共查询到20条相似文献,搜索用时 171 毫秒
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《计算机应用与软件》2016,(5)
针对采用数据透明传输的Zig Bee电梯无线轿厢通信存在信息传输滞后、通信效率较低的缺点,阐述三种常用Zig Bee协议栈并分析轿厢通信原理。以Stm32W108芯片为核心的Zig Bee无线模块作为应用平台,提出一种无线轿厢通信的实时性软件优化策略。该策略通过电梯主控制器端的无线模块通过串口端、无线端分别收集询问帧及应答帧,并由其在规定时间内回复电梯主控制器信息,以满足轿厢通信的时间要求,最后提出相关软件的流程设计。经实验表明,该优化策略能满足系统的实时性要求,无线轿厢通信系统的有效通信距离能够达到165 m,满足一般高层建筑的无线轿厢通信的距离要求。 相似文献
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该文主要介绍将实时操作系统应用于有轨电车轨道模块控制系统,通过实时系统弥补离散控制系统实时性差的问题。采取基于LPC1700的实时多任务操作系统μC/OS-Ⅱ进行有轨电车轨道模块的通信控制,从而实现了各个模块通信的实时性。 相似文献
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运动估计是剔除视频压缩中的时间冗余的关键,现有算法大都是基于全搜索策略的SAD匹配算法,这些算法虽然压缩性能很好,但计算复杂,实时性差。提出一种快速运动估计新算法,将块分割成多个子块,计算每个子块的灰度值之和与灰度值的平方和,将其整体作为一个参数再结合提出的三个匹配准则,求出当前帧和候选帧之间的最优运动估计。通过实验表明,采用该算法后计算的复杂度明显减小,实时性得到较大提高,其压缩性能却非常接近基于全搜索策略的SAD算法。 相似文献
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针对城市物流配送中客户需求量不确定且时效性要求较高的特点,考虑客户需求量为随机变量且有时间窗的车辆路径优化问题,同时基于不同的信息化调度水平,考虑了配送失败时的三种补救策略。构建了机会约束混合整数规划数学模型并转化为等价的确定性模型进行求解。提出了含有多种算子的改进混合进化算法来求解该模型,并基于算例,验证了算法的优越性。同时,对模型的参数敏感性和三种补救策略下的风险成本进行了分析。结果表明,采用提前预测,实时反馈,即时派出新车的补救策略可以最大程度保证满足客户时间约束,同时还具有降低配送路程的经济优势。 相似文献
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多选择背包问题离散狼群算法研究 总被引:1,自引:0,他引:1
狼群算法是一种通过模拟狼群的捕食行为和猎物分配方式提出的群体智能算法,为求解复杂组合优化问题提供了一种新的思路。目前狼群算法不能解决离散问题,以NP难中的经典问题——多选择背包问题的求解为研究对象,设计了基于离散空间的狼群算法。对于离散空间的狼群算法,通过将人工狼编码,重新设计了狼群的游走、奔袭和围捕过程,并设计了三个过程中的步长。把学习机制引入离散狼群算法,实现了人工狼之间的交流,且确立了自适应步长公式。结果表明:离散狼群算法成功实现了对离散问题的求解,为组合优化问题的求解提供了新方法。 相似文献
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Penalty Formulations and Trap-Avoidance Strategies for Solving Hard Satisfiability Problems 下载免费PDF全文
BenjaminW.Wah ZheWu 《计算机科学技术学报》2005,20(1):0-0
In this paper we study the solution of SAT problems formulated as discrete decision and discrete constrained optimization problems. Constrained formulations are better than traditional unconstrained formulations because violated constraints may provide additional forces to lead a search towards a satisfiable assignment. We summarize the theory of extended saddle points in penalty formulations for solving discrete constrained optimization problems and the associated discrete penalty method (DPM). We then examine various formulations of the objective function, choices of neighborhood in DPM, strategies for updating penalties, and heuristics for avoiding traps. Experimental evaluations on hard benchmark instances pinpoint that traps contribute significantly to the inefficiency of DPM and force a trajectory to repeatedly visit the same set of or nearby points in the original variable space. To address this issue, we propose and study two trap-avoidance strategies. The first strategy adds extra penalties on unsatisfied clauses inside a trap, leading to very large penalties for unsatisfied clauses that are trapped more often and making these clauses more likely to be satisfied in the future. The second strategy stores information on points visited before, whether inside traps or not, and avoids visiting points that are close to points visited before. It can be implemented by modifying the penalty function in such a way that, if a trajectory gets close to points visited before, an extra penalty will take effect and force the trajectory to a new region. It specializes to the first strategy because traps are special cases of points visited before. Finally, we show experimental results on evaluating benchmarks in the DIMACS and SATLIB archives and compare our results with existing results on GSAT, WalkSAT, LSDL, and Grasp. The results demonstrate that DPM with trap avoidance is robust as well as effective for solving hard SAT problems. 相似文献
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Port operations usually suffer from uncertainties, such as vessels’ arrival time and handling time and unscheduled vessels. To address this, this study presents a dynamic berth allocation and crane assignment specific problem (BACASP) when unscheduled vessels arrive at the port, which is branded the berth allocation and quay crane assignment specific problem with unscheduled vessels (UBACASP). A rolling-horizon based method is proposed to decompose the UBACASP into a multi-stage static decision BACASP, wherein a rescheduling margin-based hybrid rolling-horizon optimization method is developed by incorporating the event-driven and periodical rolling-horizon strategies as the urgency of dynamic