• 한국진공학회:학술대회논문집
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• 한국진공학회 2009년도 제38회 동계학술대회 초록집
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• pp.358-358
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• 2010

Ion beam bombardment at low energy forms nanosize patterns such as ripples, dots or wrinkles on the surface of polymers in ambient temperature and pressure. It has been known that the ion beam can alter the polymer surface that induces skins stiffer or the density higher by higher compressive stress or strain energies associated with chain scissions and crosslinks of the polymer. Atomic scale structure evolution in polymers is essential to understand a stress generation mechanism during the ion beam bombardment, which governs the nanoscale surface structure evolution. In this work, Molecular Dynamics (MD) simulations are employed to characterize the phenomenon occurred in bombardment between the ion beam and polymers that forms nanosize patterns. We investigate the structure evolution of Low Density Polyethylene (LDPE) at 300 K as the polymer is bombarded with Argon ions having various kinetic energies ranging from 100 eV to 1 KeV with 50 eV intervals having the fluence of $1.45\;{\times}\;1014 #/cm2$. These simulations use the Reactive Force Field (ReaxFF), which can mimic chemical covalent bonds and includes van der Waals potentials for describing the intermolecular interactions. The results show the details of the structural evolution of LDPE by the low energy Ar ion bombardment. Analyses through kinetic and potential energy, number of crosslinks and chain scissions, level of local densification and motions of atoms support that the residual strain energies on the surface is strongly associated with the number of crosslinks or scissored chains. Also, we could find an optimal Ar ion beam energy to make crosslinks well.

• 대한수의학회지
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• 제34권2호
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• pp.219-227
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• 1994

The development of abomasum in fetuses between 60, 90, 120 days of gestation and neonates of Korean native goats was investigated by light, scanning and transmission electron microscopy. The results obtained were summarized as follows ; 1. The abomasum wall appeared to be differentiated into the epithelium, lamina propria, muscle layer, and serosa at 60 days of gestation. The epithelium was stratified columnar and these nuclei were located near the apical two thirds portion of the cell at 60 days of gestation, and then transformed into simple columnar epithelium with the flat basal nuclei. 2. The inner circular and outer longitudinal muscle layers were observed at 90 days of gestation and the blood vessels had become quite well developed as various arterioles, venules and capillaries of different size during this age. 3. Gastric pits were seen at 90 days of gestation and continued gradually to increase depth during gestation. 4. The mucous, parietal and chief cells appeared in epithelium at 90 days of gestation and continued gradually to increase in number during gestation. In 120 days fetuses and neonates, muscle layer had become very thickeness. 5. Scanning electron microscopically, the inner surface of the abomasum already consisted of wavy spiral folds which had many fine wrinkles at 60 days of gestation. In 90 day old fetuses, each spiral fold was enlarged and its surface was tended to be split into many straight longitudinal ridges and among these ridge were found shallow grooves, At 120 days, the subdivided swellings of ridges were progressively complicated in shape. In the neonates, the inner surface was flat and holed with many gastric pits. 6. Transmission electron microscopically, the epithelium was straified columnar and these nuclei were irregular shape at 60 days fetus. The parietal, chief and mucous cells were observed in 90 day old fetuses and continued gradually to increase in number during gestation. 7. The development of the abomasum was relatively slow at early stages, it was accelerated greatly in the last of gestation.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제28권5호
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• pp.434-444
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• 2006

