On the arithmetical complexity of Sturmian words

Using the geometric dual technique by Berstel and Pocchiola, we give a uniform O(n³)$O\left(n^3\right)$ upper bound for the arithmetical complexity of a Sturmian word. We also give explicit expressions for the arithmetical complexity of Sturmian words of slope between 1/3 and 2/3 (in particular, of the Fibonacci word). In this case, the difference between the genuine arithmetical complexity function and our upper bound is bounded, and ultimately 2-periodic. In fact, our formula is valid not only for Sturmian words but for rotation words from a wider class.     

一种面向FPGA的指/对数函数求值算法

CORDIC算法常用于高效地实现多种超越函数求值,但算法的通用性使其无法针对具体函数进行优化。提出一种统一的指数/对数函数迭代求值算法LnE,实现方式与CORDIC算法类似,每次迭代同样只需进行移位、加法和简单的判断操作,拥有线性收敛速度,但LnE算法具备更多优势：只需x、y两条通路;每次迭代均进行加法操作,不需根据迭代系数[di]选择加法/减法,控制简单;不需进行扩展因子补偿;不需重复某些迭代以保证收敛。因此LnE算法的迭代次数和每次迭代的开销均小于CORDIC算法,相对于CORDIC算法可节省1/3以上的面积开销。     

步进电机控制系统的设计

系统由单片机产生数字脉冲信号,通过ULN2003驱动芯片控制电机的运行。由于脉冲信号的频率决定电机的转动速度,所以要改变转速就需要改变脉冲频率。系统采用定时中断的方法改变脉冲频率,而按键次数主要控制外部中断用以改变存储区中的速度值,步进电机的输出脉冲频率就发生相应的改变,最终达到改变转速的效果。     

结合Rotation Forest和MultiBoost的SVM集成方法

针对如何提高集成学习的性能,提出一种结合Rotation Forest和Multil3oost的集成学习方法—利用Rotation Forest中旋转变换的思想对原始数据集进行变换,旨在增加分类器间的差异度;利用Mu1tiI3oost在变换后的数据集上训练基分类器,旨在提高基分类器的准确度。最后用简单的多数投票法融合各基分类器的决策结果,将其作为集成分类器的输出。为了验证该方法的有效性,在公共数据集UCI上进行了实验,结果显示,该方法可获得较高的分类精度。     

发动机挺柱转动及其影响因素的试验研究

本文分析了影响发动机挺柱转动的诸因素,并在凸轮挺柱磨损试验机上,用正交试验方法试验分析了影响的四种主要因素,估算出它们对挺柱转速影响的显著程度。     

Effect of rotation and thermal relaxation on Rayleigh waves in piezothermoelastic half space

The present paper represents an analysis of Rayleigh surface waves in a homogeneous, transversely isotropic, generalized piezothermoelastic half-space rotating with uniform angular velocity about normal to its boundary and subjected to stress free, electrically shorted/charge free and thermally insulated/isothermal boundary conditions. The secular equations for stress free, generalized piezothermoelastic half-space in closed form and isolated mathematical conditions are derived. The characteristics of surface waves propagating in generalized piezothermoelastic solid half-space and their dependence upon various geometric and physical parameters have been investigated. Finally, in order to illustrate and compare the theoretical results, numerical solution of various secular equations and other relevant relations are derived for cadmium selenide (6 mm) class material by adopting functional iteration scheme after employing Descartes’ algorithm to compute the characteristic roots of coupled differential equation system. The corresponding simulated results of various physical quantities such as phase velocity, attenuation, specific loss, frequency shifts and electromechanical coupling have been presented graphically for rotation and non-rotation cases. The study will be useful in design and construction of gyroscope, rotation sensors, temperature sensors and other pyro/piezoelectric SAW devices.     

混合动力挖掘机回转系统计算及仿真分析

通过混合动力挖掘机与传统挖掘机回转系统的对比,分析回转系统运动特性及各个回转过程,给出回转系统转动惯量,启、制动力矩及回转阻力的计算方法和流程,在此基础上,通过AMEsim软件搭建传统挖掘机液压马达回转系统及混合动力挖掘机电机回转系统的系统模型,并给出液压马达回转系统和电机回转系统的控制策略,通过实例计算和模型仿真得到...     

基于微处理器的智能化旋转机械状态监测与故障诊断系统

介绍了以准１６位徽处理器为核心的智能化旋转机械状态监测与故障诊断系统的工作原理及硬件与软件设计。系统由信号测量、数据采集、数据分析组成，能实现对旋转机械的在线监测、报警、转子振动分析和故障的模糊诊断。     

随机相位噪声对成像的影响及其改善方法

从雷达成像的原理出发,分析了方位向随机相位误差对点目标成像的影响,提出了通过对线性调频信号模糊图进行旋转,矩阵奇异值分解来减弱随机相位噪声影响的方法。仿真结果表明,该方法能有效地减弱随机相位对成像噪声的影响。     

环形井群激发的渗流场之复分析

本文采用复势叠加的方法,得到了环形井群的复势通式。运用该通式,解析了一系列井群的势场和速度场,并推导出了相应的产能公式。分析发现该通式形式简洁,含义明确,变化灵活,具有很强的通用性。