Initial Separation Research Articles

Simulation of the orbit and spin period evolution of the double pulsars PSR J0737-3039 from their birth to coalescence induced by gravitational wave radiation

The complete orbital and spin period evolutions of the double neutron star (NS) system PSR J0737–3039 are simulated from birth to coalescence, which include the two observed radio pulsars classified as primary NS PSR J0737–3039A and companion NS PSR J0737–3039B. By employing the characteristic age of PSR J0737–3039B to constrain the true age of the double pulsar system, the initial orbital period and initial binary separation are obtained as 2.89 h and 1.44 × 106 km, respectively, and the coalescence age or the lifetime from the birth to merger of PSR J0737–3039 is obtained to be 1.38 × 108 yr. At the last minute of coalescence, corresponding to the gravitational wave frequency changing from 20 Hz to 1180 Hz, we present the binary separation of PSR J0737–3039 to be from 442 km to 30 km, while the spin periods of PSR J0737–3039A and PSR J0737–3039B are 27.10 ms and 4.63 s, respectively. From the standard radio pulsar emission model, before the system merged, the primary NS could still be observed by a radio telescope, but the companion NS had crossed the death line in the pulsar magnetic-field versus period (B – P) diagram at which point it is usually considered to cease life as a pulsar. This is the first time that the whole life evolutionary simulation of the orbit and spin periods for a double NS system is presented, which provides useful information for observing a primary NS at the coalescence stage.

The Analysis of The Process of Barley Grain Separation from Undesirable Particles

The article focuses on the intensification of raw barley grains initial purification and separation processes before the subsequentprocessing in the area of brewing. Above all, it deals with the physical and mechanical concepts of the purification and separationof qualitatively satisfactory grains from undesirable impurities, e.g. coarse impurities, as the prevention from the potential damageof milling and scrapping facilities. Four different cultivated barley species were tested within the study. Physical and mechanicalparameters were determined in all samples, for instance powder density, angle of internal friction and external friction angle withsteel contact material, particle size distribution and morphology. The first results of measuring revealed the difference in the qualityof initial entering component of barley grains before the purification process compared to the output quality of grains after machinepurification and separation processes in the facilities determined for the subsequent grain storage. As a result of the non-effectiveprocess of separation, the final quality of the product, i.e. the beer, may be affected by the qualitative parameters of partial processesinvolved in treating barley grains.

Orbital stability of compact three-planet systems, I: Dependence of system lifetimes on initial orbital separations and longitudes

We explore the orbital dynamics of systems consisting of three planets, each as massive as the Earth, on coplanar, initially circular, orbits about a star of one solar mass. The initial semimajor axes of the planets are equally spaced in terms of their mutual Hill radius, which is equivalent to a geometric progression of orbital periods for small planets of equal mass. Our simulations explore a wide range of spacings of the planets, and were integrated for virtual times of up to 10 billion years or until the orbits of any pair of planets crossed. We find the same general trend of system lifetimes increasing exponentially with separation between orbits seen by previous studies of systems of three or more planets. One focus of this paper is to go beyond the rough trends found by previous numerical studies and quantitatively explore the nature of the scatter in lifetimes and the destabilizing effects of mean motion resonances. In contrast to previous results for five-planet systems, a nontrivial fraction of three-planet systems survive at least several orders of magnitude longer than most other systems with similar initial separation between orbits, with some surviving 1010 years at much smaller orbital separations than any found for five-planet systems. Substantial shifts in the initial planetary longitudes cause a scatter of roughly a factor of two in system lifetime, whereas the shift of one planet's initial position by 100 m along its orbit results in smaller changes in the logarithm of the time to orbit crossing, especially for systems with short lifetimes.