This study was performed to evaluate the effects of three different implant surface treatments to the bone formation during osseous healing period under unloading conditions. Machined, double-acid etched and anodic oxidized implants were inserted into tibia of 3.0 - 3.5 kg NZ white male rabbits and 2 animals of each group were sacrificed at 2, 4 and 8 weeks. The specimens containing implant was dehydrated and embedded into hard methylmethacrylate plastic. After grinding to $50{\mu}m$, the specimens were stained with Villanueva bone stain. From each specimen, histomorphometric evaluation and the bone implant contact rate were analysed with optical microscope. The results were as follows; 1. In the scanning electronic microscopic examination, machined surface implant had several shallow and paralleled scratches on plain surface, double acid-etched implant had lots of minute wrinkles, rough valley and also irregularly located craters that looked like waves, anodic oxidized surface implant had porosity that minute holes were wholly distributed on the surface. 2. After 2 weeks of implantation, the percentages of bone-to-implant contact in the machined implant, double acid-etched implant and anodic oxidized implant were 26.85%, 62.64% and 59.82%, after 4 weeks of implantation they were 64.29%, 77.85% and 75.23%, and after 8 weeks they were 82.66%, 85.34% and 86.39%. 3. After 2 weeks of implantation, the percentages of bone area between threads in the machined implant, double acid-etched implant and anodic oxidized implant were 21.55%, 42.81%, and 40.33%, after 4 weeks of implantation they were 49.32%, 62.60% and 75.56%, and after 8 weeks they were 71.62%, 87.73% and 83.94%. In summary, percentages of implant surface contacted to bone trabeculae and bone formation area inside threads in double acid-etched implants and anodic oxidized implants were greater than machined implants in early healing stage. These results suggest that double acid-etched and anodic oxidized surface implants could reduce the healing period for osseointegration and may enable to do early function.

• 소성∙가공
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• 제22권5호
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• pp.243-249
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• 2013

The multi-point forming (MPF) process for three-dimensional curved sheet metal has been developed as an alternative to the conventional die forming process since MPF allows the manufacturing of various shapes using one die set and reduce the cost of production. However, the MPF process cannot provide high quality products yet due to defects occurring in the sheet such as dimples and wrinkles. It can also lead to economic loss because of long tool setup time and additional machining required outside of the sheet formed area. In this study, a new sheet metal forming method, called flexible roll forming (FRF), is proposed to solve the problems of existing processes for three-dimensional curved sheet metal. This progressive process utilizes adjusting rods, as well as upper and lower flexible rollers as forming tools. In contrast with the existing processes, FRF can reduce the additional production costs because of the possible blank size for the part longitudinal direction, which is unrestricted. In this research, methods and procedures of the flexible roll forming technology are described. Numerical forming simulations of representative three-dimensional curved sheet products are also carried out to demonstrate the feasibility of this technology.

• 한국게임학회 논문지
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• 제9권4호
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• pp.97-106
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• 2009

본 논문은 적응적 메쉬 구조를 이용하여 가상 종이 객체를 실시간에 시뮬레이션 하는 방법을 제안한다. 제안된 기법은 임의의 삼각 메쉬에 적용될 수 있으며, 안정적인 수치 적분과 변형 기반 메쉬 세분화를 이용하여 효율적으로 종이 표면의 주름과 구김을 생성한다. 종이 객체의 구겨짐을 사실적으로 표현하기 위하여 부러지는 스프링을 가진 적응적 메쉬 구조를 사용한다. 적응적 구조가 지속적으로 질점을 삽입 혹은 삭제하기 때문에, 질량과 운동량의 보존이 고려되어야만 사실적인 종이 시뮬레이션이 가능하다. 제안된 기법은 실시간 환경에서 종이와 같이 얇은 쉘 구조의 사실적인 애니메이션을 생성한다.

• Animal Systematics, Evolution and Diversity
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• 제28권2호
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• pp.126-132
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• 2012

A new monstrilloid species belonging to the genus $Cymbasoma$ is described as a preliminary result from nocturnal surveys using a light trap on the east and south coasts of South Korea. Monstrilloid copepods are first recorded in South Korea. $Cymbasoma$ $striifrons$ n. sp. resembles $C.$ $striatum$ (Isaac, 1974) and $C.$ $tumorifrons$ Isaac, 1975 in sharing the character combination of transverse striations on forehead, somewhat small body (generally slightly less or longer than 1 mm), single lobed leg 5 bearing a short medial seta in female, and smooth lateral margin of anal somite without notch and wrinkles. However, $C.$ $striifrons$ n. sp. differs from $C.$ $striatum$ by relatively short and swollen cephalothorax, and rather strongly wrinkled genital somite. $Cymbasoma$ $striifrons$ n. sp. is also distinguished from $C.$ $tumorifrons$ in lacking a rounded protuberance on anterior margin of ventral surface and by relatively short cephalothorax and the number of ventral nipple-like processes on cephalothorax. Herein the new species is described and illustrated, with some comments on the morphological comparison with its allied species.

