Kinetic Energy Curves Research Articles

Reduced order modelling using neural networks for predictive modelling of 3d-magneto-mechanical problems with application to magnetic resonance imaging scanners

The design of magnets for magnetic resonance imaging (MRI) scanners requires the numerical simulation of a coupled magneto-mechanical system where the effects that different material parameters and in-service loading conditions have on both imaging and MRI performance are key to aid with the design and the manufacturing process. To correctly capture the complex physics, and to obtain accurate solutions, finite element simulations with dense meshes and high order elements are needed. Reduced order model approaches, based on the established proper orthogonal decomposition (POD) approach, are attractive as they can rapidly predict the numerical simulations needed under changing parameters or conditions. However, the projected (PODP) approach has an invasive computational implementation, whilst the interpolated (PODI) approach presents challenges when the dimension of the space of parameters to be investigated becomes large. As an alternative, we investigate a POD technique based on using a neural network regression, which is not as invasive as PODP, but has superior approximation properties compared to PODI. We apply this to the coupled magneto-mechanical system to understand three pressing industrial problems: firstly, the accurate and rapid computation of the resonant frequencies associated with this coupled magneto-mechanical system, secondly, the effects of magnet motion on the Ohmic power and kinetic energy curves, and, thirdly, the prediction of the uncertainty in Ohmic power and kinetic energy curves as a function of exciting frequency for uncertain material parameters.

Longitudinal Changes in Left Ventricular Blood Flow Kinetic Energy After Myocardial Infarction: Predictive Relevance for Cardiac Remodeling

Shows representative kinetic energy curves throughout the cardiac cycle of 2 separate patients, acquired at (12 months [V3]). The left panel shows a patient with preserved ejection fraction (pEF), while the panel on the right shows a patient with reduced ejection fraction (rEF). flow vectors at peak-systole, PeakE-wave and PeakA-wave indexed for EDV for each patient is shown underneath. The patient with rEF has higher systolic KEiEDV, lower PeakE-wave KEiEDV and higher PeakA-wave KEiEDV. by Hadar Ben-Arzi et al. (768–778)

The phase shift between potential and kinetic energy in human walking.

It is known that mechanical work to sustain walking is reduced, owing to a transfer of gravitational potential energy into kinetic energy, as in a pendulum. The factors affecting this transfer are unclear. In particular, the phase relationship between potential and kinetic energy curves of the center of mass is not known. In this study, we measured this relationship. The normalized time intervals α, between the maximum kinetic energy in the sagittal plane (Ek) and the minimum gravitational potential energy (Ep), and β, between the minimum Ek and the maximum Ep, were measured during walking at various speeds (0.5-2.5 m s-1). In our group of subjects, α=β at 1.6 m s-1, indicating that, at this speed, the time difference between Ep and Ek extremes is the same at the top and the bottom of the trajectory of the center of mass. It turns out that, at the same speed, the work done to lift the center of mass equals the work to accelerate it forwards, the Ep-Ek energy transfer approaches a maximum and the mass-specific external work per unit distance approaches a minimum.

On the protective capacity of a safety vest for the thoracic injury caused by falling down

BackgroundAged people all over the world are prone to fall down accidentally and be injured with fracture, such as the rib fracture. To protect the elderly, the safety vest has been developed to protect them from being injured when falling down. To effectively protect the elderly, more analysis on the protective capacity of a safety vest under different situation are needed.ResultsHerein, a finite element model based on the computed tomography CT scanning data of a Chinese old female was built, and then used to simulate the process of falling down at different velocities. Analysis and comparison were done on the maximum shear stress, kinetic energy curves and internal energy curves with and without safety vest. The maximum shear stress indicated that the Abbreviated Injury Scale (AIS) 2+ injury risks of rib were 8%, 100% and 100% at the velocities of 1.5 m/s, 2.0 m/s and 2.5 m/s, respectively. The corresponding risks were lowered to 0%, 0% and 60% by the vest, respectively. Furthermore, the vest could absorb the internal energy resulted by the deformation of the thoracic osseous tissue by about 20%, thus decreasing the shear stress and the injury risk.ConclusionIt is concluded that the safety vest decreases the injury risk when the elderly fall down, thus protects them from being injured.

