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We consider the effect that an upstream cylinder has on the effective inertial collection efficiency of a downstream cylinder. We consider an initially uniform distribution of particles moving past a cylindrical fiber in a potential crossflow and numerically calculate the resulting particle distribution far downstream of the fiber using finite differences. We then investigate the effect that the downstream distribution of particles has on the effective inertial collision efficiency of a downstream test cylinder oriented parallel to the first. We show that the effective collision efficiency of the test cylinder depends on its relative offset in the transverse direction (normal to the flow) with respect to the upstream cylinder. For relatively small offsets there is complete shielding, and no particles collide with the test cylinder. As the offset increases, a growing effective collision efficiency is observed leading to a significant enhancement relative to the collision efficiency of an isolated cylinder for intermediate offsets and Stokes numbers close to unity. Importantly, we observe relative gains in effective collision efficiency above 100% for a range of Stokes number and offset values. For larger offsets and Stokes numbers, the effect of the upstream cylinder on the effective collision efficiency of the test cylinder decreases and eventually becomes negligible. Detailed results are provided for Stokes drag acting on the particles and we also show that a non-linear drag has negligible effect on the observed trends for the conditions relevant to filtration systems. These results suggest that the arrangement of fibers has a substantial effect on inertial particle impaction even when neighboring fibers do not alter the flow field around each individual collector. Moreover, periodic arrangements with specific orientations with respect of the flow could lead to a significant enhancement of the inertial collision of particles on an array of collectors, thus contributing towards a better filtration performance.

A counter-current jet (CCJ) is significantly different from a classical jump – it is like a classical jump with a reverse surface jet layer above it. A series of experiments, with the jet's Froude number in the range 4–10, was conducted to investigate the velocity distribution characteristics of CCJs. It was found, compared with a classical jump, the CCJ velocity distribution was more even and the decay of the maximum velocity was more efficient. It was beneficial to the energy dissipation and the deceleration of a high-speed flow. The variations of velocity with depth were opposite in the upper and lower parts of the zero-velocity line, resulting in relatively large fluid internal friction near the zero-velocity line. The internal friction between the surface jet layer and the lower fluid also increased the energy dissipation rate. A counter-current energy dissipator was found to achieve a good energy dissipation effect without auxiliary energy dissipators, which could be beneficial to engineering applications.

An algorithm for solving exciton Schrodinger equation in an arbitrary 2D multiple quantum well structure under applied electric field is proposed, allowing one to model both the absorption and refraction spectra consistently and efficiently. It gives much better quantitative results than variational approximation, while being faster than more advanced methods. The algorithm is implemented using R language and tested by comparing to other published results. Possible improvements are discussed.

This paper investigates suppressing the pitching oscillation of a NACA 0012 airfoil at a Reynolds number of [Formula: see text] by using phase-shifted trailing-edge morphing. The latter considering geometric nonlinearity is simulated numerically based on spatiotemporal polynomial surface fitting. Flowfield results and aerodynamic forces are obtained by solving the unsteady Reynolds-averaged Navier–Stokes equations accompanied by a low-Reynolds-number modified-shear-stress transport model. Dynamic meshing combining a sliding mesh and Laplacian diffusion is developed to deal with the deformation of the computational grid due to the large-amplitude coupled pitching and morphing motion of the airfoil. The airfoil is subjected to stall-flutter analysis from an energy perspective by calculating the energy extracted by the airfoil from the freestream in an oscillation cycle. The flow control mechanism of the phase-offset trailing-edge morphing is analyzed in terms of the pressure distribution and moment contribution. The results suggest that trailing-edge motion with a phase of [Formula: see text] reduces the energy extraction by more than 300% and could be effective for suppressing the stall-flutter limit-cycle oscillation amplitude in specific ranges of amplitude and frequency.

We consider a discrete system of $n$ simple indistinguishable devices, called \emph{agents}, forming a \emph{connected} shape $S_I$ on a two-dimensional square grid. Agents are equipped with a linear-strength mechanism, called a \emph{line move}, by which an agent can push a whole line of consecutive agents in one of the four directions in a single time-step. We study the problem of transforming an initial shape $S_I$ into a given target shape $S_F$ via a finite sequence of line moves in a distributed model, where each agent can observe the states of nearby agents in a Moore neighbourhood. Our main contribution is the first distributed connectivity-preserving transformation that exploits line moves within a total of $O(n \log_2 n)$ moves, which is asymptotically equivalent to that of the best-known centralised transformations. The algorithm solves the \emph{line formation problem} that allows agents to form a final straight line $S_L$, starting from any shape $ S_I $, whose \emph{associated graph} contains a Hamiltonian path., Comment: 31 pages, 18 figures

