用新乌龟坐标变换研究动态Kerr黑洞的Hawking辐射

本文用一种新的乌龟坐标变换和改进的Damour-Ruffini方法研究了动态Kerr黑洞的Hawking辐射,得到了随时间和纬度角而变化的局域温度和具有准黑体谱形式的Hawking辐射谱.其结果与采用通常的乌龟坐标变换所得结果有所不同,而通常的乌龟坐标变换在量纲上存在一定的问题,本文的结果也许更为合理. 关键词： Hawking辐射 动态Kerr黑洞 改进的Damour-Ruffini方法 新乌龟坐标变换     

基于改进注意力机制的实体关系抽取方法

实体关系抽取是知识库构建中至关重要的一个环节.在众多的实体关系抽取方法中,远程监督结合神经网络模型的方法在准确率等性能上是比较令人满意的,但远程监督获取的标注语料中往往存在大量的噪声数据,给实体关系抽取模型的训练带来了很大的影响.本文提出一种基于改进注意力机制的卷积神经网络实体关系抽取模型.该模型针对包含同一实体对的句子集合,从中尽可能地找出所有体现该实体对关系的正实例,构建组合句子向量,抛弃可能的噪声句子,从而最大程度地降低噪声句子的影响又能充分利用正实例的语义信息.实验证明,本文提出的关系抽取模型在准确率上优于对比的关系抽取模型.     

高性能跑车发动机用PCB的生产工艺研究

汽车发动机用PCB要求较高的可靠性,高性能跑车发动机用PCB的可靠性要求更是十分苛刻。世界各大车用PCB制造商即使使用高成本的高Tg材料,也未必能生产出达到高性能跑车发动机要求的PCB。采用较低成本的中Tg材料,结合改进压合工艺,降低PCB材料的应力;并改善电镀铜工艺,降低电镀铜的应力。这样独特的生产工艺,使PCB在Z轴的膨胀大大降低,可使PCB的可靠性得到大幅提高。     

基于改进双边滤波的多尺度运动目标检测方法

提出一种基于改进双边滤波的运动多尺度目标检测方法,以提高对弱小目标的检测能力.首先对视频或序列红外图像进行改进双边滤波处理,提高目标的对比度,同时抑制背景的边缘噪声及随机噪声.然后对目标进行三维匹配滤波,获得若干组速度匹配叠加强度图像.最后,在这些图像中进行基于NNLoG(归一化负LoG算子)的多尺度目标检测,得到序列图像或视频段的最佳匹配速度及增强后的图像.可最终计算出目标在序列图像或视频中的运动方程.通过大量的实验及对比实验可知,改进双边滤波、三维匹配滤波及NNLoG算子综合处理效果都较好,可有效检测序列图像或视频中的目标.     

滑动离散傅里叶算法输出稳定性研究

受数字系统有限字长的影响,滑动离散傅里叶变换(滑动DFT)算法的频率单元存在输出不稳定的缺点。利用改进Goertzel算法的递归单元对滑动DFT算法的频率单元改造后,不仅可以直接计算起始频谱值,而且滑动DFT算法可以每隔N个输出值就对频率单元清零,并能提供准确的新谱值,保证了滑动DFT算法的频率单元可以长时间连续不断的处理输入数据,而不会出现输出不稳定现象。这种方法在连续地、实时地进行时频谱分析中具有重要的意义。     

支持协作多点技术的网络架构的研究

协作多点(coordinated multi-point,CoMP)技术因能有效改善小区边缘用户性能,提高系统吞吐量,引起了业界的广泛关注和研究。CoMP的研究要基于一定的网络架构,目前已有的中心式和分布式网络架构存在回程容量大、CoMP时延高、复杂度高等问题。本文提出了改进型分布式网络架构,在传统分布式网络架构的基础上增加了集中控制的逻辑实体,能有效简化CoMP流程,减少CoMP时延以及实现复杂度。     

Coupled flow and heat transfer of power-law nanofluids on non-isothermal rough rotary disk subjected to magnetic field

We study the coupled flow and heat transfer of power-law nanofluids on a non-isothermal rough rotating disk subjected to a magnetic field. The problem is formulated in terms of specified curvilinear orthogonal coordinate system. An improved BVP4C algorithm is proposed, and numerical solutions are obtained. The influence of volume fraction, types and shapes of nanoparticles, magnetic field and power-law index on the flow, and heat transfer behavior are discussed. The obtained results show that the power-law exponents (PLE), nanoparticle volume fraction (NVF), and magnetic field inclination angle (MFIA) have almost no effects on velocities in the wave surface direction, but have small or significant effects on the azimuth direction. The NVF has remarkable influences on local Nusselt number (LNN) and friction coefficients (FC) in the radial direction and the azimuth direction (AD). The LNN increases with NVF increasing while FC in AD decreases. The types of nanoparticles, magnetic field strength, and inclination have small effects on LNN, but they have remarkable influences on the friction coefficients with positively correlated heat transfer rate, while the inclination is negatively correlated with heat transfer rate. The size of the nanoparticle shape factor is positively correlated with LNN.     

An improved interpolating element-free Galerkin method with a nonsingular weight function for two-dimensional potential problems

In this paper, an improved interpolating moving least-square (IIMLS) method is presented. The shape function of the IIMLS method satisfies the property of the Kronecker δ function. The weight function used in the IIMLS method is nonsingular. Then the IIMLS method can overcome the difficulties caused by the singularity of the weight function in the IMLS method. The number of unknown coefficients in the trial function of the IIMLS method is less than that of the moving least-square (MLS) approximation. Then by combining the IIMLS method with the Galerkin weak form of the potential problem, the improved interpolating element-free Galerkin (IIEFG) method for two-dimensional potential problems is presented. Compared with the conventional element-free Galerkin (EFG) method, the IIEFG method can directly use the essential boundary conditions. Then the IIEFG method has higher accuracy. For demonstration, three numerical examples are solved using the IIEFG method.     

离散控制系统采样信号数学描述方法的讨论

计算机控制系统的广泛应用，使得离散系统的建模、分析以及设计在经典控制理论的教学中处于愈来愈重要的位置。本文针对学生在学习采样信号的数学表述方法时存在的疑问和困惑，指出现有的采样信号的数学表述方法本身，有其欠妥之处，容易造成学生的误解。论文同时给出了改进的采样信号的数学表述方法。教学实践表明：基于改进的采样信号表述方法授课，理论上更为严谨，学生易于理解、接受。     

PD-Based Optimal ADRC with Improved Linear Extended State Observer

Taking dead-zone nonlinearlity and external disturbances into account, an active disturbance rejection optimal controller based on a proportional-derivative (PD) control law is proposed by connecting the proportional-integral-derivative (PID) control, the active disturbance rejection control (ADRC) and particle swarm optimization (PSO), with the purpose of providing an efficient and practical technology, and improving the dynamic and steady-state control performances. Firstly, in order to eliminate the negative effects of the dead-zone, a class of 2-order typical single-input single-out system model is established after compensating the dead-zone. Following that, PD control law is introduced to replace the state error feedback control law in ADRC to simplify the control design. By analyzing the characteristics of the traditional linear extended state observer, an improved linear extended state observer is designed, with the purpose of improving the estimation performance of disturbances. Moreover, employing PSO with a designed objective function to optimize parameters of controller to improve control performance. Finally, ten comparative experiments are carried out to verify the effectiveness and superiority of the proposed controller.