Thermoviscous fluid flow modes in a plane nonisothermal layer

This paper deals with 3D flow of thermoviscous fluid in the low compressibility approximation within a cubic-shaped domain enclosed between two flat plates with different temperatures. For two other directions, the problem statement assigns periodic boundary conditions, while the steady pressure drop is sustained for the head flow direction. Such formulation allows to trace the evolution of initial disturbances imposed on the main flow depending on perturba-tion properties. In this case, we consider a degenerate one-dimensional divergence-free noise that is modified by a special correlation filter. When the divergent noise is generated, the solenoid nature of random velocity field must be restored. The simulation demonstrates that random disturbance field development leads to two different scenarios: for the first low-amplitude case, the velocity profile loses initial inflection point and its flowrate increases by 1.5–1.6 times, but for the second one, the flow turbulization occurs destroying the flow core and decreasing the flowrate. In both outcomes, the transition to a steady flow mode in terms of either stationary velocity fields or statistical averag-es takes place for a long interval: up to t~200 dimensionless time units. The analysis of simulated flow is based on integral kinetic energy curves and enstrophy and also via spatial averaging of the obtained data arrays.

Unstable footwear as a speed-dependent noise-based training gear to exercise inverted pendulum motion during walking

ABSTRACTPrevious research on unstable footwear has suggested that it may induce mechanical noise during walking. The purpose of this study was to explore whether unstable footwear could be considered as a noise-based training gear to exercise body center of mass (CoM) motion during walking. Ground reaction forces were collected among 24 healthy young women walking at speeds between 3 and 6 km h−1 with control running shoes and unstable rocker-bottom shoes. The external mechanical work, the recovery of mechanical energy of the CoM during and within the step cycles, and the phase shift between potential and kinetic energy curves of the CoM were computed. Our findings support the idea that unstable rocker-bottom footwear could serve as a speed-dependent noise-based training gear to exercise CoM motion during walking. At slow speed, it acts as a stochastic resonance or facilitator that reduces external mechanical work; whereas at brisk speed it acts as a constraint that increases external mechanical work and could mimic a downhill slope.

Falling Simulation of Free-Standing Museum Cultural Relics Supported by Soft Pad

Free-standing museum cultural relics are easy to fall off exhibition booth and get damaged under earthquakes. To find an effective method to mitigate damage of cultural relics due to fall off, influences of soft pad under relic was studied by ANSYS/LS-DYNA program. A bronze relic supported by a soft pad was selected for analysis. Based on material properties of both the relic and the pad, finite element model of the relic was built. By simulation, Von mises stress distributions, acceleration response curves as well as kinetic energy curves of the relic were obtained; effects of the soft pad to mitigate damage of the relic were discussed. Results show that collision between the falling museum cultural relic and ground can be mitigated by soft pad due to its buffer as well as energy absorption effects. It is suggested to use soft pad under relic to provide protection. Besides, by ANSYS/LS-DYNA program, falling off process of free-standing museum cultural relics can be effectively simulated.

Analysis of Anti-Riot Helmet Material Based on Numerical Simulation

Focusing on the problem that the modern anti-riot helmet has been revealed a number of deficiencies such as poor performance under impact, the material of helmet shell is analyzed based on numerical simulation in this paper. A finite element model of anti-riot helmet and simple finite element models of head, trunk and blunt object are established by CAD software and ABAQUS software. PP, PC and ABS are chosen as three different engineering plastics for anti-riot helmet shell material, and then carry a numerically simulation on the process of anti-riot helmet impact moment. Results show that the overall system kinetic energy curves present overall downward trends firstly, then present irregular waves with smaller ups and downs. PC is a more excellent helmet material while comparing to PP and ABS.

