Artículos de revistas sobre el tema "Drive and dissipation"
Siga este enlace para ver otros tipos de publicaciones sobre el tema: Drive and dissipation.
Crea una cita precisa en los estilos APA, MLA, Chicago, Harvard y otros
Consulte los 50 mejores artículos de revistas para su investigación sobre el tema "Drive and dissipation".
Junto a cada fuente en la lista de referencias hay un botón "Agregar a la bibliografía". Pulsa este botón, y generaremos automáticamente la referencia bibliográfica para la obra elegida en el estilo de cita que necesites: APA, MLA, Harvard, Vancouver, Chicago, etc.
También puede descargar el texto completo de la publicación académica en formato pdf y leer en línea su resumen siempre que esté disponible en los metadatos.
Explore artículos de revistas sobre una amplia variedad de disciplinas y organice su bibliografía correctamente.
1
Ikeda, Tatsuhiko N. y Masahiro Sato. "General description for nonequilibrium steady states in periodically driven dissipative quantum systems". Science Advances 6, n.º 27 (julio de 2020): eabb4019. http://dx.doi.org/10.1126/sciadv.abb4019.
Resumen
Laser technology has developed and accelerated photo-induced nonequilibrium physics, from both the scientific and engineering viewpoints. Floquet engineering, i.e., controlling material properties and functionalities by time-periodic drives, is at the forefront of quantum physics of light-matter interaction. However, it is limited to ideal dissipationless systems. Extending Floquet engineering to various materials requires understanding of the quantum states emerging in a balance of the periodic drive and energy dissipation. Here, we derive a general description for nonequilibrium steady states (NESSs) in periodically driven dissipative systems by focusing on systems under high-frequency drive and time-independent Lindblad-type dissipation. Our formula correctly describes the time average, fluctuation, and symmetry properties of the NESS, and can be computed efficiently in numerical calculations. This approach will play fundamental roles in Floquet engineering in a broad class of dissipative quantum systems from atoms and molecules to mesoscopic systems, and condensed matter.
2
Kumar, Naveen, Suram Singh y Avinash Chand Yadav. "Energy fluctuations in one dimensional Zhang sandpile model". Journal of Statistical Mechanics: Theory and Experiment 2022, n.º 7 (1 de julio de 2022): 073203. http://dx.doi.org/10.1088/1742-5468/ac7aa8.
Resumen
Abstract We consider the Zhang sandpile model in one-dimension (1D) with locally conservative (or dissipative) dynamics and examine its total energy fluctuations at the external drive time scale. The bulk-driven system leads to Lorentzian spectra, with a cutoff time T growing linearly with the system size L. The fluctuations show 1/f α behavior with α ∼ 1 for the boundary drive, and the cutoff time varies non-linearly. For conservative local dynamics, the cutoff time shows a power-law growth T ∼ L λ that differs from an exponential form ∼exp(μL) observed for the nonconservative case. We suggest that the local dissipation is not a necessary ingredient of the system in 1D to get the 1/f noise, and the cutoff time can reveal the distinct nature of the local dynamics. We also discuss the energy fluctuations for locally nonconservative dynamics with random dissipation.
3
Palochkin, S. V. y P. N. Rudovskiy. "Energy Dissipation in a Drive Chain During Its Transverse Vibrations as a String with Fixed Ends". Proceedings of Higher Educational Institutions. Маchine Building, n.º 06 (723) (junio de 2020): 3–9. http://dx.doi.org/10.18698/0536-1044-2020-6-3-9.
Resumen
Chain transmissions are widespread in drives of machines used for various industrial purposes. In order to study drive dynamics, it is important to know the dissipative characteristics of its components and gears. However, the information on the damping ability of chain transmissions in research and technical literature is limited and fragmented, which makes the topic of this work, dedicated to the study of energy dissipation in transverse vibrations of chain transmission branches, of great current interest. The objective of this work was to study and determine the quantitative characteristics of energy dissipation in a drive chain experiencing the most common form of transverse vibrations as a string with fixed ends, which is characteristic of transmissions with large masses of sprockets and parts attached to them. To achieve this objective, a mathematical model of the dissipation of vibrational energy was developed using a method of estimating energy losses due to friction when parts of the chain’s hinge joint slip in a compressed contact. Engineering formulas for calculating energy dissipation per cycle of vibrations and absorption coefficient were obtained. The adequacy of the developed model and the obtained calculation formulas was confirmed by the results of the experimental determination of the absorption coefficients of the chain using the method of free damped vibrations. The results of the study allow us to conclude that chain transmissions have an increased damping capacity, and to determine the influence of transmission parameters and the oscillatory process on it.
4
Chyba, Christopher F. y Kevin P. Hand. "Internal-current Lorentz-force Heating of Astrophysical Objects". Astrophysical Journal Letters 922, n.º 2 (1 de diciembre de 2021): L38. http://dx.doi.org/10.3847/2041-8213/ac399d.
Resumen
Abstract Two forms of ohmic heating of astrophysical secondaries have received particular attention: unipolar-generator heating with currents running between the primary and secondary, and magnetic induction heating due to the primary’s time-varying field. Neither appears to cause significant dissipation in the contemporary solar system. But these discussions have overlooked heating derived from the spatial variation of the primary’s field across the interior of the secondary. This leads to Lorentz-force-driven currents around paths entirely internal to the secondary, with resulting ohmic heating. We examine three ways to drive such currents, by the cross product of (1) the secondary’s azimuthal orbital velocity with the nonaxially symmetric field of the primary, (2) the radial velocity (due to nonzero eccentricity) of the secondary with the primary’s field, or (3) the out-of-plane velocity (due to nonzero inclination) with the primary’s field. The first of these operates even for a spin-locked secondary whose orbit has zero eccentricity, in strong contrast to tidal dissipation. We show that Jupiter’s moon Io today could dissipate about 600 GW (more than likely current radiogenic heating) in the outer 100 m of its metallic core by this mechanism. Had Io ever been at 3 Jovian radii instead of its current 5.9, it could have been dissipating 15,000 GW. Ohmic dissipation provides a mechanism that could operate in any solar system to drive inward migration of secondaries that then necessarily comes to a halt upon reaching a sufficiently close distance to the primary.
5
Gadomski, Adam. "Soft-Material Dissipative Formation by a Kramers-Type Picture". Research Letters in Materials Science 2007 (2007): 1–4. http://dx.doi.org/10.1155/2007/71642.
Resumen
We consider a model soft-material formation in dimensiond(a degree of freedom) undergoing an entropic drive, deeply rooted in first law of thermodynamics as well as in entropy production, namely, dissipation rate. It turns out that for such entropy-driven (dissipative) process, two strategies of making the formation orderly can be seen. In low-temperature limit, one may promote curvature-controlled, surface-tension involving scenario, usually characteristic of polycrystals and bubbles. In high-temperature limit, there can be a chance for creating order by establishing viscoelastic phase separation, promoting some microstress field's microrheological action that somehow renormalizes the system toward ordering. The latter, in turn, is very characteristic of protein and/or colloid network formations. This altogether implies that a disordering thermodynamic factor, such as the entropy can typically be, is able to effectively promote ordering by respective energy dissipation, in particular for soft-matter rearrangements and clusterings with weak interactions among the basic material's units, namely, “soft” grains.
6
GUPTA, ROHINI, JOHN WILLIS y LAWRENCE T. PILEGGI. "LOW POWER DESIGN OF OFF-CHIP DRIVERS AND TRANSMISSION LINES: A BRANCH AND BOUND APPROACH". International Journal of High Speed Electronics and Systems 07, n.º 02 (junio de 1996): 249–67. http://dx.doi.org/10.1142/s0129156496000104.
Resumen
As electronic systems grow in functional complexity, hence size, the design is often forced into a multi-chip solution. For such systems, the power dissipation due to the off-chip drivers (OCDs) and the off-chip interconnect capacitance can contribute to a significant portion of the overall system power. Often, however, this excessive power dissipation is unwarranted, since a smaller OCD can be used to drive the transmission line load, hence reducing the net capacitance being switched. The objective of this paper is to enable power dissipation trade-off decisions during the high-level phases of design and to minimize the power dissipation of OCDs and their associated interconnect. First, a termination metric is described that uses width optimization of RLC interconnects. Then, in terms of a proposed linear driver model, the low power design objective is posed as an integer programming problem and a branch and bound enumeration algorithm is presented. The driver and interconnect sizes are determined which will preserve signal quality, dispense with additional termination components, meet delay requirements, and minimize the overall power dissipation.
