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A line laser with high power as the background light source for the design of a new photoelectric detection target is proposed in this paper, aiming to improve the detection ability of the traditional photoelectric detection target under low background illumination. The laser emitted pulse waveform function and the laser echo pulse response function were used to establish the mathematical model of the reflected echo power of projectile in the detection area and derive the calculation function of minimum detectable echo power in the line laser detection screen, according to information of the line laser emitted power, incident angle of projectile, duration time and detection distance of projectile passing through the line laser detection screen. Calculations and experimental results showed that the design method of line laser detection screen and calculation model of laser echo power are reasonable, and the detection ability of line laser detection screen is obviously higher than that of traditional photoelectric detection screen, especially in low background illumination; at the same time, the designed line laser detection screen was used to combine a six line laser detection screen intersection test system, based on live ammunition for shooting. The test system is stable and able to obtain the dynamic parameters of the flying projectile, verifying that the design of the line laser detection screen in new photoelectric detection target can be suitable for shooting range test applications.

Turbulence transportation across permeable interfaces is investigated using direct numerical simulation, and the connection between the turbulent surface flow and the pore flow is explored. The porous media domain is constructed with an in-line arranged circular cylinder array. The effects of Reynolds number and porosity are also investigated by comparing cases with two Reynolds numbers (Re≈3000,6000) and two porosities (φ=0.5,0.8). It was found that the change of porosity leads to the variation of flow motions near the interface region, which further affect turbulence transportation below the interface. The turbulent kinetic energy (TKE) budget shows that turbulent diffusion and pressure transportation work as energy sink and source alternatively, which suggests a possible route for turbulence transferring into porous region. Further analysis on the spectral TKE budget reveals the role of modes of different wavelengths. A major finding is that mean convection not only affects the distribution of TKE in spatial space, but also in scale space. The permeability of the wall also have an major impact on the occurrence ratio between blow and suction events as well as their corresponding flow structures, which can be related to the change of the Kármán constant of the mean velocity profile., Deutsche Forschungsgemeinschaft, Projekt DEAL, Cluster of Excellence SimTech

We develop a scheme for the computation of the full-counting statistics of transport described by Markovian master equations with an arbitrary time dependence. It is based on a hierarchy of generalized density operators, where the trace of each operator yields one cumulant. This direct relation offers a better numerical efficiency than the equivalent number-resolved master equation. The proposed method is particularly useful for conductors with an elaborate time-dependence stemming, e.g., from pulses or combinations of slow and fast parameter switching. As a test bench for the evaluation of the numerical stability, we consider time-independent problems for which the full-counting statistics can be computed by other means. As applications, we study cumulants of higher order for two time-dependent transport problems of recent interest, namely steady-state coherent transfer by adiabatic passage and Landau-Zener-St\"uckelberg-Majorana interference in an open double quantum dot., Comment: 7 pages, 5 figures

A theoretical study of the K-shell ionization of hydrogen-like ions, colliding with bare nuclei, is performed within the framework of the time-dependent Dirac equation. Special emphasis is placed on the ionization probability that is investigated as a function of impact parameter, collision energy and nuclear charge. To evaluate this probability in a wide range of collisional parameters we propose a simple analytical expression for the transition amplitude. This expression contains three fitting parameters that are determined from the numerical calculations, based on the adiabatic approximation. In contrast to previous studies, our analytical expression for the transition amplitude and ionization probability accounts for the full multipole expansion of the two-center potential and allows accurate description of nonsymmetric collisions of nuclei with different atomic numbers, $Z_1 \neq Z_2$. The calculations performed for both symmetric and asymmetric collisions indicate that the ionization probability is reduced when the difference between the atomic numbers of ions increases., 8 pages, 6 figures

Single-phase natural circulation thermosiphon loops have been attracting increased interest as they represent the prototype of passive safety systems. However, the stability properties of thermosiphon loops, which can affect and compromise their functionality, are still actively investigated. Traditionally, the stability analysis of thermosiphon loops has been simplified to one-dimensional (1D) calculations, on the argument that the flow would be monodimensional when the diameter of the pipe D is orders of magnitude smaller than the length of the loop Lt. However, at lower Lt/D ratios, rectangular thermosiphon loops show that the flow presents three-dimensional (3D) effect, which also has been confirmed by stability analyses in toroidal loops. In this paper, we performed a series of high-fidelity simulations using the spectral-element code nek5000 to investigate the stability behavior of the flow in rectangular thermosiphon loops. A wide range of Lt/D ratio from 10 to 200 has been considered, and the results show many different outcomes compared to previous 1D analytical calculations or stability theory. Moreover, we analyzed the flow in rectangular thermosiphon loops using proper orthogonal decomposition (POD), and we observed that the cases without flow reversal are characterized by swirl modes typical of bent pipes and high-frequency oscillation of the related time coefficients obtained by Galerkin projection. However, the swirl mode was not observed in cases with flow reversals, and these cases are characterized by symmetric flow field at second POD mode and the similarity of low-frequency oscillation in the projection of POD modes.

In this work, using a spherically symmetric metric, we investigate a minimally interacting holographic dark energy model within the framework of Saez-Ballester Theory. We predict that the dark energy component dominating the universe is of phantom type, which will lead the model universe to cosmic doomsday (big rip singularity). As big rip and holographic dark energy are incompatible with each other, we employ a higher dimensional scenario so that the cosmic doomsday is replaced by the de-Sitter phase. The model expands with a slow and uniform change of size during the early evolution, whereas the change becomes faster, agreeing with the present observation of the accelerated expansion. The present values of Hubble’s parameter and the dark energy EoS parameter are measured to be H = 67 and λ = − 1 . 00011 , which agree with the respective values H 0 = 67 . 36 ± 0 . 54 kms − 1 Mpc − 1 and λ = − 1 . 03 ± 0 . 03 of the most recent Planck 2018 result.

