scholarly journals Vortex excitation of tower-like structures of circular cross-sections.

2007 ◽  
Vol 1 (1) ◽  
pp. 119-143
Author(s):  
Tomasz Lipecki
Keyword(s):  
Mathematical Model ◽  
Cross Sections ◽  
Lateral Displacement ◽  
Theoretical Background ◽  
Lateral Vibrations ◽  
Lateral Response ◽  
Analysis Of Results ◽  
Lateral Displacements ◽  
Corrosion Of Steel

The paper deals with the description of vortex excitation phenomenon in cases of structures of circular cross-sections. Other sources of across-wind load (fluctuations of wind direction or aerodynamic interference) are neglected in this paper. The main aim of this paper is presentation of a theoretical background of a new mathematical model of critical vortex excitation of slender structures of circular cross-sections. All calculations have been performed using own computer programme according to numerical implementation of mathematical model. That programme allows to simulate across-wind action caused by vortices as well as a lateral response of the analysed structure. Simulations of vortex excitation are performed in real time on the basis of lateral displacements. Sensitivity analysis of results has been carried out for the purpose of determination of the importance of particular parameters describing mathematical model for lateral displacement of analysed structures. Final results concerning maximum lateral top displacements of the structures obtained according to the new model have been compared with available full-scale data for steel and concrete chimneys. Maximum lateral top displacements have been also compared with results obtained according to procedures included in codes and standards. Moreover, additional aspects of vortex excitation are presented: the influence of corrosion of steel chimneys and the influence of feedbacks between vortex shedding and lateral vibrations on lateral response of analysed structures.

Optimization Design of Single Steering Trapezoid Mechanism of Vehicle Based on MATLAB

2012 ◽  
Vol 490-495 ◽  
pp. 2499-2504
Author(s):  
Ai Hua Ren ◽  
Chuan Qiong Sun
Keyword(s):  
Mathematical Model ◽  
Sensitivity Analysis ◽  
Optimization Design ◽  
Research Direction ◽  
Selection Of Variables ◽  
Analysis Of Results ◽  
Actual Operation ◽  
Matlab Programming ◽  
Selection Of

Firstly the optimum mathematical model of single steering trapezoid mechanism of vehicle was established gradually through selection of variables, setting constraints, determination of objective function. And then the optimum calculation is carried out with MATLAB programming in the case of EQ1092, and the problem occurring in actual operation that the optimum results changed with initial points was solved. In the end the further optimum research direction of this mechanism was intuitively pointed out through visualization and sensitivity analysis of results.

scholarly journals Measurement of the mechanical properties of granular packs by wavelength-scanning interferometry

2009 ◽  
Vol 466 (2115) ◽  
pp. 789-808 ◽  
Author(s):  
Yanzhou Zhou ◽  
Ricky D. Wildman ◽  
Jonathan M. Huntley
Keyword(s):  
Lateral Displacement ◽  
Probability Distributions ◽  
Accurate Determination ◽  
Contact Forces ◽  
Response Force ◽  
Wavelength Scanning ◽  
Scanning Interferometer ◽  
Lateral Displacements ◽  
Thick Glass

A wavelength-scanning interferometer has been constructed to observe both the normal and in-plane displacements particle by particle at the base of a model granular pack. The pack comprised 25 000 steel beads supported by a thick glass substrate and was subjected to local disturbing forces on its upper surface. The system allows measurement of normal displacements of the beads to a precision of ca 0.1 nm, thereby providing highly accurate determination of contact forces while minimizing artefacts due to substrate and grain compliance. The probability distribution of the normalized contact force was found to be approximately independent of the applied load on the upper surface of the granular pack and has an exponential tail. The probability distributions of the normalized response force and lateral displacement have similar power-law tails. The interactions between contact forces and lateral displacements suggest that significant internal rearrangement occurs in the granular pack as the load is increased, and particle displacement plays an important role in the mechanics of the granular material.

scholarly journals Application of Simulation Methods of Stochastic Processes to Vortex Excitation