This article investigates the joint effects of connection weight and time delay on pattern formation for a delayed reaction-diffusion BAM neural network (RDBAMNN) with Neumann boundary conditions by using the (k₁,k₂) mode Hopf-zero bifurcation. First, the conditions for k₁ mode zero bifurcation are obtained by choosing connection weight as the bifurcation parameter. It is found that the connection weight has a great impact on the properties of steady state. With connection weight increasing, the homogeneous steady state becomes inhomogeneous, which means that the connection weight can affect the spatial stability of steady state. Then, the specified conditions for the k₂ mode Hopf bifurcation and the (k₁,k₂) mode Hopf-zero bifurcation are established. By using the center manifold, the third-order normal form of the Hopf-zero bifurcation is obtained. Through the analysis of the normal form, the bifurcation diagrams on two parameters' planes (connection weight and time delay) are obtained, which contains six areas. Some interesting spatial patterns are found in these areas: a homogeneous periodic solution, a homogeneous steady state, two inhomogeneous steady state, and two inhomogeneous periodic solutions.

There is today a growing need to accurately model the angular scattering response of metasurfaces for optical analog processing applications. However, the current metasurface modeling techniques are not well suited for such a task since they are limited to small angular spectrum transformations, as shall be demonstrated. The goal of this work is to overcome this limitation by improving the modeling accuracy of these techniques and, specifically, to provide a better description of the angular response of metasurfaces. This is achieved by extending the current methods, which are restricted to dipolar responses and weak spatially dispersive effects, so as to include quadrupolar responses and higher-order spatially dispersive components. The accuracy of the newly derived multipolar model is demonstrated by predicting the angular scattering of a dielectric metasurface placed in a vacuum. This results in a modeling accuracy that is substantially better than the standard dipolar model.

Fractional order nonlinear evolution equations have emerged in recent times as being very important model for depicting the interior behavior of nonlinear phenomena that exist in the real world. In particular, Schrodinger-type fractional nonlinear evolution equations constitute an aspect of the field of quantum mechanics. In this study, the (2 + 1)-dimensional time-fractional nonlinear Schrodinger equation and (1 + 1)-dimensional time-space fractional nonlinear Schrodinger equation are revealed as having different and novel wave structures. This is shown by constructing appropriate analytic wave solutions. A successful implementation of the advised rational ( 1 / ϕ ′ ( ξ ) ) -expansion method generates new outcomes of the considered equations, by comparing them with those already noted in the literature. On the basis of the conformable fractional derivative, a composite wave variable conversion has been used to adapt the suggested equations into the differential equations with a single independent variable before applying the scheme. Finally, the well-furnished outcomes are plotted in different 3D and 2D profiles for the purpose of illustrating various physical characteristics of wave structures. The employed technique is competent, productive and concise enough, making it feasible for future studies.

We study the asymptotic behaviour of eigenvalues and eigenfunctions of 2D vibrating systems with mass density perturbed in a vicinity of closed curves. The threshold case in which resonance frequencies of the membrane and thin inclusion coincide or closely situated is investigated. The perturbed eigenvalue problem can be realized as a family of self-adjoint operators acting on varying Hilbert spaces. However the so-called limit operator which is ultimately responsible for the asymptotics of eigenvalues and eigenfunctions is non-self-adjoint and possesses the Jordan chains of length $2$. Apart from the lack of self-adjointness, the operator has non-compact resolvent. As a consequence, its spectrum has a complicated structure, for instance, the spectrum contains a countable set of eigenvalues with infinite multiplicity., Comment: 24 pages, 4 figures

In this paper, we prove the existence of nontrivial solutions and ground state solutions for the following planar Schrödinger–Poisson system with zero mass − Δ u + ϕ u = ( I α ∗ F ( u ) ) f ( u ) , x ∈ R 2 , Δ ϕ = u 2 , x ∈ R 2 , where α ∈ ( 0 , 2 ), I α : R 2 → R is the Riesz potential, f ∈ C ( R , R ) is of subcritical exponential growth in the sense of Trudinger–Moser. In particular, some new ideas and analytic technique are used to overcome the double difficulties caused by the zero mass case and logarithmic convolution potential.

In this research article, the perturbed nonlinear Schrodinger equation (P-NLSE) is examined by utilizing two analytical methods, namely the extended modified auxiliary equation mapping and the generalized Riccati equation mapping methods. Consequently, we establish several sorts of new families of complex soliton wave solutions such as hyperbolic functions, trigonometric functions, dark and bright solitons, periodic solitons, singular solitons, and kink-type solitons wave solutions of the P-NLSE. Using the mentioned methods, the results are displayed in 3D and 2D contours for specific values of the open parameters. The obtained findings demonstrate that the implemented techniques are capable of identifying the exact solutions of the other complex nonlinear evolution equations (C-NLEEs) that arise in a range of applied disciplines.

