A Method of Form Selection for Large Scale Structures

2002 ◽  
Author(s):  
Damiano Pasini ◽  
S. C. Burgess ◽  
D. J. Smith
Keyword(s):  
Cross Sections ◽  
Large Scale ◽  
Design Parameters ◽  
Cross Sectional ◽  
Geometrical Properties ◽  
Large Scale Structures ◽  
Shape Selection ◽  
Efficiency Parameter ◽  
Sectional Shape ◽  
Selection Of

This paper presents a new method for modelling the efficiency of large-scale structural forms. Parametric equations, which include all design parameters and also the effect of buckling, are developed. Shape transformers, envelope efficiency parameter and scaling factor are introduced to describe the geometrical properties of cross-sections and to allow interaction between form and cross-sectional shape selection. Design charts provide insight and understanding and assist the selection of different structural concepts at the preliminary stage of design.

Design of C-Frames Using Real-Coded Genetic Optimization Algorithms and NURBS

1999 ◽  
Author(s):  
Ashraf O. Nassef ◽  
Hesham A. Hegazi ◽  
Sayed M. Metwalli
Keyword(s):  
Genetic Algorithms ◽  
Cross Section ◽  
Cross Sections ◽  
Design Parameters ◽  
Binary Representation ◽  
Cross Sectional ◽  
Search Spaces ◽  
The Cross ◽  
Sectional Shape ◽  
Real Coded Genetic Algorithms

Abstract C-frames constitute a large portion of machine tools that are currently used in industry. Examples of these frames include drilling machines, presses, punching and stamping machines, clamps, hooks, etc. The design parameters of these frames include the dimensions of their cross-sections, which should be chosen to withstand the applied loads and minimize the element’s overall weight. Traditionally, the cross-section of C-frame belonged to a set of primitive shapes, which included I, T, trapezoidal and rectangular sections. This paper introduces a new methodology for designing the frame’s cross-section. The cross-sectional shape is represented using non-uniform rational B-Spline (NURBS) in order to give it a form of shape flexibility. A special form of genetic algorithms known as real-coded genetic algorithms is used to conduct the search for the design objectives. Real-coded genetic algorithms are known to outperform the simple binary representation genetic algorithms when dealing with continuous search spaces. The results showed that the optimal shape was a semi I/T-section with the material bulk related to the applied load.

Structural efficiency maps for beams subjected to bending

2003 ◽  
Vol 217 (3) ◽  
pp. 207-220 ◽  
Author(s):  
D Pasini ◽  
D J Smith ◽  
S C Burgess
Keyword(s):  
Cross Sections ◽  
Neutral Axis ◽  
The Other ◽  
Limit Curve ◽  
Cross Sectional ◽  
Structural Efficiency ◽  
Relative Ratio ◽  
Efficiency Parameter ◽  
Efficiency Map ◽  
Sectional Shape

The structural efficiency of different cross-sections subjected to bending is considered in this paper. An envelope efficiency parameter, λ, is defined in terms of two shape transformers, A and 1. These transformers describe the relative ratio of the area and the second moment of area of the cross-sectional shape with respect to a rectangular envelope surrounding the shape. It is shown in a structural efficiency map that the mass efficiency of all cross-sectional shapes subjected to bending is bounded by two limiting curves. One limit curve represents cross-sections with material as far as possible from the neutral axis, the other limit curve is for cross-sections with material close to the neutral axis. The application of the map to two practical cases is also considered, together with scaling of the rectangular envelope.

Automated 3D measurement of fiber cross section morphology in handsheets

2012 ◽  
Vol 27 (2) ◽  
pp. 264-269 ◽  
Author(s):  
Christian Lorbach ◽  
Ulrich Hirn ◽  
Johannes Kritzinger ◽  
Wolfgang Bauer
Keyword(s):  
Image Analysis ◽  
Cross Section ◽  
Cross Sections ◽  
Image Plane ◽  
3D Measurement ◽  
Cross Sectional ◽  
Fiber Cross Section ◽  
Fiber Wall ◽  
Sectional Shape ◽  
Cross Section Geometry

Abstract We present a method for 3D measurement of fiber cross sectional morphology from handsheets. An automated procedure is used to acquire 3D datasets of fiber cross sectional images using an automated microtome and light microscopy. The fiber cross section geometry is extracted using digital image analysis. Simple sample preparation and highly automated image acquisition and image analysis are providing an efficient tool to analyze large samples. It is demonstrated that if fibers are tilted towards the image plane the images of fiber cross sections are always larger than the true fiber cross section geometry. In our analysis the tilting angles of the fibers to the image plane are measured. The resulting fiber cross sectional images are distorted to compensate the error due to fiber tilt, restoring the true fiber cross sectional shape. We use an approximated correction, the paper provides error estimates of the approximation. Measurement results for fiber wall thickness, fiber coarseness and fiber collapse are presented for one hardwood and one softwood pulp.

