scholarly journals Transient behavior of compressed magnetorheological brake excited by step currents

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Hongyun Wang ◽  
Cheng Bi ◽  
Yongju Zhang ◽  
Axiang Ji ◽  
Pengyuan Qiu
Keyword(s):  
Rotational Speed ◽  
Compressive Strain ◽  
Stable Process ◽  
Transient Behavior ◽  
Chain Structure ◽  
Constant Current ◽  
Shear Mode ◽  
Applied Current ◽  
Particle Chain ◽  
Rising Time

AbstractTransient behavior of a magnetorheological brake excited by step currents under compression-shear mode has been experimentally studied. The results show that the amplitude of the applied current had little effect on the rising time of transient torque, while the rising time was significantly affected by the rotational speed, the compressive speed and the compressive strain position. The falling time of transient torque was independent of the amplitude of the applied current, the compressive speed and the compressive strain position, and it was affected by the rotational speed. The falling time of the transient torque was much shorter than the rising time by a step current. The transient process of MR brake applied as a step current was different from a stable process pre-applied at constant current in different particle chain structure forming processes. In addition, the compressive processes applied in one step current and randomly on/off current were compared and experimentally verified: the particle chains in two processes both experienced the same evolutionary of transient torque. The results achieved in this study should be properly considered in the design and control of magnetorheological brake under compression-shear mode.

scholarly journals Estimating Time-Varying Applied Current in the Hodgkin-Huxley Model

2020 ◽  
Vol 10 (2) ◽  
pp. 550
Author(s):  
Kayleigh Campbell ◽  
Laura Staugler ◽  
Andrea Arnold
Keyword(s):  
Kalman Filter ◽  
Standard Deviation ◽  
Ensemble Kalman Filter ◽  
Single Neuron ◽  
Constant Current ◽  
Time Varying ◽  
Applied Current ◽  
Parameter Tracking ◽  
Voltage Spike ◽  
Low Amplitude

The classic Hodgkin-Huxley model is widely used for understanding the electrophysiological dynamics of a single neuron. While applying a low-amplitude constant current to the system results in a single voltage spike, it is possible to produce multiple voltage spikes by applying time-varying currents, which may not be experimentally measurable. The aim of this work is to estimate time-varying applied currents of different deterministic forms given noisy voltage data. In particular, we utilize an augmented ensemble Kalman filter with parameter tracking to estimate four different time-varying applied current parameters and associated Hodgkin-Huxley model states, along with uncertainty bounds in each case. We test the efficiency of the parameter tracking algorithm in this setting by analyzing the effects of changing the standard deviation of the parameter drift and the frequency of data available on the resulting time-varying applied current estimates and related uncertainty.

scholarly journals Probing Slip Differential Heat of Magnetorheological Fluids Subjected to Shear Mode Operation and Its Effect on the Structure

Materials ◽  
2019 ◽  
Vol 12 (11) ◽  
pp. 1860 ◽  
Author(s):  
Song Chen ◽  
Jing Yang
Keyword(s):  
Rotational Speed ◽  
Volume Fraction ◽  
Thermal Structure ◽  
Magnetorheological Fluids ◽  
Input Current ◽  
Shear Mode ◽  
Differential Heat ◽  
Speed Difference ◽  
Mode Operation ◽  
Excitation Coil

The paper probes slip differential heat of magnetorheological fluids (MRFs) subjected to shear mode operation and its effect on the structure. To begin, we present a novel model for measurement of slip differential heat to describe temperature rise of MRFs mainly caused by friction between magnetorheological particles. It includes two stages: (1) The micro-macro analysis of slip differential heat of MRFs including force, movement and heat between neighboring particles based on magnetic dipole and Hertzian contact theories, and (2) the further application to two basic disc-type and cylinder-type magnetorheological clutches combined with finite element simulations involving electromagnetic field and thermal analysis. The model takes into account the effect of each of the main influencing factors, such as the input current of excitation coil, the rotational speed difference of the clutches, the size and volume fraction of particles, the saturation magnetization of particles, and the structural size of the clutches, etc., on the slip differential heat of MRFs. Then the thermal structure analysis of MRFs comprising thermal deformation and equivalent thermal stress is carried out. Moreover, the effect of typical governing parameters on the slip power of MRFs and the influence of slip differential heat on the structure of MRFs are investigated individually. We show that such a model is effective in reflecting the temperature-slip time relation of MRFs. It is shown that the input current and the rotational speed difference have great effect on the slip power, and the slip differential heat has a certain influence on the micro-structure of MRFs.