The roll angular rate is much crucial for the guidance and control of the projectile. Yet the high-speed rotation of the projectile brings severe challenges to the direct measurement of the roll angular rate. Nevertheless, the radial magnetometer signal is modulated by the high-speed rotation, thus the roll angular rate can be achieved by extracting the instantaneous frequency of the radial magnetometer signal. The objective of this study is to find out a precise instantaneous frequency extraction method to obtain an accurate roll angular rate. To reach this goal, a modified spline-kernelled chirplet transform (MSCT) algorithm is proposed in this paper. Due to the nonlinear frequency modulation characteristics of the radial magnetometer signal, the existing time-frequency analysis methods in literature cannot obtain an excellent energy concentration in the time-frequency plane, thereby leading to a terrible instantaneous frequency extraction accuracy. However, the MSCT can overcome the problem of bad energy concentration by replacing the short-time Fourier transform operator with the Chirp Z-transform operator based on the original spline-kernelled chirplet transform. The introduction of Chirp Z-transform can improve the construction accuracy of the transform kernel. Since the construction accuracy of the transform kernel determines the concentration of time-frequency distribution, the MSCT can obtain a more precise instantaneous frequency. The performance of the MSCT was evaluated by a series of numerical simulations, high-speed turntable experiments, and real flight tests. The evaluation results show that the MSCT has an excellent ability to process the nonlinear frequency modulation signal, and can accurately extract the roll angular rate for the high spinning projectiles.

An implementation of the actuator line method (ALM) is applied to a hovering helicopter rotor. This method, which is widely used for wind turbine simulations, replaces the rotor blades by momentum ...

In order to maximize the lethality and reversibility of the non-lethal laser weapons (NLLW) at the same time and thus provide a theoretical basis for the R&D of laser weapons in the future, this paper accurately analyzed the limiting biological dose of irreversible damage to human skin caused by the NLLW. Firstly, based on the burn theory in medicine and the actual tactical background, this paper redefines the evaluation criteria of the limiting laser dose of NLLW to the human body. Secondly, on the basis of anatomical knowledge, a 5-layer finite element model (FEM) of superficial skin is proposed, constructed and verified, which can accurately describe the limiting reversible damage. Based on the optimized Pennes bioheat transfer equation, the diffusion approximation theory, the modified Beer-Lambert law, the Arrhenius equation, and combined with dynamic thermophysical parameters, this paper highly restored the temperature distribution and accurately solved the necrotic tissue distribution inside the human skin irradiated by 1064 nm laser. Finally, it is concluded that the maximum human dose of the 1064 nm NLLW is 8.93 J/cm2, 8.29J/cm2, and 8.17 J/cm2 when the light spots are 5 mm, 10 mm and 15 mm, respectively, and the corresponding output power of the weapon is 46.74 W,173.72 W and 384.77 W. Simultaneously, the temperature and damage distribution in the tissue at the time of ultimate damage are discussed from the axial and radial dimensions, respectively. The conclusions and analysis methods proposed in this paper are of great guiding significance for future research in military, medical and many other related fields.

Novel numerical simulations investigating the Richtmyer-Meshkov instability (RMI) with surface tension are presented. We solve the two-phase compressible Euler equation with surface tension and interface reconstruction by a volume-of-fluid method. We validate and bridge existing theoretical models of effects of surface tension on the RMI in the linear, transitional, and nonlinear postshock growth regimes. After deriving a consistent nondimensional formulation from an existing linear incompressible theory predicting perturbation development under large surface tension, we find good agreement with theoretical prediction in the small-amplitude (linear) oscillatory regime for positive Atwood numbers, and we show that negative Atwood numbers can be accommodated by an appropriate modification to the theory. Next, we show good agreement with nonlinear theory for asymptotic interface growth in the limit of small surface tension. Finally, we use the nondimensional formulation to define a heuristic criterion which identifies the transition from the linear regime to the nonlinear regime at intermediate surface tension. These results highlight the utility of this numerical method for compressible problems featuring surface tension, and they pave the way for a broader investigation into mixed compressible/incompressible problems.

HF heating experiment, with linear power ramp from 50 to 92 dBW, was conducted to determine the HF threshold power levels for the onset of detectable plasma waves and the onset of artificial ionization inferred from HF-enhanced plasma lines (HFPLs). The threshold free-space electric field at 200-km altitude, where HFPLs were detected, is about 53 mV/m. However, the HF electric field near the reflection height is enhanced by a swelling factor ~3.76 and also conversion to a linear dipole pump mode (sqrt 2); the actual threshold field is about 281 mV/m that is consistent with theory. Artificial ionization in the lower region was detectable via UHF radar. Short wavelength upper-hybrid waves, which were excited parametrically by the HF heating wave at higher threshold, implement Doppler shifted harmonic-cyclotron resonance interaction, via finite Larmour radius effect, to effectively accelerate electrons. Monitoring the spectral power of the parametric decay instability (PDI) line in the HFPLs by radar was shown to determine the artificial ionization onset time more precisely than that by observing the start of a sharp downward trend in the altitude of the HFPLs; at this time, the HF free-space electric field slightly below 200-km altitude is about 550 mV/m. Langmuir cascade lines in the HFPLs are separated by intervals about double the ion-acoustic frequency (about 4–5 kHz) generated by the PDI. These lines, observed at lower power facilities, were not observed. The upper-hybrid OTSI and PDI excited at HighPower Active Auroral Research Program (HAARP) and the mode competition nonlinear-damping mechanism are suggested as the processes, suppressing cascade enhanced HFPLs