Wind Tunnel Experiments and Numerical Study on Performance Characteristics of an H-type Vertical Axis Wind Turbine in the Spanwise Direction

The aerodynamic forces and vortex characteristics of an H-type Vertical Axis Wind Turbine (VAWT) become complicated because of dynamic stall, particularly in the three-dimensional impact on the blade spanwise direction. This study focused on the evaluation of the aerodynamic performance and vortex characteristics of an H-type VAWT in the spanwise direction by numerical simulations and wind tunnel experiments. Pressure acting on the blade surface was obtained from multiport pressure measurement devices by wind tunnel. Meanwhile, the vortex field around different blade sections was investigated through numerical simulations. The stall behavior was analysed by comparing the results of numerical simulations and experiments. As a result, the tangential force of single blade was mainly contributed at the chordwise position of x/c≤0.4c and the power of single blade was mainly contributed at the azimuthal angle range of 60°≤θ≤150° in the blade section position region of 0≤z/(H/2)≤0.7. At the section position of z/(H/2)=0.5, the initial flow separation was found at the suction side and progressed forward to the leading edge. With the increase of the tip speed ratios, the decreasing position of the averaged local power coefficient of each section was closer to the middle section of z/(H/2)=0, and the attenuation speed became faster. The power coefficient reductions at the blade section position of z/(H/2)=0.9 were 38.29%, 46.78% and 56.42% when the tip speed ratios were 1.38, 2.19 and 2.58, respectively. The results of this study provided a better understanding of the development of the performance characteristics and vortex characteristics of H-type VAWT.

An Energy-conserving Integrator for Conservative Hamiltonian Systems with Ten-dimensional Phase Space

Abstract In this paper, an implicit nonsymplectic exact energy-preserving integrator is specifically designed for a ten-dimensional phase-space conservative Hamiltonian system with five degrees of freedom. It is based on a suitable discretization-averaging of the Hamiltonian gradient, with a second-order accuracy to numerical solutions. A one-dimensional disordered discrete nonlinear Schrödinger equation and a post-Newtonian Hamiltonian system of spinning compact binaries are taken as our two examples. We demonstrate numerically that the proposed algorithm exhibits good long-term performance in the preservation of energy, if roundoff errors are neglected. This result is independent of time steps, initial orbital eccentricities, and regular and chaotic orbital dynamical behavior. In particular, the application of appropriately large time steps to the new algorithm is helpful in reducing time-consuming and roundoff errors. This new method, combined with fast Lyapunov indicators, is well suited to studying the influence of some parameters or initial conditions related to chaos in the two example problems. It is found that chaos in the former system is mainly responsible for one of the parameters. In the latter problem, a combination of small initial separations and high initial eccentricities can easily induce chaos.

Intensity Change of Binary Tropical Cyclones (TCs) in Idealized Numerical Simulations: Two Initially Identical Mature TCs

AbstractThis study investigates the intensity change of binary tropical cyclones (TCs) in idealized cloud-resolving simulations. Four simulations of binary interaction between two initially identical mature TCs of about 70 m s−1 with initial separation distance varying from 480 to 840 km are conducted in a quiescent f-plane environment. Results show that two identical TCs finally merge if their initial separation distance is within 600 km. The binary TCs presents two weakening stages (stages 1 and 3) with a quasi-steady evolution (stage 2) in between. Such intensity change of one TC is correlated with the upper-layer vertical wind shear (VWS) associated with the upper-level anticyclone (ULA) of the other TC. The potential temperature budget shows that eddy radial advection of potential temperature induced by large upper-layer VWS contributes to the weakening of the upper-level warm core and thereby the weakening of binary TCs in stage 1. In stage 2, the upper-layer VWS first weakens and then restrengthens with relatively weak magnitude, leading to a quasi-steady intensity evolution. In stage 3, due to the increasing upper-layer VWS, the nonmerging binary TCs weaken again until their separation distance exceeds the local Rossby radius of deformation of the ULA (about 1600 km), which can serve as a dynamical critical distance within which direct interaction can occur between two TCs. In the merging cases, the binary TCs weaken prior to merging because highly asymmetric structure develops as a result of strong horizontal deformation of the inner core. However, the merged system intensifies shortly after merging.

A rate-dependent cohesive zone model with the effects of interfacial viscoelasticity and progressive damage

A generalized rate-dependent cohesive zone model for describing the interfacial viscoelasticity and progressive damage of mode I fracture is presented. The proposed model has efficiently extended the traditional bi-linear cohesive traction-separation law to remove the assumptions that some of the rate-dependent parameters such as elastic stiffness, initial separation and strength, critical separation are constant at different loading speeds. Furthermore, the rate-dependency of the damage evolution, which is observed in experiments but largely neglected in the previous models, is established to describe the rate-dependent fracture process linked with the generalized traction-separation law, and an equivalent generalized Maxwell model (GMM), based on the Kohlrausch-William-Watts function with significant fewer material parameters required as input, is proposed to describe the time and history dependent stress–strain relationship of the viscoelastic interface material. The proposed model is validated by the simulations of the DCB tests with both the SBR/NR rubber interface and Polyurethane interface.

