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• Impinging paper-thin sheets of liquids produces high energy dissipation rates. • The volume of energy dissipation is equal to the volume of the impingement zone. • A new expression for the energy dissipation rate was derived and compared with turbulence theory. • Large-eddy turnover time is approximately equal to liquid residence time in impingement zone. • Large-eddy kinetic energy decays exponentially in the impingement zone. The micromixing time of impinging thin liquid sheets depends upon the energy dissipation rate (∊). The kinetic energy released by the impingement has been previously studied and was found to be a function of the coefficient of restitution of the collision. In this work, the volume within which the released kinetic energy is dissipated was investigated. The volume of energy dissipation was determined by measuring the time required for the velocity of the liquid prior to the collision to be reduced to the velocity after the collision. High-speed video was used to measure the velocity of features, generated in the front single sheet, as they passed through the impingement zone and into the mixed sheet. The experimental results showed that the time required for the velocity change was approximately equal to the residence time of liquid in the impingement zone (t r). A new equation for ∊ was developed and compared with ∊ derived from turbulence energy-cascade theory. This comparison showed that the large-eddy turnover time (t Λ) was approximately equal to t r ; a result that is in accordance with the notion from turbulence energy-cascade theory that large, energy-containing eddies lose their energy within t Λ. Within the impingement zone, the large-eddy kinetic energy was found to decay exponentially with time. [ABSTRACT FROM AUTHOR]

The revised, regularized Tao–Mo (rregTM) exchange-correlation density functional approximation (DFA) [A. Patra, S. Jana, and P. Samal, J. Chem. Phys. 153, 184112 (2020) and Jana et al., J. Chem. Phys. 155, 024103 (2021)] resolves the order-of-limits problem in the original TM formulation while preserving its valuable essential behaviors. Those include performance on standard thermochemistry and solid data sets that is competitive with that of the most widely explored meta-generalized-gradient-approximation DFAs (SCAN and r2SCAN) while also providing superior performance on elemental solid magnetization. Puzzlingly however, rregTM proved to be intractable for de-orbitalization via the approach of Mejía-Rodríguez and Trickey [Phys. Rev. A 96, 052512 (2017)]. We report investigation that leads to diagnosis of how the regularization in rregTM of the z indicator functions (z = the ratio of the von-Weizsäcker and Kohn–Sham kinetic energy densities) leads to non-physical behavior. We propose a simpler regularization that eliminates those oddities and that can be calibrated to reproduce the good error patterns of rregTM. We denote this version as simplified, regularized Tao–Mo, sregTM. We also show that it is unnecessary to use rregTM correlation with sregTM exchange: Perdew–Burke–Ernzerhof correlation is sufficient. The subsequent paper shows how sregTM enables some progress on de-orbitalization. [ABSTRACT FROM AUTHOR]

This paper reviews key advances in understanding the hydrodynamics of the forming section of papermaking during the years 1950 to 2000. Over this period papermaking advanced from rather slow-speed Fourdrinier machines to modern high-speed twin-wire formers. The advances are described in the context of technical problems faced at the time to increase machine speeds and improve paper properties. The scientific work and advances in machine design contributed greatly to the marvel of modern papermaking, which now includes machines 10 m wide operating at speeds over 100 km/h. [ABSTRACT FROM AUTHOR]

The Pauli kinetic energy functional and its functional derivative, termed Pauli potential, play a crucial role in the successful implementation of orbital-free density functional theory for electronic structure calculations. However, the exact forms of these two quantities are not known. Therefore, perforce, one employs the approximate forms for the Pauli functional or Pauli potential for performing orbital-free density functional calculations. In the present study, we developed a feed-forward neural network-based representation for the Pauli potential using a 1-dimensional (1-D) model system. We expanded density in terms of basis functions, and the coefficients of the expansion were used as input to a feed-forward neural network. Using the neural network-based representation of the Pauli potential, we calculated the ground-state densities of the 1-D model system by solving the Euler equation. We calculated the Pauli kinetic energy using the neural network-based Pauli potential employing the exact relation between the Pauli kinetic energy functional and the potential. The sum of the neural network-based Pauli kinetic energy and the von Weizsäcker kinetic energy resulted in an accurate estimation of the total kinetic energy. The approach presented in this paper can be employed for the calculation of Pauli potential and Pauli kinetic energy, obviating the need for a functional derivative. The present study is an important step in the advancement of application of machine learning-based techniques toward the orbital-free density functional theory-based methods. [ABSTRACT FROM AUTHOR]

This paper presents a novel coupling of a kinetic description of neutrals with a fluid description of a fusion plasma. The code, plasma interacting super-atoms and molecules (PISAM), employs a grid-free Cartesian geometry and a direct simulation Monte Carlo approach to solve the kinetic equations of deuterium atoms and molecules. The grid-free geometry and the parallel nature of the neutral dynamics, in the absence of neutral–neutral interactions, allow for an unlimited and work-efficient parallelization of PISAM that always ensures a balanced workload. The highly optimized Python implementation obtains good performance while securing easy accessibility to new users. The coupling of PISAM with the edge turbulence model HESEL is outlined with emphasis on the technical aspects of coupling Message Passing Interface-parallelized Python and C++ codes. Furthermore, the paper presents and analyzes simulation results from running the coupled HESEL-PISAM model. These results demonstrate the impact of radial neutral transport and plasma–neutral dynamics perpendicular to the magnetic field. Specifically, they illustrate how the inward flow of neutral kinetic energy and the inhibition of radial electric shear, resulting from poloidal momentum transfer between atoms and ions, can affect the energy containment time. By comparing the results of the HESEL-PISAM model with those obtained from coupling HESEL with a diffusive-fluid-neutral model, the capabilities of diffusion models in predicting neutral transport in the plasma edge and scrape-off layer are elucidated. [ABSTRACT FROM AUTHOR]

