闸板式调节阀工作性能的试验与研究

闸板式调节阀在现场的试验结果,研究调节阀随锅炉负荷的变化时的工作特性,测试出该种调节阀门的流量系数。     

Low-temperature Properties of Biodiesel： Rheological Behavior and Crystallization Morphology

A soybean oil derived biodiesel was prepared and blended with a conventional No. 0 petrodiesel. The pour points (PP) and the cold filter plugging points (CFPP) of biodiesel blends were evaluated on a low-temperature flow tester. Dynamic viscosities of the blends at different temperatures and different shear rates were measured on a rotary rheometer. The crystal morphologies of biodiesel blends at low temperatures were analyzed using a polarizing microscope. The results indicated that blended fuels demonstrated slight decrease in PPs and CFPPs as compared with those of neat soybean oil derived biodiesel and pure petrodiesel. Below the temperatures of PPs or CFPPs, the dynamic viscosity of biodiesel blends dramatically increased with a decreasing temperature, but decreased with an increasing shear rate, so that biodiesel blends exhibited non-Newtonian behavior. At temperatures higher than PPs or CFPPs, a linear relationship appeared between the dynamic viscosity and shear rate and biodiesel blends became Newtonian fluids. At low temperatures, wax crystals of biodiesel blends grew and agglomerated rapidly. Loss of fluidity for biodiesel blends at low temperatures could therefore be attributed on one hand to the sharp increase of viscosity and on the other hand to the rapid growth and agglomeration of wax crystals.     

掺钇(Ba,Sr,Ca)TiO_3纳米粉体及细晶陶瓷的制备与性能

采用sol-gel法制备了Y3+掺杂Ba0.90Sr0.08Ca0.02TiO3(BSCT)纳米粉体及细晶陶瓷。通过TG-DTG、XRD、SEM和TEM对样品结构及形貌进行了表征,并测试了陶瓷的介电性能。研究表明,Y3+掺杂BSCT纳米粉体主要为立方相BaTiO3,烧结后陶瓷晶粒尺寸在0.68~2.24μm可控,Y3+掺杂可以抑制陶瓷晶粒的生长,使陶瓷的tC向低温方向移动。随Y3+掺杂量的增大,陶瓷的介电温谱εr-t趋于平缓,当x(Y3+)为7.0%时,陶瓷的室温εr大幅度提高到9 176。     

基于QPSO优化算法的余弦调制滤波器组设计

提出了一种新的余弦调制滤波器组设计方法,此方法以原型滤波器的阻带衰减作为目标函数,用改进型量子粒子群算法(QPSO)设计最接近满足重构条件的原型低通滤波器,然后在此基础上通过余弦调制得到分析滤波器组和综合滤波器组.实验仿真结果表明,用此方法设计的余弦调制滤波器组(CMFB)具有良好的阻带衰减特性和精确重构性能,在满足性...     

变压器局部放电在线监测中的自适应滤波技术研究

根据自适应滤波原理提出了变压器局部放电在线监测的自适应滤波方法,由该方法编制了局部放电在线监测的自适应滤波软件。模拟试验结果表明,该方法能有效地抑制外部电磁干扰信号、提高信噪比。     

基于内蕴时间理论的地基沉降问题研究

应用基于内蕴时间理论的土流变性研究的有关结论对地基沉降问题进行了探讨。给出了地基沉降随时间变化的计算公式 ,然后对公式进行了验证 ,并且把所得到的地基沉降计算公式与现有的具有代表性的地基沉降公式进行了对比。结果表明本文给出的公式具有较好的准确性     

设计余弦调制QMF组的一种新方法

通过适当矩阵变换，本文首先将精确重建余弦调制正交镜像滤波器组的设计转化为一种带约束的非线性优化问题，它是一种带二次型约束的最小二乘（ＱＣＬＳ）优化问题，然后，我们提出了一种变参量的罚函数方法来有效求解该类ＱＣＬＳ优化问题，通过直接采用原型滤波器系数为优化变量，我们构造了一个特殊的凸函数作优化代价函数，故可获得该问题的全局最小点，最后，采用本文提出的设计方法进行了一个具体实例设计，结果表明我们的方法     

Energetic nitrocellulose coating: effective way to decrease sensitivity and modify surface property of HMX particles

Modifying the surface properties of energetic materials has theoretical and practical significance in the field of their application. In this paper, irregular cyclotetramethylene tetranitramine (HMX) particles were successfully coated by energetic nitrocellulose (NC), leading to the uniform NC-coated HMX particles. As coating materials, energetic (NC was chosen to decrease the sensitivity and modify the surface property of HMX particles, in order to expand their application furthermore. Scanning electron microscopy, laser particle size analysis, energy dispersive spectrometer, and Fourier-transform infrared (FT-IR) spectra were utilized to investigate the morphology, size, and coating quality of NC-coated HMX particles. These results indicated the effective preparation of composites structure. Moreover, the thermal behaviors of NC-coated HMX particles were investigated by simultaneous thermogravimetric and differential scanning calorimetry analysis, coupled with FT-IR and mass spectroscopy. These results showed that NC did not induce chemical properties change of HMX, only physical hydrogen bond was formed in the coating process. Finally, the friction sensitivity, impact sensitivity, and surface properties NC-coated HMX were investigated, and the results suggested that NC-coated HMX particles had better safety and depicted stronger interaction with the binder matrix than original HMX, owing to the stability of NC on the outer layer.     

Template‐Confined Dewetting Process to Surface Nanopatterns: Fabrication,Structural Tunability,and Structure‐Related Properties

Metallic surface nanopatterns are prepared by a template‐confined dewetting process with multiple structural controllabilities. The morphology of the building blocks is homogeneous throughout the surface nanopatterns, as the dewetting process proceeds separately in each bowl. The features of the building units in the surface patterns are highly dependent on the annealing temperature. Importantly, the size and composition of the nanoparticles in the surface nanopatterns can be pre‐calculated and designed by manipulating the thickness of the evaporated metallic films. The heating temperature and composition of the building units influence the surface‐enhanced Raman scattering (SERS) and plasmonic properties, thus tuning the localized surface plasmon resonance peaks over a broad range (from visible to near infrared). The introduction of silver in the gold surface nanopatterns enhances the SERS performance dramatically. This work not only provides a powerful route to fabricate surface nanopatterns, but also supplies a platform to study the mechanism of the complicated dewetting processes of metals.