Low-power multi-threshold MCML: Analysis, design, and variability

The increasing demand on low-power applications is adding pressure on circuit designers to come out with new circuit styles that can decrease power dissipation while making use of the performance improvement of the new CMOS technologies. Multi-threshold MOS current mode logic (MTMCML) appears to be a solution to this problem by making use of the high-performance of MOS current mode circuits while minimizing power dissipation with the help of multi-threshold CMOS technologies. In this work, analytical formulations, based on the BSIM3v3 model, are proposed for MTMCML performance measures with an error within 10% compared to HSPICE. The formulation helps designers to efficiently design MTMCML circuits without undergoing the time-consuming HSPICE simulations. Furthermore, it provides design guidelines and aids for designers to fully understand the different tradeoffs in MTMCML design. In addition, the analysis is extended to study the impact of technology scaling and parameter variations on MTMCML. It is shown that the worst case variation in the minimum supply voltage of MTMCML is 1.16%, thus suggesting maximal power saving.     

Cellular reuse patterns quality and efficiency comparison

Capacity enhancement and interference performance are among the most important issues in the 2nd and 3rd generation cellular networks planning. The main objective of the planning process is to reach a tradeoff between the quality and the capacity of the network. In this paper, we study and compare the CIR and spectral efficiency of different cellular reuse patterns. We also establish the exact analytical PDF expression of CIR assuming one interferer in the serving cell, we then generalize this expression to many interferer tiers. Shadowing effect is also carefully considered in the CIR distribution extension. Moreover, numerical computations are performed to estimate spectral efficiency values for the different patterns studied. Some simulations are also developed to give the comparison a concrete and a practical aspect. A reuse partitioning (RP) capacity scheme is used to serve as the basis of the study. In particular, RP sub‐cells' sizes and number of partitions are optimized in order to maximize the traffic capacity parameterized by spectral and trunking efficiency while involving the financial cost. The efficiency/cost comparison is among the main novel issues contributed by the paper. Copyright © 2006 John Wiley & Sons, Ltd.     

RadiaLE: A framework for designing and assessing link quality estimators in wireless sensor networks

Stringent cost and energy constraints impose the use of low-cost and low-power radio transceivers in large-scale wireless sensor networks (WSNs). This fact, together with the harsh characteristics of the physical environment, requires a rigorous WSN design. Mechanisms for WSN deployment and topology control, MAC and routing, resource and mobility management, greatly depend on reliable link quality estimators (LQEs). This paper describes the RadiaLE framework, which enables the experimental assessment, design and optimization of LQEs. RadiaLE comprises (i) the hardware components of the WSN testbed and (ii) a software tool for setting-up and controlling the experiments, automating link measurements gathering through packets-statistics collection, and analyzing the collected data, allowing for LQEs evaluation. We also propose a methodology that allows (i) to properly set different types of links and different types of traffic, (ii) to collect rich link measurements, and (iii) to validate LQEs using a holistic and unified approach. To demonstrate the validity and usefulness of RadiaLE, we present two case studies: the characterization of low-power links and a comparison between six representative LQEs. We also extend the second study for evaluating the accuracy of the TOSSIM 2 channel model.     

Service selection in stochastic environments: a learning-automaton based solution

In this paper, we propose a novel solution to the problem of identifying services of high quality. The reported solutions to this problem have, in one way or the other, resorted to using so-called “Reputation Systems” (RSs). Although these systems can offer generic recommendations by aggregating user-provided opinions about the quality of the services under consideration, they are, understandably, prone to “ballot stuffing” and “badmouthing” in a competitive marketplace. In general, unfair ratings may degrade the trustworthiness of RSs, and additionally, changes in the quality of service, over time, can render previous ratings unreliable. As opposed to the reported solutions, in this paper, we propose to solve the problem using tools provided by Learning Automata (LA), which have proven properties capable of learning the optimal action when operating in unknown stochastic environments. Furthermore, they combine rapid and accurate convergence with low computational complexity. In addition to its computational simplicity, unlike most reported approaches, our scheme does not require prior knowledge of the degree of any of the above mentioned problems associated with RSs. Instead, it gradually learns the identity and characteristics of the users which provide fair ratings, and of those who provide unfair ratings, even when these are a consequence of them making unintentional mistakes.     

