Flow Analysis and Modeling of Field-Controllable, Electro- and Magneto-Rheological Fluid Dampers

2005 ◽  
Vol 74 (1) ◽  
pp. 13-22 ◽  
Author(s):  
Xiaojie Wang ◽  
Faramarz Gordaninejad
Keyword(s):  
Theoretical Model ◽  
Flow Analysis ◽  
Closed Form Solution ◽  
Nonlinear Behavior ◽  
Form Solution ◽  
Proposed Model ◽  
Fluid Dampers ◽  
Magneto Rheological ◽  
Er Fluid ◽  
Theoretical Results

This study combines a fluid mechanics-based approach and the Herschel-Bulkley constitutive equation to develop a theoretical model for predicting the behavior of field-controllable, magneto-rheological (MR), and electro-rheological (ER) fluid dampers. The goal is to provide an accurate theoretical model for analysis, design, and development of control algorithms of MR/ER dampers. Simplified explicit expressions for closed-form solution of the pressure drop across a MR fluid valve are developed. The Herschel-Bulkley quasi-steady flow analysis is extended to include the effect of fluid compressibility to account for the nonlinear dynamic behavior of MR/ER fluid dampers. The advantage of this model is that it only depends on geometric and material properties of the MR/ER material and the device. The theoretical results are validated by an experimental study. It is demonstrated that the proposed model can effectively predict the nonlinear behavior of field-controllable fluid dampers.

A Proposed Model for Predicting Clamp Load Loss Due to Gasket Creep Relaxation in Bolted Joints

2012 ◽  
Vol 134 (2) ◽  
Author(s):  
Basil A. Housari ◽  
Ali A. Alkelani ◽  
Sayed A. Nassar
Keyword(s):  
Joint Stiffness ◽  
Closed Form Solution ◽  
Load Level ◽  
Form Solution ◽  
Bolted Joints ◽  
Experimental Procedure ◽  
Proposed Model ◽  
Gasket Material ◽  
Improved Model ◽  
Over Time

An improved mathematical model is proposed for predicting clamp load loss due gasket creep relaxation in bolted joints, taking into consideration gasket behavior, bolt stiffness, and joint stiffness. The gasket creep relaxation behavior is represented by a number of parameters which has been obtained experimentally in a previous work. An experimental procedure is developed to verify the proposed model using a single-bolt joint. The bolt is tightened to a target preload and the clamp load loss due to gasket creep relaxation is observed over time under various preload levels. The experimental and analytical results are presented and discussed. The proposed model provides a prediction of the residual clamp load as a function of time, gasket material and thickness, bolt stiffness, and joint stiffness. The improved model can be used to simulate the behavior of creep relaxation in soft joints as the joint stiffness effect is considered. Additionally, a closed form solution is formulated to determine the initial clamp load level necessary to provide the desired level of a steady state residual clamp load in the joint, by taking the gasket creep relaxation into account.

scholarly journals Added Mass and Damping of a Vibrating Rod in Confined Viscous Fluids

1976 ◽  
Vol 43 (2) ◽  
pp. 325-329 ◽  
Author(s):  
S. S. Chen ◽  
M. W. Wambsganss ◽  
J. A. Jendrzejczyk
Keyword(s):  
Experimental Data ◽  
Experimental Study ◽  
Cylindrical Shell ◽  
Closed Form Solution ◽  
Added Mass ◽  
Form Solution ◽  
Viscous Fluids ◽  
Series Of Experiments ◽  
Theoretical Results ◽  
Good Agreement

This paper presents an analytical and experimental study of a cylindrical rod vibrating in a viscous fluid enclosed by a rigid, concentric cylindrical shell. A closed-form solution for the added mass and damping coefficient is obtained and a series of experiments with cantilevered rods vibrating in various viscous fluids is performed. Experimental data and theoretical results are in good agreement.

A Proposed Model for Predicting Residual Clamp Load in Gasketed Bolted Joints

2010 ◽  
Author(s):  
Basil A. Housari ◽  
Ali A. Alkelani ◽  
Sayed A. Nassar
Keyword(s):  
Joint Stiffness ◽  
Closed Form Solution ◽  
Load Level ◽  
Form Solution ◽  
Relaxation Behavior ◽  
Bolted Joints ◽  
Experimental Procedure ◽  
Proposed Model ◽  
Gasket Material ◽  
Improved Model