We propose a strategy for magnetic navigation of collective stem cell microrobots in blood environments under ultrasound Doppler imaging. The cell microrobots are fabricated through a coculture process of stem cells and iron microparticles, they have spheroidal structures and are actuated under external magnetic fields. The collective cell microrobots can be reversibly gathered and spread by adjusting the magnetic interaction, and these microrobots are able to exhibit collective motion in whole blood under rotating magnetic fields. Simulation results indicate that the induced blood flow around the collective pattern affects the motion of red blood cells, and experimental results show that Doppler signals are observed when emitting ultrasound waves to the microrobots. Due to the induced three-dimensional blood flow, Doppler signals can also be observed when the imaging plane is above the collective microrobots, which enables indirect localization when performing navigation on uneven surfaces. Moreover, collective patterns of different numbers of microrobots are formed in flowing conditions, and these collective biohybrid agents are actively navigated against flowing blood with a flow rate up to 4.5 mL/min (mean velocity: 5.97 mm/s). Our study investigates a strategy for pattern formation and navigation of collective microrobots under ultrasound Doppler imaging, demonstrating the integration of collective control approach and medical imaging holds great potential for real-time active delivery tasks.

This paper presents the optimality of decay estimate of solutions to the initial value problem of 1D Schrödinger equations containing a long-range dissipative nonlinearity, i.e., λ | u | 2 u. Our aim is to obtain the two results. One asserts that, if the L 2 -norm of a global solution, with an initial datum in the weighted Sobolev space, decays at the rate more rapid than ( log t ) − 1 / 2 , then it must be a trivial solution. The other asserts that there exists a solution decaying just at the rate of ( log t ) − 1 / 2 in L 2 .

Aim: A novel design for non-reversible as well as reversible parity generator and detector in Quantum-dot Cellular Automata (QCA) technology is presented in this research article. Parity generator and detector circuits are reliable error-checking components of a nano-communication system. Objective: The main focus of this research is to design an ultra-low-power fault-tolerant reversible gate implementation of the parity logic function in QCA. An efficient QCA design layout with minimal area, less latency and the least energy dissipation is desired. Methods: The proposed designs are developed using Quantum-dot Cellular Automata (QCA) technology. The circuits are optimized using majority gate reduction and clock zone reduction techniques. Also, the cell-cell interaction technique is employed to further optimize the QCA circuit. To increase the fault tolerance and ultra-low power operation, reversible QCA circuits are designed using cascaded Feynman gates. Results Conclusion: The efficiency of the parity generator and detector is calculated to be more than 25% compared to existing QCA layouts. It is demonstrated in this paper that the proposed circuits perform exceptionally well on every design parameter. The design parameters under consideration are cell count, cell area, complexity, crossover count, latency and energy dissipation. Conclusion: Using reversible logic, a fault-tolerant and defect-sensitive circuit are developed for parity generation and detection.

Pole skipping is a recently discovered subtle effect in the thermal energy density retarded two point function at a special point in the complex $(\omega,p)$ planes. We propose that pole skipping is determined by the stress tensor contribution to many-body chaos, and the special point is at $(\omega,p)_\text{p.s.}= i \lambda^{(T)}(1,1/u_B^{(T)})$, where $\lambda^{(T)}=2\pi/\beta$ and $u_B^{(T)}$ are the stress tensor contributions to the Lyapunov exponent and the butterfly velocity respectively. While this proposal is consistent with previous studies conducted for maximally chaotic theories, where the stress tensor dominates chaos, it clarifies that one cannot use pole skipping to extract the Lyapunov exponent of a theory, which obeys $\lambda\leq \lambda^{(T)}$. On the other hand, in a large class of strongly coupled but non-maximally chaotic theories $u_B^{(T)}$ is the true butterfly velocity and we conjecture that $u_B\leq u_B^{(T)}$ is a universal bound. While it remains a challenge to explain pole skipping in a general framework, we provide a stringent test of our proposal in the large-$q$ limit of the SYK chain, where we determine $\lambda,\, u_B,$ and the energy density two point function in closed form for all values of the coupling, interpolating between the free and maximally chaotic limits. Since such an explicit expression for a thermal correlator is one of a kind, we take the opportunity to analyze many of its properties: the coupling dependence of the diffusion constant, the dispersion relations of poles, and the convergence properties of all order hydrodynamics., Comment: 39 pages, 13 figures

An explicit formula for a new type of beams, which in this work are called the "special" hyperbolic Bessel-Gaussian (SHBG) beams, has been derived, using the method of the Hankel transform formulated in our previous work. The fundamental properties of these beams are analyzed. The parameters that define the beam shape have been identified and related to those of the fundamental Gaussian beam. The analytical expressions for the SHBG beams include an additional parameter $\gamma$, which allows the beam's shape to be modified to some extent. In the plane perpendicular to the propagation direction, these beams exhibit the annular nature. Interestingly, initially (i.e. near the beam's spot) a single ring splits into a number of rings as one is moving along the beam. This is especially apparent for $\gamma$ close to unity, as this effect then appears for values of $z$ relatively small compared to the Rayleigh length i.e., where the energy concentration in the beam is still high. The phase of the wave, whose behavior is in certain aspects typical of modes having the vortex character, is also studied in this paper., Comment: 9 pages, 8 figures, ReVTeX

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

Titan longitudinal librations are dependent on the satellite internal structure and the elastic behavior of the surface. The elastic deformation of the surface is related to the perturbing potential through the Love theory. In a previous paper, we described the deformation as a response to the tidal potential exerted by Saturn at orbital frequency. Here we improve the tidal deformation reponse by including the effect of the libration angle and the orbital perturbations. We then provide the libration amplitudes associated with the rotational model of a tidally deformed three-layer Titan evolving on a non-Keplerian orbit.

