ActiveX构件开发指南（二）：ActiveX控件的创建（下）

通过属性页的形式组织控件的属性 使用属性过程所创建的一些简单属性将自动显示在Visual Basic的属性窗口中。属性页提供了一种不用属性窗口查看ActiveX控件属性的方法。当控件属性太复杂,很难用属性窗口来描述时,可采用分组的方法,将相关的属性组织成一页,用属性页来为这些属性提供一个对话框形式的接口。 与控件连接的每一个属性页都成为选项卡化的属性对话框上的一个选项卡。Visual Basic处理选项卡化对话框所说明的页面的所有细节,并管理“OK”、Cancel”和“Apply”等按钮。用户必须做的全部事情就是设计将用于设置属性值的控件。下面我们首先介     

基于XQuery查询的表格数据分页的实现

针对Web应用系统中对表格数据分页显示的需求,简要介绍了利用GridView控件的内置分页技术实现分页的方法,提出并实现了一种利用XQuery查询实现装备保障信息综合管理系统中表格数据的分页显示的方法。     

一种基于链表的战场态势显示方法

本文提供了一种基于链表的战场态势显示方法。通过构建图标成员链表,对接收到的实时的地理信息报文进行相应算法处理,在处理过程中预留消息过滤接口,进而实现对成员链表的更新和地图图标的刷新显示,最终获得一种在大量地理信息变化条件下,既能够保证地理信息显示消息的及时有效,又具备有效地理信息过滤功能的战场态势显示方法。     

基于ASP.NET的分页技术

随着网络的发展,网络服务器的运行效率显得非常重要。针对WEB数据库记录的显示问题,讨论了在ASP．NET框架下使用DataGrid控件对数据库记录的默认和自定义分页显示技术,并给出了一种高效的自定义分页方式。     

基于MFC消息机制与Direct3D的雷达目标显示实现

针对现代雷达综合化和信息化的发展趋势,为满足对雷达目标的多功能处理以及显示容量提升的需求,提出了一种在MFC构架下结合DirectX图形技术实现较大数量目标显示控制的方法。该方法使用Window控件来封装雷达目标类,利用控件的实现及其消息映射机制简化目标在终端显示时的生成、选取、更新、删除及叠加等功能处理中的计算和消息响应过程,同时采用Direct3D技术降低目标的绘制和刷新时间,提高了目标的显示批数。     

Win32全局钩子在VC5中的实现

Windows系统是建立在事件驱动的机制上的,说穿了就是整个系统都是通过消息的传递来实现的。而钩子是Windows系统中非常重要的系统接口,用它可以截获并处理送给其他应用程序的消息,来完成普通应用程序难以实现的功能。钩子的种类很多,每种钩子可以截获并处理相应的消息,如键盘钩子可以截获键盘消息,外壳钩子可以截取、启动和关闭应用程序的消息等。本文在VC5编程环境下实现了一个简单的鼠标钩子程序,     

GridView控件数据分页方法研究

数据分页是Web应用程序开发中经常使用的一种技术,也是提高Web数据访问性能的主要手段。介绍了在ASP.NET 4.0中常用的GridView控件,深入研究了它的两种分页显示方法,并给出了相关的基本概念及相应的核心代码。     

基于校园机会网络的协作小组缓存调度策略

缓存管理已经成为机会网络的研究热点,目前大多数缓存管理方法都集中在单节点,本文在校园协作学习背景下提出了缓存共享的协作小组资源调度方法.节点活跃度描述了移动节点的缓存空间利用率和节点参与消息转发积极性,消息树描述了消息在网络中的扩散程度.以协作小组为单位建立已送达消息链表,对已成功投递消息所占缓存空间及时进行释放.该方法能有效提升节点空间利用率和消息投递率并且降低了消息的投递延迟.实验结果表明,与已有算法相比,消息投递成功率平均提高了10.53％,为小组缓存的共享利用与资源的高效调度提供方法.     

基于Visual Basic与RS232串行通信的温度监测系统

在VB的通信控件Mscomm属性设置和事件响应的基础上,在WindowsXP的环境下,利用通信控件实现与单片机串行通信,把单片机采集的温度上传到PC机,同时利用Visual Basic图片框控件PictureBox显示出来,达到对温度的实时监测的目的.     