7
Chaudhari, Abhijit P., Shane P. Kelly, Riccardo J. Valencia-Tortora y Jamir Marino. "Zeno crossovers in the entanglement speed of spin chains with noisy impurities". Journal of Statistical Mechanics: Theory and Experiment 2022, n.º 10 (1 de octubre de 2022): 103101. http://dx.doi.org/10.1088/1742-5468/ac8e5d.
Resumen
Abstract We use a noisy signal with finite correlation time to drive a spin (dissipative impurity) in the quantum XY spin chain and calculate the dynamics of entanglement entropy (EE) of a bipartition of spins, for a stochastic quantum trajectory. We compute the noise averaged EE of a bipartition of spins and observe that its speed of spreading decreases at strong dissipation, as a result of the Zeno effect. We recover the Zeno crossover and show that noise averaged EE can be used as a proxy for the heating and Zeno regimes. Upon increasing the correlation time of the noise, the location of the Zeno crossover shifts at stronger dissipation, extending the heating regime.
8
Teixeira, W. S., F. L. Semião, J. Tuorila y M. Möttönen. "Assessment of weak-coupling approximations on a driven two-level system under dissipation". New Journal of Physics 24, n.º 1 (31 de diciembre de 2021): 013005. http://dx.doi.org/10.1088/1367-2630/ac43ee.
Resumen
Abstract The standard weak-coupling approximations associated to open quantum systems have been extensively used in the description of a two-level quantum system, qubit, subjected to relatively weak dissipation compared with the qubit frequency. However, recent progress in the experimental implementations of controlled quantum systems with increased levels of on-demand engineered dissipation has motivated precision studies in parameter regimes that question the validity of the approximations, especially in the presence of time-dependent drive fields. In this paper, we address the precision of weak-coupling approximations by studying a driven qubit through the numerically exact and non-perturbative method known as the stochastic Liouville–von Neumann equation with dissipation. By considering weak drive fields and a cold Ohmic environment with a high cutoff frequency, we use the Markovian Lindblad master equation as a point of comparison for the SLED method and study the influence of the bath-induced energy shift on the qubit dynamics. We also propose a metric that may be used in experiments to map the regime of validity of the Lindblad equation in predicting the steady state of the driven qubit. In addition, we study signatures of the well-known Mollow triplet and observe its meltdown owing to dissipation in an experimentally feasible parameter regime of circuit electrodynamics. Besides shedding light on the practical limitations of the Lindblad equation, we expect our results to inspire future experimental research on engineered open quantum systems, the accurate modeling of which may benefit from non-perturbative methods.
9
Wang, Yong Cong, You Kun Zhang y Yan Hui Lu. "Heat Analysis of Vehicle Drive Axle". Applied Mechanics and Materials 851 (agosto de 2016): 299–303. http://dx.doi.org/10.4028/www.scientific.net/amm.851.299.
Resumen
The vehicle drive axle is one of the main sources of power loss in drivetrain system, and its improvements can have a significant impact on vehicle fuel economy. Gears churning loss, bearing friction loss and engaging friction loss all make a great contribution to the heat generation. The temperatures of lubricants, the gear tooth contacting surfaces, and the bearing surfaces are critical to the overall axle performance in terms of power losses, fatigue life, and wear. So it is important to understand the heat generation and dissipation in automotive drive axle. However, the quantities of understandings of drive axle temperature is limited and published information is deficient.In this paper, we establish the mathematical model of heat generation and dissipation to investigate the connection between thermal behavior and power loss. Power loss is consist of churning loss, bearing friction loss and engaging friction loss. And also we simulate the model to get the conclusion and then conduct the experiments to verify the correctness of the theories and models.
10
Palochkin, S. V., M. A. Karnaukhov, M. A. Lyubchenko y P. N. Rudovskiy. "Energy dissipation in the variable stiffness couplings with a serpentine spring at the torsional vibrations". Proceedings of Higher Educational Institutions. Маchine Building, n.º 6 (759) (junio de 2023): 3–11. http://dx.doi.org/10.18698/0536-1044-2023-6-3-11.
Resumen
The paper presents results of the theoretical research of the structural vibration damping in the variable stiffness couplings with a serpentine spring, which are rather widely used in the drives of the heavy engineering and machine tool products exposed to the vibration loads. When performing dynamic calculations of the drives of such machines, it is necessary to know the dissipative characteristics of their components and parts, including the indicated couplings. The paper considers the case of torsional harmonic vibrations characteristic for the coupling drive with a serpentine spring associated with twisting of the shafts connected by this coupling due to the attached parts imbalance. Quantitative characteristics of the torsional vibration energy dissipation in the couplings under consideration were studied and determined using the well-known method for estimating the vibration energy losses due to friction during slipping in the compressed parts’ contact. Mathematical model of the torsional vibration damping in a coupling was developed, which makes it possible to determine its quantitative characteristics in the form of vibration energy dissipation per cycle and the absorption coefficient depending on the coupling design parameters and the vibration process. The proposed model is implemented as an interactive application program in the MATLAB computer environment.
11
Bhattacharyya, R. y M. S. Janaki. "Two-fluid stationary states with dissipation and external drive". Physics of Plasmas 13, n.º 4 (abril de 2006): 044508. http://dx.doi.org/10.1063/1.2196367.
12
Mirzazadeh, Ramin y Stefano Mariani. "Estimation of Air Damping in Out-of-Plane Comb-Drive Actuators". Micromachines 10, n.º 4 (19 de abril de 2019): 263. http://dx.doi.org/10.3390/mi10040263.
Resumen
The development of new compliant resonant microsystems and the trend towards further miniaturization have recently raised the issue of the accuracy and reliability of computational tools for the estimation of fluid damping. Focusing on electrostatically actuated torsional micro-mirrors, a major dissipation contribution is linked to the constrained flow of air at comb fingers. In the case of large tilting angles of the mirror plate, within a period of oscillation the geometry of the air domain at comb-drives gets largely distorted, and the dissipation mechanism is thereby affected. In this communication, we provide an appraisal of simple analytical solutions to estimate the dissipation in the ideal case of air flow between infinite plates, at atmospheric pressure. The results of numerical simulations are also reported to assess the effect on damping of the finite size of actual geometries.
13
Emanuel, Kerry y Raphaël Rousseau-Rizzi. "Reply to “Comments on ‘An Evaluation of Hurricane Superintensity in Axisymmetric Numerical Models’”". Journal of the Atmospheric Sciences 77, n.º 11 (noviembre de 2020): 3977–80. http://dx.doi.org/10.1175/jas-d-20-0199.1.
Resumen
AbstractWe concur with Makarieva et al. that in our earlier work on the hurricane differential Carnot cycle, we neglected the work done in lifting water and the dissipation of kinetic energy in the outflow (we explicitly acknowledged neglecting these terms). Here, we relax those assumptions, affirm the conclusion of Makarieva et al. that the water lifting term is small, and show that the effect of outflow dissipation is negligible. We remind readers that the differential Carnot theory is not a closed theory for potential intensity as it does not specify the outflow temperature or the boundary layer moist enthalpy at the radius of maximum winds. The addition of enthalpy to the inflow can raise the boundary layer enthalpy, reducing subsequent surface fluxes, regardless of whether that addition comes from surface fluxes themselves or from dissipative heating. We show that while this may indeed reduce the effect of dissipative heating, it does not eliminate it. We disagree with Makarieva et al.’s assertions that dissipative heating does not increase potential intensity and that only latent heat fluxes can drive tropical cyclones when dissipative heating is included.
14
Alfaro, Diego A. y Michael C. Coniglio. "Discrimination of Mature and Dissipating Severe-Wind-Producing MCSs with Layer-Lifting Indices". Weather and Forecasting 33, n.º 1 (28 de diciembre de 2017): 3–21. http://dx.doi.org/10.1175/waf-d-17-0088.1.
