战术通信网中按需路由协议的仿真研究

战术通信网是现代信息战中产生的一个重要的战场信息传输网络,其中路由协议的选择对于网络能否成功构建至关重要。在此研究了战术通信网按需路由协议中的AODV协议和DSR协议,对两种协议进行详细的分析比较,并通过OPNET仿真工具对AODV与DSR协议在不同场景下的路由开销、网络延迟和丢包率进行仿真分析,指出了两种协议各自的优势和特点,为两种路由协议在无线传播环境下的应用提供了有效的依据。     

Using a new protocol to enhance path reliability and realize load balancing in mobile ad hoc networks

In this paper we introduce a novel end-to-end approach for achieving the dual goal of enhanced reliability under path failures, and multi-path load balancing in mobile ad hoc networks (MANETs). These goals are achieved by fully exploiting the presence of multiple paths in mobile ad hoc networks in order to jointly attack the problems of frequent route failures and load balancing. More specifically, we built a disjoint-path identification mechanism for maintaining multiple routes between two endpoints on top of the Stream Control Transmission Protocol (SCTP), and the Dynamic Source Routing (DSR) protocol. A number of additional modifications are incorporated to the SCTP protocol in order to allow its smooth operation. The proposed approach differs from previously related work since it consists of an entirely end-to-end scheme built on top of a transport layer protocol. We provide both analytical and simulation results that prove the efficiency of our approach over a wide range of mobility scenarios.     

Ad Hoc中的常用路由算法分析

在传统的移动无线Internet接入方式中，通常是以宽带有线接入网为支撑。无线用户只通过一跳(不需要在无线网中多次转接)就可以接入固定网络。在很多应用场合，如个人区域网、家域网、军事应用、抢险救灾等，无线网络没有固定的基础设施作支撑，移动用户的信息需要通过移动用户之间的多次中转才能到达目的用户，这种网络通常称为分布式或无中心式(Ad hoc)网络。本文首先介绍了Ad Hoc网络。然后介绍了目前运用于Ad Hoc网络中的几种路由算法，并指出其优缺点。     

短波Ad Hoc路由协议仿真与性能分析

为找到一种适合短波Ad hoc网络使用的路由协议,通过OPNET仿真软件对短波信道进行建模,在该模型的基础上对无线Ad Hoc常用的3种路由协议:优化链路状态路由(Optimized Link State Routing,OLSR)、反应式路由中的动态源路由(Dynamic Source Routing,DSR)和按需距离矢量(Ad hoc On Demand Distance Vector,AODV)进行仿真分析。仿真结果表明,OLSR路由协议网络时延最小、吞吐量最高和数据丢失率最低,其整体性能优于AODV及DSR路由协议,更适合于短波信道,但是OLSR路由协议也存在着开销高的不足,下一步可以针对降低路由开销进行研究。     

Aging resistance of asphalt binders through the use of zinc diethyldithiocarbamate

Abstract

Aging can significantly reduce the durability of binders used in asphalt pavements and can consequently impose long-term maintenance cost to the owners. Antioxidants are additives that can be used to hinder oxidation and hardening of petroleum asphalt binders. In this study, the effect of zinc diethyldithiocarbamate (ZnDEC) as an antioxidant on chemical and rheological features of the binder were evaluated and monitored during laboratory aging process. The results indicated that not only ZnDEC can retard the aging process, but it also improves the low- and mid-temperatures cracking resistance without negatively affecting the rutting performance of the binder.     

高模量沥青流变性能的试验研究

选用两种高模量添加剂ZQ-2及ECB,分别对三个不同掺量下(5%、7%、10.5%)的两种高模量沥青进行动态剪切流变试验(DSR)及低温梁弯曲试验(BBR),分析不同掺量下它们的高低温性能。研究表明:随着掺量的上升,掺加ZQ-2的高模量沥青高温性能随之提高,低温性能下降;而掺加ECB的高模量沥青高低温性能随着掺量的上升变化趋势并不明显。最后建议河北省耐久性高模量项目工程(承赤高速试验段)最适宜的添加剂掺量。     

Synthesis and evaluation of high-temperature properties of butylated graphene oxide composite incorporated SBS (C4H9-GO/SBS)-modified asphalt

Graphene nanoparticles (GNPs) added styrene-butadiene-styrene (SBS)-modified asphalt suffers from serious compatibility and agglomeration problems. To tackle these problems, in this study, graphene oxide (GO) was mixed with bromobutane to synthesize butylated graphene oxide (C₄H₉-GO) composite, which was in turn compounded with SBS for the preparation of C₄H₉-GO/SBS-modified asphalt. C₄H₉-GO/SBS-1.0-modified asphalt exhibited the best performance in terms of 11.4% increased softening point, 19.3% increased ductility, and 10.2% reduction in penetration as compared to 5% SBS-modified asphalt. Dynamic shear rheometer and multistress creep recovery tests showed that at 1.0% C₄H₉-GO contents, C₄H₉-GO/SBS composite-modified asphalt exhibited the best high-temperature performance and low stress sensitivity. Microscopic characterization of C₄H₉-GO via Fourier transform infrared spectroscopy, X-ray diffraction, and Raman spectroscopy revealed successful bonding between  C₄H₉ and GO, increasing interlayer spacing in GO. Atomic force microscopy and scanning electron microscopy analysis showed the superior elasticity of C₄H₉-GO than GNPs. Differential scanning calorimetry analysis indicated that C₄H₉-GO sheets can be stabilized by SBS through π–π stacking with the polystyrene chains. This study awarded to the preparation of novel C₄H₉-GO/SBS-modified asphalt with superior mechanical property can be deemed of potential value and applications in construction and highway industries. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48231.     

汉语语音识别的抗噪性前端算法及性能分析

讨论了欧洲电信标准委员会ETSI提出的分布式语音识别系统的抗噪前端特征提取算法,该算法融合多种抗噪技术。结合汉语语音的特点,进行了汉语语音识别整体框架下的算法实现,并进行了实验和分析,典型噪声环境下的识别结果证明,相对于基线MFCC特征提取算法,稳健性有较大提高。     

Multipath Source Self Repair Routing Algorithm for Mobile Ad Hoc Networks

A multipath source self repair routing (MSSRR) algorithm for mobile ad hoc networks is proposed.By using multiple paths which can be repaired by themselves to transmit packets alternately, the network‘s load is balanced, the link state in the network can be checked in time, the number of the times the route discovery mechanism starts is decreased. If only one route which will be broken can be used to transmit the packets, the route discovery mechanism is restarted. The algorithm is implemented on the basis of dynamic source routing (DSR). The effect of MSSRR on lifetime of the access from the source to the destination and the overhead is discussed. Compared with the performance of DSR, it can be seen that the algorithm can improve the performance of the network obviously and the overhead almost does not increase if the average hop count is larger.     

浅析增强型EDGE关键技术

EDGE（Enhanced Dataratefor GS MEvolution）是一种基于GSM／GPRS网络的数据增强型移动通信技术．通常又被人们称为2．75G技术。本文介绍了在伴随着多载波．QAM调制．DSR技术、新型时隙结构等各种关键技术的应用．EDGE的发展与演进一一增强型EDGE技术。阐明了增强型EDGE技术在演进路线中的地位．分析了其对传统EDGE技术的改进与3G系统互补,共存的特点。