Forward and Backward Simulations

A unified, comprehensive presentation of simulation techniques for verification of concurrent systems is given, in terms of a simple untimed automaton model. In particular, (1) refinements, (2) forward and backward simulations, (3) hybrid forward-backward and backward-forward simulations, and (4) history and prophecy relations are defined. History and prophecy relations are abstract versions of the history and prophecy variables of Abadi and Lamport, as well as the auxiliary variables of Owicki and Gries, Relationships between the different types of simulations, as well as soundness and completeness results, are stated and proved. Finally, it is shown how invariants can be incorporated into all the simulations. Even though many results are presented here for the first time, this paper can also be read as a survey (in a simple setting) of the research literature on simulation techniques. The development for untimed automata is designed to support a similar development for timed automata, Part II of this paper will show how the results of this paper can be carried over to the setting of timed automata.     

ADVISOR软件的混合仿真方法

该文首先介绍了前向仿真方法和后向仿真方法，分析了其工作原理和优缺点。接着描述了美国电动汽车仿真软件ADVISOR的混合仿真方法，它是以后向仿真方法为主，前向仿真方法为辅的混合仿真方法。然后以一混合动力汽车模型为例，分析了ADVISOR的工作原理。最后具体分析了一个典型仿真模块一车轮模块的模型，比较了其中的前向路径与后向路径的差异，具体说明了混合仿真方法的实现。该文对ADVISOR软件的应用具有参考作用。     

ADⅥSOR软件的混合仿真方法

该文首先介绍了前向仿真方法和后向仿真方法,分析了其工作原理和优缺点.接着描述了美国电动汽车仿真软件ADVISOR的混合仿真方法,它是以后向仿真方法为主,前向仿真方法为辅的混合仿真方法.然后以一混合动力汽车模型为例,分析了ADⅥSOR的工作原理.最后具体分析了一个典型仿真模块-车轮模块的模型,比较了其中的前向路径与后向路径的差异,具体说明了混合仿真方法的实现.该文对ADVISOR软件的应用具有参考作用.     

针对IPTV快进快退优化的媒体封装格式

通过分析网络电视(IPTV)服务的特性和快进快退操作对服务器的影响,设计一种对快进快退操作进行优化的流媒体文件封装与索引格式,在采用数据块状存储的基础上,提出帧类别存储策略。性能对比实验表明,使用该文件格式的IPTV服务器提高了在快进快退模式下的性能。     

为何丽讯进 东芝退 2009年丽讯超预期300%完成30000台销量

2009年的国内投影机市场,用乱世来形容一点不为过。市场、品牌、渠道等层面变数颇多:全球金融海啸对投影机市场的影响仍在继续;老牌日系品牌退出中国市场的消息不断;各大厂商和渠道商分分合合,国内渠道格局大变。俗话说乱世出英雄,在充满变化的市场环境下,来自美国的投影品牌丽讯犹如一匹黑马,在2009年取得了骄人的成绩,令整个投影行业为之侧目。     

为何丽讯进 东芝退——2009年丽讯超预期300％完成30000台销量

2009年的国内投影机市场,用"乱世"来形容一点不为过.市场、品牌、渠道等层面变数颇多:全球金融海啸对投影机市场的影响仍在继续;老牌日系品牌退出中国市场的消息不断;各大厂商和渠道商分分合合,国内渠道格局大变.     

