• 한국안전학회지
• /
• 제8권2호
• /
• pp.16-22
• /
• 1993

Accidents, especially fatal accidents in construction work are being not reduced, but increased, despite of more concerns of related authority and companies themselves. It is investigated that major reasons of which these accident increase are caused to set up wrong temporary structures : scaffolding with insufficient components or safety guards. Approximately 50% of falling accident, one of three major accidents； falling collapsing of structures or soil, accidents from heavy equipments, are due to defects of temporary structures. Therefore, technical standards for these temporary structures made by the ministry of labour in 1984, should be promptly revised because of its insufficient considerations for structural concepts. A method to effectively ensure the construction safety are shown through an experimental method, mathematical analysis structural planning against overturning and collapsing of scaffold-ing components, consideration of safety factor in loading, formulations of safety structure against falling or dropping from schaffolding.

• 소성∙가공
• /
• 제19권2호
• /
• pp.88-94
• /
• 2010

The next generation of diesel engine can operate at high injection pressure up to 1,800bar. The common rail pipe must have higher internal strength because it is directly influenced by the high-pressure fuel. Folding defects in the Common rail pipe can not ensure the structural safety. Therefore, Preform design and fatigue-life analysis are very important for preventing the head of the common rail pipe from folding in the heading process and for predicting fatigue life according to the amount of folding. In this study, a closed form equation to predict fatigue life was suggested by Goodman theory and pressure vessels theory in ASME Code in order to develop an optimization technique of the heading process and verified its reliability through fatigue-structural coupled field analysis. The results calculated by the theory were in good agreement with those obtained by the finite element analysis.

• Advances in nano research
• /
• 제4권1호
• /
• pp.45-50
• /
• 2016

Data of Raman spectroscopy from graphene and few-layer graphene (FLG) irradiated by SEM electron beam in the range of energies 0.2 -30 keV are presented. The obvious effect of damaging the nanostructures by all used beam energies for specimens placed on insulator substrates ($SiO_2$) was revealed. At the same time, no signs of structural defects were observed in the cases when FLG have been arranged on metallic substrate. A new physical mechanism of under threshold energy defect production supposing possible formation of intensive electrical charged puddles on insulator substrate surface is suggested.

• Pediatric Gastroenterology, Hepatology & Nutrition
• /
• 제24권2호
• /
• pp.238-243
• /
• 2021

Caudal regression syndrome (CRS) is a rare neural tube defect that affects the terminal spinal segment, manifesting as neurological deficits and structural anomalies in the lower body. We report a case of a 31-month-old boy presenting with constipation who had long been considered to have functional constipation but was finally confirmed to have CRS. Small, flat buttocks with bilateral buttock dimples and a short intergluteal cleft were identified on close examination. Plain radiographs of the abdomen, retrospectively reviewed, revealed the absence of the distal sacrum and the coccyx. During the 5-year follow-up period, we could find his long-term clinical course showing bowel and bladder dysfunction without progressive neurologic deficits. We present this case to highlight the fact that a precise physical examination, along with a close evaluation of plain radiographs encompassing the sacrum, is necessary with a strong suspicion of spinal dysraphism when confronting a child with chronic constipation despite the absence of neurologic deficits or gross structural anomalies.

• 한국결정성장학회지
• /
• 제19권2호
• /
• pp.90-94
• /
• 2009

Mong Hsu rubies from Myanmar were heat treated in oxidizing(oxygen) atmosphere at $1650^{\circ}C$ for 1 hour. The investigations of the micro-structural defects in the samples before and after heat treatment have been carried out by the variety of analysis techniques of FTIR, UV-VIS-NIR and SEM-EDS. It was found that after heat treatment the dark blue cores region were disappeared and turned to orange red color with the presence of the dense cloudy brownish colored tiny particles in and near former blue zoning. As-received ruby samples only revealed the presence of FTIR absorption peaks of diaspore, boehmite and O-H stretching, at 1986, 2115 and $3078/3319\;cm^{-1}$ respectively. The UV-VIS-NIR absorption of as-received and heat treated ruby samples similarly showed peaks at 405, 554 and 693 nm associated with $Cr^{3+}$, but for the same samples, the absorption peak of heat-treated ruby samples at 693 nm was somewhat stronger than that of the untreated ruby samples. Especially the presence of $Cr^{3+}$ peaks at 659 and 675 nm was found obviously in as-received ruby samples only. The SEM-EDS investigation disclosed the micro-porous defect structures commonly related to the core regions of the untreated ruby samples, which after heat treatment in an oxidizing environment those defect features have been dissolved into the host phase resulting in the lightening or disappearance of the dark coloration of ruby core.

• 한국정보통신학회논문지
• /
• 제4권3호
• /
• pp.713-719
• /
• 2000

고체상 켜쌓기법(solid phase epitaxy)으로$Ge_xSi_{1-x}/Si$(111) 이종접합을 형성하기 위해 Si(111) 기판위에 먼저 Au를 1000A 증착하고 그 위에 Ge을 1000A 증착시켜 a-Ge/Au/Si(111)구조를 형성하고 이를 고진공 조건에서 이단계 열처리 하였다. 열처리 후 Auger 전자분광분석(AES), X-ray 회절(XRD), 고분해 투과전자현미경(HRTEM) 등을 통해 Au와 Ge의 거동과 형성된 $Ge_xSi_{1-x}$막의 특성을 열처리 조건에 따라 분석하였다. a-Ge/Au/Si(111)구조는 열처리에 의해 Au/GeSi/Si(111)의 구조로 변했으며 형성된$Ge_xSi_{1-x}/$((111)층은 Si(111) 기판의 면 방향과 잘 일치하였다. 그러나 $Ge_xSi_{1-x}/Si$((111)층 내부에 적층결함, 전이, 쌍정, planar defect 등이 주로 (111)면 방향으로 형성되어 있음을 알 수 있었다.

