基于粒子群优化算法的二维最大相关法图像分割

二维最大相关法图像分割算法充分利用了图像像素的灰度分布信息和各像素间的空间相关信息,因此算法的抗干扰能力强、图像分割效果好.但该算法的搜索空间大、计算时间长.为解决这一问题,提出了一种基于粒子群优化算法的二维最大相关法.该算法充分利用粒子群优化算法的特点,并对其进行了有益的改进,提高了算法的性能和搜索速度.实验结果证明了该算法的快速性、有效性和稳定性.     

基于强基因模式组织算法的VRPTW研究

提出一种强基因模式组织算法,给出了强基因模式、连续模式以及对称模式的定义,使用节约法提取强基因模式.设计了选择、变异和模式重组算子,同时建立了以运输成本为目标、具有时间窗等约束的车辆路径问题模型.将该算法与改进的遗传算法、改进的差分进化算法和节约法对模型进行仿真实验.结果表明,强基因模式的应用及模式重组算子大大缩小了解的搜索空间,提高了算法的收敛速度和解的精度,其性能优于其他3种算法.     

带有非线性惯性权重和柯西变异的粒子群优化算法

粒子群优化算法是一种新型启发式智能优化算法,它运行速度快,收敛性强,但是容易陷入局部极值.为了克服粒子群算法的早熟收敛现象,提出了一种新的带有非线性惯性权重和柯西变异的粒子群优化算法.首先,对算法中的惯性权值进行改进,增强粒子局部收敛能力;然后,利用柯西变异算子,增加种群多样性.数值实验表明,提出的改进粒子群优化算法具有较快收敛速度,寻优能力强,能有效克服早熟收敛现象.     

基于改进樽海鞘算法的共享单车分布密度优化

针对城市共享单车分布密度优化问题,提出了一种改进樽海鞘算法.首先,将共享单车分布密度优化问题转换成函数优化问题,以等待时间、花费时间、费用及安全代价为评价指标,建立目标函数.其次,引入一维正态云模型和非线性递减控制策略来改进樽海鞘算法中引领者的搜索机制,增强对局部数据的挖掘能力;引入自适应策略来改进原算法跟随者搜索机制,避免算法陷入局部最优值.最后,通过标准测试函数以及共享单车分布密度优化仿真对所提优化算法的有效性进行了验证,结果表明:相比原樽海鞘算法、萤火虫算法及人工蜂群算法,改进的樽海鞘算法具有更好的稳定性和全局搜索能力,能够更好地实现对共享单车分布密度的优化,提升共享单车的区域利用率,对智慧交通的发展有一定的参考价值.     

基于词频信息改进的IG特征选择算法在文本分类中的应用研究

IG算法是一种有效的特征选择算法,在文本分类研究领域中得到了广泛应用。本文针对IG算法的不足,提出了一种基于词频信息的改进方法,分别从类内词频信息、类内词频位置分布、类间词频信息等方面进行了改进。通过实验对改进的算法进行了测试,结果表明,改进的算法相对传统算法更有效。     

最优权动态控制学习机制的多种群遗传算法

遗传算法(GA)的全局搜索能力强,易于操作,但收敛速度慢,易陷入局部极值.为克服上述缺陷,首先对算法初始化方法进行改进,采用海明距离作为聚类划分的相似性度量提出了一种均匀分区多种群初始化方法.该方法以相似性度量为准则划分出不同集合的聚类中心点,然后以偏好随机的方式产生多个不同的种群,避免算法因种群初始个体在解空间分布不够均匀而陷入局部收敛.其次在遗传算法中引入多种群并行机制和学习机制来提高算法的性能,通过对已有研究中两种机制在遗传算法中的作用进行分析,指出各自的优势和不足,分别对两种机制进行改进,提出改进的多种群并行机制与最优权动态控制的学习机制,并从理论角度探讨了改进的两种机制的合理性.最后,将两种机制有机结合起来,充分发挥两种机制的优点,抑制各自的不足之处.仿真实验结果表明,算法中经过改进的两种机制具有良好的沟通能力,结合新的初始化方法,使得算法在收敛速度和精度上都要优于其他几种已有的改进算法.     