利用Spring MVC实现数据分页显示处理

结合资源查询需求,讨论了用Spring MVC实现数据分页显示编程处理思路与技巧。在介绍Spring MVC的工作过程的基础上,分析讨论了资源查询分页处理的设计过程。控制器中通过URL参数传递分页信息,在业务逻辑中则通过方法参数传递分页信息,通过SQL语句的关联查询处理,可限制只从数据库读取当前页的数据。视图显示中,通过EL表达式获取来自模型的数据。文中介绍的方法具有较大通用性,实现了分页查询处理的高效化。     

机会网络中能量有效的副本分布状态感知路由机制

针对机会网络中的节点能耗与消息扩散程度之间存在矛盾,基于节点能耗与副本状态感知的路由机制可以显著地改善资源受限场景的网络性能,综合考虑消息扩散程度与节点剩余能量,并结合节点相遇概率预测方法,提出能量有效的副本分布状态感知路由机制,为消息分布式地选择合理的中继节点。仿真结果表明,所提出的路由机制能够有效降低网络负载,并大幅改善消息投递率和平均时延性能。     

Gossip-based ad hoc routing

Many ad hoc routing protocols are based on some variant of flooding. Despite various optimizations of flooding, many routing messages are propagated unnecessarily. We propose a gossiping-based approach, where each node forwards a message with some probability, to reduce the overhead of the routing protocols. Gossiping exhibits bimodal behavior in sufficiently large networks: in some executions, the gossip dies out quickly and hardly any node gets the message; in the remaining executions, a substantial fraction of the nodes gets the message. The fraction of executions in which most nodes get the message depends on the gossiping probability and the topology of the network. In the networks we have considered, using gossiping probability between 0.6 and 0.8 suffices to ensure that almost every node gets the message in almost every execution. For large networks, this simple gossiping protocol uses up to 35% fewer messages than flooding, with improved performance. Gossiping can also be combined with various optimizations of flooding to yield further benefits. Simulations show that adding gossiping to AODV results in significant performance improvement, even in networks as small as 150 nodes. Our results suggest that the improvement should be even more significant in larger networks.     

带有能量补给的异构无线传感器网络拓扑控制算法

针对当前算法主要对拓扑构建或拓扑维护单独研究的问题,提出了一种将两个过程组合的拓扑控制算法,可以适应于通信和能量异构的网络。拓扑构建以较少的通信开销构建连通支配集,而拓扑维护由sink节点基于时间、能量或故障机制执行局部或全局修复策略以节约能量。理论分析和仿真实验证实,算法能以较少的时间和通信开销构建拓扑并延长网络生命时间。     

Energy efficient secured routing protocol for MANETs

The design of routing protocol with energy efficiency and security is a challenging task. To overcome this challenge, we propose energy-efficient secured routing protocol. The objective of our work is to provide a secured routing protocol, which is energy efficient. To provide security for both link and message without relying on the third party, we provide security to the protocol by choosing a secure link for routing using Secure Optimized Link State Routing Protocol. Each node chooses multipoint relay nodes amongst the set of one-hop neighbors, so as to reach all two-hop neighbors. The access control entity authorizes nodes announcing the node identification to the network. In addition, the access control entity signs a public key Ki, a private key ki, and the certificate Ci required by an authorized node to obtain the group key. Each node maintains a route table with power status as one of its entry. After selecting the link, on requirement of a new route, we check nodes’ power status in its routing table and then accordingly arise a route. Then, we perform group key distribution using the generated keys using a small number of messages which helps reducing energy consumption. The group key can be altered periodically to avoid nonauthorized nodes and to avoid the use of the same group key in more than some amount of data. Then, we provide communication privacy for both message sender and message recipient using Secure Source Anonymous Message Authentication Scheme. Thereby, the message sender or the sending node generates a source anonymous message authentication for message for releasing each message based on the MES scheme. Hence, our approach will provide message content authenticity without relying on any trusted third parties.     

Congestion Control Performance of R-DSDV Protocol in Multihop Wireless Ad Hoc Networks

Ad hoc wireless networks are composed of mobile nodes communicating through wireless links, without any fixed backbone infrastructure. Frequent topology changes due to node mobility make routing in such dynamic networks a challenging problem. Moreover, successful message routing implies every mobile node is potentially capable of acting as a router, thus supporting store-and-forward mechanisms. However, resource limitations on these nodes also require a control on congestion due to message forwarding. In this paper, we consider our recently proposed randomized version of the well-known Destination-Sequenced Distance Vector (DSDV) routing protocol, referred to as R-DSDV, and validate its performance through extensive simulation experiments. Our results demonstrate that a probabilistic control on message traffic based on local tuning of protocol parameters is feasible, and that R-DSDV outperforms the basic DSDV protocol by significantly reducing the average queue size associated with each mobile node and hence the average packet delay.     