Resumen
Abstract The environmental factors that drive the dissipation of linear severe-wind-producing mesoscale convective systems (MCSs) are investigated. Layer-lifting indices are emphasized, which measure convective instability in forward-propagating MCSs by considering that deep convective latent heating depends on 1) the potential latent heating within the atmospheric column, measured by the integrated CAPE (ICAPE), and 2) the dilution of buoyancy due to midtropospheric inflow, measured by the inflow fraction (IF) of convectively unstable air to total system-relative inflow. These elements are integrated to define the layer-lifting CAPE (CAPEll), which depends on environmental thermodynamics, kinematics, and the MCS’s movement vector. Radar reflectivity plots are used to subjectively identify and classify MCSs in terms of their stage (mature or dissipating) and degree of organization (highly or weakly organized). Nonparametric statistical inferences are performed on several metrics computed at maturity and dissipation from RUC/RAP analysis data, aiming to identify the most skillful indices for diagnosing three different aspects of MCS dissipation: 1) the transition from maturity to dissipation, 2) the stage of an MCS, and 3) the disorganization that characterizes the dissipating stage. In terms of MCS dissipation CAPEll is the best diagnostic. A close approximation to CAPEll is accomplished by estimating an MCS’s movement with Corfidi vectors, providing a potentially useful index in operational settings. ICAPE is the most skillful thermodynamic metric, while IF is the best kinematic discriminator of MCS stage and stage transition, suggesting the fundamental importance of layer-lifting convective instability for MCS maintenance. Layer-lifting indices are not particularly skillful at distinguishing the degree of MCS organization at maturity, which is best diagnosed by deep vertical wind shear.
15
Zhang, Cong Peng, Mei Bo Li y Xue Ke Luo. "Thermal Characteristics Analysis of Aerostatic Direct Drive Rotary Stage". Advanced Materials Research 655-657 (enero de 2013): 287–91. http://dx.doi.org/10.4028/www.scientific.net/amr.655-657.287.
Resumen
A precision air bearing rotary stage driven by direct-driven motor is proposed. The structural characteristic of the rotary system is introduced, and the mechanism of structural thermal deformation and heat dissipation of aerostatic direct drive rotary stage were analyzed. The simulation models of static and transient temperature field are built, and thermal-structure coupled filed is calculated. The internal steady thermal field diagram and key nodes temperature curve of the rotary stage are obtained. Based on the temperature analysis results, the rotary stage structural deformation is established. The cooling method is provided, and result shows that the cooling way is effective.
16
Mylnikov, Valentin Yu, Sergey O. Potashin, Grigorii S. Sokolovskii y Nikita S. Averkiev. "Dissipative Phase Transition in Systems with Two-Photon Drive and Nonlinear Dissipation near the Critical Point". Nanomaterials 12, n.º 15 (24 de julio de 2022): 2543. http://dx.doi.org/10.3390/nano12152543.
Resumen
In this paper, we examine dissipative phase transition (DPT) near the critical point for a system with two-photon driving and nonlinear dissipations. The proposed mean-field theory, which explicitly takes into account quantum fluctuations, allowed us to describe properly the evolutionary dynamics of the system and to demonstrate new effects in its steady-state. We show that the presence of quantum fluctuations leads to a power-law dependence of the anomalous average at the phase transition point, with which the critical exponent is associated. Also, we investigate the effect of the quantum fluctuations on the critical point renormalization and demonstrate the existence of a two-photon pump “threshold”. It is noteworthy that the obtained results are in a good agreement with the numerical simulations.
17
Karthikeyan, A. y P. S. Mallick. "Body-Biased Subthreshold Bootstrapped CMOS Driver". Journal of Circuits, Systems and Computers 28, n.º 03 (24 de febrero de 2019): 1950051. http://dx.doi.org/10.1142/s0218126619500518.
Resumen
This paper proposes a body-biased bootstrapped CMOS driver for subthreshold applications. The proposed driver has been implemented with the same number of transistors as conventional bootstrapped CMOS driver. The performance of the subthreshold bootstrapped CMOS driver has been compared with the conventional bootstrapped CMOS driver. Our results show that the proposed body-biased subthreshold bootstrapped CMOS driver has 37% reduction in delay and 39% reduction in power dissipation compared to conventional bootstrapped CMOS driver. The proposed driver is more suitable to drive large loads compared to the conventional driver and operates better at subthreshold region.
18
Auclair-Desrotour, P., S. Mathis y C. Le Poncin-Lafitte. "Tidal interactions in rotating multiple stars and their impact on their evolution". Proceedings of the International Astronomical Union 9, S307 (junio de 2014): 208–10. http://dx.doi.org/10.1017/s1743921314006735.
Resumen
AbstractTidal dissipation in stars is one of the key physical mechanisms that drive the evolution of binary and multiple stars. As in the Earth oceans, it corresponds to the resonant excitation of their eigenmodes of oscillation and their damping. Therefore, it strongly depends on the internal structure, rotation, and dissipative mechanisms in each component. In this work, we present a local analytical modeling of tidal gravito-inertial waves excited in stellar convective and radiative regions respectively. This model allows us to understand in details the properties of the resonant tidal dissipation as a function of the excitation frequencies, the rotation, the stratification, and the viscous and thermal properties of the studied fluid regions. Then, the frequencies, height, width at half-height, and number of resonances as well as the non-resonant equilibrium tide are derived analytically in asymptotic regimes that are relevant in stellar interiors. Finally, we demonstrate how viscous dissipation of tidal waves leads to a strongly erratic orbital evolution in the case of a coplanar binary system. We characterize such a non-regular dynamics as a function of the height and width of resonances, which have been previously characterized thanks to our local fluid model.
19
de Lavergne, Casimir, Gurvan Madec, Julien Le Sommer, A. J. George Nurser y Alberto C. Naveira Garabato. "On the Consumption of Antarctic Bottom Water in the Abyssal Ocean". Journal of Physical Oceanography 46, n.º 2 (febrero de 2016): 635–61. http://dx.doi.org/10.1175/jpo-d-14-0201.1.
Resumen
AbstractThe abyssal ocean is primarily filled by cold, dense waters formed around Antarctica and collectively referred to as Antarctic Bottom Water (AABW). At steady state, AABW must be consumed in the ocean interior at the same rate it is produced, but how and where this consumption is achieved remains poorly understood. Here, estimates of abyssal water mass transformation by geothermal heating and parameterized internal wave–driven mixing are presented. This study uses maps of the energy input to internal waves by tidal and geostrophic motions interacting with topography combined with assumptions about the distribution of energy dissipation to evaluate dianeutral transports induced by breaking internal tides and lee waves. Geothermal transformation is assessed based on a map of geothermal heat fluxes. Under the hypotheses underlying the constructed climatologies of buoyancy fluxes, the authors calculate that locally dissipating internal tides and geothermal heating contribute, respectively, about 8 and 5 Sverdrups (Sv; 1 Sv ≡ 106 m3 s−1) of AABW consumption (upwelling), mostly north of 30°S. In contrast, parameterized lee wave–driven mixing causes significant transformation only in the Southern Ocean, where it forms about 3 Sv of AABW, decreasing the mean density but enhancing the northward flow of abyssal waters. The possible role of remotely dissipating internal tides in complementing AABW consumption is explored based on idealized distributions of mixing energy. Depending mostly on the chosen vertical structure, such mixing could drive 1 to 28 Sv of additional AABW upwelling, highlighting the need to better constrain the spatial distribution of remote dissipation. Though they carry large uncertainties, these climatological transformation estimates shed light on the qualitative functioning and key unknowns of the diabatic overturning.
20
Sang, Longlong, Quanming Lu, Jinlin Xie, Feibin Fan, Qiaofeng Zhang, Weixing Ding, Jian Zheng y Xuan Sun. "Energy dissipation during magnetic reconnection in the Keda linear magnetized plasma device". Physics of Plasmas 29, n.º 10 (octubre de 2022): 102108. http://dx.doi.org/10.1063/5.0090790.
