In this study, the physical properties and fracture characteristics according to the tensile load are evaluated on the materials of the polymeric filler and carbon fiber-based composite sleeve technique. The polymeric filler and the composite sleeve technique are applied to areas where the pipe body thickness is reduced due to corrosion in large-diameter water pipes. First, the tensile strength of the polymeric filler was 161.48~240.43 kgf/cm2, and the tensile strength of the polyurea polymeric filler was relatively higher than that of the epoxy. However, the tensile strength of the polymeric filler is relatively very low compared to ductile cast iron pipes(4,300 kgf/cm2<) or steel pipes(4,100 kgf/cm2). Second, the tensile strength of glass fiber, which is mainly used in composite sleeves, is 3,887.0 kgf/cm2, and that of carbon fiber is up to 5,922.5 kgf/cm2. The tensile strengths of glass and carbon fiber are higher than ductile cast iron pipe or steel pipe. Third, when reinforcing the hemispherical simulated corrosion shape of the ductile cast iron pipe and the steel pipe with a polymeric filler, there was an effect of increasing the ultimate tensile load by 1.04 to 1.06 times, but the ultimate load was 37.7 to 53.7% compared to the ductile cast iron or steel specimen without corrosion damage. It was found that the effect on the reinforcement of the corrosion damaged part was insignificant. Fourth, the composite sleeve using carbon fiber showed an ultimate load of 1.10(0.61T, 1,821.0 kgf) and 1.02(0.60T, 2,290.7 kgf) times higher than the ductile cast iron pipe(1,657.83 kgf) and steel pipe(2,236.8 kgf), respectively. When using a composite sleeve such as fiber, the corrosion damage part of large-diameter water pipes can be reinforced with same level as the original pipe, and the supply stability can be secured through accident prevention.
In this study, we collect water control valves that have had accidents due to existing cracks, etc. are collected, and propose investigation items for strengthening the valve structural safety evaluation through a series of analyzes from valve specifications to physicochemical properties are proposed. The results of this study are as follows. First, there was a large variation in the thickness of the body or flange of the valves to be investigated, which is considered to be very important factor, because it may affect the safety of the valve body against internal pressure and the flange connected with the bolt nut. Second, 60% of the valves under investigation had many voids in the valve body and flange, etc. and the decrease in thickness due to corrosion was relatively large on the inner surface in contact with water rather than the outer surface. It is judged that the investigation of depth included voids is very important factor. Third, all valves to be investigated are made of gray cast iron foam, and therefore it is judged that there is no major problem in chemical composition. It is judged that the chemical composition should be investigated. Fourth, as a physical investigation item, the analysis of metal morphology structure seems to be a very important factor for nodular cast iron from rather than a gray cast iron foam water valve with a flake structure. As it was found to be 46.7~68.8% of the standard recommended by KS, it could have a direct effect on damage such as cracks, and therefore it is judged that the evaluation of tensile strength is very important in evaluating the safety of the valve.
본 연구에서는, 5가지 식물의 메탄올 추출물을 이용하여 모기기피 효과 실험을 진행하고 누드 쥐를 모델로 하여 흰줄숲모기에 대한 모기기 피제의 유효용량 및 유효시간을 평가하였다. 그리고 식물의 휘발성분을 GC-MS로 분석하였다. 유효용량은 개박하가 10, 50, 100, 200 μg/mL 에서 72.9, 83.7, 86.4, 97.3%의 효율로 가장 높았다. 누드 쥐를 대상으로 한 유효시간 연구에서는 5가지 식물의 메탄올 추출물 중 개박하, 개다 래 및 개똥쑥이 90.5%로, 30분까지만 지속하였다. 각 식물의 휘발성분을 분석한 결과, 애플민트 28개 성분, 개다래 19개 성분, 개똥쑥 27개 성분, 개박하 26개 성분, 민들레 19개 성분이 확인 되었다. 특히 모기기피제의 유효 성분으로 알려진 네페탈락톤(nepetalactone)이 개박하의 휘발성분 중 한 성분으로 확인 되었다(27.95 mg/Kg). 본 연구결과는 다양한 휘발성분을 함유한 식물을 이용한 모기기피제 재료로서 가능성을 제시한다.
