scholarly journals Dynamic response of rail track in longitudinal direction

2018 ◽  
Vol 2018 (7) ◽  
pp. 1-9 ◽  
Author(s):  
Włodzimierz Czyczuła ◽  
Łukasz Chudyba
Keyword(s):  
Dynamic Response ◽  
Critical Speed ◽  
Linear Models ◽  
Longitudinal Direction ◽  
Damping Properties ◽  
Stationary Response ◽  
Rail Track ◽  
Train Speed ◽  
Short Time

The paper presents an analysis of linear models track response under longitudinal loads due to braking/accelerating of the train. Longitudinal forces are uniformly distributed on the whole length of the train. Analysis was carried out under assumption that – in the short time – train speed not changes significantly. Therefore stationary response of rail track is considered. The problem of critical speed has been analyzed. Effect of damping properties of track foundation on maximum longitudinal displacements were also considered. In summary certain practical conclusions were formulated as well as the further investigations were pointed out.

scholarly journals Effect of vertical imperfections on longitudinal railway track response

2019 ◽  
Vol 262 ◽  
pp. 11003
Author(s):  
Wlodzimierz Czyczula ◽  
Lukasz Chudyba
Keyword(s):  
Critical Speed ◽  
Linear Models ◽  
Railway Track ◽  
Traction Forces ◽  
Stationary Response ◽  
Rail Track ◽  
Train Speed ◽  
Short Time

The paper presents an analysis of linear models track response under longitudinal loads due to braking and accelerating of the train as well as constant traction forces. Longitudinal forces on the wheel-rail contacts are uniformly distributed on the whole length of train. Analysis is carried out under assumption that – in short time – train speed does not change significantly. Therefore stationary response of rail track is considered. The problem of critical speed is presented. Effect of vertical imperfections on the longitudinal rail displacement is considered under assumption that longitudinal forces varying in time are changed proportionally to the vertical forces. These forces are proportional to the amplitude of vertical imperfections. This analysis should be recognised as the main novelty of the paper. In the summary, certain practical conclusions are formulated as well as the further investigations are pointed out.

Optimum Design of Journal Bearings Dimensions for Rotating Machines

2020 ◽  
Vol 38 (10A) ◽  
pp. 1481-1488
Author(s):  
Tariq M. Hammza ◽  
Ehab N. Abas ◽  
Nassear R. Hmoad
Keyword(s):  
Aspect Ratio ◽  
Dynamic Response ◽  
Numerical Solution ◽  
Critical Speed ◽  
Design Method ◽  
Considerable Effect ◽  
Journal Bearings ◽  
Rotating Machines ◽  
Bearing Clearance ◽  
Study Results

The values of Many parameters which involve in the design of fluid film journal bearings mainly depend on the bearing applied load when using the conventional design method to design the journal bearings, in this study, as well as applied bearing load, the dynamic response and critical speed have been used to calculate the dimensions of journal bearings. In the field of rotating machine, especially a heavy-duty rotating machines, the critical speed and response are the main parameters that specify bearing dimensions. The bearing aspect ratio (bearing length to bore diameter) and bearing clearance have been determined based on rotor maximum critical speed and minimum response displacement. The analytical solution of rotor Eq. of motion was verified by numerical solution via using ANSYS Mechanical APDL 18.0 and by comparing the numerical solution with the preceding study. The final study results clearly showed that the bearing aspect ratio has little effect on the critical speed, but it has a high effect on the dynamic response also the bearing clearance has little effect on the critical speed and considerable effect on the dynamic response. The study showed that the more accurate values of bearing aspect ratio to make the response of rotor as low as possible are about 0.65 - 1 and bearing percent clearance is about 0.15 - 0.2 for different rotor dimensions.

Sternal Force-Displacement Relationship During Cardiopulmonary Resuscitation

1993 ◽  
Vol 115 (2) ◽  
pp. 195-201 ◽  
Author(s):  
K. G. Gruben ◽  
A. D. Guerci ◽  
H. R. Halperin ◽  
A. S. Popel ◽  
J. E. Tsitlik
Keyword(s):  
Cyclic Loading ◽  
Cardiopulmonary Resuscitation ◽  
Dynamic Response ◽  
Elastic Properties ◽  
Clinical Data ◽  
Viscoelastic Model ◽  
Damping Properties ◽  
Cpr Training ◽  
Force Displacement

A viscoelastic model is presented to describe the dynamic response of the human chest to cyclic loading during manual cardiopulmonary resuscitation (CPR). Sternal force and displacement were measured during 16 clinical resuscitation attempts and during compressions on five CPR training manikins. The model was developed to describe the clinical data and consists of the parallel combination of a spring and dashpot. The human chests’ elastic and damping properties were both augmented with increasing displacement. The manikins’ elastic properties were stiffer and both elastic and damping properties were less dependent on displacement than the humans’.