The effect of some growth-regulating compounds upon electroosmotic measurements, transcellular water flow, and Na, K, and Cl influx in Nitella flexilis

1973 ◽  
Vol 51 (5) ◽  
pp. 1055-1070 ◽  
Author(s):  
I. R. Wanless ◽  
Nancy Bryniak ◽  
D. S. Fensom
Keyword(s):  
Water Flow ◽  
Pond Water ◽  
Basic Flow ◽  
Constant Current ◽  
Naphthaleneacetic Acid ◽  
Applied Current ◽  
Osmotic Effect ◽  
Membrane Complex ◽  
Small Constant ◽  
A Cell

By using a small, constant, applied current on a cell of Nitella in artificial pond water, it was possible to compare the effect of different growth-regulating compounds on the apparent electroosmotic water coupling in the cell wall – membrane complex. Indoleacetic acid (IAA) at first enhanced the electro-osmotic effect and then ceased to alter it, but began to change the asymmetric transcellular water flow. Gibberellic acid (GA), when added to IAA, increased this effect, while abscissic acid (ABA) added to IAA decreased it. Some compounds like naphthaleneacetic acid (NAA), alar-83, skatol, or ABA alone, had no effect on the electroosmotic (eo.) coefficient; but NAA, skatol, ABA (alone) changed the asymmetric water flow (basic flow) and some ion influxes. Light-degraded IAA acted in a manner very similar to skatol, which suggests that IAA is quickly converted to skatol in the cell in the presence of light. With light–dark transitions or with IAA, the electroosmotic coefficient changed in a manner parallel to passive ion (Na+ and K+) influx, but was not related to basic flow or Cl− influx changes.Under controlled conditions of low constant current applied to a test cell, it has been shown that a change in apparent eo. coefficient upon auxin addition is largely a reflection of change in the true electroosmotic properties of the cell membrane at the positive end of the cell.

A Mechanistic Perspective of the Biaxial Strength of Paperboard

1986 ◽  
Vol 108 (2) ◽  
pp. 135-140 ◽  
Author(s):  
Dennis E. Gunderson ◽  
Lee A. Bendtsen ◽  
Robert E. Rowlands
Keyword(s):  
Compressive Strain ◽  
Analytical Models ◽  
Practical Significance ◽  
Shear Mode ◽  
Stress And Strain ◽  
Failure Envelope ◽  
Specific Mechanism ◽  
Plane Shear ◽  
Mode Of Failure ◽  
Failure Conditions

Prior research has demonstrated the practical significance of biaxial strength and established methods for measuring and predicting biaxial properties. Analytical models have been shown to accurately predict failure conditions, but do not identify the mode of failure. The present research develops a method for modeling the biaxial strength of paperboard based on criteria which infer a specific mechanism or mode of failure. In this approach, one or more criteria comprise a model which is evaluated iteratively at multiple states of stress to construct a failure envelope. Analytical results are graphically compared with experimental data. While some models evaluated in this report do not adequately represent the data, one comprised of both stress and strain limiting criteria yields an acceptable fit. We conclude that the modeling approach proposed is practical and useful for distinguishing between “potentially correct” and “inadequate” concepts of biaxial strength. Results suggest that transverse compressive strain may play a role in limiting tensile strength and that paperboard may not fail in an in-plane shear mode unique from normal tensile and compressive failure.

scholarly journals Battery Recharging Issue for a Two-Power-Level Flywheel System

2010 ◽  
Vol 2010 ◽  
pp. 1-5
Author(s):  
Janaína Gonçalves de Oliveira ◽  
Hans Bernhoff
Keyword(s):  
Rotational Speed ◽  
Power Flow ◽  
Power Level ◽  
Average Power ◽  
Current Control ◽  
Constant Current ◽  
Power Electronic Converters ◽  
Closed Loop System ◽  
Main Challenge ◽  
Order Of Magnitude

A novel battery recharging system for an all-electric driveline comprising a flywheel with a permanent magnet double wound synchronous machine (motor/generator) is presented. The double winding enables two voltage levels and two different power levels. This topology supersedes other all-electric drivelines. The battery operates in a low-power regime supplying the average power whereas the flywheel delivers and absorbs power peaks, which are up to a higher order of magnitude. The topology presents new challenges for the power conversion system, which is the focus of this investigation. The main challenge is the control of the power flow to the battery when the vehicle is parked despite the decay of the flywheel machine voltage; which is dependent on its charge state, that is, rotational speed. The design and simulation of an unidirectional DC/DC buck/boost converter for a variable rotational speed flywheel is presented. Conventional power electronic converters are used in a new application, which can maintain a constant current or voltage on the battery side. Successful PI current control has been implemented and simulated, together with the complete closed loop system.

