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86
Lowdensity paritycheck codes based on finite geometries: A rediscovery and new results
 IEEE Trans. Inform. Theory
, 2001
"... This paper presents a geometric approach to the construction of lowdensity paritycheck (LDPC) codes. Four classes of LDPC codes are constructed based on the lines and points of Euclidean and projective geometries over finite fields. Codes of these four classes have good minimum distances and thei ..."
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Cited by 119 (4 self)
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This paper presents a geometric approach to the construction of lowdensity paritycheck (LDPC) codes. Four classes of LDPC codes are constructed based on the lines and points of Euclidean and projective geometries over finite fields. Codes of these four classes have good minimum distances and their Tanner graphs have girth T. Finitegeometry LDPC codes can be decoded in various ways, ranging from low to high decoding complexity and from reasonably good to very good performance. They perform very well with iterative decoding. Furthermore, they can be put in either cyclic or quasicyclic form. Consequently, their encoding can be achieved in linear time and implemented with simple feedback shift registers. This advantage is not shared by other LDPC codes in general and is important in practice. Finitegeometry LDPC codes can be extended and shortened in various ways to obtain other good LDPC codes. Several techniques of extension and shortening are presented. Long extended finitegeometry LDPC codes have been constructed and they achieve a performance only a few tenths of a decibel away from the Shannon theoretical limit with iterative decoding.
The Quadratic Assignment Problem: A Survey and Recent Developments
 In Proceedings of the DIMACS Workshop on Quadratic Assignment Problems, volume 16 of DIMACS Series in Discrete Mathematics and Theoretical Computer Science
, 1994
"... . Quadratic Assignment Problems model many applications in diverse areas such as operations research, parallel and distributed computing, and combinatorial data analysis. In this paper we survey some of the most important techniques, applications, and methods regarding the quadratic assignment probl ..."
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Cited by 89 (16 self)
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. Quadratic Assignment Problems model many applications in diverse areas such as operations research, parallel and distributed computing, and combinatorial data analysis. In this paper we survey some of the most important techniques, applications, and methods regarding the quadratic assignment problem. We focus our attention on recent developments. 1. Introduction Given a set N = f1; 2; : : : ; ng and n \Theta n matrices F = (f ij ) and D = (d kl ), the quadratic assignment problem (QAP) can be stated as follows: min p2\Pi N n X i=1 n X j=1 f ij d p(i)p(j) + n X i=1 c ip(i) ; where \Pi N is the set of all permutations of N . One of the major applications of the QAP is in location theory where the matrix F = (f ij ) is the flow matrix, i.e. f ij is the flow of materials from facility i to facility j, and D = (d kl ) is the distance matrix, i.e. d kl represents the distance from location k to location l [62, 67, 137]. The cost of simultaneously assigning facility i to locat...
An automated framework for structural testdata generation
 Proceedings of the International Conference on Automated Software Engineering; IEEE
, 1998
"... Structural testing criteria are mandated in many software development standards and guidelines. The process of generating testdata to achieve 100 % coverage of a given structural coverage metric is labour intensive and expensive. This paper presents an approach to automate the generation of such te ..."
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Cited by 72 (12 self)
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Structural testing criteria are mandated in many software development standards and guidelines. The process of generating testdata to achieve 100 % coverage of a given structural coverage metric is labour intensive and expensive. This paper presents an approach to automate the generation of such testdata. The testdata generation is based on the application of a dynamic optimisationbased search for the required testdata. The same approach can be be generalised to solve other testdata generation problems. Three such applications are discussed { boundary value analysis, assertion/runtime exception testing and component reuse testing. Aprototype toolset has been developed to facilitate the automatic generation of testdata for these structural testing problems. The results of preliminary experiments using this technique and the prototype toolset are presented and show the e ciency and e ectiveness of this approach. 1
On Geometric Assembly Planning
, 1992
"... This dissertation addresses the problem of generating feasible assembly sequences for a mechanical product from a geometric model of the product. An operation specifies a motion to bring two subassemblies together to make a larger subassembly. An assembly sequence is a sequence of operations that co ..."
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Cited by 71 (12 self)
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This dissertation addresses the problem of generating feasible assembly sequences for a mechanical product from a geometric model of the product. An operation specifies a motion to bring two subassemblies together to make a larger subassembly. An assembly sequence is a sequence of operations that construct the product from the individual parts. I introduce the nondirectional blocking graph, a succinct characterization of the blocking relationships between parts in an assembly. I describe efficient algorithms to identify removable subassemblies by constructing and analyzing the NDBG. For an assembly A of n parts and m partpart contacts equivalent to k contact points, a subassembly that can translate a small distance from the rest of A can be identified in O(mk 2 ) time. When rotations are allowed as well, the time bound is O(mk 5 ). Both algorithms are extended to find connected subassemblies in the same time bounds. All free subassemblies can be identified in outputdependent ...
Space Variant Image Processing
, 1993
"... This paper describes a graphbased approach to image processing, intended for use with images obtained from sensors having space variant sampling grids. The connectivity graph (CG) is presented as a fundamental framework for posing image operations in any kind of space variant sensor. Partially moti ..."
