• 한국도로학회논문집
• /
• 제6권2호
• /
• pp.37-45
• /
• 2004

아스팔트 포장은 주행의 쾌적성, 안전성 그리고 시공 및 보수의 용이성으로 인하여 세계적으로 많은 도로에 널리 이용되고 있다. 그러나 우리나라의 경우 고도의 경제성장으로 인한 교통량 증가와 차량의 중량화로 야기된 상습적 인 지체와 여름철 고온현상으로 아스팔트 포장의 파손정도가 심화되고 포장수명이 단축됨으로서 유지보수비용이 급격히 증가하는 양상을 보이고 있다. 이에 국내외에서 아스팔트 포장에 대한 파손 방지대책 및 내구성 증진에 관한 연구들이 진행되고 있으며 그 한 방법으로 토목섬유와 같은 보강재를 포장체에 삽입하고 있다. 본 연구에서는 아스팔트 포장 표층의 거동을 점탄성으로 분석하였으며 포장체에 삽입된 지오그리드의 설치 위치, 포장단면의 두께를 조합하여 지오그리드의 최적 설치 위치를 알아보고 포장단면의 물성에 따른 민감도 분석을 수행하였다. 연구결과, 지오그리드를 기층과 보조기층 사이에 보강하였을 경우. 기층아래에서 발생하는 횡방향 인장응력을 무보강 아스팔트 포장에 비해 29$\sim$56% 정도 감소시켜 균열 발생을 상당히 억제 할 수 있을 것으로 판단되었다. 또한, 노상에서의 수직 변형률과 최대 전단변형률을 살펴보았을 때 지오그리드를 포장체에 삽입하여 소성변형에 대한 억제 효과도 얻을 수 있는 것으로 판단되었다.

• 대한의용생체공학회:의공학회지
• /
• 제26권2호
• /
• pp.73-86
• /
• 2005

We need to flatten the brain cortex to smooth surface, sphere, or 2D plane in order to view the buried sulci. The rendered 3D surface of the segmented white matter and gray matter does not have the topology of a sphere due to the partial volume effect and segmentation error. A surface without correct topology may lead to incorrect interpretation of local structural relationships and prevent cortical unfolding. Although some algorithms try to correct topology, they require heavy computation and fail to follow the deep and narrow sulci. This paper proposes a method that corrects topology of the rendered surface fast, accurately, and automatically. The proposed method removes fractions beside the main surface, fills cavities in the inside of the main surface, and removes handles in the surface. The proposed method to remove handles has three-step approach. Step 1 performs smoothing operation on the rendered surface. In Step 2, vertices of sphere are gradually deformed to the smoothed surfaces and finally to the boundary of the segmented white matter and gray matter. The Step 2 uses multi-resolutional approach to prevent the deep sulci from geometrical intersection. In Step 3, 3D binary image is constructed from the deformed sphere of Step 2 and 3D surface is regenerated from the 3D binary image to remove intersection that may happen. The experimental results show that the topology is corrected while principle sulci and gyri are preserved and the computation amount is acceptable.

• 열처리공학회지
• /
• 제28권6호
• /
• pp.300-309
• /
• 2015

The aim of the present study was to predict the variations in microstructure and deformation occurring during gas carburizing and quenching processes of a SCM420H planetary gear in a real production environment using the finite element method (FEM). The motivation for the present study came from the fact that previous FEM simulations have a limitation of the application to the real heat treatment process because they were performed with material properties provided by commercial programs and heat transfer coefficients (HTC) measured from laboratory conditions. Therefore, for the present simulation, many experimentally measured material properties were employed; phase transformation kinetics, thermal expansion coefficients, heat capacity, heat conductivity and HTC. Particularly, the HTCs were obtained by converting the cooling curves measured with a STS304 gear without phase transformations using an oil bath with an agitator in a real heat treatment factory. The FEM simulation was successfully conducted using the aforementioned material properties and HTC, and then the predicted results were well verified with experimental data, such as the cooling rate, microstructure, hardness profile and distortion.

