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21.
目的:无线传感器网络发展迅速,但传感器的高能耗问题成为制约其发展的主要瓶颈,高效节能的路由协议设计成为研究热点。方法:针对目前无线传感器网络常用的LEACH路由协议存在的簇首能耗过分集中、簇首分布不均衡问题,提出了改进的路由协议EEACRA,在总结、分析LEACH路由协议现有问题的基础上,给出了EEACRA路由协议的簇首选取门限值、簇首位置调整算法和基于能量代价最小的簇间多跳路由算法的实现方法,同时给出了具体的实现EEACRA协议的工作流程和关键算法。在MATLAB环境下对LEACH路由协议和EEACRA路由协议进行了仿真,对比了不同能耗降低措施对网络能耗降低的贡献。结果:仿真结果表明EEACRA路由协议的网络稳定期较LEACH路由协议有较大的改善。结论:证明了改进的路由协议EEACRA可以有效地提高网络的稳定期。 相似文献
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为了提高对混合架构下ORACLE数据的挖掘和查找速度,提出一种基于频繁项目集关联规则挖掘的数据快速查找方法。构建ORACLE数据的内部关联属性映射关系模型,在异质网络混合构架模式下,采用Graph OLAP数据仓库模型进行数据库检索的关系维度表,提取表达ORACLE数据属性信息的特征参量,通过同态标签检索方法,实现对目标数据的快速查找定位。仿真结果表明,采用该方法进行ORACLE数据查找的查准率和查全率较高,计算速度较快,性能优于传统方法。 相似文献
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传统的以水为装饰的方法形式比较单一,缺乏创新性的现状,因此提出了一种基于ARM架构,结合了人体传感、无线传输等功能的数字图形水幕系统,能够精确控制电磁水阀开/闭合,实现了以水为媒介的图形、文字的展示;同时,在系统中开发了一种自由落体图像补偿算法,创建了图像补偿表,通过对原始图像的补偿可在系统人眼感兴趣的区域很好展示所需的图形及文字;在实验中可看出系统在1.26 m×1.26 m的显示区域内对64×64像素的图形进行补偿时达到了较好的效果;该系统综合考虑了性能、成本等因素,具有很强的创新性和实用价值。 相似文献
25.
Efficient and flexible memory architecture to alleviate data and context bandwidth bottlenecks of coarse-grained reconfigurable arrays 总被引:1,自引:0,他引:1
The computational capability of a coarse-grained reconfigurable array(CGRA)can be significantly restrained due to data and context memory bandwidth bottlenecks.Traditionally,two methods have been used to resolve this problem.One method loads the context into the CGRA at run time.This method occupies very small on-chip memory but induces very large latency,which leads to low computational efficiency.The other method adopts a multi-context structure.This method loads the context into the on-chip context memory at the boot phase.Broadcasting the pointer of a set of contexts changes the hardware configuration on a cycle-by-cycle basis.The size of the context memory induces a large area overhead in multi-context structures,which results in major restrictions on application complexity.This paper proposes a Predictable Context Cache(PCC)architecture to address the above context issues by buffering the context inside a CGRA.In this architecture,context is dynamically transferred into the CGRA.Utilizing a PCC significantly reduces the on-chip context memory and the complexity of the applications running on the CGRA is no longer restricted by the size of the on-chip context memory.Data preloading is the most frequently used approach to hide input data latency and speed up the data transmission process for the data bandwidth issue.Rather than fundamentally reducing the amount of input data,the transferred data and computations are processed in parallel.However,the data preloading method cannot work efficiently because data transmission becomes the critical path as the reconfigurable array scale increases.This paper also presents a Hierarchical Data Memory(HDM)architecture as a solution to the efficiency problem.In this architecture,high internal bandwidth is provided to buffer both reused input data and intermediate data.The HDM architecture relieves the external memory from the data transfer burden so that the performance is significantly improved.As a result of using PCC and HDM,experiments running mainstream video decoding programs achieved performance improvements of 13.57%–19.48%when there was a reasonable memory size.Therefore,1080p@35.7fps for H.264high profile video decoding can be achieved on PCC and HDM architecture when utilizing a 200 MHz working frequency.Further,the size of the on-chip context memory no longer restricted complex applications,which were efficiently executed on the PCC and HDM architecture. 相似文献
26.