Enhanced Bonding by Applied Current in Cu-to-Cu Joints Fabricated Using 20 μm Cu Microbumps

2017 ◽  
Vol 139 (4) ◽  
Author(s):  
Sung Woo Ma ◽  
Chanho Shin ◽  
Young-Ho Kim
Keyword(s):  
Shear Strength ◽  
Direct Current ◽  
Chain Structure ◽  
Ambient Atmosphere ◽  
Cohesive Failure ◽  
Applied Current ◽  
Enhanced Diffusion ◽  
Cu Bonding ◽  
Si Wafer

The effect of applied current in enhancing bonding was studied in Cu-to-Cu direct bonding using Cu microbumps. A daisy-chain structure of electroplated Cu microbumps (20 μm × 20 μm) was fabricated on Si wafer. Cu-to-Cu bonding was performed in ambient atmosphere at 200–300 °C for 10 min under 260 MPa, during which direct current of 0–10 A (2.5 × 106 A/cm2) was applied. With increasing applied current, the contact resistance decreased and the shear strength in the Cu-to-Cu joints increased. The enhanced bonding imparted by the application of current was ascribed to Joule heating and electromigration effects. Subsequently, the joint temperature was calibrated to isolate the electromigration effects for study. In Cu-to-Cu joints joined at the same adjusted temperature, increasing the current caused unbonded regions to decrease and regions of cohesive failure to increase. The enhanced diffusion across the Cu/Cu interfaces under the applied current was the main mechanism whereby the quality of the Cu-to-Cu joints was improved.

Model Development and Simulation of Transient Behavior of Heavy Duty Gas Turbines

2000 ◽  
Author(s):  
J. H. Kim ◽  
T. W. Song ◽  
T. S. Kim ◽  
S. T. Ro
Keyword(s):  
Rotational Speed ◽  
Gas Turbines ◽  
Guide Vane ◽  
Model Development ◽  
Transient Behavior ◽  
Heavy Duty ◽  
Governing Equations ◽  
Exhaust Temperature ◽  
Fully Implicit ◽  
Integral Forms

This paper describes models for a transient analysis of heavy duty gas turbines, and presents dynamic simulation results of a modern electricity generation engine. Basic governing equations are derived from integral forms of unsteady conservation equations. Mathematical models of each component are described with the aid of unsteady one-dimensional governing equations and steady state component characteristics. Special efforts have been made to predict the compressor characteristics including the effect of movable vanes, which govern the running behavior of the whole engine. The derived equation sets are solved numerically by a fully implicit method. A controller model that maintains constant rotational speed and target temperature (turbine inlet or exhaust temperature) is used to simulate real engine operations. Component models, especially those of the compressor, are validated through a comparison with test data. Simulated is the dynamic behavior of a 150MW class engine. The simulated time-dependent variations of engine parameters such as power, rotational speed, fuel, temperatures and guide vane angles are compared with field data. Simulated results are fairly close to the operation data.

Experimental and numerical studies of squeeze mode behaviour of magnetic fluid

2008 ◽  
Vol 222 (12) ◽  
pp. 2395-2407 ◽  
Author(s):  
N Gstöttenbauer ◽  
A Kainz ◽  
B Manhartsgruber ◽  
R Scheidl
Keyword(s):  
Magnetic Field ◽  
Hysteresis Loops ◽  
Industrial Applications ◽  
Constitutive Laws ◽  
Shear Mode ◽  
Mr Fluid ◽  
Carrier Fluid ◽  
Particle Chain ◽  
Semi Solid ◽  
Fluid Behaviour

