An Evaluation of Architectural Platforms for Parallel Navier-Stokes Computations

We study the computational, communication, and scalability characteristics of a computational fluid dynamics application, which solves the time-accurate flow field of a jet using the compressible Navier-Stokes equations, on a variety of parallel architectural platforms. The platforms chosen for this study are a cluster of workstations (the LACE experimental testbed at NASA Lewis), a shared-memory multiprocessor (the CRAY Y-MP), and distributed-memory multiprocessors with different topologies (the IBM SP and the CRAY T3D). We investigate the impact of various networks connecting the cluster of workstations on the performance of the application and the overheads induced by popular message-passing libraries used for parallelization. The work also highlights the importance of matching the memory bandwidth to processor speed for good single processor performance. By studying the performance of an application on a variety of architectures, we are able to point out the strengths and weaknesses of each of the example computing platforms. This revised version was published online in June 2006 with corrections to the Cover Date.     

Novel miniaturized folded UWB microstrip antenna‐based metamaterial for RF energy harvesting

This paper presents a design of an ultra‐wideband (UWB) cylindrical metamaterial (MTM) antenna for radio frequency (RF) energy harvesting to suit the fields of Internet of Things (IoT) applications. The patch circuitry is based on 3×5 Hilbert‐shaped MTM unit cells array to enhance the antenna bandwidth. While, the antenna ground plane is defected with an electromagnetic band gap structure to enhance the gain. The antenna is mounted on a polytetrafluoroethylene cylindrical substrate of an outer diameter of 15 mm and length of 32 mm with 1 mm in thickness. The substrate relative permittivity is 2.04, and the loss tangent is 0.0002. The antenna patch and the ground plane structures are printed with silver nanoparticles ink using a ^2.5D CNC plotter machine. The fabricated prototype provides an UWB over the frequency range from 3.77 up to 13.89 GHz with a first separate resonant mode at 3 GHz. The antenna performance is tested numerically using two different software packages of CST MWS and HFSS. Then, an experimental validation is conducted to realize the performance of the proposed antenna in harvesting the RF energy. Excellent conversion efficiency, about 90%, is achieved at 5.8 GHz. Finally, the antenna radiation patterns and S₁₁ spectrum are measured and compared against their simulated results to achieve good agreements.     

Congestion control in wireless sensor and 6LoWPAN networks: toward the Internet of Things

The Internet of Things (IoT) is the next big challenge for the research community where the IPv6 over low power wireless personal area network (6LoWPAN) protocol stack is a key part of the IoT. Recently, the IETF ROLL and 6LoWPAN working groups have developed new IP based protocols for 6LoWPAN networks to alleviate the challenges of connecting low memory, limited processing capability, and constrained power supply sensor nodes to the Internet. In 6LoWPAN networks, heavy network traffic causes congestion which significantly degrades network performance and impacts on quality of service aspects such as throughput, latency, energy consumption, reliability, and packet delivery. In this paper, we overview the protocol stack of 6LoWPAN networks and summarize a set of its protocols and standards. Also, we review and compare a number of popular congestion control mechanisms in wireless sensor networks (WSNs) and classify them into traffic control, resource control, and hybrid algorithms based on the congestion control strategy used. We present a comparative review of all existing congestion control approaches in 6LoWPAN networks. This paper highlights and discusses the differences between congestion control mechanisms for WSNs and 6LoWPAN networks as well as explaining the suitability and validity of WSN congestion control schemes for 6LoWPAN networks. Finally, this paper gives some potential directions for designing a novel congestion control protocol, which supports the IoT application requirements, in future work.

     

Universal Adaptive Differential Protection for Regulating Transformers

Since regulating transformers have proved to be efficient in controlling the power flow and regulating the voltage, they are more and more widely used in today's environment of energy production, transmission and distribution. This changing environment challenges protection engineers as well to improve the sensitivity of protection, so that low-current faults could be detected (like turn-to-turn short circuits in transformer windings) and a warning message could be given. Moreover, the idea of an adaptive protection that adjusts the operating characteristics of the relay system in response to changing system conditions has became much more promising. It improves the protection sensitivity and simplifies its conception. This paper presents an adaptive adjustment concept in relation to the position change of the on load tap changer for universal differential protection of regulating transformers; such a concept provides a sensitive and cost-efficient protection for regulating transformers. Various simulations are carried out with the Electro-Magnetic Transients Program/Alternative Transients Program. The simulation results indicate the functional efficiency of the proposed concept under different fault conditions; the protection is sensitive to low level intern faults. The paper concludes by describing the software implementation of the algorithm on a test system based on a digital signal processor.     