• Journal of Plant Biology
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• 제22권1_2호
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• pp.21-27
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• 1979

Sandy loam plots of pH 5.5, which was created by the reclamation of highlands in Yongin county, Kyeonggi province, was selected for the present experimental study. Sugar beet was cultured in these plots by treating them with calcium hydroxide and 3 replications to maintain pH 5.5, 6.4, 6.8, 7.2, and 7.6, respectively. The growth and yield of sugar beet were investigated and the results obtained showed a great deal of boron deficiency. The growth in its early stage was favorable in high pH plots, while no significant difference was observed in sugar content, root weight and sugar production at the time of harvest in each treated plot. The tendency of sugar accumulation appeared to be identical in terms of pattern in each treated plot; i.e. sugar was accumulated until early September but declined momentarily from the middle of September and then the sugar accumulation was resumed from the middle of October. The number of individuals in boron deficiency was larger in high pH plots and the condition of such boron deficiency was also severe. The result of analysis of boron contained in plant body revealed that the boron content of individuals caused boron deficiency by water culture and that occurred in the plots was small alike. The appearance of boron deficiency is characterized by the emergence of black stripes on the surface of the basal part of petiole, severe necrosis of young leaves in the area of growing point and severe wrinkles. Therefore it is felt necessary to pay particular attention to boron deficiency in the culture of sugar beet in our country.

• 소성∙가공
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• 제9권6호
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• pp.653-662
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• 2000

Wrinkling is one of the major defects in sheet metal products together with tearing, springback and other geometric and surface defects. The initiation and growth of wrinkles are influenced by many factors such as stress ratios, mechanical properties of the sheet material, geometry of the workpiece, contact condition, etc. It is difficult to analyze the wrinkling initiation and growth considering all the factors because the effects of the factors are very complex and the wrinkling behavior may show a wide scatter of data even for small deviations of factors. The finite element analyses of the wrinkling initiation and growth in the sheet metal forming process provide the detailed information about the wrinkling behavior of sheet metal. The direct analyses of the wrinkling initiation and growth, however, bring about a little difficulty in complex industrial problems because it needs large memory size and long computation time. In the present study, therefore, a global-local analysis technique is introduced for the computational efficiency. Through the analysis of wrinkling in the door inner stamping process, the efficiency of the global-local analysis technique is investigated.

• Design & Manufacturing
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• 제15권3호
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• pp.13-18
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• 2021

In plate forming technology, cylindrical drawing process is widely used in industry due to technological development. In this study, we used stainless steel 3042B and stainless steel 304J1, which are the most commonly used materials in the production of cold and hot water tanks for water purifiers, among cylindrical drawing products. Under the same conditions, the thickness of the sidewall of the product formed by drawn experiment was studied. As a result of the experiment, the bottom thickness of stainless steel 304J1 was considered to be thick. It is judged that the defect rate can be reduced by changing the breaking phenomenon of the floor surface of the cold and hot water bottles to the material of stainless steel 304j1. Stainless steel 304 2B material shows a sharp change in thickness from punch corner R to sidewall position, while stainless steel 304J1 material showed a uniform change from punch corner R to sidewall position. Stainless steel 304J1 material is considered to improve the clamping of the product in the process of extracting the product after hand drawing. The appearance of stainless steel 3042B products is considered to produce more wrinkles in the flange, which exerts greater tensile force on the sidewall during molding, resulting in uneven sidewall thickness.

• 한국의류산업학회지
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• 제23권2호
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• pp.237-246
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• 2021

This study aims to analyze short sleeve cycling tops from three brands for a change in garment fit and pressure depending on the static and cycling postures. To this end, it used a 3D virtual garment system to virtualize the garments. Further, a cross-section of the 3D virtual garment data was obtained, and the space length was measured in the design-X program to prove the objectivity of the 3D virtual garment. The results indicated that three brands had a large space length at the front than the back because of the bent posture in cycling. Therefore, appropriate ease was required for the waist and abdomen. Although there were various cutting lines of the bodice panel by brand, the design of the cutting lines should consider the changes in the surface to reflect the bent posture in cycling. The results of this experiment confirmed that the wrinkles present in the 3D virtual garment were reflected in the cross-section and that the space length was small in the high-stress area, as shown in red. Therefore, it was proven the stress of the 3D virtual garment could be used for 3D virtual garment evaluation.