Responses of Continuous, Elastically Supported Beam Guideways to Transit Loads

1980 ◽  
Vol 102 (4) ◽  
pp. 247-254 ◽  
Author(s):  
J. F. Wilson ◽  
S. T. Barbas
Keyword(s):  
Dynamic Responses ◽  
Experimental Measurements ◽  
Constant Force ◽  
Euler Beam ◽  
Transit Systems ◽  
Elastic Supports ◽  
System Parameters ◽  
Wide Range ◽  
Speed Parameter ◽  
Elastically Supported

Solutions for nondimensional dynamic response histories are formulated for an undamped, continuous, Bernoulli-Euler beam resting on discrete, evenly-spaced, equal elastic supports. Responses depend on: The distribution of the constant force loads; a dimensionless load speed parameter; and the ratio of support stiffness to beam stiffness. Peak midspan moments and deflections are calculated over a wide range of system parameters for several beam configurations. Results are that the extreme end spans have the peak dynamic responses; that these responses increase as the relative support stiffness increases; and responses may become unbounded. Experimental measurements complement the calculations. Results are applicable to the design of cable-stayed guideways for advanced transit systems.

scholarly journals Soft-drop grooming for hadronic event shapes

2021 ◽  
Vol 2021 (7) ◽  
Author(s):  
Jeremy Baron ◽  
Daniel Reichelt ◽  
Steffen Schumann ◽  
Niklas Schwanemann ◽  
Vincent Theeuwes
Keyword(s):  
Event Generator ◽  
Experimental Measurements ◽  
Event Shape ◽  
Matrix Elements ◽  
Underlying Event ◽  
Hadronic Event ◽  
Wide Range ◽  
Event Shapes ◽  
The Impact ◽  
Perturbative Corrections

Abstract Soft-drop grooming of hadron-collision final states has the potential to significantly reduce the impact of non-perturbative corrections, and in particular the underlying-event contribution. This eventually will enable a more direct comparison of accurate perturbative predictions with experimental measurements. In this study we consider soft-drop groomed dijet event shapes. We derive general results needed to perform the resummation of suitable event-shape variables to next-to-leading logarithmic (NLL) accuracy matched to exact next-to-leading order (NLO) QCD matrix elements. We compile predictions for the transverse-thrust shape accurate to NLO + NLL′ using the implementation of the Caesar formalism in the Sherpa event generator framework. We complement this by state-of-the-art parton- and hadron-level predictions based on NLO QCD matrix elements matched with parton showers. We explore the potential to mitigate non-perturbative corrections for particle-level and track-based measurements of transverse thrust by considering a wide range of soft-drop parameters. We find that soft-drop grooming indeed is very efficient in removing the underlying event. This motivates future experimental measurements to be compared to precise QCD predictions and employed to constrain non-perturbative models in Monte-Carlo simulations.

Dynamic Response of the Spectral Element Model by Using the FFT

2007 ◽  
Vol 345-346 ◽  
pp. 845-848
Author(s):  
Joo Yong Cho ◽  
Han Suk Go ◽  
Usik Lee
Keyword(s):  
Fourier Transforms ◽  
Initial Conditions ◽  
Element Model ◽  
Spectral Element ◽  
Dynamic Responses ◽  
Analysis Method ◽  
Euler Beam ◽  
Exact Analytical Solutions ◽  
Simply Supported ◽  
Spectral Analysis Method

In this paper, a fast Fourier transforms (FFT)-based spectral analysis method (SAM) is proposed for the dynamic analysis of spectral element models subjected to the non-zero initial conditions. To evaluate the proposed SAM, the spectral element model for the simply supported Bernoulli-Euler beam is considered as an example problem. The accuracy of the proposed SAM is evaluated by comparing the dynamic responses obtained by SAM with the exact analytical solutions.

Vibration Suppression of an Elastically Supported Beam With Closely Spaced Natural Frequencies

2020 ◽  
Author(s):  
Haizhou Liu ◽  
Hao Gao
Keyword(s):  
Natural Frequencies ◽  
Vibration Suppression ◽  
Fixed Point Theory ◽  
Dynamic Performance ◽  
Point Theory ◽  
Primary System ◽  
Computationally Efficient ◽  
Wide Range ◽  
Univariate Optimization ◽  
Elastically Supported