Simulation of Flow Field on a Large Scale Wind Turbine

2008 ◽  
Author(s):  
I. Janajreh ◽  
C. Ghenai
Keyword(s):  
Flow Field ◽  
Wind Energy ◽  
Wind Turbine ◽  
Wind Turbines ◽  
Cross Sections ◽  
Large Scale ◽  
Wind Farms ◽  
Operating Characteristics ◽  
Cross Sectional ◽  
Capital Costs

Large scale wind turbines and wind farms continue to evolve mounting 94.1GW of the electrical grid capacity in 2007 and expected to reach 160.0GW in 2010 according to World Wind Energy Association. They commence to play a vital role in the quest for renewable and sustainable energy. They are impressive structures of human responsiveness to, and awareness of, the depleting fossil fuel resources. Early generation wind turbines (windmills) were used as kinetic energy transformers and today generate 1/5 of the Denmark’s electricity and planned to double the current German grid capacity by reaching 12.5% by year 2010. Wind energy is plentiful (72 TW is estimated to be commercially viable) and clean while their intensive capital costs and maintenance fees still bar their widespread deployment in the developing world. Additionally, there are technological challenges in the rotor operating characteristics, fatigue load, and noise in meeting reliability and safety standards. Newer inventions, e.g., downstream wind turbines and flapping rotor blades, are sought to absorb a larger portion of the cost attributable to unrestrained lower cost yaw mechanisms, reduction in the moving parts, and noise reduction thereby reducing maintenance. In this work, numerical analysis of the downstream wind turbine blade is conducted. In particular, the interaction between the tower and the rotor passage is investigated. Circular cross sectional tower and aerofoil shapes are considered in a staggered configuration and under cross-stream motion. The resulting blade static pressure and aerodynamic forces are investigated at different incident wind angles and wind speeds. Comparison of the flow field results against the conventional upstream wind turbine is also conducted. The wind flow is considered to be transient, incompressible, viscous Navier-Stokes and turbulent. The k-ε model is utilized as the turbulence closure. The passage of the rotor blade is governed by ALE and is represented numerically as a sliding mesh against the upstream fixed tower domain. Both the blade and tower cross sections are padded with a boundary layer mesh to accurately capture the viscous forces while several levels of refinement were implemented throughout the domain to assess and avoid the mesh dependence.

scholarly journals On the effect of cross sectional shape on incipient motion and deposition of sediments in fixed bed channels

2014 ◽  
Vol 62 (1) ◽  
pp. 75-81 ◽  
Author(s):  
Mir-Jafar-Sadegh Safari ◽  
Mirali Mohammadi ◽  
Golezar Gilanizadehdizaj
Keyword(s):  
Cross Sections ◽  
Research Work ◽  
Fixed Bed ◽  
Deposition Condition ◽  
Incipient Motion ◽  
Rigid Boundary ◽  
Cross Sectional ◽  
Motion Equations ◽  
Sectional Shape ◽  
Minimum Velocity

Abstract The condition of incipient motion and deposition are of the essential issues for the study of sediment transport. This phenomenon is of great importance to hydraulic engineers for designing sewers, drainage, as well as other rigid boundary channels. This is a study carried out with the objectives of describing the effect of cross-sectional shape on incipient motion and deposition of particles in rigid boundary channels. In this research work, the experimental data given by Loveless (1992) and Mohammadi (2005) are used. On the basis of the critical velocity approach, a new incipient motion equation for a V-shaped bottom channel and incipient deposition of sediment particles equations for rigid boundary channels having circular, rectangular, and U-shaped cross sections are obtained. New equations were compared to the other incipient motion equations. The result shows that the cross-sectional shape is an important factor for defining the minimum velocity for no-deposit particles. This study also distinguishes incipient motion of particles from incipient deposition for particles. The results may be useful for designing fixed bed channels with a limited deposition condition.

Enamel Crystal Shape: History of an Idea

1987 ◽  
Vol 1 (2) ◽  
pp. 322-329 ◽  
Author(s):  
H. Warshawsky
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Cross Sections ◽  
Three Dimensional ◽  
Unit Cell ◽  
Cross Sectional ◽  
Transmission Electron ◽  
History Of ◽  
Sectional Shape ◽  
Imaging Plane

The purpose of this paper is to review evidence which casts doubt on the interpretation universally applied to hexagonal images seen in sectioned enamel. The evidence is based on two possible models to explain the hexagonal profiles seen in mammalian enamel with transmission electron microscopy. The "hexagonal ribbon" model proposes that hexagonal profiles are true cross-sections of elongated hexagonal ribbons. The "rectangular ribbon" model proposes that hexagonal profiles are caused by three-dimensional segments that are parallelepipeds contained in the Epon section. Since shadow projections of such rectangular segments give angles that are inconsistent with the hexagonal unit cell, a model based on ribbons with rhomboidal cut ends and angles of 60 and 120° is proposed. The "rhomboidal ribbon" model projects shadows with angles that are predicted by the unit cell. It is suggested that segments of such crystallites in section project as opaque hexagons on the imaging plane in routine transmission electron microscopy. Morphological observations on crystallites in sections - together with predictions from the hexagonal, rectangular, and rhomboidal ribbon models - indicate that crystallites in rat incisor enamel are flat ribbons with rhomboidal cross-sectional shape. Hexagonal images in electron micrographs of thin-sectioned enamel can result from rhomboidal-ended, parallelepiped-shaped segments of these crystallites projected and viewed as two-dimensional shadows.

