Focusing properties of the double-vortex beams through a high numerical-aperture objective

We study the focusing properties of the double-vortex beams through a high numerical-aperture objective based on the vectorial Debye theory. We investigate the double-vortex beams composing of two rings, and each ring carries different orbital angular momentum (OAM). It is shown that the total intensity distributions in the focal region are of double-ring structure, and by adjusting certain parameters, the shape of double-ring can be changed. The tight focusing of the double-vortex beams may find applications in micro-particle trapping, manipulation, material processing, etc.     

Radiography of a K_α X-ray source generated through ultrahigh picosecond laser–nanostructure target interaction

Laser-driven ultrafast X-ray sources are widely used for diagnostic radiography. However, there is a large divergence of fast electrons when they are generated by an intense short-pulse laser interacting with a foil target.We design a nanowire array target to achieve a more compact point X-ray source. Fast electrons are confined and guided by the nanowire array structure in order to generate a Kαsource with a small spot size. In our work, the smallest measured source size is comparable to the laser spot size, while the conversion efficiency can reach2.4 × 10-4.     

化纤单体生产的绿色化进程回顾与量化

纵观以往化纤单体生产的革新化措施和绿色化进程,大致可分成3个层面:(1)优化工艺,减少跑冒滴漏;(2)改变反应方式或引入新催化剂;(3)彻底改变原料路线.前两个层面的革新多数能达到节能、降耗、降低生产成本的效果,已取得了较多工业化成果.丁二烯或生物质等原料路线试图从第3个层面解决问题,绿色化虽彻底,但或因引入新的有害物质,或因副产物多,目的产物收率太低,物耗和能耗尚难与传统的芳烃原料路线媲美,工业化道路更艰难.为了推进化纤单体生产的绿色化进程,尽早发现新的切入点,找准绿色化方向,本文综述了前人的绿色化成果,试图从原料路线、制备工艺和"三废"处理3个方面追寻"领跑者"的足迹.针对已有工艺的物耗、能耗和生产成本分析比较以及取舍绿色化革新措施时,常因比较边界(范围)不一致,得出偏颇的观点,误导读者,建议先导入原子经济性(质量效率)评价和全生命周期清单分析等过渡指标,再建立更完善的评价体系,逐步达到严格的全生命周期评价、多维评价的水平.     

基于数值分析的匿名大数据访问最优控制算法

为了降低大数据访问对人们生活的影响,减少因数据访问带来的一系列问题,更好地保护用户的隐私,需要对匿名大数据访问进行控制。当前算法是利用Purpose建立匿名大数据访问模型,在原来的K-匿名算法基础上为Purpose匿名数据访问模型构建算法,该算法对公开信息隐私安全涉及较少,对分布式数据隐私的安全保障效果不理想。为此,提出一种基于数值分析的匿名大数据访问最优控制算法。该算法利用MapReduce编程框架对匿名大数据用户的公钥和私钥进行初始化,将计算代理权授权,用户把需要保存的数据以及授权传送给第三方,也就是代理方签名,实现匿名大数据的审计。根据属性群对匿名大数据访问进行控制,系统管理员构建一棵二叉树,通过对称加密算法与属性群路径密钥,加密的群密钥,产生报头消息,根据上述所获结果,管理员对属性群密钥进行生成、更新和分发。实验结果证明,所提算法计算开销、存储开销以及通信开销较低,匿名大数据访问控制的效率高,具有较强的可实践性,为该领域的研究发展提供了支撑。     

Effects of high pressure sintering on the microstructure and thermoelectric properties of BiCuSeO

Polycrystalline BiCuSeO oxides are prepared by solid-state reaction followed by pressureless sintering (PLS) and high pressure sintering (HPS) methods. Both the experimental results and the density functional theory calculations indicate that the crystal defect concentrations of BiCuSeO can be reduced under the effect of high pressure. By comparing with the PLS sample, a larger power factor and a lower thermal conductivity can be obtained for the HPS sample. The maximum figure of merit ZT～0.4 @ 800?K was obtained for the HPS sample, which is about 3 times higher than the PLS sample. These results indicate that the effect of high pressure is beneficial to modifying the microstructure and improving the thermoelectric performance of BiCuSeO oxyselenide.     

Modeling and analysis of dual-chamber pneumatic spring with adjustable damping for precision vibration isolation

Dual-chamber pneumatic spring with adjustable damping (DCPS-AD) employs a variable orifice mechanism (VOM) to obtain the adjustable stiffness and damping characteristics. These adjustable characteristics are aimed at improving the performance of the pneumatic vibration isolation system (VIS). In order to understand thoroughly how the adjustable parameter of VOM affects the behavior of DCPS-AD, the model of DCPS-AD is derived analytically and validated experimentally. The influence of VOM on the performance of DCPS-AD is analyzed quantitatively. All the results demonstrate that VOM has the ability to vary complex stiffness distribution in frequency domain. Based on these results, the approach optimizing the performance of VIS is proposed, which is realized by adjusting VOM actively. Performance experimental measurements of VIS in frequency domain are carried out under different payload masses. The measurement results validate the proposed approach, which can optimize the performance of VIS when some application conditions varying.     

Synchronization and coupling of Mandelbrot sets

The definitions of synchronization and coupling of two different Mandelbrot sets are introduced. By the nonlinear coupling method, the synchronization and coupling of two different Mandelbrot sets are achieved, which make one Mandelbrot set change to be another and also make two different Mandelbrot sets change to be the same one.     

A water-soluble,small molecular fluorescence probe based on 2-(2′-hydroxyphenyl) benzoxazole for Zn2+ in plants

A water-soluble, small molecular zinc fluorescence probe (ZFP) based on 2-(2′-hydroxyphenyl) benzoxazole was prepared. It exhibited high selectivity and sensitivity to Zn²⁺ than the other metal ions. The highest fluorescence enhancement was observed in the presence of Zn²⁺ owing to the inhibition of excited-state intramolecular proton transfer (ESIPT). Furthermore, fluorescence imaging experiments confirmed that ZFP can be used to monitor Zn²⁺ in biological systems.