In this paper, we study the phenomenon of concentration and the formation of delta shock wave in vanishing adiabatic exponent limit of Riemann solutions to the Aw–Rascle traffic model. It is proved that as the adiabatic exponent vanishes, the limit of solutions tends to a special delta-shock rather than the classical one to the zero pressure gas dynamics. In order to further study this problem, we consider a perturbed Aw–Rascle model and proceed to investigate the limits of solutions. We rigorously proved that, as the adiabatic exponent tends to one, any Riemann solution containing two shock waves tends to a delta-shock to the zero pressure gas dynamics in the distribution sense. Moreover, some representative numerical simulations are exhibited to confirm the theoretical analysis.

This paper explores some novel solutions to the generalized Schrodinger-Boussinesq (gSBq) equations, which describe the interaction between complex short wave and real long wave envelope. In order to derive some novel complex hyperbolic and complex trigonometric function solutions, the sine-Gordon equation method (sGEM) is applied to the gSBq equations. Novel complex hyperbolic and trigonometric function solutions are expressed by the dark, bright, combo dark-bright, W -shaped, M -shaped, singular, combo singular, and periodic wave solutions. The accuracy of the explored solitons is examined under the back substitution to the corresponding equations via the symbolic computation software Maple. It is found from the back substitution outcomes that all soliton solutions satisfy the original equations. The proper significance of the explored outcomes is demonstrated by the three-dimensional (3D) and two-dimensional (2D) graphs, which are presented under the selection of particular values of the free parameters. All the combo-soliton (W-shaped, M-shaped, and periodic wave) solutions are found to be new for the interaction between complex short wave and real long wave envelope in laser physics that show the novelty of the study. Moreover, the applied method provides an efficient tool for exploring novel soliton solutions, and it overcomes the complexities of the solitary wave ansatz method.

This paper proves that the motion of small-slope vorticity fronts in the two-dimensional incompressible Euler equations is approximated on cubically nonlinear timescales by a Burgers–Hilbert equation derived by Biello and Hunter (2010) using formal asymptotic expansions. The proof uses a modified energy method to show that the contour dynamics equations for vorticity fronts in the Euler equations and the Burgers–Hilbert equation are both approximated by the same cubically nonlinear asymptotic equation. The contour dynamics equations for Euler vorticity fronts are also derived.

We propose the results of a theoretical and mathematical model of the growing bubbles at low Mach number in a generalized Newtonian fluid. The system occurs under the effect of magnetic field and s...

Thermoacoustics is about conversion between thermal and acoustical energies to provide alternative green technology for power cycle and cooling system. The oscillatory flow across porous structure inside the system is playing the role of energy conversion between the acoustic wave and the surface of the porous structure. Better understanding of fluid dynamics of oscillatory flow inside thermoacoustic system is therefore important for the thermoacoustic based energy conversion system. This paper presents the ‘entrance’ and ‘exit’ effects of the oscillatory flow within a parallel-plate structure that is placed inside a standing-wave thermoacoustic environment. Two-dimensional SST k-ω CFD models which were validated using experimental data and theoretical predictions were used for this investigation. Two different operating frequencies of 14.2 Hz and 23.6 Hz were studied for flow with five different amplitudes that were represented using drive ratios of 0.3%, 0.83%, 1.5%, 2.1% and 3%. These correspond to cases with Reynolds numbers between 5936 and 62926. Due to the cyclic nature of the flow, a region defined as an ‘exit’ region was observed in addition to the usual ‘entrance’ region and the fully developed region for flow inside a channel. The change of shape of velocity profiles from the ‘m’ shape profile, to the ‘slug-like’ profile and ‘parabolic-like’ profile was discussed in relation to the ‘entrance’ and ‘exit’ effects on flow inside the channel. The ‘entrance’ and ‘exit’ effects become bigger as drive ratio increases. The effect of ‘entrance’ and ‘exit’ are slightly reducing as frequency increases from 14.2 Hz to 23.6 Hz. This may be related to the shorter travel distance of fluid as the frequency increases. The results shown in this paper suggest that the flow within a 200 mm parallel-plate structure should be treated as developing flow especially for flow with low resonance frequency at drive ratio higher than 1%.

