose, the jacket was tested for heat insulation properties of non-heating, heating on the back, heating on the abdomen, and heating on both the back and abdomen in a sitting posture in a static state. Thermal property analysis results from examining the average skin temperature, core temperature, and the temperature and humidity within clothing showed, that placing a heating element in one place was more effective than distributing the heating elements in different locations. Heating on the back was the most effective for maintaining optimal skin temperature, core temperature, and humidity, whereas heating on the abdomen was not effective for maintaining optimal skin temperature, core temperature, or humidity within clothing because of the gap between the jacket and the body.

• 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.

• The Research Journal of the Costume Culture
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• v.22 no.2
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• pp.290-299
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• 2014

This research sought to analyze the characteristics of breast movement at the treadmill activity levels. It also examined the effect of wearing a sports bra in reducing breast displacement. The subjects for the data collection were females in their 20s (n=2) with C-cup size breast. The experimental conditions were three different moving speeds (4 km/h, jogging: 7 km/h, and sprinting: 10 km/h) and two types of sports bras. Three dimensional breast displacement was measured. The displacement of the right nipple point was measured with a 3D motion analyzer. The results show that the breasts were greatly displaced from the walking speed (4 km/h) when subjects did not wear any bra. Whereas their breast displacement distance decreased remarkably when they wore sports bras. The nipple point moved 42~44 mm in the vertical direction at walking speed with naked condition. But it was reduced by 80% after wearing sports bras. When subjects running (7 km/h, 10 km/h) without any bra, the nipple point moved 122~141 mm. However it was reduced by 60~70% when they wore sports bras. The apartment time (time delay) between at the highest point of the upper body and the nipple was 0.25 seconds at the running speeds (7 km/h, 10 km/h) without wearing any bra. After wearing sports bras, the time delay was cut to 0.06~0.12 seconds. These results implies that without wearing any bra the skin surrounding the breasts might be seriously pulled at running activity. The functional sports bra suppress breast movement. It might prevent the sagging of breasts by preventing the damage of the Cooper's ligaments.

• Journal of Welding and Joining
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• v.26 no.4
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• pp.85-91
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• 2008

The grooving corrosion is caused mainly by the different microstructures between the matrix and weld which is formed during the rapid heating and cooling cycle in welding. By this localized corrosion reaction of pipes, it evolves economic problems such as the early damage of industrial facilities and pipe lines of apartment, and water pollution. So lots of researches were carried out already about grooving corrosion mechanism of ERW carbon steel pipe but there is seldom study for water hammer happened by fluid phenomenon and corrosion rate by flow velocity. In this study, the analysis based on hydrodynamic and fracture mechanics was carried out. ANSYS, FLUENT and STAR-CD were used for confirmation of flow phenomenon and stress on the pipe. As the results, fatigue failure is able to be happened by water hammer and grooving corrosion rate is increased cause by turbulent. Grooving corrosion is happened on the pipe, then friction loss of fluid is occurred from corroded part. Erosion can be happened enough in corroded region of microscopic size that wear "V" form. Also pipe is able to be damaged by water hammer effects because of corroded region is general acting as a notch effects. Corrosion depth was more than half of total thickness, it can be damaged from water hammer pressure.

• Fashion & Textile Research Journal
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• v.21 no.4
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• pp.497-508
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• 2019

Snowboarder accidents at ski resorts are increasing; therefore, it is essential to wear protective wrist, hip and knee protectors when snowboarding. However, most studies focus on the improvement of gear or expansion of safety facilities with few studies on protectors that directly safeguard the body from accidents caused by tumbling. Protectors currently on the market do not properly consider the needs of the users. Therefore, this study investigates the reality of usage and satisfaction rate of those that use snowboarding protectors along with factors deemed important upon wearing them to provide the grounds for the development of comfortable protectors. Subjects were 1,058 adults in their 20s to 40s. First, a survey was conducted regarding demographic traits as well as the wearing and purchasing of protectors. Second, 325 people that purchased and wore protectors were investigated in regards to the wearing satisfaction rate of current commercial protectors. The results showed that 86% of the 1,058 subjects wore protectors; knee protectors (72%), hip protectors (57%) and wrist protectors (38%). Important factors upon purchasing and wearing satisfaction were studied according to demographic traits, snowboarding experience, and number of snowboard rides for one season. As a result, the damage rate increased along with the number of snowboard rides for one season. Important factors considered when purchasing varied significantly according to sex, age, snowboarding experience, and favored slopes. The results of this study will help in the design of comfortable protectors for snowboarders.

• Journal of the Korean Society of Industry Convergence
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• v.25 no.6_2
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• pp.1119-1125
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• 2022

The depletion of resources and waste disposal caused by the continuous development of industry have emphasized the need to reduce consumption and production, recycle and reuse, and the importance of remanufacturing has increased in recent years. The spindle part of the aging planner miller, which is currently being remanufactured, is one of the factors that has the greatest impact on the performance of the machine tool. When designing the spindle part of the spindle shaft, there are considerations such as the configuration size bearing performance of the main shaft, but the diameter of the main shaft, the dangerous speed bearing, and the arrangement that affect the machining accuracy should be basically considered. As such, various studies have been conducted on the design of machine tool spindle spindles, but research on the reverse engineering of existing aging machine tool spindle spindles is poor. Reverse engineering is designing in the direction of improving performance by extracting specifications from already finished products, and first scanning the reverse engineered object through a 3D scanner, 3D modeling is performed based on the collected data, and then the process of deriving improvement plans by reverberating to improve performance by identifying wear and damage conditions is followed. Therefore, in this study, the purpose of this study is to provide data on reverse engineering by deriving improvement plans through optimal design for the bearing position of the aging planar Miller spindle spindle using central composite programming.