FAR3d程序对EAST上阿尔芬不稳定性识别过程中的应用

为更好理解EAST实验中的等离子体不稳定性现象,文章从实验和模拟两个角度,对EAST中高βN放电区间的阿尔芬不稳定性现象进行了分析。在实验上,本文使用高频磁探针和电子回旋辐射诊断对不稳定性的频率、位置、环向模数进行判断。在模拟上首次应用了FAR3d程序,识别了在ρ=0.45、频率为87 kHz的主导模式TAE(toroidicity-induced Alfven eigenmode),以及ρ=0.55、频率为62 kHz的次主导模式EPM(energetic particle mode),环向模数均为2,与实验中的测量结果对比在误差范围内基本一致,自洽地识别了不稳定性的类型并且得到了位置与频率信息。在此基础上,对有限拉莫轨道(finite Larmor radius, FLR)效应进行评估。模拟结果显示,在EAST高βN放电区间,FLR效应对识别低环向模数n的不稳定性模式的影响较小。在该放电的模式的识别过程中可关闭FLR以加速计算。FAR3d程序高效的计算能力和精准的模拟结果,可为后续EAST的实验提供指导。

Investigation of radial heat conduction with 1D self-consistent model in helicon plasmas

A 1D radially self-consistent model in helicon plasmas has been established to investigate the influence of radial heat conduction on plasma transport and wave propagation.Two kinds of 1D radial fluid models,with and without considering heat conduction,have been developed to couple the 1D plasma-wave interaction model,and self-consistent solutions have been obtained.It is concluded that in the low magnetic field range the radial heat conduction plays a moderate role in the transport of helicon plasmas and the importance depends on the application of the helicon source.It influences the local energy balance leading to enhancement of the electron temperature in the bulk region and a decrease in plasma density.The power deposition in the plasma is mainly balanced by collisional processes and axial diffusion,whereas it is compensated by heat conduction in the bulk region and consumed near the boundary.The role of radial heat conduction in the large magnetic field regime becomes negligible and the two fluid models show consistency.The local power balance,especially near the wall,is improved when conductive heat is taken into account.

Architectural Approaches to Network and Service Access Authentication

Authentication is the first step,of central importance, for access control and for security protection in radio access networks.A general model for authentication was adopted from fixed networks and applied to the wireless world.However,the differences in the operational environment between the fixed and the wireless world,heterogeneity of the radio communications systems,new trends in service provisioning, emerging business models and performance requirements raise the need to revisit the original requirements for authentication systems and to come up with schemes that better suit current needs.In this review paper we discuss authentication in singlehop radio access networks by characterizing the current as well as the emerging authentication schemes.

RELATIVE ASYMPTOTICS FOR ORTHOGONAL MATRIX POLYNOMIALS WITH RESPECT TO A PERTURBED MATRIX MEASURE ON THE UNIT CIRCLE

Given a positive definite matrix measure Ω supported on the unit circle T, then main purpose of this paper is to study the asymptotic behavior of L n()L n(Ω) -1 and Φ n(z;)Φ n(z;Ω) -1 where(z)=Ω(z)+Mδ(z-w); |w|>1,M is a positive definite matrix and δ is the Dirac matrix measure. Here, L n(·) means the leading coefficient of the orthonormal matrix polynomials Φ n(z;·). Finally, we deduce the asymptotic behavior of Φ n(w;)Φ n(w;Ω)* in the case when M=I.

Zeolitic imidazolate framework-67 derived Al-Co-S hierarchical sheets bridged by nitrogen-doped graphene:Incorporation of PANI derived carbon nanorods for solid-state asymmetric supercapacitors

Metal sulfides have been widely enticed as battery-type electrodes in supercapacitor devices because of their maximal theoretical capacitance.Nevertheless,their lower conductivity and ion transport kinetics can largely restrict their rate performance,hence the practical usage in fields of demanding high power devices.Therefore,the design of new electrodes with higher energy and power densities remains a highly challenging task.To the best of our knowledge,a novel hierarchical composite of Al-CoS_(2) on nitrogendoped graphene(NG)is prepared based on a zeolite imidazole framework using a simple and scalable hydrothermal process.In this hybrid,ultrathin Al-CoS_(2) nanosheet arrays are vertically orientated on the NG framework to limit self-aggregation,hence increasing the electrical property and cycle stability of composite.It is investigated that the Al/Co feeding ratio plays a crucial role in controlling the obtained hierarchical structure of Al-Co-S sheets and their electrode performance.Also,Al^(3+) can influence remarkably the morphology and electrochemical property of the resultant graphene composite.An effective synergism is noticed between the redox Al-CoS_(2) and NG resulting in fast electron transfer and chargingdischarging processes.Surprisingly,when the as-developed composite is utilized as a positive electrode at an applied current density of 1 A/g,a specific capacitance of 1915.8 F/g is attained with ultra-long cycle stability(96%,10,000 cycles)and an excellent retention rate(~89%).As a consequence,when a solid-state asymmetric supercapacitor(ASC)device is made by combining an Al-CoS_(2) @NG hybrid with a negative electrode made of polyaniline(PANI)derived carbon nanorods(PCNRs),it demonstrates remarkable specific capacitance(188 F/g),energy density(66.9 Wh/kg),and cyclic stability of 92%after 10,000 cycles.This may open the pathway for the application of the next-generation supercapacitors in the future.