Current design constraints have encouraged the studies of aeroacoustics fields around compressible jet flows. The present work addresses the numerical study of subgrid scale modeling for unsteady turbulent jet flows as a preliminary step for future aeroacoustic analyses of main engine rocket plumes. An in-house large eddy simulation (LES) tool is developed in order to reproduce high fidelity results of compressible jet flows. In the present study, perfectly expanded jets are considered because the authors want to emphasize the effects of the jet mixing phenomena. The large eddy simulation formulation is written using the finite difference approach, with an explicit time integration and using a second order spatial discretization. The energy equation is carefully discretized in order to model the energy equation of the filtered Navier-Stokes formulation. The classical Smagorinsky model, the dynamic Smagorinsky model and the Vreman models are the chosen subgrid scale closures for the present work. Numerical simulations of perfectly expanded jets are performed and compared with the literature in order to validate and compare the performance of each subgrid closure in the solver., Comment: conference paper - AIAA Aviation 2016. arXiv admin note: substantial text overlap with arXiv:2212.12353, arXiv:2212.12365

We compare the computational performance of two modeling approaches for the flow of dilute cavitation bubbles in a liquid. The first approach is a deterministic model, for which bubbles are represented in a Lagrangian framework as advected features, each sampled from a distribution of equilibrium bubble sizes. The dynamic coupling to the liquid phase is modeled through local volume averaging. The second approach is stochastic; ensemble-phase averaging is used to derive mixture-averaged equations and field equations for the associated bubble properties are evolved in an Eulerian reference frame. For polydisperse mixtures, the probability density function of the equilibrium bubble radii is discretized and bubble properties are solved for each representative bin. In both cases, the equations are closed by solving Rayleigh-Plesset-like equations for the bubble dynamics as forced by the local or mixture-averaged pressure, respectively. An acoustically excited dilute bubble screen is used as a case study for comparisons. We show that observables of ensemble- and volume-averaged simulations match closely and that their convergence is first order under grid refinement. Guidelines are established for phase-averaged simulations by comparing the computational costs of methods. The primary costs are shown to be associated with stochastic closure; polydisperse ensemble-averaging requires many samples of the underlying PDF and volume-averaging requires repeated, randomized simulations to accurately represent a homogeneous bubble population. The relative sensitivities of these costs to spatial resolution and bubble void fraction are presented.

We investigate the long-range, two-body interactions between rubidium and potassium atoms in highly excited ($n=70$) Rydberg states. After establishing properly symmetrized asymptotic basis states, we diagonalize an interaction Hamiltonian consisting of the standard Coulombic potential expansion and atomic fine structure to calculate electronic potential energy curves. We find that when both atoms are excited to either the $70s$ state or the $70p$ state, both the $\Omega=0+$ symmetry interactions and the $\Omega=0-$ symmetry interactions demonstrate a deep potential well capable of supporting many bound levels; the size of the corresponding dimer states are on the order of 2.25 $\mu$m. We estabish $n$-scaling relations for the equilibrium separation $R_e$ and the dissociation energy $D_e$ and find these relations to be consistent with similar calculations involving the homonuclear interactions between rubidium and cesium. We discuss the specific effects of $\ell$-mixing and the exact composition of the calculated potential well \textit{via} the expansion coefficients of the asymptotic basis states. Finally, we apply a Landau-Zener treatment to show that the dimer states are stable with respect to predissociation., Comment: 8 pages, 4 figures, 4 tables

We theoretically study the influence of laser polarization in inelastic scattering of electrons by hydrogen atoms in the presence of a circularly polarized laser field in the domain of field strengths below $10^{7}$ V/cm and high projectile energies. A semi-perturbative approach is used in which the interaction of the projectile electrons with the laser field is described by Gordon-Volkov wave functions, while the interaction of the hydrogen atom with the laser field is described by first-order time-dependent perturbation theory. A \textit{closed analytical solution} is derived in laser-assisted inelastic electron-hydrogen scattering for the $1s \to nl$ excitation cross section which is valid for both circular and linear polarizations. For the excitation of the $n=2$ levels simple analytical expressions of differential cross section are derived for laser-assisted inelastic scattering in the perturbative domain, and the differential cross sections by the circularly and linearly polarized laser fields and their ratios for one- and two-photon absorption are calculated as a function of the scattering angle. Detailed numerical results for the angular dependence and the resonance structure of the differential cross sections is discussed for the $1s \to 4l$ excitations of hydrogen in a circularly polarized laser field., Comment: arXiv admin note: text overlap with arXiv:1509.08695

Wind energy technology is based on the ability to capture the energy contained in air motion. Wind power quantifies the rate of this kinetic energy extraction. Wind power is also the rate of kinetic energy flow carried by the moving air. Because the motion is both the source of the energy and the means of its transport, the efficiency of wind power extraction is a balance of slowing down the wind while maintaining a sufficient flow. This chapter quantifies these fundamental concepts and discusses the nature of wind.

In recent years considerable interest has been aroused to the problem of high-temperature heat conduction of solid-state body subject to strong high-frequency electronic and laser beams [1].

Using the nonclassical symmetry of nonlinear reaction–diffusion equations, some exact multi-dimensional time-dependent solutions are constructed for a fourth-order Allen–Cahn–Hilliard equation. This models a phase field that gives a phenomenological description of a two-phase system near critical temperature. Solutions are given for the changing phase of cylindrical or spherical inclusion, allowing for a “mushy” zone with a mixed state that is controlled by imposing a pure state at the boundary. The diffusion coefficients for transport of one phase through the mixture depend on the phase field value, since the physical structure of the mixture depends on the relative proportions of the two phases. A source term promotes stability of both of the pure phases but this tendency may be controlled or even reversed through the boundary conditions.

We develop the idea that a natural link between Boltzmann schemes and finite volumes exists naturally: the conserved mass and momentum during the collision phase of the Boltzmann scheme induces general expressions for mass and momentum fluxes. We treat a unidimensional case and focus our development in two dimensions on possible flux boundary conditions. Several test cases show that a high level of accuracy can be achieved with this scheme.

