有旋流动的赝势函数及其对超跨声速流动的应用

本文应用缩项法对叶轮机S_1与S_2流面上熵及转焓都不均匀的有旋流动引入一新通用函数——赝势函数,它保持了势函数的优点,但却完全解除了均熵无旋的限制。特别是对于含激波的超、跨声速流动的求解,赝势函数提供了一种新的物理上完全相容、数值解简便的有力工具。     

叶轮机叶片气动优化理论的进展

—、引言叶片气动问题(一般讲,任何工程问题)可分为下列四大类:正命题,反命题,杂交型命题和优化命题。与叶栅优化命题直接相关的是叶栅反命题,但由于如何给定叶面流速,即最优流速分布问题没有解决,由于按给定叶面流速分布求出的叶型往往不能满足气动以及其他方面(强度、振动、冷却、工艺等)的要求,从而无实用价值,所以,反命题解法虽然早在40年代就已出现,但至今极少被采用。至于最优流速分布问题迟迟未能解决的原因,又是由于叶型形状同叶面流速分布之间的关系太复杂,以致极难建立变分问题的数学表      

Crystal structures and electronic properties of solid fluorine under high pressure

As the previously proposed structures of C2/m and C2/c possess similar enthalpies and x-ray diffraction patterns, the space group of fluorine at ambient pressure is in controversy. We successfully obtain its thermodynamically stable lowpressure phase, which shares the same structure as the earlier known C2/c. Further investigations on phonon spectra reveal the instability of the C2/m structure with imaginary frequency in the Brillouin zone and confirm the dynamically stable property of the C2/c structure at the same time. Compressing fluorine up to 8 GPa, the C2/c phase is found to undergo a phase transition to a new structure with a space group of Cmca. Electronic energy band structures indicate the insulating feature of C2/c and Cmca with no bands across the Fermi level. The infrared(IR) and Raman spectra of C2/c and Cmca at selected pressures are calculated to provide useful information to future experiments.     

182Os 核yrast带相继SU(3)–U(5)–SU(3)结构相变势能曲面的一种可能理解

基于联合实施微观相互作用玻色子模型的最大F旋方案 (sdIBM-F_max)与γ射线能量-自旋曲线 (γ-ray energy over spin curves, E-GOS)方案, 成功描述了¹⁸²Os核yrast带相继的SU(3)–U(5)–SU(3)结构相变, 由于缺少直观解释而显得抽象. 本文借助微观sdIBM-F_max的微观参数与Bohr哈密顿量的势能曲面方程之间存在的泛函关系, 几何地给出了对这种相继相变途径的另外一种可能理解; 并阐述了在完全变形核的高角动量态中, 由于量子效应在高激发态与低激发态之间生成高简并的临界区, 提供了γ振动能量会变得低于转动能量的一个可能途径, 从而实现了SU(3)–U(5)的相变. 关键词： yrast带结构演化 势能曲面 相变临界区 182Os核')" href="#">¹⁸²Os核     

A design of novel type superconducting magnet for super—high field functional magnetic resonance imaging by using the harmonic analysis method of magnetic vector potentials

The approach of expanding the magnetic scalar potential in a series of Legendre polynomials is suitable for designing a conventional superconducting magnetic resonance imaging magnet of distributed solenoidal configuration. Whereas the approach of expanding the magnetic vector potential in associated Legendre harmonics is suitable for designing a single-solenoid magnet that has multiple tiers, in which each tier may have multiple layers with different winding lengths. A set of three equations to suppress some of the lowest higher-order harmonics is found. As an example, a 4T single-solenoid magnetic resonance imaging magnet with 4×6 layers of superconducting wires is designed. The degree of homogeneity in the 0.5m diameter sphere volume is better than 5.8 ppm. The same degree of homogeneity is retained after optimal integralization of turns in each correction layer. The ratio B_m/B₀ in the single-solenoid magnet is 30% lower than that in the conventional six-solenoid magnet. This tolerates higher rated superconducting current in the coil. The Lorentz force of the coil in the single-solenoid system is also much lower than in the six-solenoid system. This novel type of magnet possesses significant advantage over conventional magnets, especially when used as a super-high field functional magnetic resonance imaging magnet.     

中子诱发233,235,238U裂变机制的多通道理论研究

用改进的多通道和无规颈断裂模型,计算了能量E_n=0—6MeV的中子诱发²³³U、²³⁵U裂变和E_n=1.3—5.3MeV中子诱发²³⁸U裂变的碎片的质量分布、动能分布和瞬发中子数分布,理论计算在定量上与实验符合较好.     

200GeV/u的~(238)U+~(238)U核碰撞产生的双轻子谱(M≤4GeV/c~2)的计算

在夸克味动力学的计算中,除包含ｕ、ｄ、ｓ夸克及其反夸克外,还涉及粲夸克及其反夸克（ｃｃ）,采用包含夸克味动力学效应的相对论性流体力学模型,计算了碰撞能量为２００ＧｅＶ／ｕ的２３８Ｕ＋２３８Ｕ核碰撞时形成的膨胀ＱＧＰ及其在相变过程中发射的双轻子谱,轻子对的质量范围Ｍ≤４ＧｅＶ／ｃ２．计算结果与ＣＥＲＮＳＰＳ的实验测量数据进行了定性的比较和分析,得到初步的结论：由于夸克碎块和味动力学效应,Ｊ／ψ→μ＋＋μ－峰值被降低,导致低质量区（阈至１．３５ＧｅＶ／ｃ２）谱的提高．     

一种基于移相误差估计的5步移相算法

移相误差是用移相法进行相位测量的主要误差。本文提出一种 5步移相算法 ,分两步进行相位计算 ,首先估计实际步进移相的线性移相误差 ,然后再利用此移相误差估计值计算相位分布。移相误差估计公式和相位计算公式简洁 ,算法简单易行 ,对线性移相误差和二次谐波的敏感度低 ,可基本消除线性移相误差对解调相位的影响。对本文提出的算法进行了仿真研究 ,同时给出了 Hariharan 5步算法、Surrel 6步最小算法的仿真结果。结果表明 :本算法明显优于以上两种算法 ,可基本消除线性移相误差引起的相位偏移。本算法适用于作等步移相的相位测量或移相的标定。     

用显微镜观察气体中的布朗运动

如图１所示,用一台８Ｘ物镜,１５Ｘ目镜的显微镜,自制气体布朗运动观察器一台进行观察．观察器由贮烟室和光源组成,贮烟室与橡皮球相通,贮烟室上面是透光玻璃片,光源由小电珠、透镜组成,透镜由圆柱形充水玻璃管（可用试管）代替． 实验时,用橡皮球吸入一点蚊香烟尘．把显微镜的物镜对着烟室上面透明玻璃片,点亮光源,微调升镜筒旋钮,很快看到烟尘颗粒的布朗运动现象．漂浮颗粒对光的散射,犹如夜空中游动的繁星,十分生动壮观有趣．用显微镜观察气体中的布朗运动@梁超联$广西桂林市荔浦师范学校!546600