Rail Track Surface Image Acquisition and Positioning

2013 ◽  
Vol 278-280 ◽  
pp. 1143-1147
Author(s):  
Liang Sun ◽  
Jun Zhang ◽  
Zhe Chen ◽  
Long Guo ◽  
Jia Ge ◽  
...  
Keyword(s):  
High Speed ◽  
Detection System ◽  
Output Pulse ◽  
Location Information ◽  
Optical Encoder ◽  
Rail Track ◽  
Surface Image ◽  
Train Speed ◽  
Track Surface ◽  
Time Acquisition

Rail track surface detection system was constructed to detect the rail track surface. The mismatch between the train speed, rail track location and camera trigger speed was solved during the real-time acquisition process about the rail track using optical encoder and GPS module. In our system, optical encoder was used to reflect the train speed and output pulse to externally trigger the line scan high-speed camera exposure. At the same time, another pulse of optical encoder was transmitted to the computer to save the GPS location information. So the rail track images are saved with the track location information.

scholarly journals Improving Dynamic Response of a Single-Spool Gas Turbine Engine Using a Nonlinear Contoller

1992 ◽  
Author(s):  
O. F. Qi ◽  
N. R. L. Maccallum ◽  
P. J. Gawthrop
Keyword(s):  
Dynamic Response ◽  
Gas Turbine ◽  
Linear Models ◽  
Digital Simulation ◽  
Gas Turbine Engine ◽  
Open Loop ◽  
Nonlinear Controller ◽  
Nonlinear Simulation ◽  
Turbine Engine ◽  
Engine Simulation

This paper describes the design of a closed-loop nonlinear controller to improve the dynamic response of a single-spool gas turbine engine. The nonlinear controller is obtained by scheduling the gains of multivariable compensators as a function of engine non-dimensional shaft speed. The compensators, whose outputs are fuel flow and nozzle area, are designed using optimal control theory based on a set of linear models generated from a nonlinear engine simulation. Investigations are also made into developing simple algorithms to obtain an analytical expression for the compressor given its characteristic. The detailed process of developing a nonlinear simulation model for the engine is also described. The open-loop fuel controller is studied using the digital simulation.

Finite Mixture Dynamic Regression Modeling of Panel Data With Implications for Dynamic Response Analysis

2005 ◽  
Vol 30 (2) ◽  
pp. 169-187 ◽  
Author(s):  
David Kaplan
Keyword(s):  
Probability Density Function ◽  
Dynamic Response ◽  
Regression Model ◽  
Density Function ◽  
Regression Models ◽  
Linear Models ◽  
Finite Mixture ◽  
Response Analysis ◽  
Model Parameters ◽  
Mixture Density

This article considers the problem of estimating dynamic linear regression models when the data are generated from finite mixture probability density function where the mixture components are characterized by different dynamic regression model parameters. Specifically, conventional linear models assume that the data are generated by a single probability density function characterized by a single set of regression model parameters. However, when the true generating model is finite mixture density function, then estimation of conventional linear models under the assumption of a single density function may lead to erroneous conclusions. Instead, it may be desirable to estimate the regression model under the assumption that the data are derived from a finite mixture density function and to examine differences in the parameters of the model within each mixture component. Dynamic regression models and subsequent dynamic response analysis using dynamic multipliers are also likely to be affected by the existence of a finite mixture density because dynamic multipliers are functions of the regression model parameters. Utilizing finite mixture modeling applied to two real data examples, this article shows that dynamic responses to changes in exogenous variables can be quite different depending on the number and nature of underlying mixture components. Implications for substantive conclusions based on the use of dynamic multipliers is discussed.

scholarly journals Dynamic Response of Symmetric and Asymmetric Setback Buildings

2020 ◽  
Vol 9 (4) ◽  
pp. 3179-3183
Keyword(s):  
Dynamic Response ◽  
Transverse Direction ◽  
Dynamic Behaviour ◽  
Time History ◽  
Longitudinal Direction ◽  
Time History Analysis ◽  
Seismic Excitations ◽  
Numerical Studies ◽  
History Analysis ◽  
Codal Provisions

