10979198
Weakly Hamiltonian-connected ordinary multipartite tournaments
Abstract We characterize weakly Hamiltonian-connected ordinary multipartite tournaments. Our result generalizes such a characterization for tournaments by Thomassen and implies a polynomial algorithm to decide the existence of a Hamiltonian path connecting two given vertices in an ordinary multipartite tournament and finds one, if it exists.
4789976
In-Tournament Digraphs
Abstract In this paper we introduce a generalization of digraphs that are locally tournaments (and hence of tournaments). This is the class of in-tournament digraphs-the set of predecessors of every vertex induces a tournament. We show that many properties of local tournament digraphs can be extended even to in-tournament digraphs. For instance, any strongly connected in-tournament digraph has a directed hamiltonian cycle. We prove that the underlying graph of any in-tournament digraph is l-homotopic. We investigate the problem of which graphs are orientable as in-tournament digraphs and prove that any graph representable as an intersection subgraph of a unicyclic graph can be so oriented. It is shown that there is a polynomial algorithm for recognizing those graphs that can be oriented as in-tournament digraphs.
14351696
A sufficient condition for a semicomplete multipartite digraph to be Hamiltonian
Abstract A multipartite tournament is an orientation of a complete k -partite graph for some k ⩾ 2. A factor of a digraph D is a collection of vertex disjoint cycles covering all the vertices of D . We show that there is no degree of strong connectivity which together with the existence of a factor will guarantee that a multipartite tournament is Hamiltonian. Our main result is a sufficient condition for a multipartite tournament to be Hamiltonian. We show that this condition is general enough to provide easy proofs of many existing results on paths and cycles in multipartite tournaments. Using this condition, we obtain a best possible lower bound on the length of a longest cycle in any strongly connected multipartite tournament.
43442956
Representation characterizations of chordal bipartite graphs
A bipartite graph is chordal bipartite if it does not contain an induced cycle of length at least six. We give three representation characterizations of chordal bipartite graphs. More precisely, we show that a bipartite graph is chordal bipartite if and only if the complement is the intersection graph of a family of pairwise compatible claws in a weighted hypercircle. (A hypercircle is a graph which consists of internally vertex disjoint paths between two distinguished vertices, and a claw in a hypercircle is a connected subgraph containing exactly one of the two distinguished vertices.) We also introduce two classes of bipartite graphs, both containing interval bigraphs and interval containment bigraphs. They are compatible subtree intersection bigraphs and compatible subtree containment bigraphs. We show that these two classes are identical to the class of chordal bipartite graphs.
31025959
A Note on Spanning Local Tournaments in Locally Semicomplete Digraphs
We prove a result which implies that every k-connected locally semicomplete digraph which is not a semicomplete digraph must contain a k-connected spanning local tournament. This improves an earlier result of Guo and partially answers a question of Jackson and Thomassen.
4803217
Pushing the cycles out of multipartite tournaments
Abstract Let D be a digraph and X ⊆ V ( D ). By pushing X we mean reversing each arc of D with exactly one end in X. Klostermeyer proved that it is NP-complete to decide if a given digraph can be made acyclic using the push operation. Here we characterize, in terms of forbidden subdigraphs, the multipartite tournaments which can be made acyclic (resp. ordinary, unidirectional) using the push operation. This implies that the problem of deciding if a given multipartite tournament can be made acyclic (resp. ordinary, unidirectional) using the push operation and, if so, finding a suitable subset of vertices to push, is solvable in polynomial time.
14811510
Specification back-propagation and its application to DC fault simulation for analog/mixed-signal circuits
In this paper we present the specification backpropagation technique which enables one to derive the constraint of an internal functional block with respect to a given DC specification for an analog/mixed-signal system. Based on this technique, we implement an efficient fault simulator which reduces the required efforts by (1) removing undetectable faults from the fault list, and (2) performing fault simulation only locally for the fault block. Simulation results on an industrial design show a speedup factor of 7.2 with 98% correct classification of detected and undetected faults as compared with full-chip DC fault simulation.
6321071
The Myth of the Boundaryless Organization
Technology does not make cultural and business boundaries disappear simply because it exists.
36043890
Remote Visualization by Browsing Image Based Databases with Logistical Networking
5118559
The Effect of Restarts on the Efficiency of Clause Learning
Given the common use of restarts in today's clause learning SAT solvers, the task of choosing a good restart policy appears to have attracted remarkably little interest. On the other hand, results have been reported on the use of different restart policies for combinatorial search algorithms. Such results are not directly applicable to clause learning SAT solvers, as the latter are now understood as performing a form of resolution, something fundamentally different from search (in the sense of backtracking search for satisfying assignments). In this paper we provide strong evidence that a clause learning SAT solver could benefit substantially from a carefully designed restart policy (which may not yet be available). We begin by pointing out that the restart policy works together with other aspects of a SAT solver in determining the sequence of resolution steps performed by the solver, and hence its efficiency. In this spirit we implement a prototype clause learning SAT solver that facilitates restarts at arbitrary points, and conduct experiments on an extensive set of industrial benchmarks using various restart policies, including those used by well-known SAT solvers as well as a universal policy proposed in 1993 by Luby et al. The results indicate a substantial impact of the restart policy on the efficiency of the solver, and provide motivation for the design of better restart policies, particularly dynamic ones.
9736317
Characterization of a pseudo-random testing technique for analog and mixed-signal built-in-self-test
In this paper, we characterize and evaluate the effectiveness of a pseudo-random-based implicit functional testing technique for analog and mixed-signal circuits. The analog test problem is transformed into the digital domain by embedding the device-under-test (DUT) between a digital-to-analog-converter and an analog-to-digital converter. The pseudo-random testing technique uses band-limited digital white noise (pseudo-random-patterns) as input stimulus. The signature is constructed by computing the cross-correlation between the digitized output response and the pseudo-random input sequence. We have implemented a DSP-based hardware testbed to evaluate the effectiveness of the pseudo-random testing technique. Our results show that we can achieve close to 100% yield and fault coverages by carefully selecting only two cross-correlation samples. Noise level and total harmonic distortion below 0.1% and 0.5%, respectively, do not affect the classification accuracy.