• 대한기계학회논문집A
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• 제35권5호
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• pp.555-559
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• 2011

본 연구는 유압 피스톤 펌프 재료로 사용되고 있는 SACM645소재를 사용하여 모재, QT(quenching & tempering) 시험편 및 QT 질화시험편의 피로특성을 조사하였다. 피로특성 조사결과는 다음과 같다. QT 질화시험편은 피로한도가 인장강도의 80%로 나타나 아주 높은 값을 나타내었다. 이것은 시험편 표면에 단단한 질화처리를 실시하여 피로균열의 발생을 지연시켰고, 피로균열이 발생하더라고 소재가 단단하여 균열진전속도가 늦었다고 판단된다. 파면 관찰결과 피로균열진전 영역에서는 모두 스트라이에이션이 관찰되었고, 피로균열진전 이외의 영역에서 QT 시험편은 벽개파괴의 양상을, 모재와 Qt 질화시험편은 딤플 파괴의 양상을 나타내었다.

• 대한방사선기술학회지:방사선기술과학
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• 제14권2호
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• pp.15-21
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• 1991

Experiment was conducted on the image quality and exposure dose following replacement of $CaWO_4$ system screen BH-III and BX-III which have so far been used for high-voltage hard-radiation quality radiography, with rare earth system screen KO750, combined with high contrast film SRH, while additional filter was altered, Cu 0.8 mm+Al 1.4 mm(HVL : Al 8.8 mm), Cu 1.3 mm+Al 1.0 mm(HVL : Al 10.6 mm) and Cu 1.8 mm+Al 1.5 mm(HVL : Al 11.4 mm). AS a result, visual evaluation did not detect extreme changes in image quality under the respective condition(HVL : $Al\;8.8\;mm{\sim}Al\;11.4\;mm$). It was noted, however, that surface exposure dose declined with an increase in the thickness of the additional filter, as it was $18.9\;{\mu}Gy$ at HVL Al 8.8 mm, $17.5\;{\mu}Gy$ at Al 10.6 mm and $15.7\;{\mu}Gy$ at Al 11.4 mm. Considering the limited rating of X-ray equipment and wear of machinery, however, the range of $Cu\;1.3\;mm{\sim}1.8\;mm+Al\;1.0\;mm{\sim}1.5\;mm(1/16\;VL{\sim}1/32\;VL)$ seemed to be a limit.

• The Journal of Advanced Prosthodontics
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• 제8권6호
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• pp.465-471
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• 2016

PURPOSE. The purpose of this study is to evaluate the stability of interface between Co-Cr-Mo (CCM) UCLA abutment and external hex implant. MATERIALS AND METHODS. Sixteen external hex implant fixtures were assigned to two groups (CCM and Gold group) and were embedded in molds using clear acrylic resin. Screw-retained prostheses were constructed using CCM UCLA abutment and Gold UCLA abutment. The external implant fixture and screw-retained prostheses were connected using abutment screws. After the abutments were tightened to 30 Ncm torque, 5 kg thermocyclic functional loading was applied by chewing simulator. A target of $1.0{\times}10^6$cycles was applied. After cyclic loading, removal torque values were recorded using a driving torque tester, and the interface between implant fixture and abutment was evaluated by scanning electronic microscope (SEM). The means and standard deviations (SD) between the CCM and Gold groups were analyzed with independent t-test at the significance level of 0.05. RESULTS. Fractures of crowns, abutments, abutment screws, and fixtures and loosening of abutment screws were not observed after thermocyclic loading. There were no statistically significant differences at the recorded removal torque values between CCM and Gold groups (P>.05). SEM analysis revealed that remarkable wear patterns were observed at the abutment interface only for Gold UCLA abutments. Those patterns were not observed for other specimens. CONCLUSION. Within the limit of this study, CCM UCLA abutment has no statistically significant difference in the stability of interface with external hex implant, compared with Gold UCLA abutment.

• Journal of Information Processing Systems
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• 제15권6호
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• pp.1277-1295
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• 2019

With its technical development, digital printing is being universally introduced to the mass production of clothing factories. At the same time, many fashion platforms have been made for customers' participation using digital printing, and a tool is provided in platforms for customers to make designs. However, there is no sufficient solution in the production stage for automatically converting a customer's design into a file before printing other than designating a square area for the pattern designed by the customer. That is, if 30 different designs come in from customers for one shirt, designers have to do the work of reproducing the design on the clothing pattern in the same location and in the same angle, and this work requires a great deal of manpower. Therefore, it is necessary to develop a technology which can let the customer make the design and, at the same time, reflect it in the clothing pattern. This is defined in relation to the existing clothing pattern with digital printing. This study yields a clothing pattern for digital printing which reflects a customer's design in real time by matching the diagram area where a customer designs on a given clothing model and the area where a standard pattern reflects the customer's actual design information. Designers can substitute the complex mapping operation of programmers with a simple area-matching operation. As there is no limit to clothing designs, the variousfashion design creations of designers and the diverse customizing demands of customers can be satisfied at low cost with high efficiency. This is not restricted to T-shirts or eco-bags but can be applied to all woven wear, including men's, women's, and children's clothing, except knitwear.

