A Simple Dynamic Modeling of Head Slap in Hard Disk Drive

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.

Gravitational effects on ocular pressure and perfusion pressure

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.

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

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

&lt;p&gt;Satellite-based UV spectrometers can constrain sulphur dioxide (SO&lt;sub&gt;2&lt;/sub&gt;) fluxes at passively degassing volcanoes over decadal time scales. From 2005 to 2015, more than 15 volcanoes had mean passive SO&lt;sub&gt;2 &lt;/sub&gt;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&amp;#8217;s surface. Passive degassing may depressurize pathways between deep and shallow magma storage regions, resulting in magma ascent and possibly eruption.&lt;/p&gt;&lt;p&gt;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&amp;#8217;s top passive emitter of volcanic SO&lt;sub&gt;2&lt;/sub&gt;, which exhibits intriguing long-term subsidence patterns and no obvious pressurization preceding eruptive periods. We compare subsidence rates measured by InSAR to the system&amp;#8217;s average daily SO&lt;sub&gt;2&lt;/sub&gt; 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&amp;#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 km&lt;sup&gt;3&lt;/sup&gt;) 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.&lt;/p&gt;

Study on Vertical Earth Pressure of Slab Culvert under High Embankment

2012 ◽  
Vol 256-259 ◽  
pp. 1898-1902 ◽  
Author(s):  
Bao Kuan Ning ◽  
He Fan ◽  
Lei Gong ◽  
Guo Qing Liu
Keyword(s):  
Numerical Simulation ◽  
Boundary Conditions ◽  
Field Test ◽  
Structural Design ◽  
Earth Pressure ◽  
Test Results ◽  
Soil Pressure ◽  
Vertical Earth Pressure ◽  
The Impact ◽  
Good Agreement

With the increasing of embankment culvert engineering applications, there has been due in part to the structural design is too conservative and not economic or select unreasonable structural form, leading to the phenomenon of cracking or even collapse of the culvert structure, and the phenomenon has seriously affected the normal use of the highway. In this paper, the numerical simulation of vertical earth pressure distribution on different structural forms of embankment on culverts, to discuss the impact of boundary conditions, fill height, the thickness of the culvert culverts vertical earth pressure. Combined with Heda highway a culvert covert field test results and numerical simulation results were compared and analyzed. The results show that the numerical simulation and field test results in good agreement with the culvert structure in the form of vertical earth pressure of the embankment culverts have a greater impact; the structure of different forms of the culvert in the upper soil pressure is significantly different. In addition, analysis of the impact of boundary conditions, filling height of culvert vertical earth pressure values. The results can reference for the study of the structural design of the embankment culverts security.

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

2008 ◽  
Vol 295 (6) ◽  
pp. H2427-H2435 ◽  
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.

Datacenter Scale Evaluation of the Impact of Temperature on Hard Disk Drive Failures

2013 ◽  
Vol 9 (2) ◽  
pp. 1-24 ◽  
Author(s):  
Sriram Sankar ◽  
Mark Shaw ◽  
Kushagra Vaid ◽  
Sudhanva Gurumurthi
Keyword(s):  
Hard Disk Drive ◽  
Hard Disk ◽  
Disk Drive ◽  
Scale Evaluation ◽  
The Impact

scholarly journals A New Lumped Approach for the Simulation of the Magnetron Injection Gun for MegaWatt-Class EU Gyrotrons

Energies ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 2068
Author(s):  
Nicolò Badodi ◽  
Antonio Cammi ◽  
Alberto Leggieri ◽  
Francisco Sanchez ◽  
Laura Savoldi
Keyword(s):  
High Frequency ◽  
Electron Cyclotron Resonance ◽  
Lumped Parameter Model ◽  
Electron Cyclotron Resonance Heating ◽  
Test Results ◽  
Radio Waves ◽  
Magnetron Injection Gun ◽  
Thermal Dynamics ◽  
Lumped Parameter ◽  
Current Emission

In the framework of the ITER (International Thermonuclear Experimental Reactor) project, one of the key components of the reactor is the ECRH (Electron Cyclotron Resonance Heating). This system has the duty to heat the plasma inside the tokamak, using high frequency and power radio waves, produced by sets of 1MW gyrotrons. One of the main issues related to the gyrotron operation is the output power drop that happens right after the beginning of a pulse. In this work, we study the underlying phenomena that cause the power drop, focusing on the gyrotron’s MIG (Magnetron Injection Gun) of the 1MW, 170 GHz European Gyrotron prototype for ITER. It is shown how the current emission and the temperature of the emitter are tightly bound, and how their interaction causes the power drop, observed experimentally. Furthermore, a simple yet effective lumped-parameter model to describe the MIG’s cathode thermal dynamics is developed, which is able to predict the power output of the gyrotron by simulating the propagation of the heat inside this component. The model is validated against test results, showing a good capability to reproduce the measured behavior of the system, while still being open to further improvements.

scholarly journals Optimal Occupant Kinematics and Crash Pulse for Automobile Frontal Impact

2009 ◽  
Vol 16 (1) ◽  
pp. 61-73 ◽  
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.

Dynamic Modeling of a Monopropellant-Based Chemofluidic Actuation System

2006 ◽  
Vol 129 (4) ◽  
pp. 435-445 ◽  
Author(s):  
Navneet Gulati ◽  
Eric J. Barth
Keyword(s):  
Dynamic Modeling ◽  
Power Supply ◽  
Gas Dynamics ◽  
Flow Dynamics ◽  
Lumped Parameter Model ◽  
Human Scale ◽  
Actuation System ◽  
Lumped Parameter ◽  
Viable System ◽  
Power And Energy

This paper presents a dynamic model of a monopropellant-based chemofluidic power supply and actuation system. The proposed power supply and actuation system, as presented in prior works, is motivated by the current lack of a viable system that can provide adequate energetic autonomy to human-scale power-comparable untethered robotic systems. As such, the dynamic modeling presented herein is from an energetic standpoint by considering the power and energy exchanged and stored in the basic constituents of the system. Two design configurations of the actuation system are presented and both are modeled. A first-principle based lumped-parameter model characterizing reaction dynamics, hydraulic flow dynamics, pneumatic flow dynamics, and compressible gas dynamics is developed for purposes of control design. Experimental results are presented that validate the model.

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