Modeling and evaluating IPTV applications in WiMAX networks

Internet Protocol-based Television (IPTV) is a digital television service which delivers television content via an IP network. The rapid growth of wireless network technology in recent years has changed, the way people access the Internet. Adding mobility to IPTV can create a truly compelling ubiquitous service which spans different network domains and varied IP-enabled terminals and devices, such as set-top boxes, PCs and cell phones. However, extending IPTV service to wireless networks requires overcoming bandwidth bottlenecks and high packet loss rates. Following the IEEE 802.16 standard, worldwide interoperability for microwave access (WiMAX) features high data rates and large service coverage, offering a wireless broadband solution for IPTV services. While previous research has focused on creating a broadband IPTV service few studies have practically evaluated IPTV applications in a wireless broadband network environment. In this paper, we model and evaluate a common constant bit rate (CBR)¹ based IPTV application and an IPTV live streaming (PPStreaming)² application while retrieving IPTV content via a WiMAX network. We also use the NS2 simulation tool to evaluate the performance of these two IPTV applications. The evaluation metrics include latency, packet loss, data rate and throughput statistics when the two IPTV applications are run in the WiMAX network. ¹The simplest IPTV solution is to convey video content by CBR. IPTV operators and content delivery networks relay CBR streaming content to control the demand for network capacity. Broadcasters prefer CBR video as it conserves bandwidth resources, but CBR delivery can degrade video quality result in higher overall demand on network capacity. ²PPStreaming (also referred to as P2P streaming Internet TV) is a network for live media streaming. In principle it’s similar to BitTorrent (BT) in that it provides stable and smooth broadcast of TV programs to broadband users. Unlike traditional streaming media, PPStreaming adopts P2P-streaming technology and supports full-scale visits with tens of thousands of simultaneous users. Its client software can be used in the browser or as a standalone executable.     

Wii remote–based low-cost motion capture for automated assembly simulation

This paper describes the development of a Wii remote (Wiimote)–based low-cost motion capture system and demonstrates its application for automated assembly simulation. Multiple Wiimotes are used to form a vision system to perform motion capture in 3D space. A hybrid algorithm for calibrating a multi-camera stereo vision system has been developed based on Zhang’s and Svoboda’s calibration algorithms. This hybrid algorithm has been evaluated and shown accuracy improvement over Svoboda’s algorithm for motion capture with multiple cameras. The captured motion data are used to automatically generate an assembly simulation of objects represented by CAD models in real time. The Wiimote-based motion capture system is practically attractive because it is inexpensive, wireless, and easily portable. Application examples have been developed for a single vision system with two Wiimotes to track the assembly of a microsatellite prototype frame and for an integrated vision system with four Wiimotes to track the assembly of a bookshelf.     

An Efficient Authentication Scheme for Access Control in Mobile Pay-TV Systems

In a mobile pay-TV system, a large number of messages are exchanged for mutual authentication purposes. In traditional authentication schemes, with one-to-one delivery, one authentication message per request is delivered from a head end system to subscribers. This results in the delivery of a large quantity of messages and therefore is inefficient and costly. Moreover, since most traditional schemes use an RSA-based signature for identity validation and nonrepudiation of communication, they suffer from high communication costs. Due to its wireless nature, mobile pay-TV is vulnerable to attacks during hand-off. As traditional schemes do not support hand-off authentication, they are insecure during hand-off. With these shortcomings, they are not suitable for mobile pay-TV. In this paper, we propose an innovative authentication scheme, in which, by providing one-to-many facility, only one authentication message for multiple requests is broadcasted from the head end system to subscribers. By employing bilinear property of pairing and elliptic curve cryptography, our scheme provides one-to-many facility in the case of multiple requests for the same service in a short period of time. This new scheme achieves better broadcast efficiency and performance on communication costs than traditional ones. Additionally, this scheme provides a hand-off authentication mechanism to protect the access of services while preventing attacks during hand-off; therefore, the scheme is more secure to support access control. Moreover, to provide anonymous authentication for protecting identity privacy, the scheme adopts an identity-based scheme while traditional schemes do not apply. The scheme inherits advantages of the identity-based scheme that a public key does not need to be certificated, the certification authority mechanism will not be needed and the key exchange overhead can be reduced. With these advantages of our scheme, it is well suited for mobile pay-TV system.     

