• Title/Summary/Keyword: cross section shape

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Atherogenic Risk Stratification According to Changes in the Geometrical Shape of the Coronary Artery (관상동맥의 기하학적 형상변화에 따른 동맥경화 위험도)

  • Suh, Sang-Ho;Park, Jun-Gil;Roh, Hyung-Woon;Lee, Byung-Kwon;Kwon, Hyuck-Moon
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.34 no.10
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    • pp.893-899
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    • 2010
  • A previous study showed that hemodynamics is correlated with stenosis in the coronary artery. The flow characteristics and the distributions of the hemodynamic wall parameters in the coronary artery are investigated under physiological flow condition. The present study also aims to establish the mechanism of the generation of atherosclerosis by analyzing the hemodynamic variables in the coronary artery where atherosclerosis frequently occurs. The stenosis phenomena due to atherosclerosis are related to not only the biochemical reaction between blood and blood vessels but also the hemodynamic factors sush as flow separation and oscillatory wall shear stress. As the bifurcated angle increases, the size of the recirculation area that appears in the cross section increases and disturbed flow is observed in this area. We speculate that this area is the starting point of atherosclerosis in the coronary artery.

CFD Analysis of Axial Flow Cyclone Separator for Subway Station HVAC System (지하역사 공기조화기에 적용 가능한 미세먼지 제거용 사이클론의 수치해석적 연구)

  • Kim, Jin-Kwan;Kim, Ho-Joong;Lee, Myung-Jun;Kim, Tae-Sung;Kwon, Soon-Bark
    • Proceedings of the SAREK Conference
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    • 2008.11a
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    • pp.546-550
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    • 2008
  • In this study, 3-dimensional Computational Fluid Dynamics (CFD) analysis was induced to simulate air flow and particle motion in the axial flow cyclone separator. The commercialized CFD code FLUENT was used to visualize pressure drop and particle collection efficiency inside the cyclone. We simulated 4 cyclone models with different shape of vane, such as turning angle or shape of cross section. For the air flow simulation, we calculated the flow field using standard ${\kappa}-{\varepsilon}$ turbulence viscous model. Each model was simulated with different inlet or outlet boundary conditions. Our major concern for the flow filed simulation was pressure drop across the cyclone. For the particle trajectory simulation, we adopted Euler-Lagrangian approach to track particle motion from inlet to outlet of the cyclone. Particle collection efficiencies of various conditions are calculated by number based collection efficiency. The result showed that the rotation angle of the vane plays major roll to the pressure drop. But the smaller rotation angle of vane causes particle collection efficiency difference with different inlet position.

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A Study on the Estimation of the Structural Stability of a Container Crane according to the Change of the Boom Shape using Wind Tunnel Test (풍동실험을 이용한 붐 형상 변화에 따른 컨테이너 크레인 구조 안정성 평가에 관한 연구)

  • Lee Seong-Wook;Han Geun-Jo;Han Dong-Seop;Kim Tae-Ryung
    • Proceedings of the Korean Institute of Navigation and Port Research Conference
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    • 2006.06b
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    • pp.311-316
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    • 2006
  • This study was carried out to analyze the effect of wind load on the structural stability of a container crane according to the change of the boom shape using wind tunnel test and provided a container crane designer with data which can be used in a wind resistance design of a container crane assuming that a wind load at 75m/s wind velocity is applied on a container crane. Data acquisition conditions for this experiment were established in accordance with the similarity. The scale of a container crane dimension, wind velocity and time were chosen as 1/200, 1/13.3 and 1/15. And this experiment was implemented in an Eiffel type atmospheric boundary-layer wind tunnel with $11.25m^2$ cross-section area. Each directional drag and overturning moment coefficients were investigated and uplift forces at each supporting point due to the wind load were analyzed.

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Geometric Evaluation of Patient-Specific 3D Bolus from 3D Printed Mold and Casting Method for Radiation Therapy

  • An, Hyun Joon;Kim, Myeong Soo;Kim, Jiseong;Son, Jaeman;Choi, Chang Heon;Park, Jong Min;Kim, Jung-in
    • Progress in Medical Physics
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    • v.30 no.1
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    • pp.32-38
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    • 2019
  • Purpose: The objective of this study is to evaluate the geometrical accuracy of a patient-specific bolus based on a three-dimensional (3D) printed mold and casting method. Materials and Methods: Three breast cancer patients undergoing treatment for a superficial region were scanned using computed tomography (CT) and a designed bolus structure through a treatment planning system (TPS). For the fabrication of patient-specific bolus, we cast harmless certified silicone into 3D printed molds. The produced bolus was also imaged using CT under the same conditions as the patient CT to acquire its geometrical shape. We compared the shapes of the produced bolus with the planned bolus structure from the TPS by measuring the average distance between two structures after a surface registration. Results and Conclusions: The result of the average difference in distance was within 1 mm and, as the worst case, the absolute difference did not exceed ${\pm}2mm$. The result of the geometric difference in the cross-section profile of each bolus was approximately 1 mm, which is a similar property of the average difference in distance. This discrepancy was negligible in affecting the dose reduction. The proposed fabrication of patient-specific bolus is useful for radiation therapy in the treatment of superficial regions, particularly those with an irregular shape.

