空时码不对称调制方法研究

提出了空时编码不对称调制方案。软件分析了比特交织空时编码调制系统在Rayleigh衰落信道下的成对错误概率上界。对于常用的几种映射方案,采用不对称调制星座图,可以增大汉明距离为1的调制符号间的最小欧氏距离,从而提高系统的编码增益和分集增益,降低成对错误概率的上界。理论分析和仿真结果表明,不对称调制星座图改善了比特交织空时编码调制系统在Rayleigh信道下的性能,并且没有牺牲频谱效率和增加系统复杂性的代价。     

一种新的基于MQAM的PLNC去噪映射算法

物理层网络编码(Physical Layer Network Coding,PLNC)在高阶幅度和相位调制中存在星座点模糊现象。针对这一问题提出了一种物理层网络编码去噪映射算法。在该算法中,中继节点对接收信号进行星座点重新布局,按一定规律将星座点合并,经过处理后的信号星座点降低了一半,进而下行链路的调制阶数也降低了一半,星座图相邻点之间的欧氏距离变大,系统误码率性能得到提高;且中继节点只需解调-重映射-调制,处理复杂度低。通过计算机仿真验证了该算法的有效性。     

空时分组码的简化译码方法

实际无线通信应用中,译码方法的简化一定程度上降低了移动端的功率消耗。文章根据星座图的几何结构,从数学角度出发,描述了一种8进制相移键控(8PSK)下空时分组码的简化最大似然(ML)译码方法,并将该方法推广到幅度相移键控(APSK)映射情况下的译码。对最大似然译码方法和文中简化最大似然方法的仿真结果及译码计算复杂度进行了分析和比较,结果表明简化最大似然译码算法只是降低了计算复杂度,并没有影响误码率。     

一种基于差分星座图的调制体制识别算法

针对π/4QPSK和8PSK信号调制体制识别,提出了一种基于相位差分信号星座图的调制体制识别算法.算法利用两种相位差分信号的星座图点数作为识别特征.对单级减法聚类算法不能很好地适应多种调制方式识别的问题,采用一种改进的多级聚类算法得到星座图点数,并通过计算机仿真获得了最佳聚类参数.仿真结果表明,改进后的算法在200个码元下的识别性能至少提高1dB,低信噪比下的性能得到了很大改善.12dB以上时,π/4QPSK和8SK信号的正确识别率达到了100%.     

对称α稳定分布噪声下的软解映射算法

对称α稳定(SαS)分布噪声是一种非高斯噪声,相对于高斯噪声具有明显的脉冲特性,因此高斯噪声下的软解映射算法不适用于SαS分布噪声中。为解决该问题,根据高斯噪声下软解映射算法的对数似然比和信号幅度呈线性的特点,提出一种SαS分布噪声下基于欧式距离的软解映射算法,只需在高斯噪声下的软解映射算法和译码算法之间加入预处理算法,限制比特软信息的幅度,并将幅度过高的软信息置零。仿真结果显示,该算法实现简单、运算量低,所需信噪比在α=1.84的SαS分布噪声下比Huber算法低0.3 dB,在α=1.3的SαS分布噪声下低2 dB~5 dB。     

基于加权函数选择的伺服系统性能优化设计方法

为了尽可能提高伺服系统的性能, 提出一种基于加权函数选择的性能优化设计方法. 首先, 给出性能优化设计问题的描述; 其次, 给出了线性矩阵不等式(Linear matrix inequality, LMI)形式的优化指标; 再次, 提出一种基于加权函数选择的系统性能优化设计迭代算法; 最后, 利用Bode积分关系分析了算法的收敛性. 所提出的系统性能优化设计算法易于迭代计算, 仿真实例验证了算法的有效性.     

