Calculation and prediction of divertor detachment via impurity seeding by using one-dimensional model

Achieving the detachment of divertor can help to alleviate excessive heat load and sputtering problems on the target plates,thereby extending the lifetime of divertor components for fusion devices.In order to provide a fast but relatively reliable prediction of plasma parameters along the flux tube for future device design,a one-dimensional(1D)modeling code for the operating point of impurity seeded detached divertor is developed based on Python language,which is a fluid model based on previous work(Plasma Phys.Control.Fusion 58045013(2016)).The experimental observation of the onset of divertor detachment by neon(Ne)and argon(Ar)seeding in EAST is well reproduced by using the 1D modeling code.The comparison between the 1D modeling and two-dimensional(2D)simulation by the SOLPS-ITER code for CFETR detachment operation with Ne and Ar seeding also shows that they are in good agreement.We also predict the radiative power loss and corresponding impurity concentration requirement for achieving divertor detachment via different impurity seeding under high heating power conditions in EAST and CFETR phase II by using the 1D model.Based on the predictions,the optimized parameter space for divertor detachment operation on EAST and CFETR is also determined.Such a simple but reliable 1D model can provide a reasonable parameter input for a detailed and accurate analysis by 2D or three-dimensional(3D)modeling tools through rapid parameter scanning.

Flat Band and η-Pairing States in a One-Dimensional MoiréHubbard Model

A Moirésystem is formed when two periodic structures have a slightly mismatched period,resulting in unusual strongly correlated states in the presence of particle-particle interactions.The periodic structures can arise from the intrinsic crystalline order and periodic external field.We investigate a one-dimensional Hubbard model with periodic on-site potential of period n_(0),which is commensurate to the lattice constant.For large n_(0),the exact solution demonstrates that there is a midgap flat band with zero energy in the absence of Hubbard interaction.Each Moiréunit cell contributes two zero energy levels to the flat band.In the presence of Hubbard interaction,the midgap physics is demonstrated to be well described by a uniform Hubbard chain in which the effective hopping and on-site interaction strength can be controlled by the amplitude and period of the external field.Numerical simulations are performed to demonstrate the correlated behaviors in the finite-sized Moiré Hubbard system,including the existence of an η-pairing state and bound pair oscillation.This finding provides a method to enhance the correlated effect by a spatially periodic external field.

Chimera states of phase oscillator populations with nonlocal higher-order couplings

The chimera states underlying many realistic dynamical processes have attracted ample attention in the area of dynamical systems.Here, we generalize the Kuramoto model with nonlocal coupling incorporating higher-order interactions encoded with simplicial complexes.Previous works have shown that higher-order interactions promote coherent states.However, we uncover the fact that the introduced higher-order couplings can significantly enhance the emergence of the incoherent state.Remarkably, we identify that the chimera states arise as a result of multi-attractors in dynamic states.Importantly, we review that the increasing higher-order interactions can significantly shape the emergent probability of chimera states.All the observed results can be well described in terms of the dimension reduction method.This study is a step forward in highlighting the importance of nonlocal higher-order couplings, which might provide control strategies for the occurrence of spatial-temporal patterns in networked systems.

Oscillatory squeeze flow through an Oldroyd-B fluid-saturated porous layer

This study deals with the analytical investigation of oscillatory squeeze film flow through a Brinkman viscoelastic Oldroyd-B fluid-saturated porous layer subject to two vertically harmonically oscillatory disks.The validity of the present proposed analytical solutions is first demonstrated for the Newtonian fluids when bothΛ_(1)andΛ_(2)tend to zero by comparison with the previous literature.Results demonstrate that an increase in the elasticity parameterΛ_(1)correlates with a rise in axial velocities,indicating that the relaxation timeΛ_(1)facilitates enhanced squeeze flow.In the case of squeeze film flow in porous layers,low oscillating frequencies exert minimal effects on axial velocities,independent of variations in the viscoelasticity parameterΛ_(1).However,at higher oscillating frequencies,axial velocities escalate with increasing the viscoelasticity parameterΛ_(1).Furthermore,the retardation timeΛ_(2)of the viscoelastic fluid shows no significant effect on the axial velocity,regardless of oscillating frequency changes in both pure fluids and porous layers.