On ab initio-based, free and closed-form expressions for gravitational waves

We introduce a new approach for finding high accuracy, free and closed-form expressions for the gravitational waves emitted by binary black hole collisions from ab initio models. More precisely, our expressions are built from numerical surrogate models based on supercomputer simulations of the Einstein equations, which have been shown to be essentially indistinguishable from each other. Distinct aspects of our approach are that: (i) representations of the gravitational waves can be explicitly written in a few lines, (ii) these representations are free-form yet still fast to search for and validate and (iii) there are no underlying physical approximations in the underlying model. The key strategy is combining techniques from Artificial Intelligence and Reduced Order Modeling for parameterized systems. Namely, symbolic regression through genetic programming combined with sparse representations in parameter space and the time domain using Reduced Basis and the Empirical Interpolation Method enabling fast free-form symbolic searches and large-scale a posteriori validations. As a proof of concept we present our results for the collision of two black holes, initially without spin, and with an initial separation corresponding to 25–31 gravitational wave cycles before merger. The minimum overlap, compared to ground truth solutions, is 99%. That is, 1% difference between our closed-form expressions and supercomputer simulations; this is considered for gravitational (GW) science more than the minimum required due to experimental numerical errors which otherwise dominate. This paper aims to contribute to the field of GWs in particular and Artificial Intelligence in general.

Dissipative soliton dynamics and switching in split ring resonator based metamaterial with multi-photon absorption and diffusion

Compound dissipative soliton (DS) is obtained theoretically in Split Ring Resonator based metamaterial having higher order nonlinearities, multi-photon absorption and diffusion. Effects of both the multi-photon absorption and diffusion on the DS are found to be detrimental however can be compensated by a suitable external gain to stabilize the DS. The interaction dynamics of two DSs is studied for different phase difference and initial separation. The phase controlled soliton switching is demonstrated. Notably, a weak solitonic beam is demonstrated to control a strong one. The DSs are robust against the randomness of the metamaterial. The outcome of this investigation may be useful to design experiments that employ DS in higher order nonlinear metamaterials.

Investigation of continuous and discontinuous contact cases in the contact mechanics of graded materials using analytical method and FEM

The aim of this paper was to examine the continuous and discontinuous contact problems between the functionally graded (FG) layer pressed with a uniformly distributed load and homogeneous half plane using an analytical method and FEM. The FG layer is made of non-homogeneous material with an isotropic stress–strain law with exponentially varying properties. It is assumed that the contact at the FG layer-half plane interface is frictionless, and only the normal tractions can be transmitted along the contacted regions. The body force of the FG layer is considered in the study. The FG layer was positioned on the homogeneous half plane without any bonds. Thus, if the external load was smaller than a certain critical value, the contact between the FG layer and half plane would be continuous. However, when the external load exceeded the critical value, there was a separation between the FG layer and half plane on the finite region, as discontinuous contact. Therefore, there have been some steps taken in this study. Firstly, an analytical solution for continuous and discontinuous contact cases of the problem has been realized using the theory of elasticity and Fourier integral transform techniques. Then, the problem modeled and twodimensional analysis was carried out by using ANSYS package program based on FEM. Numerical results for initial separation distance and contact stress distributions between the FG layer and homogeneous half plane for continuous contact case; the start and end points of separation and contact stress distributions between the FG layer and homogeneous half plane for discontinuous contact case were provided for various dimensionless quantities including material inhomogeneity, distributed load width, the shear module ratio and load factor for both methods. The results obtained using FEM were compared with the results found using analytical formulation. It was found that the results obtained from analytical formulation were in perfect agreement with the FEM study.

