EFFECT OF SURFACE LAYER ON ELECTROMECHANICAL STABILITY OF TWEEZERS AND CANTILEVERS FABRICATED FROM CONDUCTIVE CYLINDRICAL NANOWIRES

Herein, the impact of surface layer on the stability of nanoscale tweezers and cantilevers fabricated from nanowires with cylindrical cross section is studied. A modified continuum based on the Gurtin–Murdoch surface elasticity is applied for incorporating the presence of surface layer. Considering the cylindrical geometry of the nanowire, the presence of the Coulomb attraction and dispersion forces are incorporated in the derived formulations. Three different approaches, i.e. numerical differential quadrature method (DQM), an approximated homotopy perturbation method (HPM) and developing lumped parameter model (LPM) have been employed to solve the governing equations. The impact of surface layer on the instability of the system is demonstrated.

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A Simple Dynamic Modeling of Head Slap in Hard Disk Drive

Volume 6B: 18th Biennial Conference on Mechanical Vibration and Noise ◽

10.1115/detc2001/vib-21503 ◽

2001 ◽

Author(s):

Seong-Hun Lee ◽

Jeong-Hak Lee ◽

Kwang-Joon Kim

Keyword(s):

Hard Disk Drive ◽

Dynamic Modeling ◽

Structural Design ◽

Continuous System ◽

Disk Drive ◽

Lumped Parameter Model ◽

Test Results ◽

Lumped Parameter ◽

Shock Resistance ◽

The Impact

Abstract In order to understand mechanism of the impact between head and disk of a HDD subject to a shock and to improve the shock resistance effectively, it is essential to develop a dynamic model which can represent well the head slap. Although motion of the head and disk subject to a shock requires modeling by a continuous system to be rigorous, in this study, a simplified lumped parameter model is developed to understand basic dynamics of the head slap and to determine crucial parameters for the improvement of the structural design. In addition, drop test results of the HDD are presented to back to up the derived model.

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Mitigation of Biodynamic Response to Shock Loads Using Semi-Active Vertically Stroking Crew Seats

ASME 2010 Conference on Smart Materials, Adaptive Structures and Intelligent Systems, Volume 2 ◽

10.1115/smasis2010-3857 ◽

2010 ◽

Author(s):

Harinder J. Singh ◽

Norman M. Wereley

Keyword(s):

Human Body ◽

Control Algorithm ◽

Equations Of Motion ◽

Comprehensive Analysis ◽

Lumped Parameter Model ◽

Force Model ◽

Body Parts ◽

Governing Equations ◽

Lumped Parameter ◽

Yield Force

This study addresses mitigation of biodynamic response due to an initial velocity impact of a vertically stroking crew seat using an adaptive magnetorheological energy absorber. Under consideration is a multiple degree-of-freedom detailed lumped parameter model of a human body falling with prescribed initial crash velocity (sink rate). The lumped parameter model of the human body consisted of four main parts: pelvis, upper torso, viscera and head. The governing equations of motion of a vertically stroking crew seat incorporating a human body were derived using parameters such as available damper stroke as well as MR yield force. The control algorithm for smooth landing of a rigid occupant was examined for compliant occupant and was modified accordingly. Four MR yield force models were analyzed to shape decelerations experienced by human body and an appropriate model was selected for comprehensive analysis. The simulated responses were analyzed with selected MR yield force model for a crew seat with an occupant corresponding to 90th percentile male at sink rates varying from 8 to 12 m/s. In addition, the mitigation of injuries to the human body parts due to load transmissions corresponding to crash velocities was also evaluated for the selected MR yield force model along with terminal conditions necessary for smooth landing.

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Gravitational effects on ocular pressure and perfusion pressure

Journal of Applied Physiology ◽

10.1152/japplphysiol.00546.2021 ◽

2021 ◽

Author(s):

Lonnie G. Petersen ◽

Richard Stuart Whittle ◽

Justin Hyunwoo Lee ◽

Jeremy Sieker ◽

Joseph Carlson ◽

...

