Virus Transmission Through Compromised Synthetic Barriers: Part I—Effect of Unsteady Driving Pressures

2001 ◽  
Vol 123 (5) ◽  
pp. 506-512 ◽  
Author(s):  
Matthew R. Myers ◽  
Bigyani Das
Keyword(s):  
Steady State ◽  
Virus Transmission ◽  
Time Varying ◽  
Virus Suspension ◽  
Synthetic Membranes ◽  
Virus Adsorption ◽  
Barrier Surface ◽  
Number Of Cycles ◽  
Static Conditions ◽  
Steady State Predictions

Although synthetic membranes such as gloves, condoms, and instrument sheaths are used in environments with highly time-varying stresses, their effectiveness as barriers to virus transmission is almost always tested under static conditions. In this paper it is shown how a previously developed mathematical model can be used to transform information from static barrier tests into predictions for more realistic use conditions. Using a rate constant measured for herpes adsorption to latex in saline, and an oscillatory trans-membrane pressure representative of coitus, the amount of virus transmitted through a hole (2 μm diameter) in a condom is computed. Just beyond the exit orifice of the pore, transport is dominated by the rapidly dissipating viscous jet of virus suspension, which results in an accumulation of viruses roughly 20 pore radii from the barrier surface during each cycle. Due to virus adsorption to the barrier surfaces, the simulations reveal a gradual decrease in virus flow with increasing number of cycles, and thus a slow divergence from predictions based upon steady-state conditions. Still, over the 500 cycles simulated, steady-state predictions approximate the net number of viruses transmitted to within 25 percent error.

Dynamic Stability of an Impact System Connected With Rock Drilling

1969 ◽  
Vol 36 (4) ◽  
pp. 743-749 ◽  
Author(s):  
C. C. Fu
Keyword(s):  
Computer Simulation ◽  
Exact Solution ◽  
Steady State ◽  
Asymptotic Stability ◽  
Piecewise Linear ◽  
Steady State Solution ◽  
External Excitation ◽  
Rock Drilling ◽  
Impact System ◽  
Number Of Cycles

This paper deals with asymptotic stability of an analytically derived, synchronous as well as nonsynchronous, steady-state solution of an impact system which exhibits piecewise linear characteristics connected with rock drilling. The exact solution, which assumes one impact for a given number of cycles of the external excitation, is derived, its asymptotic stability is examined, and ranges of parameters are determined for which asymptotic stability is assured. The theoretically predicted stability or instability is verified by a digital computer simulation.

The Elastic-Plastic Analysis of Tubes—IV: Thermal Ratchetting

1992 ◽  
Vol 114 (2) ◽  
pp. 236-245 ◽  
Author(s):  
W. Jiang
Keyword(s):  
Steady State ◽  
Plastic Strain ◽  
Centrifugal Force ◽  
Kinematic Hardening ◽  
Elastic Plastic ◽  
External Pressures ◽  
Plastic Analysis ◽  
Steady Solutions ◽  
Number Of Cycles

This paper continues the investigation of the shakedown behavior of tubes subjected to cyclic centrifugal force and temperature, and sustained internal and external pressures. It is found that when ratchetting occurs, the plastic strain builds up with each cycle, but finally reaches a steady state after a large number of cycles for kinematic hardening materials. The steady solutions for three kinds of ratchetting behavior are found and given in this paper.

On Stability of a Nonlinear, Periodically Time Varying, Rotating Blade

2011 ◽  
Author(s):  
Fengxia Wang
Keyword(s):  
Steady State ◽  
Differential Equations ◽  
Nonlinear Partial Differential Equations ◽  
Multiple Time ◽  
Time Varying ◽  
Rotating Blade ◽  
Stability And Bifurcation ◽  
Geometric Stiffening ◽  
Rotational Motions ◽  
The Stability

This paper discusses the stability of a periodically time-varying, spinning blade with cubic geometric nonlinearity. The modal reduction method is adopted to simplify the nonlinear partial differential equations to the ordinary differential equations, and the geometric stiffening is approximated by the axial inertia membrane force. The method of multiple time scale is employed to study the steady state motions, the corresponding stability and bifurcation for such a periodically time-varying rotating blade. The backbone curves for steady-state motions are achieved, and the parameter map for stability and bifurcation is developed. Illustration of the steady-state motions is presented for an understanding of rotational motions of the rotating blade.

