Singular Double Porosity Model

We consider the linear parabolic equation describing the transport of a contaminant in a porous media crossed by a net of infinitely thin fractures. The permeability is very high in the fractures but very low in the porous blocks. We derive the homogenized model corresponding to a net of infinitely thin fractures, by means of the singular measures technique. We assume that these singular measures are supported by hyperplanes of codimension one. We prove in a second step that this homogenized model could be obtained indistinctly either by letting the fracture thickness, in the standard double porosity model, tend to zero, or by homogenizing a model with infinitely thin fractures.     

A new red-emitting phosphor of Eu3+-doped Sr2MgMoxW1−xO6 for solid state lighting

The white light-emitting diode has recently attracted great attention as a promising candidate for next generation lighting. The solid solution of Sr_1.80Eu_0.10Li_0.10MgMo_xW_1?xO₆ was synthesized via high-temperature solid-state reaction and this solid solution is treated as a promising red emitting phosphor for white light-emitting diodes. In our cases, the X-ray diffraction, excitation spectra, emission spectra and decay curves of these solid solutions were measured as a function of the Mo/W ratio to characterize the structural and luminescent properties. The excitation bands of the series of phosphors are consistent well with the region of near ultraviolet light, and the phosphors present better color purity than the commercial phosphor Y₂O₂S:Eu³⁺ in current use. Taking these properties into consideration, this kind of material may find a great potential application as a red phosphor for near-ultraviolet excited white light-emitting diodes.     

传感器和Origin7.0软件在电脑控制韦伯福斯摆的实验研究中应用

研究用电脑控制韦伯福斯摆的实验中,用光电传感器、位移传感器和力传感器测量摆的振动周期和摆幅、角速度等及弹簧的劲度系数,由此来学习一种测量刚体转动惯量的方法。     

Electrostatic double layers in a warm negative ion plasma with nonextensive electrons

The electrostatic double layer (DL) structures are studied in negative ion plasma with nonextensive electrons q-distribution. The extended Korteweg–de Vries (EKdV) equation is derived using a reductive perturbation method. It is found that both fast (compressive) and slow (rarefactive) ion acoustic (IA) DLs can propagate in such type of plasmas. The effects of various plasma physical parameters; such as nonextensivity of electrons, presence of negative ions, temperature of both positive and negative ions and different mass ratios of positive to negative ions on the formation of DL structures are discussed in detail with numerical illustrations.     

Double marginalization and coordination in the supply chain with uncertain supply

This paper explores a generalized supply chain model subject to supply uncertainty after the supplier chooses the production input level. Decentralized systems under wholesale price contracts are investigated, with double marginalization effects shown to lead to supply insufficiencies, in the cases of both deterministic and random demands. We then design coordination contracts for each case and find that an accept-all type of contract is required to coordinate the supply chain with random demand, which is a much more complicated situation than that with deterministic demand. Examples are provided to illustrate the application of our findings to specific industrial domains. Moreover, our coordination mechanisms are shown to be applicable to the multi-supplier situation, which fills the research gap on assembly system coordination with random yield and random demand under a voluntary compliance regime.     

Effect of double stratification on MHD free convection in a micropolar fluid

This paper analyzes the flow and heat and mass transfer characteristics of the free convection on a vertical plate with variable wall temperature and concentration in a doubly stratified micropolar fluid. A uniform magnetic field is applied normal to the plate. The governing non-linear partial differential equations are transformed into a system of coupled non-linear ordinary differential equations using similarity transformations and then solved numerically using the Keller-box method. The numerical results are compared and found to be in good agreement with previously published results as special cases of the present investigation. The non-dimensional velocity, microrotation, temperature and concentration are presented graphically for various values of magnetic parameter, coupling number, thermal and solutal stratification parameters. In addition, the Nusselt number, the Sherwood number, the skin-friction coefficient, and the wall couple stress are shown in a tabular form.     

单点侧向泵浦掺Yb3＋双包层光纤激光器理论研究

 从速率方程出发，建立了单点侧向泵浦掺Yb³⁺双包层光纤激光器的理论模型并进行了数值分析，得到了泵浦光方向分别为正向、反向、双向时,光纤内泵浦光和激光功率的分布特性及输出功率与泵浦点位置的变化关系。结果表明，相对于泵浦光正向或反向传输，当泵浦光双向传输时，光纤中的激光功率分布和输出激光功率受泵浦点的位置影响较小，对于侧向泵浦的双包层光纤激光器是较好的选择。     

Effects of springs on a pendulum electromechanical energy harvester

This paper studies a model of energy harvester that consists of an electromechanical pendulum system subjected to nonlinear springs. The output power is analyzed in terms of the intrinsic parameters of the device leading to optimal parameters for energy harvesting. It is found that in an appropriate range of the springs constant, the power attains higher values as compared to the case without springs. The dynamical behavior of the device shows transition to chaos.