The paper presents a simple yet rigorous analysis of the transient of the spatial distribution of the kinetic energy of a classical ideal monoatomic dilute gas that passes from non-equilibrium to equilibrium. The proposed approach is event-based, in the sense that the evolution of the system is analyzed as a function of the random number of collisions in a given time interval. Taking a very simple yet realistic model of collision, the paper shows that collisions between atoms lead exponentially to energy equipartition. [ABSTRACT FROM AUTHOR]

The supersaturation equation for a vertically moving adiabatic cloud parcel is analyzed. The effects of turbulent updrafts are incorporated in the shape of a stochastic Lagrangian model, with spatial and time correlations expressed in terms of turbulent kinetic energy. Using the Fokker–Planck equation, the steady-state probability distributions of supersaturation are analytically computed for a number of approximations involving the time-scale separation between updraft fluctuations and phase relaxation, and droplet or ice particle size fluctuations. While the analytical results are presented in general for single-phase clouds, the calculated distributions are used to compute mixed-phase cloud properties—mixed fraction and mean liquid water content in an initially icy cloud—and are argued to be useful for generalizing and constructing new parameterization schemes. Significance Statement: Supersaturation is the fuel for the development of clouds in the atmosphere. In this paper, our goal is to better understand the supersaturation budget of clouds embedded in a turbulent environment by analyzing the basic equations of cloud microphysics. It is found that the turbulent characteristics of an air parcel substantially affect the cloud's supersaturation budget and hence its life cycle. This is also shown in the context of mixed-phase clouds where, depending on the turbulent regime, different liquid-to-ice ratios are found. Consequently, the theoretical approach of this paper is crucial to develop tools to parameterize small-scale atmospheric features, like clouds, into global circulation models to improve climate projections for the future. [ABSTRACT FROM AUTHOR]

In order to solve the blockage effect and energy dissipation phenomenon caused by cavitation in the low-pressure vortex core region, this paper analyzes the spatial evolution of vorticity intensity and turbulent kinetic energy intensity under different cavitation conditions based on the Wray–Agarwal (WA) model. First, the tip leakage flow characteristics are studied, the evolution of vorticity and vorticity intensity is analyzed, then the distribution of turbulent kinetic energy distribution in the blade tip region is studied, and finally, the vorticity transport characteristics of the tip region are analyzed. It is found that the tip leakage rate is less affected by the vortex cavitation of the tip leakage, and there is a strong interaction between the leakage flow at the tip leading edge and the trailing edge, and the separation vortices and low-speed regions formed in the end-wall region cause blockage of the flow passage. Low pressure causes cavitation to cover most regions of the suction surface, inhibiting the formation and development of the tip leakage vortices. The distribution range of high turbulent kinetic energy region is almost the same as that of high-vorticity region, and there is a positive correlation between the two intensities. Severe cavitation causes the high turbulent kinetic energy region at the outlet of the flow passage to develop in the radial and axial directions of the impeller, which increases the turbulent dissipation and energy loss. The change of vorticity transport intensity caused by cavitation is mainly reflected in the expansion contraction term, and the Coriolis force term plays a dominant role in the vorticity transport process. This paper provides a reference for further improving the performance of mixed-flow pumps. [ABSTRACT FROM AUTHOR]

Purpose: In the post-capture stage, the tumbling target rotates the combined spacecraft system, and the detumbling operation performed by the space robot is required. To save the costly onboard fuel of the space robot, this paper aims to present a novel post-capture detumbling strategy. Design/methodology/approach: Actuated by the joint rotations of the manipulator, the combined system is driven from three-axis tumbling state to uniaxial rotation about its maximum principal axis. Only unidirectional thrust perpendicular to the axis is needed to slow down the uniaxial rotation, thus saving the thruster fuel. The optimization problem of the collision-free detumbling trajectory of the space robot is described, and it is optimized by the particle swarm optimization algorithm. Findings: The numerical simulation results show that along the trajectory planned by the detumbling strategy, the maneuver of the manipulator can precisely drive the combined system to rotate around its maximum principal axis, and the final kinetic energy of the combined system is smaller than the initial. The unidirectional thrust and the lower kinetic energy can ensure the fuel-saving in the subsequent detumbling stage. Originality/value: This paper presents a post-capture detumbling strategy to drive the combined system from three-axis tumbling state to uniaxial rotation about its maximum principal axis by redistributing the angular momentum of the parts of the combined system. The strategy reduces the thrust torque for detumbling to effectively save the thruster fuel. [ABSTRACT FROM AUTHOR]

