Indexing with coded deltas—a data compaction technique

The paper describes the coded delta scheme, which is one of the methods used by the Census Research Unit, University of Durham, for compacting the 1971 U.K. census data. It evaluates the merits and limitations of the technique in relation to the characteristics of the data set and other techniques available for compact encoding of numeric and string data.     

富县浅层水平井中生产管柱下入可行性分析

富县区块储层埋藏浅、渗透率低,直井开发效果差,需用水平井技术提高开发效果,而在浅层水平井中生产管柱与套管壁之间摩擦阻力大,因此存在作业风险。通过应用有限元方法建立了能描述生产管柱与套管壁之间非线性随机接触问题的方程,求解该方程可以得出在水平井眼中生产管柱的变形量、摩擦阻力和管柱载荷。通过编程计算表明,在富县的浅层水平井中生产管柱能通过自重下入,但井下摩擦阻力大,井口悬重低。     

A framework for condensation-based anonymization of string data

In recent years, privacy preserving data mining has become an important problem because of the large amount of personal data which is tracked by many business applications. An important method for privacy preserving data mining is the method of condensation. This method is often used in the case of multi-dimensional data in which pseudo-data is generated to mask the true values of the records. However, these methods are not easily applicable to the case of string data, since they require the use of multi-dimensional statistics in order to generate the pseudo-data. String data are especially important in the privacy preserving data-mining domain because most DNA and biological data are coded as strings. In this article, we will discuss a new method for privacy preserving mining of string data with the use of simple template-based models. The template-based model turns out to be effective in practice, and preserves important statistical characteristics of the strings such as intra-record distances. We will explore the behavior in the context of a classification application, and show that the accuracy of the application is not affected significantly by the anonymization process. This article is an extended version of the conference version of the paper presented at the SIAM Conference on Data Mining, 2007 Aggarwal and Yu (2007). Available at .     

An algorithmic analysis of DNA structure

Bilinearity, complementarity and antiparallelism of the double stranded DNA structure are proved, in a general and abstract setting, as requirements of an efficient duplication algorithm for ‘mobile strings’.     

字符串的子串删除问题

本文探讨了Codeforces Round#452 (Div. 2) F题的两种做法。     

A reference string sampling method with dynamically changing parameters

Wittneben proposed a technique which determines the structural characteristics of a program's memory referencing behavior based only on a sampling of the complete reference string. This method controls the cost of the measurement by adjusting the sampling rate while simultaneously attempting to determine accurately the referencing behavior as reflected in its working set measurements. Wittneben's method is controlled by parameters with statically determined values. The aim of this paper is to present a modified sampling method in which sampling parameters are updated dynamically according to the actual program referencing behavior. The updating process is controlled by the phase-transition structure of a program. Furthermore, working set measurements of the program are based on modified principles which take into account the most probable sources of errors made during the sampling process. Experiments conducted with synthetic and real reference strings seem to demonstrate the superiority of the modified method in comparison with the technique originally formulated by Wittneben.     

A New Efficient Algorithm for Computing the Longest Common Subsequence

The Longest Common Subsequence (LCS) problem is a classic and well-studied problem in computer science. The LCS problem is a common task in DNA sequence analysis with many applications to genetics and molecular biology. In this paper, we present a new and efficient algorithm for solving the LCS problem for two strings. Our algorithm runs in O(ℛlog log n+n) time, where ℛ is the total number of ordered pairs of positions at which the two strings match. Preliminary version appeared in [24]. C.S. Iliopoulos is supported by EPSRC and Royal Society grants. M.S. Rahman is supported by the Commonwealth Scholarship Commission in the UK under the Commonwealth Scholarship and Fellowship Plan (CSFP) and is on Leave from Department of CSE, BUET, Dhaka-1000, Bangladesh.     

Approximate string matching with address bit errors

A string S∈Σ^m$S\in {\Sigma }^m$ can be viewed as a set of pairs S={(_σi,i):i∈{0,…,m−1}}$S=\{({\sigma }_i,i):i\in \{0,\dots ,m-1\}\}$. We consider approximate pattern matching problems arising from the setting where errors are introduced to the location component (i$i$), rather than the more traditional setting, where errors are introduced into the content itself (_σi${\sigma }_i$). In this paper, we consider the case where bits of i$i$ may be erroneously flipped, either in a consistent or transient manner. We formally define the corresponding approximate pattern matching problems, and provide efficient algorithms for their resolution, while introducing some novel techniques.     

Working set measurements based on sampled reference string information

The development of new memory technologies combined with the pressures for ever larger, database software systems will continue to make a multi-level memory an attractive and cost-effective system organization. The performance of a process executing in a system with such a memory hierarchy depends on both the memory referencing behavior of the process and the policy used to control the contents of each memory level. The direct observation of this referencing behavior by capturing every memory reference involves a substantial overhead and can not be applied to ‘time-critical’ systems because the measurement radically perturbs the normal operation of the system. This paper reports on the development and testing of a technique which determines the structural characteristics of a process's memory referencing behavior based only on a sampling of the complete reference string. This method controls the cost of the measurement by adjusting the sampling rate while simultaneously attempting to accurately determine the referencing behavior as reflected in its working set measurements. The results presented in this paper are based on the use of a set of successively more realistic synthetic behavior models as well as on actual reference strings.     

Sequential vs. parallel complexity in simple gene assembly

We investigate some differences between the general intramolecular model for gene assembly and its restricted simple model. Although both models satisfactorily sort all current experimental data, we show that the general model offers assembly strategies for a given string that vary in both assembly length and the operations used, while the simple model will always use the same number of each type of operation to sort a gene. When simple operations are applied in parallel this is given a new twist. We prove that for any n≥1$n\ge 1$, there exists a string having maximally parallel assemblies of any length between n$n$ and 2n$2n$.