一种新的前后向扩散血管图像增强方法

提出一种新的血管图像去噪和锐化方法。在对血管多尺度分析的基础上,利用血管响应函数替代梯度,构建血管的一致性扩散系数。该扩散系数包含前向和后向扩散操作,在去除图像噪声的同时,可以锐化血管。在合成图像、肺小血管图像上进行仿真实验,结果表明,该方法适用于模糊的医学血管噪声图像,不仅能较好地去除噪声,而且能锐化血管边缘。     

智能合约辅助下满足前后向安全的动态可搜索加密方案

动态可搜索加密过程易受文件注入攻击和信息泄露导致的信息滥用攻击,同时现有基于公钥密码体制构造的动态可搜索加密方案往往涉及大量双线性对运算,不能满足实际应用的效率要求。通过引入智能合约,提出一种满足前后向安全的动态可搜索加密方案。以智能合约取代传统的搜索服务器进行关键字陷门匹配测试,解决传统搜索服务器必须满足诚实且好奇的设定问题,在此过程中避免大量使用双线性对运算,而是只执行一些简单的哈希操作,从而提升密文数据搜索阶段的计算效率。该方案满足前向安全性和后向安全性,即旧的搜索陷门不能用于搜索更新后的文件,且后续搜索不会泄露已删除文件所对应的索引信息。分析结果表明,与现有公钥密码体制下的动态可搜索加密方案相比,该方案在安全性和计算效率方面更具优势,适用于大数据通信环境。     

A co-processed contour tracing algorithm for a smart camera

This paper describes a new approach for a contour-tracing algorithm targeting a low-power smart camera for industrial inspection. This embedded system consists of the three major components: CMOS sensor, FPGA and microprocessor. By analysing a linear-time algorithm used for simultaneously labelling connected components and their contours, two independent tasks could be identified. By efficiently assigning these two parts to the FPGA and the microprocessor achieving high-speed real-time operation is possible. The novelty of the proposed method is the development of a sequential co-processing algorithm for the FPGA. A Contour-Neighbourhood 3 × 3 filter kernel for converting the grey-level data to an intermediate representation containing directional information was added into an FPGA image-processing design. This pre-processed data is then provided to a software component which is executed on a microprocessor. The final result of this analysis is a sorted list of contour points for each object in the image. Further increases of the data throughput and the workload of the hardware resources are achievable by pipelining the subtasks of consecutive images. The runtime behaviour of this parallel operation is sufficient for meeting the real-time requirements of an industrial 2D measurement system.     

一种前后向复扩散图像增强算法

传统的图像增强算法无法在去除噪声的同时保留图像的纹理.为此,本文从线性前向复扩散的原理出发,研究了线性后向复扩散的图像增强功能,将前向复扩散和后向复扩散相结合,给出了一种前后向复扩散图像增强算法.实验结果表明:该算法抑制了图像中的微弱噪声,有效地增强了图像,保留了图像的细节纹理,没有产生错误的图像增强效果,可以获得很好的图像增强效果.     

基于双向推理的主体框架

文章提出了一个基于双向推理的主体框架FBRA,它是一个混合型的主体框架,主体既是反应的又是慎思的。它的推理内核是正向推理和反向推理相结合。正向推理用于对环境的反应,包括对其他主体的反应。反向推理基于溯因推理,用于信念修正、规划、多主体协调和多主体通信等。     

A contour tracing algorithm that preserves common boundaries between regions

In most literatures, the boundary of a region R is defined as the set of pixels in R that have at least one neighbor outside R. Applying this definition to images with multi-labels, for example results of segmentation, one will end up with nonoverlapping boundaries between regions. This contradicts the physical boundary concept and makes shape analysis among regions difficult. This paper presents a new, efficient contour tracing algorithm based on the extended boundary concept, a common boundary representation which shifts the inter-pixel boundary by one-half pixel toward the right and lower directions. It is shown that, in addition to the common boundary representation, the new algorithm has the following advantages over the old approaches: (1) It provides more detailed topological information in each contour. (2) The implementation in a table lookup method is easier and more efficient. (3) The complexity can be reduced to half because only one of each pair of neighboring regions needs to be traced. (4) Parallel processing is feasible. (5) The shapes of regions are well preserved.     

