多层多维事元可拓集及其运算

为了建立复杂系统的事元可拓模型,针对现实世界中具有多层结构、每个子层次结构又具有多个特征的复杂系统中各子系统的相互作用问题,从可拓学原理出发,在n维事元可拓集概念的基础上,提出了多层多维事元可拓集及其正域、负域、拓界的概念. 给出了多层多维事元可拓集的正可拓域、负可拓域、正稳定域、负稳定域的定义. 研究了多层多维事元可拓集的交运算等,讨论了有关性质,并对性质进行了严格证明,得到了多层多维事元可拓集交的可拓域、稳定域的表达式.     

基于原子防护的SM2算法实现及简单功耗分析

SM2算法是中国商用椭圆曲线公钥密码标准算法。SM2算法实现过程中如不加防护措施,攻击者利用简单功耗分析(simple power analysis, SPA)即可破解私钥。为有效防御SPA攻击,提高算法性能,以安全芯片为基础,针对椭圆曲线标量乘运算采用优化的原子防护方法,软硬件实现了SM2算法。同时搭建安全评估环境,进行安全分析实验。结果表明,原子块内功耗波形变化规律基本一致,但原子块间局部功耗波形随着标量乘系数比特值不同而存在明显差异,从而导致私钥泄露,成为信息安全隐患。针对泄露位置进行原因分析,提出了改进的实现策略。实验结果表明所提出的策略可有效抵御SPA攻击。     

方波阳极溶出伏安法同时测定溶液中Cd（Ⅱ）、Pb（Ⅱ）、Cu（Ⅱ）、Bi（Ⅲ）离子的多元校正方法

方波阳极溶出伏安法同时测定Cd（Ⅱ）、Pb（Ⅱ）、Cu（Ⅱ）和Bi（Ⅲ）,由于谱峰重叠面无法直接进行分析,为此提出一种基于化学计量学同时定量分析的方法.在0.1,mol/L柠檬酸铵溶液中,以银基汞膜电极为工作电极,采用方波阳极溶出伏安法结合偏最小二乘（PLS）回归方法,用于同时定量分析溶液中Cd（Ⅱ）、Pb（Ⅱ）、Cu（Ⅱ）和Bi（Ⅲ）离子.由于Cu（Ⅱ）和Bi（Ⅲ）离子的溶出峰严重重叠,采用偏最小二乘回归方法进行定量分析.以39个样品作为训练集建立了PLS回归模型,各离子浓度范围分别是Cd（Ⅱ）0.10～2.56,μg/mL、Pb（Ⅱ）0.20～2.66,μg/mL、Cu（Ⅱ）0.10～2.56,μg/mL、Bi（Ⅲ）0.60～3.06,μg/mL.采用另外10个样品作为验证集对模型进行了评价,得到4种离子的回收率分别为92.3%～103.0%、94.7%～106.0%、89.0%～105.0%和94.8%～108.0%.与传统的单变量校正方法相比,多元校正方法可以用于重叠溶出伏安信号的定量分析.     

混沌范德玻-杜芬系统参数自适应反步设计

针对一类具有多个未知参数的混沌ADVP(范德玻-杜芬)系统,设计自适应镇定控制器.基于反步法思想,对所有未知参数设计自适应估计律,结合反步思想为一类不确定混沌系统设计自适应控制器.设计出的控制器只需施加于一个子系统,使得控制的实现更加方便.整个设计过程只须作一次极点配置和求解一个李雅普诺夫方程,简化了计算,得到了简单且易实现的标量控制器.仿真结果表明:受控系统能快速达到收敛.     