Hydrogen ejectors effectively utilize excess unreacted hydrogen. However, traditional ejectors have limited operational ranges and are only suitable for specific power ranges. This paper presents a dual-nozzle ejector aimed at broadening its operational range through different working modes. A simulation model, validated by experiments, is employed based on the working principles of ejectors. Spiral blades are installed at drive end to improve the recirculation efficiency. Flow characteristics, including streamwise and spanwise vortices at high power, are also investigated in different modes. Results indicate that optimal operating range for Ring-nozzle(RN) mode is between 31.1 and 124.4A. When output current exceeds 124.4A, it is necessary to switch to Central-nozzle (CN) or Double-nozzles (DNs) mode. Analysis of streamlines and velocity vectors reveals that installing spiral blades can modify directions of primary flow. Blades with appropriate distortion should be selected. In CN mode, when stack reaches 60% of rated power, installing 20° spiral blades has a minimal impact on stability of radial flow. Installing 30° or 40° spiral blades is suitable for full-load condition. In DNs mode, installing 30° spiral blades enhances acceleration of gas flow with lower influence from radial influx. This ejector provides assurance for upgrade of fuel cell stacks by incorporating recirculation technology. • A dual-nozzle ejector with spiral guide blades is designed, verified and evaluated. • Installed spiral blades change direction and gather kinetic energy of primary flow. • Advantageous working conditions of different modes with blades are discussed. • Flow mechanism of different blades under high power in two modes is analyzed. • Flow acceleration and losses should be balanced by changing the twist of blades. [ABSTRACT FROM AUTHOR]

In recent years, wind power generation has been promoted as a countermeasure to global environmental problems. However, the introduction of many wind power generators into the power system may cause system frequency fluctuations. This paper proposes a control method to reduce system frequency fluctuations by using the rotor kinetic energy (RKE) of a variable speed wind turbine (VSWT). When the frequency falls, this method suppresses fluctuations by consuming RKE to increase VSWT power generation, and when it rises, it decreases VSWT power generation by accumulating RKE. The effectiveness of this method is confirmed through simulations using PSCAD/EMTDC. [ABSTRACT FROM AUTHOR]

Dynamics modeling and analysis of a rotating piezoelectric laminated beam (RPLB) considering the effect of the setting angle is presented in this paper. The rotating piezoelectric energy harvester can be simplified as a RPLB which is fixed at a rotating hub. It is easy to know that a steady transversal deformation would be produced due to the transversal component of centrifugal force when the beam is not along the radial direction (the setting angle is not equal to 0° or 180°). However, the variation of steady transversal deformation and its effect were rarely considered by existing theoretical models about the rotating harvesters. To this end, a novel nonlinear dynamics model of the RPLB is developed by the combination of floating frame reference (FFR) and absolute nodal coordinate formulation. In the model, the position coordinates and gradients on the FFR are used as the nodal coordinates to describe deformation field. The enthalpy, elastic and kinetic energies of the RPLB are derived with consideration of the piezoelectric constitutive equation and the rotation of the FFR. Thus, the dynamics equations of the RPLB can be developed by using the Lagrange's equations of second kind. The results obtained from the model show agreement with those obtained from the previous literatures, which verifies the correctness of the model. Several examples are presented to analyze the effects of rotating speed, setting angle and tip mass on steady transversal deformation, output voltage and modal characteristics. • A novel nonlinear dynamics model of RPLB is developed to benefit the design of piezoelectric energy harvesters. • Steady deformation caused by transversal component of centrifugal force and its effects are investigated and analyzed. • Variations of the dynamic stiffening / softening of RPLB with setting angle and its reason are discussed. • Tensile strains and compression strains respectively lead to dynamic stiffening and softening. [ABSTRACT FROM AUTHOR]

In this paper, attention is focused on the analysis and optimization of energy flows in networked systems via a fluid-dynamic approach. Considering the real case of an energy hub, the proposed model deals with conservation laws on arcs and linear programming problems at nodes. Optimization of the energy flows is accomplished by considering a cost functional, which estimates a term proportional to the kinetic energy of the overall system in consideration. As the real optimization issue deals with an integral formulation for which precise solutions have to be studied through variational methods, a decentralized approach is considered. First, the functional is optimized for a simple network having a unique node, with an incoming arc and two outgoing ones. The optimization deals with distribution coefficients, and explicit solutions are found. Then, global optimization is obtained via the local optimal parameters at the various nodes of the real system. The obtained results prove the correctness of the proposed approach and show the evident advantages of optimization procedures dealing with variational approaches. [ABSTRACT FROM AUTHOR]

Since the creation of the first parallel electrical power systems around the world, the rotor angle stability of synchronously operating generators has been one of the most crucial and challenging problems. In modern electricity networks, including in Kazakhstan, where renewable energy technologies are rapidly emerging, the issue of stability takes on even greater importance due to the technical shortcomings of inverter-based generation. In this framework, an analysis of rotor angle transient stability was carried out when replacing existing synchronous generators with doubly fed induction generators under a certain pre-emergency mode. A critical proportion of active power generation by DFIG units was identified at which transient stability can still be maintained due to the sufficient stored kinetic energy of the synchronous machines remaining in operation. In addition, two simple solutions were investigated to improve transient stability, such as an increased time of the automatic reclosure operation and the use of special load-shedding automation. Finally, this paper proposes a novel type of flexible smart-grid automation that is capable of monitoring the main operating parameters and issuing control actions depending on inertia, the availability of wind resources, and the load of the system as a whole. For this analysis, a real power system from the Mangystau region in Kazakhstan was considered, and the PowerWorld software 23 was used. [ABSTRACT FROM AUTHOR]

