正交频分复用分组传输系统中载波频偏和信道的联合估计

针对传统接收机将载波频偏和信道状态独立估计带来性能损失的缺点,提出了一种载波频偏和信道的联合估计算法.该算法由两个独立的载波频偏和信道估计单元通过迭代的方法实现,其中信道估计单元利用载波频偏估计单元提供的载波频偏估计信息和最大似然方法估计信道状态信息,而载波频偏估计单元则利用信道估计单元提供的信道估计信息和最大似然方法估计载波频偏.随着载波频偏估计单元与信道估计单元间估计信息的不断交换,载波频偏和信道估计的精度得到逐步提高.由于该算法避免了复杂的多维搜索算法,因此具有较低的计算复杂度.此外,在算法迭代过程中考虑了信道估计噪声的影响,进一步提高了估计的精度.仿真结果表明,当符号能量噪声比大于18dB时,可以获得接近理想同步的误码性能.     

关于表达式求值的算法研究与实现

栈是计算机领域中重要的数据结构.容器是C++标准库定义的一种数据结构、队列,栈等数据结构都能用不同类型的容器实现.计算机进行表达式求值的方法很多,主要采用栈和一种容器(如vector类型)来实现在包含+、-、*、/运算符和(、)括号的表达式求值中常用的算法,文中所有表达式都假设是在合法情况下进行求值的,中缀表达式到后缀...     

涟钢RH-MFB试生产钢水质量分析

为充分发挥RH-MFB的精炼功能,了解涟源钢铁公司RH-MFB的精炼效果,对涟钢RH-MFB上的钢水质量进行分析,包括钢中w[C],w[N],wT[O]及显微夹杂分析.结果表明,RH-MFB试生产钢水在中间包内平均增碳量为0.002 2%,出RH后钢液有轻微吸氮现象;RH-MFB精炼后,钢液中大于10 μm的显微夹杂数量明显减少,wT[O]平均值较前期生产也有明显下降;基体为Al2O3的夹杂物是RH精炼过程及中间包钢液中存在的主要夹杂物,其形貌特征各异,在工艺后期多以球状和细小块状存在,此外,还发现有少量铝酸盐或硅铝酸盐加硫化物夹杂.为此,提出了有针对性的改进措施.     

Adaptive fault-tolerant controller design for airbreathing hypersonic vehicle with input saturation

The problem of fault-tolerant control is discussed for the longitudinal model of an airbreathing hypersonic vehicle(AHV) with actuator faults and external disturbances.Firstly,a fault-tolerant control strategy is presented for the longitudinal model of an AHV,which guarantees that velocity and altitude track their reference trajectories at an exponential convergence rate.However,this method needs to know the minimum value of the actuator efficiency factor and the upper bound of the external disturbances,which makes it not easy to implement.Then an improved adaptive fault-tolerant control scheme is proposed,where two adaptive laws are employed to estimate the upper bound of the external disturbances and the minimum value of the actuator efficiency factor,respectively.Secondly,the problem of designing a control scheme with control constraints is further considered,and a new adaptive fault-tolerant control strategy with input saturation is designed to guarantee that velocity and altitude track their reference trajectories.Finally,simulation results are given to show the effectiveness of the proposed methods.     

我国著作财产追续权立法障碍评析

在著作权法修订之际，关于追续权入法的呼声日隆。然而，将追续权纳入中国著作权法，尚需解决其执法障碍，即美术作品转让的信息获取问题和权利主张模式，如果这些障碍不解决，即使入法，也缺乏可操作性。理论上的正当性，也需要考虑到实际操作上的可行性。     

毫米波通信系统中利用随机逼近的波束赋形算法

为了在60 GHz毫米波通信系统中确定收发机最优的窄波束方向使得传输速率最大,提出了一种基于波束码本的自适应波束赋形算法.该算法在室内60 GHz信道的射线跟踪模型基础上建立了离散优化问题,并引入随机逼近的全局优化算法进行求解,首先在窄波束空间中进行随机采样,再利用含噪的信道估计获得样本目标函数的无偏估计量,并据此执行...     

Adaptive set stabilization of the attitude of a rigid spacecraft without angular velocity measurements

The global adaptive set stabilization problem of the attitude of a rigid spacecraft is addressed in this paper. Two different cases are considered. First, by using adaptive backstepping method, the authors design a global adaptive control law for the attitude control system with unknown inertia matrix such that the attitude and the angular velocities can be globally asymptotically stabilized to a set consisting of two equilibria. And then, based on the obtained backstepping adaptive law, the authors consider the case that the angular velocities are not measurable. By introducing an auxiliary state, a semi-global adaptive set stabilization law without angular velocity measurements is also designed. It is rigorously proved that, for the two cases, both of the closed loop systems satisfy the set stability. The effectiveness of the proposed methods is verified by simulation results.     

关于螺线管各分段自感和段间互感的分析

螺线管是由各分段或各单匝线圈串联而成的,某分段或某匝线圈所匝链的磁链是其自感磁链与别的线圈对其总互感磁链之和.其中自感磁链对各匝线圈来说是相等的,与线圈的具体位置无关.而线圈所获取的总的互感磁链则与该线圈的具体位置有关:线圈越靠近管子的中间,获取的互感磁链就越大;越靠向管子的两端,获取的互感磁链就越小.至于自感系数和互感系数则与相应磁链的特点一样.     

Fuzzy Multi-Objective Decision Model of Supplier Selection with Preference Information

1. INTRODUCTIONNowadays supply chain managemellt is a hot topic in acadellila circle and induStrial Practice. Purchasing andsupply managemellt is the key step of supply chain management. The combination of focusing more on coLlaborative relationshipsand increasingly strategic role of purchasing has resulted in a rise in prominence ofstrategies of supply base reduction and relationships management (supplier-buyer relationships management)within the last few years (Lamming 1993, bort and p…     

Systematic Methodology of Integrated Supply Chain Management

Supply chain management (SCM) is a strategy for global competition. Th e characteristics of SCM are integration, systematic and coordination. Using sys tematic, coordination thoughts and integration theory, a new model of enterprise integration based on supply chain management is put forward and an implementing paradigm for systematic methodology of supply chain management is developed.