Variations on a theme by Huffman

In honor of the twenty-fifth anniversary of Huffman coding, four new results about Huffman codes are presented. The first result shows that a binary prefix condition code is a Huffman code iff the intermediate and terminal nodes in the code tree can be listed by nonincreasing probability so that each node in the list is adjacent to its sibling. The second result upper bounds the redundancy (expected length minus entropy) of a binary Huffman code byP_{1}+ log_{2}[2(log_{2}e)/e]=P_{1}+0.086, whereP_{1}is the probability of the most likely source letter. The third result shows that one can always leave a codeword of length two unused and still have a redundancy of at most one. The fourth result is a simple algorithm for adapting a Huffman code to slowly varying esthnates of the source probabilities. In essence, one maintains a running count of uses of each node in the code tree and lists the nodes in order of these counts. Whenever the occurrence of a message increases a node count above the count of the next node in the list, the nodes, with their attached subtrees, are interchanged.     

基于消息传输率的时延容忍网络路由

针对时延容忍网络(DTNs),提出基于消息传输率的路由(DTRR)。将每条消息划分若干个消息块。当源节点遇见合适的转发节点就传输消息块,否则就将消息块存于缓存区中。同时,DTRR路由结合相遇频率、相遇时长和缓存区的可用空间,推导链路的消息传输率。再依据消息传输率,选择下一跳转发节点。仿真结果表明,提出的DTRR路由在消息传输率方面的性能优于同类的等待路由(SWR)。     

Optimal energy efficiency routing strategy based on community in mobile social network

An optimal energy efficiency routing strategy based on community was proposed,which minimized the network energy consumption under the given delay constraint.Firstly the expected energy consumption and delay of message delivery in the connected network were obtained through Markov chain.Then the comprehensive cost function for delivering message from source node to destination node was designed,which was combined with energy consumption and delay.Thus,the optimization function to comprehensive cost of relay node delivering message was obtained,and further the reward function of relay node was gotten.Finally the optimal expected reward of optimal relay node was achieved using the optimal stopping theory,so as to realize the optimal energy efficiency routing strategy.In simulations,the average energy consumption,the average delay and the average delivery ratio of routing optimization strategy were compared with those of other routing strategies in related literatures.The results show that the strategy proposed has smaller average energy consumption,shorter average delay and higher average delivery ratio,gaining better energy consumption optimization effect.     

Message redundancy removal of multi-copy routing in delay tolerant MANET

This article puts forward a new scheme to control message redundancy efficiently in delay tolerant mobile Ad-hoc networks(MANET).The class of networks generally lacks end-to-end connectivity.In order to improve the efficiency that messages are delivered successfully,multiple message copies routing protocols are usually used,but the network load is increased due to a large number of message redundancies.In the study,by using counter method,every node adds an encounter counter based on epidemic routing scheme...     

Deadlock Avoidance in Store-and-Forward Networks--II: Other Deadlock Types

This paper describes the construction of loop-free buffer graphs which avoid four types of buffer deadlocks in store-and-forward networks. 1) Progeny deadlock, where original messages spawnother ones, and buffer contention occurs between the original and progeny messages. This occurs when positive or negative acknowledgments are created, e.g., if messages reverse direction after encountering a path failure. 2) Copy-release deadlock, where a message copy is stored at the source node and the buffer is not released until an acknowledgment is received from the destination node. Buffer contention may arise among the original messages, stored copies, and acknowledgments. 3) Pacing deadlock, where a local flow control protocol is used between a network node and attached terminals. Buffer contention may arise between the message flows into and out of the terminal, preventing the transmission of go-ahead commands. 4) Reassembly deadlock, whereby reassembly of packetized messages at the destination node cannot be completed. The solution presented here has the novel features of not requiring preallocation of reassembly buffers before transmission of multiple packets of a multipacket message, and not requiring dedication of buffer space at intermediate nodes for individual messages. These schemes are believed to have modest buffer requirements at each node, and if adequate buffer pools are provided, will incur negligible performance degradations under normal conditions, with overhead increasing under heavy buffer usage when deadlock is near.