Observability and Forward–Backward Observability of Discrete-Time Nonlinear Systems

 In this paper we study the observability properties of nonlinear discrete-time systems. Two types of contributions are given. First we present observability criteria in terms of appropriate codistributions. For particular, but significant, classes of systems we provide criteria that require only a finite number of computations. Then we consider invertible systems (which includes discrete-time models obtained by sampling continuous-time systems) and prove that the weaker notion of forward–backward observability is equivalent to the stronger notion of (forward) observability. Date received: January 19, 2001. Date revised: May 14, 2002.     

A contour tracing and coding algorithm for generating 2D contour codes from 3D classified objects

In 3D image data sets generated by voxel-based classification, each voxel is marked with a specific class label. Voxels of the same class label can form 3D objects of extremely complex shape. Interactively drawn regions are usually represented by their 2D region borders. In order to combine automatically classified with interactively drawn regions, a contour tracing and coding algorithm for generating optimized 2D contours from 3D classified objects is presented. A special conversion algorithm allows a chain or a crack code representation. An application to medical images shows the method's necessity and usefulness in dealing with highly complex regions.     

基于前后向线性预测的时变参数估计方法研究

在基时间函数展开理论基础上,通过同时引入非平稳信号的前向线性预测和后向线性预测来估计模型的时变系数,提出了一种新的时变参数建模方法,有效地克服了现有方法对瞬时频率估计的滞后问题和无法准确估计初始时刻值的困难;仿真试验证明,在相同阶次和基函数维数条件下,该方法对非平稳信号瞬时频率的估计效果要优于现有的方法。     

容错调度算法中反向调度与正向调度性能分析

分析了软件容错模型中的BCE容错调度算法,针对该算法中的反向调度和正向调度两个过程,给出了RMB、DMB、EDFB 3种反向调度算法和RMF、EDFF 2种正向调度算法,指出了反向调度和正向调度相互协调的特性。将各种算法在BCE算法中进行模拟,结果表明EDFF正向调度算法能够与3种反向调度算法更好地协调,从而获得比RMF正向调度算法更高的调度性能。模拟结果表明,3种反向调度算法在BCE算法中的性能相近。得出RMB(或DMB)反向调度算法与EDFF正向调度算法的组合较适用于软件容错模型的结论。     

Monotonic Extensions of Petri Nets: Forward and Backward Search Revisited

In this paper, we revisit the forward and backward approaches to the verification of extensions of infinite state Petri Nets. As contributions, we propose an efficient data structure to represent infinite downward closed sets of markings and to compute symbolically the minimal coverability set of Petri Nets, we identify a subclass of Transfer Nets for which the forward approach generalizes and we propose a general strategy to use both the forward and the backward approach for the efficient verification of general Transfer Nets.     

Forward变换器的精确线性化控制

为了提高Forward变换器非线性系统的控制性能,采用了精确线性化控制方法。首先采用开关函数和开关周期平均算子建立适合微分几何方法的仿射非线性系统模型。从理论上证明了该模型满足系统精确线性化的条件。对非线性坐标变换后得到的线性系统,利用二次型最优控制策略推导出非线性状态反馈控制律。实验结果表明,系统具有良好的静态和动态性能,验证了该控制方法的有效性和正确性。     

A Logical Characterization of Forward and Backward Chaining in the Inverse Method

The inverse method is a generalization of resolution that can be applied to non-classical logics. We have recently shown how Andreoli’s focusing strategy can be adapted for the inverse method in linear logic. In this paper we introduce the notion of focusing bias for atoms and show that it gives rise to forward and backward chaining, generalizing both hyperresolution (forward) and SLD resolution (backward) on the Horn fragment. A key feature of our characterization is the structural, rather than purely operational, explanation for forward and backward chaining. A search procedure like the inverse method is thus able to perform both operations as appropriate, even simultaneously. We also present experimental results and an evaluation of the practical benefits of biased atoms for a number of examples from different problem domains. This work has been partially supported by the Office of Naval Research (ONR) under grant MURI N00014-04-1-0724 and by the National Science Foundation (NSF) under grant CCR-0306313. The first author was partially supported by a post-doctoral fellowship from INRIA-Futurs/école Polytechnique.