Improvement in energy conversion of electrostrictive composite materials by new approach via piezoelectric effect: Modeling and experiments

This study proposes a new model that couples the piezoelectric and electrostrictive behavior to minimize the polarization power of composite polymer. The development of this model is capable to predict the energy harvesting abilities of an electrostrictive composite. To improve the dielectric permittivity of electrostrictive polymer, the particles of PZT have been incorporated in order to increase the conversion efficiency of the composite. Dielectric characterization tests showed an increase in dielectric permittivity by a factor of 4.5 compared to pure polymer. Experimental measurements of harvested power validate the analytical model and demonstrate a good correlation between the two data. An equivalent of an electrical scheme has been developed, which allows modeling the two behaviors. The harvested power density under low frequency at 2% of strain can reach 0.30 μW/cm³ for 33% of PZT without the polarization field, including the conversion efficiency becomes higher. The energy harvester property of this material composite has excellent potential for several self‐powered applications such as wireless sensor networks and the internet of things.     

Performances comparison between multilevel hierarchical and mesh FPGA interconnects

This paper evaluates a new multilevel hierarchical FPGA (MFPGA). The specific architecture includes two unidirectional programmable networks: a downward network based on the Butterfly-Fat-Tree topology; and a special upward network. New tools are developed to place and route several benchmark circuits on this architecture. Comparison with the traditional symmetric Manhattan mesh architecture shows that MFPGA can implement circuits with a smaller area and better speed.     

Exploration and optimization of a homogeneous tree-based application specific inflexible FPGA

An Application Specific Inflexible FPGA (ASIF) is a modified form of an FPGA which is designed for a predefined set of applications that operate at mutually exclusive times. An ASIF is a compromise between FPGAs and Application Specific Integrated Circuits (ASICs). Compared to an FPGA, an ASIF has reduced flexibility and improved density while compared to an ASIC, it has larger area but improved flexibility. This work presents a new homogeneous tree-based ASIF and uses a set of 16 MCNC benchmarks for experimentation. Experimental results show that, on average, a homogeneous tree-based ASIF gives 64% area gain when compared to an equivalent tree-based FPGA. Further, the experiments are performed to explore the effect of look-up table (LUT) and arity size on a tree-based ASIF. Later, comparison between tree and mesh-based ASIF is performed and results show that tree-based ASIF is 12% smaller in terms of routing area and consumes 77% less wires than mesh-based ASIF. Finally the quality comparison between two ASIFs reveals that, on average, tree-based ASIF gives 33% area gain as compared to mesh-based ASIF.     

Geometric representation of the mean–variance–skewness portfolio frontier based upon the shortage function

The literature suggests that investors prefer portfolios based on mean, variance and skewness rather than portfolios based on mean–variance (MV) criteria solely. Furthermore, a small variety of methods have been proposed to determine mean–variance–skewness (MVS) optimal portfolios. Recently, the shortage function has been introduced as a measure of efficiency, allowing to characterize MVS optimal portfolios using non-parametric mathematical programming tools. While tracing the MV portfolio frontier has become trivial, the geometric representation of the MVS frontier is an open challenge. A hitherto unnoticed advantage of the shortage function is that it allows to geometrically represent the MVS portfolio frontier. The purpose of this contribution is to systematically develop geometric representations of the MVS portfolio frontier using the shortage function and related approaches.     

Mineralization of aqueous phenolate solutions: A combination of irradiation treatment and wet oxidation

Wet oxidation (high-temperature, high-pressure oxidation of organic wastes in aqueous solution) and radiation technology were combined in γ-ray and electron beam induced oxidation of 4×10^?4–1×10^?2 mol dm^?3 Na-phenolate solutions in a wide O₂ concentration (1–20 bar pressure) and absorbed dose (0–50 kGy) range. Most experiments were made in stainless steel high pressure autoclave equipped with magnetic stirrer. The rate of oxidation was followed by chemical oxygen demand and total organic carbon content measurements. The rate was similar in γ-ray and pulsed electron beam irradiation and increased with O₂ concentration in the liquid.     

Analogues of Miyachi, cowling-price and Morgan theorems for compact extensions of ℝ n

Let K be a compact subgroup of automorphisms of ? ⁿ . We formulate and prove an analogue of Miyachi’s theorem for the semi-direct product K ? ? ⁿ . This allows us to solve the sharpness problems in the theorem of Cowling-Price and in the L ^p ? L ^q analogue of Morgan theorem for any compact extension of ? ⁿ . These upshots are proved using the representations theory and the Plancherel formula for the group Fourier transform.     

Generalized logarithmic Gauss map and its relation to (co)amoebas

We define the generalized logarithmic Gauss map for algebraic varieties of the complex algebraic torus of any codimension. Moreover, we describe the set of critical points of the logarithmic mapping restricted to our variety, and we show an analogous of Mikhalkin's result on the critical points of the logarithmic map restricted to a hypersurface.     

WCDS‐DCR: an energy‐efficient data‐centric routing scheme for wireless sensor networks

Wireless sensor networks (WSNs) typically consist of a large number of battery‐constrained sensors often deployed in harsh environments with little to no human control, thereby necessitating scalable and energy‐efficient techniques. This paper proposes a scalable and energy‐efficient routing scheme, called WCDS‐DCR, suitable for these WSNs. WCDS‐DCR is a fully distributed, data‐centric, routing technique that makes use of an underlying clustering structure induced by the construction of WCDS (Weakly Connected Dominating Set) to prolong network lifetime. It aims at extending network lifetime through the use of data aggregation (based on the elimination of redundant data packets) by some particular nodes. It also utilizes both the energy availability information and the distances (in number of hops) from sensors to the sink in order to make hop‐by‐hop, energy‐aware, routing decisions. Simulation results show that our solution is scalable, and outperforms existing schemes in terms of network lifetime. Copyright © 2010 John Wiley & Sons, Ltd.     

Benchmarking mean-variance portfolios using a shortage function: the choice of direction vector affects rankings!

In addition to its use in data envelopment analysis models, the shortage function has been proposed as a tool to gauge performance in multi-moment portfolio models. An open issue is how the choice of direction vector affects the efficiency measurement, especially when some of the data can be negative and, from a practical point of view, whether and how the resulting league tables are affected. This paper illustrates empirically how the choice of direction vector affects the relative ranking of mean-variance portfolios. This result is relevant to all frontier-based applications, especially those where some of the data can be naturally negative.