宇宙中的暗物质及大尺度结构的形成——暗物质成分及成团图景

宇宙间的物质绝大部分是不可视的。这些暗物质成分不是单一的,对大尺度结构的形成起着关键的作用。在含有多种成分的宇宙中,一种重要的成团特性是:若成分1和2的密度和Jeans长度满足ρ₁《ρ₂,λ_1J《λ_2J,则非主导成分1中尺度小于λ_2J的非均匀性,无论初始如何,最终总是强于主导成分中的相应非均匀性。利用这一机制可以推断,暗物质至少含有两种成分,一是静质量较小的弱粒子,构成主导成分,一是质量较大的超弱粒子,构成非主导成分。含有两种暗物质的宇宙,可以统一地解释大尺度结构的主要特征:1.超星系团和巨洞构成的100Mpc非均匀性;2.存在红移z>2的可视天体;3.在小于超星系团尺度上,暗物质分布较可视天体均匀;4.由矮球星系数据所推知的可能存在两种质量不同的微子。     

黑洞吸积盘中的迅速冷却区及受激复合发射

本文提出了在黑洞吸积盘中有可能存在受激复合发射机制,这种机制将出现于具有迅速冷却区的吸积盘中.这种盘将有相干的H及HeI的线发射.这一模型可以用来自恰地解释所有迄今得到的关于SS433的观测事实.     

Stability Analysis of Gradient-Based Neural Networks for Optimization Problems

The paper introduces a new approach to analyze the stability of neural network models without using any Lyapunov function. With the new approach, we investigate the stability properties of the general gradient-based neural network model for optimization problems. Our discussion includes both isolated equilibrium points and connected equilibrium sets which could be unbounded. For a general optimization problem, if the objective function is bounded below and its gradient is Lipschitz continuous, we prove that (a) any trajectory of the gradient-based neural network converges to an equilibrium point, and (b) the Lyapunov stability is equivalent to the asymptotical stability in the gradient-based neural networks. For a convex optimization problem, under the same assumptions, we show that any trajectory of gradient-based neural networks will converge to an asymptotically stable equilibrium point of the neural networks. For a general nonlinear objective function, we propose a refined gradient-based neural network, whose trajectory with any arbitrary initial point will converge to an equilibrium point, which satisfies the second order necessary optimality conditions for optimization problems. Promising simulation results of a refined gradient-based neural network on some problems are also reported.     

双二茂铁甲氨基醇的合成及其硅烷基化

;双二茂铁甲醇;硅基化;双二茂铁甲氨基醇的合成及其硅烷基化     

The effect of Nb addition on the thermal stability and magnetic properties of Fe-based amorphous alloys with a wide supercooled liquid region

We have examined the effect of Nb addition on the thermal stability of the supercooled liquid before crystallization, the glass-forming ability and magnetic properties for the amorphous alloy series Fe₇₃Nb_xAl_5-xGe₂P₁₀C₆B₄ and Fe₆₃Co₇Nb_xZr_10-xB₂₀. The supercooled liquid regions (ΔT_x=T_x-T_g) have maximum values of 66 and 79K, respectively, for Fe₇₃Nb₁Al₄Ge₂P₁₀C₆B₄ and Fe₆₃Co₇Nb₄Zr₆B₂₀ alloys. The saturation magnetization σ_s of the Fe₇₃Nb_xAl_5-xGe₂P₁₀C₆B₄ alloy system is much higher than that of the Fe₆₃Co₇Nb_xZr_10-xB₂₀ alloy system, and is almost unchanged with an increasing Nb content from 0 to 3 at%. But the σ_s of the Fe₆₃Co₇Nb_xZr_10-xB₂₀ alloys decreases linearly with increasing Nb content. The coercive force H_c of the two alloy series can have a minimum value of 31A/m for Fe₇₃Nb₁Al₄Ge₂P₁₀C₆B₄ and 37A/m for Fe₆₃Co₇Nb₄Zr₆B₂₀. All these values are for the ribbons annealed at 773 and 873K for 15min in vacuum.     

Preparation of Gd-Ni Film Alloy in Urea-NaBr Melt

Gd in 4f lanthanon has ferromagnetic-paramagnetism transform temperature (Curie point) and the highest magnetic thermal entropy change at room temperature. So far, it is still the best magnetic refrigeration working substance material. The systems of urea with some alkali metal salts have lower melting point (301~389 K)^[1], greater solubility of metal chloride and higher conductivity^[2]. In this paper, the electrode processes of Ni (Ⅱ) reduced in urea-NaBr melt, electrodeposition of nickel with gadolinium, and the surface morphology and the structural states of electrodeposited films and films after heat treatment have been investigated.     

A Study of the Dual Affine Scaling Continuous Trajectories for Linear Programming

In this paper, a continuous method approach is adopted to study both the entire process and the limiting behaviors of the dual affine scaling continuous trajectories for linear programming. Our approach is different from the method presented by Adler and Monteiro (Adler and Monteiro, Math. Program. 50:29–51, 1991). Many new theoretical results on the trajectories resulting from the dual affine scaling continuous method model for linear programming are obtained.     

1,10-邻菲啰啉-5,6-二酮修饰碳糊电极测定水中镉

以1,10-邻菲啰啉-5,6-二酮(phendio)修饰碳糊电极为工作电极,在0.05mol/L HAc-NaAc(pH4.74)电解液中,于-1.30V(vs.SCE)处Cd2 以Cd-1,10-邻菲啰啉-5,6-二酮络合物的形式吸附到电极上,再经过阳极溶出,从而建立了一种测定水样中痕量镉的新方法。本法于-0.69V处产生一个灵敏的溶出峰,其二阶导数峰电流与Cd2 的浓度在2.4×10-7~6.0×10-9mol/L范围内呈良好的线性关系;检出限为3.0×10-10mol/L(S/N=3)。应用本方法测定水样中的Cd2 ,结果令人满意。     

新型锂离子电池正极材料LiVOPO4的制备与表征

Novel lithium-ion battery cathode material LiVOPO₄ was synthesized by sol-gel method using lithium hydroxide, ammonium metavanadate, phosphoric acid and citric acid as raw materials. The microstructure, surface morphology and electrochemical properties were characterized by various electrochemical methods in combination with thermogravimertric (TG) analysis and differential thermal analysis (DTA), X-ray diffraction (XRD), infrared (IR) spectroscopy, scanning electron microscope (SEM). Results show that the sample obtained by calcinating at 650 ℃ for 6 h is made up of uniform particles with size of 2～3 μm. The first discharge, charge capacity and columbic efficiency of LiVOPO₄ is 137.1 mAh·g^-1, 146.1 mAh·g^-1 and 93.8%, respectively. After 80 cycles the discharge capacity is kept at 130.4 mAh·g^-1, which is 95.1% of the first discharge capacity, and the capacity loss per cycle was only 0.061%, suggesting the LiVOPO₄ derived by this method is a promising cathode material for lithium ion batteries.     

{[Nd4(ox)4(NO3)2(OH)2(H2O)2].5H2O}n: a porous 3D lanthanide-based coordination polymer with a special luminescent property

Unique bridging modes of oxalates and nitrates have unexpectedly caused a porous 3D lanthanide-based coordination polymer, which has 1D channels and displays a special luminescent property.