微粒群优化算法在基站分布规划中的应用

微粒群优化算法（PSO）是一种具有全局随机优化的智能算法。该算法编程简单,鲁棒性强,并行运算能力强,能以较快的速度收敛至全局最优解。本文在PSO的思想基础上提出了一种改进搜索方向,降低“早熟”概率的方法,即结合遗传算法,引入了爬坡算子。本文并将该改进算法应用于基站分布规划的研究中,实验仿真结果表明,利用该改进算法能提高基站覆盖率,降低经济成本。     

一种基于精英选择和反向学习的分布估计算法

为了提高分布估计算法的性能,提出一种从选择方式和搜索机制出发的改进分布估计算法.首先,借鉴并改进粒子群种群更新策略,在构造优势群体时,引入精英选择策略替换经典的截断选择,提高算法向全局最优解的收敛速度;然后,引入二次反向反射搜索算子,从搜索机制上对分布估计算法进行改进,提高算法的全局搜索能力.仿真结果表明,所提出的改进分布估计算法能够有效的避免陷入局部最优值,在寻优精度、收敛速度以及算法的稳定性和鲁棒性上都有极大改善.     

一种针对QAP问题的改进蚁群算法研究

QAP(quadratic assignment problem二次分配问题)是经典的组合优化问题之一,广泛应用于许多领域中.本文研究了一种求解QAP的改进蚁群算法,我们将该算法与一种混合演化算法对QAPLIB中现实类问题的实验结果进行了比较,结果表明改进蚁群算法对该类型的问题有较优的结果,即优化效果好,运算量小,通用性强.     

带柯西变异的自学习改进烟花算法

针对烟花算法收敛速度慢和求解精度不高,论文提出了一种改进烟花算法--带柯西变异的自学习改进烟花算法.改进算法用全局搜索能力更强的柯西变异算子替代高斯变异算子,增大变异范围;用全局最优烟花个体和历史柯西火花的位置来构造新的爆炸半径使其不仅能够继承和学习历史信息,还能够自适应地调整步长;并使用可同时兼顾烟花质量与分布的"精英-随机"选择策略.使用了10个典型基准测试函数和10个0-1背包问题进行仿真实验,结果表明,与蝙蝠算法、粒子群算法、带高斯扰动的粒子群算法、烟花算法、增强烟花算法、自适应烟花算法相比.该算法在收敛速度、计算精度以及稳定性方面性能更优.     

Hard Real-Time Communication with the Timed Token Protocol: Current State and Challenging Problems

With the increasing use of distributed real-time systems, the ability of communication networks to handle real-time traffic is becoming more and more important. The timed token medium access control protocol, which has been now incorporated into several network standards such as FDDI and SAFENET due to its special timing property of bounded medium access time, is one of the most suitable and attractive candidate communication protocols for supporting distributed hard real-time applications. Extensive research has been conducted on using the timed token protocol to guarantee timely transmission of messages in a communication environment with hard real-time requirements. This paper intends to present a comprehensive review on recent advances in hard real-time communication with the timed token protocol. In addition, several challenging problems are identified.     

分布强实时系统的可预测性研究

分布强实时系统在国防、航空、航天等领域具有重要作用,可预测性是它的一个主要特点。针对一种分布强实时系统原理,分析和评测了影响强实时系统可预测性的诸延迟因素。给出了一种实时操作系统各开销的测试方法和结果。建立了分布环境下强实时任务响应时间和ＦＤＤＩ网络延迟上限的计算模型,并进行了实例分析。     

Hard real-time communication in multiple-access networks

With the increasing use of distributed hard real-time systems, the ability of computer networks to handle hard real-time message traffic is becoming more important. For traditional networks, maximizing the throughput or minimizing the average message delay is the most important performance criteria. In the hard real-time domain, however, concern focuses on satisfying the time constraints of individual messages. This paper examines recent developments in hard real-time communication in local area multiple-access networks. Two general strategies are used in hard real-time communication: the guarantee strategy and the best-effort strategy. In the former, messages are guaranteed to meet their deadlines during normal operation of the network. In the best-effort strategy, the network will attempt to send messages before their deadlines, but no guarantees are given. Real-time message traffic can be distinguished according to whether it is best suited for the guarantee strategy or the best-effort strategy. Although this paper concentrates on multiple-access networks, many of the concepts presented and lessons learned are also applicable to other types of networks.     