A novel hybrid feature selection method for microarray data analysis

Recently, many methods have been proposed for microarray data analysis. One of the challenges for microarray applications is to select a proper number of the most relevant genes for data analysis. In this paper, we propose a novel hybrid method for feature selection in microarray data analysis. This method first uses a genetic algorithm with dynamic parameter setting (GADP) to generate a number of subsets of genes and to rank the genes according to their occurrence frequencies in the gene subsets. Then, this method uses the χ²-test for homogeneity to select a proper number of the top-ranked genes for data analysis. We use the support vector machine (SVM) to verify the efficiency of the selected genes. Six different microarray datasets are used to compare the performance of the GADP method with the existing methods. The experimental results show that the GADP method is better than the existing methods in terms of the number of selected genes and the prediction accuracy.     

A spatial warping method for freeform modeling based on a level-set method

Providing an intuitive and effective tool for freeform geometric modeling is important for product design. We introduce in this paper a level-set based spatial warping method for freeform modeling, allowing shape deformation to be initialed by rigid body transformations of volumetric tools. Intuitive user operations including imprinting, deformation and smoothing are developed to shield the user from the underlying geometric complexity. Unlike mesh-based spatial warping methods, the developed method represents a digital model by implicit distance field data and describes its change of geometry by the level-set method. This guarantees the generation of topologically correct triangular mesh models and circumvents the error-prone remeshing and mesh-repairing processes, thus preventing topological errors such as self-intersections. We present this method with algorithm details, numerical experiments and modeling examples.     

Growth characteristics of hierarchical ZnO structures prepared by one-step aqueous chemical growth

By varying the initial precursor concentrations of (KOH/Zn(NO₃)₂ 6H₂O) without addition of surfactants, the branched nanostructures with different growth characteristics can be obtained. In this study, the growth behavior of the three-dimensional hierarchical structure arrays varied from randomly oriented to well-defined sixfold symmetry by altering pH value of the solution and the related effect of erosion phenomenon have been illustrated. In summary, the hierarchical structures with different morphologies can be obtained on preformed Zn microtips through a simple one-step solution method.     

Null-field BIEM for solving a scattering problem from a point source to a two-layer prolate spheroid

In this paper, the acoustic scattering problem from a point source to a two-layer prolate spheroid is solved by using the null-field boundary integral equation method (BIEM) in conjunction with degenerate kernels. To fully utilize the spheroidal geometry, the fundamental solutions and the boundary densities are expanded by using the addition theorem and spheroidal harmonics in the prolate spheroidal coordinates, respectively. Based on this approach, the collocation point can be located on the real boundary, and all boundary integrals can be determined analytically. In real applications of a two-layer prolate spheroidal structure, it can be applied to simulate the kidney-stone biomechanical system. Here, we consider the confocal structure to simulate the kidney-stone system since its analytical solution can be analytically derived. The parameter study for providing some references in the clinical medical treatment is also considered. To check the validity of the null-field BIEM, a special case of the acoustic scattering problem of a point source by a rigid scatterer is also done by setting the density of the inner prolate spheroid to infinity. Results of the present method are compared with those obtained using the commercial finite element software ABAQUS.     

Exact solutions for plastic responses of orthotropic strain-hardening rotating hollow cylinders

This paper presents exact solutions for plastic responses of plastically orthotropic strain-hardening rotating hollow cylinders. Hill’s yield criterion and the Voce hardening law were adopted. The concept of sequential limit analysis was employed to deal with the strain-hardening behavior by updating the yield criterion and the deformed configuration sequentially. First, exact solutions of the plastic angular velocity were acquired by solving both static and kinematic limit analysis problems. The existence of closed-form exact solutions for some cases was also illustrated. Moreover, the global hardening behavior was analytically evaluated. The corresponding distributions of plastic stress components and equivalent plastic strain were also developed. Second, the elastic–plastic capability of the commercial finite-element code ABAQUS was employed for rigorous validations of analytical solutions. Finally, good agreement is observed between analytical solutions and numerical results.     

Thermoelastic Analysis of Functionally Graded Rotating Disks with Variable Thickness Involving Non-Uniform Heat Source

The research aims to investigate thermoelastic behavior of functionally graded rotating disks with variable thickness involving a non-uniform heat source. We assume material properties and thickness of rotating disks to vary in the radial direction. Axisymmetric thermal loads including non-uniform heat source, heat flux, and temperature boundary conditions are considered. To conduct corresponding simulations, two user subroutines are edited and incorporated into the commercial finite-element code ABAQUS. For verification, analytical formulations are derived and solved uniquely by symbolic calculations using the computing software Mathematica. The developed finite-element technique is then verified with very good agreement between results by ABAQUS and Mathematica.