脉冲载荷下柱壳结构响应实验研究

利用电子束及化爆对柱壳模拟结构进行脉冲加载，通过试验研究结构响应规律及结构破坏阈值，对壳体结构响应的基本理论进行了论述和分析；根据电子束及化爆加载实验结果，重点分析了不同结构的破坏阈值；提出了提高柱壳壳体抗脉冲载荷能力的技术途径。     

Synthesis,structural, linear and nonlinear optical properties of chromium doped SnO2 thin films

The present work concentrates on some physical investigation of the undoped and Cr doped SnO₂ thin films deposited onto precleaned glass substrates by the spray pyrolysis system. The physical properties of the undoped and Cr doped SnO₂ thin films were investigated by the X-ray diffraction (XRD), atomic force electron microscope (AFM), field emission scanning electron microscope (FESEM), four-probe method and double beam spectrophotometer. The undoped and Cr doped SnO₂ films display a polycrystalline nature with orthorhombic crystal structure. The linear optical constants energy gap E_g, refractive index n, absorption coefficient α, static refractive index n_o, oscillation energy E_o, dispersion energy E_d and the Urbach energy of the undoped and Cr doped SnO₂ thin films were evaluated. The investigated films exhibit a direct energy gap and their values decrease with the increasing of Cr doping content while the Urbach energy follows a reverse behavior. On the other hand, the nonlinear optical constants (third-order nonlinear susceptibility ${\mathit{\chi }}^{(3)}$ and nonlinear refractive index n₂) have been increased with increasing the Cr doping content. Finally, it has been found that the sheet resistance and conductivity of the synthesized thin films were enhanced by increasing the Cr doping content. The 5?wt% Cr doped SnO₂ thin film has a high value of the figure of merit among other films.     

Effects of brief milling and acid treatment on two ordered and disordered kaolinite structures

The structural characteristics of well-ordered kaolinite (K1) and poorly ordered kaolinite (K2) after the ¼ h milling procedures, continuing acid activation with 2 M hydrochloric acid and intercalation ability with urea were assessed. Kaolinite samples were examined by X-ray powder diffraction, thermogravimetry, infrared spectroscopy analysis and specific surface area measurement. Kaolinite K1 contained a slightly higher portion of particles <2 μm (38 vol.%) than K2 (31 vol.%) increasing after jet milling (to 92 vol.% and 54 vol.%, respectively), but decreasing slightly after ball milling (to the 37 vol.% and 26 vol.%, respectively). The acid treatment contributed to a narrower particle size distribution, increased value of the surface area and dehydroxylation temperature and improved the structural order of poorly ordered kaolinites. Maximum surface area SSA = 45 m²g^{− 1} was measured for K2 after ball milling and treatment with hydrochloric acid. Treatment of kaolinites with hydrochloric acid supports their ability to intercalate urea and exfoliate, while the mechanical millings adversely affected intercalation urea. The SSA 9.8 and 20.5 m²g^{− 1} of K1 and K2, respectively, changed after: (1) exfoliation to 21.0 and 34.1 m²g^{− 1}, respectively, (2) jet milling and exfoliation to 38.0 and 42.0 m²g^{− 1}, respectively, (3) ball milling and exfoliation to 20.3 and 34.4 m²g^{− 1}, respectively, and (4) ball milling, acid treatment and exfoliation to 40.3 and 46.7 m²g^{− 1}, respectively.     

An integrated assembly method of sandwich structured ceramic matrix composites

Sandwich structured composites have been widely studied and applied at ambient temperature in aeronautical, automobile and naval applications. For high temperature applications, an integrated ceramic sandwich structure could take advantage of multiple functions such as skin stiffness and core insulation. For thermo-structural applications, skins must be made of ceramic matrix composites (CMC) because of their strength, their resistance to high temperatures (beyond 1000 °C), and their low densities. Concerning foam cores, some carbides (e.g. SiC) are, for their outstanding thermo-mechanical properties, the most appropriate. These foams can withstand long oxidative exposing conditions with low material degradation. This paper presents an assembly method of SiC based sandwich structured CMC. It is performed during sandwich manufacturing in an integrated fashion and allows the production of complex shapes at low costs. Produced flat sandwich panels, characterized by three point bending tests, showed a marked toughening behaviour.     

Superconductive superhard phase of BC7: Predicted via ab initio calculations

We present a first-principles study on a phase of BC₇ with Amm2 space-group symmetry (we call o-BC₇), which is selected from more than a dozen of candidates via energetic, mechanical and dynamical stabilities within a wide pressure scale from 0 to at least 100 GPa. Our calculated results show that this structure is highly incompressible with large bulk and shear modulus of 388 GPa and 430 GPa, respectively, which is even higher than cubic BN. Further investigations revealed that the Vickers hardness (H_v ≈ 49.5 GPa) is higher than t-BC₃ reported recently. And the superconducting critical temperature is calculated to be 38 K, which is comparable to that of MgB₂.     

浅谈冷却塔塔体结构的分类与特点

在水资源和环境问题日益突出的今天,在工农业生产和人民生活中广泛应用的冷却设备——冷却塔对于节省水资源和保护环境发挥了重要的作用.从冷却塔塔体结构材料的角度对不同塔体结构的特点进行了阐述和分析,并对其进行了比较,以供在冷却塔选型、设计时参考.     

Yttrium doping of Ba0.5Sr0.5Co0.8Fe0.2O3-δ part II: Influence on oxygen transport and phase stability

Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3-δ (BSCF) in its cubic perovskite phase has attracted much interest for potential use as oxygen transport membrane (OTM) due to its very high oxygen permeability at high temperatures. However, performance degradation due to a sluggish phase decomposition occurs when BSCF is operated below 840?°C. Partial B-site substitution of the transition metal cations in BSCF by larger and redox-stable cations has emerged as a potential strategy to improve the structural stability of cubic BSCF. In this study, the influence of yttrium doping (0…10?mol-%) on oxygen transport properties and stability of the cubic BSCF phase is assessed by in situ electrical conductivity relaxation (ECR) and electrical conductivity measurements during long-term thermal annealing both at 700?°C and 800?°C. Detailed phase analysis is performed by scanning electron microscopy (SEM) after long-term annealing of the samples in air at different temperatures.     

网络管理信息系统安全对策探索

网络管理信息系统的应用越来越广泛，这时网络管理信息的安全提出了更高的要求，本文针对网络管理信息系统的特点，提出了一个网络管理信息系统的安全结构模型，分析了相应的安全对策。     

辽河和胜利焦化蜡油组成的初步研究

研究了辽河、胜利焦化蜡油的组成，考察了硫、氮、残炭在焦化蜡油中的分布，采用改进的Ｂ－Ｌ法、ｎ－ｄ－Ｍ法计算了辽河、胜利焦化蜡油的结构参数，并与大庆焦化蜡油文献数据进行了比较，讨论了焦化蜡油中氮对掺炼的影响。     

一个结构优化的能量方法

本文提出了一种用于结构最优材料分布的能量方法.该方法将结构在一定约束条件下的承载能力转化成结构吸收应变能的能力.文章给出了拉格朗日函数, 通过包括对区域的变分确定材料分布.文中以悬臂梁为例说明了这一方法,并就此情况给出了解析解.若将位移约束以外力势能项代替,那么得到的结果相同.为了说明对较复杂情况的处理.本文建议用离散化方法进行数值解,仍以悬臂梁为例加以说明,结果表明,数值解收敛于前面的解析解.