Abstract Vibration suppression of distributed parameter systems is of great interest and has a wide range of applications. The dynamic performance of a primary system can be improved by adding dynamic vibration absorbers (DVA). Although the relevant topics have been studied for decades, the trade-off between capability of suppressing multiple resonant peaks and complexity of absorbers has not been well addressed. In this paper, the vibration suppression problem of a uniform Euler-Bernoulli beam with closely spaced natural frequencies is investigated. To achieve desired vibration reduction, a two-DOF DVA is connected to the beam through a pair of a spring and a dashpot. By introducing a virtual ground spring, the parameters of the absorber are determined via extended fixed point theory. The proposed method only requires univariate optimization and is computationally efficient. Numerical examples conducted verify the viability of the proposed method and the effectiveness of a two-DOF DVA in suppressing double resonances.

scholarly journals Modeling a Helical Fluid Inerter System with Time-Invariant Mem-Models

2020 ◽  
Author(s):  
David Wagg ◽  
Jin-Song Pei
Keyword(s):  
Element Model ◽  
Feedforward Neural Network ◽  
Dynamic Responses ◽  
Experimental Measurements ◽  
The Novel ◽  
State Variables ◽  
Model Concept ◽  
Multilayer Feedforward Neural Network ◽  
Time Invariant ◽  
Model Family

In this paper, experimental data from tests of a helical fluid inerter are used to model the observed hysteretic behaviour. The novel idea is to test the feasibility of employing mem-models, which are time-invariant herein, to capture the observed phenomena by using physically meaningful state variables. Firstly we use a Masing model concept, identified with a multilayer feedforward neural network to capture the physical characteristics of the hysteresis functions. Following this, a more refined approach based on the concept of a multi-element model including a mem-inerter is developed. This is compared with previous definitions in the literature and shown to be a more general model. Through-out this paper, numerical simulations are used to demonstrate the type of dynamic responses anticipated using the proposed time- invariant mem-models. Corresponding experimental measurements are processed to demonstrate and validate the new mem-modeling concepts. The results show that it is possible to have a unified model constructed using both the damper and inerter from the mem-model family. This model captures many of the more subtle features of the underlying physics, not captured by other forms of existing model.

scholarly journals The structure of the co-orbital stable regions as a function of the mass ratio

2020 ◽  
Vol 496 (3) ◽  
pp. 3700-3707
Author(s):  
L Liberato ◽  
O C Winter
Keyword(s):  
Angular Distance ◽  
Stable Region ◽  
Polynomial Functions ◽  
Mass Ratio ◽  
Three Body Problem ◽  
System Parameters ◽  
Wide Range ◽  
Value Range ◽  
Three Body ◽  
Orbital Region

ABSTRACT Although the search for extrasolar co-orbital bodies has not had success so far, it is believed that they must be as common as they are in the Solar system. Co-orbital systems have been widely studied, and there are several works on stability and even on formation. However, for the size and location of the stable regions, authors usually describe their results but do not provide a way to find them without numerical simulations, and, in most cases, the mass ratio value range is small. In this work, we study the structure of co-orbital stable regions for a wide range of mass ratio systems and build empirical equations to describe them. It allows estimating the size and location of co-orbital stable regions from a few system parameters. Thousands of massless particles were distributed in the co-orbital region of a massive secondary body and numerically simulated for a wide range of mass ratios (μ) adopting the planar circular restricted three-body problem. The results show that the upper limit of horseshoe regions is between 9.539 × 10−4 < μ < 1.192 × 10−3, which corresponds to a minimum angular distance from the secondary body to the separatrix of between 27.239º and 27.802º. We also found that the limit to existence of stability in the co-orbital region is about μ = 2.3313 × 10−2, much smaller than the value predicted by the linear theory. Polynomial functions to describe the stable region parameters were found, and they represent estimates of the angular and radial widths of the co-orbital stable regions for any system with 9.547 × 10−5 ≤ μ ≤ 2.331 × 10−2.

Optimum Design of Elastically Supported Gyroscopes for Ship Stabilization

1984 ◽  
Vol 106 (4) ◽  
pp. 387-392
Author(s):  
K.-N. Lee ◽  
A. Seireg
Keyword(s):  
Optimal Design ◽  
Dynamic Model ◽  
Optimum Design ◽  
Design Procedures ◽  
System Parameters ◽  
Ship Roll ◽  
Elastically Supported ◽  
Elastic Spring

The study reported in this paper deals with the development of a dynamic model for the analysis of elastically supported gyroscopic absorber systems for ship stabilization. The gryoscopes are mounted on elastically supported platforms at the fore and aft ends of the ship to minimize both the roll and pitch movements. Springs and dampers are also utilized between the gyroscope gimbal and the platform. Several design configurations of the absorber are considered. Optimal design procedures are utilized to find the system parameters for best performance in each case. The performance of the resulting optimum absorber shows that introducing the elastic spring and damper between the gimbal and platform has a significant effect on reducing the ship-roll action.

