碳还原剂加入方式对粉煤灰氮化反应的影响

通过碳还原氮化反应,从工业废料粉煤灰制备氮化陶瓷类材料.采用氮/氧分析仪测定产物氮含量,评价氮化反应程度;以BET氮气吸附法测定比表面积,分析粉体活性;以扫描电镜分析样品表面形貌;以热重分析仪测定碳含量,X射线能谱仪估计元素组成.比较机械混合法、超声法和高能球磨法3种碳加入方式.结果表明,粉煤灰自身含碳的还原活性处于机械混合法和高能球磨混合法之间,高能球磨法对提高反应混合物活性最有效,所得产物结晶氮含量最高,质量分数可由0.3 %提高到23.1%.     

以Kriging可靠度分析为基础的半无限规划

基于可靠度的结构优化设计是国内外积极探索和研究的重要课题,但是传统的两层次算法的最大缺点就是计算效率很低,甚至有时不能够得到收敛解.因此有必要对这一类问题进行研究和探索,寻找新的计算方法以降低计算成本.本文将Kriging方法应用于带可靠性约束的优化设计中,将双层规划问题转化为一个带有无穷多个约束的半无限规划问题,然后使用Kriging模拟来近似地替代结构重分析,使得优化过程中的结构重分析次数减少,在保证计算精度的同时使计算效率得到较大提高.     

基于KPCA和SVM的火箭发动机试验台故障诊断方法

为了解决液体火箭发动机试验台的故障诊断问题,提出了一种基于核主元分析(KPCA)特征提取和支持向量多分类机(SVM)的故障诊断方法,该方法首先利用核主元分析对试验台标准故障样本进行特征提取,通过特征分析,建立适合于试验台故障状态识别的层次多分类支持向量机,并对其进行训练,然后将试验数据在主元上投影,输入到训练好的支持向量多分类器,对试验台故障状态进行识别.该方法充分利用了核主元分析强大的非线性特征提取能力和支持向量分类机良好的小样本泛化特性,解决了试验台故障诊断中的小样本、非线性模式识别问题.对试验台的试验结果表明,该方法是有效的、可行的.     

通用突变控制方法及其在潜艇中的应用

运用非线性动力学和突变理论,研究了高维系统建立具有理想特性突变的控制方法.引入冲失滤波器保证系统平衡点不变,并利用隐式判据、中心流形定理以及规范形法确定控制增益.以潜艇空间运动为例,阐述计算的全过程.该控制方法简便、快捷,可广泛应用到实际控制系统的设计中.     

一种块递推实时FFT算法模块设计与实现

文中提出了一种基于FPGA-IP核的FFT算法硬件模块的设计方案,该方案采用四分块递推FFT算法,具有结构规范、递推性好、实时性强等特点,结合DSP对模块的数据输入和输出的软件控制,实现了一种硬件和软件相结合的实时FFT模块.对该模块性能进行测试,FFT模块运行稳定,输出的计算结果正确,与DSP软件实现的标准FFT算法程序库相比,文中的FFT模块实时性能提高了35倍,该模块已被用于实时信号处理系统中.     

基于广义AIC和RPC的OFDM航空信道估计算法

文章通过对航空信道的分析,指出其稀疏信道特征,使用普通算法对此信道进行信道估计会引入高阶矩阵运算,为加快收敛速度、降低实现难度,文中提出了一种利用GAIC(generalized Akaike information criterion)准则和RPC(repeated phase-rotated Chu)训练序列的OFDM航空信道LS(1east squares)估计方法,该方法利用GAIC准则确定信道模型的阶次及抽头位置,为减小信道估计的运算复杂度,引入RPC序列作为训练序列,既满足了LS(least squares)估计,又大大简化了计算复杂度.文章针对具体应用给出文中算法的性能仿真结果,证明了此算法可避免高阶矩阵运算,节约了大量权值可忽略抽头所引入的资源占用和计算量,且显著减小估计误差,可更好跟踪快变的稀疏信道.     

Corrosion behavior and mechanism of the automotive hot-dip galvanized steel with alkaline mud adhesion

The corrosion behavior and mechanism of hot-dip galvanized steel and interstitial-free (IF) substrate with alkaline mud adhesion were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), electrochemical impedance spectroscopy (EIS), and linear polarization. The results show that non-uniform corrosion occurs on the galvanized steel and IF substrate during 250 h with the mud adhesion. The corrosion products on the galvanized steel are very loose and porous, which are mainly ZnO, Zn5(OH...     

Temperature distribution and dynamic control of secondary cooling in slab continuous casting

To predict and optimize the temperature distribution of slab continuous casting in steady operational state, a three-dimensional model (named offline model) based on the heat transfer and solidification theories was developed. Both heat transfer and flux distribution characteristics of the nozzle sprays on the slab were considered, and the complicated boundary condi-tions, such as spray cooling, natural convection, thermal radiation as well as contact cooling of individual rolls were involved in the model. ...     

Preparation and mechanical properties of polypropylene fiber reinforced calcined kaolin-fly ash based geopolymer

To improve the environmental benefits and solve the problems of large shrinkage and high brittleness, the partial replacement of calcined kaolin by fly ash as a raw material for geopolymer synthesis and the influences of polypropylene (PP) fiber on the mechanical properties and volume stability were investigated. The results show that compressive strength of the geopolymer containing 33.3%(mass fraction) fly ash by steam curing at 80 °C for 6 d is improved by 35.5%. The 3-day compressive strength, flexural strength and impacting energy of geopolymers containing 0.05%PP fiber increase by 67.8%, 36.1% and 6.25%, while the shrinkage and modulus of compressibility decrease by 38.6% and 31.3%, respectively. The results of scanning electron microscopy (SEM) and the appearances of crack growths confirm that PP fiber can offer a bridging effect over the harmful pores and defects and change the expanding ways of cracks, resulting in a great improvement of strength and toughness. Foundation item: Project(2006AA06Z225) supported by the National High-Tech Research and Development Program of China     

浙江高等教育均衡发展的思考

浙江高等教育均衡发展,主要是指浙江省内不同地市之间、城乡之间、同一地市不同高校之间、同一高校不同群体之间的均衡发展。本文主要研究浙江高等教育的“三大均衡”,即：地市间实现均衡发展,只研究11个地市高校的均衡布局问题;城乡间实现均衡发展,只研究城乡高校的均衡布局,尤其是县级社区学院的发展问题;高校间实现均衡发展,只研究不同高校学科带头人的均衡布局问题。