Double loop networks with minimum delay

AbstractDouble loop networks have been widely studied as practical and reliable computer networks. Let N denote the number of stations in a double loop network. The literature has proposed a topology which yields the diameter 2√N. In this paper we give a heuristic method which finds a topology with diameter roughly √3N for large N. We also give several infinite classes of values of N for which topologies are found that achieve the lower bound ⌈√3N⌉ − 2 for the diameter

A new construction of 3̄-separable matrices via an improved decoding of Macula’s construction

AbstractMacula proposed a novel construction of pooling designs which can effectively identify positive clones and also proposed a decoding method. However, the probability of an unresolved positive clone is hard to analyze. In this paper we propose an improved decoding method and show that for d=3 an exact probability analysis is possible. Further, we derive necessary and sufficient conditions for a positive clone to be unresolved and gave a modified construction which avoids this necessary condition, thus resulting in a 3̄-separable matrix

Concurrent Geometric Multicasting

We present MCFR, a multicasting concurrent face routing algorithm that uses geometric routing to deliver a message from source to multiple targets. We describe the algorithm's operation, prove it correct, estimate its performance bounds and evaluate its performance using simulation. Our estimate shows that MCFR is the first geometric multicast routing algorithm whose message delivery latency is independent of network size and only proportional to the distance between the source and the targets. Our simulation indicates that MCFR has significantly better reliability than existing algorithms

Structural and doping effects in the half-metallic double perovskite A2A_2CrWO6_6

he structural, transport, magnetic and optical properties of the double perovskite $A_2$CrWO$_6$ with $A=\text{Sr, Ba, Ca}$ have been studied. By varying the alkaline earth ion on the $A$ site, the influence of steric effects on the Curie temperature $T_C$ and the saturation magnetization has been determined. A maximum $T_C=458$ K was found for Sr$_2$CrWO$_6$ having an almost undistorted perovskite structure with a tolerance factor $f\simeq 1$. For Ca$_2$CrWO$_6$ and Ba$_2$CrWO$_6$ structural changes result in a strong reduction of $T_C$. Our study strongly suggests that for the double perovskites in general an optimum $T_C$ is achieved only for $f \simeq 1$, that is, for an undistorted perovskite structure. Electron doping in Sr$_2$CrWO$_6$ by a partial substitution of Sr$^{2+}$ by La$^{3+}$ was found to reduce both $T_C$ and the saturation magnetization $M_s$. The reduction of $M_s$ could be attributed both to band structure effects and the Cr/W antisites induced by doping. Band structure calculations for Sr$_2$CrWO$_6$ predict an energy gap in the spin-up band, but a finite density of states for the spin-down band. The predictions of the band structure calculation are consistent with our optical measurements. Our experimental results support the presence of a kinetic energy driven mechanism in $A_2$CrWO$_6$, where ferromagnetism is stabilized by a hybridization of states of the nonmagnetic W-site positioned in between the high spin Cr-sites.Comment: 14 pages, 10 figure

Particle swarm optimization for the Steiner tree in graph and delay-constrained multicast routing problems

This paper presents the first investigation on applying a particle swarm optimization (PSO) algorithm to both the Steiner tree problem and the delay constrained multicast routing problem. Steiner tree problems, being the underlining models of many applications, have received significant research attention within the meta-heuristics community. The literature on the application of meta-heuristics to multicast routing problems is less extensive but includes several promising approaches. Many interesting research issues still remain to be investigated, for example, the inclusion of different constraints, such as delay bounds, when finding multicast trees with minimum cost. In this paper, we develop a novel PSO algorithm based on the jumping PSO (JPSO) algorithm recently developed by Moreno-Perez et al. (Proc. of the 7th Metaheuristics International Conference, 2007), and also propose two novel local search heuristics within our JPSO framework. A path replacement operator has been used in particle moves to improve the positions of the particle with regard to the structure of the tree. We test the performance of our JPSO algorithm, and the effect of the integrated local search heuristics by an extensive set of experiments on multicast routing benchmark problems and Steiner tree problems from the OR library. The experimental results show the superior performance of the proposed JPSO algorithm over a number of other state-of-the-art approaches

Identical transitions in the strongly deformed Sr-99 and Sr-100

The decay of the very neutron-rich nucleus Rb-100 has been studied by gamma-spectroscopy of on-line mass-separated samples. Schemes for beta-decay to Sr-100 and beta-n-decay to Sr-99 are presented. New sets of transitions in Sr-99 and Sr-100 with identical energies are observed. All identical bands so far observed in neutron-rich Sr isotopes obey a simple energy rule valid for even-even, odd-even and odd-odd bands.Comment: 31 pages, 7 figures, Phys. Rev. C, in prin

On Macula's error-correcting pool designs

AbstractWe show that Macula's claim of a Hamming distance 4 between any two candidate sets of positive clones in his pool design is incorrect. However, a previous proof of his on a weaker result (with a condition on design parameters) is correct. We also show that the condition is sharp and the distance 4 result is also sharp for arbitrary parameter values

Enumerating Consecutive and Nested Partitions for Graphs

Consecutive & nested partitions have been extensively studied in the set-partition problem as tools with which to search efficiently for an optimal partition. We extend the study of consecutive and nested partitions on a set of integers to the vertex-set of a graph. A subset of vertices is considered consecutive if the subgraph induced by the subset is connected. In this sense the partition problem on a set of integers can be treated as a special case when the graph is a line. In this paper we give the number of consecutive & nested partitions when the graph is a cycle. We also give a partial order on general graphs with respect to these numbers