移动基站无线传感器网络2个参数的优化

针对一种移动基站协助数据收集模式,研究移动基站最佳缓冲区位置的设计问题,得出节点在发射半径r=R的情况下,当移动基站缓冲区的中心位于2／3R时,网络的总能量消耗最小,当中心位于1／2R时,网络的寿命最长。在r〈〈R的情况下,节点的发射功率可选择{l..k}中的一种传送数据,并给出通过插值作图法得到最佳基站缓冲区位置的设置与节点最佳发射功率的计算方法,相比采用固定功率发射方法,能够将网络寿命提高5倍。     

面向手机短信的隐私保护方案

针对手机短信存在的用户隐私泄露问题,设计一种面向手机短信的隐私保护方案.本方案结合非对称加密技术,通过使用信息接收者的公钥对原始短信进行加密获得短信密文,并结合预设的生命周期信息封装成短信自毁对象(Message Self-destructing Object,MSO)并通过运营商发送给接收者,接收者接收到MSO后对其生命周期进行验证,只有当前时间处于其生命周期内时,才能进一步使用其私钥对短信密文进行解密获取原始短信内容,一旦超过MSO的生命周期,则MSO将被自动删除以保护用户隐私安全.实验分析表明,本方案能够有效保护用户手机短信的隐私安全,实现生命周期控制并自动删除过期短信,并且对硬件系统要求低,开销合理,适合在人们日常生活中进行推广使用.     

基于移动—能量代价函数的无线自组织网络路由策略研究

能量均衡技术一直是无线自组织网络的热点研究领域.在深入研究网络信息传输特性的基础上,提出了一种基于移动-能量代价函数的无线自组织网络路由策略,并用于网络信息传输.首先,本文考虑节点连通性、能量均衡性,提出了一种节点移动策略;然后,以传输路径节点集合中的瓶颈节点剩余能量、传输链路数量作为准则,建立以网络节点为对象的能量代价函数.基于移动-能量代价函数的路由策略从链路层的决策转移到节点层的决策.最后,采用MATLAB数值仿真该路由策略的性能,结果显示:本文提出的移动-能量代价函数的路由策略既保持了原有路由优化的精度,延迟网络瓶颈节点能量下降速度,提高网络生存时间.     

Estimating life-form cover fractions in California sage scrub communities using multispectral remote sensing

The California sage scrub (CSS) community type in California's Mediterranean-type ecosystems is known for its high biodiversity and is home to a large number of rare, threatened, and endangered species. Because of extensive urban development in the past fifty years, this ecologically significant community type is highly degraded and fragmented. To conserve endangered CSS communities, monitoring internal conditions of communities is as crucial as monitoring distributions of the community type in the region. Vegetation type mapping and field sampling of individual plants provide ecologically meaningful information about CSS communities such as spatial distribution and species compositions, respectively. However, both approaches only provide spatially comprehensive information but no information about internal conditions or vice versa. Therefore, there is a need for monitoring variables which fill the information gap between vegetation type maps and field-based data. A number of field-based studies indicate that life-form fractional cover is an effective indicator of CSS community health and habitat quality for CSS-obligated species. This study investigates the effectiveness of remote sensing approaches for estimating fractional cover of true shrub, subshrub, herb, and bare ground in CSS communities of southern California. Combinations of four types of multispectral imagery ranging from 0.15 m resolution scanned color infrared aerial photography to 10 m resolution SPOT 5 multispectral imagery and three image processing models - per-pixel, object-based, and spectral mixture models - were tested.An object-based image analysis (OBIA) routine consistently yielded higher accuracy than other image processing methods for estimating all cover types. Life-form cover was reliably predicted, with error magnitudes as low as 2%. Subshrub and herb cover types required finer spatial resolution imagery for more accurate predictions than true shrub and bare ground types. Positioning of sampling grids had a substantial impact on the reliability of accuracy assessment, particularly for cover estimates predicted using multiple endmember spectral mixture analysis (MESMA) applied to SPOT imagery. Of the approaches tested in this study, OBIA using pansharpened QuickBird imagery is one of the most promising approaches because of its high accuracy and processing efficiency and should be tested for more heterogeneous CSS landscapes. MESMA applied to SPOT imagery should also be examined for effectiveness in estimating factional cover over more extensive habitat areas because of its low data cost and potential for conducting retrospective studies of vegetation community conditions.     

Optimal allocation of change points in simple step-stress experiments under Type-II censoring

In simple step-stress experiments under Type-II censoring with the cumulative exposure model and exponentially distributed lifetimes, maximum likelihood estimates (MLE) of the expected lifetimes may not exist due to the absence of failure times either before or after the stress change point. For this reason, when planning a step-stress experiment, the change point could be chosen so as to minimize the probability of non-existence of the MLE. These non-existence probabilities are examined and compared in the one- as well as the two-sample situations. Moreover, the optimal allocations of the change points are discussed and the effects of the use of non-optimal choices for the change points are assessed.     

面向数据对象实体类的需求分析方法

文章介绍一种作者在多个管理信息系统开发中采用的面向数据对象实体类的需求分析方法（ＤＩＣＡＭ）。该方法以数据为中心分析系统的结构。该方法根据数据来源将数据客体分为三类：源数据客体、混合数据客体和生成数据客体。该方法一方面从纵向分析数据客体的属性组成和结构,另一方面从横向分析数据实例特征,将各个数据客体的数据划分为不同的实例类,以实例类的状态、生命过程、组成组描述系统中的数据产生变化,通过实例类状态的获得反映系统的功能。     

近线性神经和元非线性神经元

人工神经网络(ANN)中普遍采用的神经元模型具有单调有界的I／O特性,该文称其为近线性神经元(ALN,approximate－linear neuron),ALN既简化了网络的复杂性,也是限制ANN能力的一个瓶径.通过比较Hopfield神经网络的稳定性和Conway生命游戏的复杂行为,该文提出非线性神经元(NLN,non－linear neuron)的概念,其I／O特性是完全非线性的.ALN可以进一步提高ANN的非线性,从而增强它的功能,余数制神经网络是一个例子.     

专家系统软件开发生存期模型分析

文章根据专家系统类软件的特点,在分析已有软件开发生存期模型优缺点基础上,提出了一种适用于专家系统的开发模型,它以瀑布模型为基本框架,在不同开发阶段引入了快速原型开发模型和面向对象技术以克服瀑布模型的缺点。实践表明这种开发模型是可行的。     

具有行为强化学习能力的人工生命进化模型设计

人工生命进化模型设计的关键问题是学习与进化之间的关系,在自主体生存期内的学习过程可以通过不同的遗传方式指导个体行为的进化。该文利用进化算法和人工神经网络的研究方法,设计了两种不同的人工生命自主体的进化模型,模型解决了先天的遗传进化和后天的个体神经系统强化学习的有机结合问题,并且得出结论认为,强化学习有助于自主体适应复杂的外部环境,同时学习也可以直接或间接地使该适应性成为自主体遗传基因上的固定成分。     

生活形态研究与设计艺术关系的辨析

随着产品设计越来越关注固定人群的生活方式,反映和满足特定人群的特定需求的产品在设计领域逐渐凸显出来。把握生活形态研究和设计艺术两者的关系,让产品更加趋于特定人群的需求。从而使产品在使用的过程中激发人们的联想,产生共鸣。