Nuclear reactions of C on a liquid hydrogen target measured with the superconducting TOF spectrometer

Reaction cross sections with various kinds of breakup channels for neutron-rich carbon isotopes ^18-20C and for ⁹Be impinging on a liquid hydrogen target were investigated at 40 MeV/nucleon. The nuclides of interest were produced via projectile fragmentation from a 63 MeV/nucleon ⁴⁰Ar beam and were separated in flight at the RIKEN projectile fragment separator (RIPS). The combination of the large-acceptance superconducting TOF spectrometer, TOMBEE (TOF Mass analyzer for exotic BEam Experiment), with a liquid hydrogen target, CRYPTA (CRYogenic ProTon and Alpha target system), enables simultaneous measurements of several reaction channels: the reaction cross sections (σR), individual elemental fragmentation cross sections (σΔZ), charge-changing cross sections (σcc), neutron-removal cross sections (σ−xn), and charge-pickup cross sections (σΔZ+1) for ^19,20C; σΔZ, σ−xn, and σΔZ+1 for ¹⁸C; and σR for ⁹Be. The present σR of ⁹Be on proton, σR=397±23 mb, measured in the inverse kinematics, was consistent with the previous measurements using proton beams at different laboratories. The σR of ¹⁹C and ²⁰C on proton were determined to be σR=754±22 mb and σR=791±34 mb, respectively. Taking into account the beam energy and target dependence of σR, the present σR are found to be considerably enhanced compared with those measured at around 1 GeV/nucleon. The σΔZ+1 appears to increase with the mass number of the projectiles, and it significantly contributes to σR in the present energy range. The finite-range optical-limit and few-body Glauber model analyses were performed for σR to study the nuclear matter density distributions and to derive the relative strength of the s-wave components of the valence neutrons in ¹⁹C and ²⁰C. A neutron halo structure of ¹⁹C is confirmed with an s-wave dominance of the valence neutron when the effect of the charge-pickup reaction is taken into account. The large σ−n of ¹⁹C and σ−2n of ²⁰C also support the decoupled structures of ¹⁸C +n and ¹⁸C+2n, respectively. The σcc of ¹⁹C and ²⁰C agree with each other within their experimental uncertainties, which might indicate a similar proton density distribution in ¹⁹C and ²⁰C. The σΔZ decreases monotonically without the even-odd effect as the number of removed protons increases.     

The active role played by nonmagnetic Sr in magnetostructural coupling in SrTcO3 from first principles

The total energies and structural parameters of SrTcO₃ are calculated by means of the generalized gradient approximation (GGA) plus on-site Coulomb interaction corrections (GGA+U) method. G-type antiferromagnetic (G-AFM) is found to be ground state, in consistence with the previous experimental result. The distortions around Sr and Tc upon magnetic transition are compared and the change of distortion for SrO bond upon magnetic transition is found to be 25.83 times of the change for TcO bond. Our results point to an active role played by Sr in magnetostructural coupling in SrTcO₃.     

基于微透镜阵列的积分视场成像光谱仪前置成像系统分析与设计

作为对天文光谱进行观测的仪器,成像光谱仪有着十分重要的作用。由于传统的狭缝型成像光谱仪的狭缝限制,对面源天体的观测需多次扫面,才能获得完整的面源三维数据立方体(x, y; λ),这样将会浪费大量的观测时间。为了实现目标物体三维数据立方体的快速扫描,提出了一种基于微透镜阵列的无狭缝、静态化、快速高效的可见光到近红外波段积分视场成像光谱仪结构,并对其基本工作原理进行分析。为了扩展微透镜阵列积分视场成像光谱仪在医学、农业、物探等其他领域的应用潜能,该研究的光谱波段选择可见光到近红外波段。根据视场积分的工作原理,分析和设计了像方远心结构的离轴三反前置成像系统。系统采用视场离轴方式,波段范围400～900 nm,相对口径F/5,主镜、次镜和三镜皆为二次非球面,二次非球面系数分别为：-7.05,-0.92和-1.61。为减小系统体积,在离轴三反系统的焦平面附近放置反射镜。系统在奈奎斯特空间频率60 lp·mm-1处,调制传递函数大于0.75,成像质量接近衍射极限,满足系统要求。     