Study of thermal decoherence of harmonic oscillators

The thermal decoherence of harmonic oscillators is investigated here.The quantum system presented here is a one-dimensional oscillator with angular frequency,which is surrounded by a thermal bath of environmental oscillators.There are various environmental oscillators with different angular frequency(below an ultraviolet cutoff).At the beginning,the quantum system is a pure state and the environmental oscillators are in thermodynamic equilibrium with temperature.After a period,the system-environment interactions inspire significant decoherence of the quantum state.Such decoherence is displayed by explicit calculations of the purity and von Neumann entropy of the quantum system.It is worth noting that the decoherence could be significant even in the weak coupling and low temperature case due to the large amount of environmental degrees of freedom.Since the decoherence process is inspired between the quantum system and an ordinary thermal environment here,the thermal decoherence result is quite general.

Numerical Investigations on the Resonance Errors of Multiscale Discontinuous Galerkin Methods for One-Dimensional Stationary Schrödinger Equation

In this paper,numerical experiments are carried out to investigate the impact of penalty parameters in the numerical traces on the resonance errors of high-order multiscale discontinuous Galerkin(DG)methods(Dong et al.in J Sci Comput 66:321–345,2016;Dong and Wang in J Comput Appl Math 380:1–11,2020)for a one-dimensional stationary Schrödinger equation.Previous work showed that penalty parameters were required to be positive in error analysis,but the methods with zero penalty parameters worked fine in numerical simulations on coarse meshes.In this work,by performing extensive numerical experiments,we discover that zero penalty parameters lead to resonance errors in the multiscale DG methods,and taking positive penalty parameters can effectively reduce resonance errors and make the matrix in the global linear system have better condition numbers.

Oscillatory Dynamics of a Spherical Solid in a Liquid in an Axisymmetric Variable Cross Section Channel

The dynamics of a solid spherical body in an oscillating liquid flow in a vertical axisymmetric channel of variable cross section is experimentally studied.It is shown that the oscillating liquid leads to the generation of intense averaged flows in each of the channel segments.The intensity and direction of these flows depend on the dimensionless oscillating frequency.In the region of studied frequencies,the dynamics of the considered body is examined when the primary vortices emerging in the flow occupy the whole region in each segment.For a fixed frequency,an increase in the oscillation amplitude leads to a phase-inclusion holding effect,i.e.,the body occupies a quasi-stationary position in one of the cells of the vertical channel,while oscillating around its average position.It is also shown that the oscillating motion of a liquid column generates an averaged force acting on the body,the magnitude of which depends on the properties of the body and its position in the channel.The quasi-stationary position is determined by the relative density and size of the body,as well as the dimensionless frequency.The behavior of the body as a function of the amplitude and frequency of fluid oscillation and relative size is discussed in detail.Such findings may be used in the future to control the position of a phase inclusion and/or to strengthen mass transfer effects in a channel of variable cross section by means of fluid oscillations.

Linearization of Intrinsically Nonlinear Oscillators

We show that an intrinsically nonlinear oscillator can always be transformed into a linear or harmonic oscillator by addition of a constant force, which shifts the equilibrium position of the oscillator.

Dynamics of a Quantum Dissipative System Coupled with an Oscillator

We study the dynamics of a quantum dissipative system. Besides its linear coupling with a harmonic bath modelling the dissipation, we suppose that it is coupled with an oscillator with an interaction of the form s 2 x 2 . In our study, we integrate over the bath and the oscillator, extract the corresponding influence functionals and then solve the system’s sign problem. We apply the theory to the case of a double well and study the time evolution of the expectation value of the position.

Experimental and simulation study on shear stress-induced erythrocyte damage based on vortex oscillator

Background:Shear stress-induced erythrocyte damage,namely hemolysis,is an important problem in the development of blood-contacting medical devices such as mechanical circulatory support devices.Computational fluid dynamics simulation combined with hemolysis prediction models have been widely used to predict hemolysis.With the development of hemolysis prediction models,the new hemolysis prediction model requires more experimental data to verify.In addition,the difference of in vitro blood-shearing device also affect the accuracy of hemolysis prediction.Methods:To address these problems,a new in vitro blood-shearing device(vortex oscillator)was used to further verify the accuracy of the hemolysis prediction models,and to guide the optimal design of blood-contacting medical devices such as mechanical circulatory support devices.Firstly,the flow field information such as wall stress and velocity of the vortex oscillator under different speeds was analyzed.Secondly,different hemolysis prediction models were used to calculate hemolysis,and the predicted data was compared with the experimental data.Results and Conclusion:In this study,the flow field information inside the vortex oscillator at high rotational speeds was systematically investigated,and the prediction of hemolysis was carried out.The results showed that the predicted data of hemolysis was significantly different from the experimental data,which indicated that it was urgent to establish a standardized in vitro blood-shearing platform to provide a reference for accurate hemolysis prediction.