VPA: Computer program for the computation of the phase shift in atom–atom potential scattering using the Variable Phase Approach

A computer code for the computation of the phase shift in atom–atom and electron–atom potential scattering is presented. The phase shift is the central quantity required for the calculation of all types of scattering cross sections. The program uses the Variable Phase Approach (VPA). This is the only exact method for the direct calculation of the scattering phase shift. All other methods are based on examining the large distance behavior of the exact solution of the Schrödinger equation. Such methods yield the phase shift only modulo π. The absolute value of the phase shift and its variation with scattering energy is, however, needed for a full understanding of the scattering process, such as for instance in the study of shape resonances and Glory oscillations. The VPA has been sparingly used owing to the instability of the underlying equations and the consequent difficulty of writing computer code to solve them. We present a computer code for the efficient implementation of the VPA method for atom–atom scattering problems over a wide range of scattering energies. The code works for potentials which are singular and for those that are non-singular at the origin. An example of the implementation of the code is given for both an interaction potential with an attractive well and for a purely repulsive potential. Program summaryProgram title: VPA:Variable Phase ApproachCPC Library link to program files: https://dx.doi.org/10.17632/zh248d2362.1Code Ocean capsule: https://dx.doi.org/10.24433/CO.8146850.v1Licensing provisions: GNU General Public License 3 (GPL)Programming language: Fortran 90Nature of problem: To compute the quantum mechanical phase shift in an atom–atom or an electron–atom potential scattering problem. The interaction potential, dependent on a single radial coordinate, is defined by the user.Solution method: The Variable Phase Approach is used. This is the only available method for the direct calculation of the phase shift. The initial internuclear separation for the integration is chosen with the help of the analytical solution for a hard sphere core for all orbital angular momentum quantum numbers L of interest. The first-order nonlinear equation is integrated numerically with a modified LSODA19,20 program. The analytic formula for calculation of the Jacobian of the equation is also provided.Additional comments including restrictions and unusual features: Computer codes for the atom–atom interaction potential, POTENT1, and for its derivative with respect to the inter nuclear separation, DPOTENT1, must be supplied by a user. The calculation of the spherical Bessel and Neumann functions required is performed explicitly for large l angular momentum quantum numbers where the standard upward iterative generation of the functions becomes unstable.

Van der Waals interactions and oscillatory behaviour of carbon onions interacting with a fully constrained graphene sheet

This study focuses on the van der Waals (vdW) interactions and oscillatory behaviour of nested spherical fullerenes (carbon onions) in the vicinity of a single-layer graphene (SLG) sheet. The carbon onions are of Ih symmetries and the graphene sheet is modelled as a fully constrained flat surface. Employing the continuum approximation along with the 6–12 Lennard-Jones (LJ) potential function, explicit analytical expressions are determined to calculate the vdW potential energy and interaction force. The equation of motion is solved numerically based on the actual force distribution to attain the displacement and velocity of the carbon onion. Using the conservation of mechanical energy principle, a semi-analytical expression is also derived to accurately evaluate the oscillation frequency. Numerical results are presented to examine the influences of size of carbon onion and initial conditions (initial separation distance and initial velocity) on the operating frequency of carbon onion–SLG sheet oscillators. It is shown that carbon onion executes oscillatory motion above the graphene sheet with frequencies in the gigahertz (GHz) range. It is further observed that smaller structures of carbon onions produce greater frequencies. We comment that the presented results in this study would contribute to the development of new generation of nano-oscillators.

Congruence between molecular and morphological systematics of Alpine non‐biting midges (Chironomidae, Diamesinae)

AbstractIn mountain regions, climate change is resulting in glacial retreat, causing biodiversity loss in glacial‐fed streams (kryal habitat). Diamesa species (Diptera Chironomidae), the main colonizers of the kryal in the Alps, are the aquatic insects more threatened by extinction. In recent years, DNA barcoding was successfully adopted to delimit species of chironomids and provided species identification. We highlighted that for the Diamesa genus, inconsistencies remain between identification on a morphological and molecular basis, mainly within cinerella and zernyi groups, raising doubts about the validity of head colour as a good diagnostic taxonomic character. Molecular phylogeny reconstruction based on mitochondrial (cytochrome oxidase subunits I and II) and one nuclear (ribosomal 18S rRNA) markers revealed that D. bohemani and D. zernyi on one hand, and D. cinerella and D. tonsa on the other hand, represent populations of the same species. Divergence times suggested that the radiation of these alpine species seems to have been driven by the climatic events with the alternation of glacial periods that happened in the Pliocene and Pleistocene. The initial separation of the oriental species D. steinboecki seems to be due to the tectonic movements of the Periadriatic fault system that probably favoured the emergence of lakes and streams, successively colonized by D. steinboecki. This study raises important concerns, from the validity of diagnostic characters used today to identify larval types up to the uncertainty about how many species of Diamesa inhabit the European Alps and what their fate will be within the scenario of climate change.