2017 ◽  
Vol 63 (1) ◽  
pp. 77-98 ◽  
Author(s):  
T. Lipecki ◽  
A. Flaga
Keyword(s):  
Mathematical Model ◽  
Computer Program ◽  
Stochastic Processes ◽  
Numerical Simulations ◽  
Cross Sections ◽  
Simulation Methods ◽  
Direct Simulation ◽  
Time Step ◽  
Lateral Response ◽  
The Mathematical Model

AbstractA description of direct simulation of crosswind loads caused by critical vortex excitation and the response of the structure to these loads are presented in this paper. Tower-like structures of circular cross-sections are considered. A proposed mathematical model of vortex excitation has been numerically implemented and a selfserving computer program was created for the purpose. This software, cooperating with the FEM system, allows for a simulation of a crosswind load and lateral response in real time, meaning that at each time step of the calculations the load is generated using information regarding displacements seen beforehand. A detailed description of the mathematical model is neglected in this paper, which is focused on numerical simulations. WAWS and AR methods are used in simulations.

Analysis of STEM micrographs of thick objects

1978 ◽  
Vol 36 (2) ◽  
pp. 106-107
Author(s):  
S. Golladay
Keyword(s):  
Inelastic Scattering ◽  
Multiple Scattering ◽  
Mass Distribution ◽  
Cross Sections ◽  
Phase Contrast ◽  
Image Point ◽  
Contrast Effects ◽  
Total Cross Sections ◽  
Elastic And Inelastic Scattering

The theory of multiple scattering has been worked out by Groves and comparisons have been made between predicted and observed signals for thick specimens observed in a STEM under conditions where phase contrast effects are unimportant. Independent measurements of the collection efficiencies of the two STEM detectors, calculations of the ratio σe/σi = R, where σe, σi are the total cross sections for elastic and inelastic scattering respectively, and a model of the unknown mass distribution are needed for these comparisons. In this paper an extension of this work will be described which allows the determination of the required efficiencies, R, and the unknown mass distribution from the data without additional measurements or models. Essential to the analysis is the fact that in a STEM two or more signal measurements can be made simultaneously at each image point.

A quantitative approach to inner shell losses

1978 ◽  
Vol 36 (1) ◽  
pp. 526-527 ◽  
Author(s):  
R.D. Leapman ◽  
P. Rez ◽  
D.F. Mayers
Keyword(s):  
Energy Transfer ◽  
Cross Section ◽  
Cross Sections ◽  
Accurate Determination ◽  
Background Intensity ◽  
Core Excitation ◽  
Quantitative Basis ◽  
Cross Section Differential ◽  
Bound Electrons

Microanalysis by EELS has been developing rapidly and though the general form of the spectrum is now understood there is a need to put the technique on a more quantitative basis (1,2). Certain aspects important for microanalysis include: (i) accurate determination of the partial cross sections, σx(α,ΔE) for core excitation when scattering lies inside collection angle a and energy range ΔE above the edge, (ii) behavior of the background intensity due to excitation of less strongly bound electrons, necessary for extrapolation beneath the signal of interest, (iii) departures from the simple hydrogenic K-edge seen in L and M losses, effecting σx and complicating microanalysis. Such problems might be approached empirically but here we describe how computation can elucidate the spectrum shape.The inelastic cross section differential with respect to energy transfer E and momentum transfer q for electrons of energy E0 and velocity v can be written as

Preparation And elemental analysis of ancient fibers

1987 ◽  
Vol 45 ◽  
pp. 410-411
Author(s):  
Allen Angel ◽  
Kathryn A. Jakes
Keyword(s):  
Cross Sections ◽  
Physical Structure ◽  
Energy Dispersive ◽  
Archaeological Sites ◽  
X Ray ◽  
Long Term Storage ◽  
Backscattered Electron ◽  
Electron Imaging

Fabrics recovered from archaeological sites often are so badly degraded that fiber identification based on physical morphology is difficult. Although diagenetic changes may be viewed as destructive to factors necessary for the discernment of fiber information, changes occurring during any stage of a fiber's lifetime leave a record within the fiber's chemical and physical structure. These alterations may offer valuable clues to understanding the conditions of the fiber's growth, fiber preparation and fabric processing technology and conditions of burial or long term storage (1).Energy dispersive spectrometry has been reported to be suitable for determination of mordant treatment on historic fibers (2,3) and has been used to characterize metal wrapping of combination yarns (4,5). In this study, a technique is developed which provides fractured cross sections of fibers for x-ray analysis and elemental mapping. In addition, backscattered electron imaging (BSI) and energy dispersive x-ray microanalysis (EDS) are utilized to correlate elements to their distribution in fibers.