Studies on thermal,mechanical, morphological,and viscoelastic properties of polybenzimidazole fiber reinforced high density polyethylene composites

High density polyethylene (HDPE) and polybenzimidazole fiber (PBI) composites were prepared by melt blending in a twin screw extruder. The thermomechanical properties of PBI fiber reinforced HDPE composite samples (1%, 4%, and 8%) of fiber lengths 3 mm and 6 mm were investigated using differential scanning calorimeter (DSC), universal testing machine, rheometer, and scanning electron microscopy (SEM). The effects of fiber content and fiber lengths on the thermomechanical properties of the HDPE‐PBI composites were studied. The DSC analysis showed a decrease in crystallinity of HDPE‐PBI composites with an increase of fiber loading. SEM images revealed homogeneous distribution of the fibers in the polymer matrix. The thermal behavior of the composites was evaluated from thermogravimetric analysis and the thermal stability was found to increase with the addition of fibers. The evidence of homogeneous distribution was verified by the considerably high values of tensile strength and flexural strength. In the rheology study, the complex viscosities of HDPE‐PBI composites were higher than the HDPE matrix and increased with the increasing of PBI fiber loading. POLYM. COMPOS., 5–13, 2016. © 2014 Society of Plastics Engineers     

Shelf life and safety concerns of bakery products--a review

Bakery products are an important part of a balanced diet and, today, a wide variety of such products can be found on supermarket shelves. This includes unsweetened goods (bread, rolls, buns, crumpets, muffins and bagels), sweet goods (pancakes, doughnuts, waffles and cookies) and filled goods (fruit and meat pies, sausage rolls, pastries, sandwiches, cream cakes, pizza and quiche). However, bakery products, like many processed foods, are subject to physical, chemical and microbiological spoilage. While physical and chemical spoilage limits the shelf life of low and intermediate moisture bakery products, microbiological spoilage by bacteria, yeast and molds is the concern in high moisture products i.e., products with a water activity (a(w)) > 0.85. Furthermore, several bakery products also have been implicated infoodborne illnesses involving Salmonella spp., Listeria monoctyogenes and Bacillus cereus, while Clostridium botulinum is a concern in high moisture bakery products packaged under modified atmospheres. This extensive review is divided into two parts. Part I focuses on the spoilage concerns of low, intermediate and high moisture bakery products while Part II focuses on the safety concerns of high moisture bakery products only. In both parts, traditional and novel methods of food preservation that can be used by the bakery industry to extend the shelf life and enhance the safety of products are discussed in detail.     

Stepped sine wave DC/AC inverter II. Circuit design

This work presents a detailed design and the experimental results of a stepped sine wave DC/AC inverter. The design criterion is to build an inverter of low cost, easy to repair, reliable and of high efficiency. The electronic components used in the inverter are of low cost and commercially available in developing countries. No special components such as toroidal transformers or high cost switching devices are employed. The design with available components enables easy maintenance and short repair periods for the inverter. As a result the inverter reliability increases. Protection circuits against overload, overtemperature of switching devices and low battery voltage are included in the design. A 500 W prototype inverter is built and tested in the laboratory. Good agreement between theory and measurements is observed. The prototype inverter is tested with both resistive and inductive loads and good reliability is observed. An inverter efficiency exceeding 90% is measured.     

Numerical study of a bubble plume generated by bubble entrainment from an impinging jet

The current paper presents the prediction results of a bubbly flow under plunging jet conditions using multiphase mono- and poly-dispersed approaches. The models consider interfacial momentum transfer terms arising from drag, lift, and turbulent dispersion force for the different bubble sizes. The turbulence is modeled by an extended k–? model which accounts for bubble induced turbulence. Furthermore in case of a poly-dispersed air–water flow the bubble size distribution, bubble break-up and coalescence processes as well as different gas velocities in dependency on the bubble diameter are taken into account using the Inhomogeneous MUSIG model. This model is a generalized inhomogeneous multiple size group model based on the Eulerian modeling framework which was developed in the framework of a cooperative work between ANSYS-CFX and Forschungszentrum Dresden-Rossendorf (FZD). The latter is now implemented into the CFD code CFX.According to the correlation on the lateral lift force obtained by Tomiyama (1998); this force changes its sign in dependence on the bubble size. Consequently the entrained small bubbles are trapped below the jet. They can escape from the bubble plume only by turbulent fluctuations or by coalescence. If the size of the bubbles generated by coalescence exceeds the size at which the lift force changes its sign these large bubbles go out from the plume and rise to the surface.A turbulent model based on an additional source term for turbulence kinetic energy and turbulence eddy dissipation equation is compared to the common concept for modeling the turbulence quantities proposed by Sato et al. (1981). It has been found that the large bubble distribution is slightly affected by the turbulence modeling which affects particularly the bubble coalescence and break-up process.