Virtual Impact Test for Aluminum-Alloy Wheel Based on Numerical Simulation Method

The mechanical properties of car wheel mast have high reliability requirements. The impact test for trial casting aluminum alloy wheel must be passed, which is one of the bench tests. Based the practical case, the integrated finite-element model for virtual test is established, including impact block, wheel, tire, bracket, rubber pad, the standard test load conditions are imposed, and the entire impact process was simulated by finite-element method, the velocity, displacement and kinetic energy curves of the impact block, the stress distribution and the impact force curve of change were obtained. Moreover, using in a typical case, compared with the physical impact test, the model and procedure of the finite-element numerical simulation was verified. The modeling method and calculation procedure given can guide the virtual design of aluminum-alloy wheel, the blindness of design can be reduced, and the development work efficiency can be increased.

Virtual Impact Test for Aluminum-Alloy Wheel Based on Numerical Simulation Method

The mechanical properties of car wheel mast have high reliability requirements. The impact test for trial casting aluminum alloy wheel must be passed, which is one of the bench tests. Based the practical case, the integrated finite-element model for virtual test is established, including impact block, wheel, tire, bracket, rubber pad, the standard test load conditions are imposed, and the entire impact process was simulated by finite-element method, the velocity, displacement and kinetic energy curves of the impact block, the stress distribution and the impact force curve of change were obtained. Moreover, using in a typical case, compared with the physical impact test, the model and procedure of the finite-element numerical simulation was verified. The modeling method and calculation procedure given can guide the virtual design of aluminum-alloy wheel, the blindness of design can be reduced, and the development work efficiency can be increased.

Mechanical energy fluctuations during hill walking: the effects of slope on inverted pendulum exchange

Humans and other animals exchange gravitational potential energy (GPE) and kinetic energy (KE) of the center of mass during level walking. How effective is this energy exchange during downhill and uphill walking? Based on previous reports and our own reasoning, we expected that during downhill walking, the possibility for mechanical energy exchange would be enhanced and during uphill walking, the possibility for exchange would be reduced. We measured the fluctuations of the mechanical energies for five men and five women walking at 1.25 m s(-1). Subjects walked on the level, downhill, and uphill on a force measuring treadmill mounted at 3 degrees, 6 degrees and 9 degrees. We evaluated energy exchange during the single support period based on the GPE and KE fluctuation factors of phase relationship, relative magnitude and extent of symmetry. As expected, during level walking, the GPE and KE curves were out of phase, of similar magnitude, and nearly mirror images so that the fluctuations in combined (GPE+KE) energy were attenuated. During downhill walking, the fluctuations in the combined energy of the center of mass were smaller than those on the level, i.e. mechanical energy exchange was more effective. During uphill walking, the fluctuations in the combined energy of the center of mass were larger than those on the level, i.e. mechanical energy exchange was less effective. Mechanical energy exchange occurred during downhill, level and uphill walking, but it was most effective during downhill walking.

Landau and Ott scaling for the kinetic energy density in the low-Tcconventional superconductorsLi2Pd3Band Nb

The scaling approach recently proposed by Landau and Ott for isothermal magnetization curves is extended to the average kinetic energy density of the condensate. Two low $T_c$ superconductors, Nb and $Li_{2}Pd_{3}B$ are studied and their isothermal reversible magnetization shown to display Landau and Ott scaling. Good agreement is obtained for the upper critical field $H_{c2}(T)$, determined from the Abrikosov approximation for the reversible region (standard linear extrapolation of the magnetization curve), and from the maximum of the kinetic energy curves. For the full range of data, which includes the irreversible region, the isothermal $d.M.B/H^2$ curves for $Li_2Pd_3B$ show an impressive collapse into a single curve over the entire range of field measurements. The Nb isothermal $d.M.B/H^2$ curves exhibit the interesting feature of a constant and temperature independent minimum value.

Electronic excitation in impact scattering of low-energy He+ from solid surfaces.