Prediction of one-dimensional CrN nanostructure as a promising ferromagnetic half-metal

Searching for one-dimensional(1D)nanostructure with ferromagnetic(FM)half-metallicity is of significance for the development of miniature spintronic devices.Here,based on the first-principles calculations,we propose that the 1D CrN nanostructure is a FM half-metal,which can generate the fully spin-polarized current.The ab initio molecular dynamic simulation and the phonon spectrum calculation demonstrate that the 1D CrN nanostructure is thermodynamically stable.The partially occupied Cr-d orbitals endow the nanostructure with FM half-metallicity,in which the half-metallic gap(?s)reaches up to 1.58 eV.The ferromagnetism in the nanostructure is attributed to the superexchange interaction between the magnetic Cr atoms,and a sizable magnetocrystalline anisotropy energy(MAE)is obtained.Moreover,the transverse stretching of nanostructure can effectively modulate?s and MAE,accompanied by the preservation of half-metallicity.A nanocable is designed by encapsulating the CrN nanostructure with a BN nanotube,and the intriguing magnetic and electronic properties of the nanostructure are retained.These novel characteristics render the 1D CrN nanostructure as a compelling candidate for exploiting high-performance spintronic devices.

Stochastic Resonance in a Single-Ion Nonlinear Mechanical Oscillator

Stochastic resonance is a counterintuitive phenomenon amplifying the weak periodic signal by application of external noise.We demonstrate the enhancement of a weak periodic signal by stochastic resonance in a trappedion oscillator when the oscillator is excited to the nonlinear regime and subject to an appropriate noise.Under the full control of the radio-frequency drive voltage,this amplification originates from the nonlinearity due to asymmetry of the trapping potential,which can be described by a forced Duffing oscillator model.Our scheme and results provide an interesting possibility to make use of controllable nonlinearity in the trapped ion,and pave the way toward a practical atomic sensor for sensitively detecting weak periodic signals from real noisy environment.

Straightforward Method for Nonlinear Oscillators

It is challenging to predict the frequency property of a nonlinear vibration system conveniently and efficiently.Especially,an invalid or physically irrelevant result might be obtained by some advanced methods.Therefore,predicting the frequency lacks an expedient and efficient method.This challenge is addressed by developing a straightforward and effective frequency formulation that reliably predicts the frequency-amplitude relationship.This study provides a one-step approach which can fast determine the periodic properties of any conservative oscillators and also provides a reference for other similar studies.

An Investigation of Bubble Motion in the Fluidic Oscillator

Enhanced gas-liquid mass transfer is significant for the desulfurization and denitration of ship exhaust gases.As a fluid device,the special structure of the fluidic oscillator generates self-excited oscillations that can effectively enhance the mass transfer process of gas-liquid.But there are few studies on the internal gas-liquid flow.The transportation of individual bubbles in the fluidic oscillator was investigated by a high-speed camera and digital image analysis.The results show that the bubble experienced a significant deceleration process in the chamber region of the fluidic oscillator.In addition,the maximum bubble offset increased with the diameter of the initial bubble.The trajectory of the bubble showed zigzag movement due to the deflecting oscillation of the fluidic oscillator.At the same time,the deformation of the bubble was intensified by the deflecting oscillation.The deformation ratio of the bubble increased with the increase of Reynolds number.By studying the transport process of a single bubble in the fluid oscillator,it is considered that the fluid oscillator has the potential to be a new bubble generator.

On the Relativistic Harmonic Oscillator

The relativistic harmonic oscillator represents a unique energy-conserving oscillatory system. The detailed characteristics of the solution of this oscillator are displayed in both weak- and extreme-relativistic limits using different expansion procedures, for each limit. In the weak-relativistic limit, a Normal Form expansion is developed, which yields an approximation to the solution that is significantly better than in traditional asymptotic expansion procedures. In the extreme-relativistic limit, an expansion of the solution in terms of a small parameter that measures the proximity to the limit (v/c) →1 yields an excellent approximation for the solution throughout the whole period of oscillations. The variation of the coefficients of the Fourier expansion of the solution from the weak- to the extreme-relativistic limits is displayed.