events is evaluated. In each rolling horizon, a mixed integer linear programming model (MILP) is presented for the BACASP to minimize the total port stay time of vessels and the penalties of delays associated with the spatial and temporal constraints, such as the length of continuous berth, number of quay cranes (QCs) and non-crossing of QCs. A discretization strategy is designed to divide the continuous berth into discrete segments, and convert the BACASP to a discrete combinatorial optimization problem, which is efficiently solved by the proposed adaptive large neighborhood search algorithm (ALNS). Case studies with different problem characteristics are conducted to prove the effectiveness of the solution methods proposed in this study. Moreover, the performances of the ALNS and the existing methods for solving the BACASP are compared, and the advantages and disadvantages of different rolling strategies under different degrees of uncertainties are deeply analyzed. 相似文献
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Address autoconfiguration is one of the fundamental issues in mobile ad hoc networks (MANET). A node must need some form of
identity before participating in any sort of communication. So each host in a MANET needs to be uniquely addressed so that
the packets can be relayed hop-by-hop and delivered ultimately to the desired destination. Moreover, nodes in the MANET are
free to move and organize themselves in an arbitrary fashion. Therefore any fixed infrastructure based solution for assigning
identity (i.e. IP address) is not directly applicable to MANET. Under this infrastructureless and sporadic nature of the mobile
nodes, several protocols of address autoconfiguration in the mobile ad hoc networks (MANET) have been proposed. Although some
of these protocols perform decently in sparse and small networks, but exhibit poor performance (e.g., single point of failure,
storage limitation, large protocol overhead and so on) when the network is either dense or very large. In this paper, we propose
an efficient and scalable address autoconfiguration protocol that automatically configures a network by assigning unique IP
addresses to all nodes with a very low overhead and minimal cost. Evenly distributed Duplicate-IP address Detection Servers
are used to ensure the uniqueness of an IP address during IP address assignment session. In contrast to some other solutions,
the proposed protocol does not exhibit any problems pertaining to leader election or centralized server-based solutions. Furthermore,
grid based hierarchy is used for efficient geographic forwarding as well as for selecting Duplicate-IP address Detection Servers.
Through simulation results we demonstrate scalability, robustness, low latency, fault tolerance and some other important aspects
of our protocol. 相似文献
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Along with advancement of communication systems, the demand for fault-tolerance and real-time performance for communication protocols continues to increase. Communication protocols which perform recovery from any abnormal state to a normal state are called self-stabilizing protocols. However, in these protocols, real-time recovery is not taken into consideration. This paper discusses verification of communication protocols which have self-stabilizing and timeliness properties, which are called responsive protocols.Gouda et al. proposed a mathematical method to prove whether a given protocol specification satisfies the self-stabilizing property. However, this method is not automated and does not verify the timeliness property. This paper thus proposes an automated method for verification of responsive protocols. In this method, communication protocols are modeled by extended finite state machines and their states are represented by predicates. The self-stabilizing property is proven by verifying that sequences of such states which start from an arbitrary abnormal state converge in a normal state. Also, the timeliness property is proven by verifying that the convergence is done within a priori given time. 相似文献
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潘可 《单片机与嵌入式系统应用》2014,(2):5-8
在保护装置中最为稳定的引导程序U-Boot中实现了对该通用调试软件的通信协议的支持。基于U-Boot提供的独立应用开发框架,将独立的具有完整TCP/IP协议支持的lwIP协议栈移植至U-Boot。基于该协议栈以及U-Boot的独立应用开发框架,实现了对通用调试软件的复杂通讯协议的完整支持。经过上述技术改进,极大地扩展了通用调试软件的适用范围,加快了变电站工程实施中遇到的各种装置类似问题的解决速度。 相似文献