This paper presents the techno-typological study of seven bone projectile points closely associated with a burial assemblage excavated from El Alto 5 (~550 cal BP, Sierras of Córdoba, Argentina). The bone points provide a comparative model for interpreting the function of arrow points, primarily concerning how archaeologists can accurately differentiate the arrow tips used for warfare or hunting. Bone points have barbed shoulders to resist removal from the wound and serrated stems for secure hafting. They required shafts a few millimeters thicker than stone-tipped arrows for hafting, involving more kinetic energy to inflict severe injuries. Identifying a dark residue spattered over the blades opens the possibility that poison was applied to enhance the effectiveness of the shoot. The study is considered a starting point to build more accurate models to identify interpersonal violence during the Late Prehispanic Period, where most bone points occurred as domestic refuse of campsites. [ABSTRACT FROM AUTHOR]

The turbulence observed in the stirred tank is a result of the superposition of flows at different scales, each exerting various influences on the operational processes. To understand the flow characteristics associated with stirring, this paper undertakes particle image velocimetry (PIV) experimental research on an unbaffled tank stirred by an open turbine featuring four distinct blade deflection angles. The flow field in the unbaffled tank manifests as a double‐circulation flow pattern; however, it is worth noting that the blade deflection angle exerts a significant impact on the stirring process. Specifically, when the blade deflection angle reached 90°, the flow discharge aligned closely with the radial direction, accompanied by pronounced fluctuations in the high‐velocity region. The Lagrangian coherent structures (LCS) formed were subsequently extracted and subjected to finite‐time Lyapunov exponent (FTLE) analysis. Notably, a more regular wake pattern emerged in proximity to the blade tip, while a larger scale flow structure persisted along the flow direction. To systematically analyze the flow field stirred by the open turbine, modal analysis was employed. By reconstructing the flow field based on the principle of 50% energy content, the decomposition of flows at different scales was achieved. The turbulent kinetic energy (TKE) generated by the various scale flows was subsequently calculated, revealing that the high TKE values primarily originate from the large‐scale flow structure. Conversely, the TKE generated by the small‐scale flow exhibits a uniform distribution across different regions. Notably, in regions characterized by higher velocities, the peak TKE associated with the small‐scale flow also manifests; however, it is significantly smaller in magnitude compared to that generated by the original flow or the large‐scale flow. [ABSTRACT FROM AUTHOR]

The increasing performance requirements for aero-engines necessitate the integrated design of compressor transition ducts with upstream components to reduce the axial length of the engine. This paper presents an experimental investigation of three-dimensional (3D) blade designs within an aggressive compressor transition duct integrated with the upstream stator. The aim is to reduce the total pressure loss and decrease the radial distortion of the flow field at the outlet of the transition duct, thus providing better inflow conditions for the high-pressure compressor. Detailed measurements of the internal flow field were conducted under both near stall (NS) and design (DE) conditions for three 3D blades. The results showed that in the downward path, adopting the 3D blades with positive dihedral and forward sweep contributed to mitigating the stator hub corner stall under the NS condition. Under the same operating conditions, enhanced kinetic energy at the stator root improved the spanwise uniformity of the transition duct outlet profile, while also increasing the anti-separation capability of the downstream hub boundary layer. The corner vortex at the stator root could enhance momentum mixing between the downstream hub boundary layer and the mainstream, thereby providing stronger separation resistance for the hub boundary layer under the NS condition. Compared to the baseline stators, the optimized 3D stators reduced system total pressure loss by 24% under the NS condition, while maintaining essentially unchanged total pressure loss under the DE condition. [ABSTRACT FROM AUTHOR]

Turbulent kinetic energy (TKE) is a quantity of primary importance in shock–turbulence interaction (STI). Linear interaction analysis (LIA) serves as a theoretical method to predict the amplification of TKE in STI. LIA is constrained by low-amplitude fluctuations and neglects nonlinear effects. In this paper, we explore the nonlinear amplification of the kinetic energy of fluctuations in the interaction between a vorticity wave and a shock wave that serves as a building block flow for STI. A weakly nonlinear framework (WNLF) is introduced to analyze nonlinear effects in fluctuation kinetic energy (FKE) and identify the dominant physical mechanisms driving its amplification. The theoretical framework is validated through high-accuracy numerical simulations of shock–vorticity wave interactions. The simulation results are compared with the predictions derived from the WNLF for a range of intensities and inclinations of shock-upstream vorticity fluctuations at different Mach numbers, and WNLF is found to successfully scale the numerical data for FKE, thus confirming the validity and applicability of the framework. According to WNLF findings, at lower supersonic Mach numbers, the intermodal interaction between vorticity–vorticity modes is important, whereas the interaction between vorticity and acoustic modes becomes dominant at higher Mach numbers. Using the intermodal interactions, a model based on WNLF is proposed to predict TKE amplification in STI. In comparison to direct numerical simulation, the WNLF based model predicts the TKE amplification for moderate turbulent Mach number and lower supersonic flow Mach numbers. This is a significant improvement over the LIA results available in the literature. [ABSTRACT FROM AUTHOR]

A brand-new type of multislot and pool–weir combined fishway (MSWF) is firstly proposed in this paper. In fact, six MSWF configurations (MSWF-1 to MSWF-6) are designed and compared, and numerical results demonstrate that MSWF-5 (i.e., weir height h=0.6 m and the vertical-slot width bs=0.62 m) has the best performance at a flow discharge (i.e., Q) of 600 L/s in terms of flow topology, velocity distribution, and turbulent kinetic energy among all the eight fishways considered. The introduction of the weir in MSWF not only contributes to improving the flow regime, but also offers an extra fish-passage channel for fishes. Moreover, the general superiority of MSWF-5 over the vertical-slot fishway (VSF) is exhibited by providing the numerical results at Q=600 , 800, 1,000, and 1,200 L/s. Additionally, fish-passage tests are carried out in a physical model (including the MSWF-5 part and the VSF part) with the aid of juvenile grass carps. As expected, the recommended MSWF-5 does outperform VSF with respect to passage success rate, mean fish transit time, entry efficiency, and mean entrance time, matching its excellent hydraulic properties. [ABSTRACT FROM AUTHOR]

