Applied Mechanics and Materials Vols. 236-237

Abstract: Subpixel technique of linear CCD is effective to enhance the spatial resolution without increasing the focal length of optics and reducing the pixel size. To compare image quality of two main subpixel imaging modes, quincunx sampling and four-point sampling, a method to quantitatively evaluate image quality of subpixel based on MTF was proposed. The MTF of quincunx and four-point sampling modes were derived. Analytical results shows that theoretical limiting resolution of quincunx sampling and four-point sampling is improved to 1.4 and 1.86 times respectively, and MTF values at Nyquist frequency of two modes are increased by 0.1106 and 0.1679, respectively. MTFA in (0, 0.5) of two subpixel imaging modes were calculated and results illustrates that four-point sampling offers much more improvement with image quality than quincunx sampling, at the cost of double amount of data. A model for simulating subpixel imaging using Matlab was established, and simulation results of spoke target verify the theoretical analysis.

Abstract: This paper investigates the resource allocation of Orthogonal Frequency Division Multiplexing Access (OFDMA) cellular network with DF relaying in the downlink. A joint scheme of relay selection, subcarrier assignment and power allocation is proposed to maximize the system sum rate subject to individual power constraints and heterogeneous users' rate requirements. Since the original problem is a mixed integer programming (MIP), we transform it to a standard convex optimization by continuous relaxation and solve it via iterative water-filling (IWF) and subgradient methods in the dual domain. Beside the joint scheme, the upper bound is studied through an exhaustive bisection search. Simulations results show that the proposed scheme outperforms the traditional methods in terms of both system throughput and users' satisfactions.

Abstract: An Opportunistic Network Coding (ONC) based transmission approach (OCRA) is proposed to improve the transmission efficiency in wireless broadcast scenario. OCRA combines as many as lost packets by adopting opportunistic coding strategy, and makes terminals retrieve lost packets from single retransmission packet thus improving transmission efficiency. The theoretical analysis and simulation results show the feasibility and effectiveness of proposed approach.

Abstract: An automatic agglomeration methodology to generate coarse grids for 3D flow solutions on anisotropic unstructured grids has been introduced in this paper. The algorithm combines isotropic octree based coarsening and anisotropic directional agglomeration to yield a desired coarsening ratio and high quality of coarse grids, which developed for cell-centered multigrid applications. This coarsening strategy developed is presented on an unstructured grid over 3D ONERA M6 wing. It is shown that the present method provides suitable coarsening ratio and well defined aspect ratio cells at all coarse grid levels.

Abstract: A wireless sensor network consists of distributed devices which can monitor physical and environmental conditions and have a lot of applications, such as environmental monitoring, habitat monitoring, object tracking, nuclear reactor controlling, fire detection and traffic monitoring. Although it has a lot of potential applications, a wireless sensor network is highly energy constrained. Limited energy resource to the sensor becomes an obstacle for its applications and efficient usage of energy helps in improving the network lifetime. Suppose a network has a high-density of sensor nodes, there will be lots of problems such as the intersection of sensing, redundant data, communication interference and energy waste. So it is necessary to set up a management application to maintain these resources. On the other hand, a high-density network can be fault tolerant and more accurate than low-density sensor networks. In this paper, we proposed a new scheduling for sensor networks which can decide the nodes to be on or off and maintain the coverage area for the original one. This management schema may take a node out of service temporally in order to save energy. Our design uses a Voronoi Diagram, which decomposes the sensing area into regions around each node.

Abstract: This paper studies the coordinate optimization control problem of networked control systems (NCSs) with random time delay and packet dropout. A discrete-time system model of NCSs with time-delays and data packet dropout is proposed. A method of state estimation base on extra kalman filter is given. Then a gain-schedule adaptive LQG control strategy base on effective delay-estimation online is proposed. The result illustrate that the effectiveness of the proposed controller design and the satisfactory performance of the system.

Abstract: Content-Based Copy Detection (CBCD) is a heated research area. A variety of features are extracted and applied extensively to improve the performance of CBCD systems. A novel scheme which adopts 3-Dimensional SIFT Descriptors (Paul Scavenger, 2007) based on the innovative dynamic tunnels is proposed in this paper. The algorithm is aim to reach a proper balance between efficiency and accuracy. Experimental results indicate that the algorithm achieves an accuracy match with inexpensive computational cost.

Abstract: The current product configuration methods can only be applied to the situation when the configuration information is specific or fuzzy. In order to address this problem, a new multi-objective optimization approach to configuration design with the consideration of several types of uncertain information was proposed. The uncertain configuration information was uniformly described with interval numbers. Targeting on optimizing the performance, cost and term of configured products, three mathematical models was established, and some adaptations were made to these models according to the interval number. A multi-objective optimization model was generated by integrating the three models. The non-dominated sorting genetic algorithm II was used to solve the model and a Pareto optimal set of product configuration schemes was obtained. A general optimum selection method was put forward based on the fuzzy set theory, and the optimization sequence of the Pareto solutions can be founded using the method. The proposed approach can effectively deal with the problem of product configuration optimization under uncertain information.

Abstract: As ant colony optimization algorithm and clustering routing algorithm were discussed deeply, a clustering routing algorithm based ant colony optimization (CRAACO) for wireless sensor networks has been put forward. To test the performance of CRAACO, simulations have been done from information fusion rates, remaining energy and network lifetime. The experiment results show that the CRAACO can work effectively and may be used in wireless sensor networks.

Abstract: The imaging measurement system must be calibrated before application. In calibration procedure, sub-pixel center extraction is the crucial step for the final accuracy. In this paper, a new sub-pixel extraction method is proposed. Edge detection at pixel level is obtained using LOG operator, then sub-pixel edge detection is realized using the Facet model. Finally, the least squares ellipse fitting is operated on the sub-pixel edge to determine the sub-pixel center. Experiment on a series of simulated images indicates that this algorithm is able to realize the center location accuracy of 0.01-0.02 pixel, and meets the requirement of sub-pixel level.