In this paper, we study random features manifested in components of energy eigenfunctions of quantum chaotic systems, given in the basis of unperturbed, integrable systems. Based on semiclassical analysis, particularly on Berry's conjecture, it is shown that the components in classically allowed regions can be regarded as Gaussian random numbers in certain sense, when appropriately rescaled with respect to the average shape of the eigenfunctions. This suggests that, when a perturbed system changes from integrable to chaotic, deviation of the distribution of rescaled components in classically allowed regions from the Gaussian distribution may be employed as a measure for the ``distance'' to quantum chaos. Numerical simulations performed in the LMG model and the Dicke model show that this deviation coincides with the deviation of the nearest-level-spacing distribution from the prediction of random-matrix theory. Similar numerical results are also obtained in two models without classical counterpart., Comment: 11 pages, 13 figures

The elementary optical excitations of a two-dimensional electron or hole system have been identified as exciton-Fermi-polarons. Nevertheless, the connection between the bound state of an exciton and an electron, termed trion, and exciton–polarons is subject of ongoing debate. Here, we use an analogy to the Tavis–Cummings model of quantum optics to show that an exciton–polaron can be understood as a hybrid quasiparticle—a coherent superposition of a bare exciton in an unperturbed Fermi sea and a bright collective excitation of many trions. The analogy is valid to the extent that the Chevy Ansatz provides a good description of dynamical screening of excitons and provided the Fermi energy is much smaller than the trion binding energy. We anticipate our results to bring new insight that could help to explain the striking differences between absorption and emission spectra of two-dimensional semiconductors, Comptes Rendus. Physique, 22 (S4), ISSN:1631-0705, ISSN:1878-1535

The free energy principle (FEP) states that any dynamical system can be interpreted as performing Bayesian inference upon its surrounding environment. Although, in theory, the FEP applies to a wide variety of systems, there has been almost no direct exploration or demonstration of the principle in concrete systems. In this work, we examine in depth the assumptions required to derive the FEP in the simplest possible set of systems – weakly-coupled non-equilibrium linear stochastic systems. Specifically, we explore (i) how general the requirements imposed on the statistical structure of a system are and (ii) how informative the FEP is about the behaviour of such systems. We discover that two requirements of the FEP – the Markov blanket condition (i.e. a statistical boundary precluding direct coupling between internal and external states) and stringent restrictions on its solenoidal flows (i.e. tendencies driving a system out of equilibrium) – are only valid for a very narrow space of parameters. Suitable systems require an absence of asymmetries in perception-action loops that are highly unusual for living systems interacting with an environment, which are the kind of systems the FEP explicitly sets out to model. More importantly, we observe that a mathematically central step in the argument, connecting the behaviour of a system to variational inference, relies on an implicit equivalence between the dynamics of the average states of a system with the average of the dynamics of those states. This equivalence does not hold in general even for linear systems, since it requires an effective decoupling from the system's history of interactions. These observations are critical for evaluating the generality and applicability of the FEP and indicate the existence of significant problems of the theory in its current form. These issues make the FEP, as it stands, not straightforwardly applicable to the simple linear systems studied here and suggests that more development is needed before the theory could be applied to the kind of complex systems which describe living and cognitive processes.

In this study, the lock-in phenomenon of Tip Clearance Flow (TCF) instabilities and their relationship to blade vibration are investigated numerically on an axial transonic rotor with a large tip clearance. The capabilities of simulating instability flow and lock-in phenomenon are verified on a transonic rotor and a NACA0012 airfoil by comparing with the test data, respectively. The lock-in phenomenon is first numerically confirmed that may occur to TCF instabilities when its frequency is close to the blade vibration frequency. The lock-in region becomes wider with the vibration amplitude increasing, and it is also affected by modal shapes. For the rotor at the simulation conditions in this study, the bending mode results in a wider lock-in region than the torsional mode. In the lock-in region, the phase difference between the Tip Clearance Vortex (TCV) and the blade vibration changes with the flow condition and the frequency ratio of the blade vibration and the TCV instabilities. The frequency of the TCV instabilities reduces with the mass flow decreasing. Therefore, reducing mass flow and increasing frequency ratio have similar effects on the TCV phase, which causes a significant variation on the unsteady pressure amplitude in the blade tip area. Thus, the aerodynamic damping changes significantly with the TCV phase. The aerodynamic damping displays a nonlinear relationship with the vibration amplitude, and it changes from negative to positive with the vibration amplitude increasing at the same frequency ratio. The negative damping is mainly provided by the tip area of the blade. For unlocked conditions, the period of the TCF instabilities fluctuates over time, and it cannot be directly separated by their frequency features. Inter Blade Phase Angle (IBPA) also has an important influence on the feature of the TCV instabilities. The occurrence of frequency lock-in also requires “appropriate” IBPA. For the examined working conditions, the frequency lock-in occurs under 0 ND (Nodal Diameter), but not under 8 ND. However, no matter 0 ND or 8 ND, the phase of TCV always locks onto the IBPA at the examined conditions.

Experimental investigations of two interacting spheres were carried out in a Mach 4 flow with a static pressure of 2.666 Pa. This study was performed in the MARHy wind tunnel, an adjustable supersonic or hypersonic low-density facility. The main purpose is to estimate how the interactions between spherical debris modify the aerodynamic forces during their atmospheric entry. Indeed, around 80 km, altitude experimentally reproduced thanks to MARHy flow conditions, most debris fragment. The multiple debris, resulting from fragmentation, interact with each other’s, which may impact their trajectory. The purpose of this work is to analyze the behavior of a moving sphere placed in the wake of another one. The moving sphere is suspended with two thin wires, so it can almost freely move in the flow direction and physically respond to the acting flow forces of the wake of the first one. Aerodynamic forces are then calculated from the sphere angle deflection. The qualitative analysis of the experimental results will be discriminated first with respect to the trajectory of the second sphere, and secondly with respect to the evolution of the aerodynamic forces according to the sphere.