Resumen
This paper investigates energy dissipation during electron-scale magnetic reconnection with laboratory experiments. Magnetic fields with opposite directions are generated by two parallel identical pulsed currents in our Keda linear magnetized plasma device. Magnetic reconnection is realized in the rising phase of the pulsed currents. The ramp-up rate of the pulsed current is found to be proportional to the inflow speed, providing a method to modify the reconnection drive. The incoming magnetic energy and its dissipation into plasma energy have been estimated in the vicinity of the X line. It is found that the plasma energy converted from the incoming electromagnetic energy increases with the increasing reconnection drive, while the conversion ratio remains almost unchanged, which is about 10%.
21
Zhang, Bowen, Zaixin Song, Senyi Liu, Rundong Huang y Chunhua Liu. "Overview of Integrated Electric Motor Drives: Opportunities and Challenges". Energies 15, n.º 21 (7 de noviembre de 2022): 8299. http://dx.doi.org/10.3390/en15218299.
Resumen
Integrated Motor Drives (IMDs) have recently received extensive attention. In electric vehicles (EVs), electric propulsion aircraft, and ship propulsion systems, integrated motors have the great potential to replace traditional motors with the distinct merits of compact size, high power density, high efficiency, and high-cost effectiveness. This paper investigates and reviews integrated motor drives’ development and critical technologies. It not only reveals the research progress of the motor structure, converter, volume optimization, heat dissipation design, and weakening electromagnetic interference of integrated motor drives but also explores in detail the applications of wide-bandgap semiconductors and the integration of LCL filters. In addition, this paper also puts forward the concept of integrated motor drive integration level and establishes a corresponding quantitative method to evaluate IMDs integration level. In the future, integrated wireless motor drives will have a broad scope of research and application. IMDs systems will play an important role in applications requiring high power density, providing solutions to motor system size and heat dissipation problems. This overview will help clarify the opportunities, challenges, and future development of IMDs.
22
Kowal, Michał. "Sensorless compensation system for thermal deformations of ball screws in machine tools drives". Archives of Mechanical Technology and Materials 36, n.º 1 (1 de diciembre de 2016): 1–6. http://dx.doi.org/10.1515/amtm-2016-0001.
Resumen
Abstract The article presents constructional, technological and operational issues associated with the compensation of thermal deformations of ball screw drives. Further, it demonstrates the analysis of a new sensorless compensation method relying on coordinated computation of data fed directly from the drive and the control system in combination with the information pertaining to the operational history of the servo drive, retrieved with the use of an artificial neural networks (ANN)-based learning system. Preliminary ANN-based models, developed to simulate energy dissipation resulting from the friction in the screw-cap assembly and convection of heat are expounded upon, as are the processes of data selection and ANN learning. In conclusion, the article presents the results of simulation studies and preliminary experimental evidence confirming the applicability of the proposed method, efficiently compensating for the thermal elongation of the ball screw in machine tool drives.
23
Uddin, Mohammad Nasir, Zhuoqun Zhai y Ifte Khairul Amin. "Port Controlled Hamilton With Dissipation-Based Speed Control of IPMSM Drive". IEEE Transactions on Power Electronics 35, n.º 2 (febrero de 2020): 1742–52. http://dx.doi.org/10.1109/tpel.2019.2918679.
24
Brunelli, Matteo y Oussama Houhou. "Dissipative Synthesis of Mechanical Fock-Like States". Proceedings 12, n.º 1 (19 de julio de 2019): 25. http://dx.doi.org/10.3390/proceedings2019012025.
Resumen
The observation of genuine quantum features of nano-mechanical motion is a key goal for both fundamental and applied quantum science. To this end, a promising approach is the stabilization of nonclassical features in the presence of dissipation, by means of the tunable coupling with a photonic environment. Here we present a scheme that combines dissipative squeezing with a mechanical nonlinearity to stabilize arbitrary approximations of (displaced) mechanical Fock state of any number. We consider an optomechanical system driven by three control lasers---at the cavity resonance and at the two mechanical sidebands---that couple the amplitude of the cavity field to the resonator's position and position squared. When the amplitude of the resonant drive is tuned to some specific values, the mechanical steady state is found in a (displaced) superposition of a finite number of Fock states, which for large enough squeezing achieves near-unit fidelity with a (displaced) Fock state of any desired number.
25
Ramsay, E., James Breeze, David T. Clark, A. Murphy, D. Smith, R. Thompson, Sean Wright, R. Young y A. Horsfall. "High Temperature CMOS Circuits on Silicon Carbide". Materials Science Forum 821-823 (junio de 2015): 859–62. http://dx.doi.org/10.4028/www.scientific.net/msf.821-823.859.
Resumen
This paper presents the characteristics and performance of a range of Silicon Carbide (SiC) CMOS integrated circuits fabricated using a process designed to operate at temperatures of 300°C and above. The properties of Silicon carbide enable both n-channel and p-channel MOSFETS to operate at temperatures above 400°C [1] and we are developing a CMOS process to exploit this capability [4]. The operation of these transistors and other integrated circuit elements such as resistors and contacts is presented across a temperature range of room temperature to +400°C. We have designed and fabricated a wide range of test and demonstrator circuits. A set of six simple logic parts, such as a quad NAND and NOR gates, have been stressed at 300°C for extended times and performance results such as propagation delay drive levels, threshold levels and current consumption versus stress time are presented. Other circuit implementations, with increased logic complexity, such as a pulse width modulator, a configurable timer and others have also been designed, fabricated and tested. The low leakage characteristics of SiC has allowed the implementation of a very low leakage analogue multiplexer showing less than 0.5uA channel leakage at 400°C. Another circuit implemented in SiC CMOS demonstrates the ability to drive SiC power switching devices. The ability of CMOS to provide an active pull up and active pull down current can provide the charging and discharging current required to drive a power MOSFET switch in less than 100ns. Being implemented in CMOS, the gate drive buffer benefits from having no direct current path from the power rails, except during switching events. This lowers the driver power dissipation. By including multiple current paths through independently switched transistors, the gate drive buffer circuit can provide a high switching current and then a lower sustaining current as required to minimize power dissipation when driving a bipolar switch.
26
Howson, Thomas. "How Transverse Waves Drive Turbulence in the Solar Corona". Symmetry 14, n.º 2 (15 de febrero de 2022): 384. http://dx.doi.org/10.3390/sym14020384.
Resumen
Oscillatory power is pervasive throughout the solar corona, and magnetohydrodynamic (MHD) waves may carry a significant energy flux throughout the Sun’s atmosphere. As a result, over much of the past century, these waves have attracted great interest in the context of the coronal heating problem. They are a potential source of the energy required to maintain the high-temperature plasma and may accelerate the fast solar wind. Despite many observations of coronal waves, large uncertainties inhibit reliable estimates of their exact energy flux, and as such, it remains unclear whether they can contribute significantly to the coronal energy budget. A related issue concerns whether the wave energy can be dissipated over sufficiently short time scales to balance the atmospheric losses. For typical coronal parameters, energy dissipation rates are very low and, thus, any heating model must efficiently generate very small-length scales. As such, MHD turbulence is a promising plasma phenomenon for dissipating large quantities of energy quickly and over a large volume. In recent years, with advances in computational and observational power, much research has highlighted how MHD waves can drive complex turbulent behaviour in the solar corona. In this review, we present recent results that illuminate the energetics of these oscillatory processes and discuss how transverse waves may cause instability and turbulence in the Sun’s atmosphere.
27
Wu, Xiangfan, Yangyang Guo, Zuzhi Tian, Fangwei Xie, Jinjie Ji y Haopeng Li. "Analysis on Flow and Temperature Field of High-Power Magnetorheological Fluid Transmission Device". Applied Sciences 12, n.º 10 (17 de mayo de 2022): 5044. http://dx.doi.org/10.3390/app12105044.
