A simple approach to the synthesis of silver nanowires by hydrothermal process in the presence of gemini surfactant

Silver nanowires were synthesized by the hydrothermal route in aqueous solution of gemini surfactant 1,3-bis(cetyldimethylammonium) propane dibromide (16-3-16) at a relatively low temperature. The as-prepared silver nanowires were characterized by X-ray photoelectron spectroscopy (XPS), X-ray powder diffraction (XRD), transmission electron microscope (TEM), electron diffraction (ED), and UV-vis absorption spectrum. The obtained silver nanowires are of high aspect ratios with an average diameter of approximately 30 nm and length ranging from several to tens of micrometers.     

A first-principles investigation of LiNH(2) as a hydrogen-storage material: effects of substitutions of K and Mg for Li

Li-N-H compounds hold promise as novel hydrogen-storage materials with high gravimetric hydrogen densities. Because the dehydriding reaction caused by the decomposition of LiNH(2) requires a higher temperature than desired, much effort has been devoted to the destabilization of LiNH(2) to decrease the decomposition temperature. In particular, there has been recent experimental evidence for lowering the temperature by partial substitution of Li by Mg. However, the reason is not clear. In this study, we have employed density functional theory to investigate LiNH(2) and partially Li-substituted systems aiming to understand the effects of the substitution on the destabilization of the NH(2) species. K, a more electropositive element, and Mg, a more electronegative element, have been chosen as two probes to illustrate the effects. We have focused on the investigation of effects of substitutions on the N-H bond strength that is regarded as a qualitative indicator of the decomposition temperature. We have found that in both cases the N-H bonds are weakened, in particular, the Mg substitute appears to be more effective in the destabilization of the NH(2). The relative strength of the metal-N ionic bonding has been found to be a key factor to explain the effects of the substitutes. These have been discussed in detail in terms of Wannier function analyses.     

Eu~(3+)激活MgO-Al_2O_3-SiO_2发光体的溶胶-凝胶法合成和特性研究

在实验室中,采用溶胶-凝胶法,在1000℃的温度下,合成出组成为2.692MgO-1.2Al_2O_3-4SiO_2:0.045Eu~(3+),0.009Bi~(3+)(加入Li~+作为电荷补偿剂)发光体。利用红外光谱,X射线粉末衍射、热重及差热分析研究了由凝胶至发光晶体的转变过程。采用岛津RF-540荧光分光光度计,在室温下测量了发光体的激发光谱和发光光谱。讨论了发光体的发光特性及Bi~(3+)对Eu~(3+)的敏化作用。     

在高于253 K温度下的1550 nm波长单光子探测实验

介绍了在高于253 K的温度下,实现红外单光子探测的实验.选用拉通电压较高的雪崩光电二极管（APD）,设计制作了非线性限流技术保护高温工作的APD,利用半导体热电制冷器,在256.8K的温度下,实现了1550 nm波段的单光子探测实验.单光子探测的暗记数率为3.13×10－5 ns,在220 kHz/s的单光子脉冲速率下,探测效率为2.08%.     

用多重网格技术求解平面叶栅跨音绕流

1982年以来,Ni、Davis等人发展了一种与多重网格技术相结合的时间相关有限体积积分方法,这是一个快速求定常解的显式推进方法。本文采用这种方法计算平面叶栅跨音绕流,阐明了Ni-Davis格式的基本思想和处理原则,在物面边界近似处理上本文作了适当改进,为适当选取人工粘性项提出了具体平滑公式,又根据数值试验对多重网格技术提出了改进算法。两个跨音叶栅绕流算例表明,数值结果的精度和计算效率是令人满意的,可以满足航空发动机气动设计的需要。在IBM 4341计算机上,求解一个65×17网格上的跨音流场大约需CPU时间15分钟,使用四层网格技术后可节省CPU时间50%到60%。     

超弹性矩形板单向拉伸时微孔的增长*

本文研究了含中心微孔的超弹性矩形板在单向拉伸时的有限变形和受力分析.为了考察微孔的存在对矩形板变形和应力的影响,将问题化成一个超弹性环形板的变形和受力分析,并用最小势能原理得到变分近似解.进行了数值计算,分析了微孔的增长情况.     

色散缓变光纤中皮秒孤子脉冲的压缩

本文实验研究了孤子脉冲在色散缓变光纤中传输时的动力学特性,发现孤子脉冲在色散缓变光纤中能被压缩.采用500米色散缓变光纤,成功将4.4ps的孤子脉冲压缩到830fs,脉冲压缩比为5.3.色散缓变光纤中孤子脉冲压缩的实验研究为超短光脉冲压缩提供了新的途径和方法.     

粘弹性圆薄板的动力学行为

基于线性粘弹性力学的Boltzmann叠加原理,给出粘弹性圆薄板动力学分析的初边值问题。通过一定的简化后得到描述薄板力学行为的四维非线性非自治动力系统。综合使用非线性动力学中的数值分析方法,研究了参数对粘弹性圆薄板动力学行为的影响。同时计算了吸引子的Lyapunov维、相关维和点形维。     

粘弹性柱壳的若干动力学性质

本文讨论了轴向压力和一致分布的径向压力作用下粘弹性柱壳的动力稳定性问题.利用Laplace变换,得到了常载作用下粘弹壳的稳定性条件.综合利用动力学的经典方法,得到了由粘弹性壳所定义的动力系统的各种动力学性质及各种参数对结构稳定性的影响.     

Some dynamical properties of a viscoelastic cylindrical shell

IntroductionTherearerarepapersonthedynamicPropertiesofviscoelasticshells.~ulosl']discussesthecaseofshallowsphericalshellandDrozdov[ZIgivesasufficientcondihonofstabilityfortheviscoelasticcylindershellbyusingtheLyapunovfunchonal.UsingtheLyapunovdirectmethod,Tyllkowski[']establishesasufficientconditionfortheasymptohcstabilityofviscoelasticcylindricalshell.ItisnotdifficulttofindthattheseexistingresultSmainlyconcentrateonthedynamicstabilityofviscoelasticshell.Thediscussionaboutthedynamicalsyste…