• Title/Summary/Keyword: Geometrical Shape

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Shape Optimization of the Plane Truss Structures with the Statical and Natural Frequency Constraints (정적(靜的) 및 고유진동수(固有振動數) 제약조건식(制約條件式)을 고려(考慮)한 평면(平面) 트러스 구조물(構造物)의 형상최적화(形狀最適化)에 관(關)한 연구(硏究))

  • Lee, Gyu Won;Lee, Gun Tea
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.10 no.2
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    • pp.23-38
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    • 1990
  • In this study, decompositive optimization method of two levels was selected to optimize effectively the geometry of the truss which takes the multi-loading condition, and the allowable stress, bucking stress, displacement and natural frequency constraints into consideration. The algorithm of this study is made up of sectional optimization using the feasible direction method in level 1, and geometrical optimization employing Powell's one-direction search method which menimizes only objictive function in level 2. The results of this study acquired by beenning applied to structural model of the truss are as follows : 1. It is verified that the algorithm of this study effectively converges, independent of the initial geometry of the truss and the applied various constraints. 2. The optimum goemetry of the truss varies more considerably according to the constraints selected. 3. Under the condition of the same design, the weight of the truss can be decreased more considerably by means of optimizing even the geometry of truss than by means of optimizing the section of truss while fixing geometrical configuration of it, even though there might be a little difference according to the initial geometry of the truss and the design condition.

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Study on the Meaning of Four Subjects and Four Species as a Disease-Prediction Data and Diagnostic Value on Ante-Disease (질병예측자료로서 사과(四科) . 사류형상(四類形象)의 의의와 미병진단적 가치 연구)

  • Kim, Jong-Won;Jeon, Soo-Hyung;Lee, In-Seon;Kim, Kyu-Kon;Lee, Yong-Tae;Kim, Kyung-Chul;Eom, Hyun-Sup;Chi, Gyoo-Yong
    • Journal of Physiology & Pathology in Korean Medicine
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    • v.23 no.2
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    • pp.325-330
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    • 2009
  • In Korea, medical diagnostic equipments and biochemical examination can not be used in order for diagnosing sub-healthy state or ante-disease state in oriental medicine clinic. So morphic analogical method used in oriental medicine can be a good tool as a disease-predictable signs in order to enable preventive diagnosis and therapy. Therefore the four geometrical subjects; Essence, Pneuma, Spirit, Blood(四科;精氣紳血) and the four taxonomical species; Pisces, Quadruped, Aves, Carapaces(四類;魚走鳥甲) are chosen as morphic models in this paper. The differences of two classifying methods with four subjects and four species were as follows. The diagnostic category was meta-medical and synthetic against medical specific. The diagnostic object was body in contrast with face. They were able to be applicant in psychology and classification of characteristics against diagnostics and therapeutics directly in oriental medicine. The theoretical basis was basic diagrams of four unit-fluids of body and morphological analogy with four animal species respectively. And the therapeutic aims were systemic pathogenesis following five phase theory against congestion and deficiency of Essence, Pneuma, Spirit, Blood. The four subjects and four species are mixed each other practically in clinic. But it should be used limitedly because of the above reasons described and must divide the principal and secondary factors and follow the pathology of principal shape factor. In order to improve the diagnostic value of ante-disease state, the discriminable standards, measurement methods, limit of interrelating interpretation and the criteria of abnormal disproportion were needed to be defined more clearly in advance.

The Effects of Tunnel Geometrical Characteristics and Canopy Installation on the Ventilation and Fire Propagation (터널의 기하학적 형태 및 캐노피 설치가 터널 환기 및 화재 확산에 미치는 영향 분석)