Gender determination of caucasoid hair using image analysis

1993 ◽  
Vol 51 ◽  
pp. 216-217
Author(s):  
T.B. Ball ◽  
W.M. Hess
Keyword(s):  
Image Analysis ◽  
Cross Sections ◽  
Scalp Hair ◽  
The Body ◽  
Equivalent Diameter ◽  
Cross Sectional ◽  
Hair Samples ◽  
Length Width ◽  
Morphological Differences

It has been demonstrated that cross sections of bundles of hair can be effectively studied using image analysis. These studies can help to elucidate morphological differences of hair from one region of the body to another. The purpose of the present investigation was to use image analysis to determine whether morphological differences could be demonstrated between male and female human Caucasian terminal scalp hair.Hair samples were taken from the back of the head from 18 caucasoid males and 13 caucasoid females (Figs. 1-2). Bundles of 50 hairs were processed for cross-sectional examination and then analyzed using Prism Image Analysis software on a Macintosh llci computer. Twenty morphological parameters of size and shape were evaluated for each hair cross-section. The size parameters evaluated were area, convex area, perimeter, convex perimeter, length, breadth, fiber length, width, equivalent diameter, and inscribed radius. The shape parameters considered were formfactor, roundness, convexity, solidity, compactness, aspect ratio, elongation, curl, and fractal dimension.

DETERMINATION OF PERFORMANCE INDICATORS OF THE TRUCK KrAZ-6510TE

2020 ◽  
pp. 19-26
Author(s):  
Olexandr Pavlenko ◽  
Serhii Dun ◽  
Maksym Skliar
Keyword(s):  
Mathematical Model ◽  
Surface Friction ◽  
Building Structures ◽  
Maximum Torque ◽  
Military Equipment ◽  
Military Vehicles ◽  
Force Magnitude ◽  
Vehicle Mobility ◽  
The Mathematical Model

In any economy there is a need for the bulky goods transportation which cannot be divided into smaller parts. Such cargoes include building structures, elements of industrial equipment, tracked or wheeled construction and agricultural machinery, heavy armored military vehicles. In any case, tractor-semitrailer should provide fast delivery of goods with minimal fuel consumption. In order to guarantee the goods delivery, tractor-semitrailers must be able to overcome the existing roads broken grade and be capable to tow a semi-trailer in off-road conditions. These properties are especially important for military equipment transportation. The important factor that determines a tractor-semitrailer mobility is its gradeability. The purpose of this work is to improve a tractor-semitrailer mobility with tractor units manufactured at PJSC “AutoKrAZ” by increasing the tractor-semitrailer gradeability. The customer requirements for a new tractor are determined by the maximizing the grade to 18°. The analysis of the characteristics of modern tractor-semitrailers for heavy haulage has shown that the highest rate of this grade is 16.7°. The factors determining the limiting gradeability value were analyzed, based on the tractor-semitrailer with a KrAZ-6510TE tractor and a semi-trailer with a full weight of 80 t. It has been developed a mathematical model to investigate the tractor and semi-trailer axles vertical reactions distribution on the tractor-semitrailer friction performances. The mathematical model has allowed to calculate the gradeability value that the tractor-semitrailer can overcome in case of wheels and road surface friction value and the tractive force magnitude from the engine. The mathematical model adequacy was confirmed by comparing the calculations results with the data of factory tests. The analysis showed that on a dry road the KrAZ-6510TE tractor with a 80 t gross weight semitrailer is capable to climb a gradient of 14,35 ° with its coupling mass full use condition. The engine's maximum torque allows the tractor-semitrailer to overcome a gradient of 10.45° It has been determined the ways to improve the design of the KrAZ-6510TE tractor to increase its gradeability. Keywords: tractor, tractor-semitrailer vehicle mobility, tractor-semitrailer vehicle gradeability.

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