Model of self-generated magnetic field generation from relativistic laser interaction with solid targets

Generation of self-generated annular magnetic fields at the rear side of a solid target driven by relativistic laser pulse is investigated by using theoretical analysis and particle-in-cell simulations.The spatial strength distribution of magnetic fields can be accurately predicted by calculating the net flow caused by the superposition of source flow and return flow of hot electrons.The theoretical model established shows good agreement with the simulation results,indicating that the magnetic-field strength scales positively to the temperature of hot electrons.This provides us a way to improve the magnetic-field generation by using a micro-structured plasma grating in front of the solid target.Compared with that for a common flat target,hot electrons can be effectively heated with the well-designed grating size,leading to a stronger magnetic field.The spatial distribution of magnetic fields can be modulated by optimizing the grating period and height as well as the incident angle of the laser pulse.

Effect of sharp vacuum-plasma boundary on the electron injection and acceleration in a few-cycle laser driven wakefield

The electron injection and acceleration driven by a few-cycle laser with a sharp vacuum-plasma boundary have been investigated through three-dimensional(3D)particle-in-cell simulations.It is found that an isotropic boundary impact injection(BII)first occurs at the vacuum-plasma boundary,and then carrier-envelope-phase(CEP)shift causes the transverse oscillation of the plasma bubble,resulting in a periodic electron self-injection(SI)in the laser polarization direction.It shows that the electron charge of the BII only accounts for a small part of the total charge,and the CEP can effectively tune the quality of the injected electron beam.The dependences of laser intensity and electron density on the total charge and the ratio of BII charge to the total charge are studied.The results are beneficial to electron acceleration and its applications,such as betatron radiation source.

支撑喉镜下激光补充切除非完整剥离的残余声带囊肿21例

目的探讨支撑喉镜下激光切除声带囊肿囊壁的疗效。方法21例声带囊肿患者采用微瓣剥离技术分离破裂,再采用支撑喉镜下激光切除声带囊肿囊壁,于术后2周、2个月和6个月应用动态喉镜观察声带形态、声门闭合情况及患者声嘶改善情况。结果21例患者手术顺利,术后即感声嘶改善,无出血,无窒息。术后2周复查,16例患者恢复良好;5例患者声音仍有嘶哑,声带稍有水肿,边缘黏膜欠平整。术后8周复查,20例患者恢复或接近正常嗓音,喉镜检查声带边缘平整、光滑;1例患者禁声不佳,仍有嘶哑,声带前中1/3处呈小结样微隆起。随访半年,仍有嘶哑的1例患者,伴声带小结,自觉声音能接受;无1例复发。1例左侧囊肿术后5个月对侧出现囊肿,经微瓣技术完整摘除后无复发。结论采用支撑喉镜下激光补充切除非完整剥离的残余声带囊肿囊壁治疗声带囊肿,可彻底切除病变,又能很好地保留黏膜的完整性,利于发声功能恢复,是治疗破裂声带囊肿较好的手术方式。

Simulations on the multi-shell target ignition driven by radiation pulse in Z-pinch dynamic hohlraum

We present the first simulation results of a multi-shell target ignition driven by Z-pinch dynamic hohlraum radiation pulse.The radiation pulse is produced with a special Z-pinch dynamic hohlraum configuration,where the hohlraum is composed of a single metal liner,a low-Z plastic foam,and a high-Z metallic foam.The implosion dynamics of a hohlraum and a multi-shell target are investigated separately by the one-dimensional code MULTI-IFE.When the peak drive current is 50 MA,simulations suggest that an x-ray pulse with nearly constant radiation temperature(-310 eV)and a duration about 9 ns can be obtained.A small multi-shell target with a radius of 1.35 mm driven by this radiation pulse is able to achieve volumetric ignition with an energy gain(G)about 6.19,where G is the ratio of the yield to the absorbed radiation.Through this research,we better understand the effects of non-uniformities and hydrodynamics instabilities in Z-pinch dynamic hohlraum.

An optimal method for the power spectrum measurement

An aliasing effect brought up by mass assignment onto Fast Fourier Transformation （FFT） grids may bias measurement of the power spectrum of large scale structures. In this paper, based on the Beylkin＇s unequally spaced FFT technique, we propose a new precise method to extract the true power spectrum of a large discrete data set. We compare the traditional mass assignment schemes with the new method using the Daub6 and the 3rd-order B-spline scaling functions. Our measurement of Poisson samples and samples of N-body simulations shows that the B-spline scaling function is an optimal choice for mass assignment in the sense that （1） it has a compact support in real space and thus yields an efficient algorithm （2） without any extra corrections. The Fourier space behavior of the 3rd-order B-spline scaling function enables it to be able to accurately recover the true power spectrum with errors less than 5% up to k 〈 kN. It is expected that such a method can be applied to higher order statistics in Fourier space and will enable us to have a precision capture of the non-Gaussian features in the large scale structure of the universe.