Ιdentification of spatiotemporal seismicity clusters in central Ionian Islands (Greece)

The spatiotemporal evolution of seismicity of an accurately relocated earthquake catalog in the central Ionian Islands, Greece, is explored, by the systematic identification of the earthquake clusters over the period September 2016–December 2019. Manual waveform phase picking was the input for the relocation leading to 13,632 earthquakes that compose a data set with a completeness magnitude as low as Mc = 1.5. The clustering procedure engages a temporal stochastic point process, the Markovian Arrival Process (MAP), for an initial separation of the background seismicity from potential seismic excitations, using the changes in the seismicity rate and a density-based clustering algorithm, DBSCAN, for the detection of elevated spatial density areas. A high concentration of temporally persistent clusters is identified along the western coastline of Lefkada Island, in the parallel step-over faults between the two major fault branches of the Kefalonia Transform Fault Zone and in the Myrtos Gulf area in Kefalonia, which are spatially correlated to the positive static stress changes induced by the coseismic slip of the Mw6.5 November 17, 2015 Lefkada main shock. The method presented remarkable potential in the identification of clusters in 3-D space along with the seismicity migration during the temporal evolution of seismic sequences. Multiple secondary faults of the Kefalonia segment can be revealed and the dominant triggering mechanisms can be illuminated contributing towards the understanding of the regional faulting properties and mechanics, an outcome that cannot be achieved solely by studying the large earthquakes, due to their rarity. The temporal and spatial clustering properties of microseismicity shed light on the preparation phase of the large earthquakes as being part of this process, thus contributing to the seismic hazard assessment.

Relative Dispersion on the Inner Shelf: Evidence of a Batchelor Regime

AbstractOceanographic relative dispersion (based on drifter separations r) has been extensively studied, mostly finding either Richardson–Obukhov () or enstrophy cascade [] scaling. Relative perturbation dispersion (based on perturbation separation r − r0, where r0 is the initial separation) has a Batchelor scaling () for times less than the r0-dependent Batchelor time. Batchelor scaling has received little oceanographic attention. GPS-equipped surface drifters were repeatedly deployed on the Inner Shelf off of Pt. Sal, California, in water depths ≤ 40 m. From 12 releases of ≈18 drifters per release, perturbation and regular relative dispersion over ≈4 h are calculated for 250 ≤ r0 ≤ 1500 m for each release and the entire experiment. The perturbation dispersion is consistent with Batchelor scaling for the first 1000–3000 s with larger r0 yielding stronger dispersion and larger Batchelor times. At longer times, and scale-dependent diffusivities begin to suggest Richardson–Obukhov scaling. This applies to both experiment averaged and individual releases. For individual releases, nonlinear internal waves can modulate dispersion. Batchelor scaling is not evident in as the correlations between initial and later separations are significant at short time scaling as ~t. Thus, previous studies investigating are potentially aliased by initial separation effects not present in the perturbation dispersion . As the underlying turbulent velocity wavenumber spectra is inferred from the dispersion power law time dependence, analysis of both and is critical.

Formation of vortex rings and hopfions in trapped Bose–Einstein condensates

The topological transition of vortex lines to vortex rings and hopfions is numerically investigated by the Gross–Pitaevskii equation in three-dimensional trapped Bose–Einstein condensates. The shape of the vortex rings formed by the two vortex lines of the vortex dipole depends strongly on the initial separation of the lines. An approximately perfect vortex ring can be obtained by choosing some suitable values of the separation. The deformation of the formed rings depends on the shape of the rings in turn. Furthermore, we show a feasible approach to generate vortex hopfions by imprinting a vortex line in the center of the generated vortex rings. Specifically, the movement of the vortex rings can excite helical waves along the central vortex line of the hopfion structure if the vortex ring is not perfect.

