Rajesh Prasad

Fracture behaviour of aluminium alloy 2219–T87 welded plates

Abstract Aluminium alloy AA 2219 is used in aerospace applications because of its good weldability, stress corrosion resistance, and mechanical properties over a wide temperature range of + 250 to - 250 ° C. The elastic-plastic fracture toughness JIc has been measured on 7.4 mm thickness autogenous alternating current tungsten inert gas welded plates of 2219-T87 alloy in the as welded condition, using a single specimen technique. The present paper elucidates the variation of JIc across the weld joint. The toughness was evaluated at three different locations across the weld, namely, in the weld, fusion boundary, and heat affected zones, and compared with parent metal toughness. It was found that the fracture toughness across the weld was higher than the parent metal toughness. The fusion boundary had the lowest toughness among the three zones across the weld joint. The variation of toughness among the different zones is explained with reference to fractographic observations.

Efficient indexing techniques for record matching and deduplication

Record matching works on large sets of data, which may be either from single database or several databases. As size of database increases very rapidly, demand of matching process becomes too high. So, there is demand to minimise the number of matching pair records, time and cost in comparing records using efficient matching techniques. Recent researches have been done on record matching by number of researchers using various indexing techniques but as such they are not effective. Suffix array SA and q-gram are used indexing technique, but they lack somewhere in computation. This paper proposes two new indexing techniques: inverse suffix array ISA and Burrows-Wheeler transformation BWT to improve the performance of record matching process. The approach ISA can handle the multiple keywords simultaneously. We compare the performance of the proposed techniques with existing suffix array and q-gram indexing techniques and found that the new techniques are better than the earlier techniques.

A new parameterized string matching algorithm by combining bit-parallelism and suffix automata

In the parameterized string matching, a given pattern P is said to match with a substring t of the text T, if there exist a bijection from the symbols of P to the symbols of t. This problem has an important application in software maintenance, where we wish to find the equivalency between two sections of codes. Two sections of codes are said to be equivalent, if one can be transformed into the other by renaming identifiers and variables only. Crochemore et al., 1994, has developed an algorithm (BDM) for exact string matching problem using suffix automata. Kimmo Fredriksson et al., 2006, has developed parameterized bit-parallel algorithm (parameterized shift-or) and parameterized BDM (PBDM). Parameterized shift-or (PSO) simulates finite automata in their nondeterministic form. The main drawback of PSO is: it is unable to skip text characters while matching forward. In this paper, we develop a new algorithm for parameterized string matching problem. This algorithm is based upon both suffix automata and bit parallelism concepts. This algorithm is faster than PBDM, since it processes the suffix automata in their non-deterministic form.

Parameterized shift-and string matching algorithm using super alphabet

In the parameterized string matching, a given pattern P is said to match with a sub-string t of the text T, if there exist a bijection from the symbols of P to the symbols of t. This problem has an important application in software maintenance where it is required to find equivalency between two sections of codes. Two sections of codes are said to be equivalent if one can be transformed into the other by renaming identifiers and variables only. In this paper, we extend shift-and string matching algorithm to find all such occurrences of P in T. The new algorithm is named as parameterized shift-and (PSA) string matching algorithm. We further extend PSA by using the concept of super alphabets. Implementation results show that by using a super alphabet of size s, the algorithm (PSA) is speeded-up by a factor of s, where s is size of the super alphabet (i.e. s is the number of characters processed simultaneously). We also show the performance of super alphabet PSA with respect to duplicity present in the code. However these algorithms are applicable only when pattern length (m) is less than or equal to word length (w) of computer used (i.e. m les w).

