多孔活性自燃金属的光谱辐射特性研究

多孔活性金属材料因为内部存在大量的孔隙，大大地增加了与空气的接触面积，使得其在空气中的燃烧较为猛烈，燃烧温度迅速上升。其燃烧过程属于固体燃烧的范畴，较为复杂。以镁为例，通过建立燃烧模型，来研究多孔活性金属的光谱辐射特性。首先，建立氧气总消耗量与活性金属剩余质量的关系，研究氧气在活性金属孔隙内的扩散浓度关系，通过求解活性金属热平衡方程得到活性金属燃烧过程中温度与时间的关系式，进而得到活性金属的峰值光谱辐射强度表达式；然后，将模型计算的仿真结果与红外热像仪测得的实验结果对比，结果表明，模型的计算结果与实验结果相一致，误差在了10%以内；最后，通过建立的燃烧模型来研究活性金属燃烧规律以及其光谱辐射特性，解决了高空、高速下的活性金属光谱辐射强度难以实验获得的问题，大大减小了实验成本与时间。分别对比不同时间活性金属箔片在1～3，3～5以及8～12 μm波段下的辐射强度，得出活性金属燃烧时的辐射强度主要集中在3～5 μm波段的结论。研究结果表明：自燃金属最大燃烧温度随高度的增加逐渐下降，随气流速度的增加先增加后减小，在速度为30 m·s-1时，温度达到最大；自燃金属的光谱辐射强度在2～6 μm波段达到最大。该模型也可以用来研究其他活性金属的燃烧特性。     

Applying the combined integral method to one-dimensional ablation

In this paper the combined integral method is applied to a simple one-dimensional ablation problem. One of the drawbacks of heat balance integral methods is how to choose the approximating function. It is common to use a polynomial form but even then it is not clear what the power of the highest order term should be. Previous studies have determined exponents either from exact solutions or from expansions valid over short time scales; neither approach is satisfactory nor very accurate for larger times. We combine the heat balance and refined integral methods to determine this exponent as part of the solution process, and conclude that it is in fact time-dependent in the ablation stage. From comparing the approximate solutions with numerical and exact analytical solutions whenever possible, we show that this new method greatly improves the accuracy on standard methods, without overcomplicating the method.     

Magnetic suspectibilities of liquid gold alloys

Abstract

The temperature dependences of the magnetic susceptibilities of liquid Au-Zn and Au-Cd alloys have been measured. Curves of the susceptibilities of these alloys for all concentrations show rather a big deviation from the linearly interpolated ones. With the increase of temperature, these curves approach the interpolated curves. This fact might be related to the change of clustering in the liquid state, which approaches a random mixture with the increase in temperature.     

Abnormal resistance–temperature characteristic of the melting Bi nanowires

There are no reports about the electronic transport behavior of the melting metal nanostructures because the morphology of nanostructures cannot be kept under the melting condition. Here, the electronic properties of the melting Bi nanowires are investigated using the pore confinement of anodic aluminum oxide template. The results indicate that with the increase of temperature the resistance of Bi nanowires has a transition from the positive temperature coefficient of resistance before fusion to the negative one after fusion. Moreover, as the temperature gradually increases, the resistance of the melting Bi nanowires rapidly decreases at first, and then tardily decreases. This research provides fundamental and valuable information for exploring and designing the new electronic devices under the high temperature.     

A Comparative Study of Electron Heat Transport in a Stochastic and a Non‐Stochastic Magnetic Field

We studied the electron heat transport across a non‐local stochastic magnetic field and a non‐local non‐stochastic magnetic field in tokamak plasmas. Analytical results and numerical simulation results were compared with conditions of a stochastic and a non‐stochastic magnetic field respectively in this article. Parameter of stochasticity in perturbed magnetic field was found not tobe a key factor in influencing effective radial heat conductivity in radial direction of tokomak when Chirikov parameter is close to one (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Infinitely many singular interactions on noncompact manifolds

We show that the ground state energy is bounded from below when there are infinitely many attractive delta function potentials placed in arbitrary locations, while all being separated at least by a minimum distance, on two dimensional non-compact manifold. To facilitate the reading of the paper, we first present the arguments in the setting of Cartan–Hadamard manifolds and then subsequently discuss the general case. For this purpose, we employ the heat kernel techniques as well as some comparison theorems of Riemannian geometry, thus generalizing the arguments in the flat case following the approach presented in Albeverio et al. (2004).     

Swelling Ratios and Rates of Sulfonation of Solvent Modified Copolymers of Styrene Cross-Linked with Pure m-and Pure p-Divinylbenzene

Solvent-modified (toluene) copolymers have been prepared from styrene cross-linked with commercial divinylbenzene, m-divinylbenzene, and p-divinylbenzene at divinyl monomer contents of 16 mole % and 32 mole % at F_M = 0.50. The resultant copolymers have been characterized by swelling-ratio determinations and rates of sulfonation at 60 and 80°C. The solvent-modified 16 mole % cross-linked copolymers sulfonated at rates slightly greater than those characterizing the 8 mole % cross-linked copolymers prepared in the absence of diluent. The order of decreasing sulfonation rates for both the conventional 8 mole % cross-linked systems and for the solvent-modified 16 mole % cross-linked copolymers is commercial divinylbenzene/styrene, p-divinylbenzene/styrene, m-divinylbenzene styrene. The 32 mole % cross-linked systems exhibit a different order of decreasing sulfonation rates: commercial divinylbenzene/styrene, m-divinylbenzene/styrene, p-divinylbenzene/styrene. The swelling ratios of the 32 mole % solvent-modified copolymers were comparable to those of the conventional 8 mole % cross-linked systems.     

Mutation scanning analysis of genetic variation within and among Echinococcus species: Implications and future prospects

Adult tapeworms of the genus Echinococcus (family Taeniidae) occur in the small intestines of carnivorous definitive hosts and are transmitted to particular intermediate mammalian hosts, in which they develop as fluid‐filled larvae (cysts) in internal organs (usually lung and liver), causing the disease echinococcosis. Echinococcus species are of major medical importance and also cause losses to the meat and livestock industries, mainly due to the condemnation of infected offal. Decisions regarding the treatment and control of echinococcosis rely on the accurate identification of species and population variants (strains). Conventional, phenetic methods for specific identification have some significant limitations. Despite advances in the development of molecular tools, there has been limited application of mutation scanning methods to species of Echinococcus. Here, we briefly review key genetic markers used for the identification of Echinococcus species and techniques for the analysis of genetic variation within and among populations, and the diagnosis of echinococcosis. We also discuss the benefits of utilizing mutation scanning approaches to elucidate the population genetics and epidemiology of Echinococcus species. These benefits are likely to become more evident following the complete characterization of the genomes of E. granulosus and E. multilocularis.