Summary Recent developments in predicting microemulsion phase behavior for use in chemical flooding are based on the hydrophilic-lipophilic deviation (HLD) and net-average curvature (NAC) equation-of-state (EoS). The most advanced version of the HLD-NAC EoS assumes that the three-phase micelle characteristic length is constant as parameters like salinity and temperature vary. In this paper, we relax this assumption to improve the accuracy and thermodynamic consistency of these flash calculations. We introduce a variable characteristic length in the three-phase region based on experimental data that is monotonic with salinity or other formulation variables, such as temperature and pressure. The characteristic length at the boundary of the three-phase region is then used for flash calculations in the two-phase lobes for Winsor type II-/II+. The functional form of the characteristic length is made consistent with the Gibbs phase rule. The improved EoS can capture asymmetric phase behavior data around the optimum, whereas current HLD-NAC based models cannot. The variable characteristic length formulation also resolves the thermodynamic inconsistency of existing phase behavior models that give multiple solutions for the optimum. We show from experimental data and theory that the inverse of the characteristic length varies linearly with formulation variables. This important result means that it is easy to predict the characteristic length in the three-phase region, which also improves the estimation of surrounding two-phase lobes. This improved physical understanding of microemulsion phase behavior should greatly aid in the design of surfactant blends and improve recovery predictions in a chemical flooding simulator.

A molecular spintronics device is considered as a highly promising candidate for the quantum hardware in the field of practical quantum information applications. Within this field, local objects always obey the Coulomb blockade effect, where electrons occupy molecular orbitals monotonically in a step-like manner as the gate voltage sweeps. Herein, based on a single-molecule transistor in an external magnetic field, we predict that the charge occupation of both spin channels may show nonmonotonic filling, characterized by a spin-sensitive charge oscillation, contravening the standard Coulomb blockade behavior. We attribute this nonmonotonicity to the competition among the Zeeman effect, the many-body effect, and the symmetry of the quantum states. To obtain significant oscillations, strong electron–electron interaction and low temperature are prerequisites. We demonstrate that the oscillation goes against the spin-polarized transport, and for appropriate parameters, the transistor may act as a perfect electronically-manipulable bidirectional molecular spintronics device. To implement such an ideal, the state-of-the-art numerical renormalization group method is adopted, and an experimental proposal to test these predictions is suggested.

In this study, a theoretical method is proposed to solve shock relations coupled with chemical equilibrium. Not only shock waves in dissociated flows but also detonation waves in combustive mixtures can be solved. The global iterative solving process is specially designed to mimic the physical and chemical process in reactive shock waves to ensure good stability and fast convergence in the proposed method. Within each global step, the single-variable equations of normal and oblique shock relations are derived and solved with the Newton iteration method to reduce the complexity of the problems, and the minimization of free energy method of NASA (National Aeronautics and Space Administration) is adopted to solve equilibrium compositions. It is demonstrated that the convergent process is stable and very close to the real chemical-kinetic process, and high accuracy is achieved in the solutions of normal and oblique reactive shock waves. Moreover, the proposed theoretical method has also been applied to many problems associated with reactive shocks, including the stability of oblique detonation wave, bow detonation over a sphere, and shock reflection in dissociated air. The great importance of using chemical equilibrium to theoretically predict the theoretical range of the wedge angle for a standing oblique detonation wave (the standing window of the oblique detonation wave), the stand-off distance of bow detonation wave and the transition criterion of shock reflection in dissociated air with high accuracy have been addressed.

Homogeneous magnetic field is widely used in various applications, and Helmholtz and Merritt coils are the most commonly used homogeneous field generators. However, only the field homogeneity at the center point is concerned in their design, which leads to restriction for most applications where a certain volume of homogeneous field is required. This indicates that traditional coil configurations can be further optimized. Based upon a comprehensive definition of homogeneous field, improved three-coil and four-coil configurations are proposed in this paper. Practical formulae with normalized coil parameters are given to provide a convenient tool for designers. These formulae establish relationships between coil parameters and the required homogeneous field. The accuracy of the formulae is verified by the finite-element analysis. Comparisons with Merritt coils show that, when getting the same homogeneous field, the improved coils can reduce both power loss and conductor mass by up to 24.8%. Through a comparison among main coil configurations, the improved four-coil configuration is recommended for homogeneous magnetic field generation. For high-intensity magnetic field applications, the winding cross-section effect is analyzed. At last, experiments are performed to verify the theoretical analysis, and the reason why the improved coils have better performance than traditional ones is revealed.

In this paper, we propose optimum and near-optimum adaptive coherent detectors of radar targets in compound-Gaussian clutter with generalized inverse Gaussian texture (CG-GIG clutter). The target amplitude and the speckle covariance matrix are modeled as unknown quantities to be estimated. On the basis of the two-step generalized likelihood ratio test (GLRT) and the estimate of the speckle covariance matrix, the optimum coherent detector and its adaptive version are designed in this paper. It is demonstrated that the proposed optimum coherent detector contains three common detectors, which are the optimum K detector (OKD), the generalized likelihood ratio test linear-threshold detector (GLRT-LTD), and the generalized likelihood ratio test detector for compound-Gaussian clutter with inverse Gaussian texture (GLRT-IG). Due to the existence of the modified Bessel function depending on data, the optimum coherent detector is computationally unrealizable. Therefore, a near-optimum coherent detector with a new structure also named match filter (-MF) detector and its adaptive version (-AMF) are proposed, which decreases the computational cost. The proposed near-optimum coherent detector contains two common detectors, the GLRT-LTD and the -MF detector in K-distributed clutter, and has a comparable detection performance of the near-optimum detector in CG-IG clutter which was proposed before. Theoretical analysis and numerical experiments illustrate that the proposed two detectors for CG-GIG clutter have the constant false alarm ratio (CFAR) property relative to the estimate of the speckle covariance matrix and Doppler steering vector. Moreover, the detection performance of the two coherent detectors are evaluated by the simulated and real data.