Control of produced water with highly corrosive medium in oil-gas production

The construction of middle oil-gathering facility, in which technological processes are managed in a closed medium is necessary for environmental protection to control highly corrosive medium in oil and gas production. Associated gas separated from the fluid in initial separation unit within middle oil-gathering facility enters gas-gathering point with low pressure, and the liquid - into the pig of oil, water and sand, which should be constructed from iron concrete for cleaning from mechanical impurities sediments and salt as well. The liquid charge from the separation unit and pig of oil, water and sand is based upon the law of communicating vessels. To supply long-life for reservoirs, the inner and outer walls should be covered with a special coating and additionally, electrochemical protection should be provided as well.

A Novel Loaded Tooth Contact Analysis Procedure With Application to Internal–External Straight Bevel Gear Mesh in a Pericyclic Drive

Abstract A comprehensive numerical loaded tooth contact analysis (LTCA) model is proposed for straight bevel gears that exhibit large number of teeth in contact, well beyond the involute line of action limits. This kind of contact is observed when the meshing gears have conformal surfaces, as in a pericyclic mechanical transmission, and is traditionally analyzed using finite element simulations. The pericyclic drive is kinematically similar to an epicyclic bevel gear train and is characterized by load sharing over large number of teeth in an internal–external bevel gear mesh, large shaft angles (175–178 deg), nutational gear motion, and high reduction ratio. The contact region spreads over a large area on the gear tooth flank due to high contacting surface conformity. Thus, a thick plate finite strip method (FSM) was utilized to accurately calculate the gear tooth bending deflection. Based on the tooth deformation calculation model and accounting for initial surface separation, a variational framework is developed to simultaneously solve for load distribution and gear tooth deformation. This is followed by calculation of contact stress, bending stress, mesh stiffness, and transmission error. The results demonstrate the high-power density capabilities of the pericyclic drive and potential for gear noise reduction. The model developed herein is applied with real gear tooth surfaces, as well.

Complexity of Electron Injection Dynamics and Light Soaking Effects in Efficient Dyes for Modern DSSC

Electron transfer dynamics in dye sensitized solar cells (DSSCs) employing triphenylamine Y123 dye were investigated by means of femtosecond broadband transient absorption spectroscopy in the visible and mid-IR range of detection. The electron injection process to the titania conduction band was found to appear biphasically with the time constant of the first component within 350 fs and that of the second component between 80 and 95 ps. Subsequently, the effects of continuous irradiation on the ultrafast and fast electron transfer processes were studied in the systems comprising Y123 dye or carbazole MK2 dye in combination with cobalt- or copper-based redox mediators: [Co(bpy)3](B(CN)4)2/3 (bpy = 2,2′-bipyridine) or [Cu(tmby)2](TFSI)1/2 (tmby = 4,4′,6,6′ tetramethyl-2,2′-bipyridine, TFSI = bis(trifluoromethane)sulfonamide). We have found that the steady-state illumination led to acceleration of the electron injection process due to the lowering of titania conduction band edge energy. Moreover, we have observed that the back electron transfer to the oxidized dye was suppressed. These changes in the initial (up to 3 ns) charge separation efficiency were directly correlated with the photocurrent enhancement.

Dynamic behavior of chloride ion-electrically charged open carbon nanocone oscillators: A molecular dynamics study

This paper is intended to study the dynamic oscillatory behavior of chloride ion inside electrically charged open carbon nanocones (CNCs) using the molecular dynamics (MD) simulations. The small and wide ends of nanocone are assumed to be identically and uniformly charged with positive electric charges. In the simulation, the Tersoff-Brenner (TB) and the Lennard-Jones (LJ) potential functions are employed to evaluate the interatomic interactions between carbon atoms and the van der Waals (vdW) interactions between the ion and the nanocone, respectively. The Coulomb potential is also adopted to evaluate the electrostatic interactions between the ion and the electric charges distributed at both ends of nanocone. Numerical results are presented to examine the effects of magnitude of electric charges, initial separation distance and initial velocity on the mechanical oscillatory behavior of system and the obtained results are also compared with the ones related to an uncharged nanocone. It is found that operating frequency as well as escape velocity enhance considerably as a result of electrostatic interactions. It is further found that regardless of the value of electric charges, optimal oscillation frequency is achievable when no initial velocity is imposed on the ion initially located inside of nanocone with an offset of 2 Å from its small end.