• 한국의류산업학회지
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• 제17권4호
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• pp.646-656
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• 2015

This study investigates the conditions of Korean naval duty and combat uniforms to develop a new design. Survey participants consisted of, 723 Sailors ($25.3{\pm}6.9yr$ in age, $43{\pm}53$ months in work experience, $174{\pm}6cm$ in height, $71{\pm}9kg$ in body mass) serving in the Korean Navy for over 12 months. The questionnaire consisted of 72 questions about anthropometric characteristics, preferred design, textiles, wear mobility, and subjective perceptions. The results showed that the preferred colors for future naval duty uniforms were blue in summer (69%) and black in winter (62%). Digital camouflage pattern (60%) and darker colors on the inside of shirt collar (87%) and the edge of sleeves (84%) were preferred. They favored more than one pocket on the upper arm and chest of the shirts (58%), narrower width around pant legs and hems than the current clothing (63%), self-controlled elastic waist (55%) and no cargo type pocket on the pants (45%). There were requirements to alleviate excessive heat stress in summer and to protect from the cold and wind in winter. Wrinkle-free (85%), anti-bacterial (78%), water-proof (75%), oil-proof (90%), and elastic (67%) textiles were preferred for Korean navy uniforms. These results will be applied to develop the next generation Korean navy uniforms.

• 한국음향학회지
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• 제8권1호
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• pp.5-12
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• 1989

RMS, Kurtosis, Crest factor, Probability of exceedance와 Probability density function 등의 통계적 파라미터를 선정하여 베어링의 사용조건과 결함진전에 따른 변화특성을 조사하였다. 이를 위해 4볼 시험기에서 하중, 회전수 및 시간을 변화시키면서 실험하여 진동신호를 수집하고, 이를 A/D변환시킨 후 디지털 필터링하여 주파수 대역별 통계적 파라미터 값을 계산하였다. 실험결과, 하중이나 회전수와 같은 운전조건이 변화하는 경우 RMS의 값은 운전조건 변화에 따라 변하지만 Kurtosis 등의 통계적 파라미터들은 운전조건과 무관하게 steady한 결과를 나타내었다. 또한 통계적 파라미터와 시간과의 상관관계에 대한 실험으로부터 통계적 파라미터들을 결함의 진전 상태를 나타내는 파라미터로 사용할 수 있음을 확인하였으며, 따라서 파손방지를 위한 예측지표로서 이들 통계적 파라미터를 이용할 수 있을것으로 판단되었다.

• The Journal of Advanced Prosthodontics
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• 제10권2호
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• pp.93-100
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• 2018

PURPOSE. The purpose of this study was to determine the changing frequency of a diamond bur after multiple usages on 3 different surfaces. MATERIALS AND METHODS. Human premolar teeth (N = 26), disc shaped direct metal laser sintered CoCr (N = 3) and zirconia specimens (N = 3) were used in this study. Groups named basically as Group T for teeth, Group M for CoCr, and Group Z for zirconia. Round tapered black-band diamond bur was used. The specimens were randomly divided into three groups and placed with a special assembly onto the surveyor. 1, 5, and 10 preparation protocols were performed to the first, second, and third sub-groups, respectively. The subgroups were named according to preparation numbers (1, 5, 10). The mentioned bur of each group was then used at another horizontal preparation on a new tooth sample. The same procedure was used for CoCr and zirconia disc specimens. All of the bur surfaces were evaluated using roughness analysis. Then, horizontal tooth preparation surfaces were examined under both stereomicroscope and SEM. The depth maps of tooth surfaces were also obtained from digital stereomicroscopic images. The results were statistically analyzed using One-Way ANOVA, and the Tukey HSD post-hoc tests (${\alpha}=.05$). RESULTS. All of the groups were significantly different from the control group (P<.001). There was no significant difference between groups Z5 and Z10 (P=.928). Significant differences were found among groups T5, M5, and Z5 (P<.001). CONCLUSION. Diamond burs wear after multiple use and they should be changed after 5 teeth preparations at most. A diamond bur should not be used for teeth preparation after try-in procedures of metal or zirconia substructures.

• 대한치과보철학회지
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• 제58권1호
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• pp.67-76
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• 2020

컴퓨터 지원 설계 제조 기술(CAD/CAM)의 발전에 따라, 완전한 디지털 워크플로우를 구현하기 위한 첫번째 단계인 구내스캐너의 중요성이 높아지기 시작했다. CAD/CAM 이중스캔 기술은 임시 수복물의 외형을 복제하여 최종 수복물에 반영하도록 하는 방법이다. 이 증례에서는 비심미적인 전치부, 중증도의 마모, 수직 고경의 감소를 보이는 67세 남성을 치관 연장술과 수직고경 회복을 동반한 완전구강회복을 통해 치료했다. 임시 수복물은 구내스캐너와 CAD/CAM 이중스캔을 이용해 제작되었다. 적응 기간 후, 최종 단일 구조 지르코니아 수복물을 CAD/CAM 이중스캔을 이용해 임시 수복물을 반영해 제작되었다.