• 한국분말재료학회지
• /
• 제9권6호
• /
• pp.441-448
• /
• 2002

Dispersions of non-soluble ceramic particles in a metallic matrix can enhance the strength and heat resistance of materials. With the advent of mechanical alloying it became possible to put the theoretical concept into practice by incorporating very fine particles in a flirty uniform distribution into often oxidation- and corrosion- resistant metal matrices. e.g. superalloys. The present paper will give an overview about the mechanical alloying technique as a dry, high energy ball milling process for producing composite metal powders with a fine controlled microstructure. The common way is milling of a mixture of metallic and nonmetallic powders (e.g. oxides. carbides, nitrides, borides) in a high energy ball mill. The heavy mechanical deformation during milling causes also fracture of the ceramic particles to be distributed homogeneously by further milling. The mechanisms of the process are described. To obtain a homogeneous distribution of nano-sized dispersoids in a more ductile matrix (e.g. aluminium-or copper based alloys) a reaction milling is suitable. Dispersoid can be formed in a solid state reaction by introducing materials that react with the matrix either during milling or during a subsequent heat treatment. The pre-conditions for obtaining high quality materials, which require a homogeneous distribution of small dis-persoids, are: milling behaviour of the ductile phase (Al, Cu) will be improved by the additives (e.g. graphite), homogeneous introduction of the additives into the granules is possible and the additive reacts with the matrix or an alloying element to form hard particles that are inert with respect to the matrix also at elevated temperatures. The mechanism of the in-situ formation of dispersoids is described using copper-based alloys as an example. A comparison between the in-situ formation of dispersoids (TiC) in the copper matrix and the milling of Cu-TiC mixtures is given with respect to the microstructure and properties, obtained.

• 한국공간구조학회논문집
• /
• 제6권3호
• /
• pp.111-121
• /
• 2006

들림형 보구조는 휨재와 뜬지주, 스트링으로 조합되는 구조로서, 스트링에 PS력을 도입하여 휨재의 응력과 변형을 조절함으로써 구조능력을 높이는 구조시스템이다. 기존의 연구결과와 실사례를 조사하여 들림형 보구조의 특성과 구조계획시 구성방식을 파악하였다. 그 결과, 연력도형의 보의 형상 및 높낮이 그리고 스트링의 sag설정, 평면배열, 뜬지주의 수와 구성이 설계인자로서 고려될 수 있음을 파악하였고, 실사례와 구조적 거동의 연구고찰을 통해 그 설계인자의 세부 구성방식을 나타내었다. 또한 들림형 보구조는 큰 부가하중이 작용할 때의 구조부담을 줄이기 위하여 부가하중에 대해 별도의 저항 메카니즘을 고안함으로써 구조효율을 높일 수 있는 방식이 고려될 수 있음을 보였다.

• 건축역사연구
• /
• 제17권3호
• /
• pp.7-21
• /
• 2008

Three-story Stone pagodas in Gameunsa Temple site, one of the early staged stone pagodas, has been known as a standard of Silla stone pagodas. A stone pagoda is not only a stone art work and but also a stone architecture. In understanding the stone pagoda it is very important to be approached with technological side in which we can investigate the stone pagoda deeply and as well as to have been approached with art historical view. Also it needs that we should see the stone pagoda in view of structural safety. We can get many high technique from our ancestors who made Gameunsajiseoktap. 1. To reduce any deformation such as relaxation and sinking of members which is caused by a heavy load the members such as the lower tier of the base is made up of the foundation stone and side stone in each, comprising one stone. 2. A special construction method for connection between wall stone and column stone in stereobates was invented. It is to make column stone projected partially and wall stone be caved in that two members should be jointed well. This unique method is not used any longer after the three-story Stone pagodas in Gameunsa Temple Site. 3. In each side upper and lower member are not engaged as the size of roof stones and support stones of roof stones are different. It can be done for a distribution of perpendicular load and a prevention for relaxation of members. 4. It makes sure that to make upper ends of support stones 10mm lower was to be avoid upper loads to it judging from survey in disassemblying east pagoda. It proves that ancestors who made this stone pagoda had a technique to understand the structural matters to make small members as big as possible, not to engage in joint, to avoid in ends of members from upper load.

