水面蒸发模型的进一步优化

水面蒸发量是水文水利计算、径流分析预测及水资源利用评价的主要内容,针对目前水面蒸发计算模型存在的问题,通过对水面蒸发机理的分析,采用最小二乘回归法,建立了由主要影响因子构成的修正系数函数对由相对次要因子构成的主体函数进行修正的基本模型,经比较,该模型具有较好的拟合精度。     

一一对应人脸自动识别身份验证的方法与应用

为实现人脸自动识别科技成果的广泛应用,本文规避现有的人脸自动识别的缺陷与不足,借鉴其成熟技术,提出在固定背景和光照的条件下,采用一对一比对,在＂合作用户＂领域中将人脸自动识别应用于身份验证的新方法。通过对人脸自动识别现有成熟技术、发展趋势和发展前景的论证,得出一一对应人脸自动识别身份验证的方法的技术路线完全可行,值得推广应用的结论。     

基于VBA实现Excel数据检验和比较

对Excel数据处理进行了阐述,介绍了如何利用VBA编程实现Excel工作表中的数据检验和比较,并给出了相应的代码。     

Using local transition probability models in Markov random fields for forest change detection

Change detection based on the comparison of independently classified images (i.e. post-classification comparison) is well-known to be negatively affected by classification errors of individual maps. Incorporating spatial-temporal contextual information in the classification helps to reduce the classification errors, thus improving change detection results. In this paper, spatial-temporal Markov Random Fields (MRF) models were used to integrate spatial-temporal information with spectral information for multi-temporal classification in an attempt to mitigate the impacts of classification errors on change detection. One important component in spatial-temporal MRF models is the specification of transition probabilities. Traditionally, a global transition probability model is used that assumes spatial stationarity of transition probabilities across an image scene, which may be invalid if areas have varying transition probabilities. By relaxing the stationarity assumption, we developed two local transition probability models to make the transition model locally adaptive to spatially varying transition probabilities. The first model called locally adjusted global transition model adapts to the local variation by multiplying a pixel-wise probability of change with the global transition model. The second model called pixel-wise transition model was developed as a fully local model based on the estimation of the pixel-wise joint probabilities. When applied to the forest change detection in Paraguay, the two local models showed significant improvements in the accuracy of identifying the change from forest to non-forest compared with traditional models. This indicates that the local transition probability models can present temporal information more accurately in change detection algorithms based on spatial-temporal classification of multi-temporal images. The comparison between the two local transition models showed that the fully local model better captured the spatial heterogeneity of the transition probabilities and achieved more stable and consistent results over different regions of a large image scene.     

各种网络拥塞控制机制的实现及比较

随着网络应用的迅猛发展,网络拥塞成为一个不可避免的问题,拥塞控制已经成为当前网络研究的重点。为了使网络得到充分的利用,研究者提出了多种拥塞控制机制,并且得到不断的改进。该文通过比较各种典型控制算法的优缺点,来对网络拥塞控制机制作个综合阐述。     

布尔表达式的化简与并行排序网络验证

为设计出能够验证并行排序网络正确性的有效工具,根据[0,1]原理和布尔函数的特点和性质,提出一种布尔表达式的化简算法,并根据此算法设计出验证工具.对[0,1]原理和布尔函数的特点和性质进行了讨论,指出有利于化简操作的性质.设计出的工具能够根据并行排序网络的参数显示网络图形、自动生成布尔表达式并实现化简验证,工具的输出有利于对排序网络的分析,也可以用于辅助排序网络的设计和优化.实验结果表明了该工具的有效性.     

CNC插补算法的VHDL建模设计与实现

数控机床加工的零件轮廓一般都可以用直线或圆弧去逼近。插补计算是数控系统根据输入的基本数据,描述工件轮廓的一种技术。文章针对硬件电路实现插补运算柔性差和精度低的缺陷,探索了一种以软IP实现插补运算的思路。并以较常用的逐点比较插补算法为例详细讨论了整个VHDL建模过程,作了比较全面的时序分析。最后在EDA6000实验开发平台验证了方案的可行性。该软IP插补具有升级容易、成本低廉的优点。     

岭南园林和江南园林美学特征的比较

本文从环境、功用、性格、艺术、文化五个方面,对岭南园林和江南园林美学特征进行了比较,提炼出二者不同的个性特点,提出了园林是文化的载体。     

Linear-space algorithms that build local alignments from fragments

This paper presents practical algorithms for building an alignment of two long sequences from a collection of alignment fragments, such as all occurrences of identical 5-tuples in each of two DNA sequences. We first combine a time-efficient algorithm developed by Galil and coworkers with a space-saving approach of Hirschberg to obtain a local alignment algorithm that uses0((M+N+F logN) logM) time and0(M+N) space to align sequences of lengthsM andN from a pool of F alignment fragments. Ideas of Huang and Miller are then employed to develop a time- and space-efficient algorithm that computesn best nonintersecting alignments for anyn>1. An example illustrates the utility of these methods.This work was supported in part by Grant RO1 LM05110 from the National Library of Medicine.     

用于全向无线电能传输的两种磁矢量控制方式对比分析

为实现全向无线电能传输,基于二维正交磁耦合机构提出了磁矢量旋转和磁矢量定向的控制方式。首先,采用基波等效分析法(fundamental harmonic approximation, FHA)设计使电压增益可调的LCC/S谐振补偿网络。其次,依据两种控制方式的机理给出激励电流的控制方法,从理论上对比二者传输效率差异同位置的关系。在上述基础上,由Ansys/Maxwell仿真得到两种控制方式的磁场时空特点,并基于空间互感分布的Matlab/Simulink仿真模型验证了两种控制方式的可行性。最后,搭建一台实验样机对理论分析进行验证,测得样机的传输效率的空间分布。仿真和实验结果表明：所提控制方式均可应用于正交磁耦合机构实现全向无线电能传输,磁矢量定向效率优于磁矢量旋转,平均效率提升了33.18%。