• 한국표면공학회지
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• 제50권5호
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• pp.366-372
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• 2017

Plasma electrolytic oxidation(PEO) has attracted attention as a surface treatment which has high wear resistance and corrosion resistance. PEO is generally considered as cost-effective, environmentally friendly and superior in terms of coating performance. Most of studies about the PEO processes have been applied to light metals such as Al and Mg. Because the strength of Al and Mg is weaker than that of steel, there is a limit to the application. In this study, PEO process was used to form oxide coatings on Hot dipped aluminized(HDA) steel and the characteristics of the coating film according to the PEO current density were studied. The morphology was observed by SEM and component was analyzed by using EDS. The corrosion behaviors of PEO coating films were estimated by exposing salt spray test at 5 wt.% NaCl solution and measuring polarization curves in deaerated 3 wt.% NaCl solution. With the increase of PEO process current density, the pore size of the coating surface and the thickness of coating increased. It was confirmed that no Fe component was present on the coating surface. PEO coating films obviously showed good corrosion resistance compared with HDA. It is considered that the PEO coating acts as a barrier to protect the base material from external factors causing corrosion.

• 한국정밀공학회지
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• 제5권1호
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• pp.84-93
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• 1988

The on-line detection of the chip flow is one of the most important technologies in com- pletly automatic operation of machine tool, such as FMS and Unmanned Factories. This problem has been studied by many researchers, however, it is not solved as yet. For the recognition of chip flow in this study, the dynamic cutting force components due to the chip breaking were measured by dynamometer of piezo-electric type, and the frequency components of cutting force were also analyzed. From the measured results, the effect of cutting conditions and tool geometry on the dynamic cutting force component and chip formation were investigated in addition to the relationships between frequency of chip breaking (fB) and side serrated crack (fC) of chip. As a result, the following conclusions were obtaianed. 1) The chip formations have a large effect on the dynamic cutting force components. When chip breaking takes place, the dynamic cutting force component greatly increases, and the peridoic components appear, which correspond to maximum peak- frequency. 2) The crater wear of tool has a good effect on the chip control causing the chiup to be formed as upward-curl shape. In this case, the dymamic cutting force component greatly increases also 3) fB and fC of chip are closely corelated, and fC of chips has a large effect on the change of the situation of chip flow and dynamic cutting force component. 4) Under wide cutting conditions, the limit value (1.0 kgf) of dynamic cutting force component exists between the broken and continuous chips. Accordingly, this value is suitable for recognition of chip flow in on-line control of the cutting process.

• Asian Journal of Atmospheric Environment
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• 제4권2호
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• pp.97-105
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• 2010

A quantitative single particle analytical technique, denoted low-Z particle electron probe X-ray microanalysis (low-Z particle EPMA), was applied to characterize particulate matters collected at two underground subway stations, Jegidong and Yangje stations, in Seoul, Korea. To clearly identify the source of the indoor aerosols in the subway stations, four sets of samples were collected at four different locations within the subway stations: in the tunnel; at the platform; near the ticket office; nearby outdoors. Aerosol samples collected on stages 2 and 3 ($D_p$: $10-2.5\;{\mu}m$ and $2.5-1.0\;{\mu}m$, respectively) in a 3-stage Dekati $PM_{10}$ impactor were investigated. Samples were collected during summertime in 2009. The major chemical species observed in the subway particle samples were Fe-containing, carbonaceous, and soil-derived particles, and secondary aerosols such as nitrates and sulfates. Among them, Fe-containing particles were the most popular. The tunnel samples contained 85-88% of Fe-containing particles, with the abundance of Fe-containing particles decreasing as the distances of sampling locations from the tunnel increased. The Fe-containing subway particles were generated mainly from mechanical wear and friction processes at rail-wheel-brake interfaces. Carbonaceous, soil-derived, and secondary nitrate and/or sulfate particles observed in the underground subway particles likely flowed in from the outdoor environment by human activities and the air-exchange between the subway system and the outdoors. In addition, since the platform screen doors (PSDs) limit air-mixing between the tunnel and the platform, samples collected at the platform at the Yangjae station (with PSDs) showed a marked decrease in the relative abundances of Fe-containing particles compared to the Jegidong station (without PSDs).