• Journal of Electrochemical Science and Technology
• /
• 제7권4호
• /
• pp.306-315
• /
• 2016

Amorphous vanadium titanates (aVTOs) are examined for use as a negative electrode in lithium-ion batteries. These amorphous mixed oxides are synthesized in nanosized particles (<100 nm) and flocculated to form secondary particles. The $V^{5+}$ ions in aVTO are found to occupy tetrahedral sites, whereas the $Ti^{4+}$ ions show fivefold coordination. Both are uniformly dispersed at the atomic scale in the amorphous oxide matrix, which has abundant structural defects. The first reversible capacity of an aVTO electrode ($295mAhg^{-1}$) is larger than that observed for a physically mixed electrode (1:2 $aV_2O_5$ | $aTiO_2$, $245mAhg^{-1}$). The discrepancy seems to be due to the unique four-coordinated $V^{5+}$ ions in aVTO, which either are more electron-accepting or generate more structural defects that serve as $Li^+$ storage sites. Coin-type Li/aVTO cells show a large irreversible capacity in the first cycle. When they are prepared under nitrogen (aVTO-N), the population of surface hydroxyl groups is greatly reduced. These groups irreversibly produce highly resistive inorganic compounds (LiOH and $Li_2O$), leading to increased irreversible capacity and electrode resistance. As a result, the material prepared under nitrogen shows higher Coulombic efficiency and rate capability.

• 한국구조물진단유지관리공학회 논문집
• /
• 제12권2호
• /
• pp.75-82
• /
• 2008

국내에는 약 18,000여개의 댐이 있는 것으로 보고되고 있다. 이 중에서 대댐으로 분류되는 1,200여개의 대댐은 비교적 양호하게 운영 관리되고 있으나, 지자체 등에서 관리하는 소규모의 댐들은 대부분 제체를 관통하는 복통을 갖고 있으며, 제도적 장치의 미비와 전문 인력의 부족으로 체계적인 유지관리가 거의 이루어지지 않고 있는 실정이다. 본 연구에서는 소규모 댐들에서 자주 발생하는 결함의 유형에 대해서 고찰하고, 결함의 보수보강을 통하여 소규모 댐의 안전을 확보할 수 있는 방법을 제시하고자 한다. 또한, 전기비저항 탐사를 통하여 결함의 진행정도를 파악하고, 보수보강 이후의 보수보강 효과를 판정하는 방법론을 제시하고자 하였다.

• 한국구조물진단유지관리공학회 논문집
• /
• 제17권4호
• /
• pp.119-127
• /
• 2013

외부에 설치된 목재 구조물 및 목조주택의 경우 기본적인 접합에 사용되는 철물은 스크류 볼트, 스테인리스 못, 일반 철못을 사용하는데, 목재의 철물 접합 부분이 외기 환경에 직접적으로 노출됨에 따라 온습도 변화에 의한 영향으로 철물 접합부 못의 마찰 저항성이 저하되어 이에 대한 하자가 지속적으로 발생하고 있으며, 이에 따른 유지보수가 반드시 필요한 실정이다. 하지만, 문제의 개선을 위한 기초자료 확보와 같은 실험 분석 등 현재까지 많은 연구와 대책수립이 이루어지지 않아 하자가 발생된 목재 구조물이 방치되고 있는 실정이므로 본 연구에서는 목재 및 철물 종류별 접합부의 마찰 저항성 분석을 통해 이와 같은 문제 해결을 위한 못 뽑기 저항 특성 분석으로 목재 수종 및 제조 조건 별 올바른 철물 사용 제안과 유지관리 및 보수 보강 계획을 수립할 수 있는 기초자료를 확보하고자 한다.

• 한국재료학회지
• /
• 제21권12호
• /
• pp.685-689
• /
• 2011

The goal of this investigation was to produce a zirconia-family black ceramics that has enhanced functionality and reliability. Color zirconia ceramics have been produced by adding pigments. Pigments cause structural defects within zirconia and result in a drop in physical properties. Using environmentally friendly rice husk, we produced a black zirconia that is free of structural defects. In optimal firing conditions for black zirconia the calcining temperatures of the molding product are changed from $400^{\circ}C$ to $1200^{\circ}C$, and the firing temperatures are changed from $1400^{\circ}C$ to $1600^{\circ}C$. Color of testing the specimens was analyzed using Ultraviolet (UV) spectroscopy. Scanning Electron Microscope (SEM), EDAX (EDX), and Fourier transform infrared spectroscopy (FT-IR) analyses were carried out in order to examine impregnation properties and crystal phases. Universial Test Machine (UTM) was used to measure the flexual strength as well as the compressive strength. From experimental results, it was found that in optimal firing conditions the sample was calcined from $1000^{\circ}C$ to $1500^{\circ}C$. Commission internationalde I'Edairage (CIE) values of manufactured black zirconia color were $L^*$ = 29.73, $a^*$ = 0.23, $b^*$ = -2.68. The bending strength was 918 MPa and the compressive strength was 2676 MPa. These strength values are similar to typical strength values of zirconia, which confirms that carbon impregnation did not influence physical properties.