The deviations of trajectory and attitude angle for internal store separation are evaluated by two wind tunnel test methods. One is the Freedrop Test (FDT), which is known as unsteady and time-dependent method of scaled model. The other is the Captive Trajectory System (CTS) test, which is usually regarded as a quasi-steady and time-averaged test technology. The result shows that there is a streamwise adverse pressure gradient on the cavity resulting in a nose-up pitching moment coefficient (>0) acting on the store model. When the initial pitch angular velocity is 0, the store exits the shear-layer with a nose-up pitch attitude causing the store to climb back towards and collide with the aircraft. However, the store passes through the shear-layer into the freestream with a nose-down pitch, which causes a successful separation event when the initial pitch angular velocity

Partial surge is a type of instability inception in transonic compressors and occurs in the form of axisymmetric low-frequency disturbances localized in the hub region. Previous studies illustrate that the frequency of partial surge is set by the Helmholtz frequency of the entire system, which motivates to propose a hypothesis that the system response performs an important role in the formation of partial surge. For further verification, a series of experiments are conducted to explore the link between the propagating of the partial surge and the system feedback in this study. In the first case, an additional test point is set on the wall of the plenum to detect the system response. Combining the flow behaviors inside the plenum with the disturbances in the rotor tip and stator hub/tip regions, the effects of the system feedback on the occurrence of the continuous disturbances and the rotating stall cells are illustrated. In the second case, a screen is mounted at the compressor outlet to prevent positive feedback from the plenum. The experimental results demonstrate that in the absence of system feedback, it is the occurrence of spike-type stall inception that leads to the flow instability instead of that of partial surge. In addition, three flow phenomena in the second case are discussed, including the occurrence of the single pulse, the unstable process during the stall evolution and the switch of instability inception.

In this paper, a passive muzzle arc control device (PMACD) of the augmented railguns is studied. By discussing its performance at different numbers of extra rails, a parameter optimization model is proposed. Through the calculation model, it is found that the PMACD works well in the simple railgun, which refers to the gun that there is only one pair of rails in the inner bore. The PMACD may decrease the simple railgun’s armature peak current and muzzle arc, but affect its muzzle velocity not much. However, in the augmented railguns it has different characteristics. If the parameters of the PMACD are not selected suitable. It may increase the armature peak current and muzzle arc, but greatly decrease the velocity. The reason for this problem is that the extra rails generate a strong magnetic field in front of the armature, which induces a large current to change the armature current. It is also found that when the resistance and inductance parameters of the PMACD satisfy with the optimization formula, the PMACD can also play a good role in arc suppression in the augmented railguns. Experiments of an augmented railgun with a stainless steel PMACD are carried out to verify this optimization method. Results show that the muzzle arc is obviously controlled. This work may provide a reference for the design of the muzzle arc control device.

Hemispherical Resonator Gyroscope (HRG) is a classical high precision Coriolis Vibration Gyroscope (CVG), which performs attitude estimation of carrier by detecting the precession of standing wave of resonator, thus, the drift of standing wave of resonator has a great influence on the output accuracy of gyroscope, where the quality factor non-uniformity of resonator is one of main error sources. Ring electrode is a classical excitation structure of HRG because the standing wave can precess freely under its excitation, which makes the gyroscope have more accurate scale factor, larger measurement range and better dynamic characteristics. In this paper, the equations of motion of an ideal resonator excited by a ring electrode are derived by the elastic thin shell theory and Lagrange mechanical principle, then the corresponding equivalent mechanical model is established. According to the “average method”, it can be seen that the ideal resonator excited by the ring electrode works in integral mode, and any position in the circumferential direction of resonator can be a working point, which means that the quality factor non-uniformity has a great effect on the drift of standing wave. Therefore, the equations of motion of resonator with quality factor non-uniformity under the ring electrode excitation are deduced by the equivalent mechanical model, and the drift model of standing wave is established by the “average method”, it can be found that both the amplitude of quality factor non-uniformity and angle between the “inherent damping axis” and antinode axis of standing wave can affect the drift rate of standing wave. Moreover, the drift model indicates that if the input angular rate does not reach the threshold, the precession angular rate of standing wave will appear “self-locking” phenomenon, that is, the gyroscope will lose the integral effect.

The aerodynamic design and fuel burn performance of a Mach-0.78 strut-braced-wing regional jet is investigated through aerodynamic shape optimization based on the Reynolds-averaged Navier–Stokes eq...

The underlying study investigates single valued neutrosophic entropy based adaptive sensitive frequency band selection for variational mode decomposition (VMD) for the purpose of identifying defective components in an axial pump. The proposed methodology is applied in the following steps. First, VMD is applied for decomposing vibration signals into various frequency bands, called as modes. After computing energy of each VMD, the lower (minimum) and upper (maximum) bounds from these energy readings are extracted for defect conditions, such as outer race, inner race, worn piston, faulty cylinder and valve plate, and blocked hole of the piston. Thereafter, energy interval ranges are obtained and further converted into the form of single valued neutrosophic sets (SVNSs). Then, the proposed neutrosophic entropy measure is deployed for quantifying the non-linear connection between each bearing defect conditions and various frequency bands. The mode having maximum neutrosophic entropy value is designated to the “most sensitive” frequency band. Thereafter, envelope demodulation is applied to the most sensitive selected frequency band for finding defective components. The proposed neutrosophic entropy and VMD based methodology is effective in providing a better insight for selecting suitable frequency band for carrying out envelope demodulation in comparison to existing methods.

In this report, we discuss a possible way to derive the Pauli equation of a spin − 1 / 2 particle based on Budiyono-Rohrlich ontic extension and epistemic restriction axioms of a statistical model of quantum mechanics. Applying the conservation of energy and probability continuity equation, we show that for a pure quantum mechanical particle spin, the corresponding equation can be reconstructed by assuming the existence of separable probability distribution functions of spin. The associated particle spin is still considered as a pure quantum phenomenon which has no classical counterpart. We also discuss the possibility of constructing a bipartite Pauli equation of nonlocal interacting two spin − 1 / 2 particles. We examine the corresponding necessary conditions for the separability of the Bell-like-states and Werner-like-states through the Peres–Horodecki positive partial transpose criterion.