Municipal drainage systems can transmit harmful microorganisms such as COVID-19 virus through wastewater as well as drain airflow with suspended tiny bio-droplets. The generation of tiny droplets in drainage systems can be simplified as the phenomenon of jet impingement and splashing, which is also common in industries, but the size and velocity correlation and the kinetic energy of splashing droplets remain unclear. This paper uses high-speed photography to study splashing from a jet impinging on a horizontal plate. Since the jet can break into successive drops before impingement, successive drops impingement and continuous jet impingement are defined and their splashing modes are revealed. Successive drops impingement and continuous jet impingement, respectively, produce splashing droplets with sizes smaller than 0.25 and 0.30 times the size of the impact drops and jet, and with the velocities up to 3.0 and 1.5 times the impact velocity. Correlations between size and velocity of splashing droplets are established: the range and maximum of velocity increase as diameter decreases, and the high velocity splashing droplets have ejection angles within 10° to 20°. For successive drops impingement, the percentage of total kinetic energy of splashing droplets relative to impact kinetic energy increases with impact Weber number and can reach nearly 50%; however, it varies little with impact Weber number for continuous jet impingement, reaching only 10%. Successive drops impingement produces more splashing droplets characterized by a combination of smaller size, higher velocity and larger ejection angle, resulting in a greater risk of producing airborne microorganisms. [ABSTRACT FROM AUTHOR]

Polytetrafluoroethylene/aluminum (PTFE/Al) reactive material is a pivotal research object in the aerospace, military, and mechanical engineering fields and can release chemical energy (CE) under shock or impact. However, its relatively low mechanical strength limits its applications. The present paper proposes a Cu-PTFE/Al (73.5wt. %/26.5wt. %) double-layer liner that can form tandem explosive formed projectiles (EFPs) under the shock of shaped charges, which not only retains the strong penetration ability but also shows a more significant lateral enhancement effect through the deflagration reaction. Here, the preparation process of the PTFE/Al liner is given, and an analytical model for the Cu-PTFE/Al tandem EFP of the damage process against multi-spaced plates is established, revealing the penetration and deflagration-enhanced mechanisms. Subsequently, a two-step segmented numerical simulation for the penetration–deflagration coupling effects is conducted, and the time-space interaction process and damage results between kinetic energy penetration and CE deflagration are obtained. A series of experiments of tandem EFPs against spaced plates are conducted, including the different materials, thickness ratio, and standoff. Experimental results show that compared with Cu–Cu tandem EFP with the same condition, the penetration ability of Cu-PTFE/Al composite EFP is reduced, but the damage enhancement effect is greatly improved; the maximum damage area of a single plate is increased by 220.1%, and the average damage area of a single plate is increased by 76.2%. This study provides important reference data and a theoretical basis for the design of metal-reactive tandem EFPs. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the dynamic properties of spin-orbit coupling spin-1 ferromagnetic Bose-Einstein condensates with different trap geometry. Our results are obtained in terms of the threecomponent Gross-Pitaevskii equation of mean-field theory. Two kinds of trap potential are discussed: isotropic and anisotropic. It is shown that the spin-exchange dynamics are greatly influenced by trap geometry. For the latter with weak spin-orbit coupling strength, we find that the three-component oscillation accelerates and some small difference emerges between component m = 1 and m = -1. With the increase in spin-orbit coupling strength, the three components reach almost the same population. In addition, the kinetic energy of the system changes within a small scope for strong spin-orbit coupling, as opposed to a constant value in an isotropic trap. The density distributions display that the stripe phase appears with the increase in spin-orbit coupling strength. The method of generating stripe structure is different from the ground state of ferromagnetic condensate. For isotropic trap, the spatial separation of top and bottom spin-orbit condensates in component m = 1 and m = -1 occurs at weak spin-orbit coupling, and square lattice appears at strong spin-orbit coupling. [ABSTRACT FROM AUTHOR]

In this paper, we propose an effective linearly implicit unconditional energy-stable scheme for surface quasi-geostrophic flows based on the scalar auxiliary variable approach and the Fourier spectral Galerkin method. Compared with traditional numerical methods, our scheme has constant coefficient matrices at each time step, and the numerical solutions are consistent with the dissipation laws for modified energy. By treating linear terms implicitly and nonlinear terms explicitly, we derive the dissipation laws for discrete modified surface kinetic energy and Hamiltonian. To reduce the aliasing error induced by the Fourier spectral Galerkin method, we implement a 2/3 de-aliasing technique for the nonlinear terms. Furthermore, the integration concerning energy in our numerical scheme is exact due to the Fourier spectral Galerkin method. Numerical experiments are presented to verify the stability and efficiency of the proposed scheme. [ABSTRACT FROM AUTHOR]