Resumen
Aiming to solve the problem of high-power magnetorheological fluid transmission heat dissipation, a new type of magnetorheological fluid drive disk is designed. The characteristics of the flow field and temperature field of high power MR fluid transmission devices are analyzed. Meanwhile, the influence of factors, such as rotating speed, inlet velocity, inlet position, diameter and number of magnetic columns, on the flow field are also investigated. Furthermore, the distribution characteristics of the ultimate slip power and the transient temperature field are obtained. The experimental platform of an MR fluid transmission device was established, and the torque transfer performance and heat dissipation performance were tested. The experimental results show that the device has good heat dissipation performance and can transfer high-power torque.
28
Xu, Zhaoxiang, Yazhen Wang y Haifeng Wang. "Calculation and Analysis of Deformation Characteristic and Energy Dissipation of Flexible Bearings in Harmonic Drive for Industrial Robots". Journal of Physics: Conference Series 2365, n.º 1 (1 de noviembre de 2022): 012032. http://dx.doi.org/10.1088/1742-6596/2365/1/012032.
Resumen
Abstract The flexible bearing is a key component of harmonic gear reducer for industrial robots. The wave generator cam as assembly part will significantly affect the flexible bearing transmission state. This paper derives the flexible bearing deformation coordination equation formula based on the harmonic drive theories, and the deformation characteristics of the flexible bearing formed by different wave generator cam shapes were studied. Combined the theory of clabellon with the load and deformation which are obtained, the deformation energy dissipation of the outer ring of the flexible bearing is discussed and quantitatively evaluated. The results showed that the wave generator cam shapes have a greater effect on the carrying capacity of the flexible bearing, and the dissipation of deformation energy of the flexible bearing can be effectively reduced by selecting appropriate wall thickness of the outer ring. Moreover, it was found that the two-roller wave generator deformation energy dissipation is the least at the same constraint.
29
Long, Christopher A., Alan B. Turner, Guven Kais, Kok M. Tham y John A. Verdicchio. "Measurement and CFD Prediction of the Flow Within an HP Compressor Drive Cone". Journal of Turbomachinery 125, n.º 1 (1 de enero de 2003): 165–72. http://dx.doi.org/10.1115/1.1516195.
Resumen
In some gas turbine aeroengines, the HP compressor is driven by the H.P. turbine through a conical shaft or drive cone. This drive cone is enclosed by a stationary surface that forms the supporting material for the combustion chambers. Air used to cool the turbine blades is directed into the space around the drive cone, and a major concern to an engine designer is the temperature rise in this air due to frictional dissipation and heat transfer. This paper presents results from a combined experimental and CFD investigation into the flow within an engine representative HP compressor drive cone cavity. The experimental results show similarities in flow structure to that found in classic rotor-stator systems. Both 2-D and 3-D CFD simulations were carried out using the FLUENT/UNS code. The 3-D model which included the actual compressor blade tip clearance gave the best agreement with the experimental data. However, the computational resource required to run the 3-D model limits its practical use. The 2-D CFD model, however, was found to give good agreement with experiment, providing care was exercised in selecting an appropriate value of initial tangential velocity.
30
de Lavergne, Casimir, Gurvan Madec, Julien Le Sommer, A. J. George Nurser y Alberto C. Naveira Garabato. "The Impact of a Variable Mixing Efficiency on the Abyssal Overturning". Journal of Physical Oceanography 46, n.º 2 (febrero de 2016): 663–81. http://dx.doi.org/10.1175/jpo-d-14-0259.1.
Resumen
AbstractIn studies of ocean mixing, it is generally assumed that small-scale turbulent overturns lose 15%–20% of their energy in eroding the background stratification. Accumulating evidence that this energy fraction, or mixing efficiency Rf, significantly varies depending on flow properties challenges this assumption, however. Here, the authors examine the implications of a varying mixing efficiency for ocean energetics and deep-water mass transformation. Combining current parameterizations of internal wave-driven mixing with a recent model expressing Rf as a function of a turbulence intensity parameter Reb = εν/νN2, the ratio of dissipation εν to stratification N2 and molecular viscosity ν, it is shown that accounting for reduced mixing efficiencies in regions of weak stratification or energetic turbulence (high Reb) strongly limits the ability of breaking internal waves to supply oceanic potential energy and drive abyssal upwelling. Moving from a fixed Rf = 1/6 to a variable efficiency Rf(Reb) causes Antarctic Bottom Water upwelling induced by locally dissipating internal tides and lee waves to fall from 9 to 4 Sverdrups (Sv; 1 Sv ≡ 106 m3 s−1) and the corresponding potential energy source to plunge from 97 to 44 GW. When adding the contribution of remotely dissipating internal tides under idealized distributions of energy dissipation, the total rate of Antarctic Bottom Water upwelling is reduced by about a factor of 2, reaching 5–15 Sv, compared to 10–33 Sv for a fixed efficiency. The results suggest that distributed mixing, overflow-related boundary processes, and geothermal heating are more effective in consuming abyssal waters than topographically enhanced mixing by breaking internal waves. These calculations also point to the importance of accurately constraining Rf(Reb) and including the effect in ocean models.
31
Scotti, Alberto. "Biases in Thorpe-Scale Estimates of Turbulence Dissipation. Part II: Energetics Arguments and Turbulence Simulations". Journal of Physical Oceanography 45, n.º 10 (octubre de 2015): 2522–43. http://dx.doi.org/10.1175/jpo-d-14-0092.1.
Resumen
AbstractThis paper uses the energetics framework developed by Scotti and White to provide a critical assessment of the widely used Thorpe-scale method, which is used to estimate dissipation and mixing rates in stratified turbulent flows from density measurements along vertical profiles. This study shows that the relevant displacement scale in general is not the rms value of the Thorpe displacement. Rather, the displacement field must be Reynolds decomposed to separate the mean from the turbulent component, and it is the turbulent component that ought to be used to diagnose mixing and dissipation. In general, the energetics of mixing in an overall stably stratified flow involves potentially complex exchanges among the available potential energy and kinetic energy associated with the mean and turbulent components of the flow. The author considers two limiting cases: shear-driven mixing, where mixing comes at the expense of the mean kinetic energy of the flow, and convective-driven mixing, which taps the available potential energy of the mean flow to drive mixing. In shear-driven flows, the rms of the Thorpe displacement, known as the Thorpe scale is shown to be equivalent to the turbulent component of the displacement. In this case, the Thorpe scale approximates the Ozmidov scale, or, which is the same, the Thorpe scale is the appropriate scale to diagnose mixing and dissipation. However, when mixing is driven by the available potential energy of the mean flow (convective-driven mixing), this study shows that the Thorpe scale is (much) larger than the Ozmidov scale. Using the rms of the Thorpe displacement overestimates dissipation and mixing, since the amount of turbulent available potential energy (measured by the turbulent displacement) is only a fraction of the total available potential energy (measured by the Thorpe scale). Corrective measures are discussed that can be used to diagnose mixing from knowledge of the Thorpe displacement. In a companion paper, Mater et al. analyze field data and show that the Thorpe scale can indeed be much larger than the Ozmidov scale.
32
Kaaz, Nicholas, Matthew T. P. Liska, Jonatan Jacquemin-Ide, Zachary L. Andalman, Gibwa Musoke, Alexander Tchekhovskoy y Oliver Porth. "Nozzle Shocks, Disk Tearing, and Streamers Drive Rapid Accretion in 3D GRMHD Simulations of Warped Thin Disks". Astrophysical Journal 955, n.º 1 (1 de septiembre de 2023): 72. http://dx.doi.org/10.3847/1538-4357/ace051.