scholarly journals Parameterization of subgrid plume dilution for use in large-scale atmospheric simulations

2010 ◽  
Vol 10 (5) ◽  
pp. 2551-2560 ◽  
Author(s):  
A. D. Naiman ◽  
S. K. Lele ◽  
J. T. Wilkerson ◽  
M. Z. Jacobson
Keyword(s):  
Large Scale ◽  
Climate Model ◽  
Global Climate ◽  
Global Climate Model ◽  
Cross Sectional ◽  
Plume Dynamics ◽  
Eddy Simulation ◽  
Subgrid Model ◽  
Diffusion Parameters ◽  
Sectional Shape

Abstract. A new model of plume dynamics has been developed for use as a subgrid model of plume dilution in a large-scale atmospheric simulation. The model uses mean wind, shear, and diffusion parameters derived from the local large-scale variables to advance the plume cross-sectional shape and area in time. Comparisons with a large eddy simulation of aircraft emission plume dynamics, with an analytical solution to the dynamics of a sheared Gaussian plume, and with measurements of aircraft exhaust plume dilution at cruise altitude show good agreement with these previous studies. We argue that the model also provides a reasonable approximation of line-shaped contrail dilution and give an example of how it can be applied in a global climate model.

Effects of Some Design Parameters on the Static Performance of the Truss String Structure

2011 ◽  
Vol 255-260 ◽  
pp. 215-219
Author(s):  
Cheng Wei Huang ◽  
Rui Shao ◽  
De Li Zhang
Keyword(s):  
Finite Element ◽  
Tensile Properties ◽  
High Strength ◽  
Design Parameters ◽  
Sectional Area ◽  
Cross Sectional ◽  
Static Performance ◽  
String Structure ◽  
Element Theory ◽  
Selection Of

The beam string structure，a new self-balancing system is a combination of a string (Cable), pole and beam-column (beam, arch). Because the beam string structure make full use of tensile properties of high-strength cord, force became more reasonable, transportation became more convenient and construction became more simple for the new self-balancing system. The beam string structure became a new structure with a good value and prospects. In this paper the effects of the static performance of the single truss string structure are researched through analyzing the influence of prestressed cable, pole pitch, blow-span ratio of cable and cross-sectional area of cable using of finite element theory. The results of the reasonable selection of string truss design parameters a valuable reference.

scholarly journals Direct-Write Photolithography for Cylindrical Tooling Fabrication in Roll-to-Roll Microcontact Printing

2015 ◽  
Vol 3 (3) ◽  
Author(s):  
Larissa F. Nietner ◽  
David E. Hardt
Keyword(s):  
Large Scale ◽  
Microcontact Printing ◽  
Scale Up ◽  
Surface Patterning ◽  
Direct Write ◽  
Cross Sectional ◽  
Control Factors ◽  
Roll To Roll ◽  
Sectional Shape ◽  
Scale Surface

The scale-up of microcontact printing (μCP) to a roll-to-roll technique for large-scale surface patterning requires scalable tooling for continuous pattern printing with μm-scale features (e.g., 1–50 μm). Here, we examine the process of creating such a tool using an optical direct-write or “maskless” method working on a rotating cylindrical substrate. A predictive model of pattern formation is presented along with experimental results to examine the key control factors for this process. It is shown that factors can be modulated to vary the cross-sectional shape in addition to feature height and width. This feature can then be exploited to improve the robustness of the final printing process.

scholarly journals Influence of the volute cross-sectional shape on mixed inflow turbine performances

2017 ◽  
Vol 9 (7) ◽  
pp. 168781401770817 ◽  
Author(s):  
Mohamed Amine Meghnine ◽  
Mohammad Kamal Hamidou ◽  
Mohammed Hamel
Keyword(s):  
Cross Sections ◽  
Radial Direction ◽  
Essential Element ◽  
Sectional Area ◽  
Cross Sectional ◽  
Flow Angle ◽  
Absolute Flow ◽  
Subsonic Regime ◽  
Simulation Results ◽  
Sectional Shape

The volute is an essential element in the centrifugal machines. Improving its performance is an effective way to improve the total performance of the turbine. The purpose of this study is to replace the accelerating and guiding nozzle vanes by exploring different design possibilities on the cross-sectional area convergence of the volute, since a decreasing area is then associated with expansion in the subsonic regime. The work is extended to a mixed inflow turbine using the new volute cross sections under pulsating regimes for turbocharging. The numerical simulation results show larger accelerations [Formula: see text] and lesser losses in the case of sections with flatter area in the radial direction and without vaneless space between the volute and the rotor; but this combination has an effect on the exit absolute flow angle which is less uniform.

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