Target Wave Research Articles

Interaction of π+ and K+ Mesons with 13,15C and 15N Nuclei at Intermediate Energies within Glauber Diffraction Theory

The differential cross sections for the elastic scattering of π± and K+ mesons on 13,15C and 15N nuclei at intermediate energies were calculated within Glauber diffraction theory. The sensitivity of the calculated features to variations in the target wave functions and in the multiple-scattering contribution were analyzed. The contribution of double scattering were estimated.

Breakup of spatiotemporal pattern under electromagnetic radiation

Stable wave propagation is important for heart health, however, the electromagnetic radiation could affect normal signal propagation of heart, even make a sudden cardiac arrest. In this paper, the effect of electromagnetic radiation on the propagation of stable target wave generated by linear feedback control is studied in detail. It is confirmed that there are different transitions of electrical activities in cardiac tissue, which are transitions from target wave to spiral wave, some isolated islands of pattern waves coexisted, broken pattern and even the quiescent state, are generated when the electromagnetic field is imposed on the cardiac tissue in three ways. Furthermore, it is interesting to find there are different real affected regions, in which the electrical activities of nodes are destroyed, when the radiation signal is imposed on the cardiac tissue in different ways. It is also found the kinds of dynamical behaviors in the media are dependent on the real affected region. These results state that electromagnetic radiation could change the electrical activities, even destroy and suppress the wave propagation of wave source, and the ways of electromagnetic radiation imposed on the media are also important.

Collision and Radiative Rates for Infrared to Extreme Ultraviolet Lines of S iii

Abstract Electron excitation collision strengths for a wide range of transitions giving rise to infrared, optical, ultraviolet, and extreme ultraviolet lines of S iii have been calculated using the B-spline Breit–Pauli R-matrix method. The term-dependent non-orthogonal orbitals have been employed for the accurate representation of target wave functions and the electron plus S iii target scattering system. The multiconfiguration Hartree–Fock method has been utilized for the calculation of 198 S iii fine-structure level energies belonging to the , , , and 3s3p 25s configurations. The transition probabilities between fine-structure levels have also been calculated and compared with available other calculations. The close-coupling expansion includes these 198 fine-structure levels of S iii in the electron collision calculations. The effective collision strengths are calculated at electron temperatures in the range of 103–106 K for all possible transitions between the 198 fine-structure levels. The present calculation includes a larger number of levels in the close-coupling expansion and improved target description than previous calculations and should be useful for the analysis of measured spectra from various astrophysical objects. Comparison with other calculations is used to assess likely uncertainties in the existing collision and radiative rates for S iii. The collision and radiative rates are estimated to be accurate to about 20% or better for most main transitions of astrophysical importance.

Laser-Assisted (e, 2e) Collisions in the Symmetric/Asymmetric Coplanar Geometry

In this review, we present a comprehensive survey of laser-assisted (e, 2e) reactions. The influence of a laser field on the dynamics of (e, 2e) collisions in atomic hydrogen is analyzed in the symmetric and asymmetric coplanar geometries. Particular attention is devoted to the construction of the dressed (laser-modified) target wave functions, in both the initial and final states. The calculation is performed in the framework of Coulomb-Volkov-Born approximation, where the initial and final electrons are described by Volkov wave functions, while the interaction of the incident electron with the target atom is treated in the first and the second Born approximation. The state of the ejected electron is described by a Volkov/Coulomb-Volkov wave function. A detailed account is also given of the techniques we have used to evaluate the scattering amplitudes. The influence of the laser parameters (frequency, intensity, and direction of polarization) on the angular distribution of the ejected electron is discussed, and a number of illustrative examples are given. The structure of the triple differential cross section in the vicinity of resonances is also analyzed.

Photoionization of neutral iron from the ground and excited states

The B-spline R-matrix method is used to investigate the photoionization of neutral iron from the ground and excited states in the energy region from the ionization thresholds to 2 Ry. The multiconfiguration Hartree-Fock method in connection with adjustable configuration expansions and term-dependent orbitals is employed for an accurate representation of the initial states of Fe i and the target wave functions of Fe ii. The close-coupling expansion contains 261 LS states of Fe ii and includes all levels of the 3d64s,3d54s2,3d7,3d64p, and 3d54s4p configurations. Full inclusion of all terms from the principal configurations considerably changes both the low-energy resonance structure and the energy dependence of the background cross sections. Partial cross sections are analyzed in detail to clarify the most important scattering channels. Comparison with other calculations is used to place uncertainty bounds on our final photoionization cross sections and to assess the likely uncertainties in the existing data sets.

