• Title/Summary/Keyword: Buttress

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Effects of Screw Diameter and Thread Shape on the Strength of Transpedicular Screw Fixation in Posterior Spinal Fusion (후방 척추고정술에서 척추경 나사못의 크기와 형태가 척추 고정력에 미치는 영향에 대한 연구)

  • Mun, Mu-S.;Ryu, Jei-C.;Yoo, Myung-C.;Kim, Ki-T.
    • Proceedings of the KOSOMBE Conference
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    • v.1995 no.05
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    • pp.23-26
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    • 1995
  • The objectives of the present study are 1)to find the effect of the diameter of transpedicular screws on their fixational strength in pedicles under static pull-out loading, 2)to determine the biomechanical correlation between the pedicle diameter and the screw diameter, and 3)to find the effects of other factors in the screw design, such as materials, screw pitch, thread height and shape on their fixational strength. Biomechanical tests (Test I) were performed to evaluate the effect of the screw diameter on pull-out strength by using 60 porcine pedicls and six groups of custom-made pedicle screws with different diameters (the major and the minor diameter of the screws used in the testing varied from 4mm upto 9mm and from 3mm upto 8mm, respectively) while all other factors (materials, screw pitch, thread height and shape etc.) were fixed. In Test II, by using 61 porcine pedicles, the relationship between the ratio of the pedicle diameter and the screw diameter(=aspect ratio) of the custum-made screw and the pull-out strength of the screw was investigated. Test III was performed with 94 porcine pedicles and 8 different types of the commercial screws from 6 major productors in order to determine the effect of the screw diameter, pitch and the thread shape on the pull-out strength of the screw, respectively. The results of Test I showed that the axial pull-out resistance of the screw could be increased prportionaly to the screw diameter(P<0.05). But this increase in the pull-out resistance did not found when the screws of 4mm or 9mm in the diameter were employed. It was found from the results of Test II that the screws had its maximum pull-out resistant force when the aspect ratio ranging 40 - 69% (P<0.05). based on the results for the major diameter against the minor diameter of screw, the maximal pull-out resistance was found at 60-65% (P<0.05). According to these biomechanical testing results, it seems that the screw with a moderately large pitch is more desirable and the buttress-shaped screw can provide stronger fixation than the V-shape one can, if other designal factor and conditions were fixed.

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Changes in Benthic Macroinvertebrate Community Before and After Rainy Season in Mountain Valley with Erosion Control Dam (사방댐이 설치된 산지계곡의 장마 전·후 저서성 대형무척추동물 군집변화)

  • An, Chae-Hui;Han, Jung-Soo;Choi, Jun-Kil;Lee, Hwang-Goo
    • Korean Journal of Environment and Ecology
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    • v.34 no.2
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    • pp.121-129
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    • 2020
  • This study investigated the change of benthic macroinvertebrates community due to erosion control dams installed in Wonju, Gangwon by comparing the data before and after a rainy season. It selected a closed-type erosion control dam (boulder stone), an open-type erosion control dam (buttress), and a control area and surveyed two upstream points and two downstream points four times between March and September 2019. The flow velocity mostly increased in the closed-type, open-type, and control areas but decreased in St. 3 after the rainy season. The number of benthic macroinvertebrates species and their populations mostly decreased after the rainy season, and the rate of decrease in the populations in the open-type and control areas were more similar than the closed-type area. Species and populations of the EPT groups mostly decreased after the rainy season. A result of the similarity analysis showed that the closed-type and open-type areas were separated by 38.4% with the control area before the rainy season, but the open-type and control areas were separated by 51.3% with the closed-type area after the rainy season. A result of the principal components analysis (PCA) based on axis 1 showed that the closed-type area had a positive value before and after the rainy season, and the open-type and control areas had a negative value before and after the rainy season. The open-type area was more correlated with the control area than the close type. The analysis of the EPT groups showed the distribution of Ephemeroptera in the closed-type area and Trichoptera in the open-type and control areas. The result of this study shows that the installation of erosion control dam can cause changes in benthic macroinvertebrates community and that the open-type area had a smaller difference community difference from the control area after the rainy season than the closed-type area.

Study on 3D Printer Suitable for Character Merchandise Production Training (캐릭터 상품 제작 교육에 적합한 3D프린터 연구)

  • Kwon, Dong-Hyun
    • Cartoon and Animation Studies
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    • s.41
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    • pp.455-486
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    • 2015
  • The 3D printing technology, which started from the patent registration in 1986, was a technology that did not attract attention other than from some companies, due to the lack of awareness at the time. However, today, as expiring patents are appearing after the passage of 20 years, the price of 3D printers have decreased to the level of allowing purchase by individuals and the technology is attracting attention from industries, in addition to the general public, such as by naturally accepting 3D and to share 3D data, based on the generalization of online information exchange and improvement of computer performance. The production capability of 3D printers, which is based on digital data enabling digital transmission and revision and supplementation or production manufacturing not requiring molding, may provide a groundbreaking change to the process of manufacturing, and may attain the same effect in the character merchandise sector. Using a 3D printer is becoming a necessity in various figure merchandise productions which are in the forefront of the kidult culture that is recently gaining attention, and when predicting the demand by the industrial sites related to such character merchandise and when considering the more inexpensive price due to the expiration of patents and sharing of technology, expanding opportunities and sectors of employment and cultivating manpower that are able to engage in further creative work seems as a must, by introducing education courses cultivating manpower that can utilize 3D printers at the education field. However, there are limits in the information that can be obtained when seeking to introduce 3D printers in school education. Because the press or information media only mentions general information, such as the growth of the industrial size or prosperous future value of 3D printers, the research level of the academic world also remains at the level of organizing contents in an introductory level, such as by analyzing data on industrial size, analyzing the applicable scope in the industry, or introducing the printing technology. Such lack of information gives rise to problems at the education site. There would be no choice but to incur temporal and opportunity expenses, since the technology would only be able to be used after going through trials and errors, by first introducing the technology without examining the actual information, such as through comparing the strengths and weaknesses. In particular, if an expensive equipment introduced does not suit the features of school education, the loss costs would be significant. This research targeted general users without a technology-related basis, instead of specialists. By comparing the strengths and weaknesses and analyzing the problems and matters requiring notice upon use, pursuant to the representative technologies, instead of merely introducing the 3D printer technology as had been done previously, this research sought to explain the types of features that a 3D printer should have, in particular, when required in education relating to the development of figure merchandise as an optional cultural contents at cartoon-related departments, and sought to provide information that can be of practical help when seeking to provide education using 3D printers in the future. In the main body, the technologies were explained by making a classification based on a new perspective, such as the buttress method, types of materials, two-dimensional printing method, and three-dimensional printing method. The reason for selecting such different classification method was to easily allow mutual comparison of the practical problems upon use. In conclusion, the most suitable 3D printer was selected as the printer in the FDM method, which is comparatively cheap and requires low repair and maintenance cost and low materials expenses, although rather insufficient in the quality of outputs, and a recommendation was made, in addition, to select an entity that is supportive in providing technical support.