The Orphée reactor, located at the CEA Saclay near Paris, that was used to produce neutrons for scattering experiments over the past four decades has been stopped definitively in October 2019. The Laboratoire Léon Brillouin, the laboratory that operated the diffractometers and spectrometers around the Orphée reactor, is studying the possibility to build a compact Neutron Source to keep offering neutron beams to the French neutron scattering community. The efficient use of a pulsed source requires neutron instrumentation using Time-of-Flight (TOF) principles.The transfer of NSE spectrometer from continuous to pulse source requires the change of monochromatic neutron beam spin-echo technique to the TOF one. Here we report a successful attempt of adaptation of the Neutron Resonance Spin-Echo spectrometer MUSES (G1bis) to a pulsed source with a frequency of 20 Hz and a duty cycle of roughly 5 %.

Quantum spin liquids, exotic phases of matter with topological order, have been a major focus of explorations in physical science for the past several decades. Such phases feature long-range quantum entanglement that can potentially be exploited to realize robust quantum computation. We use a 219-atom programmable quantum simulator to probe quantum spin liquid states. In our approach, arrays of atoms are placed on the links of a kagome lattice and evolution under Rydberg blockade creates frustrated quantum states with no local order. The onset of a quantum spin liquid phase of the paradigmatic toric code type is detected by evaluating topological string operators that provide direct signatures of topological order and quantum correlations. Its properties are further revealed by using an atom array with nontrivial topology, representing a first step towards topological encoding. Our observations enable the controlled experimental exploration of topological quantum matter and protected quantum information processing.

This paper has been devoted to exact calculation of the natural frequencies for out-of-plane free vibration of three-layer symmetric sandwich beams by using dynamic stiffness matrix method. Governing differential equations of motion have been derived using Euler-Bernoulli beam theory and St. Venant’s torsion theory, so that the effects of shear deformation in the face layers and rotary inertia are not taken into account and the cross-section is allowed to warp without restraint. Wittrick-Williams algorithm has been used to calculate the natural frequencies. Accuracy and ability of the dynamic stiffness matrix method have been illustrated in form of several examples. Results are verified through comparison with the natural frequencies obtained from ABAQUS software. Full independence of out-of-plane bending and torsional modes of vibration for three-layer symmetric sandwich beams has been proven.

In a fuel-efficient extended formation flight of commercial airplanes, the aerodynamic benefits depend on one’s ability to surf wake vortices. This paper presents a wake vortex detection scheme bas...

The available literature on heat pumps shows that thermodynamic models lead to minimization of energy expense, very often in endoreversible configurations, sometimes irreversibles. The present paper purpose is to revisit and complete the heat pumps irreversible model by adding the coupling constraint between the cycle and the thermal reservoirs assumed to be thermostats. This constraint is in fact an essential condition for the cycle existence, practically always ignored. This modeling leads to a set of new results, including new expressions for the COP corresponding to minimum energy expense. The fundamental consequences of this new approach also show the limits of the equipartition theorem of heat exchange area, as well as of the entropy minimization method.

Here, we use the modified Kudryashov’s algorithm and addendum to Kudryashov’s technique to obtain new optical solitons of the Ginsburg–Landau fractional complex of non-linearity (CGLE) laws in Kerr, which demonstrate various phenomena in physics such as non-linear waves, the transformation of the secondary phase, superconductivity, surfaces, liquid crystals, and field-theory strings. Dark, bright, singular solitons and combo bright-singular solitons are retrieved. The modified Kudryashov’s algorithm provides dark, singular solitons, and combo bright-singular solitons, although the addendum to Kudryashov’s technique ensures bright and singular solitons. These solutions are practiced for three optional definitions of derivative viz. conformable derivative, beta derivative, and M-truncated. Also shown are graphic representations of the solutions obtained.

We have explored the non-locality of two qubits interacting time-dependently with a non-degenerate parametric amplifier cavity fields in the presence of the Stark shift interaction term. The time-dependent two-qubit reduced density matrix is calculated numerically when the cavity fields are initially in two entangled coherent states. We investigate the non-locality via local Fisher information and negativity. It is shown that, the generated non-locality depends on the time dependent two-qubit location, the Stark shift interaction, the difference between the mean photon numbers of the two cavity fields as well as the initial intensity coherent fields. The agreement of the generated correlations presented by the local Fisher information and the negativity depends on the physical parameters. The Stark shift non-linearity and the difference between the mean photon numbers leads to reducing the generated correlations. The local Fisher information is more robust against the Stark shift interaction than the negativity .

In quantum fluids, the quantisation of circulation forbids the diffusion of a vortex swirling flow seen in classical viscous fluids. Yet, a quantum vortex accelerating in a superfluid may lose its energy into acoustic radiation, in a similar way an electric charge decelerates upon emitting photons. The dissipation of vortex energy underlies central problems in quantum hydrodynamics, such as the decay of quantum turbulence, highly relevant to systems as varied as neutron stars, superfluid helium and atomic condensates. A deep understanding of the elementary mechanisms behind irreversible vortex dynamics has been a goal for decades, but it is complicated by the shortage of conclusive experimental signatures. Here, we address this challenge by realising a programmable quantum vortex collider in a planar, homogeneous atomic Fermi superfluid with tunable inter-particle interactions. We create on-demand vortex configurations and monitor their evolution, taking advantage of the accessible time and length scales of our ultracold Fermi gas. Engineering collisions within and between vortex-antivortex pairs allows us to decouple relaxation of the vortex energy due to sound emission and interactions with normal fluid, i.e. mutual friction. We directly visualise how the annihilation of vortex dipoles radiates a sound pulse in the superfluid. Further, our few-vortex experiments extending across different superfluid regimes suggest that fermionic quasiparticles localised inside the vortex core contribute significantly to dissipation, opening the route to exploring new pathways for quantum turbulence decay, vortex by vortex., Comment: 7+9 pages, 4+7 figures

