Electromagnetic energy flow near nanoparticles—I: single spheres

The electromagnetic (EM) energy flow near single spheres is investigated by applying Mie theory. From the patterns of the energy flow, the absorption and the scattering of light can be understood in the microscopic point of view. In the absorption profiles of metallic particles, most absorbed energy is consumed on the surface of the particles, which indicates that the resonance of surface plasmon is different from that of the bulk plasmon. Two mechanisms to enhanced local EM field are also distinguished. One is the surface plasmon resonance, and another one is the intensified energy flow.     

短周期超晶格AlP／GaP能带结构的转变及其带间的光跃迁

介绍了间接跃迁的半导体ＡｌＰ与ＧａＰ形成的超晶格，由于零折叠效应，实现了能带由间接带隙向直接带隙的转变，从而增加了带间的光跃迁几率，并推导了该几率的表达式。     

Total energy decay for the wave equation in exterior domains with a dissipation near infinity

We show that the energy of solutions to the initial boundary value problem for the wave equation in exterior domains with a dissipation which is localized only near infinity tends to zero as the time goes to infinity. We do not make any geometrical condition like star-shapedness on the boundary.     

Existence and nonexistence of curved front solution of a biological equation

This paper deals with the existence of curved front solution of a partial differential equation coming from a mathematical model of stroke. The equation is of reaction-diffusion type in a cylinder of radius R and of diffusion and absorption type outside of the cylinder. We prove the nonexistence of a travelling front when R is small enough and the existence if R is large enough using a recent energy method. We construct the travelling front as the limit in time of a solution with a well-chosen initial condition, in a travelling referential.     

Energy of formation for and liquid binary alloys

We have investigated the free energy of formation for Ag_xIn_1-x and Ag_xSn_1-x liquid binary alloys at temperatures 1173 and 1250 K, respectively. A microscopic theory based on the first order perturbation has been applied. The interionic interaction and a reference liquid are the fundamental components of the theory. The interionic interaction is described by a local pseudopotential. A liquid of hard spheres (HS) of two different effective diametres and charges is used to describe the reference system. The results of the calculations for energy of formation agree very well with the available experimental data. Our calculations also reveal that a simple perturbative approach along with appropriate effective pair potentials can produce nearly quantitative results for the concerned alloys.     

Upper and lower bounds for the energy of bipartite graphs

Using Lagrange's multiplier rule, we find upper and lower bounds of the energy of a bipartite graph G, in terms of the number of vertices, edges and the spectral moment of fourth order. Moreover, the upper bound is attained in a graph G if and only if G is the graph of a symmetric balanced incomplete block design (BIBD). Also, we determine the graphs for which the lower bound is sharp.     

Electron–hole recombination luminescence in LiYF4:U single crystal

Photoluminescence (PL), photostimulated luminescence (PSL), thermally stimulated luminescence (TSL) and electron paramagnetic resonance (EPR) studies were carried out on LiYF₄:U⁴⁺ and pure LiYF₄ crystals. The PL and EPR investigations have identified the presence of Eu³⁺, Tb³⁺ and Gd³⁺ ions in both of these crystals possibly due to their existence in the starting materials. The luminescence observed during afterglow, PSL and TSL revealed that emission occurs at wavelength positions 382, 413, 437 and 544 nm, which are characteristic of Tb³⁺ ions. The present investigations using PSL and TSL in combination with PL studies before and after gamma irradiation have revealed that selective energy transfer to Tb³⁺ ions occurs during electron–hole recombination processes like PSL and TSL. Even though other luminescent ions (U⁴⁺ and Eu³⁺) are present in the system and U⁴⁺/U³⁺ ions are participating in electron capture/release processes, the selective energy transfer results in Tb³⁺ ions acting as luminescence centers.     

低阻抗二极管产生的强流电子束能谱分布的数值模拟

 给出了低阻抗二极管产生的电子束能谱分布及外加磁场对二极管阻抗影响的数值模拟研究结果。结果表明，即使在外加电压恒定的条件下，二极管产生的电子束也具有一定的能谱分布，这说明用二极管电压、电流波形计算脉冲电子束能谱分布是不正确的。另外,外加磁场对低阻抗二极管的阻抗特性具有较大影响，其阻抗随外加磁场的增大而减小。分析认为这是由于外加磁场强度的变化改变了二极管中束电子的运动轨迹。当没有外加磁场或外加磁场较小时，低阻抗二极管产生的电子束发生自箍缩，此时二极管电流是自箍缩饱和顺位流；当外加磁场足够强时，电子束的自箍缩被抑制，二极管电流是没有箍缩时的空间电荷限制电流。束电流小于自箍缩临界电流的二极管其阻抗将不随外加磁场的变化而变化。     

Location and calculation-free node-scheduling schemes in large wireless sensor networks

In wireless sensor networks that consist of a large number of low-power, short-lived, unreliable sensors, one of the main design challenges is to obtain long system lifetime without sacrificing system original performance (sensing coverage and sensing reliability). To solve this problem, one of the potential approaches is to identify redundant nodes at the sensing interface and then assign them an off-duty operation mode that has lower energy consumption than the normal on-duty mode. In our previous work [J. Wireless Commun. Mobile Comput. 3 (2003) 271; Processing of ACM Wireless Sensor Network and Application Workshop 2002, September 2002], we proposed a node-scheduling scheme, which can provide a 100% sensing coverage preservation capability. This, however, requires each node to be aware of its own and its neighbors’ location information. Also, in that scheme, each node has to do accurate geometrical calculation to determine whether to take an off-duty status. In this paper, we propose and study several alternative node-scheduling schemes, which cannot completely preserve the original system coverage, but are nonetheless light-weighted and flexible compared with the previous one. Our simulation results compare these schemes with the previous one and demonstrate their effectiveness.     

Diffusion of 99Tc in granite under aerobic and anoxic conditions

Summary  Vezetéknév