Keyword(s):

Supine Position ◽

Perfusion Pressure ◽

Lumped Parameter Model ◽

Lumped Parameter ◽

Postural Changes ◽

Gravitational Stress ◽

Gravitational Vector ◽

Head Up Tilt ◽

The Impact ◽

Ocular Hemodynamics

Changes in the gravitational vector by postural changes or weightlessness induce fluid shifts impacting ocular hemodynamics and regional pressures. This investigation explores the impact of changes in direction of the gravitational vector on intraocular pressure (IOP), mean arterial pressure at eyelevel (MAPeye), and ocular perfusion pressure (OPP), which is critical for ocular health. Thirteen subjects underwent 360° of tilt (including both prone and supine positions) at 15º increments. At each angle, steady-state IOP and MAPeye were measured and OPP calculated as MAPeye-IOP. Experimental data were compared to a 6-compartment lumped parameter model of the eye. Mean IOP, MAPeye, and OPP significantly increased from 0º supine to 90º head down tilt (HDT) by 20.7±1.7 mmHg (ᵅD; < 0.001), 38.5±4.1 mmHg (ᵅD; < 0.001), and 17.4±3.2 mmHg (ᵅD; <0.001), respectively. Head up tilt (HUT) significantly decreased OPP by 16.5±2.5 mmHg (ᵅD; < 0.001). IOP was significantly higher in prone vs. supine position for much of the tilt range. Our study indicates that OPP is highly gravitationally dependent. Specifically, data show that MAPeye is more gravitationally dependent than IOP, thus causing OPP to increase during HDT and to decrease during HUT. Additionally, IOP was elevated in prone position compared to supine position due to the additional hydrostatic column between the base of the rostral globe to the mid-caudal plane, supporting the notion that hydrostatic forces play an important role in ocular hemodynamics. Changes in OPP as a function of changes in gravitational stress and/or weightlessness may play a role in the pathogenesis of spaceflight-associated neuro-ocular syndrome.

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Can high rates of passive volcanic gas emissions induce reservoir depressurization at Ambrym volcano (Vanuatu)?

10.5194/egusphere-egu21-7998 ◽

2021 ◽

Author(s):

Tara Shreve ◽

Raphaël Grandin ◽

Marie Boichu

Keyword(s):

Ground Deformation ◽

Lumped Parameter Model ◽

Magma Ascent ◽

Large Reservoir ◽

Gas Emissions ◽

Volcanic System ◽

Lumped Parameter ◽

Gas Geochemistry ◽

The Impact

Satellite-based UV spectrometers can constrain sulphur dioxide (SO2) fluxes at passively degassing volcanoes over decadal time scales. From 2005 to 2015, more than 15 volcanoes had mean passive SO2 fluxes greater than 1 kiloton per day. Although the processes responsible for such high emission rates are not clearly established, this study aims to investigate the impact of strong degassing on the pressurization state of volcanic systems and the resulting ground deformation. One possible result of high degassing rates is the depressurization of the region where the melt releasing gas is stored, which may result in subsidence at the Earth&#8217;s surface. Passive degassing may depressurize pathways between deep and shallow magma storage regions, resulting in magma ascent and possibly eruption.A lumped-parameter model developed by Girona et al., 2014 couples the mass loss by passive degassing with reservoir depressurization in an open volcanic system. However, this model has yet to be tested using real measurements of gas emissions and ground deformation. In our study, we focus on Ambrym volcano, the past decade&#8217;s top passive emitter of volcanic SO2, which exhibits intriguing long-term subsidence patterns and no obvious pressurization preceding eruptive periods. We compare subsidence rates measured by InSAR to the system&#8217;s average daily SO2 flux, focusing on a subsidence episode spanning 2015 to 2017 that is not clearly linked to magma removal from the system. Using realistic input parameters for Ambrym&#8217;s system constrained by petrology and gas geochemistry, a range of reservoir volumes and conduit radii are explored. Large reservoir volumes (greater than 30 km3) and large conduit radii (greater than 300 m) are consistent with depressurization rates obtained from geodetic modelling of InSAR measurements using the Boundary Element method. By comparing these values of reservoir volume and conduit radius with those estimated from geodesy, gas geochemistry, and seismology, we test the applicability and discuss uncertainties of the aforementioned lumped-parameter physical model to interpret the long-term subsidence at Ambrym volcano as a result of sustained passive degassing.