Insights on cellulose hydrolysis in the porous structure of biomass particles using the lattice Boltzmann method

Lignocellulose biomass has been recognized as one of the most promising sources of low-cost and renewable biofuels, and its conversion into alternative fuels and valuable platform molecules has attracted widespread attention. The porous solid residue from lignocellulose biomass, which was pretreated by steam-stripping, is catalyzed by dilute sulfuric acid to form levulinic acid (LA). The process includes porous media diffusion, multicomponent reactive transport, liquid-solid interface reaction, and cellulose dissolution. Understanding the interactions between these complex physicochemical processes is the basis for optimizing the performance of the hydrolysis reaction. In this study, a porous reaction transport model based on the lattice Boltzmann method (LBM) was established to simulate the conversion of cellulose to LA which was catalyzed by dilute acid. The simulation results were compared with the existing experimental results to verify the accuracy of the model. The simulation results showed that temperature has a significant effect on hydrolysis and the highest carbon yield was obtained at 180 °C. Without considering the lignin reaction, the higher the sulfuric acid concentration, the better is the hydrolysis efficiency in the range of 4% – 8%. The influence of cellulose content and steam-stripping the residue porosity on the dissolution rate of cellulose was also evaluated. The average dissolution rate of cellulose is the highest within 75 min, when the porosity is 0.7 and the cellulose content is 50%.     

一种基于Logistic方程的图像加密算法

基于Logistic方程的图像加密提出了一种算法,首先在一维Logistic混沌方程的基础上提出广义Logistic方程的模型,然后在分析研究广义Logistic方程的相图轨迹基础上,设计一种带有一次耦合项的二维广义Logistic方程.发现该方程当控制参数值在某一范围内变化时产生稳定的不动点,并分析得出这是一个多周期...     

黑色旅游外文文献研究述评

黑色旅游是对传统旅游的否定与突破,是后现代主义在旅游学科内的"一个暗示".在对黑色旅游外文文献系统梳理的基础上,得出目前西方黑色旅游的研究现状:(1)到与死亡及灾难有关的景点旅游不一定是黑色旅游,需要从旅游动机及体验的角度来定义黑色旅游;(2)黑色旅游与相关概念之间的关系界定不清;(3)供给角度的描述性研究多于需求角度的描述性研究;(4)定性研究多于定量研究;(5)以西方为中心的研究视角多于世界其他地方.最后提出狭义与广义黑色旅游概念的区别,希望为国内黑色旅游的理论研究或实际开发提供参考.     

仿射非线性系统状态方程的任意阶近似解

针对典型的仿射非线性系统,采用常微分方程理论对其进行求解.首先将系统在平衡点附近进行展开,求得其齐次方程的解,然后利用常数变易法将非线性微分方程变为等价的第二类非线性Volterra积分方程.采用逐次逼近法,求得任意阶近似解,并证明解的收敛性.     

Three-year changes of surface albedo of degraded grassland and cropland surfaces in a semiarid area

Diurnal, seasonal and interannual variations of surface albedo of degraded grassland and cropland surfaces at a semiarid area of Tognyu have been investigated based on the continuous three years observational data from 2003 to 2005. The changes of surface albedo with solar elevation angle and soil moisture have been discussed also. It has been found that surface albedo has almost the same diurnal and seasonal variations on degraded grassland and cropland surfaces in the semiarid area, while surface albedo is large in winter and small in summer. The diurnal variation of the surface albedo has relationship with the weather condition. The diurnal cycle of the surface albedo likes the ＂U＂ shape curve in sunny day, while it is low-high after the rain, and high-low after the snow. The surface albedo has large variation in cloudy day, while it has no any variation in overcast day. The large difference of the surface albedo can be 0.04 in winter between two land surfaces, because the snow has large effects on the surface albedo in winter. The rainfall is an important factor in summer on the surface albedo, while the difference of the surface albedo is 0.01 only between two land surfaces. The differences of the surface albedo can also be 0.04 in autumn due to vegetation growing. The seasonal-average surface albeo from 2003-2005 is 0.25, 0.22, 0.24, 0.32 respectively in spring, summer, autumn and winter on the degraded grassland surface, while it is 0.25, 0.21,0.22, 0.33 respectively in spring, summer, autumn and winter on the cropland surface. The surface albedo becomes smaller with the increase of solar elevation angle. When the solar elevation angle is greater than 40°, the surface albedo changes very little and tends to be a constant. The surface albedo has negative exponent functions with soil moisture in the growing season.     

图书馆网站的标准化问题研究

本文从图书馆网站标准化的含义入手,通过选取七家大型图书馆网站为样本进行校验测试,进一步论述了网站标准化的必要性,在此基础上提出了进行网站标准化建设工作的具体对策。