An effective connected dominating set based mobility management algorithm in MANETs

This paper proposes a connected dominating set (CDS) based mobility management algorithm, CMMA, to solve the problems of node entering, exiting and movement in mobile ad hoc networks (MANETs), which ensures the connectivity and efficiency of the CDS. Compared with Wu's algorithm, the proposed algorithm can make full use of present network conditions and involves fewer nodes. Also it has better performance with regard to the approximation factor, message complexity, and time complexity.

Size distribution of galaxies in SDSS DR7:weak dependence on halo environment

Using a sample of galaxies selected from the Sloan Digital Sky Survey Data Release 7(SDSS DR7) and a catalog of bulge-disk decompositions, we study how the size distribution of galaxies depends on the intrinsic properties of galaxies, such as concentration, morphology, specific star formation rate(sSFR),and bulge fraction, and on the large-scale environments in the context of central/satellite decomposition,halo environment, the cosmic web: cluster, filament, sheet and void, as well as galaxy number density. We find that there is a strong dependence of the luminosity-or mass-size relation on the galaxy concentration, morphology, s SFR and bulge fraction. Compared with late-type(spiral) galaxies, there is a clear trend of smaller sizes and steeper slope for early-type(elliptical) galaxies. Similarly, galaxies with a high bulge fraction have smaller sizes and steeper slopes than those with a low bulge fraction. Fitting formulae of the average luminosity-and mass-size relations are provided for galaxies with these different intrinsic properties. Examining galaxies in terms of their large scale environments, we find that the masssize relation has some weak dependence on the halo mass and central/satellite segregation for galaxies within mass range 9.0 ≤ log M*≤ 10.5, where satellites or galaxies in more massive halos have slightly smaller sizes than their counterparts, while the cosmic web and local number density dependence of the mass-size relation is almost negligible.

Toward accurate measurement of property-dependent galaxy clustering I.Comparison of the Vmax method and the“shuffled”method

Galaxy clustering provides insightful clues to our understanding of galaxy formation and evolution,as well as the universe.The redshift assignment for the random sample is one of the key steps to accurately measure galaxy clustering.In this paper,by virtue of the mock galaxy catalogs,we investigate the effect of two redshift assignment methods on the measurement of galaxy two-point correlation functions(hereafter 2 PCFs),the Vmax method and the"shuffled"method.We have found that the shuffled method significantly underestimates both of the projected 2 PCFs and the two-dimensional 2 PCFs in redshift space,while the Vmax method does not show any notable bias on the 2 PCFs for volume-limited samples.For fluxlimited samples,the bias produced by the Vmax method is less than half of the shuffled method on large scales.Therefore,we strongly recommend the Vmax method to assign redshifts to random samples in the future galaxy clustering analysis.

Radiation effects of electrons on multilayer FePS3studied with laser plasma accelerator

Space radiation with inherently broadband spectral flux poses a huge danger to astronauts and electronics on aircraft,but it is hard to simulate such feature with conventional radiation sources. Using a tabletop laser-plasma accelerator, we can reproduce exponential energy particle beams as similar as possible to these in space radiation. We used such an electron beam to study the electron radiation effects on the surface structure and performance of two-dimensional material(Fe PS3).Energetic electron beam led to bulk sample cleavage and damage between areas of uneven thickness. For the Fe PS3sheet sample, electron radiation transformed it from crystalline state to amorphous state, causing the sample surface to rough.The full widths at the half maximum of characteristic Raman peaks became larger, and the intensities of characteristic Raman peaks became weak or even disappeared dramatically under electron radiation. This trend became more obvious for thinner samples, and this phenomenon was attributed to the cleavage of P–P and P–S bonds, destabilizing the bipyramid structure of [P2S6]4-unit. The results are of great significance for testing the maximum allowable radiation dose for the two-dimensional material, implying that Fe PS3cannot withstand such energetic electron radiation without an essential shield.

The intrinsic SFRF and sSFRF of galaxies:comparing SDSS observation with IllustrisTNG simulation

The star formation rate function(SFRF) and specific star formation rate function(s SFRF) from observations are impacted by the Eddington bias, due to uncertainties in the estimated star formation rate(SFR). We develop a novel method to correct the Eddington bias and obtain the intrinsic SFRF and sSFRF from the Sloan Digital Sky Survey(SDSS) Data Release 7. The intrinsic SFRF is in good agreement with measurements from previous data in the literature that relied on UV SFRs but its high star-forming end is slightly lower than the corresponding IR and radio tracers. We demonstrate that the intrinsic sSFRF from SDSS has a bimodal form with one peak found at sSFR ~10-9.7 yr^-1 representing the star-forming objects while the other peak is found at sSFR ~10-12 yr^-1 representing the quenched population. Furthermore, we compare our observations with the predictions from the Illustris TNG and Illustris simulations and affirm that the "TNG" model performs much better than its predecessor. However,we show that the simulated SFRF and CSFRD of TNG simulations are highly dependent on resolution,reflecting the limitations of the model and today’s state-of-the-art simulations. We demonstrate that the bimodal, two peaked s SFRF implied by the SDSS observations does not appear in TNG regardless of the adopted box-size or resolution. This tension reflects the need for inclusion of an additional efficient quenching mechanism in the TNG model.

