目标散射矩阵的特征值理论和雷达天线的最优极化

在本文中，研究了非对称的散射矩阵，发展了其特征值理论。然后，研究了雷达天线的最优极化问题。在文中还指出了国外文献中的某些假设或结论是不正确的     

加热、冷却下变物性梯度功能材料板瞬态热应力

用非线性有限元法分析由ZnO2和Ti-6Al-4V组成的变物性梯度功能材料板在加热、冷却过程中的瞬态热应力问题,检验方法的正确性,给出不同力学边界条件下该材料板的瞬态热应力场分布,并与常物性时的结果进行比较。结果表明,考虑变物性比常物性时的最大拉应力减少26％,最大压应力减少23．2％;在冷却初瞬时,陶瓷侧出现很大拉应力;此外,材料组分的分布形状系数M的变化和力学边界条件对该材料板的加热、冷却瞬态热应力场分布的影响显著。此结果为该材料的设计、制备提供了准确的理论计算依据。     

微电子元件在冲击载荷下的失效分析及数值模拟

焊球界面层裂是微电子封装器件的主要失效模式之一。针对微电子封装器件的界面层失效问题,首先利用焊球剪切实验,得出在剪切速度增加的情况下,焊球失效形式由脆性断裂转变为韧性断裂。基于实验结果,利用有限元程序LS-DYNA,采用内聚力模型的方法,模拟在高速冲击下焊球的裂纹扩展情况,得到与实验结果相似的仿真结果。研究表明:内聚力模型法应用于微电子封装材料的界面层失效分析,可准确模拟微电子封装器件的界面层开裂问题,对进一步研究整个器件在生产、制造、测试及使用过程中界面层裂的产生与扩展奠定基础。     

ADHESION STRENGTH OF COATING SUBSTRATE AND SURFACE MORPHOLOGY OF PRETREATMENT

Premature failure of coated tool often results from a poor adhesion of coating-substrate and shortens the lifetime of the tool. The results of increasing the adhesion strength of thin film coatings on cutting tool inserts by pretreating the inserts with sandblasting technique to obtain a desirable surface morphology of the inserts are presented. A geometric model representing the ideal surface morphology is established to enhance the nucleation density and adhesion strength of coating-substrate. Thin film coating experiment is conducted on the substrates of four different sample groups. Indentation and wear tests are performed on coated inserts to evaluate the effect of sandblasting on the adhesion strength of the coatings. A theoretical analysis is provided on the formation and growth of atom clusters in terms of the contact angle and the thermodynamic barrier of a substrate to predict thin film nucleation.     

TD-SCDMA系统密集市区的规划研究

本文分析了密集市区TD-SCDMA系统的传播环境及话务特点,从目前密集市区TD-SCDMA网络存在的问题入手,在规划的角度对密集市区覆盖和容量需求进行了分析,给出了规划建议。     

A facile co-gelation route to synthesize FeCo/carbon nanocomposites and their application as magnetically separable adsorber

A new kind of magnetic porous FeCo/carbon nanocomposites was successfully synthesized by using a facile co-gelation sol-gel route. The sol-gel process of this route started from an ethanol solution containing teraethylorthosilicate (TEOS), furfuryl alcohol (FA), and metal nitrates. With the evaporation of solvent, the weak acidity produced from hydrolysis of metal nitrates simultaneously catalyzed the polymerization of FA and the hydrolysis of TEOS, which led to the inorganic/organic hybrid xerogel, accompanying metal salts spontaneously captured in the xerogel. The composites obtained have high surface areas, pore volumes and strong magnetic strengths, which make them exhibit excellent performance of adsorption for bulk dyes and easily separated from solution by external field after adsorption. Compared to the previous methods, this route is very simple and operable for the preparation of magnetic porous carbon composites. Such facile co-gelation route also provides a common path to the synthesis of nanoscale metal or alloy embedded in the porous carbon materials.     

