Effect of the Liquid-Phase Characteristic on the Microstructures and Dielectric Properties of Donor- (Niobium) and Acceptor- (Magnesium) Doped Barium Titanate

Changes in the microstructure and dielectric properties with the variation of the donor/acceptor ratio in BaTiO₃ ceramics were investigated. In donor-rich specimens, a liquid that appeared during sintering did not penetrate into grain boundaries. However, in the acceptor-rich specimens, the grains were separated by a liquid film during sintering. The much higher mobility of the liquid film than that of the grain boundaries was suggested to cause extensive grain growth in acceptor-rich BaTiO₃. The macroscopic homogenization of dopants because of grain growth in acceptor-rich specimens resulted in changes in the dielectric properties.     

The Berlekamp-Massey Algorithm revisited

We propose a slight modification of the Berlekamp-Massey Algorithm for obtaining the minimal polynomial of a given linearly recurrent sequence. Such a modification enables to explain it in a simpler way and to adapt it to lazy evaluation. partially supported by the Galois Theory and Explicit Methods in Arithmetic Project HPRN-CT-2000-00114 partially supported by the European Union funded project RAAG CT-2001-00271     

控制W9Cr3Mo4V低倍碳化物剥落的工艺改进

针对W9Cr3M04V轧制成品材低倍碳化物剥落的形成原因分析，得出一次碳化物颗粒粗大、在1／4D至中心区域聚集是导致低倍热酸浸试验碳化物剥落的主因；由此进行冶炼过程中注速（锭形）、浇注温度选择对比工艺试验，得出在原有冶炼＋轧制的工艺基础上选用2．2t锭、降低浇注温度（1489℃）能有效改善一次碳化物颗粒大小和聚集程度，进而有效降低低倍碳化物剥落倾向。     

Heavy arsenic doping of silicon grown by atmospheric pressure selective epitaxial chemical vapor deposition

Selective epitaxial Si with a high arsenic concentration of 2.2×10¹⁹ atoms/cm³ was deposited at a high growth rate of 3.3 nm/min under atmospheric pressure. It was confirmed that this method had excellent selectivity and produced films having good crystalline quality, abrupt dopant profiles at the interfaces, and smooth surfaces. The growth mechanism is discussed in terms of the relationship between the effects of arsenic surface segregation and etching by hydrogen chloride.     

La3+掺杂对纳米TiO2微观结构及光催化性能的影响

以钛酸丁酯和氯化镧为原料,采用溶胶-凝胶法制备了La3+掺杂TiO2纳米粉体,讨论了不同掺杂浓度、不同热处理温度的样品催化降解刚果红染料实验中的光催化活性,并通过X射线衍射(XRD)、透射电镜(TEM)分析了La3+掺杂TiO2样品的相组成、晶胞参数和晶粒大小对光催化活性的影响.结果表明:La3+掺杂能够显著提高TiO2粒子的光催化活性,最佳掺杂浓度为100∶3 0,最佳热处理温度为600℃;La3+掺杂的TiO2的相组成是影响光催化活性的决定性因素;晶格膨胀程度及晶粒大小对光催化活性的影响,主要是在相组成相同或相近时才体现得比较明显.     

Effect of functionalization and boron and nitrogen substitution on some properties of carbon nanotubes

Molecular orbital calculations of the ionization potential of single wall carbon nanotubes having donor NH₂ and acceptor NO₂ groups bonded to the side walls and ends and boron and nitrogen substituted for carbon show substantial increases in ionization potential compared to carbon nanotubes with no functional groups and no carbon substitutions. The presence of a carbon vacancy on the side wall also causes a substantial increase in the ionization potential. The effect of tube length on the ionization energy is also calculated. The calculations also suggest that at appropriate levels of boron and nitrogen doping the armchair carbon nanotubes could be high temperature organic ferromagnetic materials.     

Formation Kinetics of Unsaturated (Ti, W)C Solid Solution

ＦｏｒｍａｔｉｏｎＫｉｎｅｔｉｃｓｏｆＵｎｓａｔｕｒａｔｅｄ（Ｔｉ，Ｗ）ＣＳｏｌｉｄＳｏｌｕｔｉｏｎＬｉｎＣｈｅｎ’ｇｕａｎｇ，ＤｅｎｇＦｅｎｇｘｉａｎｇ，ＨｅＣｏｎｇｘｕｎａｎｄＧａｏＺｈａｏｚｕ（林晨光）（邓凤翔）（贺从训）（高兆祖）（Ｇｅｎｅｒ...     

Recrystallisation of amorphous natural brannerite through annealing: The effect of radiation damage on the chemical durability of brannerite

An amorphous natural brannerite sample was chosen to study the annealing of the radiation damage through thermal recrystallisation, and subsequently to evaluate the effect of radiation damage on its aqueous durability. Microstructural characterisation of the natural brannerite revealed minor alteration along the rim of the crystal and within cracks. The formation of UO₂ particles and soluble Pb–Ca-rich aluminosilicate glass is responsible for the higher U and Pb releases from the recrystallised brannerite. In general, natural brannerite has been shown to be resistant to dissolution over geological time, therefore minor brannerite inclusions in ceramic formulations for immobilisation of actinide-rich radioactive wastes should not have a detrimental effect on the long-term chemical durability of the wasteforms.     

An efficient algorithm for characteristic tracking on two-dimensional triangular meshes

Tracking characteristics on unstructured meshes is an important part of many numerical methods in computational fluid mechanics. In this paper, we propose an efficient algorithm for characteristic tracking on two-dimensional unstructured triangular meshes. Numerical experiments, including an example for applying this algorithm with the Eulerian-Lagrangian localized adjoint method (ELLAM) to solve a convection-dominated convection-diffusion problem, are presented to demonstrate the efficiency of this algorithm.