液氮温区同轴脉冲管制冷机的实验研究

脉冲管制冷机冷头朝上布置可以使制冷机与超导器件的耦合更方便 ,但对G -M型脉冲管制冷机 ,重力会对这种布置方式产生不利影响。对双向进气型脉冲管制冷机 ,直流和耦合传热会共同影响脉冲管制冷机的性能。介绍了液氮温区G -M型同轴脉冲管制冷机的实验结果 ,主要研究了蓄冷器温度分布和重力对脉冲管制冷机性能的影响     

Development of Bi(Pb)-2223/Ag pancake-shaped and solenoidal coils

High temperature superconducting (HTSC) multifilamentary (MT) Bi(Pb)-2223/Ag tapes with reproducible critical current density of between 15000 and 20000 A/cm² at 77 K in self field have been achieved using the standard flat-rolling method as the intermediate deformation between sintering periods. Long lengths of Bi(Pb)-2223/Ag MT tapes up to 43 m prepared by the conventional method of powder-in-tube (PIT) have been successfully produced on a laboratory scale. Several coils have been fabricated from sections of the long length tape, using the co-wound wind-and-react (W&R) procedure for the pancake-shaped and the singly-wound W&R as well as R&W procedure for the solenoidal coils. A novel W&R solenoidal coil (reaching ~973 ampere-turns) wound on an alumina ceramic tube generates a DC field of ~19 mT at 77 K and has been fabricated together with five pancake-shaped coils, each generating an average of ~5 mT at 77 K. These are destined for magnet construction with a possible combined calculated field of ~0.04 T at 77 K (with liquid nitrogen as a coolant)     

轻武器射击精度影响因素剖析

从弹药和武器的角度，分析影响轻武器射击精度的诸主要因素。并针对诸主要因素提出相应的改进建议，为提高武器系统精度的研究提供参考。     

Preparation and characterization of transparent ZnO/epoxy nanocomposites with high-UV shielding efficiency

Transparent ZnO/epoxy nanocomposites with high-UV shielding efficiency were reported in this paper. First, zinc oxide (ZnO) precursor was synthesized via the homogeneous precipitation method and ZnO nanoparticles were then made by calcination of the precursor at different temperature. The structural properties of the as-prepared ZnO nanoparticles were studied in detail using thermogravimetry (TGA), differential thermal analysis (DTA), X-ray diffractometer (XRD), Fourier transform infrared spectrometer (FT-IR) and transmission electron microscopy (TEM), respectively. Transparent ZnO/epoxy nanocomposites were subsequently prepared from transparent epoxy (EP-400) and as-prepared ZnO nanoparticles via in situ polymerization. Optical properties of ZnO/epoxy nanocomposites, namely visible light transparency and UV light shielding efficiency, were studied using an ultraviolet-visible (UV-vis) spectrophotometer. The optical properties of the as-obtained nanocomposites were shown to depend on ZnO particle size and content. The nanocomposite containing a very low content (0.07% in weight) of ZnO nanoparticles with an average particle size of 26.7 nm after calcination at 350 °C possessed the most optimal optical properties, namely high-visible light transparency and high-UV light shielding efficiency, that are desirable for many important applications.     

On the Cutoff Wavelength of Rectangular-Shaped Microshield Line by Edge Element Method

In this paper, the cutoff characteristic of rectangular-shaped microshield transmission line has been analysed by edge element method. Dependence of cutoff wavelengths on the thickness of metallic signal strip, dielectric constant of dielectric substrate and the width of the rectangular-shaped ground conductor are presented in tabular form. Numerical results in this paper have important values in design of rectangular-shaped microshield lines in microwave and millimeter wave integrated circuits.     

产品设计方案的多目标决策分析及其智能支持系统

用模糊多目标决策方法对产品设计方案进行决策分析并设计出相应的智能计算机支持系统，实例证明这一方法在实际应用中是有效的和可靠的。     

多相物质粉末衍射的物相检索

讨论了多相物质粉末衍射的物相检索问题，介绍了XRDS的物相检索软件。这是一种智能型的物相检索程序，考虑了测试数据的不确定度，以及粉末样品和块状样品衍射图谱各自的特点，不仅注意到实际样品中微量物相存在的可能，也注意到块状样品结构有序性的可能。XRDS能够帮助材料工作者同时检出样品中所含的多种物相及其含量，操作简单、结果可靠。     

西北地区水资源现状与可持续利用对策的探讨

中国的水资源问题在西北地区尤为突出.西北地区生态环境脆弱,资源丰富,如何在发展经济的同时实现人与自然的和谐共处,已成为人们日益关心的话题.随着国家西部大开发战略的进一步推进,特别是实施西部大开发的近五年,切实采取有效措施以实现西部地区水资源的可持续利用,已经逐渐成为人们的共识.从分析西北地区水资源现状入手,根据西北地区水资源的特点,提出西北地区水资源可持续利用的对策①加大地下水资源勘查力度,查清水资源储量;②综合利用,科学规划,加强水资源的合理配置与调控;③开源与节流并举,尤其要重视节流;④充分利用天然地下库容调蓄水资源;⑤完善相关法律和法规的建设,强化监督管理加强和完善水资源法规建设,建立健全水资源管理体系.通过以上措施的实施将有利于解决西北地区水资源的严重短缺问题.     

Restraining the associations of anthracene fluorophore by chemically linking to poly(methyl methacrylate)

Associations (dimer or aggregate) of anthracene (An) fluorophores tend to interrupt the monomer emission and reduce the quantum yield (Φ_PL); therefore, poly(methyl methacrylate) (PMMA) chain was used in this study to chemically link to anthracene and to block the mutual associations among the anthracene fluorophores. With this aim, the target polymers were prepared by anionic polymerizations with 9,10‐dibromoanthracene/s‐butyllithium as initiating system to proceed polymerizations of methyl methacrylate (MMA) directly or in the presence of 1,1‐diphenylethylene (DPE). Use of DPE before addition of MMA produces stable initiating anionic species and avoids potential side reactions during polymerization; however, it also introduces four β‐phenylene rings around the central anthracene ring, which interfere with the corresponding emission pattern and reduce the Φ_PL (32%) value due to potential interactions between phenylene rings and anthracene. On the contrast, polymerization without participation of DPE results in polymer with central anthracene ring directly connected to two PMMA chains, which gives clean vibronic emission pattern with limited association emissions and enhanced Φ_PL (52%) value. Physical blending of anthracene by PMMA is less efficient to restrain the associations and results in a film of lower Φ_PL (20%). © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008