40944529
Symmetric Graphs of Order a Product of Two Distinct Primes
A simple undirected graph ? is said to be symmetric if its automorphism group Aut ? is transitive on the set of ordered pairs of adjacent vertices of ?, and ? is said to be imprimitive if Aut ? acts imprimitively on the vertices of ?. Let k and p be distinct primes with k < p. This paper gives a classification of all imprimitive symmetric graphs on kp vertices for k ? 5. The cases k < 5 have been treated previously by Cheng and Oxley (k = 2) and the second and third authors (k = 3), and the classification of primitive symmetric graphs on kp vertices with k ? 5 was done by the first and third authors.
29378412
Vertex-primitive digraphs of prime-power order are hamiltonian
Abstract Witte [6] proved that every connected Cayley digraph of a p -group is hamiltonian. In this note we generalize Witte's result to connected vertex-primitive digraphs of prime-power order; namely, we prove that every connected vertex-primitive digraph of prime-power order is hamiltonian.
1797921
Arc-transitive circulant digraphs of odd prime-power order
In this paper, the full automorphism group of a circulant digraph of prime-power order is investigated, and as a result, a complete classification of arc-transitive circulant graphs of odd prime-power order is given.
39351233
Note on Infinite Families of Trivalent Semisymmetric Graphs
A simple undirected graph is said to be semisymmetric if it is regular and edge-transitive but not vertex-transitive. This paper uses the groups PSL (2, p) and PGL (2, p), where p is a prime, to construct two new infinite families of trivalent semisymmetric graphs.
43124802
On the Isomorphisms of Cayley Graphs of Abelian Groups
Let G be a finite group, S a subset of G\{1}, and let Cay (G, S) denote the Cayley digraph of G with respect to S. If, for any subset T of G\{1}, Cay(G, S) ≅ Cay(G, T) implies that Sα = T for some α ∈ Aut(G), then S is called a CI-subset. The group G is called a CIM-group if for any minimal generating subset S of G, S ∪ S-1 is a CI-subset. In this paper, CIM-abelian groups are characterized.
7439709
2-Arc-transitive regular covers of complete graphs having the covering transformation group Z3p
A family of 2-arc-transitive regular covers of a complete graph is investigated. In this paper, we classify all such covering graphs satisfying the following two properties: (1) the covering transformation group is isomorphic to the elementary abelian p-group Zp3, and (2) the group of fiber-preserving automorphisms acts 2-arc-transitively. As a result, new infinite families of 2-arc-transitive graphs are constructed.
19879470
The multiscale medial properties of interfering image structures
The multiscale medial axis (MMA) is a robust shape representation in analysing objects in greylevel images. It is computed as ridges in the medialness scale-space of an image. In this paper the multiscale medial properties of overlapping objects are investigated, the result of which is novel to the community in that the existing studies only concentrated on isolated objects. To improve the distinguishability of these objects, a sliding window algorithm is proposed to detect locally optimal scale ridges in scale space. When used in the medialness scale-space of an image, this efficient method can extract a complete set of MMAs for interfering objects, in contrast with the globally optimal scale ridge definition which has been widely used. This is demonstrated in the applications in medical images.
53245552
Simultaneous shield insertion and net ordering for capacitive and inductive coupling minimization
In this article, we first show that existing net ordering formulations to minimize noise are no longer sufficient with the presence of inductive noise, and shield insertion is needed to minimize inductive noise. Using a Keff model as the figure of merit for inductive coupling, we then formulate two simultaneous shield insertion and net ordering (SINO) problems: the optimal SINO/NF problem to find a minimal area SINO solution that is free of capacitive and inductive noise, and the optimal SINO/NB problem to find a minimal area SINO solution that is free of capacitive noise and is under the given inductive noise bound. We reveal that both optimal SINO problems are NP-hard, and propose effective approximate algorithms for the two problems. Experiments show that our SINO/NB algorithm uses from 51p to 82p fewer shields compared to uniform shield insertion and net ordering (US + NO), and uses from 4p to 47p fewer shields compared to separated net ordering and shield insertion (NO + SI). Furthermore, the SINO/NB solutions under practical noise bounds use from 38p to 61p fewer shields compared to SINO/NF solutions, and use up to 36p fewer shields compared to the theoretical lower bound for optimal SINO/NF solutions. Moreover, we show that the Keff model has a high fidelity versus the noise voltage computed using accurate RLC circuit models and SPICE simulations. To the best of our knowledge, it is the first work that presents an in-depth study on the automatic layout optimization of multiple nets to minimize both capacitive and inductive noise.
13407089
Event detection and period extraction using multi-scale symmetry and entropy
We present a system for detecting discrete periodic events over a short interval and in the presence of interference. In the first stage symmetries are identified using scale-space representation. This process detects signal events with a low signal-to-noise ratio but has the potential to introduce a number of false responses. This process is followed by an entropy-based algorithm that can robustly extract periodicities from a set of observed discrete events in the presence of a large number of false alarms. The event detection and period extraction processes have a low computational cost and can extract signal periodicity after a short observation time. This scheme was evaluated against four previously reported methods. Results demonstrate that the period extraction algorithm presented here is more reliable than three of the previously reported algorithms. The reliability of the algorithm presented here was similar to that of the fourth method but the computational cost was much less.
1185541
A serializability violation detector for shared-memory server programs
We aim to improve reliability of multithreaded programs by proposing a dynamic detector that detects potentially erroneous program executions and their causes. We design and evaluate a Serializability Violation Detector (SVD) that has two unique goals: (I) triggering automatic recovery from erroneous executions using backward error recovery (BER), or simply alerting users that a software error may have occurred; and (II) helping debug programs by revealing causes of error symptoms.Two properties of SVD help in achieving these goals. First, to detect only erroneous executions, SVD checks serializability of atomic regions, which are code regions that need to be executed atomically. Second, to improve usability, SVD does not require a priori annotations of atomic regions; instead, SVD approximates them using a heuristic. Experimental results on three widely-used multithreaded server programs show that SVD finds real bugs and reports modest false positives. The goal of this paper is to develop a detector suitable for (I) BER-based avoidance of erroneous program executions; and (II) alerting users as software errors occur. We argue that such a detector should have the following two properties.
10735574
Forwarding indices of folded n-cubes
For a given connected graph G of order n, a routing R is a set of n(n - 1) elementary paths specified for every ordered pair of vertices in G. The vertex (resp. edge) forwarding index of a graph is the maximum number of paths of R passing through any vertex (resp. edge) in the graph. In this paper, the authors determine the vertex and the edge forwarding indices of a folded n-cube as (n-1)2n-1 +1-((n+l)/2) (n ⌊n+1/2⌋) and 2n-(n,⌊n+1/2⌋),respectively.