长焦距、大视场空间观测相机光学系统设计

为了解决空间相机高分辨率与大视场的难题,在共轴三反的基础上,通过对以往离轴三反系统改进设计,提出了一种长焦距、大视场、大相对孔径无中心遮拦的离轴三反系统设计方法,并利用ZEMAX软件设计了一种焦距为1200mm,视场角11°×3°,相对孔径F／4,工作谱段在0．4～2．5μm的光学系统,该系统在全视场空间频率50lp／mm处,MTF均值大于0．42,接近衍射极限,弥散斑直径RMS值小于10μm,表明其具有良好的成像质量。     

Terahertz spectroscopy of oxygen, O2, in its Σg and Δ electronic states : THz Spectroscopy of O2

High precision rotational spectra of isotopic oxygen O₂ (with or ) in its electronic ground state have been measured in selected frequency regions between 0.4 and 2.0 THz. The main isotopic species, , was also investigated in its first excited electronic state . The new data, analyzed together with previous measurements, yielded improved spectroscopic parameters.     

Integrable structure of melting crystal model with two -parameters

This paper explores integrable structures of a generalized melting crystal model that has two q-parameters q₁,q₂. This model, like the ordinary one with a single q-parameter, is formulated as a model of random plane partitions (or, equivalently, random 3D Young diagrams). The Boltzmann weight contains an infinite number of external potentials that depend on the shape of the diagonal slice of plane partitions. The partition function is thereby a function of an infinite number of coupling constants t₁,t₂,… and an extra one Q. There is a compact expression of this partition function in the language of a 2D complex free fermion system, from which one can see the presence of a quantum torus algebra behind this model. The partition function turns out to be a tau function (times a simple factor) of two integrable structures simultaneously. The first integrable structure is the bigraded Toda hierarchy, which determines the dependence on t₁,t₂,…. This integrable structure emerges when the q-parameters q₁,q₂ take special values. The second integrable structure is a q-difference analogue of the 1D Toda equation. The partition function satisfies thisq-difference equation with respect to Q. Unlike the bigraded Toda hierarchy, this integrable structure exists for any values of q₁,q₂.     

Variational treatment of Faraday waves in inhomogeneous Bose-Einstein condensates

Motivated by the recent experimental progress on the collective modes of a Bose-Einstein condensate whose atomic scattering length is tuned via Feshbach resonances, we analyze by variational means the dynamics of Faraday waves in trapped Bose-Einstein condensates. These waves can be excited by modulating periodically either the strength of the magnetic trap or the atomic scattering length. To study their dynamics, we develop a variational model that describes consistently both the bulk part of an inhomogeneous, low-density, cigar-shaped condensate and small-amplitude, small-wavelength Faraday waves. The main ansatz used in the variational treatment is tailored around a set of Gaussian envelopes and we show extensions for the high-density regime using a q-Gaussian function. Finally, we show explicitly that for drives of small amplitude, the two methods of obtaining Faraday waves are equivalent, and we discuss the existing experimental results.     

基于数据驱动的弹射救生可视化软件开发

以第三代弹射救生系统为基本仿真对象,根据实际座椅系统的工作过程,基于Unity3D游戏引擎,数据驱动3DsMax建模软件建立的三维仿真实体模型,结合基于C#编程开发语言的Visual Studio 2010开发平台,利用计算机图形图像生成技术,将弹射救生过程中的相关信息以三维图像直观地显示出来,表现人椅系统出舱过程、离机过程和人伞系统工作过程在真实的实验数据驱动下弹射救生全过程。通过开发弹射救生可视化软件系统,把弹射救生这一复杂过程直观形象地展现出来,为研究防护救生技术提供一条行之有效的手段。     

Coupling effect of surface plasmon polaritons in single-negative lamellar heterostructure

Propagation characteristics of surface plasmon polaritons (SPPs) in the lamellar heterostructure, which is actually a SPP waveguide array, constructed by two kinds of single negative (SNG) material layers stacked alternatively are investigated. Based on the finite element method (FEM), the negative-refraction (NR) property is demonstrated when the electromagnetic wave penetrates through free space into such SNG lamellar structure. A clear view of the underlying physics of NR is presented qualitatively that is mainly related to the coupled SPPs. The strong coupling effect leads to the novel SPP dispersion curves and then the anomalous propagation characteristics.