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The total cavopulmonary connection resistance: a significant impact on single ventricle hemodynamics at rest and exercise

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.00628.2008 ◽

2008 ◽

Vol 295 (6) ◽

pp. H2427-H2435 ◽

Cited By ~ 82

Author(s):

Kartik S. Sundareswaran ◽

Kerem Pekkan ◽

Lakshmi P. Dasi ◽

Kevin Whitehead ◽

Shiva Sharma ◽

...

Keyword(s):

Heart Rate ◽

Single Ventricle ◽

Fluid Dynamic ◽

Three Dimensional ◽

Lumped Parameter Model ◽

Total Cavopulmonary Connection ◽

Dynamic Simulations ◽

Lumped Parameter ◽

The Impact ◽

Cavopulmonary Connection

Little is known about the impact of the total cavopulmonary connection (TCPC) on resting and exercise hemodynamics in a single ventricle (SV) circulation. The aim of this study was to elucidate this mechanism using a lumped parameter model of the SV circulation. Pulmonary vascular resistance (1.96 ± 0.80 WU) and systemic vascular resistances (18.4 ± 7.2 WU) were obtained from catheterization data on 40 patients with a TCPC. TCPC resistances (0.39 ± 0.26 WU) were established using computational fluid dynamic simulations conducted on anatomically accurate three-dimensional models reconstructed from MRI ( n = 16). These parameters were used in a lumped parameter model of the SV circulation to investigate the impact of TCPC resistance on SV hemodynamics under resting and exercise conditions. A biventricular model was used for comparison. For a biventricular circulation, the cardiac output (CO) dependence on TCPC resistance was negligible (sensitivity = −0.064 l·min−1·WU−1) but not for the SV circulation (sensitivity = −0.88 l·min−1·WU−1). The capacity to increase CO with heart rate was also severely reduced for the SV. At a simulated heart rate of 150 beats/min, the SV patient with the highest resistance (1.08 WU) had a significantly lower increase in CO (20.5%) compared with the SV patient with the lowest resistance (50%) and normal circulation (119%). This was due to the increased afterload (+35%) and decreased preload (−12%) associated with the SV circulation. In conclusion, TCPC resistance has a significant impact on resting hemodynamics and the exercise capacity of patients with a SV physiology.

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Optimal Occupant Kinematics and Crash Pulse for Automobile Frontal Impact

Shock and Vibration ◽

10.1155/2009/290405 ◽

2009 ◽

Vol 16 (1) ◽

pp. 61-73 ◽

Cited By ~ 2

Author(s):

Zhiqing Cheng ◽

Joseph A. Pellettiere ◽

Jeff R. Crandall ◽

Walter D. Pilkey

Keyword(s):

Lumped Parameter Model ◽

Frontal Impact ◽

Vehicle Interior ◽

Impact Speed ◽

Vehicle System ◽

Lumped Parameter ◽

Passive Restraint ◽

System Optimal ◽

Occupant Kinematics ◽

The Impact

Based on a lumped-parameter model of the occupant-vehicle system, optimal kinematics of the occupant in frontal impact are investigated. It is found that for the minimization of the peak occupant deceleration, the optimal kinematics move the occupant at a constant deceleration. Based on this the optimal vehicle crash pulse is investigated. The optimal crash pulse for passive restraint systems is found to be: a positive impulse at the onset, an immediate plunge followed by a gradual rebound, and finally a positive level period. The relation of the peak occupant deceleration to the impact speed, crash deformation, and vehicle interior rattlespace is established. The optimal crash pulse for active and pre-acting restraint systems is discussed.

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Characterization of Giant Magnetostrictive Materials Using Three Complex Material Parameters by Particle Swarm Optimization

Micromachines ◽

10.3390/mi12111416 ◽

2021 ◽

Vol 12 (11) ◽

pp. 1416

Author(s):

Yukai Chen ◽

Xin Yang ◽

Mingzhi Yang ◽

Yanfei Wei ◽

Haobin Zheng

Keyword(s):