The CECO wave energy converter: Recent developments

CECO is a wave energy converter (WEC) of the oscillating body type equipped with an inclined PTO system and being developed at the Faculty of Engineering of the University of Porto. In the last years, several research studies have been performed to assess and to improve the performance of this WEC, using both physical model tests and numerical simulations. The main objective of this paper is reviewing the most significant findings of past research works, so as to provide a detailed overview about the present status of knowledge, but also presenting recent outcomes on the development of CECO and the next research steps. It discusses the influence of the PTO slope angle and damping on the efficiency of CECO harvesting wave energy and describes its energy conversion stages. Furthermore, the intra-annual variability of the wave resource (i.e., on a monthly basis) is considered in the analysis of the influence of the PTO inclination and local water depth at the deployment site on CECO captured energy and captured energy efficiency, along the North Atlantic coast of the Iberian Peninsula. The results have shown significant differences between the summer and winter months and also highlighted the fact that the initial geometry of this WEC is more suitable for the less energetic wave climates, characteristic of the southern locations of the case study area and of shallow waters. The conclusions obtained supported the design of an enhanced version of CECO, prepared for the more energetic stretches of the study area, which presents a hydrodynamic efficiency of more than twice the original one, for the target wave conditions.

Minimization of drift force on a floating cylinder by optimizing the flexural rigidity of a concentric annular plate

The deployment of suitable configurations of mutually interacting floating bodies for efficiently controlling their hydrodynamic interactions towards the reduction of the wave drift forces and, thus, of the mooring lines’ loads, has, nowadays, gained a great scientific interest. In this paper, the hydrodynamic behaviour of a floating cylinder and a concentric annular flexible plate is analysed in the frequency domain aiming at the minimization of the drift forces acting on the cylinder by optimizing the flexural rigidity of the plate. The diffraction/radiation problem is solved using a higher-order boundary element method. The analysis is implemented assuming that both floating bodies oscillate freely in heave, while for the plate, flexible modes are, additionally, considered for describing its structural deformations. The required modes shapes are determined in vacuum (“dry” mode superposition approach) through analytical expressions. The flexural rigidity of the plate, D, is optimized at a specific wave number using a real-coded genetic algorithm. Initially, results are compared with numerical results of other investigators for the case of two rigid concentric floating cylinders. Next, extended results are presented, focusing on the effect of D, including its optimum value, on various physical quantities describing the behaviour of both the cylinder and the plate. Contrary to the isolated cylinder, the presence of the plate introduces sharp peaks in the variation pattern of the drift force of the cylinder, bounded at specific wave numbers, where resonance of the seiche mode of water motion in the annular cavity or of specific flexible modes of the plate occurs. However, by reducing D to its optimum value, the cylinder’s drift force obtains practically zero values at the target wave number, due to an efficient improvement of the wave field in the annular cavity around the cylinder. Moreover, a great reduction of the drift force compared to the isolated cylinder is achieved in the subsequent high frequency range.

Incorporating irregular nonlinear waves in simulation of dropped cylindrical objects

This study investigates the use of second-order irregular waves for estimating loads on dropped objects. The theory for the irregular nonlinear wave model is integrated into a motion prediction model to simulate the falling process of a dropped cylinder under irregular waves. Through frequency analysis, the simulated irregular waves are transformed into wave spectrum by fast Fourier transform and compared with the target wave spectrum. A good agreement between simulated wave spectrum and target wave spectrum indicates the validity of the irregular nonlinear wave model. The effects of cylinder mass density, wave amplitude and initial wave phase on the trajectory and terminal conditions of dropped cylindrical object are systematically investigated, and the simulated results are compared with those induced by regular waves.