ON THE MODIFICATIONS OF CLASSICAL ORTHOGONAL POLYNOMIALS: THE SYMMETRIC CASE

We consider the modifications of the monic Hermite and Gegenbauer polynomials via the addition of one point mass at the origin. Some properties of the resulting polynomials are studied ; three-term recurrence relation, differential equation, ratio asymptotics, hypergeometric representation as well as, for large n, the behaviour of their zeros.

Microstructural Development and Mechanical Properties of PM Ti-45Al-2Nb-2Mn-0.8 vol.%TiB_2 Processed by Field Assisted Hot Pressing

A g-Ti Al intermetallic alloy, Ti e45 Al e2Nb e2Mn(at.%)e0.8 vol.%Ti B2, has been processed from gas atomized prealloyed powder by field assisted hot pressing(FAHP). An initial analysis of the prealloyed powder helped on the understanding of the intermetallic sintering behavior. Atomized powder consisted of a metastable phase that transformed into a2 t g equilibrium phases by thermal treating. Different powder particle microstructures were found, which influence the microstructure development of the FAHP g-Ti Al material depending on the sintering temperature. Duplex, nearly lamellar and fully lamellar microstructures were obtained at the sintering temperatures above 1000 C. Lower consolidation temperatures, below 1000 C, led to the formation of an Al rich phase at powder particle boundaries, which is deleterious to the mechanical properties. High compressive yield strength of 1050 MPa was observed in samples with FAHP duplex microstructures at room temperature.Whereas nearly lamellar and fully lamellar microstructures showed yield strength values of 655 and 626 MPa at room temperature and 440 and 425 MPa at 750 C, respectively, which are superior in comparison to similar alloys processed by other techniques. These excellent properties can be explained due to the different volume fractions of the a2 and g phases and the refinement of the PM microstructures.

On-chip mode-locked laser diode structure using multimode interference reflectors

We report, for the first time to our knowledge, an on-chip mode-locked laser diode(OCMLLD) that employs multimode interference reflectors to eliminate the need of facet mirrors to form the cavity. The result is an OCMLLD that does not require cleaved facets to operate, enabling us to locate this OCMLLD at any location within the photonic chip. This OCMLLD provides a simple source of optical pulses that can be inserted within a photonic integrated circuit chip for subsequent photonic signal processing operations within the chip(modulation, optical filtering, pulse rate multiplication, and so on). The device was designed using standardized building blocks of a generic active/passive In P technology platform, fabricated in a multi-project wafer run, and achieved mode-locking operation at its fundamental frequency, given the uncertainty at the design step of the optical length of these mirrors, critical to achieve colliding pulse mode-locked operation.

On a Classical Theorem on the Diameter and Minimum Degree of a Graph

In this work, we obtain good upper bounds for the diameter of any graph in terms of its minimum degree and its order, improving a classical theorem due to Erd¨os, Pach, Pollack and Tuza.We use these bounds in order to study hyperbolic graphs(in the Gromov sense). To compute the hyperbolicity constant is an almost intractable problem, thus it is natural to try to bound it in terms of some parameters of the graph. Let H(n, δ_0) be the set of graphs G with n vertices and minimum degree δ_0, and J(n, Δ) be the set of graphs G with n vertices and maximum degree Δ. We study the four following extremal problems on graphs: a(n, δ_0) = min{δ(G) | G ∈ H(n, δ_0)}, b(n, δ_0) = max{δ(G) |G ∈ H(n, δ_0)}, α(n, Δ) = min{δ(G) | G ∈ J(n, Δ)} and β(n, Δ) = max{δ(G) | G ∈ J(n, Δ)}. In particular, we obtain bounds for b(n, δ_0) and we compute the precise value of a(n, δ_0), α(n, Δ) andβ(n, Δ) for all values of n, δ_0 and Δ, respectively.

Gromov Hyperbolicity of Riemann Surfaces

我们在 Riemann 表面的 Gromov 意义学习 hyperbolicity。我们从“它的积木部件”的 hyperbolicity 的表面的 deducethe hyperbolicity。我们在 Riemann 表面的 hyperbolicity 和 somegraph 的 hyperbolicity 之间的等价与它联系了的 alsoprove。这些结果澄清 Riemann 表面 intoY 片和漏斗的分解怎么影响表面的 hyperbolicity。结果简化拓扑学 ofthe 表面并且允许我们从本地信息获得全球结果。

In the shadow of the laser phantom needle cross:dynamic air-plasma aperture sheds light on terahertz microscopy

Two plasma filaments crossing above the target create a subwavelength window for terahertz microscopy that excludes any subwavelength probe in vicinity.