Fuel compression in the magnetized cylindrical implosion driven by a gold tube heated by heavy ion beams

A magnetized cylindrical target composed of a gold tube filled with deuterium-tritium fuel plasma at low density is studied numerically in the present paper.A shock wave is produced when a heavy ion beam heats the gold along the direction of the magnetic field.The density peak of the shock wave increases with the increase in time and it propagates in the-r direction in the cylindrical tube.It seems that this wave is the supermagnetosonic wave.It is found that the Mach number M is between 6.96 and 19.19.The density peak of the shock wave increases as the intensity of the heavy ion beam increases.Furthermore,the density peak of the shock wave increases as the external magnetic field increases.

Modulational instability of the coupled waves between fast magnetosonic wave and slow Alfvén wave in the laser–plasma interaction

By performing modulational instability analysis of the the nonlinear coupled dimensionless equations between a fast magnetosonic wave(FMSW)propagating obliquely with the magneticfield and a low-frequency slow Alfvén wave(SAW),we obtain the dispersion relation of the perturbation wave.The growth rate of the perturbation wave is obtained.It is found that the growth rate increases as background magnetic field increases,which is in agreement with that reported by Tiwary et al(2016 Phys.Plasmas 23122307).A critical perturbation wave number is found.When the perturbation wave number is greater than or equal to the critical value,the growth rate is positive and it increases as the perturbation wave number increases,while the wave is stable.The maximum growth rate is reached when the frequency of the FMSW is half of the ion cyclotron frequency.The minimum growth rate is reached when the propagation direction of the perturbation wave is the same as that of the FMSW.

Investigation of the fast magnetosonic wave excited by the Alfvén wave phase mixing by using the Hall–MHD model in inhomogeneous plasma

The inhomogeneity is introduced by a nonzero density gradient which separates the plasma into two different regions where plasma density are constant.The Alfvén waves,the phase mixing and the fast magnetosonic wave are excited by the boundary condition in inhomogeneous magnetized plasma.By using the Hall–magnetohydrodynamics(MHD)model,it is found that there are Alfvén waves in the homogeneous regions,while the phase mixing appears in the inhomogeneous region.The interesting result is that a fast magnetosonic wave is excited in a different direction which has a nonzero angle between the wave propagation direction and the direction of the background magnetic field.The dependence of the propagation direction of the excited fast magnetosonic wave and its strength of the magnetic field on the plasma parameters are given numerically.The results show that increasing both the driving frequency and the ratio of magnetic pressure to thermal pressure will increase the acceleration of the electrons.The electron acceleration also depends on the inhomogeneity parameters.

Investigation of the confinement of high energy non-neutral proton beam in a bent magnetic mirror

By using the particle-in-cell(PIC)simulation method,we studied how the proton beam is confined in a bent magnetic mirror.It is found that the loss rate of the charged particles in a bent mirror is less than that in the axi-symmetric mirror.For a special bent mirror with the deflection angle of the coilsα=45°,it is found that the loss rate reaches maximum value at certain ion number density where the ion electrostatic oscillation frequency is equal to the ion cyclotron frequency.In addition,the loss rate is irrelevant to the direction of the proton beam.Our results may be helpful to devise a mirror.In order to obtain the least loss rate,we may choose an appropriate deflection angle,and have to avoid a certain ion number density at which the ion electrostatic oscillation frequency is equal to the ion cyclotron frequency.

Nanoparticle-strengthened Ni_(2)CoCrNb_(0.2)medium-entropy alloy with an ultrastrong cryogenic yield strength fabricated by additive manufacturing

To improve the yield strength of metallic materials at low temperatures,a strategy of combining the calculation of phase diagrams(CALPHAD)technique with the overall valence electron concentration(OVEC)principle is applied,and a Ni_(2)CoCrNb_(0.2)medium-entropy alloy(MEA)with D022 superlattice(noted as theγ″phase)is designed.Bulk MEA samples without defects were successfully fabricated using laser additive manufacturing(AM),followed by solution treatment at 1200℃for 1 h and then aging at 650℃for 120 h.The nanoscaleγ″phase precipitated.The tensile results indicated that the MEA had superior yield strengths of∼1180 MPa and∼1320 MPa and tensile strengths of∼1335 MPa and∼1552 MPa at 293 K and 77 K,respectively.The yield strength obtained was superior to that of currently reported medium/high-entropy alloys and typical advanced cryogenic steel.The mechanical properties of the Ni_(2)CoCrNb_(0.2)MEA demonstrated a strong temperature dependence,and the increased yield strength was mainly attributed to the increase in lattice friction stress at low temperatures.This research provides a new strategy for producing materials with ultrastrong cryogenic yield strengths by AM.

中药白及在口腔疾病中的研究与应用

白及作为我国传统的中药材,分布广泛、价廉易得。随着中医药的蓬勃发展,白及在临床医学上的应用也更为深入,包括抗菌、抗肿瘤、治疗消化道溃疡、胃黏膜病变和体内外出血等。本文对白及的药理特性、化学成分做一总结,同时分析各成分在治疗中的机制和通路,着重归纳整理了白及在口腔疾病领域的应用,包括口腔黏膜类疾病、龋病、髓腔内屏障材料和牙周组织工程支架材料等,证明了白及无论是单味用药还是配伍用药,都能依靠其自身特性发挥重要功效,为进一步推广白及在口腔疾病治疗中的研究应用提供参考。

Selective enforcement of regulation

Regulatory agencies may,whether outside of set rules or within their discretion,depart from the original goals or principles set for enforcing the rules,which we term selective enforcement.Taking China,a country in transition,as an example,and using cases and large-sample tests,we present empirical evidence of selective enforcement.The results show that the China Securities Regulatory Commission(CSRC) takes into account whether companies violating the rules have a state-owned background and the strength of that background when investigating and punishing non-compliance.After controlling for the degree of violation,state-owned-enterprises(SOEs) are punished less severely than private companies;and the higher the hierarchy of the SOE in question,the less severe the punishment.It also takes longer for SOEs to be punished.We also find that companies that violate the rules less seriously have a greater tendency to apply for refinancing than those that violate the rules more seriously.This may be because the severity of the violation can affect listed companies' expectations of obtaining refinancing.The analysis and conclusions of this study prove useful in understanding the causes and consequences of selective enforcement in transition economies.