In this paper, we study the dynamics of a three-species food chain model with two delays duo to fear. First we discuss the permanence of this delayed model, then we discuss dynamics under six cases: (1) τ 1 = τ 2 = 0 , (2) τ 1 > 0 , τ 2 = 0 , (3) τ 2 > 0 , τ 1 = 0 , (4) τ 1 = τ 2 > 0 , (5) τ 1 ∈ ( 0 , τ 10 ) , τ 2 > 0 , (6) τ 2 ∈ ( 0 , τ 20 ) , τ 1 > 0 . We shall study the Hopf bifurcation about case (5) by center manifold theorem and normal form. At last we shall give simulations which reveal the influence of delays and fear on the dynamics of this predator–prey system.

This article presents the spatial and temporal dynamics of high-power Gaussian laser pulse in relativistic plasma. At higher intensities, the self-focusing and self-compression of laser pulse take place due to the variation in the mass of plasma electrons moving with speed comparable to the speed of light. The two non-linear coupled differential equations for spatial and temporal pulsewidth parameters have been obtained using the moment theory approach. These equations have been solved numerically using the Runga-Kutta method. The variation in the spatial and temporal pulsewidth parameters with the distance of propagation is then used to calculate the energy gained by the electrons, which are trapped by the excited electron plasma wave during laser-plasma interaction. It is observed that spatio-temporal dynamics play an important role in electron acceleration in relativistic plasma.

In this work we study a non-flat Friedmann-Robertson-Walker universe filled with a pressure-less dark matter (DM) and Barrow holographic dark energy (BHDE) whose IR cutoff is the apparent horizon. Among various DE models, (BHDE) model shows the dynamical enthusiasm to discuss the universe's transition phase. According to the new research, the universe transitioned smoothly from a decelerated to an accelerated period of expansion in the recent past. We exhibit that the development of $q$ relies upon the type of spatial curvature. Here we study the equation of state (EoS) parameter for the BHDE model to determine the cosmological evolution for the non-flat universe. The (EoS) parameter and the deceleration parameter (DP) shows a satisfactory behaviour, it does not cross the the phantom line. We also plot the statefinder diagram to characterize the properties of the BHDE model by taking distinct values of barrow exponent $\triangle$. Moreover, we likewise noticed the BHDE model in the $(\omega_{D}-\omega_{D}^{'})$ plane, which can furnish us with a valuable, powerful finding to the mathematical determination of the statefinder. In the statefinder trajectory, this model was found to be able to reach the $\Lambda CDM$ fixed point., Comment: 19 pages, 21 figures

Three-chamber configuration is the simplest type among the fluid soft actuators with multiple degrees of freedom in three-dimension space. However, the motion control of the three-chamber fluid soft actuator is a challenging task because of the strong coupling effect of the chambers which are connected together. This short paper develops a novel electrohydraulic control device with decoupling function. The supplied pressures of three cylinders in the electrohydraulic control device are linked by a swash plate mechanism. The axial displacement, the tilted angle, and the azimuth angle of the swash plate are driven by three electrical motors separately and corresponding to the stretched length, the bending angle, and the yaw angle of the three-chamber soft actuator. Thus, the three outputs of the soft actuator can be independently controlled. Theoretical analysis is implemented to provide basis for machine design. A prototype is fabricated and experiments under both of static and dynamic conditions are carried out to evaluate the performance of the proposed concept. The results show that the electrohydraulic control device can effectively drive the three-chamber soft actuator and reduce the difficulty of controller design.

The present study numerically, investigates the aerodynamic characteristics of low speed flow past symmetric NACA airfoils, for various t/c values of 0.10, 0.15, 0.18, 0.21 and 0.24 at chordwise Reynolds numbers of 2 × 105 and 4 × 105, where t is the airfoil thickness and c is the airfoil chord. The presence of laminar separation bubble is indicated by oscillatory behaviour of pressure coefficient on the suction surface beyond peak pressure. The fluctuations in lift/drag are seen at smaller t/c values of 0.10 and 0.15, whereas no fluctuations are seen at a higher t/c value of 0.21. An empirical expression is developed to predict the mean lift, viscous as well as total drag coefficients for symmetric airfoils as a function of t/c only, which varies linearly for both the Reynolds numbers studied. The velocity vectors show the flow separations phenomenon only at smaller t/c values of 0.10 and 0.15, while at a higher t/c value of 0.21, well behaved and steady flow field is seen, which might be the reason for the absence of lift/drag fluctuations. The far-field acoustic measurements of symmetric NACA airfoils for various thickness ratios reveal that thicker airfoil (NACA0021, t/c = 0.21) radiates lower acoustic emissions (i.e., about 2 dB) as compared to the thinner (NACA0010, t/c = 0.10) ones.