Scheduling hard and soft real-time communication in a controller area network

The paper introduces a mechanism to implement distributed scheduling for the CAN-bus resource in order to meet the requirements of a dynamic distributed real-time system. The key issues considered here are multicasting, distinguishing between hard real-time, soft real-time, and non-real-time constraints, achieving high resource utilization for the CAN-bus, and supporting dynamic hard real-time computing by allowing dynamic reservation of communication resources.     

Fail-Awareness: An Approach to Construct Fail-Safe Systems

We present a framework for building fail-safe hard real-time applications in timed asynchronous distributed systems subject to communication partitions and performance, omission, and crash failures. Most distributed systems built from commercial-off-the-shelf (COTS) processor and communication services are subject to such partitions because their COTS components do not provide hard real-time guarantees. Also custom designed systems can be subject to partitions due to unmaskable link or router failures. The basic assumption behind our approach is that each processor has a local hardware clock that proceeds within a linear envelope of real-time. This allows one to compute an upper bound on the actual delays incurred by a particular processing sequence or message transmission. Services and applications can use these computed bounds to detect when they cannot guarantee all their standard properties because of excessive delays. This allows an application to be fail-aware, that is, to detect when it cannot guarantee all its safety properties and in particular, to detect when to switch to a fail-safe mode.     

基于GIS的分布式实时协同制图系统的研究

由于Internet网络带宽限制等诸多方面的影响,基于GIS的分布式实时协同制图系统是较难实现的。采用复制式模型构造了一个基于GIS的分布式实时协同制图系统,并且采用动态数据格式作为各站点的交换数据,极大限度地战少了网络数据传输量,提高了系统的响应速度和稳定性,满足了协同制图系统对实时性的要求。     

Modeling distributed real-time systems with MAST 2

Switched networks have an increasingly important role in real-time communications. The IEEE Ethernet standards have defined prioritized traffic (802.1p) and other QoS mechanisms (802.1q). The Avionics Full-Duplex Switched Ethernet (AFDX) standard defines a hard real-time network based on switched Ethernet. Clock synchronization is also an important service in some real-time distributed systems because it allows a global notion of time for event timing and timing requirements. In the process of defining the new MAST 2 model, clock synchronization modeling capabilities have been added, and the network elements have been enhanced to include switches and routers. This paper introduces the schedulability model that will enable an automatic schedulability analysis of a distributed application using switched networks and clock synchronization mechanisms.     

Performance estimation for real-time distributed embedded systems

Many embedded computing systems are distributed systems: communicating processes executing on several CPUs/ASICs. This paper describes a performance analysis algorithm for a set of tasks executing on a heterogeneous distributed system. Tight bounds are essential to the synthesis and verification of application-specific distributed systems, such as embedded computing systems. Our bounding algorithms are valid for a general problem model: The system can contain several tasks with hard real-time deadlines and different periods; each task is partitioned into a set of processes related by data dependencies. The periods of tasks and the computation times of processes are not necessarily constant and can be specified by a lower bound and an upper bound. Such a model requires a more sophisticated algorithm, but leads to more accurate results than previous work. Our algorithm both provides tighter bounds and is faster than previous methods     

基于平滑调度的弱硬实时系统约束规范

约束规范是弱硬实时系统研究的基础。从弱硬实时系统的定义出发,提出了一个新的约束规范,它能够有效实现平滑调度。给出并证明了弱硬实时系统约束规范严格性比较的一个重要定理。业已证明,该约束规范具有良好的性能和较好的适用范围。     

Dynamic Task Scheduling in Hard Real-Time Distributed systems

This algorithm for scheduling tasks with hard real-time constraints—that is, tasks that must meet their deadlines-works dynamically on loosely coupled distributed systems.