  • Lee, Chang-Woo;Suh, Ki-Yoon;Kim, Jung-Wook
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.8 no.4
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    • pp.325-334
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    • 2006
  • Understanding the airflow characteristics within the canopy structure installed between closely adjacent tunnels either for light adaptation or for protection from snow hazards is required for the normal ventilation as well as safety system design. Grade, horizontal alignment, cross-sectional area and shape are known to substantially influence the fire smoke behavior and their influences raise great concern for the safety design. This paper aims at studying the effects of tunnel geometrical characteristics and canopy installation on the ventilation and fire propagation through CFD analysis. In the case of 145m long canopy, 50% opening ratio is preferred with respect to the airflow pattern and ventilation efficiency. When a 20MW fire occurs in a 1.8km-long tunnel and four 1250mm reversible jet fans are instantly turned on, smoke concentration at 40m downstream of the fire decrease 13% for the upgrade tunnel with 2% gradient and increases 20% for -2% gradient, compared to the standard horizontal tunnel. Backlayering is observed within 45m-long segment toward the entrance in 2% down-graded tunnel. In a rectangular tunnel, there is no significant difference of smoke concentration as well as velocity profile from the standard crown tunnel. Three-laned tunnel shows lower level of both profiles and backlayering is detected up to 50m upstream of the fire, while the risky situation rapidly disappears thereafter.

Vibration and Impact Transmission for each Variable of Woodpile Metamaterial (우드파일 메타물질의 변수 별 진동 및 충격에 끼치는 영향)

  • Ha, Young sun;Hwang, Hui Y.;Cheon, Seong S.
    • Composites Research
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    • v.34 no.3
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    • pp.155-160
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    • 2021
  • Metamaterials are complexes of elements that can create properties not found in naturally occurring materials, such as changing the direction of forces, creating negative stiffness, or altering vibration and impact properties. In the case of wood pile metamaterials that are easy to manufacture and have excellent performance in reducing vibration and shock in the vertical direction, basic research on variables affecting shock transmission is needed to reduce shock. Although research on impact reduction according to geometrical factors is being conducted recently, studies on the effect of material variables on impact reduction are insufficient. In this paper, finite element analysis was carried out by variablizing the geometrical properties (lamination angle, diameter, length) and material properties (modulus of elasticity, specific gravity, Poisson's ratio) of wood pile cylinders. Through finite element analysis, the shape of the wooden pile cylinder delivering impact was confirmed, and the effect of each variable on the reduction of impact force and energy was considered through main effect diagram analysis, and frequency band analysis was performed through fast Fourier transform. proceeded In order to reduce the impact force and vibration, it was found that the variables affecting the contact area of t he cylinder have a significant effect.

Effect of different pattern size and pattern shape on castability of commercially pure titanium (납형의 크기와 형태가 티타늄의 주조성에 미치는 영향)

  • Seo, Yoon-Jeong;Oh, Gye-Jeong;Lee, Hyo-Il;Shin, Yoo-Jin;Kim, Hong-Joo;Park, Sang-Won
    • The Journal of Korean Academy of Prosthodontics
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    • v.51 no.4
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    • pp.261-268
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    • 2013
  • Purpose: The purpose of this study was to investigate the effect of geometrically different wax pattern shapes and sizes on the castability of Grade2 Cp-Ti (commercially pure titanium). Materials and methods: Total of 40 mesh wax pattern ($61mm{\times}24mm$, 207 grids), ($61mm{\times}17mm$, 138 grids) was cast in this experiment. Depending on the geometrical shape of the wax pattern, 8 groups was organized; Flat, Semicircular, Horse-shoe and V-shape, each consisting 5 samples. Runner-bar sprue was used in all patterns. The number of completely cast grid in wax pattern served as a measure for the castability of comercially pure titanium. Results: The mean value of square count in each group was as followed; 133.20 squares in group SS (96.52%), 132.40 squares in group SH (95.94%), 132.00 squares in group SF (95.65%), 127.60 squares in SV (91.43%), 198.60 squares in group LF (95.94%), 197.80 squares in group LV (95.56%), 196.40 squares in group LS (94.88%), and 188.00 squares in group LH (90.82%). Conclusion: Within the limitations of this study the results indicate that there were no sttistically significant difference in castability of titanium regarding wax pattern shape (P>.05). However, Small size wax patterns were showing the noticeable castability more than Large size pattern.