Classical Method ◽

Lumped Parameter Model ◽

Complex Material ◽

Material Parameters ◽

Magnetostrictive Materials ◽

Lumped Parameter ◽

Giant Magnetostrictive Materials ◽

Power Transducer ◽

And Performance ◽

The Stability

Complex material parameters that can represent the losses of giant magnetostrictive materials (GMMs) are the key parameters for high-power transducer design and performance analysis. Since the GMMs work under pre-stress conditions and their performance is highly sensitive to pre-stress, the complex parameters of a GMM are preferably characterized in a specific pre-stress condition. In this study, an optimized characterization method for GMMs is proposed using three complex material parameters. Firstly, a lumped parameter model is improved for a longitudinal transducer by incorporating three material losses. Then, the structural damping and contact damping are experimentally measured and applied to confine the parametric variance ranges. Using the improved lumped parameter model, the real parts of the three key material parameters are characterized by fitting the experimental impedance data while the imaginary parts are separately extracted by the phase data. The global sensitivity analysis that accounts for the interaction effects of the multiple parameter variances shows that the proposed method outperforms the classical method as the sensitivities of all the six key parameters to both impedance and phase fitness functions are all high, which implies that the extracted material complex parameters are credible. In addition, the stability and credibility of the proposed parameter characterization is further corroborated by the results of ten random characterizations.

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Dynamic Response of a Cam-Actuated Mechanism With Pneumatic Coupling

Journal of Engineering for Industry ◽

10.1115/1.3439284 ◽

1977 ◽

Vol 99 (3) ◽

pp. 598-603 ◽

Cited By ~ 3

Author(s):

F. Y. Chen

Keyword(s):

Dynamic Response ◽

Dynamic Characteristics ◽

Lumped Parameter Model ◽

System Equation ◽

Variation Of Parameters ◽

Lumped Parameter ◽

Cam Follower ◽

The Stability

The dynamic characteristics of a cam-actuated system whose follower mass is coupled with a nonlinear pneumatic mechanism of hysteretic type are investigated using a lumped-parameter model. The dynamic response of the cam follower is obtained from the solution of the formulated system equation by the Krylov-Bogoliubov method of variation of parameters. The stability of the system is also investigated.

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Theoretical Analysis and Optimization of a Gloved Hand-arm System

Journal of Biomechanical Engineering ◽

10.1115/1.4051662 ◽

2021 ◽

Author(s):

Oreoluwa Alabi ◽

Sunit Kumar Gupta ◽

Oumar Barry

Keyword(s):

Harmonic Balance ◽

Equations Of Motion ◽

Biomechanical Model ◽

Lumped Parameter Model ◽

Human Hand ◽

Governing Equations ◽

Lumped Parameter ◽

Hand Tool ◽

Modeling Techniques ◽

Linear Spring

Abstract Studies have shown that isolators in the form of anti-vibration gloves effectively reduce the transmission of unwanted vibration from vibrating equipment to the human hand. However, as most of these studies are based on experimental or modeling techniques, the level of effectiveness and optimum glove properties for better performance remains unclear. To fill this gap, hand-arm system dynamics with and without gloves are studied analytically in this work. In the current work, we use a lumped parameter model of the hand-arm system, with hand-tool interaction modeled as a linear spring-damper system. The resulting governing equations of motion are solved analytically using the method of harmonic balance. Parametric analysisis performed on the biomechanical model of the hand-armsystem with and without a glove to identify key design pa-rameters. It is observed that the effect of glove parameters on its performance is not repetitive and changes in the studied different frequency ranges. This observation further motivates us to optimize the glove parameters to minimize the overall transmissibility in different frequency ranges.

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Mode-Coupled Regenerative Machine Tool Vibrations

Volume 5: 19th Biennial Conference on Mechanical Vibration and Noise, Parts A, B, and C ◽

10.1115/detc2003/vib-48576 ◽

2003 ◽

Author(s):

Tama´s Kalma´r-Nagy ◽

Francis C. Moon

Keyword(s):

Machine Tool ◽

Cutting Tool ◽

Chip Thickness ◽

The Other ◽

Lumped Parameter Model ◽

Regenerative Effect ◽

Lumped Parameter ◽

Tool Vibrations ◽

The Stability ◽

Effect Time

In this paper a new 3 degree-of-freedom lumped-parameter model for machine tool vibrations is developed and analyzed. One mode is shown to be stable and decoupled from the other two, and thus the stability of the system can be determined by analyzing the remaining two modes. It is shown that this mode-coupled nonconservative cutting tool model including the regenerative effect (time delay) can produce an instability criteria that admits low-level or zero chip thickness chatter.

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