Stability of target waves in excitable media under electromagnetic induction and radiation

Local periodic stimulus can trigger stable pulse and target wave in the excitable media, the potential mechanism is that each cell is activated by continuous driving to keep pace with the external forcing. Indeed, local diversity in excitability and heterogeneity are induced when external forcing with diversity is applied on the media. When target wave is formed and propagated, the media will be modulated, e.g. it can emit electric signal from sinoatrial node and develops target wave in the cardiac tissue, and then the heartbeat is controlled completely. In fact, the distribution of electromagnetic field in the media is changed when external electric stimulus is applied on the media; therefore, the effect of electromagnetic induction becomes important during the information encoding and signal propagation. In this paper, the Morris–Lecar model is used to describe the local kinetic of the media and an induction current is considered thus the effect of electromagnetic induction can be described. Then the artificial heterogeneity is triggered to investigate the formation and development of target waves in the excitable media with electromagnetic induction and even radiation, which is described by using Gaussian white noise. Diversity in excitability and conductance of ion channels is considered, respectively, thus different kinds of artificial heterogeneity are developed to find the stability of target waves. It is found that the target wave encounters breakup with increasing of the intensity of electromagnetic radiation.

Entropy measurement of ordered patterns in neuronal network with repulsive coupling

Traveling waves, standing waves, and spiral waves occur spontaneously in the brain neural network in some brain states. The occurrence of these ordered spatiotemporal patterns is often related to some neurological diseases. However, the mechanisms behind the generation of the ordered pattern are not fully understood. How to quantitatively describe the nature of these spatiotemporal patterns still needs further exploring. In order to solve these problems, the Hindmarsh-Rose neuron model is used to study the dynamic behavior of the two-dimensional (2D) neuronal network with double-coupling layer, which is composed of nearest-neighbor excitatory coupling and long-range repulsive coupling layers and evolves from an initial state with a random phase distribution. An improved cluster entropy is proposed to describe the spatiotemporal pattern of the neuronal network. The numerical simulation results show that the repulsive coupling can either promote the formation of ordered patterns or suppress the formation of ordered patterns. When the repulsive coupling strength and excitatory coupling strength are appropriately selected, the chaotic network can spontaneously generate single spiral wave, multiple spiral wave, traveling wave, the coexistence of spiral wave and others wave state, the coexistence of target wave and others wave state, the coexistence of traveling wave and standing wave, etc. The probability with which spiral wave and traveling wave occur reach 0.4555 and 0.1667 respectively. The probability with which target wave and other states co-occur, and the probability with which the traveling wave and the standing wave co-occur, are 0.0389 and 0.1056, respectively. These ordered wave patterns and chaotic states can be distinguished by using the proposed cluster entropy. When the repulsive coupling strength is large enough, the neuronal network is generally in chaotic state. It is found by calculating cluster entropy that a large cluster can appear in the neuronal network when the excitatory coupling strength and repulsive coupling strength are both weak. These results can conduce to understanding the self-organization phenomena occurring in the experiments and also to treating various neurological diseases.

Electron-impact excitation of forbidden and allowed transitions in Fe ii

Extensive calculations are reported for electron collision strengths, rate coefficients, and transitions probabilities for a wide range of transitions in Fe ii. The collision strengths were calculated in the close-coupling approximation using the B-spline Breit-Pauli R-matrix method. The multiconfiguration Hartree-Fock method in connection with adjustable configuration expansions and a semiempirical fine-tuning procedure is employed for an accurate representation of the target wave functions. The energy correction was also used in the scattering calculations by adding to Hamiltonian matrices prior to transformation to intermediate coupling. The spin-orbit interaction term was added to the final Hamiltonian matrices in scattering calculations. The close-coupling expansion contains 340 fine-structure levels of Fe ii and includes all levels of the $3{d}^{6}4s$, $3{d}^{5}4{s}^{2}$, $3{d}^{7}$, and $3{d}^{6}4p$ configurations, plus a few lowest levels of the $3{d}^{5}4s4p$ configuration. The effective collision strengths are obtained by averaging the electron collision strengths over a Maxwellian distribution of velocities at electron temperatures in the range from ${10}^{2}$ to ${10}^{5}$ K and are reported for all possible inelastic transitions between the 340 fine-structure levels. The present results are more extensive than the previous calculations and considerably expand the existing data sets for Fe ii, allowing a more detailed treatment of the available measured spectra from different space observatories. Comparison with other calculations for collision rates and available experimental radiative rates is used to place uncertainty bounds on our collision strengths and to assess the likely uncertainties in the existing data sets.