Resumen
Abstract The angular momentum of gas feeding a black hole (BH) may be misaligned with respect to the BH spin, resulting in a tilted accretion disk. Rotation of the BH drags the surrounding spacetime, manifesting as Lense–Thirring torques that lead to disk precession and warping. We study these processes by simulating a thin (H/r = 0.02), highly tilted ( = 65 ° ) accretion disk around a rapidly rotating (a = 0.9375) BH at extremely high resolutions, which we performed using the general-relativistic magnetohydrodynamic code H-AMR. The disk becomes significantly warped and continuously tears into two individually precessing subdisks. We find that mass accretion rates far exceed the standard α-viscosity expectations. We identify two novel dissipation mechanisms specific to warped disks that are the main drivers of accretion, distinct from the local turbulent stresses that are usually thought to drive accretion. In particular, we identify extreme scale height oscillations that occur twice an orbit throughout our disk. When the scale height compresses, “nozzle” shocks form, dissipating orbital energy and driving accretion. Separate from this phenomenon, there is also extreme dissipation at the location of the tear. This leads to the formation of low-angular momentum “streamers” that rain down onto the inner subdisk, shocking it. The addition of low-angular momentum gas to the inner subdisk causes it to rapidly accrete, even when it is transiently aligned with the BH spin and thus unwarped. These mechanisms, if general, significantly modify the standard accretion paradigm. Additionally, they may drive structural changes on much shorter timescales than expected in α-disks, potentially explaining some of the extreme variability observed in active galactic nuclei.
33
Eastham, Sebastian D. y Daniel J. Jacob. "Limits on the ability of global Eulerian models to resolve intercontinental transport of chemical plumes". Atmospheric Chemistry and Physics 17, n.º 4 (20 de febrero de 2017): 2543–53. http://dx.doi.org/10.5194/acp-17-2543-2017.
Resumen
Abstract. Quasi-horizontal chemical plumes in the free troposphere can preserve their concentrated structure for over a week, enabling transport on intercontinental scales with important environmental impacts. Global Eulerian chemical transport models (CTMs) fail to preserve these plumes due to fast numerical dissipation. We examine the causes of this dissipation and how it can be cured. Goddard Earth Observing System (GEOS-5) meteorological data at 0.25° × 0.3125° horizontal resolution and ∼ 0.5 km vertical resolution in the free troposphere are used to drive a worldwide ensemble of GEOS-Chem CTM plumes at resolutions from 0.25° × 0.3125° to 4° × 5°, in both 2-D (horizontal) and 3-D. Two-dimensional simulations enable examination of the sensitivity of numerical dissipation to grid resolution. We show that plume decay is driven by flow divergence and shear, filamenting the plumes until GEOS-Chem's high-order advection scheme cannot resolve gradients and fast numerical diffusion ensues. This divergence can be measured by the Lyapunov exponent (λ) of the flow. Dissipation of plumes is much faster at extratropical latitudes than in the tropics and this can be explained by stronger divergence. The plume decay constant (α) is linearly related to λ, and increasing grid resolution provides only modest benefits toward plume preservation. Three-dimensional simulations show near-complete dissipation of plumes within a few days, independent of horizontal grid resolution and even in the tropics. This is because vertical grid resolution is inadequate in all cases to properly resolve plume gradients. We suggest that finer vertical grid resolution in the free troposphere is essential for models to resolve intercontinental plumes, while current horizontal resolution in these models (∼ 1°) is sufficient.
34
Seligman, Darryl Z., Adina D. Feinstein, Dong Lai, Luis Welbanks, Aster G. Taylor, Juliette Becker, Fred C. Adams, Marvin Morgan y Jennifer B. Bergner. "Potential Melting of Extrasolar Planets by Tidal Dissipation". Astrophysical Journal 961, n.º 1 (1 de enero de 2024): 22. http://dx.doi.org/10.3847/1538-4357/ad0b82.
Resumen
Abstract Tidal heating on Io due to its finite eccentricity was predicted to drive surface volcanic activity, which was subsequently confirmed by the Voyager spacecraft. Although the volcanic activity in Io is more complex, in theory volcanism can be driven by runaway melting in which the tidal heating increases as the mantle thickness decreases. We show that this runaway melting mechanism is generic for a composite planetary body with liquid core and solid mantle, provided that (i) the mantle rigidity, μ, is comparable to the central pressure, i.e., μ/(ρ gR P) ≳ 0.1 for a body with density ρ, surface gravitational acceleration g, and radius R P; (ii) the surface is not molten; (iii) tides deposit sufficient energy; and (iv) the planet has nonzero eccentricity. We calculate the approximate liquid core radius as a function of μ/(ρ gR P), and find that more than 90% of the core will melt due to this runaway for μ/(ρ gR P) ≳ 1. From all currently confirmed exoplanets, we find that the terrestrial planets in the L 98-59 system are the most promising candidates for sustaining active volcanism. However, uncertainties regarding the quality factors and the details of tidal heating and cooling mechanisms prohibit definitive claims of volcanism on any of these planets. We generate synthetic transmission spectra of these planets assuming Venus-like atmospheric compositions with an additional 5%, 50%, and 98% SO2 component, which is a tracer of volcanic activity. We find a ≳3σ preference for a model with SO2 with 5–10 transits with JWST for L 98-59bcd.
35
Tafoya, Sara, Steven J. Large, Shixin Liu, Carlos Bustamante y David A. Sivak. "Using a system’s equilibrium behavior to reduce its energy dissipation in nonequilibrium processes". Proceedings of the National Academy of Sciences 116, n.º 13 (13 de marzo de 2019): 5920–24. http://dx.doi.org/10.1073/pnas.1817778116.
Resumen
Cells must operate far from equilibrium, utilizing and dissipating energy continuously to maintain their organization and to avoid stasis and death. However, they must also avoid unnecessary waste of energy. Recent studies have revealed that molecular machines are extremely efficient thermodynamically compared with their macroscopic counterparts. However, the principles governing the efficient out-of-equilibrium operation of molecular machines remain a mystery. A theoretical framework has been recently formulated in which a generalized friction coefficient quantifies the energetic efficiency in nonequilibrium processes. Moreover, it posits that, to minimize energy dissipation, external control should drive the system along the reaction coordinate with a speed inversely proportional to the square root of that friction coefficient. Here, we demonstrate the utility of this theory for designing and understanding energetically efficient nonequilibrium processes through the unfolding and folding of single DNA hairpins.
36
Saenko, Oleg A., Xiaoming Zhai, William J. Merryfield y Warren G. Lee. "The Combined Effect of Tidally and Eddy-Driven Diapycnal Mixing on the Large-Scale Ocean Circulation". Journal of Physical Oceanography 42, n.º 4 (1 de abril de 2012): 526–38. http://dx.doi.org/10.1175/jpo-d-11-0122.1.
Resumen
Abstract Several recent studies have shown that ocean western boundaries are the primary regions of eddy energy dissipation. Globally, the eddy energy sinks have been estimated to integrate to about 0.2 TW. This is a sizable fraction of the tidal energy dissipation in the deep oceanic interior, estimated at about 1.0 TW and contributing to diapycnal mixing. The authors conduct sensitivity experiments with an ocean general circulation model assuming that the eddy energy is scattered into high-wavenumber vertical modes, resulting in energy dissipation and locally enhanced diapycnal mixing. When only the tidal energy dissipation maintains diapycnal mixing, the overturning circulation, and stratification in the deep ocean are too weak. With the addition of the eddy dissipation, the deep-ocean thermal structure becomes closer to that observed and the overturning circulation and stratification in the abyss become stronger. Furthermore, the mixing associated with the eddy dissipation can, on its own, drive a relatively strong overturning. The stratification and overturning in the deep ocean are sensitive to the vertical structure of diapycnal mixing. When most of this energy dissipates within 300 m above the bottom, the abyssal overturning and stratification are too weak. Allowing for the dissipation to penetrate higher in the water column, such as suggested by recent observations, results in stronger stratification and meridional circulation. Zonal circulation is also affected. In particular, the Drake Passage transport becomes closer to its observational estimates with the increase in the vertical scale for turbulence above topography. Consistent with some theoretical models, the Drake Passage transport increases with the increase in the mean upper-ocean diffusivity.
37
TSYPIN, V. S., A. G. ELFIMOV, C. A. de AZEVEDO y A. S. de ASSIS. "Alfvén-wave dissipation and current in strongly elongated tokamaks". Journal of Plasma Physics 60, n.º 2 (septiembre de 1998): 289–98. http://dx.doi.org/10.1017/s0022377898006850.
Resumen
The general approach to Alfvén-wave current drive and induced plasma rotation in tokamaks with strongly elongated transverse cross-sections is considered. Model approximations are used to describe the circulating- and trapped-particle dynamics in all particle-trapping regions. This approach gives an accuracy of some percent. New terms, connected with the wave dissipation on trapped particles in the second and third trapped-particle regions for elongated tokamaks, are taken into account. The plasma rotation and longitudinal current, depending on the absorbed power of kinetic Alfvén waves, are discussed.