Stability and multistability of synchronization in networks of coupled phase oscillators

Coupled phase oscillators usually achieve synchronization as the coupling strength among oscillators is increased beyond a critical value. The stability of synchronous state remains an open issue. In this paper, we study the stability of the synchronous state in coupled phase oscillators. It is found that numerical integration of differential equations of coupled phase oscillators with a finite time step may induce desynchronization at strong couplings. The mechanism behind this instability is that numerical accumulated errors in simulations may trigger the loss of stability of the synchronous state.Desynchronization critical couplings are found to increase and diverge as a power law with decreasing the integral time step. Theoretical analysis supports the local stability of the synchronized state. Globally the emergence of synchronous state depends on the initial conditions. Other metastable ordered states such as twisted states can coexist with the synchronous mode. These twisted states keep locally stable on a sparse network but lose their stability when the network becomes dense.

Mass-Oscillators as Information Memories of Action

In the theory of physical information, the physical phenomena of electromagnetism, quantum mechanics and gravity can be described by means of the action as information enclosed in four dimensional structures with oscillator properties, under the conditions of the Hamilton principle. The present report shows that it is also possible to simulate the behaviour of the mass under these conditions. As a result, among other things, the statements are obtained that the mass is stored virtual action;the rest frame of elementary objects and the inertia of matter are caused by the action stored in the mass oscillators.

Oscillator strength and cross section study of the valence-shell excitations of NO_(2) by fast electron scattering

Oscillator strengths and cross sections of the valence-shell excitations in NO_(2)are of great significance in testing the theoretical calculations and monitoring the state of the ozone layer in the earth’s atmosphere. In the present work, the generalized oscillator strengths of the valence-shell excitations in NO_(2)were obtained based on the fast electron scattering technique at an incident electron energy of 1.5 ke V and an energy resolution of about 70 me V. By extrapolating the generalized oscillator strengths to the limit of a zero squared momentum transfer, the optical oscillator strengths for the dipole-allowed transitions have been obtained, which provide an independent cross check to the previous experimental results. Based on the BE-scaling method, the corresponding integral cross sections have also been derived systematically from the excitation threshold to 5000 eV. The present dynamic parameters can provide the fundamental spectroscopic data of NO_(2)and have important applications in the studies of atmospheric science. The datasets presented in this paper, including the GOSs, OOSs and ICSs, are openly available at https://doi.org/10.57760/sciencedb.j00113.00156.

Size effect on light propagation modulation near band edges in one-dimensional periodic structures

Periodic photonic structures can provide rich modulation in propagation of light due to well-defined band structures.Especially near band edges,light localization and the effect of near-zero refractive index have attracted wide attention.However,the practically fabricated structures can only have finite size,i.e.,limited numbers of periods,leading to changes of the light propagation modulation compared with infinite structures.Here,we study the size effect on light localization and near-zero refractive-index propagation near band edges in one-dimensional periodic structures.Near edges of the band gap,as the structure's size shrinks,the broadening of the band gap and the weakening of the light localization are discovered.When the size is small,an added layer on the surface will perform large modulation in the group velocity.Near the degenerate point with Dirac-like dispersion,the zero-refractive-index effects like the zero-phase difference and near-unity transmittance retain as the size changes,while absolute group velocity fluctuates when the size shrinks.

Experimental research based on a C-band compact transit-time oscillator with a novel diode loading an embedded soft magnetic material and shielding structure

In order to reduce the external magnetic field and improve the conversion efficiency of high-power microwave generation devices with low external magnetic field,a novel diode with an embedded soft magnetic and shielding structure is proposed.The soft magnetic material is designed to enhance the local magnetic field in the diode region.Moreover,the diode applies a shielding structure which can reduce the radial electric field.From simulation research,it is found that the emission and transmission quality of the electron beam with low magnetic field is greatly improved when loading this diode.Through simulation research,it is verified that the diode can increase the conversion efficiency of the transit-time oscillator(TTO)from 30%to 36.7%.In our experimental study,under the conditions of a diode voltage of 540 kV and a current of 10.5 kA,the output microwave power is 1.51 GW when loading the novel diode and the microwave frequency is 4.27 GHz when an external guiding magnetic field of 0.3 T is applied.The corresponding conversion efficiency is improved from 20.0%to 26.6%,which is 6.6%higher than that of a device loaded with a conventional diode.Our experiments have verified that this novel diode can effectively improve the conversion efficiency of high-power microwave sources operating with low magnetic field,and contribute to the miniaturization and compactness of high-power microwave devices.