Influence rules of ground-based laser active removing centimeter-sized orbital debris in LEO

The aim of this article is to describe the influence rules of ground-based laser irradiating centimeter-sized orbital debris in low earth orbits (LEO) by numerical simulations and experiments. A dynamic response model of ground-based laser irradiating centimeter-scale orbital debris in LEO was established by analyzing the influences of atmospheric turbulence and beam jitter. The spatial distribution rules of far field spot diameter and far field power density with transmission distance were investigated, the effects of divergence angle to integral spot were analyzed, and the relation of divergence angles and increment of far field spot diameters were also addressed within the turbulent atmosphere. Further, the spatial and temporal distribution rules of velocity and pressure in aluminum target and plasma shock wave were described, and the influence rules of impulse coupling coefficients with power density were also discussed. As a result, the effects of eccentricity and perigee altitude with the number of laser pulses and initial true anomaly were obtained to evaluate removing ability. Hence, it has very important significance for selecting efficient removal schemes to clean centimeter-sized orbital debris in LEO.

Field coupling-induced pattern formation in two-layer neuronal network

The exchange of charged ions across membrane can generate fluctuation of membrane potential and also complex effect of electromagnetic induction. Diversity in excitability of neurons induces different modes selection and dynamical responses to external stimuli. Based on a neuron model with electromagnetic induction, which is described by magnetic flux and memristor, a two-layer network is proposed to discuss the pattern control and wave propagation in the network. In each layer, gap junction coupling is applied to connect the neurons, while field coupling is considered between two layers of the network. The field coupling is approached by using coupling of magnetic flux, which is associated with distribution of electromagnetic field. It is found that appropriate intensity of field coupling can enhance wave propagation from one layer to another one, and beautiful spatial patterns are formed. The developed target wave in the second layer shows some difference from target wave triggered in the first layer of the network when two layers are considered by different excitabilities. The potential mechanism could be pacemaker-like driving from the first layer will be encoded by the second layer.

Electron-Impact Excitation of 51S – 51Po Resonance Transition in Sr Atom

Main aspects of a new version of the B-spline R-matrix (BSR) method, in which nonorthogonal orbitals are applied, have been described. The BSR approximation is used to calculate the resonance structure of integral cross-sections of the 51S - 51Po transition at the electron scattering by a strontium atom in the energy interval up to 10 eV. The multiconfiguration Hartree–Fock method with a nonorthogonal set of orbitals is employed to accurately represent the target wave functions. The close-coupling expansion included 31 bound states of a neutral strontium atom ranging from the ground state to the 5s5f 1Fo one. The calculated cross-sections are in good agreement with available experimental data and can be exhaustively interpreted. The structure of a resonance feature in the e-Sr scattering cross-sections at about 4 eV is discussed.

Real time relationship between individual finger force and grip exertion on distal phalanges in linear force following tasks

Individual finger force (FF) in a grip task is a vital concern in rehabilitation engineering and precise control of manipulators because disorders in any of the fingers will affect the stability or accuracy of the grip force (GF). To understand the functions of each finger in a dynamic grip exertion task, a GF following experiment with four individual fingers without thumb was designed. This study obtained four individual FFs from the distal phalanges with a cylindrical handle in dynamic GF following tasks. Ten healthy male subjects with similar hand sizes participated in the four-finger linear GF following tasks at different submaximal voluntary contraction (SMVC) levels. The total GF, individual FF, finger force contribution, and following error were subsequently calculated and analyzed. The statistics indicated the following: 1) the accuracy and stability of GF at low %MVC were significantly higher than those at high SMVC; 2) at low SMVC, the ability of the fingers to increase the GF was better than the ability to reduce it, but it was contrary at high SMVC; 3) when the target wave (TW) was changing, all four fingers strongly participated in the force exertion, but the participation of the little finger decreased significantly when TW remained stable; 4) the index finger and ring finger had a complementary relationship and played a vital role in the adjustment and control of GF. The middle finger and little finger had a minor influence on the force control and adjustment. In conclusion, each of the fingers had different functions in a GF following task. These findings can be used in the assessment of finger injury rehabilitation and for algorithms of precise control.