Inelastic scattering and electron-exchange processes in low-energy (0.1--1 keV) ${\mathrm{He}}^{+}$ scattering from surfaces of ionic compounds and metallic elements have been investigated. The probability for ionization of neutral ${\mathrm{He}}^{0}$ in the ground state is minimized for target elements which have filled d orbitals located in a shallower energy position than the He 1s level. Inelastic scattering other than reionization of ${\mathrm{He}}^{0}$ is also clearly observed in the spectra from a large number of ionic compounds. These excitations are observed provided that the surface p levels are located at lower energies than the He 1s level and that ionization of ${\mathrm{He}}^{0}$ takes place with a large probability. On the basis of the quasimolecular framework, it is found that the inelastic scattering is caused by excitation of surface p electrons along the \ensuremath{\sigma} orbital, which is promoted due to the antibonding interaction with the He 1s orbital. The quantum-mechanical interference between bonding and antibonding orbitals, which results in oscillatory-yield--versus--kinetic-energy curves because of the quasiresonant charge exchange, is found to be broken down by the intervening occurrence of the inelastic process.

Mechanical energy of walking of stroke patients

The mechanical energy costs of walking have been studied in ten stroke patients with hemiplegia. A two-dimensional sagittal plane cinematographic analysis of two strides of the subjects' normal walking was undertaken, yielding continuous information about the mechanical energy costs of the whole body and each of its parts, about the energy types involved, and the amounts of energy conservation. The large head, arms, and trunk (HAT) were found to dominate the total pattern. Three major disturbances were seen. In contrast to normal subjects who show energy-conserving negatively correlated potential and kinetic energy curves for the HAT, the subjects who demonstrated the first disturbance showed gross irregularity of the curves, with almost no opportunity for exchange between energy types. In a second disturbance the curves of the HAT showed some energy-conserving portions, but levels of kinetic energy curves were low, resulting in little energy exchange. In the third disturbance, some exchange was evident, but the pattern was dominated by potential energy changes in the form of a single large rise and fall, coinciding with swing phase of the affected leg. Each of these disturbances would require a different approach to treatment. Although mechanical energy analyses do not reflect certain energy costs, such as the effort required to hold the body up against the pull of gravity and that used in contracting antagonist muscles, they could be of considerable assistance in pinpointing costly variations in energy patterns during walking and in determining appropriate treatment procedures.

Cooperative magnetism in metallic jellium and in the insulating Wigner electron crystal

Total energies for the paramagnetic (P) and ferromagnetic (F) metallic phases of jellium are calculated using interpolation formulae adjusted to the results of computer simulation studies. For the Wigner insulator (W), the total energy given by an early theoretical model is found to agree closely with recent computer simulation results. Using these total energies, the phase transitions from P to F and from F to W are estimated to take place at r s = 79 ± and 84 ± 4, respectively, in units of the Bohr radius. Although consistent with earlier estimates based directly on the computer simulations at a limited number of r s values, the present estimates are more precise. Since the P to F and F to W transitions come so close together on an r s scale, the F phase may just barely emerge as the lowest energy phase or may not so emerge at all. Using the virial theorem, kinetic energy curves are constructed and kinetic energy discontinuities at the first-order phase transitions are thereby estimated. The momentum distributions for various phases of jellium are also discussed in terms of simple models. Finally, the phase boundary between antiferromagnetic and paramagnetic states of the Wigner crystal for T ≠ 0 is briefly considered. It is shown that one is dealing with antiferromagnetism in the millidegree Kelvin range.

Energetics of fission of Th 232 induced by 27.8 MeV helium ions

>A back-to-back solid state detector system was used to study the energetics of 27.8-Mev helium ion-induced fission of Th/sup 232/, an ion beam of 0.05 mu a in intensity being used from the I.N.S. cyclotron. A symmetric peak observed in the kinetic energy contour diagram is reported. The mass yield and the average total kinetic energy curves, derived from the contour diagram, are presented. (L.B.S.)