Optimization of the beam quality in ionization injection by a tailoring gas profile

A new scheme is proposed to improve the electron beam quality of ionization-induced injection by tailoring gas profile in laser wakefield acceleration.Two-dimensional particle-in-cell simulations show that the ionization-induced injection mainly occurs in high-density stage and automatically truncates in low-density stage due to the decrease of the wakefield potential difference.The beam loading can be compensated by the elongated beam resulting from the density transition stage.The beam quality can be improved by shorter injection distance and beam loading effect.A quasi-monoenergetic electron beam with a central energy of 258 MeV and an energy spread of 5.1%is obtained under certain laser-plasma conditions.

An empirical model to form and evolve galaxies in dark matter halos

Based on the star formation histories of galaxies in halos with different masses, we develop an empirical model to grow galaxies in dark matter halos. This model has very few ingredients, any of which can be associated with observational data and thus be efficiently assessed. By applying this model to a very high resolution cosmological N-body simulation, we predict a number of galaxy properties that are a very good match to relevant observational data. Namely, for both centrals and satellites, the galaxy stellar mass functions up to redshift z=4 and the conditional stellar mass functions in the local universe are in good agreement with observations. In addition, the two point correlation function is well predicted in the different stellar mass ranges explored by our model. Furthermore, after applying stellar population synthesis models to our stellar composition as a function of redshift, we find that the luminosity functions in the 0.1 u,0.19, 0.1r, 0.1i and 0.1z bands agree quite well with the SDSS observational results down to an absolute magnitude at about -17.0. The SDSS conditional luminosity function itself is predicted well. Finally, the cold gas is derived from the star formation rate to predict the HI gas mass within each mock galaxy. We find a remarkably good match to observed HI-to-stellar mass ratios. These features ensure that such galaxy/gas catalogs can be used to generate reliable mock redshift surveys.

The importance of Righi-Leduc heat flux to the ablative Rayleigh-Taylor instability during a laser irradiating targets

The Righi±Leduc heat flux generated by the self-generated magnetic field in the ablative Rayleigh±Taylor instability driven by a laser irradiating thin targets is studied through two-dimensional extended-magnetohydrodynamic simulations.The perturbation structure gets into a low magnetization state though the peak strength of the self-generated magnetic field could reach hundreds of teslas.The Righi±Leduc effect plays an essential impact both in the linear and nonlinear stages,and it deflects the total heat flux towards the spike base.Compared to the case without the self-generated magnetic field included,less heat flux is concentrated at the spike tip,finally mitigating the ablative stabilization and leading to an increase in the velocity of the spike tip.It is shown that the linear growth rate is increased by about 10%and the amplitude during the nonlinear stage is increased by even more than 10%due to the feedback of the magnetic field,respectively.Our results reveal the importance of Righi±Leduc heat flux to the growth of the instability and promote deep understanding of the instability evolution together with the self-generated magnetic field,especially during the acceleration stage in inertial confinement fusion.

Liquid metal enabled combinatorial heat transfer science： toward unconventional extreme cooling

As a class of newly emerging material, liquid metal exhibits many outstanding performances in a wide variety of thermal management areas, such as thermal interface material, heat spreader, convective cooling and phase change material （PCM） for thermal buffering etc. To help mold next generation unconventional cooling technologies and further advance the liquid metal cooling to an ever higher level in tackling more extreme, complex and critical thermal issues and energy utilizations, a novel conceptual scientific category was dedicated here which could be termed as combinatorial liquid metal heat transfer science. Through comprehensive interpretations on a group of representative liquid metal thermal management strategies, the most basic ways were outlined for developing liquid metal enabled combined cooling systems. The main scientific and technical features of the proposed hybrid cooling systems were illustrated. Particularly, five abstractive segments toward constructing the combinatorial liquid metal heat transfer systems were clarified. The most common methods on innovating liquid metal combined cooling systems based on this classification principle were discussed, and their potential utilization forms were proposed. For illustration purpose, several typical examples such as low melting point metal PCM combined cooling systems and liquid metal convection combined cooling systems, etc. were specifically introduced. Finally, future prospects to search for and make full use of the liquid metal combined high performance cooling system were discussed. It is expected that in practical application in the future, more unconventional combination forms on the liquid metal cooling can be obtained from the current fundamental principles.

A fuzzy formal concept analysis based approach for business component identification

Identifying business components is the basis of component-based software engineering. Many approaches, including cluster analysis and concept analysis, have been proposed to identify components from business models. These approaches classify business elements into a set of components by analyzing their properties. However, most of them do not consider the difference in their properties for the business elements, which may decrease the ac- curacy of the identification results. Fhrthermore, component identification by partitioning business elements cannot reflect which features are responsible for the generation of certain results. This paper deals with a new approach for component identification from business models using fuzzy formal concept analysis. First, the membership between business elements and their properties is quantified and transformed into a fuzzy formal context, from which the concept lattice is built using a refined incremental algorithm. Then the components are selected from the concepts according to the concept dispersion and distance. Finally, the effectiveness and efficiency are validated by applying our approach in the real-life cases and experiments.