基于CP-ABE的云计算改进属性加密安全访问控制策略设计

针对云计算存储中心由于数据和访问控制的安全性无法得到有效保障,从而可能造成用户存储的敏感数据被盗取的问题,现有的解决方法往往通过加密数据密钥,并通过对数据加密来解决安全性问题,但这些方法没有对访问控制的整个过程进行全面的定义和描述,同时仍然具有较大的时空开销。为此,在对CP-ABE(eiphertext-policy attribute-based encryption)进行深入分析的基础上提出了一种基于改进属性加密访问控制模型,然后对CP-ABE进行改进,并对公钥和主密钥的生成、数据所有者加密文件、访问用户解密文件以及用户权限的全面管理过程均进行了详尽的定义和描述,从而设计了一种通用的安全访问机制。在仿真工具Ubuntu中进行实验,结果表明文中方法能有效地实现云计算环境下的安全访问控制,与其它方法相比,具有计算和存储开销低优点,具有较大的优越性。     

基于云模型和VIKOR扩展方法的电网企业科技发展区间值多属性群决策

国家电网公司确立了“一强三优”的战略目标,以公司总体发展战略为基石,集中力量开展科技发展和评估技术的相关研究。因此,对公司科技发展战略进行分析和评估是极其具有现实意义和理论意义的。本文提出了一种基于云模型和VIKOR扩展方法的群决策方法。将语言决策值综合为正态云模型,进而转化为区间值。通过VIKOR扩展方法构建可能度矩阵进行综合群决策。研究表明,针对准则值为语言值或区间值的多属性群决策,该方法可以更加客观有效。     

基于线扫方式的静压气浮激光点云数据扫描误差修正方法研究

为了修正静压气浮激光点云数据扫描误差,提出了一种基于不同扫描速度下所采集的点云数据,通过最小二乘法分区间建立误差预测模型实现对相应误差修正的新方法。实验结果表明,静压气浮三维测量仪的测量精度随气浮导轨扫描速度变化在特定范围内基本呈二次曲线变化关系,该误差修正方法能够快速、准确地实现静压气浮激光点云数据扫描误差的修正,具有较大的适用性和实际参考价值。     

Assessment of Inorganic Fibre Burden in Biological Samples by Scanning Electron Microscopy – Energy Dispersive Spectroscopy

A method based on cloud point extraction (CPE) separation/preconcentration of trace cadmium as a prior step to its determination by graphite furnace atomic absorption spectrometry (GFAAS) has been developed. If the system temperature is higher than the cloud point temperature (CPT) of the nonionic surfactant of p-octyl polyethyleneglycolphenyether (Triton X-100), the complex of Cd²⁺ with 1-(2-pyridylazo)-2-naphthol (PAN) could be extracted into surfactant-rich phase. The chemical variables affecting CPE were evaluated and optimized. Under the optimum conditions, preconcentrating 10.0 mL of water samples permitted a limit of detection of 5.9 ng · L⁻¹ (3σ) for cadmium with an enhancement factor of 50 and a relative standard deviation of 2.1% (n = 11, c = 2.0 ng · mL⁻¹). The method was applied to the determination of cadmium in reference material and water samples with satisfactory results.     

Ammeline–melamine–formaldehyde resins. Preparation and properties

Ammeline–melamine–formaldehyde resins (AMF Resins) containing 5–100 mol % of ammeline, were synthesized by polymerization of the preformed sodium salt of ammeline, melamine, and formaldehyde in basic medium by three methods. These resins, when cured, constitute a new class of thermosets. The rate of hydroxymethylation of the amino groups of the ammeline salt with formaldehyde was somewhat larger then that of the amino groups on melamine. At higher pH values ammeline insolubility was not a problem. The AMF resin composition was approximately equal to the mol ratio of the components originally charged. Both ammeline and melamine were consumed over the entire reaction period. Thus, it is possible to make approximately uniform random ammeline-melamine-formaldehyde resins (AMF) with any mol ratio of ammeline salt to melamine. By controlling the pH of the solution from which the resins were isolated, the (SINGLE BOND) O⁻ Na⁺/(SINGLE BOND) OH ratio could be varied. Resin melting points varied widely with the mol fraction of ammeline and the (SINGLE BOND) O⁻ Na⁺/(SINGLE BOND) OH ratio. AMF resin solubilities, shelf lives, cloud points, and water tolerance depended upon the method of preparation, pH, and other factors. The sodium salt of ammeline was hydroxymethylated in water more readily than ammeline. More highly methylolated ammeline species were readily formed in solution but upon precipitation only bis-N-hydroxymethylammeline was isolated. © 1996 John Wiley & Sons, Inc.     