Understanding and control of wake vortices past a circular cylinder is a cardinal problem of interest to ocean engineering. The wake formation and vortex shedding behind a variety of ocean structures such as spars, are subjected to fatigue failure limiting their life span. The additional influences due to ocean waves and currents further exacerbate these effects. In the present study, flow past an isolated circular cylindrical structure subjected to an oscillatory upstream are numerically investigated. These studies involve high resolution simulations over the low Reynolds number range (100-200). Although the practical range of interest is in high Reynolds number range of 10 3 - 10 5 , the flow physics and a number of qualitative and quantitative aspects are similar to the low Reynolds number flows. In the high Reynolds number range, statistical averaging tools in conjunction with suitable closure models would be necessary. The control of wake vortices is achieved with the aid of two small rotors located in the aft of the main cylinder. A control algorithm was coupled to determine the quantum of actuation to the rotating elements. Although control of wake vortices was observed for harmonic in-let forcing, residual vortical structures were found to persist at higher amplitudes of oscillation. To study the efficacy of this control, numerical simulations were further extended, when the circular cylinder was flexibly mounted. The control of flow induced vibrations was observed to be reasonably effective in controlling the wake generated behind the main cylinder due to oscillatory upstream.

This paper attempts to explore the general rotatory 3D motion of a magnetic heavy solid body around one fixed point under the impact of a gyrostatic moment when the body awarded initially high angular velocity about one of its inertia principal axes. The asymptotic technique of Krylov-Bogoliubov-Mitropolski and its adjustment are applied to achieve new asymptotic periodic solutions of the controlling equations of motion. Discussion of these solutions is presented taking into consideration their graphs representations. The graphical depictions of such solutions and their corresponding phase planes are plotted to give an induction about its behaviour during the interval time of motion and to reveal the good effect of the different applied forces and moments on the body's motion. The application of the achieved results of the present work can be widely found in gyroscopic devices especially that used inertia reference systems like in satellites, airplanes, and missiles. Moreover, for devices that are responsible for the stability of motion for these applications.

The research article is the analysis of wave propagation in an initially stressed micropolar fractional-order derivative thermoelastic diffusion medium with voids. The governing equations in the context of generalized fractional-order derivative thermo-elasticity are formulated and the velocity equations are obtained. The plane wave solution of these equations indicates the existence of six plane waves, namely coupled longitudinal displacement ( c L ), coupled thermal ( c T ), coupled mass diffusion ( c M D ), coupled longitudinal void volume fraction ( c V ), coupled transverse displacement ( c T D ), and coupled transverse micro-rotational ( c T M ) waves. The sets of coupled waves ( c L ), ( c T ), ( c M D ) and ( c V ) are found to be dispersive, attenuating and influenced by the presence of thermal, diffusion and voids parameters in the medium. The speeds of coupled transverse displacement ( c T D ), and coupled transverse micro-rotational ( c T M ) waves are not affected by thermal, diffusion and void parameters. The speeds of the plane waves, c L , c T , c M D , and c V are computed for a particular material and plotted against the thermal parameter, frequency, initial stress, diffusion and void parameters.

We present regime maps for subsonic flow in dense gas-particle systems, which demarcate regions of compressible and (effectively) incompressible flow. These maps should aid researchers and industrialists in selecting the appropriate modeling approach, as well as in verifying numerical solvers. Demonstrating compressibility at Mach numbers lower than 0.3, we show that this commonly used criterion is insufficient for flows in porous media. For M

The present study focuses on the mitigation of shock wave using novel geometric passages in the flow field. The strategy is to produce multiple shock reflections and diffractions in the passage with minimum flow obstruction, which in turn is expected to reduce the shock wave strength at the target location. In the present study the interaction of a plane shock front (generated from a shock tube) with various geometric designs such as, 1) zig-zag geometric passage, 2) staggered cylindrical obstructions and 3) zig-zag passage with cylindrical obstructions have been investigated using computational technique. It is seen from the numerical simulation that, among the various designs, the maximum shock attenuation is produced by the zig-zag passage with cylindrical obstructions which is then followed by zig-zag passage and staggered cylindrical obstructions. A comprehensive investigation on the shock wave reflection and diffraction phenomena happening in the proposed complex passages have also been carried out. In the new zig-zag design, the initial shock wave undergoes shock wave reflection and diffraction process which swaps alternatively as the shock front moves from one turn to the other turn. This cyclic shock reflection and diffraction process helps in diffusing the shock wave energy with practically no obstruction to the flow field. It is found that by combining the shock attenuation ability of zig-zag passage (using shock reflection and diffraction) with the shock attenuation ability of cylindrical blocks (by flow obstruction), a drastic attenuation in shock strength can be achieved with moderate level of flow blocking.

In this paper, we discuss the solution of the magneto hydrodynamics (MHD) thermal boundary layer flow of Casson liquid over a penetrable extending wedge with ohmic heating and convective boundary condition (BC). Important applications of such flows and condition include the MHD pump, radiation therapy, MHD generator, soil mechanics, melt spinning process, thermal insulation and many others. Practical applications of convective BC are often encountered in laser damage or laser processing. The problem is non dimensionalized and computational solutions are achieved for the governing nonlinear coupled ordinary differential equations (PDEs) by using homotopy analysis method (HAM) and influence of various emerging parameters on momentum and temperature field are examined. A table containing computational data for the wall shear stress f ′ ′ ( 0 ) and local Nusselt - θ ′ ( 0 ) number is also provided. Major findings/objectives of the present study are: an increasing in Casson fluid parameter δ decreases velocity when wedge stretches faster than free stream velocity for R = 2 . However, velocity increases for R = 0.1 case. Temperature velocity decreases for R = 2 or R = 0.1 cases for δ escalations. Enhancing B i for convective heat transfer increases the momentum and thermal boundary layer thickness in the presence of suction C. Computational outcomes for velocity, drag force, temperature velocity and heat transfer rate are discussed through tables numerically. Results are verified with varied choices of suction parameter C. It is noted that the convective parameter magnified the heat transfer rate.