A Study on Soviet Constructive Fashion in 1920s (1920년대 소비에트 구성주의 패션에 관한 연구)

  • 조윤경;금기숙
    • Journal of the Korean Society of Costume
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    • v.36
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    • pp.183-203
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    • 1998
  • The wave of Avant-garde swept away all in the unique social background so called 'October Revolution' and the early 1900 Russian society which was able to absorb and accept anything. The Russian avant-garde has been affected by the Cubism and the Futurism those had peculiarly appeared in the early twentieth century, spreaded out to three spheres: the Suprematism, the Rayonism and the Constructivism. The Russian Constructivism has appeared in this background, concretely and ideally ex-pressed the ideology of the revolution into the artistic form and made an huge influence to the whole Russian society. The Constructivist like Tatlin, naum Gabo, Pevaner, Rodchenko, Stepanova, Popova and Exter gave great effect on the Soviet Constructive fashion design in 1920's after the Revolution. The Soviet costume in 1920s hold in common the characteristicss of the Constructive graphic as it is, geometrical and abstractive form, energetic and motility. In fashion design, these graphic qualities have been showed as the application of geometrical form and architectural image, physical distortion and transformation. And in textile design, the simple, dynamical presentation has been appeared. We can classify the Soviet costume at this time into three occasions. The first term is from late 1910 th mid 1920, and it is altered from folk costume design to modern one. With Lamanova as the first on the list, using the folk mitif, the Constructive expression of simple form has been gradually revealed in design. Designers like Makarova, Pribylskaia and Mukhina produced the plane, simple chemise style with the decoration of the Russian traditional motif. From early to late 1920 is the second term, and it is at the pick of the most active processing of the Constructive design. Not only at the costume in daily life but also at the theatrical costume and textile, the con-structive design has been represented all avail-able fields. Many Constructivists including Stepanova, Popova, Exter and Rodchenko took part in the textile design and costume design so as to evlvo their aesthetic concept. The third term is from late 1920 to early 1930. The socialistic realism has dominated over the whole culture and art, the revolutionary dynamic motif has been presented also in textile design. The formative features of Soviet Constructive fashion design are; silhouette, from, motif, color and fabric. The first, the silhouette : a straight rectangular silhouetted has been expressed through the whole period and a volumed one with distorted human body shape has introduced in the theatrical costume design. The second, the form: many lengthened rectangular forms have been made at beginnings, but to the middle period, geometrical, architectural forms have been more showed and there are energy and movement in design. At the last period, only a partial feature-division has been seen. The third, the motif; no pattern or ethnic motif has been partly used at beginnings, a figure like circle, tri-angle has gradually appeared in textile design. At latter period, a real-existent motif like an airplane has been represented with graphing and simplicity. The fourth, the color ; because of insufficient dyeing, neutral color like black or grey color has been mainly covered, but after middle term, a primary color or pastel tone has been seen, contrast of the fabric; without much development of textile industry after the Revolution, thick and durable fabrics have been the main stream, but as time had going to the last period, fabrics such as linen, cotton, velvet and silk have been varously choesn. At the theatrical costume, new materials like plastics and metals that were able to accentuate the form. The pursuit of popularity, simplicity and functionalism that the basic concept of Constructive fashion is one of the "beauty" which has been searching in modern fashion. And now we can appreciate how innovative and epochal this Soviet Constructive fashion movement was.ement was.

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STL Generation in Reverse Engineering by Delaunay Triangulation (역공학에서의 Delaunay 삼각형 분할에 의한 STL 파일 생성)

  • Lee, Seok-Hui;Kim, Ho-Chan;Heo, Seong-Min
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.26 no.5
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    • pp.803-812
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    • 2002
  • Reverse engineering has been widely used for the shape reconstruction of an object without CAD data and the measurement of clay or wood models for the development of new products. To generate a surface from measured points by a laser scanner, typical steps include the scanning of a clay or wood model and the generation of manufacturing data like STL file. A laser scanner has a great potential to get geometrical data of a model for its fast measuring speed and higher precision. The data from a laser scanner are composed of many line stripes of points. A new approach to remove point data with Delaunay triangulation is introduced to deal with problems during reverse engineering process. The selection of group of triangles to be triangulated based on the angle between triangles is used for robust and reliable implementation of Delaunay triangulation as preliminary steps. Developed software enables the user to specify the criteria for the selection of group of triangles either by the angle between triangles or the percentage of triangles reduced. The time and error for handling point data during modelling process can be reduced and thus RP models with accuracy will be helpful to automated process.