• 한국운동역학회지
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• 제27권4호
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• pp.239-245
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• 2017

Objective: The bobsleigh shoes used in the start section are one of the most important equipment for improving the competition. Despite the importance of the start section, there are no shoes that are specific for bobsleigh athletes in Korea and Korean athletes have to wear sprint spike shoes and practice the start instead of wearing bobsleigh shoes. The objective of the present study was to provide data for improving the performance of Korean bobsleigh athletes by investigating the differences in their split time, plantar pressure, and forefoot bending angle based on skill levels at the start of a run under the same conditions as training conditions. Method: Six Korean bobsleigh athletes were divided into two groups, superior (n=3) and non-superior (n=3). A digital speedometer measured the split time at the start; the Pedar-X system (Novel, Germany) measured plantar pressure. Plantar pressures and split times were measured as the athletes pushed a bobsleigh and sprinted at full speed from the start line to the 10-m mark on the bobsleigh track. An ultra-high-speed camera was used to measure the forefoot bending angle during the start phase. Results: Significant between-group differences were found in split times (p<.000; superior = 2.38 s, non-superior = 2.52 s). The superior group had a larger rearfoot (p<.05) contact area, maximum rearfoot force (p<.01), and a larger change in angles 3 and 4 (p<.05). Conclusion: At the start of a bobsleigh run, proper use of the rearfoot for achieving effective driving force and increasing frictional resistance through a wider frictional force can shorten start time.

• 한국의류학회지
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• 제41권4호
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• pp.722-740
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• 2017

This study was conducted to offer basic data that can be used in a clothing industry for active senior males that are emerging as a new consumer bracket in a rapid aging age. To this end, this study conducted an analysis of 'younger' older male body types based on data from the 6th Size Korea. As a result of the body type analysis of 'younger' older males who are considered active seniors in comparison to 'middle' aged males, the former's height items became shorter compared to 'middle' aged males, but circumference items were bigger. Males aged 35-69, who are 'middle' aged males and 'younger' old males were divided into three body types in this study: Type1- small body type with protruded belly, compared to weight. Type 2- body type of slim torso with wide shoulder-back widths. Type3- big body type overall with tall height and heavy weight. According to body type distribution by age group, the middle-aged males had Type2 body type the most. The younger-old males showed type1 the most. There is a need to reflect the body types of active senior male characteristics in apparel pattern design because the current fits are not appropriate if active senior males wear clothing targeted for males aged 30-50.

• 대한치과보철학회지
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• 제45권6호
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• pp.769-779
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• 2007

Statement of problem. When TiN coating is applied to the abutment screw, occurrence of greater preload and prevention of the screw loosening could be expected due to decrease of frictional resistance. However, the proper thickness of TiN coating on abutment screw has not been yet reported. Purpose. The purpose of this study is to find out the appropriate TiN coating thickness by evaluating the detorque force and the surface change of titanium abutment screw with various TiN coating thickness. Material and methods. 1. Material Thirty five non-coated abutment screws were prepared for TiN coating. TiN coatings were prepared by Arc ion plating method. Depending on the coating deposition time(CDT), experimental groups were divided into 6 groups(CDT 30min, 60min, 90min, 120min, 150min, 180min) and those of 1 group was not coated as a control group. Each group was made up of 5 abutment screws. 2. Methods FE-SEM(Field Emission Scanning Electron Microscoper) and EDX(Energy Dispersive X-ray Spectroscopy) were used to observe the surface of the abutment screw. Electric scales was used to measure the weight of the abutment screw after the repeated closing and opening of 10 trials. Detorque force was measured with digital torque gauge, at each trial. Results. 1. As the coating deposition time increased, the surface became more consistent and smooth. 2. As for the abutment screws that were TiN coated for more than 60 minutes, no surface change was found after the repeated closing and opening. 3. The TiN coated abutment screws showed less weight change than the non-coated abutment screws. 4. The TiN coated abutment screws showed higher mean detorque force than the noncoated abutment screws. 5. The abutment screw coated for 60 minutes showed the highest mean detorque force. Conclusion. The coating layer of proper thickness is demanded to obtain consistent and smooth coating surface, resistance to wear, and increased detorque force of the abutment screw. In conclusion, the coating deposition time of 60 minutes indicated improved mechanical property, when TiN coating was conducted on titanium abutment screw.