The present paper theoretically accords a biomechanical model with a brief biological and mathematical description of the growing embryo transport in the human fallopian tube. This model incorporates transport mechanisms that involve the pressure gradient at the ampullar region entrance, peristaltic contractions of smooth muscle cells and swaying motions of ciliary cells. Shear rate dependent viscoelastic fluid characterizes the nature of growing embryo and secreted fluid. The pressure gradient at the ampullar region entrance ξ , metachronal wave parameter ∊ , amplitude ratio ϕ , the ratio of shear viscosity at infinity shear rate to shear viscosity at zero shear rate μ ∞ / 0 and Weissenberg number We emerged as flow control parameters. The assessment showed that the fluid model parameters ( μ ∞ / 0 and We) have opposite effects on appropriate residue time, boluses size and local flow behaviour. Progesterone ( P 4 ) and estradiol ( E 2 ), prostaglandin E 2 ( PGE 2 ) and prostaglandin F 2 α ( PGF 2 α ) constraint the fluid motion by controlling the ξ , secretion of the fluid through the goblet cells and amplitudes of both the sinusoidal and the metachronal waves. Furthermore, a comparison between the current results and available literature is made. The relevance of the obtained results with the growing embryo transport in the human fallopian tube is also explored.

Two-body point absorbers are useful for wave energy conversion in high energetic and high wave period sea locations. Analysis and simulation show that the two-body point absorbers have high efficiencies which makes them a potential candidate to promote wave energy harvesting technology towards commercialization and implementation. The submerged body of the two-body point absorbers has a large effect on their performance, hence the question arises: which geometric shape of the submerged body will lead to the best performance of the two-body wave energy harvesters? This paper presents a comprehensive study that analyses the different shapes of the submerged bodies based on the numerical wave tank simulated viscous drag coefficient and hydrodynamic property parameters of the oscillating device. A set of transient and three-dimensional computational fluid dynamic simulations of a numerical wave tank were carried out in Ansys Fluent to determine the viscous drag coefficients of the different submerged body shapes. And then the boundary element hydrodynamic simulation and linear dynamic frequency-domain modeling have been applied to identify the optimized PTO damping. Finally, non-linear time-domain modeling has been applied with the identified viscous damping drag coefficient and PTO damping coefficients to predict and compare the power output performance of different large-scale devices with different shapes of submerged bodies. It is found that each submerged body shape is suitable for a different range of wave frequencies, as one must establish a balance between the hydrodynamic properties and the viscous drag of the submerged body based on the sea location. It is also found that the typical viscous drag coefficient values used in the past studies underestimate the drag coefficient, and the linearized model widely adopted in frequency domain models is non-accurate for the devices with large viscous drag forces.

Interaction potentials were obtained by the density functional theory (DFT) and nuclear stopping powers (NSP) were calculated for 48 systems in the energy range above 10 eV. It was shown that NSP calculated using the DFT potentials in the collision energy range of 10–1000 eV give more accurate values comparing with the SRIM data, obtained data differs from SRIM data by 15–70%. The presence of a potential well leads to the emergence of an additional NSP peak at low energies. Comparison of classical calculations of the transport cross section with semiclassical ones showed their identity at energies of up to 1 eV. The criterion for the applicability of classical calculations for the transport cross section and NSP cross sections is the condition l>1 (l is the angular momentum). The importance of including multichannel scattering in NSP calculations was demonstrated, for the case of energies below 20 eV.

In this paper, the new travelling wave solutions of the (2+1)-dimensional extended Calogero-Bogoyavlenskii-Schiff (ECBS) equation are investigated. The main aim of this work is to find the new exact solutions with the aid of relatively new ( G ′ G ′ + G + A ) -expansion method. Moreover, the physical interpretation of the nonlinear phenomena is reported through the exact solutions, which indicate the efficacy of the proposed method. Furthermore, the recovered solutions are periodic and solitary wave solutions which are presented graphically.

Imaging is central to gaining microscopic insight into physical systems, and new microscopy methods have always led to the discovery of new phenomena and a deeper understanding of them. Ultracold atoms in optical lattices provide a quantum simulation platform, featuring a variety of advanced detection tools including direct optical imaging while pinning the atoms in the lattice1,2. However, this approach suffers from the diffraction limit, high optical density and small depth of focus, limiting it to two-dimensional (2D) systems. Here we introduce an imaging approach where matter wave optics magnifies the density distribution before optical imaging, allowing 2D sub-lattice-spacing resolution in three-dimensional (3D) systems. By combining the site-resolved imaging with magnetic resonance techniques for local addressing of individual lattice sites, we demonstrate full accessibility to 2D local information and manipulation in 3D systems. We employ the high-resolution images for precision thermodynamics of Bose–Einstein condensates in optical lattices as well as studies of thermalization dynamics driven by thermal hopping. The sub-lattice resolution is demonstrated via quench dynamics within the lattice sites. The method opens the path for spatially resolved studies of new quantum many-body regimes, including exotic lattice geometries or sub-wavelength lattices3–6, and paves the way for single-atom-resolved imaging of atomic species, where efficient laser cooling or deep optical traps are not available, but which substantially enrich the toolbox of quantum simulation of many-body systems., Existing techniques for high-resolution imaging of trapped quantum gases are limited to two-dimensional systems, but the approach described here works in three dimensions by magnifying the quantum gas with matter wave optics.