MIMO-OFDM系统中一种改进的QRM-MLD检测算法

在MIMO-OFDM无线通信系统中,常规的QRM-MLD检测算法的复杂度是固定的。为了降低算法的复杂度,基于传统的QRM-MLD的树搜索思想,提出了一种改进的算法,该算法能根据星座点之间的相对距离以及在不同信道条件下接收符号在星座图中的位置差别,在保留的M个候选值中进一步减少候选点数。仿真结果表明,该算法能保证在误码率性能损失很小的情况下大大减少检测过程的访问节点数,降低了算法的平均复杂度。     

面向图相似性搜索的高效图编辑距离算法

在图相似性搜索问题中,图编辑距离是较为普遍的度量方法,其计算性能很大程度上决定了图相似性搜索算法的性能。针对传统图编辑距离算法中存在的因大量冗余映射和较大搜索空间导致的性能低下问题,提出了一种改进的图编辑距离算法。该算法首先对图中顶点进行等价划分,以此计算映射编码来判断等价映射;然后定义映射完整性更新等价映射优先级,选出主映射参与扩展;其次,设计高效的启发式函数,提出基于映射编码的下界计算方法,快速得到最优映射。最后,将改进的图编辑距离算法扩展应用于图相似性搜索。在不同数据集上的实验结果表明,该算法具有更好的搜索性能,在搜索空间上最大可降低49%,速度提升了约29%。     

改进遗传算法在PID优化中的应用

现有的比例积分微分(PID)优化设计算法难以兼顾系统对快速性、稳定性和鲁棒性的要求。为此,提出一种改进的Pareto遗传算法。该算法采用新的拥挤距离计算算法,改进非支配性的比较算法,引入双重精英机制,提高进化效率和解的质量,并且解的多样性好。将该算法应用于PID多目标优化设计,仿真结果表明,决策者可根据当前工作需求在所得的Pareto解集中选择最优的满意解。     

基于改进CMGA模糊规则优化及应用

针对压缩映射遗传算法(CMGA)操作效率太低,收敛至最优解迭代次数太多的问题,采用了近亲交叉回避策略改进压缩映射遗传算法,不但保证收敛到全局最优解,而且提高了算法的收敛速度和操作效率.为了能对具体被控对象的性能进行有选择性的控制,分析了ITAE积分性能指标作为目标函数的缺点,在目标函数中增加了超调量、控制量和上升时间等综合因素,得到了性能更好的目标函数,应用于改进压缩映射遗传算法的适应度函数,并把以上改进算法的模糊规则优化应用于地板采暖系统,与模糊控制、未改进的压缩映射遗传算法优化模糊控制进行比较,提高了系统的控制效率,简化了模糊控制器的设计难度.仿真结果证明该方法在地板采暖系统中的有效性.     

Only connect: teaching, technology and telesis

Abstract This paper describes an approach to the design of interactive multimedia materials being developed in a European Community project. The developmental process is seen as a dialogue between technologists and teachers. This dialogue is often problematic because of the differences in training, experience and culture between them. Conditions needed for fruitful dialogue are described and the generic model for learning design used in the project is explained.     

European Community policy and the market

Abstract This paper starts with some reflections on the policy considerations and priorities which are shaping European Commission (EC) research programmes. Then it attempts to position the current projects which seek to capitalise on information and communications technologies for learning in relation to these priorities and the apparent realities of the marketplace. It concludes that while there are grounds to be optimistic about the contribution EC programmes can make to the efficiency and standard of education and training, they are still too technology driven.     

一种自适应子融合集成多分类器方法

融合集成方法已经广泛应用在模式识别领域,然而一些基分类器实时性能稳定性较差,导致多分类器融合性能差,针对上述问题本文提出了一种新的基于多分类器的子融合集成分类器系统。该方法考虑在度量层融合层次之上通过对各类基多分类器进行动态选择,票数最多的类别作为融合系统中对特征向量识别的类别,构成一种新的自适应子融合集成分类器方法。实验表明,该方法比传统的分类器以及分类融合方法识别准确率明显更高,具有更好的鲁棒性。     

Avoiding semantic and temporal gaps in developing software intensive systems

Development of software intensive systems (systems) in practice involves a series of self-contained phases for the lifecycle of a system. Semantic and temporal gaps, which occur among phases and among developer disciplines within and across phases, hinder the ongoing development of a system because of the interdependencies among phases and among disciplines. Such gaps are magnified among systems that are developed at different times by different development teams, which may limit reuse of artifacts of systems development and interoperability among the systems. This article discusses such gaps and a systems development process for avoiding them.     