The reattached boundary layer in the interaction of an oblique shock wave with a flat-plate turbulent boundary layer at Mach number 2.25 is studied by means of Direct Numerical Simulation (DNS). The numerical results are carefully compared with available experimental and DNS data in terms of turbulence statistics, wall pressure and skin friction. The coherent vortex structures are significantly enhanced due to the shock interaction, and the reattached boundary layer is characterized by large-scale structures in the outer region. The space-time correlation of fluctuating wall shear stress and streamwise velocity fluctuation reveals that the structural inclination angle exhibits a gradual decrease during the recovery process. The scale interactions are analyzed by using a two-point amplitude modulation correlation. A possible mechanism is proposed to account for the strong amplitude modulation in the downstream region. Moreover, the mean skin-friction is decomposed to understand the physically informed contributions. Unlike the upstream Turbulent Boundary Layer (TBL), the contribution associated with the Turbulence Kinetic Energy (TKE) production is greatly amplified, while the spatial growth contribution induced by the pressure gradient largely inhibits skin-friction generation. Based on bidimensional empirical mode decomposition, the turbulence kinetic energy production contribution is further split into different terms with specific spanwise length scales.

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.

Unsteady convective flows, over an infinite, vertical, heated, circular cylinder is investigated by considering the generalized Fourier's law of the thermal process. The generalized constitutive equation of thermal flux is a partial fractional differential equation based on the generalized time-fractional derivative with Mittag-Leffler kernel, namely the generalized Atangana-Baleanu derivative. Closed forms of the analytical solutions for the temperature and velocity fields, expressed with Bessel and Struve functions, are determined using the Laplace transform and the Weber-Dirichlet transform. The ordinary case corresponding to classical Fourier's law is also obtained. Numerical simulations, obtained with the Mathcad software, are carried out and graphically illustrated to analyze the heat transfer and fluid motion. The influence of the fractional orders of the time-derivative and of the Prandtl and Grashof numbers on the fluid temperature and velocity is studied.

Convection differential equations that include momentum, energy and mass balance equations are used for the simulations of boundary layer (BL) flows. In convection analysis, it is in execution to dimensionless the BL system through similarity variable. However, a wide range of convection differential equations cannot be non-dimensionalized using similarity variable therefore the intent of this manuscript is to develop non-similar model for the forced convective magnetic flow of a viscous fluid above an exponentially expanding surface saturated by nano-fluid. The non-similarity is due to the exponential stretching of the surface and viscous dissipation. Influences of chemical reaction and heat generation are also incorporated. The non-similarity transformation is applied to the nonlinear partial differential system (PDE’s) to transform them into dimensionless PDE’s. Non-similar system is analytically approximated by adapting local non-similarity (LNS) and then it is numerically simulated by finite difference based bvp4c algorithm to explore the influences of significant numbers named as Prandlt number, chemical reaction, magnetic field, Brownian motion, heat generation, Eckert number, thermophoresis on concentration, velocity and temperature distribution. Auxiliary consequences presume that the heat penetration in fluid rises with enhancements in Brownian motion and Prandtl number, while it can be perceived here that for positive estimations of heat generation causes the thicker temperature field. Increasing non-similarity variable and magnetic number become reason for the reduction of temperature profile and chemical reaction is reason of reduced concentration profile.

The degree distribution of network nodes exhibits scale-free features, which is a universal phenomenon in natural and social networks. It is commonly believed that growth and linear preferential attachment are the evolutionary mechanisms of scaling laws. However, the underlying cause behind these mechanisms remains unknown. In this paper, we propose the concept of the topology state of network nodes, and then define the network homomorphism ratio. Combining the total energy of the network defined in previous studies, we systematically investigate the connection between these two quantities in preferential attachment growth networks. Our results show that under the thermodynamic limit condition, the emergence of the scaling laws of the preferential attachment growth network is dominated by two principles. One principle is that the homomorphism ratio gradually tends to zero as the network grows, and the other principle is that the total energy of the system is the lowest under the condition of satisfying principle one. Interestingly, these two principles of the network are similar to the arrangement rules of electrons outside the nucleus which dominated by the Pauli exclusion principle and the principle of minimum energy.

