Acyclic domination on bipartite permutation graphs
For a graph G = (V, E), a subset S ⊆ V is called an acyclic dominating set of G if every vertex in V - S is adjacent to at least one vertex in S and the subgraph induced by S contains no cycles. In this paper, we present a linear time algorithm for transforming a minimum dominating set in a bipartite permutation graph into a minimum acyclic dominating set. Chao et al. gave a linear time algorithm to find a minimum dominating set of a permutation graph. Thus, we show that the acyclic domination problem is linear time solvable for bipartite permutation graphs.

title: Power domination in block graphs
abstract: The problem of monitoring an electric power system by placing as few measurement devices in the system as possible is closely related to the well-known domination problem in graphs. In 2002, Haynes et al. considered the graph theoretical representation of this problem as a variation of the domination problem. They defined a set S to be a power dominating set of a graph if every vertex and every edge in the system is monitored by the set S (following a set of rules for power system monitoring). The power domination number γp(G) of a graph G is the minimum cardinality of a power dominating set of G. This problem was proved NP-complete even when restricted to bipartite graphs and chordal graphs. In this paper, we present a linear time algorithm for solving the power domination problem in block graphs. As an application of the algorithm, we establish a sharp upper bound for power domination number in block graphs and characterize the extremal graphs.

title: An Improved Approximation Algorithm for Uncapacitated Facility Location Problem with Penalties
abstract: In this paper, we consider an interesting variant of the facility location problem called uncapacitated facility location problem with penalties (UFLWP for short) in which each client is either assigned to an opened facility or rejected by paying a penalty. We present a 1.8526-approximation algorithm for the UFLWP problem. Our algorithm first enhances the primal-dual method for the UFLWP problem  so that outliers can be recognized more efficiently, and then applies a local search heuristic to further reduce the cost for serving those non-rejected clients.

title: Nurbs Approximation of A-Splines and A-Patches
abstract: Given A-spline curves and A-patch surfaces that are implicitly defined on triangles and tetrahedra, we determine their NURBS representations. We provide a trimmed NURBS form for A-spline curves and a parametric tensor-product NURBS form for A-patch surfaces. We concentrate on cubic A-patches, providing a C1-continuous surface that interpolates a given triangulation together with surface normals at the vertices. In many cases we can generate cubic trimming curves that are rationally parametrizable on the triangular faces of the tetrahedra; for the remaining faces we resort to using quadratic curves, which are always rationally parametrizable, to approximate the cubic trimming curves.

title: Surface modelling using fourth order geometric flows
abstract: We use two fourth order geometric partial differential equations to efficiently solve several surface modelling problems, including the surface blending, the N-sided hole filling and the free-form surface fitting with the G/sup 1/ boundary continuity. The nonlinear equations used include the surface diffusion flow and the Willmore flow. These nonlinear equations are discretized using the mixed finite element method based on the combination of the loop's basis and the linear basis. The proposed approach is simple, efficient and gives very desirable results.

title: Human action recognition in smart classroom
abstract: This paper presents a new system for teachers' natural complex action recognition in the smart classroom in order to realize an intelligent cameraman and virtual mouse. First, the system proposes a hybrid human model and employs a 2-order B-spline function to detect the two shoulder joints in the silhouette image to obtain the basic motion features including the elbow angles, motion parameters of the face and two hands. Then, a primitive-based coupled hidden Markov model (PCHMM) is presented for natural context-dependent action recognition. Last, some comparison experiments show that PCHMM is better than the traditional HMM and coupled HMM.

title: Error Analysis of Pure Rotation-Based Self-Calibration
abstract: Self-calibration using pure rotation is a well-known technique and has been shown to be a reliable means for recovering intrinsic camera parameters. However, in practice, it is virtually impossible to ensure that the camera motion for this type of self-calibration is a pure rotation. In this paper, we present an error analysis of recovered intrinsic camera parameters due to the presence of translation. We derived closed-form error expressions for a single pair of images with nondegenerate motion; for multiple rotations for which there are no closed-form solutions, analysis was done through repeated experiments. Among others, we show that translation-independent solutions do exist under certain practical conditions. Our analysis can be used to help choose the least error-prone approach (if multiple approaches exist) for a given set of conditions.