Designing economic np control charts: A programmed simulation approach

This paper presents control charts models and the necessary simulation software for the location of economic values of the control parameters. The simulation program is written in FORTRAN, requires only 10K of main storage, and can run on most mini and micro computers. Two models are presented - one describes the process when it is operating at full capacity and the other when the process is operating under capacity. The models allow the product quality to deteriorate to a further level before an existing out-of-control state is detected, and they can also be used in situations where no prior knowledge exists of the out-of-control causes and the resulting proportion defectives.     

The development of robot art

Going through a few examples of robot artists who are recognized worldwide, we try to analyze the deepest meaning of what is called “robot art” and the related art field definition. We also try to highlight its well-marked borders, such as kinetic sculptures, kinetic art, cyber art, and cyberpunk. A brief excursion into the importance of the context, the message, and its semiotics is also provided, case by case, together with a few hints on the history of this discipline in the light of an artistic perspective. Therefore, the aim of this article is to try to summarize the main characteristics that might classify robot art as a unique and innovative discipline, and to track down some of the principles by which a robotic artifact can or cannot be considered an art piece in terms of social, cultural, and strictly artistic interest. This work was presented in part at the 13th International Symposium on Artificial Life and Robotics, Oita, Japan, January 31–February 2, 2008     

Explanation and prediction: an architecture for default and abductive reasoning

Although there are many arguments that logic is an appropriate tool for artificial intelligence, there has been a perceived problem with the monotonicity of classical logic. This paper elaborates on the idea that reasoning should be viewed as theory formation where logic tells us the consequences of our assumptions. The two activities of predicting what is expected to be true and explaining observations are considered in a simple theory formation framework. Properties of each activity are discussed, along with a number of proposals as to what should be predicted or accepted as reasonable explanations. An architecture is proposed to combine explanation and prediction into one coherent framework. Algorithms used to implement the system as well as examples from a running implementation are given.     

Three Process Perspectives: Organizations, Teams, and People

This paper provides the author's personal views and perspectives on software process improvement. Starting with his first work on technology assessment in IBM over 20 years ago, Watts Humphrey describes the process improvement work he has been directly involved in. This includes the development of the early process assessment methods, the original design of the CMM, and the introduction of the Personal Software Process (PSP)^SM and Team Software Process (TSP){^SM}. In addition to describing the original motivation for this work, the author also reviews many of the problems he and his associates encountered and why they solved them the way they did. He also comments on the outstanding issues and likely directions for future work. Finally, this work has built on the experiences and contributions of many people. Mr. Humphrey only describes work that he was personally involved in and he names many of the key contributors. However, so many people have been involved in this work that a full list of the important participants would be impractical.     

基于复小波噪声方差显著修正的SAR图像去噪

提出了一种基于复小波域统计建模与噪声方差估计显著性修正相结合的合成孔径雷达(Synthetic Aperture Radar,SAR)图像斑点噪声滤波方法。该方法首先通过对数变换将乘性噪声模型转化为加性噪声模型,然后对变换后的图像进行双树复小波变换(Dualtree Complex Wavelet Transform,DCWT),并对复数小波系数的统计分布进行建模。在此先验分布的基础上,通过运用贝叶斯估计方法从含噪系数中恢复原始系数,达到滤除噪声的目的。实验结果表明该方法在去除噪声的同时保留了图像的细节信息,取得了很好的降噪效果。     

How do children do mathematics with LOGO?

Abstract  This paper considers some results of a study designed to investigate the kinds of mathematical activity undertaken by children (aged between 8 and 11) as they learned to program in LOGO. A model of learning modes is proposed, which attempts to describe the ways in which children used and acquired understanding of the programming/mathematical concepts involved. The remainder of the paper is concerned with discussing the validity and limitations of the model, and its implications for further research and curriculum development.