38
Wang, Yang y Sonya Legg. "Enhanced Dissipation of Internal Tides in a Mesoscale Baroclinic Eddy". Journal of Physical Oceanography 53, n.º 10 (octubre de 2023): 2293–316. http://dx.doi.org/10.1175/jpo-d-23-0045.1.
Resumen
Abstract The dissipation of low-mode internal tides as they propagate through mesoscale baroclinic eddies is examined using a series of numerical simulations, complemented by three-dimensional ray tracing calculations. The incident mode-1 internal tide is refracted into convergent energy beams, resulting in a zone of reduced energy flux in the lee of the eddy. The dissipation of internal tides is significantly enhanced in the upper water column within strongly baroclinic (anticyclonic) eddies, exhibiting a spatially asymmetric pattern, due to trapped high-mode internal tides. Where the eddy velocity opposes the internal tide propagation velocity, high-mode waves can be trapped within the eddy, whereas high modes can freely propagate away from regions where eddy and internal wave velocities are in the same direction. The trapped high modes with large vertical shear are then dissipated, with the asymmetric distribution of trapping leading to the asymmetric distribution of dissipation. Three-dimensional ray tracing solutions further illustrate the importance of the baroclinic current for wave trapping. Similar enhancement of dissipation is also found for a baroclinic cyclonic eddy. However, a barotropic eddy is incapable of facilitating robust high modes and thus cannot generate significant dissipation of internal tides, despite its strong velocities. Both energy transfer from low to high modes in the baroclinic eddy structure and trapping of those high modes by the eddy velocity field are therefore necessary to produce internal wave dissipation, a conclusion confirmed by examining the sensitivity of the internal tide dissipation to eddy radius, vorticity, and vertical scale. Significance Statement The oceanic tides drive underwater waves at the tidal frequency known as internal tides. When these waves break, or dissipate, they can lead to mixing of oceanic heat and salt which impacts the ocean circulation and climate. Accurate climate predictions require computer models that correctly represent the distribution of this mixing. Here we explore how an oceanic eddy, a swirling vortex of order 100–400 km across, can locally enhance the dissipation of oceanic internal tides. We find that strong ocean eddies can be hotspots for internal tide dissipation, for both clockwise and anticlockwise rotating vortices, and surface-enhanced eddies are most effective at internal tide dissipation. These results can improve climate model representations of tidally driven mixing, leading to more credible future predictions.
39
Melrose, D. B. "Energy Dissipation due to Mass Loss in a Rotating System". Publications of the Astronomical Society of Australia 10, n.º 1 (1992): 48–51. http://dx.doi.org/10.1017/s1323358000019226.
Resumen
AbstractWhen a rotating magnetised system (angular speed Ω), such as a planet or star, loses mass there is necessarily an energy dissipation associated with the mass loss. Consider mass loss at rate M, such that the matter is flung off with the orbital speed ΩR1, at a radius R1 ≫ R0, where R0 is the radius of the planet or star. The power released is approximately equal to the power Prot = 1/2MΩ2R2 carried off in rotational kinetic energy. Part of the energy released is carried off as magnetic energy in the escaping plasma, and the remainder is released through dissipation of currents. Such dissipation plausibly leads to the acceleration of particles. The power released should be important for Jupiter and for some rapidly rotating stars. For most stellar systems, the power released is small compared to that required to drive a wind.
40
Korytov, M. S. y A. E. Bezrodina. "Development of a mathematical model of a stacker crane with regard to energy dissipation". Nauchno-tekhnicheskiy vestnik Bryanskogo gosudarstvennogo universiteta 9, n.º 2 (25 de junio de 2023): 134–44. http://dx.doi.org/10.22281/2413-9920-2023-09-02-134-144.
Resumen
Stacker cranes are widely used in automated warehouses. The actual task is to increase their energy efficiency and productivity. Simulation mathematical models are used for the solution of this problem at the stage of research and development works. We have developed a mathematical model of a rack stacker crane in long spatial displacements taking into account energy dissipation of linear coordinates of the cart and the cargo carriage. The model is a system of two second-order Lagrange differential equations. Partial derivatives of analytical expressions of kinetic and potential energies of the dynamic stacker crane system as well as dissipative Rayleigh function are used for derivation of the differential equations. Different values of dissipation coefficients for two linear coordinates of the stacker crane can be used. Using SimInTech we develop a simulation model of a conventional stacker crane based on the suggested system of differential equations and represented in the form of a block diagram. The developed simulation model is described and an example of its use is given. A complex model of a shelf stacker crane includes as a constituent part a procedure of determining time intervals of equivalent-accelerated motion of the links. Examples of time dependences of the crane bogie and cargo carriage coordinates, drive forces providing the set coordinate dependences, drives work and total work are given. The developed mathematical model of the stacker-crane can be used for the modelling of the processes of the cargo moving along the rack, its raising to the given height corresponding to the rack target cell, its lowering as well as for the estimation of the energy input of the crane.
41
Naveira Garabato, Alberto C. "A perspective on the future of physical oceanography". Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 370, n.º 1980 (13 de diciembre de 2012): 5480–511. http://dx.doi.org/10.1098/rsta.2012.0400.
Resumen
The ocean flows because it is forced by winds, tides and exchanges of heat and freshwater with the overlying atmosphere and cryosphere. To achieve a state where the defining properties of the ocean (such as its energy and momentum) do not continuously increase, some form of dissipation or damping is required to balance the forcing. The ocean circulation is thought to be forced primarily at the large scales characteristic of ocean basins, yet to be damped at much smaller scales down to those of centimetre-sized turbulence. For decades, physical oceanographers have sought to comprehend the fundamentals of this fractal puzzle: how the ocean circulation is driven, how it is damped and how ocean dynamics connects the very different scales of forcing and dissipation. While in the last two decades significant advances have taken place on all these three fronts, the thrust of progress has been in understanding the driving mechanisms of ocean circulation and the ocean's ensuing dynamical response, with issues surrounding dissipation receiving comparatively little attention. This choice of research priorities stems not only from logistical and technological difficulties in observing and modelling the physical processes responsible for damping the circulation, but also from the untested assumption that the evolution of the ocean's state over time scales of concern to humankind is largely independent of dissipative processes. In this article, I illustrate some of the key advances in our understanding of ocean circulation that have been achieved in the last 20 years and, based on a range of evidence, contend that the field will soon reach a stage in which uncertainties surrounding the arrest of ocean circulation will pose the main challenge to further progress. It is argued that the role of the circulation in the coupled climate system will stand as a further focal point of major advances in understanding within the next two decades, supported by the drive of physical oceanography towards a more operational enterprise by contextual factors. The basic elements that a strategy for the future must have to foster progress in these two areas are discussed, with an overarching emphasis on the promotion of curiosity-driven fundamental research against opposing external pressures and on the importance of upholding fundamental research as the apex of education in the field.
42
Konowrocki, Robert, Agnieszka Pręgowska y Tomasz Szolc. "Experimental and Numerical Investigations for the Controlled Rotary Damper Dynamically Interacting with the Electromechanical Rotating System". Solid State Phenomena 240 (agosto de 2015): 198–205. http://dx.doi.org/10.4028/www.scientific.net/ssp.240.198.
Resumen
In the paper dynamic electromechanical coupling between the structural model of the rotating machine drive system and the circuit model of the asynchronous motor has been investigated. By means of the computer model of the rotating machine drive system the results of experimental testing have been confirmed. From the obtained results of computations and measurements it follows that the coupling between the considered rotating system and the installed rotary dampers with the magneto-rheological fluid (MRF) results in effective energy dissipation leading to significant reduction of undesired torsional vibrations.
43
Jin, Chun, Di Wu y Yan Hua Shen. "Heat Dissipation Design and Analysis of Large Power Inverters for Electric Drive Off-Road Mine Truck". Advanced Materials Research 681 (abril de 2013): 142–46. http://dx.doi.org/10.4028/www.scientific.net/amr.681.142.