An improved mathematical model is proposed for predicting the residual clamp load in gasketed bolted joints, taking into consideration gasket creep relaxation behavior, bolt stiffness, and joint stiffness. The gasket creep relaxation behavior is represented by a number of parameters which has been obtained experimentally in a previous work. An experimental procedure is developed to verify the proposed model using a single-bolt joint. The bolt is tightened to a target preload and the clamp load loss due to gasket creep relaxation is observed over time under various preload levels. The experimental and analytical results are presented and discussed. The proposed model provides a prediction of the residual clamp load as a function of time, gasket material and thickness, bolt stiffness, and joint stiffness. The improved model can be used to simulate the behavior of creep relaxation in soft joints as the joint stiffness effect is considered. Additionally, a closed form solution is formulated to determine the initial clamp load level necessary to provide the desired level of a steady state residual clamp load in the joint, by taking the gasket creep relaxation into account.

scholarly journals An Efficient Algorithm for Learning Dictionary under Coherence Constraint

2016 ◽  
Vol 2016 ◽  
pp. 1-11 ◽  
Author(s):  
Huang Bai ◽  
Sheng Li ◽  
Qianru Jiang
Keyword(s):  
Synthetic Data ◽  
Closed Form Solution ◽  
Form Solution ◽  
Gram Matrix ◽  
Audio Signals ◽  
Novel Approach ◽  
Representation Error ◽  
Proposed Model ◽  
Minimization Procedure ◽  
Series Of Experiments

Dictionary learning problem has become an active topic for decades. Most existing learning methods train the dictionary to adapt to a particular class of signals. But as the number of the dictionary atoms is increased to represent the signals much more sparsely, the coherence between the atoms becomes higher. According to the greedy and compressed sensing theories, this goes against the implementation of sparse coding. In this paper, a novel approach is proposed to learn the dictionary that minimizes the sparse representation error according to the training signals with the coherence taken into consideration. The coherence is constrained by making the Gram matrix of the desired dictionary approximate to an identity matrix of proper dimension. The method for handling the proposed model is mainly based on the alternating minimization procedure and, in each step, the closed-form solution is derived. A series of experiments on synthetic data and audio signals is executed to demonstrate the promising performance of the learnt incoherent dictionary and the superiority of the learning method to the existing ones.

Slope Discontinuities in Pressure Vessels

1970 ◽  
Vol 37 (3) ◽  
pp. 587-595 ◽  
Author(s):  
C. R. Steele ◽  
J. Skogh
Keyword(s):  
Significant Variation ◽  
Weld Seam ◽  
Closed Form Solution ◽  
Pressure Vessels ◽  
Form Solution ◽  
Edge Zone ◽  
Slope Discontinuity ◽  
Theoretical Results ◽  
Maximum Stresses ◽  
Slope Discontinuities

A closed-form solution is obtained for the problem of a shell of revolution with a meridional slope discontinuity, which might occur at a weld seam in a pressure vessel. The effect of significant variation in the slope occurring within the usual “edge zone” and the nonlinear pressurization effect are taken into consideration. Graphs are presented from which maximum stresses can be easily computed for a wide variation of the parameters. The theoretical results agree with numerical values obtained from a computer program, even for shells that are relatively thick, for slope discontinuities that are relatively severe, and for high pressurization.

A Proposed Model for Creep Relaxation of Soft Gaskets in Bolted Joints at Room Temperature

2008 ◽  
Vol 130 (1) ◽  
Author(s):  
Ali A. Alkelani ◽  
Basil A. Housari ◽  
Sayed A. Nassar
Keyword(s):  
Mathematical Model ◽  
Room Temperature ◽  
Closed Form Solution ◽  
Load Level ◽  
Form Solution ◽  
Bolted Joints ◽  
Experimental Procedure ◽  
Proposed Model ◽  
Gasket Material ◽  
Over Time

A mathematical model is proposed for predicting the residual clamp load during creep and∕or relaxation in gasketed joints. An experimental procedure is developed to verify the proposed model for predicting the gasket relaxation under a constant compression, gasket creep under a constant stress, and gasket creep relaxation. To study gasket creep relaxation, a single-bolt joint is used. The bolt is tightened to a target preload and the clamp load decay due to gasket creep relaxation is observed over time under various preload levels. Experimental and analytical results are presented and discussed. The proposed model provides an accurate prediction of the residual clamp load as a function of time, gasket material, and geometric properties of the gasket. A closed form solution is formulated to determine the initial clamp load level necessary to provide the desired level of a steady state residual clamp load in the joint, by taking the gasket creep relaxation into account.