Discriminative criteria of Adenophorae Radix, Codonopsis Lanceolatae Radix and Adenophorae Remotiflori Radix (사삼(沙蔘), 양유(羊乳), 제니(薺苨)의 감별기준 연구)

  • Park, Eun-Sang;Lee, Se-Ree;Joeng, Jong-Min;Song, Myeong-Gyu;Yoon, Jee-Hyun;Ju, Young-Sung
    • The Korea Journal of Herbology
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    • v.32 no.2
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    • pp.33-40
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    • 2017
  • Objectives : This study is aimed at establishing the discriminative criteria for Adenophorae Radix (AT; Sasam), Codonopsis Lanceolatae Radix (CL; Yangyu) and Adenophorae Remotiflori Radix (AR; Jeni). Because of confusable publications and the similitude of herb shape, CL and AR have been used as AT in the markets. Methods : We firstly discriminated and confirmed AT, CL and AR through observing the external morphology of original plants. Then, external-internal morphological features of the medicinal herbs were studied. A stereoscope was used to determine macroscopic features of dried herbal medicines and a microscope was conducted to examine internal features with the samples, which were embedded in paraffin and stained. Results : 1. The original plant of CL was discriminated with the stem shape in comparison with others. AT and AR were classified by the leaf position of original plant. 2. In the macroscopic morphological study of medicinal herbs, CL had lumps, which seem like a wart. Also, AT and AR were different in the density of cross section. 3. In the microscopic morphological study of the medicinal herbs, the phloem, fissures and the arrangement of xylem were selected as discriminative criteria for 3 kinds of herbs. With these contents, we suggested the identification keys, including further details. Conclusions : These results, especially identification keys, will be helpful to distinguish 3 kinds of herbs, referred to as a 'Sasam'. Moreover, macroscopic and microscopic methods used in this article would be applicable tools for the discrimination of other herbs.

A Parametric Study on Intermediate Diaphragms of Steel-Box-Girder Bridges (강박스 거더교의 내부 다이아프램에 관한 매개변수 연구)

  • Park, Nam Hoi;Lim, Da Soo;Cho, Sun Kyu;Kang, Young Jong
    • Journal of Korean Society of Steel Construction
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    • v.15 no.3
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    • pp.231-239
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    • 2003
  • Many box girder bridges have been constructed during the past several decades due to their large bending and torsional rigidities as well as aesthetic considerations. However, box girders have shortcoming in that the cross section distorts under an eccentric loading and warps out of the section plane. Therefore, in order to reduce distortional stresses such as distortional warping and transverse bending normal stresses, diaphragms were generally installed in the box girders. Shapes of the diaphragms in steel-box-girder bridges constructed up to date were solid-plate, frame, and truss types. The objectives of this study using parametric study were to evaluate the appropriate stiffness ratio of intermediate diaphragms and then to propose the effective spacing and numbers of intermediate diaphragms based on the evaluated stiffness ratio. Target bridges for this study were straight continuous span bridges with a single-cell steel box section. The parameters for the parametric study were the shape of box section, the span numbers, the equivalent span length, the stiffness of intermediate diaphragms, and the spacing of intermediate diaphragms. From the results of the parametric study, the effective spacing and numbers as well as the stiffness ratio of the intermediate diaphragms will be presented.

A study of Improvement of Stiffness for Plastic PET bottle with Different Geometries and Numbers of Rib (리브 형상 및 개수에 따른 사각플라스틱 페트병의 강성보강에 관한 연구)

  • Young-Hoon Lee;Bum-Jin Park;Eui-Chul Jung;Jung-Gil Oh;Seok-Guwan Hong
    • Design & Manufacturing
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    • v.17 no.4
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    • pp.33-41
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    • 2023
  • Excessive use of plastic bottles contributes to a significant environmental issue due to the high volume of plastic waste generated. To address this, efforts are needed to reduce the weight of plastic bottles. However, indiscriminate weight reduction may compromise the essential rigidity required for plastic bottles. Extensive research on rib shape for pressure vessels are exists, but there is a few research of rib shapes to enhance the stiffness of plastic bottles. The following results were obtained from the analyses conducted in this study. 1) Among the rib cross-sections of square, trapezoid, and triangle, the buckling critical load of PET bottles with square-shaped ribs is improved by about 14% compared to the buckling critical load of PET bottles without ribs. 2) The buckling critical load is improved by about 18% when a square-shaped rib with an aspect ratio of 0.2 is applied, compared to the buckling critical load of the bottle without the rib. 3) When longitudinal and transverse square ribs were applied to the axial direction of the PET bottle, the buckling critical load was improved by about 32% and 58% compared to the buckling critical load of the PET bottle without ribs, respectively, indicating that applying longitudinal ribs is effective in reinforcing the stiffness of PET bottles. 4) When 14 transverse ribs were applied, the maximum improvement was about 48% compared to the buckling critical load of the plastic bottle without ribs. 5) When 3 longitudinal ribs were applied on each side, the maximum improvement was about 76% compared to the buckling critical load of the bottle without ribs. Therefore, it was concluded that for effective stiffness reinforcement of a 500ml square bottle with a thickness of 0.5mm, 3 square-shaped ribs with an aspect ratio of 0.2 should be applied in the longitudinal direction relative to the axial direction of the bottle.

