大面积等离子体片密度分布分析

利用空心阴极放电产生了尺寸为60 cm× 60 cm× 2 cm的大面积等离子体面. 在实验室条件下对大面积等离子体片的密度分布进行了测量. 由于高压放电脉冲脉宽较短, 实验中改变了测量方法, 同时, 在中等磁场影响下, 为了得到真实的等离子体密度, 进行了必要的数值修正.在放电电流为1---6 A时, 测量了二维的电子密度分布. 另外, 测量并讨论了其他环境参数对等离子体密度的影响. 电子密度的分布情况对与微波波束切换相当重要. 由空心阴极增强型放电产生的大面积等离子体面具有反射X波段(8---12 GHz) 微波需要的足够稠密的电子密度和足够均匀的密度分布, 这是等离子体面在雷达系统中取代金属面板的有利条件.     

Modulation instability of bright photovoltaic solitons on a partially incoherent background

We present the observation of incoherent anti-dark photovoltaic solitons in LiNbO₃:Fe crystal. This new class of soliton states involves bright photovoltaic solitons on a background beam meeting ?? > 1, where ?? is the ratio of background illumination photovoltaic constant to that of soliton beam. For ?? < 1, dark photovoltaic solitons are generated. Furthermore, this novel type solitons are investigated experimentally by injecting coherent light and partially coherent background of infinite extent. In case of spatial coherence of the background lower than the threshold of incoherent modulation instability, these results indicate that bright photovoltaic solitons can propagate in a stable fashion.     

The effects of the finest grains on the mechanical behaviours of nanocrystalline materials

This article proposes a new constitutive model to account for effects of the finest grains, with sizes ranging from 2 to 4 nm, on the mechanical behaviours of nanocrystalline (NC) materials. In this model, the normal nanograins (ranging from 20 to 100 nm) were treated as though they were composed of a grain interior (GI) and a grain boundary (GB) affected zone (GBAZ). The finest grains were considered to be part of the GBAZ, denoted as super triple junctions (STJs). For the initial plastic deformation stage of the NC materials, a phenomenological constitutive equation was suggested to predict the deformation behaviours of the GBAZ. The formation of GB dislocation (GBD) pileups provides dramatic strain hardening in deformed NC materials and thereby enhances their ductility. Then, the constitutive equations to describe the plastic deformation of the GI and the GBAZ lattice region were established. In this stage, the GBAZ are already saturated with GBD pileups, and GI deformation is the dominant mechanism. Finally, the mechanical model for the NC materials with the finest grains was built using the self-consistent method, and an overall moderate “work hardening,” sustained over a long range of plastic strain, was predicted. The effects of TJs/STJs on the deformation mechanism were quantitatively analysed. The analysis demonstrated that the existence of the finest grains will simultaneously lead to good strength and good ductility.     

Interaction of aconitine with bovine serum albumin and effect of atropine sulphate and glycyrrhizic acid on the binding

The interaction of aconitine with bovine serum albumin (BSA) and effect of atropine sulphate and glycyrrhizic acid on binding constant, binding sites, and conformation were studied in an aqueous buffer solution (pH 7.40) by ultraviolet absorption and fluorescence spectroscopy. The study results show that aconitine quenched the endogenous fluorescence of BSA via a dynamic quenching procedure. Predominant intermolecular forces between aconitine and BSA were hydrophobic interactions, which stabilized the complex of aconitine–BSA. The distance between the donor and acceptor was 2.62 nm. The conformation of BSA was investigated by synchronous fluorescence techniques, indicating that the microenvironment around tryptophan (Trp) residues was changed. Furthermore, with the addition of atropine sulphate or glycyrrhizic acid, binding constant and the number of binding sites of aconitine to BSA were decreased, and the conformation had no change, which provide an important theoretical support for aconitine detoxification by atropine sulphate and glycyrrhizic acid.     