Resumen
The environment of humidity and high temperature in underground metal mines is not conducive to the heat transfer of converter on electric drive mining truck, and the drive efficiency and lifetime of the equipment are lowered. The article calculated equivalent thermal resistance of radiator, analyzed main factors affecting thermal efficiency. Finite element software was applied to simulate the radiator temperature field of different inlet directions, and then determined fixing angle of air blower which had best cooling effect.
44
Nishida, Rina, Jianpeng Zhong y Tadahiko Shinshi. "Effect of Forced Liquid Cooling on the Voltage/Charge Displacement Characteristics of Stacked Piezoelectric Actuators during High-Frequency Drive". Actuators 10, n.º 11 (10 de noviembre de 2021): 297. http://dx.doi.org/10.3390/act10110297.
Resumen
Piezoelectric stack actuators (PESAs) are widely used in applications requiring a fast response, high resolution, and high accuracy. The self-heating of a PESA during continuous drive with a large amplitude at high frequencies can change its voltage displacement and charge displacement characteristics. These changes can lead to a loss of stability and inaccurate PESA positioning systems. In this paper, we confirmed that by using our proposed forced liquid cooling, the changes to the dynamic characteristics and the impedance of a PESA due to the fact of self-heating could be reduced. Voltage displacement curve measurements at 10 kHz demonstrated that with natural heat dissipation, the amplitude of PESA increased by 15% due to the self-heating compared to the amplitude measured at the start of driving but only by 3% with forced liquid cooling. The displacement-to-charge ratio decreased by 12% compared to that at room temperature with natural heat dissipation, while it increased by 1% during forced liquid cooling. In the measured frequency response of the voltage displacement transfer function, the increased temperature changed the gain and phase of the first and secondary vibration modes above 20 kHz with natural heat dissipation. Forced liquid cooling also reduced the variations in the frequency response of the voltage displacement transfer function.
45
Ma, Sheng-li, Jing Zhang, Xin-ke Li, Ya-long Ren, Ji-kun Xie, Ming-tao Cao y Fu-li Li. "Coupling-modulation–mediated generation of stable entanglement of superconducting qubits via dissipation". EPL (Europhysics Letters) 135, n.º 6 (1 de septiembre de 2021): 63001. http://dx.doi.org/10.1209/0295-5075/ac2b5c.
Resumen
Abstract We propose an experimentally feasible scheme for the dissipative generation of stable entanglement of superconducting qubits via coupling modulation without applying any drives on qubits and resonator. Firstly, we study the circuit of one superconducting transmission line resonator coupled to two separated qubits via two superconducting quantum interference devices (SUQIDs). By modulating the inductance of the SQUIDs via external fluxes, we can tailor an appropriate qubit-resonator coupling with both red- and blue-sideband interactions. Combined with the photon loss of the resonator, the two qubits can be autonomously steered into a long-lived entangled state with high fidelity. Moreover, we extend the model to one resonator coupled to two separated qubit chains, each of which contains N linearly coupled superconducting qubits. We show that the lossy resonator can drive the whole system into a unique dark state, i.e., a series of N entangled pairs of qubits across the chains can be stabilized at the stationary state. So, the present work enables the preparation of a stable long-range entangled state between the two qubits in the end sites of the chains, which plays an important role for implementing scalable quantum computation and quantum communication.
46
Liu, Fang, Zhao Ya, Ligang Yuan, Yang Zeng, Caiyan Zhai, Zhuozhuang Tong, Juan Huang, Hao Li y Jiayi Liu. "Design approach for subsea data center based on thermodynamic theory under the premise of building energy conservation". Thermal Science 25, n.º 6 Part A (2021): 4209–16. http://dx.doi.org/10.2298/tsci2106209l.
Resumen
Traditional data centres often require additional energy to drive air conditioning fans etc. to dissipate heat due to the serious power generation problems of servers, which in effect raises the economic costs. Seawater, with its high specific heat capacity and fluidity, offers a viable research direction for reducing economic costs, and this paper is based on this problem. The study shows that it is feasible to use containers as the main structure of the data centre. The number of servers n 860 that can be tolerated by the cooling capacity of the container without considering the limit of geometrical constraints is obtained by calculation. Secondly, in order to enhance the heat dissipation capacity of the data centre, the 6 cm straight ribbed crown fin heat dissipation enclosure is proposed to have the best heat dissipation capacity when comparing various heat dissipation enclosure configurations. A comprehensive assessment model of material properties was established, and the weights of each straight index were determined by analytic hierarchy process, and then the metals were ranked according to the specific scores of each index. The results show that nickel alloys and aluminium alloys are the most suitable.
47
Di Cristofaro, Daniele, Andrea Opreni, Massimiliano Cremonesi, Roberto Carminati y Attilio Frangi . "An Arbitrary Lagrangian Eulerian Approach for Estimating Energy Dissipation in Micromirrors". Actuators 11, n.º 10 (18 de octubre de 2022): 298. http://dx.doi.org/10.3390/act11100298.
Resumen
Quantification and minimisation of energy consumption in resonant MEMS micromirrors is a key aspect for a proper structural design. In this setting, the quality factor Q of the drive mode of the device needs to be estimated and, eventually, improved. In this work, we propose a simulation strategy for the numerical computation of MEMS micromirrors quality factors. Full order Arbitrary Lagrangian Eulerian Navier-Stokes simulations have been performed using a SUPG stabilised Chorin-Themam scheme. Finally, the numerical results are compared with experimental data, highlighting the accuracy and efficiency of the proposed method.
48
Li, Cheng Qun, Xing Sun y Xiao Lei Dong. "Design of Pure Electric Vehicles’ Drive Motor Controller Based on dsPIC". Advanced Materials Research 139-141 (octubre de 2010): 2243–46. http://dx.doi.org/10.4028/www.scientific.net/amr.139-141.2243.
Resumen
To meet the industry demands of the drive motor controller of the pure electric vehicles, this paper introduces a design of the high-power brushless DC motor controller at the core of dsPIC30F6010A. Through the establishment of permanent magnet brushless DC motor (PMBLDC) mathematical model and the analysis of the running principle of it, the control scheme of pure electric vehicles was presented and the drive circuits, protection circuits and software programming of PMBLDC controller were designed in this paper. The paralled IGBT module is adopted as the drive circuits to solve the heat dissipation issues under the high current, PID is chosen as the control algorithm and cascade control is designed as the speed regulation.The simulation by MATLAB/simulink shows that the control scheme is reasonable, the system has fast response and smooth running.
49
Yang, Lining, Xiaoxia Sun y Tao Zhang. "Performance Simulation Analysis of Modular Heat Dissipation Unit". Journal of Physics: Conference Series 2160, n.º 1 (1 de enero de 2022): 012063. http://dx.doi.org/10.1088/1742-6596/2160/1/012063.
Resumen
Abstract In this paper, GT suite software is used to model the cooling system of military special vehicles with multiple power sources. The power drive system is composed of main engine, auxiliary engine and four hub motors. By constructing modular cooling unit, the volume of radiator and the layout of cooling unit are changed. While the total volume of radiator is unchanged, the cooling capacity of cooling system is improved. Firstly, the problem is simplified and modeled by high-temperature and low-temperature double circuit. The main engine with power of 600kW and auxiliary engine with power of 200kW are combined into a high-temperature circuit. The water temperature of the circuit is higher, about 90 ºC; Four hub motors with power of 440kw and their electrical components are combined into a low temperature circuit. The water temperature of this circuit is about 60 ºC. By modifying the volume, layout and number of radiators, the temperature of the dual circuit is analyzed, and it is found that when the total radiator volume remains the same, the cooling effect of the multi-radiator layout is better.
50
Guha, Arnab, Niklas Sandström, Victor P. Ostanin, Wouter van der Wijngaart, David Klenerman y Sourav K. Ghosh. "Simple and ultrafast resonance frequency and dissipation shift measurements using a fixed frequency drive". Sensors and Actuators B: Chemical 281 (febrero de 2019): 960–70. http://dx.doi.org/10.1016/j.snb.2018.11.052.