Spontaneous formation of ordered waves in chaotic neuronal network with excitory-inhibitory connections

Spiral waves are a particular form of propagating waves, which rotate around a center point known as a rotor. Spiral waves have been found to play an important role in cardiac arrhythmia. Using voltage-sensitive dye imaging, one can find that spiral waves and plannar waves can occur in the mammalian cortex in vivo. The electrode array conduces to discovering that the seizures may manifest as recurrent spiral waves which propagate in the neocortex. However, the formation mechanism of the ordered waves and its potential function in the nervous system remain uncertain. In order to understand the formation mechanism of the ordered waves, we construct a double-layer two-dimensional -network of neuron, which is composed of nearest-neighbor excitatory coupling and long-range inhibitory coupling layers. The inhibitory grid points account for 25% of total number of grid points in the network. We propose a modified Hindmarsh-Rose neuron model to study whether differently ordered waves can occur spontaneously in the chaotic neuronal network evolving from the initial state with a random phase distribution. The numerical simulation results show that when the inhibitory coupling strength is small the spontaneous formation of ordered wave does not generally appear in the network. The larger inhibitory coupling strength, the more easily the system generates an ordered wave for sufficiently large strength of excitatory coupling. The appearance of differently ordered waves is closely related to the initial state of the system and coupling strength. As the excitatory and inhibitory coupling strengths are appropriately selected, the system can spontaneously generate the maze pattern, planar wave, single spiral wave, multiple spiral wave, paired spiral waves rotating in the opposite directions, two-arm spiral wave, target wave and inward square wave and so on. The probability for spontaneously forming a single spiral wave is far less than that for forming a small spiral wave. The occurrence probabilities of spiral wave, maze pattern and inward square wave reach 27.5%, 21.5% and 10%, respectively. The maze pattern is composed of many plane waves with different propagation directions. The occurrence probabilities of other ordered waves are quite small. These results conduce to understanding the self-organization phenomena occurring in the cerebral cortex.

Free-Surface Time-Series Generation for Wave Energy Applications

Finite-length, numerical simulations of Gaussian seas are widely used in the wave energy sector. The most common method consists of adding up harmonic sinusoidal components, with random phases and deterministic amplitudes derived from the target wave spectrum [deterministic amplitude scheme (DAS)]. In another approach, the component amplitudes are chosen randomly with a variance depending on the spectrum [random amplitude scheme (RAS)]. It is now generally accepted that only the latter method reproduces the true statistical properties of a Gaussian sea. Compared to previous works, this study clarifies the exact nature of the “statistical properties” that should be represented in the simulation process. Further analysis is carried out to address unanswered questions highlighted in the existing literature, especially with respect to the statistical relationships between discrete successive simulation points, and the probability law governing the average power estimator of a wave energy converter (WEC) simulated with the generated wave time series. It is shown that RAS exactly reflects how the WEC performance, considered over a finite duration, varies with respect to its long-term average, whereas DAS has the advantage of providing accurate estimates of the long-term average values using fewer, or shorter, simulations; in particular, it is demonstrated that only one simulation is sufficient when the WEC model is linear. Furthermore, it is shown why alternative methods, based on nonharmonic superposition of sinusoids, are not recommended. The effects of the simulation method (RAS or DAS) upon the statistics of individual oscillations in the time domain are also explored experimentally. Finally, a table is provided that gives recommendations, depending on the objective of the simulations.

Spiral wave breakup manner in the excitable system with early afterdepolarizations