• 융합정보논문지
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• 제8권1호
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• pp.131-138
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• 2018

본 연구는 완전 몰입형 가상현실 장비의 사용으로 발생하는 사이버 멀미로 인해 야기된 동적균형의 변화가 낙상을 일으키는지 알아보고자 하였다. 연구의 취지를 이해하고 자발적으로 참여에 동의한 균형감각이 정상인 20대 성인남녀 39명을 대상으로 VR착용 전과 후의 멀미지수, 심박수를 측정하고 Biorescue의 안정성 한계 검사를 실시하였다. 가상현실 체험을 위한 도구로 Samsung gear VR을 이용하였고, To the Homeland 라는 게임을 20분간 실시하였다. VR착용 후 동적균형훈련이 약간 감소하였으나 통계적으로 유의한 차이는 없었다. VR착용 전과 후의 멀미변화는 멀미설문조사를 통해 통계적으로 유의한 차이가 있음을 알 수 있었다. 심박수 변화는 Pulse Oximeter을 이용하여 심박수 증가를 보여 통계적으로 유의한 차이가 있었다. 일반인을 대상으로 완전 몰입형 가상현실 체험은 멀미가 유발되나 동적균형문제에는 다소 영향을 미치지 못하였다. 그렇기 때문에 VR 착용으로 인한 사이버멀미는 균형감소와 낙상을 유발시키지 않는다.

• 한국산업보건학회지
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• 제16권1호
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• pp.36-43
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• 2006

The principal aim of this field study was to determine the concentrations and emissions of gaseous contaminants such as ammonia and hydrogen sulfide in the different types of pig buildings in Korea and allow objective comparison between Korea and the other countries in terms of pig housing types. This field study was performed from May to June and from September to October in 2002. Pig buildings investigated in this research were selected in terms of three criteria; manure removal system, ventilation mode and growth stage of pig. Measurements of concentration and emission of ammonia and hydrogen sulfide in the pig buildings were done in 5 housing types and the visited farms were 15 sites per each housing type. Concentrations of ammonia and hydrogen sulfide were measured at three locations of the central alley in the pig building and emission rates of them were estimated by multiplying the average concentration($mg/m^3$) measured near the air outlet by the mean ventilation rate($m^3/h$) and expressed either per pig of liveweight 75kg(mg/h/pig) or per area($mg/h/m^2$). Concentrations of ammonia and hydrogen sulfide in the pig buildings were averaged to 7.5 ppm and 286.5 ppb and ranged from 0.8 to 21.4 ppm and from 45.8 to 1,235 ppb, respectively. The highest concentrations of ammonia and hydrogen sulfide were found in the mechanically ventilated buildings with slats; 12.1 ppm and 612.8 ppb, while the lowest concentrations of ammonia and hydrogen sulfide were found in the pig buildings with deep-litter bed system(2.2 ppm) and the naturally ventilated pig buildings with manure removal system by scraper(115.2 ppb), respectively(p<0.05). All the pig buildings were investigated not to exceed the threshold limit values(TLVs) of ammonia(25 ppm) and hydrogen sulfide(10 ppm). The mean emissions of ammonia and hydrogen sulfide per pig(75kg in terms of liveweight) and area($m^2$) from pig buildings were 250.2 mg/h/pig and 37.8 mg/h/pig and $336.3mg/h/m^2$ and $50.9mg/h/m^2$, respectively. The pig buildings with deep-litter bed system showed the lowest emissions of ammonia and hydrogen sulfide(p<0.05). However, the emissions of ammonia and hydrogen sulfide from the other pig buildings were not significantly different(p>0.05). Concentrations and emissions of ammonia and hydrogen sulfide were relatively higher in the pig buildings managed with deep-pit manure system with slats and mechanical ventilation mode than the different pig housing types. In order to prevent pig farm workers from adverse health effect caused by exposure to ammonia and hydrogen sulfide in pig buildings, they should wear the respirators during shift and be educated sustainably for the guideline related to occupational safety.

• 한국가스학회지
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• 제4권4호
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• pp.20-24
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• 2000

한국의 Liquid Petroleum Gas 충전소에 있어서 안전관리자의 정전기에 대한 안전 의식을 설문 조사했다. 또한, 위험요소로 판단된 일반 작업복과 순면 작업복의 정전기에 의한 화재 폭발 위험성을 평가했다. 설문 조사에 의하면, 충전소에서는 정전기 예방 측면의 효율적인 교육 및 인식 부족으로 인해 무분별한 작업복을 착용하고 있는 것으로 나타났다. 특히 현재 착용하고 있는 일반 작업복의 경우, 실험에 의한 대전 전하량이 동복 1.79$\mu$C 춘추복 1.44$\mu$C, 하복 1.02$\mu$C로 한국공업규격 (KS K-7807) 에서 정전기 재해 위험 가능성에 대해 언급한 0.60$\mu$C를 크게 상회하여 위험성이 존재했다. 반면. 순면 작업복의 경우는 대전량이 0.52$\mu$C에서 0.42$\mu$C의 범위로 안전한 것으로 나타났다. 따라서, 향후 시각적, 체험적 교육을 병행한 정전기 교육의 질적 향상이 요구되며, 정전기에 의한 재해를 방지하기 위해 착용하는 작업복에 대한 관련 기술 기준의 제정이 요구된다.