3 mol% yttria-doped stabilized zirconia (3YSZ) is synthesized by a solvothermal process, and its characteristics are investigated using various methods. Also, the dispersibility of synthesized 3YSZ nanoparticles is observed with the species of surface modifier. The 3YSZ nano sol prepared with an optimum condition is employed in prism coating and its properties are evaluated. The synthesized 3YSZ nanoparticles show a globular shape with about 10 to 20 nm crystallite size. The mixed phases with the nano sol show a high specific surface of 178 m2/g. The prism sheet coated with the 3YSZ nano sol present an excellent refractive index, transmittance, and luminance; refractive index is 1.603, transmittance is 90.2 %, and luminance of coating film is improved by 5.9 % compared to that of the film without 3YSZ nano sol. It is verified that the surface modified 3YSZ is suitable as the prism sheet for optical displays.
백색을 띄고 물리적·화학적으로 안정한 지르코니아는 열전도도가 낮고 강도와 인성, 내식성이 우수하여 단열재, 내화물과 같은 고온 재료와 각종 산업용 구조세라믹스에 사용되고 있다. 이러한 지르 코니아를 낮은 경도 및 굴절률 등과 같은 단점을 가진 고분자 코팅제에 도입하게 되면 화학적, 전기적, 광학적인 특성이 향상된다. 이와 같이 유기 소재에 무기 소재를 혼합하여 사용하는 유-무기 하이브리드 코팅을 목적으로 본 연구에서는 지르코니아 표면에 trimethylchlorosilane(TMCS)과 hexamethyldisilazane(HMDZ)을 사용하여 실릴화반응을 통한 -CH3기를 도입하여 소수성을 나노지르코 니아 표면에 도입하였다. 소수화된 지르코니아 표면에서의 TMCS와 HMDZ에 의해 도입된 Si-CH3의 존재는 FT-IR ATR spectroscopy를 통해 확인하였고, silicon 원소의 존재를 FE-SEM/EDS와 ICP-AES 를 통해 확인하였다. 또한, 개질 전후의 지르코니아를 아크릴레이트 단량체에 분산하여 침강속도를 확인 하여 분산성이 향상되는 것을 확인하였다. 지르코니아 입자의 크기 및 분포는 입도 분석기를 통해 확인 하였으며, BET 분석을 통해 개질 반응 전후의 비표면적은 18 m2/g 정도로 큰 변화가 없었다.
Currently, national fishery population is aging gradually due to avoiding fishery by young people as they do for farming. The working condition of fishing industry is very poor due to the bad climate, rough wave, worn tools, and narrow working space which cause the uncomfortable postures. These poor working conditions have strong influence on the health and safety of fishermen and cause the work related musculoskeletal disorders (WMSDs). The survey was conducted in this study to investigate the WMSDs symptoms for the fishermen in the coastal fishery. One hundred and twenty five coastal fishermen, especially drift gill net fishermen, participated in this study, and among them 110 responses were analyzed for this study due to the unreliable and insincerity of reponses. The results showed that WMSDs symptoms appeared in various parts of the body such as lower back (84.6%), shoulder (82.7%), and neck (68.2%). The drift gill net fishing require a lot of energy spending and repetitive movement because of the characteristics of the drift gill net fishery and this cause the WMSDs symptoms on back, shoulder, and neck. In this study, WMSDs symptoms of the coastal fishermen were surveyed and related various factors and characteristics were analyzed through ergonomic assessment. The results of this study can provide some basic information to improve the work environment of fishing industry.
The purpose of this study was to investigate the job stress factors that were related to the general characteristics, work characteristics, and health characteristics of the workers at distribution industry. The survey of job stress measurement scale for