6516775
Distributions of regular branched surface coverings
In a study of surface branched coverings, one can ask naturally: In how many different ways can a given surface be a branched covering of another given surface? This problem was studied by many authors in Quart. J. Math. Oxford Ser. 2 46 (1995) 485, Math. Scand. 84 (1999) 23, Discrete Math. 156 (1996) 141, Discrete Math. 183 (1998) 193, Discrete Math. (in press), European J. Combin. 22 (2001) 1125, Sibirsk. Mat. Zh. 25 (1984) 606 etc. In this paper, as a complete answer to the question for regular coverings, we determine the distribution of the regular branched coverings of any nonorientable surface S when the covering transformation group and a set of branch points are freely assigned.
623251
Isomorphism classes of bipartite cycle permutation graphs
14536749
Bartholdi zeta functions of graph bundles having regular fibers
As a continuation of computing the Bartholdi zeta function of a regular covering of a graph by Mizuno and Sato in J. Combin. Theory Ser. B 89 (2003) 27, we derive in this paper some computational formulae for the Bartholdi zeta functions of a graph bundle and of any (regular or irregular) covering of a graph. If the fiber is a Schreier graph or it is regular and the voltages to derive the bundle or the covering lie in an Abelian group, then the formulae can be simplified. As a byproduct, the Bartholdi zeta functions of Schreier graphs, Cayley graphs and the cartesian product of a graph and a regular graph are obtained.
40285902
Isoperimetric numbers and bisection widths of double coverings of a complete graph
16002222
Isomorphism classes of cycle permutation graphs
Abstract In this paper, we construct a cycle permutation graph as a covering graph over the dumbbell graph, and give a new characterization of when two given cycle permutation graphs are isomorphic by a positive or a negative natural isomorphism. Also, we count the isomorphism classes of cycle permutation graphs up to positive natural isomorphism, and find the number of distinct cycle permutation graphs isomorphic to a given cycle permutation graph by a positive/negative natural isomorphism. As a consequence, we obtain a formula for finding the number of double cosets of the dihedral group in the symmetric group.
207081381
Enumeration of Regular Graph Coverings Having Finite Abelian Covering Transformation Groups
Several isomorphism classes of graph coverings of a graph G have been enumerated by many authors. An enumeration of the isomorphism classes of n-fold coverings of a graph G was done by Kwak and Lee [Canad. J. Math., XLII (1990), pp. 747--761] and independently by Hofmeister [Discrete Math., 98 (1991), pp. 437--444]. An enumeration of the isomorphism classes of connected n-fold coverings of a graph G was recently done by Kwak and Lee [J. Graph Theory, 23 (1996), pp. 105--109]. But the enumeration of the isomorphism classes of regular coverings of a graph G has been done for only a few cases. In fact, the isomorphism classes of ${\cal A}$-coverings of G were enumerated when ${\cal A}$ is the cyclic group $\BZ_n$, the dihedral group $\BD_n$ (n: odd), and the direct sum of $m$ copies of $\BZ_p$. (See [Discrete Math., 143 (1995), pp. 87--97], [J. Graph Theory, 15 (1993), pp. 621--627], and [Discrete Math., 148 (1996), pp. 85--105]). 
In this paper, we discuss a method to enumerate the isomorphism classes of connected ${\cal A}$-coverings of a graph G for any finite group ${\cal A}$ and derive some formulas for enumerating the isomorphism classes of regular n-fold coverings for any natural number n. In particular, we calculate the number of the isomorphism classes of ${\cal A}$-coverings of G when ${\cal A}$ is a finite abelian group or the dihedral group $\BD_n$. Our method gives partial answers to the open problems 1 and 2 in [Discrete Math., 148 (1996), pp. 85--105] and also gives a formula to calculate the number of the subgroups of a given index of any finitely generated free abelian group.
32342128
Performance Analysis of an Input Queueing ATM Switch with Two Priority Classes
Abstract In this paper, we study an input queueing asynchronous transfer mode (ATM) switch with the preemptive priority scheme. Up to now, many researchers have studied this switch, but their models do not yield accurate results. Therefore, we propose another model and analyze the performance of the switch for two different arrival processes, that is, the independent priority arrival process (IPAP) and the dependent priority arrival process (DPAP). In this paper, we model a virtual head of line (HOL) queue like the previous works, and analyze it using a three-dimensional Markov chain. As for each input queue, we model it as a two-class Geomx/Geom/1 queue with preemptive priority. By using this model, we obtain the mean queueing delay of the low priority class and the maximum throughput of the switch. In case of the IPAP, we compare our result with simulation and those of the previous works to show that our model yields more accurate results. In addition, we compare the performances of those two arrival processes to illustrate their difference.
6731652
Nonmonotonic causal theories
The nonmonotonic causal logic defined in this paper can be used to represent properties of actions, including actions with conditional and indirect effects, nondeterministic actions, and concurrently executed actions. It has been applied to several challenge problems in the theory of commonsense knowledge. We study the relationship between this formalism and other work on nonmonotonic reasoning and knowledge representation, and discuss its implementation, called the Causal Calculator.
16907116
Enhancing the Fuzzy Set Model with Positively Compensatory Operators
The conventional fuzzy set model uses the MIN and MAX operators for the evaluation of boolean operators AND and OR, respectively. It has been criticized to generate incorrect ranked output in many cases. This is because the MIN and MAX operators do not well correspond with human behavior for document ranking. There are a variety of fuzzy operators to replace the MIN and MAX operators. In this paper we first investigate the behavioral aspects of the fuzzy operators and address important issues to affect retrieval effectiveness. We then present the enhanced fuzzy set model based on positively compensatory operators, which are suitable for achieving high retrieval effectiveness. It is also shown through experiments that the enhanced fuzzy set model provides similar retrieval effectiveness and higher retrieval efficiency in comparison with the extended boolean model.
15040426
3D Surface Reconstruction from Scattered Data Using Moving Least Square Method
This paper presents an efficient implementation of moving least square(MLS) approximation for 3D surface reconstruction. The smoothness of the MLS is mainly determined by the weight function where its support greatly affects the accuracy as well as the computational time in the mixed dense and scattered data. In a point-set, possibly acquired from a 3D scanning device, it is important to determine the support of the weight function adaptively depending on the distribution and shape of the given scatter data. Particulary in case of face data including the very smooth parts, detail parts and some missing parts of hair due to low reflectance, preserving some details while filling the missing parts smoothly is needed. Therefore we present a fast algorithm to estimate the support parameter adaptively by a raster scan method from the quantized integer array of the given data. Some experimental results show that it guarantees the high accuracy and works to fill the missing parts very well.
9006063
Performance evaluation model for buyer-carts in B2B EC
Even though B2B EC is becoming popular, there have been not so much studies about performance evaluation methodology for B2B systems. In this paper, after analyzing buyer carts systematically focusing on the buyer's interactional efforts on the typical buying processes of each buyer cart, we propose a quantitative performance evaluation model. For this, we categorize buyer carts in B2B EC as s-cart, i-cart, and b-cart depending upon its residing sites: seller, intermediary, and buyer sites. And after proposing the desired features of buyer carts in B2B EC as identification, collection, trashing, ordering, payment, tracking, recording, purchasing decision support, and transmission of records to e-procurement systems, we derive a performance evaluation model by calculating detail subprocesses from the desired features' viewpoints. By setting variables from interviews of business buyers in 30 listed companies in Korea, we try to evaluate the performance of buyer-carts in B2B EC. In this paper, we suggest a new methodology of performance evaluation for B2B systems, and show that the b-cart platform is more efficient than other buyer carts especially in B2B EC.