Structural characterisation of acid- and alkali-soluble polysaccharides in the fruiting body of Dictyophora indusiata and their immunomodulatory activities

The acid- and alkali-soluble polysaccharides (DIPs I and II) were extracted from the fruiting body of Dictyophora indusiata in this work. DIP I comprised of Glc (glucose), Fru (fructose) and Man (mannose), whereas DIP II was of Glc and Fru. Glc was the dominant monosaccharide in both DIPs with relatively molar percentage of >60%, which constructed the backbone of polysaccharide chain. The analysis of the glycosidic linkages indicated that Glc occurred as Glc 1 → 6 in DIP II. The immunological assays showed that both DIPs I and II had a noticeable effect on the hemolysis antibody level in the tested dosage range. However, DIP I could improve the weight of thymus organ and phagocytosis of monocyte. DIP II could restore delayed-type hypersensitivity reaction to dinitrofluorobenzene (DNFB), improving the activity of natural killer cells and the proliferation of splenocytes at high dose.     

SUPPRESSION OF A CAVITATION NEAR THE ORIFICE OF A RELIEF VALVE

The aim of this study is to suppress a cavitation near the orifice of a relief valve by changing the shape of a poppet. An experimental flow visualization technique and a numerical cavitating flow simulation, using a RNG k-ε turbulence model and a cavitation model, are employed to achieve the purpose. In the flow visualization, the cavitation phenomenon near the orifice of a relief valve is observed using a transparent test valve body model and a camera. On the other hand, a three dimensional cavitating flow simulation is conducted to predict the cavitation near the orifice of a relief valve. Six types of poppets are designed by changing the shape of a traditional poppet shape, which is expected to influence the cavitating flow in an orifice. In addition, the cavitation noise of a relief valve is measured and the noise spectrum is analyzed. In conclusion, the cavitation intensity and the cavitation noise are reduced for an optimal poppet geometry obtained in the present study.     

STUDY ON RECIPROCATING SEALS FOR A LARGER DIAMETER AXIAL PISTON

Sealing performance of the reciprocating seals on a larger diameter (100 mm in diameter ) axial piston is theoretically investigated. Based on the characteristics of the clearance flow between the seal and the piston, reasonable boundary conditions for Navier-Stokes equations are determined and the equations are modified, so that the final equations can describe the real flow state of the clearance flow. Through combining the final equations with finite element method, the pressure distributions within the clearance field during the reciprocating motion of the piston and the leakage rate with the pressure are studied. The deflections of the seal which affect sealing performance are calculated as well. Sealing performance of piston seals using oil as the working liquid is compared with using water. It is concluded that the seal using water as the working liquid is under dry friction, which cannot be dealt with the theory of fluid mechanics. The seal structure is only acceptable using oil as the working l     

Synthesis and characterization of terbium doped barium cerates as a proton conducting SOFC electrolyte

A novel proton conductor, BaCe_0.95Tb_0.05O_3−a (BCTb) perovskite was synthesized via the EDTA-citrate acid complexing method, followed by high temperature calcination. The properties of the powders were characterized by thermo gravimetric-differential thermal analysis (TG-DTA), X-ray diffraction (XRD), Scanning electron microscopy (SEM) and the conductivity measurement using the 4-probe method. In order to obtain the pure perovskite structure, the calcination temperature was elevated at 1000 °C or greater. The electrical conductivities of the BCTb perovskite mainly result from protons and are 6.51 × 10⁻³−2.0 × 10⁻² S cm⁻¹ in the temperature range of 600-850 °C with the activation energy of 41.95 kJ mol⁻¹. A Ni-BCTb∣BCTb∣LSCF(La_0.6Sr_0.4Co_0.2Fe_0.8O_3-α)-BCTb fuel cell was subsequently fabricated via a co-pressing/co-sintering method, followed by slurry-coating of the cathode. With 50 mL min⁻¹ pure hydrogen as fuel and the ambient air as oxidant, the maximum output of the fuel cell has reached to 753 mW cm⁻² at 700 °C. The results demonstrate that BCTb perovskite may be a promising electrolyte for the proton-conducting solid oxide fuel cells (PC-SOFCs) after its chemical stability is improved significantly.