A Study on the Changing Pattern of the Petiole's Vascular Branch of Some Acer Species (단풍나무속(屬) 수종(數種)의 엽병(葉柄) 유관속지(維管束枝) 변화형(變化型)에 관한 연구(硏究))

  • Park, Kwang Woo;Kim, Sam Shik
    • Journal of Korean Society of Forest Science
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    • v.73 no.1
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    • pp.21-32
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    • 1986
  • This study was done to classify 15 species in the genus Acer through tracking of the changing shape of the vascular branch from the base part to the terminal part of petiole by the anatomical method. The basic vascular branches were 3 ea, except A. mandshuricum 3-4 ea. The vascular bundle was separated, moved and connected from the base part to the terminal part of petiol, the number of separated vascular branch was 11-32 ea., the number of connected vascular branch was 0-17 ea., and the ratio of the separated vascular branch to the connected was 0.00-8.00. The maximum number of vascular branch in No, 39 of cross section part was observed in 12 species; A. ginnala and A. buergerianum were No. 11, A. truncatum and A. platanoides were No. 13, A. saccharium was No. 26. The number of the connected vascular branches with the main vascular branch were 0-6, while the number of the separated vascular branch were 0-7. On the ratio of separation to connection of the base vascular branch; "A", "B" and "C", the symmetrical shapes on the basis of "B" were A>BC, AB>C shape. The classical groups by the development of main vascular branch formation were obtained 7 groups of "a" through "g" shape. Especially, A. negundo and A. saccharinum were shown to have central vascular branches with unique changing patterns.

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Optimum Design of Cross Section Lateral Damper Oil Seals for High Speed Railway Vehicle (고속 철도 차량 횡댐퍼 오일 씰의 형상 단면 최적설계)

  • Hwang, Ji-Hwan;Kim, Chul-Su
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.18 no.1
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    • pp.579-584
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    • 2017
  • The damper oil seal of a high-speed railway vehicle is made from nitrile butadiene rubber (NBR) in order to prevent lubricant from leaking into the damper and to stop harmful contaminants from entering the external environment while in service. Oil leakage through the seal primarily occurs from fatigue failure of the damper. Cumulative damage of the seal occurs due to the contact force between the rod and the rubber during movement due to track irregularities and cants, among other factors. Thus, the design of the oil seal should minimize the maximum principal strain at weak points. In this study, the optimal cross section of the damper oil seal was found using the multi-island genetic algorithm method to improve the durability of the damper. The optimal shape of the oil seal was derived using process automation and design optimization software. Nonlinear material properties for finite element analysis (FEA) of the rubber were determined by Marlow's model. The nonlinear FEA confirmed that the maximum principal strain at the oil leakage point was decreased 24% between the initial design and the optimum design.

Study on the effect of cable on the lateral behavior of S-shaped Pedestrian-CSB (S형 보도사장교의 케이블이 횡방향 거동에 미치는 영향 연구)

  • Ji, Seon-Geun;Yhim, Sung-Soon
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.20 no.5
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    • pp.577-584
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    • 2019
  • Recently, CSB(Cable-Stayed Bridge) have been attempted to be atypical forms for landscape elements in Korea. CSB with new geometry need to analyze their characteristics clearly to ensure structural safety. This study's bridge is the S-shaped curved pedestrian CSB that has a girder with S-shape plane curve and reverse triangular truss cross section, inclined independent pylon, modified Fan type main cable and vertical backstay cable. Curved CSB can have excessive lateral displacement and moment when the tension is adjusted, focusing only on longitudinal behavior, such as a straight CSB. In order to analyze the effect of the cable on the lateral behavior of bridges, the cable is divided into two groups according to the lateral displacement direction of the pylon due to tension. The influence of the combination ratio of GR1 and GR2 on the girder, bearing, pylon, and vertical anchor cable was analyzed. When the tension applied to the bridge is 1.0GR1 plus 1.0GR2, In the combination of 1.2GR1 plus 0.8GR2, the stress on the left and right upper member of the truss girder and the deviation of the both were minimized. In addition, the horizontal force of the bearing, the lateral displacement and moment of the pylon, and the tension of the vertical backstay cable also decreased. This study is expected to be used as basic data for determination of tension of CSB with similar geometry.