Characteristic Sizes for Exhaustion-Hardening Mechanism of Compressed Cu Single-Crystal Micropillars

The stress-strain response of Cu single-crystal compression micropillar containing initial dislocation network is investigated by three-dimensional discrete dislocation dynamics simulations. The results demonstrate that the stress-strain curves can be divided into three distinct types with increasing the sizes of micropillars： the three- stage exhaustion hardening, the multi-stage mixed hardening and the two-stage conventioned forest hardening. The characteristic sizes of the micropillars is determined for the second type of the curves to be 500-700 nm.     

电谐振器和磁谐振器构成的左手材料的实验验证

加工、制作和测试了由电谐振器和磁谐振器构成的左手材料.首先分别测试了电谐振器、磁谐振器各自的传输频谱,得到各自的负参数区域,然后测试了由电谐振器和磁谐振器构成的左手材料的传输频谱,并提取了其等效介电常数和磁导率.实验结果表明,在电谐振器和磁谐振器各自传输禁带的重合区域,出现了一个通带,在该通带内,等效介电常数和磁导率同时为负,验证了材料的左手特性.     

完全匹配层吸收边界在2D3V等离子体粒子模拟中的实现

基于Berenger完全匹配层的基本思想,导出了高斯单位制下2维完全匹配层吸收介质的控制方程及参数设置方法,并进行了数值验证和参数优化。依据所得结论编制了相应的吸收边界模块加入到2D3V等离子体粒子模拟程序PLASIM中,取得了良好的吸收效果。基于完全匹配层吸收边界的实现,在小窗口内对超强激光预脉冲与低密度等离子体的长时间相互作用过程进行了模拟研究,结果表明:激光强度和作用时间是影响等离子体密度改变的重要因素,超强激光其长时间的预脉冲可以通过有质动力的累积效应在低密度等离子体中引起较大的密度变化。     

质子束在等离子体中传输的粒子模拟

用粒子模拟程序研究了长脉冲质子束在等离子体中的传输特性,模拟结果表明,等离子体可以明显改善质子束的空间传输特性,大尺度的等离子体相对于等离子体层可以实现较长距离的稳定传输。研究发现,在实现长距离传输时,等离子体波会对质子束密度有较大的调制作用,严重影响质子束的传输性质,同时通过优化束密度分布可以有效减弱等离子体波的激发,实现束较稳定的传输。     

Amphiphilic Block‐Graft Copolymers with a Degradable Backbone and Polyethylene Glycol Pendant Chains Prepared via Ring‐Opening Polymerization of a Macromonomer

Well‐defined amphiphilic block‐graft copolymers PCL‐b‐[DTC‐co‐(MTC‐mPEG)] with polyethylene glycol methyl ether pendant chains were designed and synthesized. First, monohydroxyl‐terminated macroinitiators PCL‐OH were prepared. Then, ring‐opening copolymerization of 2,2‐dimethyltrimethylene carbonate (DTC) and cyclic carbonate‐terminated PEG (MTC‐mPEG) macromonomer was carried out in the presence of the macroinitiator in bulk to give the target copolymers. All the polymers were characterized by ¹H NMR and gel permeation chromatography (GPC). The polymers have unimodal molecular weight distributions and moderate polydispersity indexes. The amphiphilic block‐graft copolymers self‐assemble in water forming stable micelle solutions with a narrow size distribution.

     

Phase-Type分布的一个新稠密子集及其性质

针对目前常用的Phase-Type分布稠密子集存在的问题,对Hyper-Erlang分布进行扩展,给出了Phase-Type分布一个新的稠密子集E-HErD,证明了该新稠密子集的稠密性,并给出了其若干相关性质.     

Synthesis of Novel Monophosphoramidite Ligands Derived from L-Proline for Rh-catalyzed Asymmetric Hydrogenation of α-Dehydroamino Acid Esters

Two novel monophosphoramidites were synthesized through a five-step transformation from commercially available L-proline. In the Rh-catalyzed asymmetric hydrogenation of α-dehydroamino acid derivatives, ligand （Sc,Rα）-1b showed good enantioselectivity and up to 91% e.e. was obtained.     

Three-dimensional invisible cloaks with arbitrary shapes based on partial differential equation

The method of designing electromagnetic invisible cloak is usually based on the form-invariance of Maxwell’s equations in coordinate transformation. By solving the partial differential equations (PDEs) that describe how the coordinates transform, three-dimensional (3-D) electromagnetic and acoustic invisible cloaks with arbitrary shapes can be designed provided the boundary conditions of the cloaks can be determined by the corresponding transformation. Full wave simulations based on finite element method verify the designed cloaks. The proposed method can be easily used in designing other transformation media such as matter-wave cloaks.     

Preparation and characterization of Li4/3Ti5/3O4/Ag composite prepared by sol-gel technique

The powders of Li_4/3Ti_5/3O₄/Ag composite were prepared by sol-gel technique. Structural identification, surface morphology and electrochemical properties of the powders were studied by X-ray diffraction, scanning electron microscopy and galvanostatic charge-discharge experiments. The results show that Li_4/3Ti_5/3O₄/Ag composite derived from sol-gel is a composite of Li_4/3Ti_5/3O₄ and silver. Li_4/3Ti_5/3O₄/Ag composite shows higher specific capacity, higher columbic efficiency and lower polarization than Li_4/3Ti_5/3O₄. The addition of silver greatly improves the cycleability of Li_4/3Ti_5/3O₄, especially at higher charge-discharge rate.     

金矿含氰废水在土壤中的残留试验

通过对桐柏金矿矿区粘土和南阳一带砂土进行不同浓度下氰化物淋溶试验，并对不同土层风干后氰化物的残留量进行了研究。与原土层土壤本底值氰化物含量进行对比，发现二者并无显著差异。同种土壤经不同浓度的氰化物淋溶后，氰化物残留量也无显著差异。为指导污灌及植物栽培提供了科学依据