Magneto-rheological (MR) fluids are suspensions of micron-sized ferromagnetic particles in a non-magnetic carrier fluid. The essential characteristic of MR fluid is the rapid and reversible transition from the state of a Newtonian-like fluid to the behaviour of a stiff semi-solid by applying a magnetic field of ∼0.1–0.4 T. This feature can be understood from the fact that the particles form chain-like structures aligned in the field direction. The MR fluid offers three modes of operation, namely the direct shear mode, the valve mode, and the squeeze mode. The latter is of particular interest due to its highly non-linear behaviour, which is still not fully understood and therefore expected to give rise to new industrial applications. A test rig for the exploration of the MR-fluid behaviour was designed for experimental purposes. The present article describes the results of measurements under sinusoidal loading modes. Special emphasis was posed on the dependence of the MR-fluid response with respect to parameter variations of the applied static magnetic field, the cyclic loading amplitude, and frequency values. Cavitation effects have been investigated and partially suppressed by pre-pressurizing the MR fluid, which enables a more thorough insight into particle chain disruption and segregation effects. Well-pronounced hysteresis loops are observed and exhibit characteristic kinks, which cannot be understood within the frame of elementary constitutive laws such as for Bingham fluids. To describe the squeeze mode phenomenon numerically, adequate constitutive laws were applied, checked numerically by utilizing finite-element simulations, and validated against experimental data. New perceptions attained so far provided reason to design an adaptive MR-fluid bearing in squeeze mode behaviour for industrial applications.

Visualization Study on Chain Structure in Electro-Rheological Fluids

1999 ◽  
Vol 13 (14n16) ◽  
pp. 1783-1790 ◽  
Author(s):  
Takeshi Tomiuga ◽  
Koji Okamoto ◽  
Haruki Madarame
Keyword(s):  
Electric Field ◽  
Apparent Viscosity ◽  
Flow Resistance ◽  
Laser Light ◽  
Light Sheet ◽  
Chain Structure ◽  
Laser Light Sheet ◽  
Particle Chain ◽  
Experimental Apparatus ◽  
Er Fluids

The electrorheological (ER) effect is known as a phenomenon that shows reversible increase of apparent viscosity by applied electric field. The electric field induces the particle polarization, resulting in the chains between the electrodes. In this study, the ER fluids in the channel with two parallel electrodes were visualized under the pressure flow. The laser light sheet and transparent electrodes were used in the experimental apparatus to visualize the particles under 10wt% concentration. The particle chain structure in the channel was clearly visualized. Under higher voltage condition, particle layers were formed at the neighbor of the electrodes. Processing the visualized images, the effects of the chain structure and the layer on the flow resistance were investigated.

scholarly journals Electrodeposition of Calcium Carbonate and Magnesium Carbonate from Hard Water on Stainless-Steel Electrode to Prevent Natural Scaling Phenomenon

Water ◽  
2021 ◽  
Vol 13 (19) ◽  
pp. 2752
Author(s):  
Faléstine Souiad ◽  
Yasmina Bendaoud-Boulahlib ◽  
Ana Sofia Rodrigues ◽  
Annabel Fernandes ◽  
Lurdes Ciríaco ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Deposition Rate ◽  
Inorganic Carbon ◽  
Hard Water ◽  
Current Intensity ◽  
Constant Current ◽  
Stainless Steel Electrode ◽  
Electrode Position ◽  
Applied Current ◽  
Steel Electrode

This study focuses on preventing scale formation in hard waters by controlled electrode-position of Ca2+ and Mg2+ on a stainless-steel cathode at constant applied current intensity. The influence of the anode material, BDD or Ti/Pt/PbO2, cathode active area, stirring speed, and applied anodic current intensity on the inorganic carbon (IC), Ca2+, and Mg2+ removal was investigated. Assays were performed with model hard water solutions, simulating Bounouara (Algeria) water. The scaling inhibiting properties of the treated water were followed by measuring IC, calcium, and magnesium concentrations and chronoamperometric characterization of the treated solutions. The influence of the Ca/Mg molar ratio on the inorganic carbon removal by electrolysis was also evaluated, utilizing model solutions with different compositions. It was found that an increase in stirring speed or cathode geometric area favors IC and Ca2+ and Mg2+ removal rates. The applied current intensity was varied from 0.025 to 0.5 A, and the best results were obtained for 0.1 A, either in IC and Ca2+ and Mg2+ removals or by the accelerated scaling tests. However, energy costs increase with applied current. The deposit formed over the cathode does not seem to influence posterior deposition rate, and after eight consecutive assays, the solid deposition rate was kept constant. Ca/Mg ratio influences IC removal rate that increases with it. The results showed that hard-water scaling phenomena can be prevented by solid electrodeposition on the cathode at applied constant current.

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