Effect of heat-treatment on the surface properties of gallium phosphide nanosolids by Raman spectroscopy

Raman spectra of gallium phosphide （GAP） nanosolids （unheated and heat-treated at 598 and 723 K, respectively） were investigated. It was observed that both the longitudinal optical mode （LO） and the transverse optical mode （TO） displayed an asymmetry on the low-wavenumber side. The scattering bands were fitted to a sum of four Lorentzians which were assigned to the LO mode, surface phonon mode, TO mode, and a combination of Ga-O-P symmetric bending and sum band formed from the X-point TA ＋ LA phonons, respectively. Analysis of the characteristic of surface phonon mode revealed that the surface phonon peak of the GaP nanosolids could be confirmed. In the infrared spectrum of the GaP nanoparticles, we observed the bands on account of symmetric stretching and bending of PO2, as well as stretching of Ga-O The Raman scattering intensity arising from the Ga-O-P linkages increased as increasing the heat-treatment temperature.     

Variational principle of combined energy—Mechanics of laminated structures

The conventional approaches for stress analysis of composite laminates have encountered discontinuity problems. In this paper, the C¹ continuity of displacements in the in-plane directions and C⁰ continuity of displacement along the thickness direction are discussed. Also, the global continuity of transverse stresses and local continuity of in-plane stresses are examined. Then, the formulations of stress analysis in both differential equation form and variational functional form are presented.     

Improved durability of Si/B/N/C random inorganic networks

The inherent high temperature durability as well as the hardness of random inorganic networks composed of Si, B, N and C, can be raised through the incorporation of rigid structural elements (e.g. borazine rings) as well as through an increase of the carbon content. This has been shown by comparison of the high temperature durabilities and micromechanical properties of newly synthesized Si/B/N/C ceramics derived from different acyclic and cyclic single source precursors. Crosslinking of these specially designed monomers with methylamine provides highly homogeneous preceramic polymers, in which the predetermined structural features of the molecular precursors are embedded. Subsequent pyrolysis and calcination up to 1500 °C converts the polymers into all-inorganic amorphous silicon boron carbonitrides. Depending on the constitution of the precursors, the as-obtained materials exhibit a combination of a high carbon content together with borazine rings embedded into the covalent network. Comparing the high temperature stability, hardness and stiffness of the synthesized ceramics, the best performance is achieved when carbon rich borazine derivatives are employed as single source precursors. Thus, the high temperature durability can be raised up to at least 2000 °C, and, at the same time, the microhardness and elastic modulus is maximized up to 14.5 and 127 GPa, respectively. The new materials have been characterized by IR spectroscopy, elemental analysis, XRD, SEM, DTA/TG, and by nanoindentation.     

Fluid flow and heat transfer in an optical fiber coating process

The optical fiber coating process, using a die and applicator system, was numerically simulated. The coupled partial differential equations, governing the fluid flow and heat transfer, were solved on a transformed, non-uniform, staggered grid. A finite volume method, with conjugate heat transfer, boundary-fitted grid, and variable transport properties, was employed. The pressure was calculated using a SIMPLE-based algorithm. An isothermal case was first modeled, where the effect of the Reynolds number (Re) was studied for different geometries. Different coating fluids were considered. A conjugate boundary condition was employed at the fiber–fluid interface for the non-isothermal flow. A free surface boundary condition was used at the fiber entry into the coating fluid. The meniscus was prescribed on the basis of prior experimental work. Regardless of fiber speed, a circulating flow was observed in the applicator. High shear rates at the dynamic contact point suggest that air can be entrained with a fast moving fiber. It was also found that pressures at the coating fluid inlet did not play a major role, for typical fiber speeds, whereas the thermal conditions that affect the properties of the fluid, such as viscosity, made a significant impact on both the flow and the thermal field. This work could be used to determine the parameters that are critical for improving the quality of the coating, particularly its uniformity, and the production rate.     

可中断负荷参与输电阻塞管理的模型与算法

在市场环境下，输电阻塞严重威胁系统安全，并加剧了市场力滥用行为。可中断负荷作为一种电力资源可有效缓解阻塞。文中建立了一个可中断负荷参与电力批发市场竞价的阻塞管理模型。该模型是一个2层优化模型：外层优化潮流模型可确定节点电价，并进行电能调度；内层优化模型旨在选取有效消除阻塞的可中断负荷。在模型求解时，针对出现的非线性互补问题(NCP)，通过NCP函数将其转化为一组非线性代数方程，然后用改进的Levenberg-Marquardt算法求解。最后以一个修改的IEEE 30节点系统验证了该模型和算法的有效性。     

Effect of Magnetic Interaction on Thermally Activated Reversal in a Magnet With a Distribution of Energy Barriers

The time dependence of magnetization is usually expressed as M(t)=M₀-SInt [see Proc. Phys. Soc. 62, 562 (1949)] for magnetic viscosity experiments. Considering magnetic interaction during the thermal activation process, a form as M(t)=M₀-SIn(t+t₀) is deduced. The dipolar interaction and exchange coupling in a magnet can lead to positive and nonpositive t₀, respectively. In the experiments of the magnetic viscosity for nanocrystalline Pr₂Fe₁₄B ribbons, the existence of positive t₀ is confirmed.     

无线ILC系统测控信号延时效应补偿方法

针对通过无线信道进行测控信号传输的远程迭代学习控制( ILC)系统,研究信号传输延时对控制系统性能的影响.分析了测控信号延时情况下ILC系统的收敛性问题,通过引入预控制向量,提出了ILC系统信道延时效应补偿的向量更新方法.数值仿真结果表明了所提方法的有效性.     

基于综合特征的车辆检测识别系统

随着信息技术和智能交通的迅速发展,自动的车辆检测识别成为不可或缺的技术。由于基于单一特征和单车辆的识别并不能满足实际中的应用要求,因此提出了多特征多车辆的检测识别算法,利用基于灰度对称,形状特征和光流强度特征的提取,通过基本的图像处理算法,最终由综合特征为基础得出车辆的识别检测结果,利用基于VC＋＋6．0的软件系统开发出车辆检测识别系统,通过实验对照,由单一特征和综合特征的检测不同结果获得实验数据,通过检测算法将视频序列图像中的车辆信息自动识别提取出来并加以标记。实验结果表明系统能够适应多变的车型和环境信息,通过识别结果准确性的分析,得出结论：针对不同的车型有较好的鲁棒性,能够满足实际智能交通控制平台的构建的基本要求。     

跳数加权DV-Hop定位算法

针对DV-Hop定位算法中距离估计误差对定位结果的影响,提出了一种信标节点优选方案和跳数加权DV-Hop定位算法。首先通过设定跳数阈值,保留跳数较少的信标节点,然后剔除近似在一条直线上的信标节点,完成信标节点优选,避免未知节点无法定位的情形。此外,利用Friis模型推导出距离估计误差与信号传播跳数之间的映射关系,采用传播跳数作为加权因子对定位结果进行了修正。仿真结果表明该算法降低了距离估计误差对定位精度的影响,提高了定位精度。