The shear stress transport turbulence model is employed to conduct a detailed study of flow characteristics at the highest efficiency point and near-stall point in a full-channel 1.5-stage compressor in this paper. The simulation results for the compressor's total pressure ratio and efficiency exhibit good agreement with experimental data. Emphasis is placed on examining the internal flow structure in the tip area of the compressor rotor under near-stall conditions. The results reveal that significant differences in flow structure primarily occur in the tip area as the compressor approaches stall. Specifically, a reduction in turbulent kinetic energy is observed in a region spanning approximately 20%–60% of the chord length on the rotor suction face near-stall conditions. Two additional peak frequencies, at 0.8 and 1.6 times the blade passage frequency, are observed, and the intricate flow phenomena are elaborated at the near-stall point. The near-stall point exhibits greater noise levels than the highest efficiency point, where the intensity of the surface source increases by more than 10 dB, peaking at 20 dB. This additional peak serves as a significant supplementary noise source near the stall point, leading to a maximum increase of 33.3 dB in the free radiated sound power. The acoustic response within the duct indicates that the compressor operating at the near-stall point continues to produce substantial noise on the actual test bench, showing an average increase of 6 dB in noise levels, and the distribution of the additional peak single-tone noise at the entrance significantly differs from that observed at the highest efficiency point. [ABSTRACT FROM AUTHOR]

Experimental study of reinforced concrete beams without stirrups under impact: performance evaluation and structural response Experiments on reinforced concrete beams without stirrups are often utilized as a simplified basis to calibrate numerical models of reinforced concrete slabs. This paper details an experimental study on the behavior of reinforced concrete beams without stirrups subjected to impact loading. For this study, the 11‐meter‐high drop tower at the Otto Mohr Laboratory of TU Dresden was used to accelerate a cylindrical impactor with a diameter of 100 mm. Compressed air accelerated the impactor to velocities between 2.7 m/s and 25.8 m/s. The impactor masses were 14.22 kg and 21.66 kg, respectively. Data on impactor and support forces, displacements, and accelerations were collected. Digital image correlation supplemented the measurements. The study revealed that the behavior of the beams exhibited different failure modes depending on the impactor velocity and mass. The shear cracks started to form at impactor velocities of approximately 11 m/s, corresponding to the lighter impactor's kinetic energy of 860 J. Furthermore, the formation of a punching cone near the loading point at impactor velocities of around 22 m/s was observed. These findings provide valuable insights for designing and thoroughly assessing the performance of shear‐deficient reinforced concrete beams under impact loading. The results serve as a foundation for enhancing the precision and reliability of numerical models, facilitating further investigations into complex structural systems. [ABSTRACT FROM AUTHOR]

In the theory of special relativity, energy can be found in two forms: kinetic energy and rest mass. The potential energy of a body is actually stored in the form of rest mass, the interaction energy too, but temperature is not. Information acquired about a dynamical system can be potentially used to extract useful work from it. Hence, the "mass–energy–information equivalence principle" that has been recently proposed. In this paper, it is first recalled that for a thermodynamic system made of non-interacting entities at constant temperature, the internal energy is also constant. So, the energy involved in a variation in entropy ( T Δ S ) differs from a change in the potential energy stored or released and cannot be associated to a corresponding variation in mass of the system, even if it is expressed in terms of the quantity of information. This debate gives us the opportunity to deepen the notion of entropy seen as a quantity of information, to highlight the difference between logical irreversibility (a state-dependent property) and thermodynamical irreversibility (a path-dependent property), and to return to the nature of the link between energy and information that is dynamical. [ABSTRACT FROM AUTHOR]

In order to achieve intelligent operation of subway transportation, this paper proposed a dual-function system integrating human kinetic energy harvesting and passenger sensing for self-powered subway pedestrian flow diversion. The proposed dual-function system mainly includes the energy harvesting module, the data acquisition and processing module, and the information transmission module. The most important module is the energy harvesting subsystem, which is a pacemaker for the dual-function system to work successfully. Therefore, this paper focuses on the structure, dynamics, electricity, and parameter analysis of the energy harvesting module. First, mechanical motion rectifier-based vibration energy harvester (MMR-based VEH) is designed to scavenging the stepping energy of passengers. Secondly, the parameter analysis of the proposed MMR-based VEH is carried out. Finally, the prototype of the dual-function system is fabricated to test the energy output and passenger sensing performance. The results showed that the dual-function system can output a voltage of up to 18.5V and a power of approximately 1.8W. Simultaneously, the proposed dual-function system can accurately sense the human step and calculate the number of passenger. • A dual-function system integrating passenger sensing and energy harvesting is proposed. • Vibration-rotation-electric coupling model of vibration energy harvester is established. • The influence of structural parameters on power output performance is analyzed. • Prototype of the dual-function system with certain configuration is fabricated. [ABSTRACT FROM AUTHOR]

This paper examines an inertial response control for wind turbines in order to provide the system inertia decreased by the integration of asynchronous variable renewable energy sources. Specifically, an application of the temporal power surge, a strategy by which the output of a wind turbine can be temporarily increased with releasing the kinetic energy stored in the rotating mass, was proposed to address significant frequency drops in a microgrid. Since the rotational speed of turbine has to be decreased by this approach, it is necessary to further reduce the wind power output to recover the rotational speed after the temporal power surge. This drawback may lead to a second frequency drop, and it is effective to intentionally increase the rotational speed beforehand to mitigate this negative effect. However, this measure causes output curtailment under normal operating conditions. Hence, a determination method of the rotational speed considering the output curtailment was proposed in this paper to facilitate frequency regulation through the temporal power surge. The proposed methods for adjusting rotational speed are evaluated and their effectiveness were verified through numerical simulations. © 2023 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

