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41.
R.?CliffordEmail author C.?Iliopoulos 《Soft Computing - A Fusion of Foundations, Methodologies and Applications》2004,8(9):597-603
Approximate pattern matching algorithms have become an important tool in computer assisted music analysis and information retrieval. The number of different problem formulations has greatly expanded in recent years, not least because of the subjective nature of measuring musical similarity. From an algorithmic perspective, the complexity of each problem depends crucially on the exact definition of the difference between two strings. We present an overview of advances in approximate string matching in this field focusing on new measures of approximation. 相似文献
42.
关系数据库中近似重复记录的识别 总被引:5,自引:0,他引:5
数据清理转换是数据仓库中的一个重要研究领域,其技术难点之一是重复记录的识别。介绍了与重复记录识别相关的字符串匹配方法,详细讨论了识别重复记录的分区式优先队列算法、多趟邻近排序法以及邻近连接法,最后给出了实验结果。 相似文献
43.
In this paper, we consider the problem of decentralized control of a collection of heterogeneous vehicles trying to maintain a rigid formation. In a rigid formation of vehicles, the separation distance between any pair of vehicles does not change throughout their motion and equals a pre-specified value that defines the formation. In each formation, there is a set of reference vehicles and a set of following vehicles. A reference vehicle may not be influenced by the motion of the following vehicle, but the motion of the following vehicle is influenced by the motion of the reference vehicle. Since we will be primarily dealing with translational maneuvers of the formation, we will consider formations where there is only one reference vehicle whose motion specifies the desired motion for all the vehicles in the formation. Each following vehicle attempts to maintain a specified constant safe distance from its adjacent vehicles in the collection. We call a vehicle B adjacent to a vehicle A if the relative position of vehicle B is known to vehicle A either by communication or by sensing. We only consider information flow graphs that are undirected when restricted to the set of following vehicles, i.e., graphs where a following vehicle A is adjacent to a following vehicle B if and only if the following vehicle B is adjacent to the following vehicle A. We model each vehicle as a point mass of one unit with two types of forces act on each vehicle - a controlled force, which is the output of an actuation system and a disturbing force over which there is no control. The actuation system is assumed to be linear and time invariant, and may be representable by a rational and strictly proper transfer function. The input to the control system of a vehicle in the formation is based on the error in maintaining the desired separation from its adjacent vehicles and the output of the control system is a command to the actuator.An earlier result showed that spacing errors due to disturbances amplify in a collection of identical vehicles with identically structured linear controllers if the reference vehicle information is not available to Ω(n) (A function f(n) is Ω(g(n)) if there is a constant c > 0 and a N > 0 such that ∣f(n)∣ > c∣g(n)∣ for all n > N.) vehicles, n being the size of the collection [1]. From the viewpoint of tolerance to communication failures, it is therefore necessary that there be at least two vehicles in the formation that are adjacent to Ω(n) vehicles in the formation. In this paper, we consider a broad class of heterogeneously structured controllers defined by a pre-specified bound, say Bc > 0 as follows: the allowable controller in conjunction with the actuation systems on-board any vehicle will produce a force no greater than Bc in response to a constant input to the control system. If this class of controllers were to be employed with the aforesaid undirected information flow graphs, we show that there is a critical size of the formation beyond which the motion of the vehicles in the formation will be unstable. This result shows the inability to scale such controllers for maintenance of rigid formations in conjunction with undirected information flow graphs. 相似文献
44.
The frequent string mining problem is to find all substrings of a collection of string databases which satisfy database specific
minimum and maximum frequency constraints. Our contribution improves the existing linear-time algorithm for this problem in
such a way that the peak memory consumption is a constant factor of the size of the largest database of strings. We show how
the results for each database can be stored implicitly in space proportional to the size of the database, making it possible
to traverse the results in lexicographical order. Furthermore, we present a linear-time algorithm which calculates the intersection
of the results of different databases. This algorithm is based on an algorithm to merge two suffix arrays, and our modification
allows us to also calculate the LCP table of the resulting suffix array during the merging. 相似文献
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46.
在线切割加工过程中,由于放电通道内电极丝受到张紧力、放电合力、流体阻尼等作用,电极丝必然会产生挠曲变形和振动现象,严重影响线切割加工的效率、精度和稳定性,主要体现在工件加工精度、表面粗糙和切口宽度。从分析放电通道内的电极丝受力情况出发,将放电合力进行傅里叶变换,结合弦振动非线性偏微分方程,建立三维多脉冲放电的电极丝振动模型,运用COMSOL仿真软件,求解电极丝振动振幅数值解。在此基础上,分析各个因素对电极丝振动的影响规律,已获得减少电极丝振动振幅的实践加工方法,为实际加工过程提供理论指导依据。 相似文献
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49.
本文分析了模糊字符串几种类型和它的表示方法,并给出模糊匹配的算法及C语言的源程序,同时也指出了在文枉编辑器的应用例子。 相似文献
50.
潘先国 《江汉石油职工大学学报》2014,(4):58-61
坪北油田由于地层水敏、地层负压亏空的限制,常用的水力冲砂法易造成油层污染。机械捞砂作业与水力冲砂法相比具有两大优势:一是无洗井冲砂液,有利于油层保护,能满足特殊作业的需要;二是工艺结构简单,使用维护方便,成本低。为提高坪北油田机械捞砂作业的有效率,借助于对"机械捞砂作业管柱设计数学模型"的研究,设计出捞砂管柱及捞砂趟数,并应用于生产实践,收到了良好的效果,为完善油井清砂提供了新的工艺方法。 相似文献