• Journal of Computational Design and Engineering
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• 제1권1호
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• pp.27-36
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• 2014

Similar to the essential components of many mechanical systems, the geometrical properties of the teeth of spiral bevel gears greatly influence the kinematic and dynamic behaviors of mechanical systems. Logarithmic spiral bevel gears show a unique advantage in transmission due to their constant spiral angle property. However, a mathematical model suitable for accurate digital modeling, differential geometrical characteristics, and related contact analysis methods for tooth surfaces have not been deeply investigated, since such gears are not convenient in traditional cutting manufacturing in the gear industry. Accurate mathematical modeling of the tooth surface geometry for logarithmic spiral bevel gears is developed in this study, based on the basic gearing kinematics and spherical involute geometry along with the tangent planes geometry; actually, the tooth surface is a parametric surface defined on a parallelogrammic domain. Equivalence proof of the tooth surface geometry is then given in order to greatly simplify the mathematical model. As major factors affecting the lubrication, surface fatigue, contact stress, wear, and manufacturability of gear teeth, the differential geometrical characteristics of the tooth surface are summarized using classical fundamental forms. By using the geometrical properties mentioned, manufacturability (and its limitation in logarithmic spiral bevel gears) is analyzed using precision forging and multiaxis freeform milling, rather than classical cradle-type machine tool based milling or hobbing. Geometry and manufacturability analysis results show that logarithmic spiral gears have many application advantages, but many urgent issues such as contact tooth analysis for precision plastic forming and multiaxis freeform milling also need to be solved in a further study.

• Tribology and Lubricants
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• 제35권5호
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• pp.274-285
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• 2019

Chemical mechanical polishing (CMP), which is a material removal process involving chemical surface reactions and mechanical abrasive action, is an essential manufacturing process for obtaining high-quality semiconductor surfaces with ultrahigh precision features. Recent rapid growth in the industries of digital devices and semiconductors has accelerated the demands for processing of various substrate and film materials. In addition, to solve many issues and challenges related to high integration such as micro-defects, non-uniformity, and post-process cleaning, it has become increasingly necessary to approach and understand the processing mechanisms for various substrate materials and abrasive particle behaviors from a tribological point of view. Based on these backgrounds, we review recent CMP R&D trends in this study. We examine experimental and analytical studies with a focus on substrate materials and abrasive particles. For the reduction of micro-scratch generation, understanding the correlation between friction and the generation mechanism by abrasive particle behaviors is critical. Furthermore, the contact stiffness at the wafer-particle (slurry)-pad interface should be carefully considered. Regarding substrate materials, recent research trends and technologies have been introduced that focus on sapphire (${\alpha}$-alumina, $Al_2O_3$), silicon carbide (SiC), and gallium nitride (GaN), which are used for organic light emitting devices. High-speed processing technology that does not generate surface defects should be developed for low-cost production of various substrates. For this purpose, effective methods for reducing and removing surface residues and deformed layers should be explored through tribological approaches. Finally, we present future challenges and issues related to the CMP process from a tribological perspective.

• 한국의상디자인학회지
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• 제23권4호
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• pp.57-71
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• 2021

The purpose of the study is to derive an appropriate knitting method that can increase the appearance, wearability, and functionality through empirical research on the sleeve height knitting ratio of seamless knit wear. The study was conducted by producing seven types of experiment clothes according to knitting ratio to examine the characteristics according to the body armhole and sleeve height ratio. Specifically, after fit evaluatins, variance analysis (ANOVA) was performed to analyze the results of the evaluation, and the evaluated contents were converted into data. Among them, the items with significant results were intensively studied using the Duncan-test. The result showed that the height and the width of the sleeves vary depending on the knitting ratio. Test sweater A was the highest at 16cm, followed by test sweater B, test sweater C, test sweater D, test sweater E, test sweater F, and test sweater G at 4cm. The 1:1 ratio of test sweater A, was the highest, which is knitted in the same course as the body. The larger the difference in the ratio of body and sleeve, the lower the height of the sleeves. As a result of the appearance sensory evaluation, a significant difference was confirmed in the result values (p<0.001) from all items on the front, side, and rear. Specifically, the appearance of the test sweater B(2:4:2) on the front and test sweater C(2:4:3) on the side and rear side was the best. When the sleeves height is properly set, the ratio of the arm line to fit the design with a natural curve is analyzed as a very important factor. The results of this study are expected to be of practical use in product development and production that can increase the feeling when wearing and design satisfaction.