Incorporating a guide vane-type spiral flow generator can effectively resolve particle deposition issues during long-distance pipeline conveyance. Combining model experiments and computational fluid dynamics (CFD) results under different guide vane height conditions, the paper investigated the structure of the circumferential velocity and the generated rotational effects of the guide vane-type spiral flow generator. Due to the combined effects of the guide vane constraint and water inertia, an envelope surface with a zero circumferential velocity exists along the inner edge of the guide vanes and in the direction of water flow. The envelope surface divides the circumferential flow velocity distribution into internal negative and external positive velocity zones. This paper discovered that the distribution of the envelope surface in the radial and axial directions is affected by both the height of the guide vanes and the Reynolds number. The rotational intensity of the fluid particles around the axis was characterized by the circumferential moment of momentum. When the relative height of the guide vane was 0.35, the highest percentage of circumferential flow velocity in the flow field was reached, while the rotational kinetic energy conversion efficiency was maximum. [ABSTRACT FROM AUTHOR]

Near-surface oceanic turbulence plays an important role in the exchange of mass, momentum, and energy between the atmosphere and the ocean. The climate modifying the air–sea CO 2 transfer rate varies linearly with the surface turbulent kinetic energy dissipation rate to the 1 / 4 power in a range of systems with different types of forcing, such as coastal oceans, river estuaries, large tidal freshwater rivers, and oceans. In the first part of this paper, we present a numerical study of the near-surface turbulent kinetic energy spectra deduced from a direct numerical simulation (DNS) compared to turbulent kinetic energy spectra deduced from idealized infrared (IR) images. The DNS temperature fields served as a surrogate for IR images from which we have calculated the underlying kinetic energy spectra. Despite the near-surface flow region being highly anisotropic, we demonstrated that modeled isotropic and homogeneous turbulence spectra can serve as an approximation to observed near-surface spectra within the inertial and dissipation ranges. The second part of this paper validates our numerical observations in a laboratory experiment. In this experiment, we compared the turbulent kinetic energy spectra near the surface, as measured using a submerged shear sensor with the spectra derived from infrared images collected from above the surface. The energy dissipation measured by the shear sensor was found to be within 20% of the dissipation value derived from the IR images. Numerically and experimentally, we have demonstrated that IR-based and remote measurement techniques of the aquatic near surface offer a potentially accurate and non-invasive way to measure near-surface turbulence, which is needed by the community to improve models of oceanic air–sea heat, momentum, and gas fluxes. [ABSTRACT FROM AUTHOR]

The spectrum of kinetic energy of vertical motions (VKE) is less well understood compared to the kinetic energy spectrum of horizontal motions (HKE). One challenge that has limited progress in describing the VKE spectrum is a lack of a unified approach to the decomposition of vertical velocities associated with the Rossby motions and inertia–gravity (IG) wave flows. This paper presents such a unified approach using a linear Rossby–IG vertical velocity normal-mode decomposition appropriate for a spherical, hydrostatic atmosphere. New theoretical developments show that for every zonal wavenumber k, the limit VKE is proportional to the total mechanical energy and to the square of the frequency of the normal mode. The theory predicts a VKE ∝ k−5 and a VKE ∝ k1/3 power law for the Rossby and IG waves, assuming a k−3 and a k−5/3 power law for the Rossby and IG HKE spectra, respectively. The Kelvin and mixed Rossby–gravity wave VKE spectra are predicted to follow k−1 and k−5 power laws, respectively. The VKE spectra for ERA5 data from August 2018 show that the Rossby VKE spectra approximately follow the predicted a k−5 power law. The expected k1/3 power law for the gravity wave VKE spectrum is found only in the SH midlatitude stratosphere for k ≈ 10–60. The inertial range IG VKE spectra in the tropical and midlatitude troposphere reflect a mixture of ageostrophic and convection-coupled dynamics and have slopes between −1 and −1/3, likely associated with too steep IG HKE spectra. The forcing by quasigeostrophic ageostrophic motions is seen as an IG VKE peak at synoptic scales in the SH upper troposphere, which gradually moves to planetary scales in the stratosphere. Significance Statement: The spectrum of kinetic energy of vertical motions (VKE) is less well understood compared to the kinetic energy spectrum of horizontal motions. One challenge is a lack of a unified approach to the decomposition of vertical velocities associated with the Rossby motions and inertia–gravity (IG) wave flows. This paper presents such a unified approach using a linear Rossby–IG vertical velocity normal-mode decomposition appropriate for a spherical, hydrostatic atmosphere. It is shown that for every zonal wavenumber, the limit VKE is proportional to the total mechanical energy and to the square of the frequency of the normal mode. The theory is successfully applied to the ERA5 data. It leads the way for a more accurate computation of momentum fluxes. [ABSTRACT FROM AUTHOR]

Translation of the seminal 1877 paper by Ludwig Boltzmann which for the first time established the probabilistic basis of entropy. Includes a scientific commentary. [ABSTRACT FROM AUTHOR]