Alterable-capacity fragile watermarking scheme with restoration capability

To take invisibility and restoration quality into account, this paper proposes an alterable-capacity watermarking scheme. For each block of size 8 × 8 pixels, the alterable-length code is generated based on the roughness of it. The alterable-length watermark generated by the alterable-length code is divided into three parts and embedded in other three blocks based on the secret key. The authenticity of each block is determined by comparing the watermark reconstructed by the block content and the corresponding extracted watermark. To improve the quality of recovered images, two copies of the significant-code of each block are embedded in different blocks and the image inpainting method is adopted to recover the tampered blocks whose significant-code embedded in other blocks is destroyed. The alterable-payload watermark preserves adequate information of image blocks especially for texture images with as few bits as possible and takes into account invisibility, security and restoration quality. Experimental results demonstrate that the proposed scheme improves the quality of watermarked and reconstructed images and is resilient to the known forgery attacks.     

The pilot experimental study of 14 MeV fast neutron digital radiography

14 MeV Fast neutrons has good penetrability and the 14 MeV fast neutron radiography can meet the need of Non-Destructive Test of the structure and lacuna of heavy-massive sample, whose shell is made of heavy metal and in which there are some hydrogen materials, and the study of fast neutron digital radiography just begins in China. By the use of a D-T accelerator, a digital imaging system made up of a fast neutron scintillation screen made of ZnS(Ag) and polypropylene, lens and a scientific grade CCD, the experimental study of fast neutron radiography has been done between 4.3×10¹⁰−6.8×10¹⁰ n/s of neutron yield. Some 14 MeV fast neutron digital radiographs have been gotten. According to experimental radiographs and their data, the performance of the fast neutron scintillation screen and the basic characters of 14 MeV fast neutron radiography are analyzed, and it is helpful for the further research. Supported by the Science and Technology Fund of China Academy of Engineering Physics (Grant No. 251)     

空间斯特林制冷机应用双机备份技术研究

为了提高斯特林制冷机对于空间探测器等应用的可靠性,往往采用双机备份的结构方式,在一台制冷机出现故障后,立即切换到另一台制冷机。文中介绍了兰州物理研究所研制的一种空间斯特林制冷机双机备份应用系统,主要设计特点、试验达到的性能指标等。     

Poly[[di­aqua­barium(II)]‐μ5‐m‐phenylenedioxydiacetato]: a three‐dimensional barium(II) coordination polymer

In the title coordination polymer, [Ba(1,3‐BDOA)(H₂O)₂]_n (where 1,3‐BDOA²⁻ is the m‐phenylenedioxydiacetate dianion, C₁₀H₈O₆), each Ba^II ion is ten‐coordinated by six carboxyl O atoms and two ether O atoms from different 1,3‐BDOA²⁻ ligands, as well as by two water mol­ecules, thus defining a dodeca­hedron. The Ba^II atoms are covalently linked by 1,3‐BDOA²⁻ ligands in different crystallographic directions, giving rise to a three‐dimensional open framework. The crystal structure is further stabilized by hydrogen bonds and π–π stacking inter­actions. In previously studied polymers of this type, the 1,3‐BDOA²⁻ ligand showed multiple bridging modes with metal ions, including bi‐, tri‐, tetra‐ and hexa­dentate. The title Ba^II complex represents a novel three‐dimensional coordination polymer constructed by octa­dentate bridging 1,3‐BDOA²⁻ ligands.     

概率约束规划逼近最优解集的稳定性和最优值的连续性

在原始规划可行集上引入了正则的概念,并在此正则条件下,研究了更一般的概率约束规划问题的稳定性.在一定的条件下,得到了概率约束规划逼近最优解集的稳定性和最优值的连续性,从而对近似求解这类问题提供了某种理论依据.     

Bis{μ‐(E)‐2‐[(2‐pyridylamino)(2‐pyridylimino)methyl]benzato}bis[acetatozinc(II)] tetrahydrate

In the C₂‐symmetric dinuclear title complex, [Zn₂(C₁₈H₁₃N₄O₂)₂(C₂H₃O₂)₂]·4H₂O, each Zn^II ion is five‐coordinated in a distorted trigonal bipyramidal fashion by one carboxylate O atom from one benzoate ligand, one imine N atom and two pyridyl N atoms from a second benzoate ligand, and one O atom from an acetate anion. The two Zn atoms are bridged by the two benzoate ligands, forming a dinuclear structure with a 14‐membered macrocycle. Adjacent dinuclear units are further connected by extensive hydrogen bonds involving the solvent water molecules, giving a three‐dimensional hydrogen‐bonded framework. The framework can be regarded as an example of the four‐connected node network of the PtS topology.