• 대한기계학회논문집B
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• 제40권10호
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• pp.659-666
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• 2016

본 연구는 길이에 따른 사각 기둥 타입을 변수로 선정하여 각각의 길이 패턴을 지닌 고체 표면에서의 물 액적 젖음 특성을 분자 동역학을 이용하여 규명하였다. 기둥의 표면 형상을 정사각형과 직사각형의 형태로 가정하였고, 정해진 형상에서의 표면 면적을 증가시켰다. 정사각형 형상의 경우 각 변의 길이가 $4.24{\AA}$, $8.48{\AA}$, $12.72{\AA}$로 증가하였으며, 직사각형 형상의 경우 고정된 한 변은 $8.48{\AA}$의 길이를 가지며 다른 한 변의 길이는 $4.24{\AA}$, $8.48{\AA}$, $12.72{\AA}$로 증가하였다. 이러한 길이 변화를 통해 사각기둥 표면형상의 변화 및 전체 고체표면의 면적 대비 기둥이 차지하는 면적의 비율에 따른 물 액적의 변화를 살펴보고, 표면과 물 액적과의 접촉각을 측정하여 비교 분석하였다.

• 대한치과보철학회지
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• 제39권3호
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• pp.250-259
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• 2001

Since the late 1930s, acrylic resins have been the materials of choice for the fabrication of complete denture bases. It has excellent esthetic properties, adequate strength, low water sorption, and low solubility. But acrylic resin has disadvantage of processing shrinkage that reduces denture retention and accuracy of denture occlusion. Metals also have been used in denture base material. Metals used in denture bases display excellent strength and dimensional stability. The major disadvantages associated with metal denture bases include increased cost, difficulty in fabrication, compromised esthetic qualities, and inability to re-base. The purpose of this study is to compare the artificial tooth movements of complete dentures with resin bases and metal bases after curing, deflasking, polishing immersion in water for 1 week and 4 weeks. Twenty-four maxillary complete resin denture bases with artificial teeth were fabricated. Twelve of them were resin based and other twelve of them were metal based. Fine crosses were marked on the incisal edges of right central incisors and distobuccal cusps of be second molars. Measurements were done for the changes of distances of reference points at the time of wax denture, after deflasking after decasting after polishing after immersion in water for 1 week and 4 weeks Meaurements were done to the accuracy of 0.001mm with a measuring microscope. The results were as follows : 1. Metal base showed significantly less tooth movement than resin base after curing and decasting (p<0.01). 2. Metal base showed significantly less tooth movement than resin base after polishing (p<0.01). 3. After immersion in water for 1 week and 4 weeks, metal base showed less movement than resin base. Difference was significant for anterior-posterior distances (p<0.01), but not significant for molar-to-molar distance (p>0.01). 4. 1 week and 4 weeks of immersion failed to compensate the initial processing shrinkage of metal and resin bases (p>0.01).

• 한국환경복원기술학회지
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• 제20권6호
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• pp.1-19
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• 2017

This study set out to identify problems with amphibian habitation by the wetland types and improve their habitation environment in urban forest wetlands, thus creating a habitat for amphibians. Study site include forest swamps in Jatjul Park as well as Yeoji neighborhood Park in Guro-gu, and in Choansan neighborhood Park in Dobong-gu. The forest swamp in Jatjul Park gets its water from Mt. Maebong and it is a former escalated farmland-turned wetland. The swamp area is $2,500m^2$, a forest zone and a landscape planting site are 83.27% and 6.70% each. Target species Seoul pond frogs are inseparable from rice fields because they live in a short radius of and lay eggs in or near paddy fields, and Rana nigromaculata have similarities with Rana plancyi chosenica in choosing their habitats. There was need for paths that would lead to other paths so amphibians would spread to other parts of the forest and for measures to secure open water. Modifying a variety of routes for water, human and animals along with building a buffer to keep the core habitation zones were required. The forest swamp in Yeonji neighborhood Park used to be a water reservoir on the foot of Mt. Gunji. The swamp area is $1,980m^2$, a forest zone and farmland account for 80.61% and 4.88% each. Non-point pollutants from upstream along run into the subject forest marsh, bare ground on the around swamp and steep stone embankments obstructed amphibians. Target species was Bufo gargarizans that live in forests and edges of hills and spawn in deep water. The forest swamp in Choansan neighborhood Park gets its water from Mt. Choan and it is close to its water source that it is a mountain stream forest wetland. The basin and the swamp are $35,240m^2$ and $250m^2$ in size respectively. A forest zone accounts for 90.20%, high stone embankments laid in refurbishing the valley obstruct amphibians and there is water shortage in times of droughts. Target species were Rana coreana, Rana dybowskii and Hynobius leechii that live in mountain valleys, streams and wetlands and lay eggs in forest marshes and rocks in valleys. Looking into the three swamps of amphibian habitation, I came to conclusions that those wetlands were suitable for their amphibians but man-made facilities blocked their corridors leading to other corridors and even killed off target species in some parts of those swamps by destroying those parts. Amphibians live in water, on ground and underground at different stages of life. Hence, we should take this fact into consideration when planning their habitats and design core habitation zones, buffers zone and use zones accordingly. Buffer zones ought to be between core habitation zones and surrounding trees. Aiming at protecting core habitation zones, buffers should be in harmony with habitation zones. Use zones should be minimized in size and not in direct contact with core habitation zones.