Numerical studies have been carried out to study the dynamic behaviour of a five-storey regular building, symmetric setback and asymmetric setback buildings having three bays along longitudinal direction and one bay along transverse direction. The objective of the study is to compare the irregularity indices with respect to different codal provisions such as IS:1893-2016, Euro Code 8-2004 and ASCE 7.05-2005 as well as with the expressions proposed by Karavasilis et al. (2008), and Pradip sarkar et al.(2010). These buildings are subjected to seismic excitations with time history analysis and the response parameters such as fundamental period of vibration of the structures, displacements and storey drifts were evaluated

scholarly journals Measuring change in biological communities: multivariate analysis approaches for temporal datasets with low sample size

PeerJ ◽  
2021 ◽  
Vol 9 ◽  
pp. e11096
Author(s):  
Hannah L. Buckley ◽  
Nicola J. Day ◽  
Bradley S. Case ◽  
Gavin Lear
Keyword(s):  
Time Series ◽  
Sample Size ◽  
Statistical Power ◽  
Structural Changes ◽  
Linear Models ◽  
Environmental Changes ◽  
Short Time Series ◽  
Biological Communities ◽  
Extinction Events ◽  
Short Time

Effective and robust ways to describe, quantify, analyse, and test for change in the structure of biological communities over time are essential if ecological research is to contribute substantively towards understanding and managing responses to ongoing environmental changes. Structural changes reflect population dynamics, changes in biomass and relative abundances of taxa, and colonisation and extinction events observed in samples collected through time. Most previous studies of temporal changes in the multivariate datasets that characterise biological communities are based on short time series that are not amenable to data-hungry methods such as multivariate generalised linear models. Here, we present a roadmap for the analysis of temporal change in short-time-series, multivariate, ecological datasets. We discuss appropriate methods and important considerations for using them such as sample size, assumptions, and statistical power. We illustrate these methods with four case-studies analysed using the R data analysis environment.

Effect of Negative Damping on Offshore Structures

2018 ◽  
Author(s):  
Gizat Derebe Amare ◽  
Yonas Zewdu Ayele
Keyword(s):  
Dynamic Response ◽  
Structural Design ◽  
Offshore Structures ◽  
Response Amplitude ◽  
Time Varying ◽  
Flow Induced Vibrations ◽  
Negative Damping ◽  
Wave Conditions ◽  
Short Time ◽  
Damping Model

Offshore structures are inevitably exposed to flow induced loads and flow-induced vibrations. The effect of these loads will affect the responses of structures, and the combined of two together on the response can lead the structures to induce different phenomena. The effect of damping is to counteract any dynamic response; however, “negative damping” increases the response amplitude. For example, the response amplitude may increase and can lead to structure instabilities, and it might cause damage in the short time. In order to achieve the best possible structural design, it is then relevant to study conditions under which structure instabilities occur. The purpose of this paper is to discuss the conditions under which offshore structures could induce “negative damping” and different structural phenomena that have been caused by “negative damping”. The discussion suggests a damping model with linear and time-varying terms, and shows theoretically that the model is negative under certain wave conditions.

scholarly journals The dynamic response of the bicycle rider’s body to vertical, fore-and-aft, and lateral perturbations

2019 ◽  
Vol 234 (7) ◽  
pp. 1944-1957
Author(s):  
Georgios Dialynas ◽  
Jelle W de Haan ◽  
Alfred C Schouten ◽  
Riender Happee ◽  
Arend L Schwab
Keyword(s):  
Dynamic Response ◽  
Random Noise ◽  
Three Dimensional ◽  
Vertical Direction ◽  
Longitudinal Direction ◽  
Apparent Mass ◽  
Motion Platform ◽  
Trunk Motion ◽  
Damped System ◽  
Two Wheeler

The objective of this study was to identify the dynamic response of the bicycle rider’s body during translational perturbations, in an effort to improve two-wheeler safety and comfort. A bicycle mock-up was equipped with sensors measuring three-dimensional seat and trunk accelerations and rider’s force responses at the seat, handlebars, and footpegs. The bicycle mock-up was driven by a hexapod motion platform that generated random noise perturbations in the range of 0–10 Hz. Twenty-four healthy male adults participated in this study. Responses are represented as frequency response functions capturing three-dimensional force interactions of the rider’s body at the seat, handlebars and footpegs in terms of apparent mass, and rider’s trunk motion (one-dimensional) as function of seat motion as seat-to-sternum transmissibility. Results showed that the vertical and longitudinal apparent mass for most of the bicycle interfaces followed the resonance of the seat-to-sternum transmissibility. A twice as high magnitude was observed at the resonance, although a more heavily damped system was apparent in the seat-to-sternum transmissibility. Resonant frequencies were considerably higher in the vertical direction compared to the longitudinal direction. Different dynamics were observed for the lateral measurements, where all magnitudes decreased after the base frequency, and no resonance was observed.

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