Indirect learning architecture (ILA) for digital pre-distortion (DPD) is commonly used to linearize power amplifiers (PA). To the author’s best knowledge, most of the DPD results in the literature obtain the matrix form of the least-square solution in order to get the DPD coefficients numerically. There exists no explicit closed-form for these coefficients that can be used as plug-and-play in simulations, or used for further closed-form analysis of important measures such as signal-to-noise ratio (SNR) and mean square error (MSE), bit-error rate (BER), …etc. In this paper, we analyze the ILA-DPD system for general memory-polynomial PA models. We provide a closed-form solution for the DPD coefficients. We first present the analytical methodology for deriving the mathematical expressions for each DPD coefficient and then introduce an open-access code that generates the DPD coefficients in symbolic form that is used to mathematically model the DPD. We consider case studies for PA and show that the analytical DPD solution matches the Monte Carlo simulations. Moreover, we also provide a closed-form solution for the iterative adaptive ILA-DPD. Our analysis shows that in the case of a large training block length the non-iterative DPD achieves approximately the same performance as an iterative DPD with a shorter training block length. System impairments are also considered, e.g. the thermal noise and the quantization noise in analog–digital conversion (ADC). We derive the normalized mean square error (NMSE) for the transmit chain in the presence of these impairments. The NMSE expression is verified through numerical simulations. 相似文献
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28.
Reliability is a major concern in the design of large disk arrays. In this paper, we examine the effect of encountering more failures than that for which the RAID array was initially designed. Erasure codes are incorporated to enable system recovery from a specified number of disk erasures, and strive beyond that threshold to recover the system as frequently, and as thoroughly, as is possible. Erasure codes for tolerating two disk failures are examined. For these double erasure codes, we establish a correspondence between system operation and acyclicity of its graph model. For the most compact double erasure code, the full 2-code, this underlies an efficient algorithm for the computation of system operation probability (all disks operating or recoverable).When the system has failed, some disks are nonetheless recoverable. We extend the graph model to determine the probability that d disks have failed, a of which are recoverable by solving one linear equation, b of which are further recoverable by solving systems of linear equations, and d−a−b of which cannot be recovered. These statistics are efficiently calculated for the full 2-code by developing a three variable ordinary generating function whose coefficients give the specified values. Finally, examples are given to illustrate the probability that an individual disk can be recovered, even when the system is in a failed state. 相似文献
29.
宁波城市设计的若干思考与建议 总被引:1,自引:0,他引:1
张柳燕 《宁波大学学报(理工版)》2004,17(2):166-169
通过探讨城市设计概念的形成过程和历史积淀,阐明其在城市建设中的意义,并运用城市设计的理论与分析方法,针对目前宁波城市大规模的规划、设计、改造现象,提出若干思考与建议. 相似文献
30.
Anna Finne Ann‐Christine Albertsson 《Journal of polymer science. Part A, Polymer chemistry》2003,41(9):1296-1305
Hydrogels of poly(1,5‐dioxepan‐2‐one) and hydrogels of block copolymers of poly(1,5‐dioxepan‐2‐one) and poly(L ‐lactide) were synthesized. Both star‐shaped polymers and linear polymers were polymerized with ring‐opening polymerization and crosslinked in situ with a tetrafunctional acid chloride (1,2,3,4‐cyclopentane tetracarboxylic acid chloride) or a difunctional acid chloride (succinyl chloride). Different network architectures were synthesized in this way. The initial monomer concentrations and the molecular weights of the macromonomers were also altered. The networks were characterized with 1H NMR and differential scanning calorimetry, and the swelling abilities of the different hydrogels were investigated in water and dichloromethane. The ratio of the monomer to the crosslinking agent was assessed by the quantification of the signal intensities in the 1H NMR spectra of the swelled network and agreed with the theoretical crosslinking density. Both the homopolymers of 1,5‐dioxepan‐2‐one and the copolymers of 1,5‐dioxepan‐2‐one and L ‐lactide swelled to a high degree in water. The swelling properties of the materials could be varied over a broad range by changes in the architecture, molecular weight, and content of the precursor in the network. Star‐shaped poly(1,5‐dioxepan‐2‐one) crosslinked with a difunctional acid chloride had the highest degree of swelling among the different homopolymer hydrogels. This network also had the lowest glass‐transition temperature because of the flexible units in the structure. The same trends found for the homopolymer hydrogels were also seen in the hydrogels with block copolymers. The hydrogels swelled enormously in dichloromethane, and as in water, the star‐shaped copolymer crosslinked with a difunctional acid chloride had the highest degree of swelling. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1296–1305, 2003 相似文献