PRICING VULNERABLE EUROPEAN OPTIONS WITH STOCHASTIC CORRELATION

2017 ◽  
Vol 32 (1) ◽  
pp. 67-95 ◽  
Author(s):  
Xingchun Wang
Keyword(s):  
Default Risk ◽  
Closed Form Solution ◽  
Form Solution ◽  
Underlying Asset ◽  
Asset Return ◽  
Stochastic Correlation ◽  
Market Index ◽  
Proposed Model ◽  
Vulnerable Options ◽  
The Impact

In this paper, we present a new pricing model for vulnerable options, with time-varying variances for each asset described by Generalized Autoregressive Conditional Heteroscedasticity processes and correlated with the return of the asset. By connecting the underlying asset and the counterparty's assets through the market factor channel, the proposed model also captures stochastic correlation between the underlying asset return and the return of the counterparty's assets. The correlation depends on the levels of the variances of both assets and the market index as well. In the proposed framework, the closed-form solution for vulnerable options is derived and numerical results are presented to investigate the impact of counterparty default risk.

Mathematical Modeling of Drug Release from Spherical Drug Particles: Analysis of the Effect of Absorption Rate on Drug Release Rate

2009 ◽  
Vol 4 (5) ◽  
Author(s):  
Norman W Loney ◽  
Ramana Susarla
Keyword(s):  
Drug Release ◽  
Absorption Rate ◽  
Release Kinetics ◽  
Closed Form Solution ◽  
Form Solution ◽  
Proposed Model ◽  
Significant Difference ◽  
Rate Of Absorption ◽  
Kinetics Of ◽  
And Diffusion

A closed form solution has been obtained for the release kinetics of a solute from a spherical drug matrix into a finite volume of liquid, taking into account the effect of rate of absorption. The proposed model results clearly show the effect of the absorption rate constant on the rate of drug release. The obtained results are compared with the experimental data and diffusion-only model results. There is a significant difference in the release profile when the rate of absorption of drug is slow. The most important feature of the mathematical relationship between the liquid concentration verses time is its ability to predict change in the performance of the drug by manipulating the parameters of the equation. These parameters include the initial concentration of the drug, the radius of the drug and diffusivity of the drug in the solid to name a few. Therefore, a substantial number of experiments can be eliminated when the optimal performance of a drug is sought after.

Analysis on a Counter-Current Flow Hemodialyzer

2009 ◽  
Vol 4 (5) ◽  
Author(s):  
Norman W Loney
Keyword(s):  
Experimental Data ◽  
Mass Transfer ◽  
Closed Form Solution ◽  
Maximum Error ◽  
Form Solution ◽  
Transfer Coefficients ◽  
Confluent Hypergeometric Functions ◽  
Proposed Model ◽  
Counter Current ◽  
Good Agreement

The closed form solution to the conjugated boundary value problem posed by a counter current hemodialyzer facilitates the estimation of the overall mass transfer coefficient. Comparison of the proposed model results with published experimental data shows good agreement for Urea and Creatinine clearances over a published range of blood and dialyzate flow rates. This model predicts clearances with a maximum error of less than 4% for both Urea and Creatinine when blood flow is 75% of the dialyzate flow. However, when both blood and dialyzate flows are identical the model over predicts the experimental data by 1.47% in the case of Urea and 4.75 for Creatinine flows of 300 ml/min. Although the concentration profile is an infinite series involving confluent hypergeometric functions, 2 terms of the series were sufficient (Mathematica notebook program) to produce these results. Overall mass transfer coefficients can now be deduced from the Sherwood numbers and provide possible improvement over currently used area coefficients.

ANALYTICAL VALUATION OF VULNERABLE OPTIONS IN A DISCRETE-TIME FRAMEWORK

2016 ◽  
Vol 31 (1) ◽  
pp. 100-120 ◽  
Author(s):  
Xingchun Wang
Keyword(s):  
Discrete Time ◽  
Default Risk ◽  
Closed Form Solution ◽  
Form Solution ◽  
Reduced Form ◽  
Option Prices ◽  
Underlying Asset ◽  
Proposed Model ◽  
Form Model ◽  
Vulnerable Options

In this paper, we present a pricing model for vulnerable options in discrete time. A Generalized Autoregressive Conditional Heteroscedasticity process is used to describe the variance of the underlying asset, which is correlated with the returns of the asset. As for counterparty default risk, we study it in a reduced form model and the proposed model allows for the correlation between the intensity of default and the variance of the underlying asset. In this framework, we derive a closed-form solution for vulnerable options and investigate quantitative impacts of counterparty default risk on option prices.

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