10976624
On the maximum induced forests of a connected cubic graph without triangles
Let t(G) denote cardinality of a maximum induced forest of a graph G with n vertices. For connected simple cubic graphs G without triangles, it is shown that t(G)?2n3 except for two particular graphs. This lower bound is sharp and it improves a result due to J.A. Bondy, et al. 1]. Using this result, we show that Ewald Speckenmeyer's Conjecture, i.e. t(G)?2n3 for all biconnected cubic graphs G with girth 4, is true, except for two particular graphs, which we describe.
43125969
On claws belonging to every tournament
A directed graph is said to ben-unavoidable if it is contained as a subgraph by every tournament onn vertices. A number of theorems have been proven showing that certain graphs aren-unavoidable, the first being Rédei's results that every tournament has a Hamiltonian path. M. Saks and V. Sós gave more examples in [6] and also a conjecture that states: Every directed claw onn vertices such that the outdegree of the root is at most [n/2] isn-unavoidable. Here a claw is a rooted tree obtained by identifying the roots of a set of directed paths. We give a counterexample to this conjecture and prove the following result:any claw of rootdegree≤n/4 is n-unavoidable.
28342911
A matching game
Abstract We consider the following 2-person game playing on K n,n . Two players, maker and breaker, alternately take a previously untaken edge from K n,n , the complete bipartite graph of order 2 n . The game continues until all the edges of K n,n have been taken. Then the edges taken by maker induce a subgraph of K n,n , which is denoted by G ( M ). At the end of the game, we calculate the number of edge-disjoint perfect matchings of G ( M ), and denote this number by m ( M ). The maker's aim is to make this number big and the breaker's is to force it small. We will prove the following result: For any given η >0, there exists N ( η ), such that if n ⩾ N ( η ), then maker has a strategy to guarantee m(M)⩾( 1 2 −η)n .
12380989
Hamiltonian cycles in bipartite graphs
We give a sufficient condition for bipartite graphs to be Hamiltonian. The condition involves the edge-density and balanced independence number of a bipartite graph.
6155777
Claws contained in all n-tournaments
Abstract We prove that any claw of order n with degree d≤ 3 8 n is n-unavoidable, which means that any tournament of order n contains it as a subdigraph. A simple corollary is that any tournament has a directed Hamiltonian path.
18993736
Matching 2.5D Scans for Face Recognition
The performance of face recognition systems that use two-dimensional images is dependent on consistent conditions such as lighting, pose, and facial appearance. We are developing a face recognition system that uses three-dimensional depth information to make the system more robust to these arbitrary conditions. We have developed a face matching system that automatically correlates points in three dimensions between two 2.5D range images of different views. A hybrid Iterative Closest Point (ICP) scheme is proposed to integrate two classical ICP algorithms for fine registration of the two scans. A robust similarity metric is defined for matching purpose. Results are provided on a preliminary database of 10 subjects (one training image per subject) containing frontal face images of neutral expression with a testing database of 63 scans that varied in pose, expression and lighting.
16545185
Hybrid Methods for POS Guessing of Chinese Unknown Words
This paper describes a hybrid model that combines a rule-based model with two statistical models for the task of POS guessing of Chinese unknown words. The rule-based model is sensitive to the type, length, and internal structure of unknown words, and the two statistical models utilize contextual information and the likelihood for a character to appear in a particular position of words of a particular length and POS category. By combining models that use different sources of information, the hybrid model achieves a precision of 89%, a significant improvement over the best result reported in previous studies, which was 69%.
121253028
Three-dimensional model based face recognition
The performance of face recognition systems that use two-dimensional (2D) images is dependent on consistent conditions such as lighting, pose and facial expression. We are developing a multi-view face recognition system that utilizes three-dimensional (3D) information about the face to make the system more robust to these variations. This work describes a procedure for constructing a database of 3D face models and matching this database to 2.5D face scans which are captured from different views, using coordinate system invariant properties of the facial surface. 2.5D is a simplified 3D (x, y, z) surface representation that contains at most one depth value (z direction) for every point in the (x, y) plane. A robust similarity metric is defined for matching, based on an iterative closest point (ICP) registration process. Results are given for matching a database of 18 3D face models with 113 2.5D face scans.
176930
Face detection and synthesis using Markov random field models
Markov random fields (MRFs) are proposed as viable stochastic models for the spatial distribution of gray levels for images of human faces. These models are trained using data bases of face and non-face images. The trained MRF models are then used for detecting human faces in test images. We investigate the performance of the face detection algorithm for two classes of MRFs given by the first- and second-order neighborhood systems. From the cross validation results and from actual detection in real images, it is shown that the second-order model makes fewer false detections. We also investigate the possibility of increasing our training data base of faces by simulating face-like images from the trained MRFs. The performance of the re-trained MRFs based on added face-like images is compared to the original training data base.
19393995
Skilled Forgery Detection in On-Line Signatures: A Multimodal Approach
Signature recognition has a long history of usage in authentication of transactions and legal contracts and hence is easily accepted by users in a variety of applications. However, the problem of skilled forgeries is an important challenge that needs to be overcome before signature recognition systems will become viable in unsupervised authentication systems. In this paper, we present a multimodal approach to forgery detection, where a physiological trait, the face of the signing person, is used to validate the signature. Methods of normalizing and combining the matching scores from the individual modalities are investigated. Test results of the system on a database of 100 users is presented. The system achieves an equal error rate of 2.2% in the presence of high quality skilled forgeries and could detect all the skilled forgeries at a genuine acceptance rate of 75%.