scholarly journals Kinetic stability properties of relativistic nonneutral electron flow for low-frequency extraordinary-mode perturbations

1989 ◽  
Vol 7 (1) ◽  
pp. 85-109 ◽  
Author(s):  
Ronald C. Davidson ◽  
Han S. Uhm
Keyword(s):  
Dispersion Relation ◽  
Layer Thickness ◽  
Electron Energy ◽  
Electron Flow ◽  
Low Frequency ◽  
Outer Edge ◽  
Stability Properties ◽  
System Parameters ◽  
Wide Range ◽  
Electron Layer

The kinetic stability properties of relativistic nonneutral electron flow in planar diode geometry are examined for extraordinary-mode perturbations about the self-consistent Vlasov equilibrium . Here, the cathode is located at x = 0; the anode is located at x = d the outer edge of the electron layer is located at is the equilibrium flow velocity in the x-direction; n^b is the electron density at the cathode (x = 0); and is the axial magnetic field, with const. in the vacuum region (xb < x ≤ d). The extraordinary-mode eigenvalue equation, derived in a companion paper for low-frequency, long-wavelength perturbations, is solved exactly. This leads to a formal dispersion relation, which can be used to determine the complex eigenfrequency ω over a wide range of system parameters and wavenumber k in the y-direction. The formal dispersion relation is further simplified for and , assuming low-frequency perturbations about a tenuous electron layer with and . Here, , and , where denotes the average equilibrium orbit, and [γ(x) − 1]mc2 is the average kinematic energy of an electron fluid element. The resulting approximate dispersion relation is solved numerically over a wide range of system parameters to determine the detailed dependence of stability properties on electromagnetic effects, layer thickness, and electron energy, as measured by , and γb − 1, respectively. Here, γb = γ(xb) denotes the electron energy at the outer edge of the electron layer. As a general remark, it is found that increasing the electron energy (γb − 1), increasing the strength of electromagnetic effects , and/or decreasing the layer thickness (xb/d) all have a stabilizing influence.

Constrained-Equilibrium Modeling of Methane Oxidation in Air

2013 ◽  
Author(s):  
Ghassan Nicolas ◽  
Mohammad Janbozorgi ◽  
Hameed Metghalchi
Keyword(s):  
Combustion Process ◽  
Rate Equations ◽  
Experimental Measurements ◽  
Combustion Modeling ◽  
Ignition Delay Times ◽  
Wide Range ◽  
Constrained Equilibrium ◽  
Detailed Kinetic Model ◽  
Rate Controlled ◽  
Oxidation In Air

The Rate-Controlled Constrained-Equilibrium (RCCE) has been further developed and applied to model methane/air combustion process. The RCCE method is based on local maximization of entropy or minimization of a relevant free energy at any time during the non-equilibrium evolution of the system subject to a set of constraints. The constraints are imposed by slow rate-limiting reactions. Direct integration of the rate equations for the constraint potentials has been employed. Once the values of the potentials are obtained, the concentration of all species can be calculated. A set of constraints has been developed for methane/air mixtures in the method of Rate-Controlled Constrained-Equilibrium (RCCE). The model predicts the ignition delay times, which have been compared to those predicted by detailed kinetic model (DKM) and with shock tube experimental measurements. The DKM includes 60 H/O/C1–2/N species and 352 reactions. The RCCE model using 16 constraints has been applied for combustion modeling in a wide range of initial temperatures (900–1200 K), pressures (1–50 atmospheres) and fuel-air equivalence ratio (0.6–1.2). The predicted results of using RCCE are within 5% of those of DKM model and are in excellent agreement with experimental measurements in shock tubes.

Determination of Gyroscopic Drifts Associated With Angular Support Motions

1970 ◽  
Vol 37 (2) ◽  
pp. 279-286
Author(s):  
R. A. Wenglarz
Keyword(s):  
Differential Equations ◽  
Digital Computer ◽  
Systematic Approach ◽  
Equations Of Motion ◽  
System Parameters ◽  
Constant Rate ◽  
Wide Range ◽  
Fixed Line

A previously proposed systematic approach for the analysis of gyroscopic drifts associated with angular support motions is further developed. For a wide range of support motions, the problem of determination of drifts is reduced to the evaluation of four integrals. The validity of the theory is tested by applying it to a gyroscope experiencing a constant rate about a fixed line and comparing the resulting predictions with those of digital computer solutions of the exact differential equations of motion, and formulas relating steady drifts to system parameters are presented.

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