Analysis of an Accelerating Rotor-Bearing System With Flexible Damped Supports

1998 ◽  
Author(s):  
Euro L. Casanova ◽  
Luis U. Medina
Keyword(s):  
Steady State ◽  
Numerical Integration ◽  
Equations Of Motion ◽  
Peak Amplitude ◽  
Graphical Form ◽  
Jeffcott Rotor ◽  
Rotor Bearing ◽  
Flexible Supports ◽  
Steady State Predictions ◽  
Bearing System

This paper deals with the dynamics of an accelerating unbalanced Jeffcott rotor-bearing system mounted on damped, flexible supports. The general equations of motion for such a system are presented and discussed. The rotor response was predicted, via numerical integration, for various cases in runup and rundown conditions and presented in graphical form. The effects of acceleration on the rotor peak amplitude and the speed at which the peak occurs is discussed and compared to steady state predictions.

A Study of Formation of Circulation Patterns in Laminar Unsteady Lid-Driven Cavity Flows Using PIV Measurement Techniques

2012 ◽  
Author(s):  
K. M. Akyuzlu ◽  
J. Farkas
Keyword(s):  
Steady State ◽  
Measurement Techniques ◽  
Reynolds Numbers ◽  
Working Fluid ◽  
Computational Fluid Mechanics ◽  
Square Cavity ◽  
Driven Cavity ◽  
Circulation Patterns ◽  
Piv Measurement ◽  
Steady State Predictions

An experimental study was conducted to observe/visualize, the formation of circulation patterns inside a square cavity due to the movement of a lid at constant velocity. Lid driven cavity flow is one of the benchmark studies used in the verification/improvement of CFD codes for internal flow applications/predictions. Previous work on this topic is primarily focused on improving the steady state predictions of the CFD codes using different numerical schemes and algorithms. Furthermore, almost all of the studies reported in computational fluid mechanics literature relates to steady state predictions of lid or shear driven flows. Experimental work that is reported in these studies is limited in scope and number. This paper reports on the measurements we made using Particle Image Velocimeter (PIV) technique to determine the flow field as it develops from stagnation to steady state inside a square cavity driven by a lid. For this purpose, we employed a 2-D PIV system, which uses a double-cavity, Nd:Yag laser to illuminate the test cavity. Experiments were conducted using water as the working fluid inside a square cavity that is one inch (25.4 mm) high and one inch wide. The depth of the cavity is five inches (127 mm) to ensure two-dimensional circulations patterns. Hollow glass sphere particles with 10 microns in diameter were used as seeding of the working fluid, water. Experiments were repeated for different lid velocities corresponding to lid Reynolds numbers (laminar to beginning of transition of turbulence.) Velocity fields were captured during the development of the circulations patters each being unique for the time of the measurement and value of the lid velocity. The center of the circulation pattern and its path inside the cavity is constructed from the captured images as steady state is attained. Also, the strength of the circulation (as manifested by the increase in the diameter of the circulation) is determined at different times for different Reynolds numbers.

scholarly journals Attenuation and amplification of the transient current in nanojunctions with time-varying gate potentials

2017 ◽  
Vol 31 (14) ◽  
pp. 1750105 ◽  
Author(s):  
Eduardo C. Cuansing
Keyword(s):  
Steady State ◽  
Green's Functions ◽  
Green’S Functions ◽  
Step Function ◽  
Time Varying ◽  
Nonequilibrium Green’S Functions ◽  
Bias Potential ◽  
Gate Potential ◽  
Drain Bias ◽  
Nonequilibrium Green's Functions

We study charge transport in a source-channel-drain system with a time-varying applied gate potential acting on the channel. We calculate both the current flowing from the source into channel and out of the channel into the drain. The current is expressed in terms of nonequilibrium Green’s functions. These nonequilibrium Green’s functions can be determined from the steady-state Green’s functions and the equilibrium Green’s functions of the free leads. We find that the application of the gate potential can induce current to flow even when there is no source-drain bias potential. However, the direction of the current from the source and the current to the drain are opposite, thereby resulting in no net current flowing within the channel. When a source-drain bias potential is present, the net current flowing to the source and drain can either be attenuated or amplified depending on the sign of the applied gate potential. We also find that the response of the system to a dynamically changing gate potential is not instantaneous, i.e., a relaxation time has to pass before the current settles into a steady value. In particular, when the gate potential is in the form of a step function, the current first overshoots to a maximum value, oscillates and then settles down to a steady-state value.

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