Electrodeposition and characterization of thermoelectric Bi<Subscript>2</Subscript>Se<Subscript>3</Subscript> thin films

Bi₂Se₃ thin films were electrochemically deposited on Ti and indium tin oxide-coated glass substrates, respectively, at room temperature, using Bi(NO₃)₃·5H₂O and SeO₂ as starting materials in diluted HNO₃ solution. A conventional three-electrode cell was used with a platinum sheet as a counter electrode, and a saturated calomel electrode was used as a reference electrode. The films were annealed in argon atmosphere. The influence of cold isostatic pressing before annealing on the microstructure and thermoelectric properties of the films was investigated. X-ray diffraction analysis indicates that the film grown on the indium tin oxide-coated glass substrate is pure rhombohedral Bi₂Se₃, and the film grown on the Ti substrate consists of both rhombohedral and orthorhombic Bi₂Se₃.     

Study of two-section composite chain of beads under vertical vibration

We investigated the dynamic properties of a two-section composite chain of beads under vertical vibration.By analyzing the chain’s motion,including phase-shift,mean dilation,center-of-mass displacement,and energy,we found that with different bead arrangements,the chain behaved in different ways.We believe that interaction existing at the interface between bead sections provides the underlying cause.This interaction causes different energy in different arrangements,which leads to different dynamic characteristics.     

复杂工况下连轧过程数值仿真系统研究

针对板、管、棒材连轧过程中出现的工艺制度难以确定、实验研究理论性不强等问题,以非线性有限元为内核,通过机型选择、系统仿真、工艺决策等措施,提出了确定最佳工艺制度的理论和方法.     

Preparation and performance of dye-sensitized solar cells based on ZnO-modified TiO<Subscript>2</Subscript> electrodes

The ZnO-modified TiO₂ electrode was prepared by adding Zn(CH₃COO)₂·2H₂O to the TiO₂ colloid during the sol-gel production process, and was used in dye-sensitized solar cells (DSCs). The open circuit voltage (V _OC) and fill factor (ff) of the cells were improved significantly. The performances of the ZnO-modified TiO₂ electrode such as dark current, transient photocurrent, impedance, absorption spectra, and flat band potential (V _fb) were investigated. It is found that the interface charge recombination impedance increases and V _fb shifts about 200 mV toward the cathodic potential. The effect mechanism of ZnO modification on the performance of DSCs may be that ZnO occupies the surface states of the TiO₂ film.     

基于C~#+SQL SERVER的网站通用注册模块的实现方法

登录注册页几乎是各个正规网站的访问起始页,这是出于网站安全考虑,也是各公司企业为方便管理众多客户所必需。本文以C#+SQL Server为基础设计了一个通用的注册模块,此模块可方便实现在页间传递参数或数据,具有较高实用性。     

分层介质中原子电四极辐射速率的计算

利用平面分层介质中电磁场Green函数的解析形式,求解位于复杂分层介质结构中的原子电四极自发辐射速率.考虑一特例,结果表明与特殊介质结构中由电磁场模式求解的电四极子衰减速率相同.     

Euler’s beta integral in Pietro Mengoli’s works

Beta integrals for several non-integer values of the exponents were calculated by Leonhard Euler in 1730, when he was trying to find the general term for the factorial function by means of an algebraic expression. Nevertheless, 70 years before, Pietro Mengoli (1626–1686) had computed such integrals for natural and half-integer exponents in his Geometriae Speciosae Elementa (1659) and Circolo(1672) and displayed the results in triangular tables. In particular, his new arithmetic–algebraic method allowed him to compute the quadrature of the circle. The aim of this article is to show how Mengoli calculated the values of these integrals as well as how he analysed the relation between these values and the exponents inside the integrals. This analysis provides new insights into Mengoli’s view of his algorithmic computation of quadratures.     

Atomic packing and short-to-medium range order evolution of Zr-Pd metallic glass

A larger-scale Zr₇₀Pd₃₀ alloy system has been simulated using molecular dynamics (MD) to investigate structure evolution in Zr₇₀Pd₃₀ metallic glass. The simulated pair distribution function of Zr₇₀Pd₃₀ metallic glass agrees well with the experimental results. Voronoi polyhedron analysis indicates that the icosahedra are not randomly distributed in space, but form characteristic intercrossed icosahedral clusters with medium-range order. Intercrossed icosahedral clusters are the dominant local configurations in Zr₇₀Pd₃₀ metallic glass and probably cause the quasicrystalline phase discovered in Zr₇₀Pd₃₀ metallic glass.     

Surface pollen assemblages of human-disturbed vegetation and their relationship with vegetation and climate in Northeast China

Pollen assemblages of 53 surface pollen samples from farmlands and wastelands in Northeast China were analyzed. Tree pollen percentages were usually higher than 30%, with Pinus (26.9%), Quercus (0.9%), Betula (0.9%) and Populus (0.7%) as the major types, and herb pollen percentages were usually higher than 50%, with weedy Poaceae (8.7%), Chenopodiaceae (7.1%), Artemisia (1.9%) and Compositae (3.5%) as the major taxa. Thus, the pollen assemblages were consistent with the regional vegetation compositions. However, there were differences in pollen assemblages among regions, especially among different geomorphological units. For example, in the mountains, there were more types of tree pollen and higher total percentages (average 42%) than in other areas, while cereal pollen percentages were lowest (11.2%). In the hills and high plains, herbs made up more than 60% of the pollens, with cereals (average 53.6%) the dominant type. In the low plains, pollen types were similar to those in the hills and high plains, but total pollen concentrations and the proportion of Concentricystes were much higher, while cereal pollen percentages were slightly lower (average 41.6%). Pollen assemblages in different land use types also differed. For example, in farmland, cereal pollen percentages were more than 40% and Chenopodiaceae was usually less than 2.5%, while in wasteland, weedy Poaceae was usually less than 10% and Chenopodiaceae was usually higher than 25%. Total pollen concentrations in farmland (average 3909 grains/g) were much lower than in wasteland (average 15074 grains/g). Redundancy analysis revealed that pollen assemblages were significantly negatively correlated with mean annual temperature (-0.73) and July mean temperature (-0.81) and significantly positively correlated with mean annual precipitation (0.48), indicating that pollen assemblages in the artificial or human-disturbed vegetation reflect regional climate well. Comparison of pollen assemblages in different areas of northern China showed that pollen concentrations reflect the intensities of human impact to some degree. For example, pollen concentrations decrease as human impacts increase in intensity. The cereal pollen proportions in farmland differed by area. In Northeast China, cereal pollen proportions were distinctly higher than in most other areas of northern China, suggesting differences in planting habits and climate.