CNT-BASED FIELD EMISSION X-RAY SOURCE

  • Kim, Hyun Suk;Lee, Choong Hun
    • Proceedings of the Korean Vacuum Society Conference
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    • 2016.02a
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    • pp.433-433
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    • 2016
  • Carbon nanotubes (CNT) emitter has widely become an attractive mechanism that draws growing interests for cold cathode field emission. CNT yarns have demonstrated its potential as excellent field emitters. It was demonstrated that a small focal spot size was achieved by manipulating some electrical parameters, such as applied bias voltage at the mesh gate, and electrostatic focal lenses, geometrical parameters, such as axial distances of the anode, and the electrostatic focal lens from the cathode assembly, and the dimension of the opening of the electrostatic lens. Electrical-optics software was used to systematically investigate the behavior of the electron beam trajectory when the aforementioned variables were manipulated. The results of the experiment agree with the theoretical simulation results. Each variable has an individual effect on the electron beam focal spot size impinging on the target anode. An optimum condition of the parameters was obtained producing good quality of X-ray images. Also, MWCNT yarn was investigated for field emission characteristics and its contribution in the X-ray generation. The dry spinning method was used to fabricate MWCNT yarn from super MWCNTs, which was fabricated by MW-PECVD. The MWCNT yarn has a significant field emission capability in both diode and the triode X-ray generation structure compared to a MWCNT. The low-voltage-field emission of the MWCNT yarn can be attributed to the field enhancing effect of the yarn due to its shape and the contribution of the high-aspect-ratio nanotubes that protrude from the sides of the yarn. Observations of the use of filters on the development of X-ray images were also demonstrated. The amount of exposure time of the samples to the X-ray was also manipulated. The MWCNT yarn can be a good candidate for use in the low voltage field emission application of X-ray imaging.

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Numerical simulation of hollow steel profiles for lightweight concrete sandwich panels

  • Brunesi, E.;Nascimbene, R.;Deyanova, M.;Pagani, C.;Zambelli, S.
    • Computers and Concrete
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    • v.15 no.6
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    • pp.951-972
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    • 2015
  • The focus of the present study is to investigate both local and global behaviour of a precast concrete sandwich panel. The selected prototype consists of two reinforced concrete layers coupled by a system of cold-drawn steel profiles and one intermediate layer of insulating material. High-definition nonlinear finite element (FE) models, based on 3D brick and 2D interface elements, are used to assess the capacity of this technology under shear, tension and compression. Geometrical nonlinearities are accounted via large displacement-large strain formulation, whilst material nonlinearities are included, in the series of simulations, by means of Von Mises yielding criterion for steel elements and a classical total strain crack model for concrete; a bond-slip constitutive law is additionally adopted to reproduce steel profile-concrete layer interaction. First, constitutive models are calibrated on the basis of preliminary pull and pull-out tests for steel and concrete, respectively. Geometrically and materially nonlinear FE simulations are performed, in compliance with experimental tests, to validate the proposed modeling approach and characterize shear, compressive and tensile response of this system, in terms of global capacity curves and local stress/strain distributions. Based on these experimental and numerical data, the structural performance is then quantified under various loading conditions, aimed to reproduce the behaviour of this solution during production, transport, construction and service conditions.

Production Mechanism of Residual Stress Generated by Multi-Pass Welding of the steel Pipe (강관 적층용접부 잔류응력의 생성기구)

  • Chang, Kyong Ho;Yang, Sung Chul;Kang, Jae Hoon
    • Journal of Korean Society of Steel Construction
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    • v.13 no.4
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    • pp.327-335
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    • 2001
  • The characteristics and production mechanism of residual stress generated by multi-pass welding of the steel pipe were elucidated from the results of three-dimensional thermal elastic-plastic FEM analysis. When the steel pipe was jointed by multi-pass welding, the stress components of circumferential direction and radial direction near welded joints on the inner surface and the outer surface of the pope were tensile. The stress component of axial direction on the inner surface was tensile and on the outer surface was compressive. On the other hands, the production mechanism of residual stress generated by multi-pass welding of the steel pipe was investigated. Residual stress generated by welding of the steel pipe was investigated not only by the thermal history but also by geometrical shape. Then, the generality of the production mechanism of residual stress generated by multi-pass welding was confirmed.

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