• 농업과학연구
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• 제37권3호
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• pp.435-449
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• 2010

Soils in the sloping uplands in Korea are subject to intensive land use with high input of agrochemicals and are vulnerable to soil erosion. Development of the environmentally sound land management strategy is essential for a sustainable production system in the sloping upland. This report addresses the status of upland agriculture and the best management practices for the uplands toward the sustainable agriculture. More than 60% of Korean lands are forest and only 21% are cultivating paddy and upland. Uplands are about 7% of the total lands and about 62% of the uplands are in the slopes higher than 7%. Due to the site-specificity of the upland, many managerial and environmental problems are occurring, such as severe erosion, shallow surface soils with rocky fragments, and loadings of non-point source (NPS) contaminants into the watershed. Based on the field trials, most of the sloping uplands were classified as Suitability Class III-V and the major limiting factor was slope and rock fragments. Due to this, soils were over-applied with N fertilizer, even though N rate was the recommendation. This resulted in decreases in yield, degradation of soil quality and increases in N loading to the leachate. Various case studies drew management practices toward sustainable production systems. The suggested BMP on the managerial, vegetative, and structural options were to practice buffer strips along the edges of fields and streams, winter cover crop, contour and mulching farming, detention weir, diversion drains, grassed waterway, and slope arrangement. With these options, conservation effects such as reductions in raindrop impact, flow velocity, runoff and sediment loss, and rill and gully erosion were observed. The proper management practice is a key element of the conservation of the soil and water in the sloping upland.

• 한국조경학회지
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• 제36권1호
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• pp.62-69
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• 2008

This study was conducted in order to recommend forest-based wildlife protection areas in Chung-nam Province using several basic habitat conditions. The conditions used in this study were the forest patch size with the potential to keep wildlife animals safe, the distance from water sources, and the availability of food for wildlife. The fractal dimension index was also used to find the edge line dynamics, which can influence on habitat conditions for edge species. The natural conservation management indices including a forest map (indicating the level of forest age), a slope map, and an elevation map were used to find the forest patches with enough space for wildlife to live on. Water resources and their buffer areas were considered as factors to protect the space as an ecological corridor. Deciduous trees and trees mixed with deciduous trees and conifers were chosen to provide wildlife animals their food. In total, 525 forest patches were chosen and recommended for the wildlife protection area. Five of these forest patches were recommended as wildlife protection areas managed by the provincial government. The other 520 forest patches were recommended to protect local wildlife animals and be managed by each county or city. These forest patches were located around the Geum-buk and Geum-nam mountains, and the forest patches are important resources as habitats to keep wildlife in the area. An ecological network consists of these separate forest patches with the ecological integration. A fractal dimension index was used to divide forest patches into several categories in order to find how patches are shaped. The forest patches with longer edges or more irregular shapes have a much higher possibility of being inhabited by various types of edge species. Through comparison of the wildlife protection areas recommended in this study to the current wildlife protection areas, we recognized that the current wildlife protection areas need boundary adjustments in order for wildlife animals to survive by themselves with water sources and food.

• 한국습지학회지
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• 제13권2호
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• pp.355-362
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• 2011

우리나라에서 멸종위기 식물인 조름나물(Menyanthes trifoliata L.)은 긴 지하경을 가지는 다년생 정수식 물이며, 양분이 적은 이탄습지 또는 산지 호수의 가장자리에 주로 서식한다. 조름나물의 복원 시 적절한 서식지 기질을 결정하기 위하여, 양분 함량이 다른 물, 물이끼 매트, 논흙을 기질로 사용한 메조코즘을 조성하여 조름나물의 성장을 조사하였다. 논흙의 경우에는 침수와 포화습윤 조건으로 나누어 조성하였다. 각 조건마다 약 10cm의 지하경을 심고, 피도, 잎의 면적, 잎의 개수, 지하경의 무게를 측정하였다. 각 변수들은, 양분이 적은 수경 재배와 물이끼 매트에서 8월경에 최고치를 보이다가 감소하였다. 양분이 많은 논흙에서는 10월까지 계속 성장하여 모든 변수에서 시작 때의 2배 이상으로 성장하였다. 지하경의 무게는 위의 기질 조건 각각에서 49, 77, 239, 312g으로 증가하였다. 본 실험결과는 조름나물이 자연에서는 양분이 적은 곳에 서식할지라도 단독으로 자라는 조건에서는 양분이 많은 환경에서 더 잘 자란다는 것을 말해준다. 이는 조름나물의 서식 기질에서의 기본적인 생태적 지위와 실제적인 생태적 지위가 다름을 의미한다. 조름나물의 성공적인 복원을 위해서는 조름나물의 서식지를 제한하는 다른 요인과 생존 전략을 밝히는 추가적인 연구가 필요하다.