Linear-Complexity Models for Wireless MAC-to-MAC Channels

Wireless local area networks suffer from frequent bit-errors that result in Medium Access Control (MAC) layer packet drops. Bandwidth and media quality constraints of real-time applications necessitate analysis and modeling at the “MAC-to-MAC wireless channel”. In this paper, we propose and evaluate stochastic models for the 802.11b MAC-to-MAC bit-error process. We propose an Entropy Normalized Kullback-Leibler (ENK) measure to accurately evaluate the performance of the models. We employ this measure to demonstrate that the traditional full-state Markov chains of order-10 and order-9 are required for accurate representation of the channel at 2 and 5.5 Mbps, respectively. However, the complexity of this modeling paradigm increases exponentially with respect to the order. For many real-time and non-real-time applications, which require (or could benefit significantly from) accurate modeling, the high complexity of full-state high-order Markov models makes them impractical or virtually ineffective. Thus, we propose two new linear-complexity models, which we refer to as the short-term energy model (SEM) and the zero-crossing model (ZCM). These models, which constitute the most important contribution of this paper, constrain the complexity to increase linearly with the model order. We illustrate that the linear-complexity models, while yielding orders of magnitude reduction in complexity, provide a performance comparable to that of the exponential complexity full-state models. Within the linear-complexity context, we illustrate that the zero-crossing model perform better than its short-term energy counterpart. Finally, for varying window sizes and due to its low complexity, we show that the zero-crossing model can be adapted in real-time. Such an adaptive model provides accurate channel modeling and characterization for rate adaptive applications.Syed Ali Khayam received the B.S. degree in computer systems engineering from National University of Sciences and Technology (NUST) Pakistan in 1999. He secured the Pakistan Higher Education Commission M.S./Ph.D. scholarship to pursue post graduate studies at Michigan State University (MSU). He completed his M.S. in Electrical Engineering from MSU in 2003. He is currently a Ph.D. candidate in the Department of Electrical and Computer Engineering at MSU. He also worked at Communications Enabling Technologies where he led a design team which realized various modules of a Voice-over-IP system-on-chip. His research interests include statistical analysis and modeling of computer (and in particular wireless) networks, network security, cross-layer protocol design, real-time multimedia communications over IP-based networks, and VLSI chip design.Hayder Radha received the B.S. degree (with honors) from Michigan State University (MSU) in 1984, the M.S. degree from Purdue University in 1986, and the Ph.M. and Ph.D. degrees from Columbia University in 1991 and 1993 (all in electrical engineering). He joined MSU in 2000 as Associate Professor in the Department of Electrical and Computer Engineering. Between 1996 and 2000, Dr. Radha worked at Philips Research USA where he initiated the Internet Video project and led a team of researchers working on scalable video coding and streaming algorithms. Dr. Radha is a Philips Research Fellow. Prior to working at Philips, Hayder Radha was a Distinguished Member of Technical Staff at Bell Labs where he worked between 1986 and 1996 in the areas of digital communications, signal/image processing, and broadband multimedia. His research interests include image and video coding, wireless technology, multimedia communications and networking. He has more than 20 patents in these areas. Dr. Radha served as Co-Chair and Editor of the ATM and LAN Video Coding Experts Group of the ITU-T in 1994–1996.     

On enabling cooperative communication and diversity combination in IEEE 802.15.4 wireless networks using off-the-shelf sensor motes

This paper presents the ‘Generalized Poor Man’s SIMO System’ (gPMSS) which combines two approaches, cooperative communication and diversity combination, to reduce packet losses over links in wireless sensor networks. The proposed gPMSS is distinct from previous cooperative communication architectures in wireless sensor networks which rely on a relay channel, and also distinct from implementations in 802.11 networks that require a wired infrastructure or hardware changes for cooperation. gPMSS foregoes the need for any changes to mote hardware and it works within the current IEEE 802.15.4 standard. We describe the gPMSS protocol that governs the cooperation between receivers. Three variants are evaluated including selection diversity, equal gain and maximal ratio combining. First, we demonstrate gPMSS on bit error traces in a fully reproducible manner. This is followed by an implementation of gPMSS in C# on the .NET Micro Framework edition of the recently released Imote2 mote platform. We demonstrate by means of experiments an increase in the packet reception rate from 22–30% to 73–76%, a relative increase of 150–245%. We also analyzed the power consumed by the transmitter per delivered packet and observe a reduction of up to 68%. We also take into account the retry limit of the IEEE 802.15.4 protocol and demonstrate that gPMSS is able to provide 99% packet delivery at the protocol’s default retry parameters against 65–75% without it.     

Synthesis of Organic Functionalized Silica from Rice Husk as an Antibacterial Agents

Silicon - In the present study, silica-aminothiazole (RHAC-ATH) and silica-aminophenol (RHAC-AMPH) have been prepared and characterized by different techniques. Fourier-Transform Infrared (FTIR)...     

Exploring the Design and Spectroscopic Characteristics of PVA/Si3N4/SiBr4 New Structures for Electronics and Optics Devices

Silicon - This work aims to design of silicon nitride (Si3N4) and silicon bromide (SiBr4) doped polyvinyl alcohol (PVA) as promising semiconductors materials which can be used in various...