Multi-patterns parameterised matching with application to computational biology

In the multi-pattern parameterised string matching problem, we are given a text T and pattern set P = {p

A fast bit-parallel multi-patterns string matching algorithm for biological sequences

The problem of searching occurrences of a pattern P[0...m-1] in the text T[0...n-1>with m ≤ n, where the symbols of P and T are drawn from some alphabet Σ of size σ, is called exact string matching problem. In the present day, pattern matching is a powerful tool in locating nucleotide or amino acid sequence patterns in the biological sequence database. The problem of searching a set of patterns P0, P1, P2...Pr-1, r ≥ 1, in the given text T is called multi-pattern string matching problem. The multi-patterns string matching problem has been previously solved by efficient bit-parallel strings matching algorithms: shift-or and BNDM. Many other types of algorithms also exist for the same purpose, but bit-parallelism has been shown to be very efficient than the others. In this paper, we extend BNDM algorithm with q-gram (B. Durian et al., 2008) for multiple patterns, where each multi-patterns are any DNA patterns. We assume that each pattern is of equal size m and total length of pattern is less than or equal to word length (w) of computer used. Since BNDM algorithm has been shown to be faster than any other bit-parallel string matching algorithm (G. Navarro, 2000), therefore, we compare the performance of multi-patterns q-gram BNDM algorithm with existing BNDM algorithm for different value of q and number of patterns (r).

Fast parameterized word matching on compressed text

Two strings P[1...m] and T[1...n] with m ≤ n, are said to be parameterized match (p-match), if one can be transformed into the other via some bijective mapping. It is mainly used in software maintenance, plagiarism detection and detecting isomorphism in a graph. In the compressed parameterized matching problem, our task is to find all the parameterized occurrences of a pattern in the compressed text, without decompressing it. Compressing the text before matching reduces the size and minimizes the matching time also. In this paper, we mainly focus on the parameterized word matching on the compressed text, where both patterns and text are compressed before actual matching is performed. For compressing the pattern and text, we use efficient compression code: Word Based Tagged Code (WBTC). Experimental results show that our algorithm is up to three times faster than the search on uncompressed text.

An offensive algorithm for multi-pattern parameterized string matching

Finding a pattern P[0...m-1] in a large body of text T[0...n-1], m≤n, is called pattern matching. One of its variation is parameterized string matching. Two strings are said to parameterized match, if one can be transformed into other via some bijective mapping. The parameterized matching has important applications in software maintenance and plagiarism detection. In this paper, we propose a new algorithm for multi-pattern parameterized string matching problem. This is an extension of quick multiple matching algorithm for exact string matching. Experimental results show that the new algorithm is very fast in practice.

Study of Bit-Parallel Approximate Parameterized String Matching Algorithms

In the parameterized string matching, a given pattern P is said to match with a substring t of the text T, if there exist a bijection from the symbols of P to the symbols of t. This problem has an important application insoftware maintenance, where we wish to find the equivalency between two sections of codes. Two sections of codes are said to be equivalent, if one can be transformed into the other by renaming identifiers and variables. In the approximate parameterized matching, a given pattern P matches the given substring t of the text T with k ≥ 0 errors, if P can be transformed into t with at most k modifications (insertion, deletion, replacement). In this paper, we extend Myers Bit-Parallel algorithm and Approximate String Matching by using Bit-Parallel NFA (both for approximate matching), for parameterized string matching problem. These extended algorithms are known as PAMA and PABPA respectively. Theoretically, PAMA algorithm is faster than PABPA algorithm. The above algorithms are applicable only when pattern length (m) is less than word length (w) of computer used (i.e. m ≤ w).

An Efficient Word Searching Algorithm through Splitting and Hashing the Offline Text

Word matching problem is to find all the occurrences of a pattern P[0…m-1] in the text T[0…n-1], where P neither contains any white space nor preceded and followed by space. In this paper, we assume that our text is offline. Ibrahiem et al. in 2008 have proposed an algorithm (WSA) for solving the word matching problem by splitting the offline text into number of tables in the preprocessing phase. The main drawback of this algorithm was: after splitting the text into a number of tables, they search each occurrence of the pattern by the brute force manner in each table. In this paper, we improved the algorithm by using an efficient hash function SDBM proposed by R. J. Enbody et al. in 1988. In this technique, after splitting the text into number of tables, we match the hash value of the pattern P with the hash values of the words of same length in the text T. This algorithm is called as modified word searching algorithm (MWSA). Experimental results show that MWSA algorithm is much faster than the previously proposed WSA algorithm.