Synthesis and characterization of amphiphilic diblock copolymers of methyl tri(ethylene glycol) vinyl ether and isobutyl vinyl ether

Water-soluble diblock copolymers of methyl tri(ethylene glycol) vinyl ether (hydrophilic block) and isobutyl vinyl ether (hydrophobic block) of different molecular weights and composition were synthesized by living cationic polymerization. The molecular weight and comonomer composition of these copolymers were determined by GPC and ¹H NMR spectroscopy, respectively. Aqueous solutions of the copolymers were characterized in terms of their micellar behavior using dynamic light scattering, aqueous GPC, and dye solubilization. All the copolymers formed aggregates with the exception of a diblock copolymer with only two hydrophobic monomer units. The micellar hydrodynamic size scaled with the 0.61 power of the number of hydrophobic units, in good agreement with a theoretical exponent of 0.73. An increase in the length of the hydrophobic block at constant hydrophilic block length or an increase in the overall polymer size at constant block length ratio both resulted in lower critical micelle concentrations (cmcs). The cloud points of 1% w/w aqueous solutions of the polymers were determined by turbidimetry. An increase in the length of the hydrophobic block at constant hydrophilic block length caused a decrease in the cloud points of the copolymers. However, an increase in the overall polymer size at constant block length ratio led to an increase in the cloud point. © 1996 John Wiley & Sons, Inc.     

染料云的形态结构表征—染料的径向分布与投影密度分布

彩色影像的最小像元-染料云的形态结构的表征有两种方法:一种是染料云的染料浓度的径向分布;另一种是染料云的投影密度分布。前者一般是从染料云形成过程的模拟计算得到;后者是从微密度计对染料云的扫描测得。本文提出了将染料的径向分布转换成相对投影密度的一种近似计算方法,从而使两种形式的表征方法相互联系起来,这为进一步优化染料云形态的研究打下基础。     

基于邻域特征点提取和匹配的点云配准

为解决噪声干扰、数据丢失情况下迭代最近点算法的鲁棒性差、配准精度低等问题,提出一种基于邻域特征点提取和匹配的点云配准方法.首先定义一个由点的k邻域曲率、点与邻近点的法向量内积均值以及邻近点与邻域拟合平面的欧氏距离方差等三部分组成的邻域特征参数,结合在移动最小二乘表面构造的曲率特征参数对点云进行两次特征点提取;其次依据直方图特征定义三个匹配条件,并用双重约束获得正确的匹配点对;最后在配准阶段,采用双向构建k维树的迭代最近点算法实现精确配准.实验结果表明,该算法的配准精度较迭代最近点算法提高了90%以上,并且能够在噪声环境下有效地完成缺失点云的配准,在鲁棒性和精确配准方面有明显优势.     

爆炸烟云扩散的时空分布模型及特性

针对爆炸烟云扩散的时空分布问题,在严格限定实验条件的前提下,设计并开展了不同当量、不同地面条件、不同炸药装置壳体厚度的3组TNT爆炸烟云扩散外场实验,获得了不同实验条件下烟云扩散时空分布数据,运用计算流体力学(computational fluid dynamics, CFD)对爆炸烟云的扩散过程进行了数值模拟。通过分析实验和数值模拟获取的烟云时空分布数据,得到了烟云扩散形态演变过程及浮力流场信息,确定了厚水泥地面条件和硬质地面条件下不同的爆炸烟云扩散高度分布模型。研究结果表明:采用实验与数值模拟相结合的方法来表征烟云时空分布模型是科学可行的,爆炸烟云高度随时间呈1/2次幂函数增长,烟云宽度短时间内几乎呈线性扩展,烟云温度随时间呈反比例函数衰减,爆轰地面条件和炸药装置壳体厚度对烟云扩散高度均有不同程度的影响。     

基于交互正交实验的玉米淀粉粉尘云最低着火温度的影响因素研究

采用Godbert-Greenwald (G-G)恒温炉装置,运用交互正交实验方法,研究了粉尘质量浓度、分散压力、CaCO_3质量分数及其交互作用对玉米淀粉粉尘云最低着火温度(minimum ignition temperature of dust cloud,MITC)的影响规律。通过直观分析法和方差分析法考察了各因素及其交互作用对玉米淀粉粉尘云最低着火温度影响,2种分析方法得出的结论一致。结果表明:CaCO_3质量分数和粉尘质量浓度对玉米淀粉粉尘云最低着火温度影响高度显著;分散压力与粉尘质量浓度对玉米淀粉粉尘云最低着火温度的影响存在交互作用,分散压力与粉尘质量浓度的交互作用对玉米淀粉粉尘云最低着火温度的影响显著。