Distributed topology control in large‐scale hybrid RF/FSO networks: SIMT GPU‐based particle swarm optimization approach

The tremendous power of graphics processing unit (GPU) computing relative to prior CPU‐only architectures presents new opportunities for efficient solutions of previously intractable large‐scale optimization problems. Although most previous work in this field focused on scientific applications in the areas of medicine and physics, here we present a Compute Unified Device Architecture‐based (CUDA) GPU solution to solve the topology control problem in hybrid radio frequency and free space optics wireless mesh networks by adapting and adjusting the transmission power and the beam‐width of individual nodes according to QoS requirements. Our approach is based on a stochastic global optimization technique inspired by the social behavior of flocking birds — so‐called ‘particle swarm optimization’ — and was implemented on the NVIDIA GeForce GTX 285 GPU. The implementation achieved a performance speedup factor of 392 over a CPU‐only implementation. Several innovations in the memory/execution structure in our approach enabled us to surpass all prior known particle swarm optimization GPU implementations. Our results provide a promising indication of the viability of GPU‐based approaches towards the solution of large‐scale optimization problems such as those found in radio frequency and free space optics wireless mesh network design. Copyright © 2011 John Wiley & Sons, Ltd.     

Extension of the Reiner–Riwlin equation to determine modified Bingham parameters measured in coaxial cylinders rheometers

The determination of the exact rheological properties, in fundamental units, of cementitious materials has become gradually a necessary step in the domain of concrete science. Several types of rheometers and their corresponding transformation equations are described in the literature. In this paper, the Reiner–Riwlin transformation equation, valid for coaxial cylinders rheometers, is developed for the modified Bingham model, which is an extension of the Bingham model with a second order term in the shear rate. The established transformation is shown to be compatible with the Reiner–Riwlin equation for the Bingham and Herschel–Bulkley models. Its validation is further proven by means of numerical simulations applied on experimental data. The yield stress values for the three rheological models (applied on the same experimental data) are compared with the yield stress calculated by means of slump flow values. Results showed that the modified Bingham model results in the most stable yield stress values, which are independent of the non-linear behaviour.     

Application of the Finite-Volume Method to Study the Effects of Baffles on Radiative Heat Transfer in Complex Enclosures

A finite-volume radiation model for participating gray media in 2-D and 3-D complex rectangular enclosures with obstacles is developed. The step and the bounded high-order resolution curved-line advection method (CLAM) schemes are examined. Using the blocked-off-region procedure, the present model is capable of predicting radiative heat transfer in enclosures with obstructions and baffles. In order to validate the formulations derived here a square cavity with one or three baffles and finned internal cylinder, then a three-dimensional complex heat recuperator of a pilot plant of biomass pyrolysis with obstructions and baffles, are studied. It should be pointed out that the developed code using the CLAM scheme is accurate and convenient for computational thermal calculations. For the considered heat recuperator, the presence of baffles enhances radiative heat flux and contributes to the increase of the mean medium temperature.     

Exponential localization of moving end mirror in optomechanics

We discuss the dynamics of moving end mirror of an optomechanical system that consists of a Fabry-Perot cavity loaded with dilute condensate and driven by a single-mode optical field. It is shown that quantum mechanical phenomenon of dynamical localization occurs both in position and momentum space for moving end mirror in the system. The parametric dependencies of dynamical localization are discussed. We also provide a set of parameters which makes this phenomenon experimentally feasible.     

In vitro study of nano-sized zinc doped bioactive glass

Surface reactivity in physiological fluid has been linked to bioactivity of a material. Past research has shown that bioactive glass containing zinc has the potential in bone regeneration field due to its enhanced bioactivity. However, results from literature are always contradictory. Therefore, in this study, surface reactivity of bioactive glass containing zinc was evaluated through the study of morphology and composition of apatite layer formed after immersion in simulated body fluid (SBF). Nano-sized bioactive glass with 5 and 10 mol% zinc were synthesized through quick alkali sol–gel method. The synthesized Zn–bioglass was characterized using field emission scanning electron microscope (FESEM), energy dispersive X-ray spectrometer (EDX), X-ray diffractometer (XRD) and Fourier transform infrared spectrometer (FTIR). Samples after SBF immersion were characterized using scanning electron microscope (SEM) and EDX. Morphological study through SEM showed the formation of spherical apatite particles with Ca/P ratio closer to 1.67 on the surface of 5 mol% Zn–bioglass. Whereas, the 10 mol% Zn–bioglass samples induced the formation of flake-like structure of calcite in addition to the spherical apatite particles with much higher Ca/P ratio. Our results suggest that the higher Zn content increases the bioactivity through the formation of bone-bonding calcite as well as the spherical apatite particles.     

Reduction of fuel consumption in gasoline engines by introducing HHO gas into intake manifold

Brown’s gas (HHO) has recently been introduced to the auto industry as a new source of energy. The present work proposes the design of a new device attached to the engine to integrate an HHO production system with the gasoline engine. The proposed HHO generating device is compact and can be installed in the engine compartment. This auxiliary device was designed, constructed, integrated and tested on a gasoline engine.     

Security issues and solutions in multicast content distribution: a survey

Multicast enables efficient large-scale content distribution by providing an efficient transport mechanism for one-to-many and many-to-many communication. The very properties that make multicast attractive, however, also make it a challenging environment in which to provide content security. We show how the fundamental properties of the multicast paradigm cause security issues and vulnerabilities. We focus on four areas of research in security for multicast content distribution: receiver access control, group key management, multicast source authentication, and multicast fingerprinting. For each we explain the vulnerabilities, discuss the objectives of solutions, and survey work in the area. Also, we briefly highlight other security issues in multicast content distribution including source access control, secure multicast routing, and group policy specification. We then outline several future research directions.     

Multicast server selection: problems, complexity, and solutions

We formulate and investigate fundamental problems that arise when multicast servers, that deliver content to multiple clients simultaneously, are replicated to enhance scalability and performance. Our study consists of two parts. First, we consider the problem under the assumption that the multicast clients are static for the duration of the multicast content distribution session. In this context, we examine two models for server behavior: fixed-rate servers, which transmit at a constant rate, and rate-adaptive servers, which adapt their transmission rate based on network conditions and/or feedback from clients. In both cases, we show that general versions of the client assignment problems are NP-hard. We then develop and evaluate efficient algorithms for interesting special cases, as well as heuristics for general cases. Second, we consider the case in which the set of clients changes dynamically during the multicast content distribution session. We again consider both fixed-rate and rate-adaptive servers. We formulate the problem as a Markov decision process, capturing the costs associated with trees, as well as the transition costs to dynamically change the trees. We use the properties of optimal solutions for small examples to develop a set of dynamic server selection heuristics.     

Comments on "Modeling TCP reno performance: a simple model and its empirical Validation"

In this Comments, several errors in Padhye , 2000, are pointed out. The more serious of these errors result in an over prediction of the send rate. The expression obtained for send rate in this Comments leads to greater accuracy when compared with the measurement data than the originals end rate expression in Padhye et al.