11462933
On flows in bidirected graphs
Bouchet conjectured that every bidirected graph which admits a nowhere-zero bidirected flow will admit a nowhere-zero bidirected 6-flow [A. Bouchet, Nowhere-zero integer flows on a bidirected graph, J. Combin. Theory Ser. B 34 (1983) 279-292]. He proved that this conjecture is true with 6 replaced by 216. Zyka proved in his Ph.D dissertation that it is true with 6 replaced by 30. Khelladi proved it is true with 6 replaced with 18 for 4-connected graphs [A. Khelladi, Nowhere-zero integer chains and flows in bidirected graphs, J. Combin. Theory Ser. B 43 (1987) 95-115]. In this paper, we prove that Bouchet's conjecture is true for 6-edge connected bidirected graphs.
80453
Chords of longest circuits in locally planar graphs
It was conjectured by Thomassen ([B. Alspach, C. Godsil, Cycle in graphs, Ann. Discrete Math. 27 (1985)], p. 466) that every longest circuit of a 3-connected graph must have a chord. This conjecture is verified for locally 4-connected planar graphs, that is, let N be the set of natural numbers; then there is a function h : N → N such that, for every 4-connected graph G embedded in a surface S with Euler genus g and face-width at least h(g), every longest circuit of G has a chord.
36530209
Determination of the star valency of a graph
The star valency of a graph G is the minimum, over all star decompositions π, of the maximum number of elements in π incident with a vertex. The maximum average degree of G, denoted by dmax-ave(G), is the maximum average degree of all subgraphs of G. In this paper, we prove that the star valency of G is either ⌈dmax-ave(G)/2⌉ or ⌈dmax-ave(G)/2⌉ + 1, and provide a polynomial time algorithm for determining the star valency of a graph.
46639086
Triangle-Free Circuit Decompositions and Petersen Minor
In this paper, we characterize those simple graphs with no Petersen minor which admit triangle-free circuit decompositions.
23191981
Cycles of all lengths in arc-3-cyclic semicomplete digraphs
Abstract Let D be an arc-3-cyclic, semicomplete digraph and uv be an arc of D contained in a cycle of length r . If vu ∉ A ( D ) then the arc uv is contained in cycles of length h : 3 ⩽ h ⩽ r , or if δ + ( D ), δ − ( D ) ⩾ 3 then the arc uv is contained in cycles of length h : 6 ⩽ h ⩽ r . Also included in this paper is a very useful crossing arc theorem .
43360105
Factorizations of regular graphs
Let G be a k-regular graph of order 2n such that k≥n. Hilton (J. Graph Theory, 9 (1985), 193–196) proved that G contains at least ⌊k3⌋ edge-disjoint 1-factors. Hilton's theorem is improved in this paper that G contains at least ⌊k2⌋ edge-disjoint 1-factors. The following result is also proved in this paper: Let G be a 2-connected, k-regular, non-bipartite graph of order at most 3k − 3 and x, y be a pair of distinct vertices. If Gβ {x, y} is connected, then G contains an (x, y)-Hamilton path.
38237419
Comparison of inter-area rekeying algorithms for secure wireless group communications
Many emerging mobile wireless applications depend upon secure group communications, in which data is encrypted and the group's data encryption key is changed whenever a member joins or leaves the group's session. Hierarchical approaches have recently been proposed to manage the distribution of the data encryption key in a scalable manner for fixed (non-mobile) networks. In this paper, we characterize the impact of mobility on secure rekeying of group communication in a hierarchical key-distribution framework. We propose several rekeying algorithms that preserve confidentiality as members move within the hierarchy. The algorithms differ in the locality of communication, the amount of messages needed to rekey the data key/key-encryption key, the key-encryption key rekey rate, and the number of key-encryption keys held by group members. We develop Markov models to quantify the performance of the proposed algorithms. Our results shows that the FEDRP and SR inter-area rekeying algorithms are superior under different circumstances. In the situation of lower arrival rate and higher mobility, SR has the lowest intra-AS message rate, rekey rate and a low inter-AS message rate. On the other hand, with higher arrival rate and lower mobility, FEDRP has a low rekey rate, inter-AS message rate and the lowest intra-AS message rate. This is achieved by allowing members to hold a small number of keys. In a wireless environment, where bandwidth is often a limiting resource, minimization of communication overhead is of critical importance. This goal could be achieved by using a dynamic strategy to combine the benefits of FEDRP and SR algorithms.
40464778
A model for compressing probabilities in belief networks
Probabilistic reasoning with belief (Bayesian) networks is based on conditional probability matrices. Thus it suffers from NP-hard implementations. In particular, the amount of probabilistic information necessary for the computations is often overwhelming. So, compressing the conditional probability table is one of the most important issues faced by the probabilistic reasoning community. Santos suggested an approach (called linear potential functions) for compressing the information from a combinatorial amount to roughly linear in the number of random variable assignments. However, much of the information in Bayesian networks, in which there are no linear potential functions, would be fitted by polynomial approximating functions rather than by reluctantly linear functions. For this reason, we construct a polynomial method to compress the conditional probability table in this paper. We evaluated the proposed technique, and our experimental results demonstrate that the approach is efficient and promising.
30275744
Robust Active Shape Model Construction and Fitting for Facial Feature Localization
Active Shape Model (ASM) has proved to be a powerful tool for interpreting face images. However, it may fail in the presence of non-Gaussian noise, or outliers. In this paper, we present a framework for both automatic model construction and efficient model fitting with outliers. In model construction, the training face samples are automatically labeled by local image search using Gabor wavelet features. Then robust principle component analysis (RPCA) is applied to capture the statistics of shape variations. In model fitting, an error function is introduced to deal with the outlier problem, which provides a connection to robust M-estimation. Gauss-Newton algorithm is adopted to efficiently optimize the robust energy function. Extensive experiments demonstrate the efficiency and robustness of our approach over previous methods.
3952600
TCP smoothness and window adjustment strategy
We observe that even when the system throughput is relatively stable,end users of media-streaming applications do not necessarily experience smooth throughput, due to the unsynchronized window adjustments triggered by random congestion indications. We analyze and evaluate the negative impact of random window adjustments on smoothness, short-term fairness, and long-term fairness. We further propose an experimental congestion avoidance mechanism, namely TCP(/spl alpha/, /spl beta/, /spl gamma/, /spl delta/), based on coordinated window adjustments. The flow-level smoothness is enhanced significantly for media-streaming applications, without a cost on fairness and responsiveness. Responsiveness is even boosted when bandwidth is underutilized.
21282948
Information-Based Cooperation in Multiple Agent Systems
In this paper, we divide the cooperation in multiple agent systems into task-based cooperation and information-based cooperation. We describe information-based cooperation as information synthesizing and decision making. To implement information synthesizing, agents' beliefs are decomposed into two levels. The higher level represents the possible information, and the lower level subsequently estimates a number function for the belief by synthesizing the possible information.