FIR digital filter-based ZCDPLL for carrier recovery

The objective of this work is to analyse the performance of the newly proposed two-tap FIR digital filter-based first-order zero-crossing digital phase-locked loop (ZCDPLL) in the absence or presence of additive white Gaussian noise (AWGN). The introduction of the two-tap FIR digital filter widens the lock range of a ZCDPLL and improves the loop’s operation in the presence of AWGN. The FIR digital filter tap coefficients affect the loop convergence behaviour and appropriate selection of those gains should be taken into consideration. The new proposed loop has wider locking range and faster acquisition time and reduces the phase error variations in the presence of noise.     

快速成形中STL格式文件的分割及其连续成形

为了避免巨型ＳＴＬ格式文件的读入错误和手工粘接带来的误差,研究了沿垂直于Ｚ向将巨型ＳＴＬ格式文件分割成多个ＳＴＬ格式文件,连续依次成形的方法,提出了分割面切割的轮廓环分解为三角形的算法。     

(1-x)Pb(Ni1/3 Nb2/3)O3-xPbTiO3陶瓷的合成及其电滞回线

采用两步法在850℃合成了(1-x)Pb(Ni1／3Nb2／3)O3-xPbTiO3(x=0．28～0．42)陶瓷,粉末均为单一钙钛矿相。扫描电子显微镜观察和介电性能检测表明：所研究的陶瓷的最佳烧结温度为1200℃。对1200C烧结的0．64Pb(Ni1/3Nb2/3)O3-0．36PbTiO3陶瓷的铁电性能进行了详细地研究,发现组成在准同型相界的陶瓷铁电性得到增强．而这种铁电性增强正是由组分及结构和准同型相界的本质共同决定的。     

The Future of Information Modelling and the End of Theory: Less is Limited,More is Different

The computational design strategist Cynthia Ottchen , who was previously Head of Research and Innovation at OMA, offers insights into the future of building information modelling (BIM). Now in the Petabyte Age of the data deluge, she argues that in our adoption of BIM we have to surpass mere data collection and technical optimisation and open up new ways of thinking with the creative use of ‘soft data’. Copyright © 2009 John Wiley & Sons, Ltd.     

压电材料中缺陷偶极子特性的研究进展

压电材料通过受主掺杂或烧结挥发等可以形成缺陷偶极子, 缺陷偶极子对材料的性能有显著的影响。本文综述了压电材料中缺陷偶极子的产生及其在外场下的响应机理, 同时, 从缺陷偶极子运动的角度分析了压电材料中老化、电滞回线异常及电致形状记忆效应等现象的起源, 简要分析了偶极子弛豫现象, 并对未来发展高可靠性压电驱动器的研究作了展望。     

Analysis of an automobile assembly line as a network of closed loops working in both,stationary and transitory regimes

In this work a real automobile assembly line and the correspondent preassembly lines have been analyzed as a network of closed loops of machines decoupled by intermediate buffers. This work deals with some important aspects, which have still not been investigated in earlier literature, such as: machines processing pallets, which are not related to each other and depend on an external variable in a network with closed loops of machines and intermediate buffers, machines working at different cycle times in a network of closed loops of machines and intermediate buffers, machines working in both, stationary and transitory regime and the relationships between the cycle times of the machines in the stationary working regime in order to guarantee the production rate of the system. Finally how the transient results can be used to improve the performance of the system under certain working conditions is discussed.     

用于布里渊分布式光纤传感的光学锁频系统

报道了一种用于布里渊分布式光纤传感器(DOFS)的高稳定光学锁频系统。一台波长为1550nm的半导体分布反馈(DFB)激光器作为主激光器用于光纤传感探测,另一台同样的激光器作为从激光器,采用光学锁相的方法将其与主激光器进行频率跟踪,使主激光器与从激光器频率差恒定为11GHz。利用该光源搭建基于自发布里渊的分布式光纤传感系统(BOTDR),可以有效地实现宽带移频,使得探测解调频率降低到百兆赫兹量级,大大降低了探测的噪声,并且降低了BOTDR系统成本。结果表明,采用此光源方案的频率波动范围为±1MHz。     

矢量跟踪算法快速重跟性能分析

当卫星导航信号受到一段时间干扰或遮蔽时,信号载噪比下降,传统跟踪环路失锁。信号恢复时,针对传统跟踪环路不能及时重新跟踪问题,应用矢量跟踪算法,进行跟踪。分析了在真实GPS数据加上仿真噪声之后矢量/频率锁定环路（VDFLL）的性能以及与传统环路进行对比,试验证明矢量跟踪具有快速重跟性能。     

Dynamics of charge‐pump phase‐locked loops

Certain problems in the existing treatment of the stability of charge‐pump phase‐locked loops are identified and addressed in this work. New results concerning the instability, stability, and asymptotic stability of charge‐pump phase‐locked loops are obtained by means of Lyapunov's direct and indirect methods. Closer consideration of the local dynamics provides further insight into the system's patterns of behavior. In particular, the influence of circuit parameters on the nature of the steady‐state orbits is investigated. Copyright © 2012 John Wiley & Sons, Ltd.     

Electromagnetic and Dynamic Mechanical Properties of Extruded Cobalt Ferrite-Polypropylene Composites

Cobalt ferrites of 0–45 wt% were incorporated in polypropylene by the extrusion technique. With increasing magnetic loading, the magnetizations were linearly increased according to the rule of mixture and the electrical permittivity was also proportional to the loading as described by Wagner's equation. The magnetic permeability may be increased but was reduced to minimal at high frequencies because of the substantial coercive field of cobalt ferrites after the extrusion. Without considerable adsorption of polymer matrix on magnetic fillers, the storage and loss modulus from 30 to 180°C of polypropylene were decreased by cobalt ferrites additions.