Fluids are seen in, e.g., mechanical, chemical and biomedical engineering, astrophysics, biology and geophysics. In this paper, we investigate a ( 3 + 1 ) -dimensional generalized variable-coefficient shallow water wave equation for the flow below a pressure surface in a fluid. Via the Kadomtsev–Petviashvili hierarchy reduction, we derive the rational solutions in terms of the Gramian. The first-order, higher-order and multi-lump waves are obtained. We present the first-order lump waves on the periodic, monotonically increasing, parabolic and Gaussian backgrounds. We observe the second-order lump waves: Two lump waves interact with each other and separate into two new lump waves; After the interaction, velocities and amplitudes of the two lump waves change. Two-lump waves are also shown: Different from the second-order lump waves, after the interaction, the two-lump waves propagate with their original velocities and amplitudes.

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

The flow of a compressible fluid with slip through a cylinder with an asymmetric local constriction has been considered both numerically, as well as analytically. For the numerical work, a particle-based method whose dynamics is governed by the multiparticle collision (MPC) rule has been used together with a generalized boundary condition that allows for slip at the wall. Since it is well known that an MPC system corresponds to an ideal gas and behaves like a compressible, viscous flow on average, an approximate analytical solution has been derived from the compressible Navier–Stokes equations of motion coupled to an ideal gas equation of state using the Karman–Pohlhausen method. The constriction is assumed to have a polynomial form, and the location of maximum constriction is varied throughout the constricted portion of the cylinder. Results for centerline densities and centerline velocities have been compared for various Reynolds numbers, Mach numbers, wall slip values and flow geometries.

The analysis of a previous paper, in which it was shown that the energy for the Aharonov-Bohm effect could be traced to the interaction energy between the magnetic field of the electron and the background magnetic field, is extended to cover the case in which the magnetic field of the electron is shielded from the background magnetic field by superconducting material. The paradox that arises from the fact that such a shielding would apparently preclude the possibility of an interaction energy is resolved and, within the limits of the ideal situation considered, the observed experimental result is derived., Published version: Foundations of Physics, Vol. 23 (1993) 703-709 doi: 10.1007/BF01883804 arXiv-ed February 18, 1993 ; \LaTeX-ed May 1, 2023 Uploaded to arXiv to help researchers with limited library facilities

In this paper, we present the methods to detect the channel delay profile and the Doppler spectrum of shallow underwater acoustic channels (SUAC). In our channel sounding methods, a short impulse in form of a sinusoid function is successively sent out from the transmitter to estimated the channel impulse response (CIR). A bandpass filter is applied to eliminate the interference from out-of-band (OOB). A threshould is utilized to obtain the maximum time delay of the CIR. Multipath components of the SUAC are specified by correlating the received signals with the transmitted sounding pulse with its shifted phases from 0 to 2Π. We show the measured channel parameters, which have been carried out in some lakes in Hanoi. The measured results illustrate that the channel is frequency selective for a narrow band transmission. The Doppler spectrum can be obtained by taking the Fourier transform of the time correlation of the measured channel transfer function. We have shown that, the theoretical maximum Doppler frequency fits well to that one obtained from measurement results.

The crystal structure of a solid largely dictates its electronic, optical and mechanical properties. Indeed, much of the exploration of quantum materials in recent years including the discovery of new phases and phenomena in correlated, topological and two-dimensional materials—has been based on the ability to rationally control crystal structures through materials synthesis, strain engineering or heterostructuring of van der Waals bonded materials. These static approaches, while enormously powerful, are limited by thermodynamic and elastic constraints. An emerging avenue of study has focused on extending such structural control to the dynamical regime by using resonant laser pulses to drive vibrational modes in a crystal. This paradigm of ‘nonlinear phononics’ provides a basis for rationally designing the structure and symmetry of crystals with light, allowing for the manipulation of functional properties at high speed and, in many instances, beyond what may be possible in equilibrium. Here we provide an overview of the developments in this field, discussing the theory, applications and future prospects of optical crystal structure engineering. The interaction between light and the crystal lattice of a quantum material can modify its properties. Utilizing nonlinear interactions allows this to be done in a controlled way to design specific non-equilibrium functionalities.

A three-dimensional slowly rotating black hole solution in the presence of negative cosmological constant in the Einstein-power-Maxwell theory is studied. It is shown that in the small rotation limit the electric field, diagonal metric function and thermodynamic properties in the small rotation limit are the same as for static case, whereas the small rotation gives in addition a non-diagonal metric function and magnetic field which are also small. For these functions cased by rotation of black hole it was obtained exact integral solution and analytic asymptotic solution.

The ab-plane optical conductivity of the Weyl semimetal TaP is calculated from the band structure and compared to the experimental data. The overall agreement between theory and experiment is found to be best when the Fermi level is slightly (20 to 60 meV) shifted upwards in the calculations. This confirms a small unintentional doping of TaP, reported earlier, and allows a natural explanation of the strong low-energy (50 meV) peak seen in the experimental ab-plane optical conductivity: this peak originates from transitions between the almost parallel non-degenerate electronic bands split by spin-orbit coupling. The temperature evolution of the peak can be reasonably well reproduce by calculations using an analog of the Mott formula., Deutsche Forschungsgemeinschaft