• 한국컴퓨터정보학회논문지
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• 제15권9호
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• pp.67-76
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• 2010

본 논문은 수위 측정 영역의 오염 상태에 적응적인 영상 기반 수위 계측 기법을 제안한다. 수위를 측정하기 위해 사용되는 목자판이 진흙, 부유물, 조명의 강한 반사에 의해 얼룩진 경우, 목자판 내부의 수평 성분 패턴이 유지되는 영역의 최종 위치와 목자판과 수면의 색상 차를 이용하여 얻어진 대략적인 수위 위치인 참조 수위와의 거리 차를 측정하여 목자판의 오염 여부를 판단하는 기법을 사용한다. 목자판이 오염되지 않은 경우에는 수평 성분이 유지되는 최종 위치의 근방 하단 영역에서 수평 성분의 분포를 분석하여 히스토그램이 가지는 최대값의 30%이상의 값을 가지는 위치를 수위로 검출하고, 목자판이 오염된 경우는 참조 수위 근방의 색상 변화의 국지적인 정점과 골을 검출한 후 그 변화가 가장 큰 위치를 수위로 검출한다. 검출된 영상 수위는 영상에 보이는 목자판의 눈금을 기준으로 생성한 맵핑 테이블을 이용하여 실제 수위로 변환된다. 제안한 방법의 적용 가능성과 일반성을 평가하기 위하여 실제 교량에 측정 시스템을 구축하고 같은 위치에 기존에 설치된 초음파 기반 측정 시스템과 그 측정치를 비교하였다.

• 산업기술연구
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• 제21권B호
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• pp.281-286
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• 2001

In this study, product design and prototype manufacturing of a plastic water-pump pulley has been tried. The designed model is supposed to be made of 33 % glass reinforced resin of which the tensile strength is 180 MPa, and has 24 ribs on each side to increase its structural strength. Structural analysis under a static load of 300 kgf acting on both edges of the belt has been carried out using a commercial finite element code, MARC. The analysis result showed the maximum effective stress near a rib of designed model would be at most 35 MPa (less than 20% of the tensile strength), therefore, the plastic product would be sufficiently safe under that loading condition. On the basis of the structural analysis, a prototype of the designed model has been manufactured by using the fused deposition modelling (FDM) method which is one of the rapid prototyping (RP) methods, using ABS resin and support materials. The CAD data exported to the RP system in STL format was prepared by a commercial solid modeling software, SolidWorks. It has been proved that the plastic pulley can successfully replace the existing flow-formed steel product.

• Bulletin of the Korean Chemical Society
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• 제24권8호
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• pp.1155-1162
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• 2003

Nanocrystalline semiconductor film electrodes have been prepared by sintering three different sizes of TiO₂ nanoparticle sols on conducting indium-tin-oxide (ITO) glass substrate. The electrochemical and photoelectrochemical properties of the prepared electrodes were comparatively investigated. The particle sizes, surface morphologies and crystallinities of the films were studied by scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. Cyclic voltammetry and capacitance measurements in the dark implies the formation of depletion layer in the semiconductor films which was usually neglected in the previous studies and shows that flat band potential ($E_{fb}$

• 한국기계가공학회지
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• 제8권2호
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• pp.3-9
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• 2009

When washing machine is rotated in the laundry, it tends to lean toward one side. This tendency causes a serious vibration. The balance of washing machine plays an important role in order to reduce the vibration by injecting the sand or the salt water into the balance of washing machine. The hot plate welder is used to prevent from outflow of contents. The hot plate welder brings about many problems which is concerned with accidents. The direction recognition and location information of the balance are required in this system. In this paper, the recognition direction of balance in washing machine using machine vision system is studied. The template matching algorithm compares sub-image with original image acquired in real-time to obtain a center point of balance image. The mid points and the edges of balance are estimated by the edge detection and gauging algorithms. The data acquired by these results is used for recognition direction of balance. The automation software for image processing is developed by using LabVIEW.