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Cited by 40 (9 self)
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This paper describes a graphbased approach to image processing, intended for use with images obtained from sensors having space variant sampling grids. The connectivity graph (CG) is presented as a fundamental framework for posing image operations in any kind of space variant sensor. Partially motivated by the observation that human vision is strongly space variant, a number of research groups have been experimenting with space variant sensors. Such systems cover wide solid angles yet maintain high acuity in their central regions. Implementation of space variant systems pose at least two outstanding problems. First, such a system must be active, in order to utilize its high acuity region; second, there are significant image processing problems introduced by the nonuniform pixel size, shape and connectivity. Familiar image processing operations such as connected components, convolution, template matching, and even image translation, take on new and different forms when defined on spac...
Low density parity check codes based on finite geometries: A rediscovery and new results
 IEEE Trans. Inform. Theory
, 2001
"... This paper presents a geometric approach to the construction of low density parity check (LDPC) codes. Four classes of LDPC codes are constructed based on the lines and points of Euclidean and projective geometries over finite fields. Codes of these four classes have good minimum distances and thei ..."
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Cited by 35 (11 self)
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This paper presents a geometric approach to the construction of low density parity check (LDPC) codes. Four classes of LDPC codes are constructed based on the lines and points of Euclidean and projective geometries over finite fields. Codes of these four classes have good minimum distances and their Tanner graphs have girth 6. Finite geometry LDPC codes can be decoded in various ways, ranging from low to high decoding complexity and from reasonably good to very good performance. They perform very well with iterative decoding. Furthermore, they can be put in either cyclic or quasicyclic form. Consequently, their encoding can be achieved in linear time and implemented with simple feedback shift registers. This advantage is not shared by other LDPC codes in general and is important in practice. Finite geometry LDPC codes can be extended and shortened in various ways to obtain other good LDPC codes. Several techniques of extension and shortening are presented. Long extended finite geometry LDPC codes have been constructed and they achieve a performance only a few tenths of a dB away from the Shannon theoretical limit with iterative decoding.
OnLine Software Version Change
, 1994
"... what constitutes an "acceptable" behavior of such a process. We capture this notion in our definition of the validity of an online change. We define an online change to be valid if some time after the change, the process reaches a reachable state of the new program version. Thus, validity ensures ..."
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Cited by 29 (0 self)
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what constitutes an "acceptable" behavior of such a process. We capture this notion in our definition of the validity of an online change. We define an online change to be valid if some time after the change, the process reaches a reachable state of the new program version. Thus, validity ensures that following a change, the process starts behaving like the new version of the program after a "transition period". We first consider validity of online changes to programs written in sequential procedure based languages. For this purpose, a very simple model in which procedures and functions are not allowed is first considered. State is modelled as a mapping from variable names to values. For this model, we show that it is undecidable to find whether or not a given online change is valid. This result has important consequences. It means that computable necessary and sufficient conditions for validity of change can not be obtained. Undecidability in this simple model also
Enumerating the NonIsomorphic Assembly Configurations of Modular Robotic Systems
 the International Journal of Robotics Research
"... A "modular" robotic system consists of joint and link modules that can be assembled in a variety of configurations to meet different or changing task requirements. However, due to typical symmetries in module design, different assembly configurations may lead to robotic structures which are kinemati ..."
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Cited by 26 (1 self)
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A "modular" robotic system consists of joint and link modules that can be assembled in a variety of configurations to meet different or changing task requirements. However, due to typical symmetries in module design, different assembly configurations may lead to robotic structures which are kinematically identical, or isomorphic. This paper considers how to enumerate the nonisomorphic assembly configurations of a modular robotic system. We introduce an Assembly Incidence Matrix (AIM) to represent a modular robot assembly configuration. Then we use symmetries of the module geometry and graph isomorphisms to define an equivalence relation on the AIMs. Equivalent AIMs represent isomorphic robot assembly configurations. Based on this equivalence relation, we propose an algorithm to generate nonisomorphic assembly configurations of an nlink treelike robot with different joint and link module types. Examples demonstrate that this method is a significant improvement over a brute force enu...
Evaluating Inlining Techniques
 Computer Languages
, 1998
"... this report is on the comparison of inlining policies and techniques. First, we formalize the power and flexibility of inlining policies (see Section 3). We then identify policies based on the version of the inlined procedure that is used, as described below ..."
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Cited by 17 (0 self)
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this report is on the comparison of inlining policies and techniques. First, we formalize the power and flexibility of inlining policies (see Section 3). We then identify policies based on the version of the inlined procedure that is used, as described below
On Supervisory Policies that Enforce Liveness in Completely Controlled Petri Nets with Directed CutPlaces and CutTransitions
 IEEE TRANSACTIONS ON AUTOMATIC CONTROL
, 1999
"... The process of synthesizing a supervisory policy that enforces liveness in a Petri net (PN) [4, 3] where each transition can be prevented from firing by an external agent, can be computationally burdensome in general [7]. In this paper we consider PNs that have a directed cutplace, or, a cuttransi ..."
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Cited by 16 (6 self)
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The process of synthesizing a supervisory policy that enforces liveness in a Petri net (PN) [4, 3] where each transition can be prevented from firing by an external agent, can be computationally burdensome in general [7]. In this paper we consider PNs that have a directed cutplace, or, a cuttransition. A place (transition) in a connected PN is said to be a cutplace (cuttransition) if its removal will result in two disconnected, componentPNs. A cutplace is said to be a directed cutplace, if, in the original PN all arcs into this cutplace emanate from transitions in only one of the two disconnected, componentPNs. We show there is a supervisory policy that enforces liveness in the original PN if and only if similar policies exist for two PNs derived from the disconnected components obtained after the removal of the directed cutplace (cuttransition). The utility of this observation in alleviating the computational burden of policy synthesis is illustrated via example.