Crystalline zinc oxide thin films are important due to a combination of optical transparency, electrical conductivity, and piezoelectric and pyroelectric properties. These functional properties are improved with increasing perfection of the crystalline structure. In this paper, classical molecular dynamics with a reactive force field was used to simulate the atom-by-atom growth of ZnOx films on a crystalline template. Contrary to previous modeling studies, the effect of a wide range of process parameters (elemental ratio x, kinetic energy of arriving atoms, and fraction of fast atoms in the particle flux) on the film crystallinity was investigated. All the parameters were found to have a significant impact. Counterintuitively, the highest crystal quality was obtained for slightly overstoichiometric films with x > 1. The results provide a quantitative insight into the role of individual deposition parameters, and the identification of their optimum values facilitates a further improvement of the film properties. [ABSTRACT FROM AUTHOR]

As the increasing scarcity of fossil fuels and the ever‐present need to address environmental concerns are faced, the development of efficient and sustainable energy harvesting techniques gains more and more significance. The liquid–solid triboelectric nanogenerator (TENG) has emerged as a promising solution for harvesting mechanical energy in water. Although the liquid–solid contact electrification technique is studied by numerous researchers, there is still a need to enhance energy harvesting efficiency in liquid–solid TENG. This comprehensive review discusses recent advances in kinetic energy harvesting from water, focusing on the solid–solid and liquid–solid interaction mechanisms when using TENGs as an energy conversion medium. The review summarizes the recent developments in structure design and material improvements, as well as hybridization with other generators as methods of enhancing the output performance of TENG. Besides discussing advancements of TENG, the potential impact and future challenges of liquid–solid TENG are highlighted. This paper provides insight into the current state of knowledge and the future directions of research in the field of liquid–solid TENG energy harvesting. [ABSTRACT FROM AUTHOR]

For over a century, side-branch resonators have served as effective acoustic filters, yet the explanation for their sound reduction capability has varied. This paper introduces a novel theory applicable to all types of side-branch resonators from an energy perspective and explains sound reduction as a consequence of acoustic energy redistribution. Our theory posits that a standing wave inside the resonator induces air vibration at the opening, which then acts as a secondary sound source, emitting acoustic energy predominantly in the form of kinetic energy. Due to the formation process of the standing wave, the sound wave generated by the resonator undergoes a phase shift relative to the original sound wave in the main pipe. Consequently, this generated sound wave, while matching the amplitude, possesses an opposite phase compared to the original noise wave within the main pipe. This antiphase relationship results in the cancellation of sound waves when they interact post-resonator in the main pipe. Our theory, grounded in an energy perspective, is derived from the principles of standing wave vibration and energy conservation. [ABSTRACT FROM AUTHOR]

In standard quantum mechanics, the coupling between quantum systems is described by a potential interaction term in the Hamiltonian. This type of coupling is well‐rooted in nature and shapes the universe around us, from the interactions between single photons to the attractive force between atoms that forms molecules. Quantum mechanics does not forbid other kinds of interactions to take place. In this paper, a non‐standard quantum coupling between quantum systems is proposed, originated from the kinetic energy rather than the potential interaction in the Hamiltonian. Unlike the potential‐based coupling, the proposed coupling changes the fundamental structure of quantum mechanics in the form of modified uncertainty relations that are shaped by the coupling between the particles in the system. Two prototypical examples of non‐standard systems that perform such kinetic‐based coupling are presented. In the first example, it considers a particle confined in a heterostructure, such as a quantum dot, where the coupling is between the particle and dynamic walls that determine the size of the heterostructure. The second example involves a particle in a 3D heterostructure with coupling between its position axes. It then discusses several future implications of the proposed type of non‐standard coupling. [ABSTRACT FROM AUTHOR]

As is well known, magnetic fields in space are distributed very inhomogeneously. Sometimes, field distributions have forms of filaments with high magnetic field values. As many observations show, such a filamentation takes place in convective cells in the Sun and other astrophysical objects. This effect is associated with the frozenness of the magnetic field into a medium with high conductivity that leads to the compression of magnetic field lines and formation of magnetic filaments. We analytically show, based on the general analysis, that the magnetic field intensifies in the regions of downward flows in both two-dimensional and three-dimensional convective cells. These regions of the hyperbolic type in magnetic fields play the role of a specific attractor. This analysis was confirmed by numerical simulations of 2D roll-type convective cells. Without dissipation, the magnetic field grows exponentially in time and does not depend on the aspect ratio between the horizontal and vertical scales of the cell. An increase due to compression in the magnetic field of highly conductive plasma is saturated due to the natural limitation associated with dissipative effects when the maximum magnitude of a magnetic field is of the order of the root of the magnetic Reynolds number Rem. For the solar convective zone, the mean kinetic energy density exceeds the mean magnetic energy density for at least two orders of magnitude, which allows one to use the kinematic approximation of the MHD induction equation. In this paper, based on the stability analysis, we explain why downward flows influence magnetic filaments, making them flatter with orientation along the interfaces between convective cells. [ABSTRACT FROM AUTHOR]

In this paper, the evolution of second harmonic waves, whose streamwise wavenumbers are twice of the fundamental streamwise wavenumber, is studied during the oblique transition of plane Couette flow. At the initial stage of the transition, the second harmonic waves are amplified in turn by the Orr mechanism and the nonlinear convection of perturbations together with the working of perturbation pressure. At the middle and late stages, the second harmonic waves are reactivated by the instability of the mean flow in the presence of developed streamwise streaks, and their growth rates are dominated later by the nonlinear interactions of the fundamental oblique waves. When the spanwise kinetic energies of the streamwise vortices, streaks, and the fundamental oblique waves are exceeded by those of the second harmonic waves, the streak breakdown occurs, indicating that these second harmonic waves are essential for the oblique transition. [ABSTRACT FROM AUTHOR]