Early afterdepolarization (EAD) is an important cause of lethal ventricular arrhythmias in heart failure because afterdepolarizations can promote the transition from ventricular tachycardia to fibrillation, which is related to the transition from spiral wave to spatiotemporal chaos. However, it remains unclear about how the EAD results in the breakup of spiral wave. In this paper, we explore the manner of spiral wave breakup induced by EADs under evenly distributed cells. The two-dimensional tissue is simulated with the Greenberg-Hasting cellular automaton model. The normal cells and aging cells are introduced into the model, in which the EAD only occurs in aging cells and can excite the resting cells. The numerical results show that the EAD can produce backward waves as well as forward waves. The EAD has no influence on the behavior of spiral wave in a few cases. The ratio of the number of unaffected spiral waves to the number of all tests is about 26.4%. The EAD can have various effects on spiral wave in other cases. The small influences on spiral wave are that the EAD leads to the meander, drift, and the deformation of spiral wave. The serious influences on spiral wave are that the EAD results in the disappearance and breakup of spiral wave. We find that spiral wave can disappear through the conduction block and transition from spiral wave to target wave. We observe the eight kinds of spiral wave breakups in connection with the excitation of EADs, such as symmetry breaking-induced breakup, nonsymmetry breaking-induced breakup, asymmetric excitation-induced breakup, conduction block-induced breakup, double wave-induced breakup, etc. Spiral wave generally breaks up into multiple spiral waves and spatiotemporal chaos. The ratio of the number of spiral wave breakup to the number of all tests is about 13.8%. However, the ratio of spiral wave breakup can reach about 32.4% under appropriately chosen parameters. The results are basically consistent with the survey results of arrhythmia-induced death rate. Furthermore, we also find that the excitation of EAD can prevent the spiral wave from disappearing and promote the breakup of spiral wave. The physical mechanisms underlying those phenomena are also briefly analyzed.

Numerical investigation on antispiral and antitarget wave in reaction diffusion system

In this paper, the antispiral and antitarget wave patterns in two-dimensional space are investigated numerically by Brusselator model with three components. The formation mechanism and spatiotemporal characteristics of these two waves are studied by analyzing dispersion relation and spatiotemporal variation of parameters of model equation. The influences of equation parameters on antispiral and antitarget wave are also analyzed. Various kinds of multi-armed antispiral are obtained, such as the two-armed, three-armed, four-armed, five-armed, and six-armed antispirals. The results show that antispirals may exist in a reaction-diffusion system, when the system is in the Hopf instability or the vicinity of wave instability. In addition to the above two types of instabilities, there is the Turing instability when the antitarget wave emerges. They have the periodicity in space and time, and their propagation directions are from outside to inward (the phase velocity vp 0), just as the incoming waves disappear in the center. The rotation directions of the various antispiral tips are the same as those of the waves, which can be rotated clockwise or anticlockwise, and the rotation period of wave-tip increases with the number of arms. Furthermore, it is found that the collision sequence of the multi-armed antispiral tip is related to the rotation direction of the wave-tip. With the increase of the number of anti-spiral arms, not only the dynamic behavior of the wave-tip turns more complex, but also the radius of the center region increases. Due to the influence of perturbation and boundary conditions, the multi-armed antispiral pattern can lose one arm and become a new antispiral pattern in the rotating process. Under certain conditions, it can be realized that the single-armed antispiral wave transforms into an antitarget wave. It is found that the change of control parameters of a and b can induce the regular changes of the space scale of antispiral waves, and antispiral waves gradually turn sparse with the increase of a, on the contrary, they gradually become dense with the increase of b. When the parameter of D_w exceeds a critical value, the propagation direction of wave is changed, and the system can produce the transformation from antispiral wave to spiral wave and from antitarget wave to target wave.

Transition and Electron Impact Excitation Collision Rates for O iii

Abstract Transition probabilities, electron excitation collision strengths, and rate coefficients for a large number of O iii lines over a broad wavelength range, from the infrared to ultraviolet, have been reported. The collision strengths have been calculated in the close-coupling approximation using the B-spline Breit–Pauli R-matrix method. The multiconfiguration Hartree–Fock method in combination with B-spline expansions is employed for an accurate representation of the target wave functions. The close-coupling expansion contains 202 O2+ fine-structure levels of the , , , and configurations. The effective collision strengths are obtained by averaging electron excitation collision strengths over a Maxwellian distribution of velocities at electron temperatures ranging from 100 to 100,000 K. The calculated effective collision strengths have been reported for the 20,302 transitions between all 202 fine-structure levels. There is an overall good agreement with the recent R-matrix calculations by Storey et al. for the transitions between all levels of the ground configuration, but significant discrepancies have been found with Palay et al. for transitions to the 1 S 0 level. Line intensity ratios between the optical lines arising from the − 1 D 2 transitions have been compared with other calculations and observations from the photoionized gaseous nebulae, and good agreement is found. The present calculations provide the most complete and accurate data sets, which should allow a more detailed treatment of the available measured spectra from different ground and space observatories.