• 한국융합학회논문지
• /
• 제10권12호
• /
• pp.257-262
• /
• 2019

최근 취미로 다양한 레포츠를 즐기는 인구가 증가하였다. 그에 따라 차량 지붕위에 다양한 물건들을 적재한 차량들을 거리에서 쉽게 볼 수가 있다. 차량 지붕위에 적재를 할 수 있게 하는 장치는 랙 이라는 장치이며 차량마다 각기 다른 형상을 가지고 있다. 다양한 종류들이 있지만 무거운 짐을 적재하기 위해 강도 및 내구성을 가져야 한다. 본 연구에서는 루프 랙의 지지대 방식과 고정대의 형상에 따른 구조 해석을 하였다. 세 가지의 모델들 중, Model C가 가장 좋은 내구성을 가지고 있음을 보였다. 따라서 어떤 형상을 가진 루프랙이 가장 안정성이 있는 것을 본 연구 결과로서 알 수 있다. 본 결과를 토대로 얻은 자동차 루프랙의 형상에 따른 구조 해석에 통한 융합 연구에 대한 설계데이터를 활용함으로서 실생활에서의 자동차 부품에 융합하여 그 미감을 보일 수 있다.

• 마이크로전자및패키징학회지
• /
• 제12권3호
• /
• pp.207-212
• /
• 2005

Al, Ti, Ta 및 Cr 박막을 DC 마그네트론 스퍼터링방법으로 0 - 800 W의 RF 바이어스로 폴리이미드 기판에 가하면서 증착한 후 금속박막의 접착성을 연구하였다. 접착력은 $90^{\circ}$ 필 테스트로 평가하였다. 필 테스트 결과 모든 시편에서 기판에 RF 바이어스를 가하면 접착력이 향상되었다. RF바이어스를 가한 시편은 필링 도중 계면근처의 폴리이미드 내에서 파괴가 일어나면서 소성변형이 심하게 발생하였다. 단면 투과전자현미경 관찰에 의하면 금속/폴리이미드 계면은 분명하지 않고 복잡한 형상을 띄고 있었다. 이런 복잡한 계면은 RF 바이어스의 영향으로 생겼으며 접착력 향상의 주요 요인이었다.

• 한국의류학회지
• /
• 제35권8호
• /
• pp.968-981
• /
• 2011

This study examines the effect of the structure of Intarsia and Jacquard knit on mechanical properties of knit fabrics to suggest data for knit design. Intarsia and 7 types of Color Jacquard (Floating Jacquard, Normal Jacquard, Bird's eye Jacquard, Tubular Jacquard, Ladder's back Jacquard, Blister Jacquard, and Transfer Jacquard) were used. The samples with a gauge of 14 were knitted using 100% wool 2/48's yarn by Shima Seiki SIG computer knitting machine. The Objective Hand was measured by KES-FB system and HV and THV were calculated by the formula of KN-402-KT and KN-301-winter respectively. The results showed that Intarsia and Floating Jacquard are thin, flexible and light, Bird's eye Jacquard is slick, flat and slim, Tubular Jacquard is stiff and undrapable, Ladder's back Jacquard is difficult in shearing deformation and relatively bulky, Blister Jacquard is thickest and transfer jacquard is uneven in surface contour. The selection of proper structure is important for the knit apparel production since the thickness and weight of knit determine the amount of yarn needed and consequently the production cost. The hands of Ladder's back Jacquard and Tubular Jacquard are superior to those of other structures. Intarsia and Floating Jacquard which are thin, light and flexible seem to be good structures for designs showing a body silhouette whereas, Bird's eye Jacquard, Tubular Jacquard and Blister Jacquard (which are thick, heavy, and stiff) are suitable for a boxy silhouette.

• 열처리공학회지
• /
• 제13권1호
• /
• pp.1-9
• /
• 2000

The microstructural characteristics and low temperature tensile properties between $25^{\circ}C$ and $-196^{\circ}C$ for as-welded and age hardened specimen by using Al 5083-H321 for base metal, 5083-5356 and 5083-4043 weldments have been investigated. The hardness of 5083-5356 weldment decreases with aging treatment, whereas the weld region of 5083-4043 weldment shows remarkable increase in hardness after aging due to the precipitation of fine Si particle at the grain boundaries and interiors. Low temperature tensile properties of 5083 AI base metal, 5083-5356 and 5083-4043 weldments appear to be the increment of tensile strengths and elongations at the room temperature and $-196^{\circ}C$, while the decrement of tensile properties around $-50^{\circ}C$ is shown. Through the observation of fine serration to fracture in the stress-strain curve and tensile fractography, the increment of localized deformation leading to promote the neck initiation and the increment of the dimple size cause to decrease in tensile strengths and elongations around $-50^{\circ}C$. For the tensile specimen of the 5083 base metal, 5083-5356 and 5083-4043 weldments, the reason to increase in elongation after solution and aging treatment is the diminishment of fine pit, the resolution of Mg into the matrix and the spheridization of the eutectic Si.