高动态GPS信号模拟器的研究与硬件设计

高动态GPS卫星信号模拟器根据载体的动态环境,精确产生载体收到的GPS卫星信号。文中针对机载GPS接收机的高动态环境建立了多通道GPS信号模拟器的数学模型,并用systemview软件验证了系统设计的可行性。并提出了GPS信号产生器的硬件实现方法。     

动态激光通信系统开环捕获技术

主要解决载舰与地面间及载舰与舰间激光通信系统开环捕获的问题.对捕获系统的组成及工作原理进行了详细论证,着重分析了捕获概率和捕获时间的决定因素.通过实例在某海域完成动态激光通信系统试验,捕获概率优于98%,捕获时间小于20s,验证了本系统能够满足动态激光通信系统的开环捕获要求.     

A scheme of access service recommendation for the Social Internet of Things

The rapid increase in the complexity and the extent of personalization of services in the Internet of Things (IoT) has led to a greater demand for frequent collaboration among heterogeneous devices. Moreover, with the inseparable relations between human and devices, the paradigm of Social IoT (SIoT) is gaining popularity in recent years. How to effectively facilitate the access to quality services and credible devices in large‐scale networks via defining, establishing, and managing social architectures among things has become a critical issue. In this paper, a scheme of access service recommendation for the SIoT is presented with the understanding of inherent constraints and factors that influence the security and stability of IoT networks. In which, timeliness properties are considered in each transaction for dynamic performance enhancements. With the benefits of promoting service discovery and composition, social relationships among things are introduced in the proposed scheme. An energy‐aware mechanism is also utilized as a restrictive factor in trustworthiness evaluation. Finally, the recommendation is based not only on the past performance but also on the social relationship and the energy status of nodes. Simulation experiments demonstrate the effectiveness and benefits of our scheme from three aspects including rating accuracy, dynamic behavior, and network stability. Copyright © 2015 John Wiley & Sons, Ltd.     

基于小波变换的动态阈值法语音信号净化

语音信号实时去噪净化处理是语音通信系统的关键技术。传统的小波阈值去噪方法由于阈值的单一性,在去除噪声的同时,造成语音信号损伤。针对这一问题,提出了一种基于小波变换的动态阈值法语音信号净化方法。能根据噪声和信号的变化而动态调节阈值;采用改进的阈值函数对小波系数缓变地压缩,仿真实验结果表明,能有效去除信号中的噪声和较好保留语音细节。     

SECM微纳米定位建模及控制器设计

为适应扫描电化学显微镜(SECM)常规应用中100nm左右的微定位精度需求,同时降低其微定位控制器的成本,在分析SECM压电工作台运动定位数学模型的基础上,结合SECM实际应用中的特点,将压电工作台数学模型进行了合理的简化,并在此基础上设计了算法简单且易于实现的开环微定位控制器。以CHI900B型扫描电化学显微镜的三维压电工作台为实验对象进行建模和控制器设计,实验结果表明,压电工作台运动定位平均跟踪误差和最大跟踪误差分别为0.093、0.115μm,误差约0.1μm,可满足SECM常规应用中的微定位精度需求。建模过程和控制器设计简单易行且无须额外的微定位传感器,适于SECM的常规应用。     

基于搜索数据率的弹道导弹跟踪制导雷达最优搜索时序

利用引导信息进行小窗口空域搜索是弹道导弹防御跟踪制导雷达极其重要的搜索方式,弹道导弹的高速运动对该方式下的搜索时序提出了巨大挑战.本文提出了一种基于搜索数据率确定雷达最优搜索时序的方法.首先依据累积发现概率最大化准则建立了搜索波位的静态最优数据率模型;然后依据静态搜索数据率的计算结果,采用编排的方式确定了波位的静态最优搜索时序;在此基础上采用照射波位与目标运动相匹配的方法得到波位的动态最优搜索时序;最后给出了仿真结果,验证了本文方法在弹道目标高速运动条件下的有效性.     

电容投切开关动态响应分析与实验

电容器投切开关的动态响应时间是动态无功补偿装置的一个重要性能指标,对补偿的效果有很大影响。文中对基于固态继电器的电容投切开关的动态响应时间进行了理论分析,并通过实验证明其正确性,为无功补偿装置的选型提供参考,有实际应用意义。     

电子束曝光机工作台吊装结构动态特性的研究

正在研制的激光定位吊装结构工作台系统是电子束曝光机的主要组成部分。本文概述了工作台吊装结构的特点,用有限元法建立了吊装结构的三维实体力学模型,在理论上对其进行了动态特性分析与计算,并用锤击法进行了测试。分析与实验表明,工作台吊装结构抗冲击能力很强,能够满足电子束曝光机高精度和高速度的要求。     

字符串动态匹配算法在地层对比中的应用

提出改进的最大类间方差法通过计算有序序列最大类间方差、最小类内方差以实现测井曲线分层,弥补最大类间方差法只能将序列分成2类的缺陷。数值形式表示的曲线不便于对比的描述,提出将数值曲线序列提取特征并转换成离散的、相对抽象的字符串序列的方法,并以具有可以得到全局最优解特点的动态规划法为理论基础进行曲线对比。使用胜利油田地质科学院提供的真实地质数据,验证利用字符串进行动态匹配进行曲线对比在地层对比中的应用,实验结果表明,算法对地层缺失、地层尖灭和地层逆序的情况均适用,且具备简化特征提取、对比效率高的特点。     

Modifying asphalt emulsion with different types of polymers for surface treatment applications

Asphalt emulsion produced from local asphalt 60/70 (Suez Co.) was modified with different types of polymers such as epoxy resin, latex styrene butadiene styrene (SBS), poly vinyl acetate (PVA), and with a mixture of two or more types of above mentioned polymers to produce a modified asphalt emulsion with high performance. This paper describes the method and technique for preparing asphalt emulsion as well as the tests, and evaluates several aspects concerning the prepared emulsion such as performance of evaporation residues, fuel and acid resistance, rheological properties, and durability. The results obtained revealed that all the modified asphalt emulsions gave better performance as compared with unmodified emulsion. Asphalt emulsion modified with a mixture of epoxy resin, latex SBR, and PVA showed the best road performance in terms of fuel and acid resistance. It was observed that the weight loss for unmodified binder, residue after evaporation of water, after immersion in kerosene for 120 min is 90% of its initial weight, while the binder improved with a mixture of SBS latex, epoxy resin, and PVA showed a weight loss of ?16% and 9% of its initial weight. Also, the admixture gives high acid resistance (weight loss ～ 9%) after immersing in 5% HCl. The dynamic viscosity test showed that asphalt emulsion modified with a mixture of SBS latex, epoxy resin, and PVA has the highest viscosity value which is a promising indication about the validity of its use for pavement in different applications.