Microwave heating synthesis of HgS and PbS nanocrystals in ethanol solvent

A novel route was developed to prepare PbS and HgS nanocrystals in ethanol solvent in the presence of sodium hydroxide by microwave heating method. PbS and HgS nanocrystals were obtained with an average size of approximately 10 and 6 nm, respectively. In the reaction, mercury acetate and lead acetate were used as mercury and lead source; sulfur powder was employed as chalcogenide source. The products were characterized by X-ray powder analysis (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and UV–Vis absorption spectroscopy. The probable mechanism was presented.     

Analytical solution for the axisymmetric plane strain electroelastic dynamics of a special non-homogeneous piezoelectric hollow cylinder

By virtue of the introduction of a dependent variable and the separation of variables technique, the axisymmetric plane strain electroelastic dynamic problem of a special non-homogeneous piezoelectric hollow cylinder is transformed to a Volterra integral equation of the second kind about a function with respect to time, which can be solved successfully by means of the interpolation method. Then the solutions of displacements, stresses, electric displacements and electric potential are obtained. The present method is suitable for a piezoelectric hollow cylinder with an arbitrary thickness subjected to arbitrary mechanical and electrical loads. Numerical results are finally presented.     

Generalized eigenvectors and fractionalization of offset DFTs and DCTs

The offset discrete Fourier transform (DFT) is a discrete transform with kernel exp[-j2/spl pi/(m-a)(n-b)/N]. It is more generalized and flexible than the original DFT and has very close relations with the discrete cosine transform (DCT) of type 4 (DCT-IV), DCT-VIII, discrete sine transform (DST)-IV, DST-VIII, and discrete Hartley transform (DHT)-IV. In this paper, we derive the eigenvectors/eigenvalues of the offset DFT, especially for the case where a+b is an integer. By convolution theorem, we can derive the close form eigenvector sets of the offset DFT when a+b is an integer. We also show the general form of the eigenvectors in this case. Then, we use the eigenvectors/eigenvalues of the offset DFT to derive the eigenvectors/eigenvalues of the DCT-IV, DCT-VIII, DST-IV, DST-VIII, and DHT-IV. After the eigenvectors/eigenvalues are derived, we can use the eigenvectors-decomposition method to derive the fractional operations of the offset DFT, DCT-IV, DCT-VIII, DST-IV, DST-VIII, and DHT-IV. These fractional operations are more flexible than the original ones and can be used for filter design, data compression, encryption, and watermarking, etc.     

基于欧玛技术的大学英语考试总评成绩计算方法

以基于欧玛技术的阅卷系统为例,介绍了用Excel实现大学英语分类成绩的接口及合并计算总评成绩的基本方法与步骤.     

Nonlinear Stress-Strain Relationship of Soil Reinforced with Flexible Geofibers

A nonlinear stress-strain relationship of soil reinforced with flexible geofibers under static loading is derived based on a nonlinear elastic stress-strain relationship of soil and a linear elastic stress-strain relationship of geofibers in the paper. This investigation includes the following aspects: First, the homogenization technique is introduced to find the volume average stress tensor and volume average strain tensor and further an elastic incremental stress-strain relation is introduced to describe deviatoric shear stress-axial strain relationship of equivalent homogeneous geofiber-reinforced soil. Second, the relation of geofiber numbers, content, mechanical behavior, distribution, and geometrical features to shear modulus of geofiber-reinforced soil is expressed and assessed by employing an elastic energy method. Third, the deviatoric shear stress and axial strain curves of geofiber-reinforced soil are calibrated by laboratory testing data of geofiber reinforced soil samples. Finally, the theoretical computational curves of geofiber reinforced soil are compared with the curves calibrated by testing data of geofiber reinforced soil. The model prediction has a good agreement with experimental results.     

Distributed Rule-Regulated Spectrum Sharing

Dynamic spectrum access is a promising technique to use spectrum efficiently. Without being restricted to any prefixed spectrum bands, nodes choose operating spectrum on-demand. Such flexibility, however, makes efficient and fair spectrum access in large-scale networks a great challenge. Prior work in this area focused on explicit coordination where nodes communicate with peers to modify local spectrum allocation, and may heavily stress the communication resource. In this paper, we introduce a distributed spectrum management architecture where nodes share spectrum resource fairly by making independent actions following spectrum rules. We present five spectrum rules to regulate node behavior and maximize system fairness and spectrum utilization, and analyze the associated complexity and overhead. We show analytically and experimentally that the proposed rule-based approach achieves similar performance with the explicit coordination approach, while significantly reducing communication cost.     

基于PTFE的PCB的多层层压方法

介绍了采用不同材料类型的粘结膜、半固化片、所需设备和粘结材料,用于生产低到高层数的PTFE多层板的情况。     

精对苯二甲酸反应器桨叶断裂分析与修复

为了保证进口精对苯二甲酸装置氧化反应器中钛制搅拌器的正常工作，对钛制搅拌器桨叶在运行中断裂脱落的原因进行了分析，并叙述了桨叶修理的方法和要求。经修理后的桨叶投入生产使用，达到了预期的目标。     

导向剂加入方式对Y型沸石合成的影响

以煤系高岭土为原料,采用液态补硅手段调节体系SiO2/Al2O3、导向剂两步加入法合成了Y型沸石.考察了导向剂不同加入方式对Y型沸石合成的影响.采用合理的导向剂两步加入法,特别是通过控制导向剂第二步加入的时间,可明显缩短Y型沸石的晶化时间,并有效地减少P型沸石的生成.     

CO毒化AB5型合金分形特征研究

研究了三种贮氢合金 L a Ni5、L a Ni4 .7Al0 .3、Ml Ni4 .5Al0 .5被 10 0× 10 - 6 CO毒化后的分形特征 ,求出这三种合金在含 10 0× 10 - 6 CO的氢中循环 ,分维分别为 0 .2 5 4 7、0 .170 9、0 .0 72 5。可以较好的解释合金被毒化的宏观现象。