A performance comparison of measurement matrices in compressive sensing

Compressive sensing involves 3 main processes: signal sparse representation, linear encoding or measurement collection, and nonlinear decoding or sparse recovery. In the measurement process, a measurement matrix is used to sample only the components that best represent the signal. The choice of the measurement matrix has an important impact on the accuracy and the processing time of the sparse recovery process. Hence, the design of accurate measurement matrices is of vital importance in compressive sensing. Over the last decade, a number of measurement matrices have been proposed. Therefore, a detailed review of these measurement matrices and a comparison of their performances are strongly needed. This paper explains the foundation of compressive sensing and highlights the process of measurement by reviewing the existing measurement matrices. It provides a 3‐level classification and compares the performance of 8 measurement matrices belonging to 4 different types using 5 evaluation metrics: the recovery error, processing time, recovery time, covariance, and phase transition diagram. The theoretical performance comparison is validated with experimental results, and the results show that the Circulant, Toeplitz, and Hadamard matrices outperform the other measurement matrices.     

Long‐term microstructural changes in solid oxide fuel cell anodes: 3D reconstruction

Microstructural changes in solid oxide fuel cell anodes after long‐term operation have been characterized by sequential sectioning with a focused ion beam, followed by scanning electron microscopy imaging and three‐dimensional reconstruction. The anodes were porous composites of Ni and Y₂O₃‐stabilized ZrO₂ (YSZ). The cells were operated at 800°C for 2, 4, and 8 kh, and at 925°C for 2 and 4 kh. For each specimen, the volume fraction, surface area, particle diameter, and tortuosity have been calculated for each phase (Ni, YSZ, and pores). The dependence of these microstructural parameters on the volume of sample analyzed was monitored; sufficiently large volumes were analyzed so as to eliminate any effect of sample volume. Gradients in volume fraction of Ni and porosity developed during fuel cell operation, with Ni fraction increasing, and pore fraction decreasing, at the electrolyte/anode interface. The magnitudes of these gradients increased with time.     

Soil burial degradation of new bio‐based additives. Part II. plasticized poly(vinyl chloride) films

Commercial sunflower oil was epoxidized, and the epoxidized oil (ESO) was used as a new thermal stabilizer for poly(vinyl chloride) (PVC). Plasticized formulations stabilized with ESO and epoxidized soya bean oil as a commercial stabilizer were evaluated for comparison. Two plasticizers were used, dioctyl phthalate and diisononyl adipate. The aging of the PVC samples was investigated in landfill soil for 24 months. The modifications of the structure of the polymer were followed by Fourier, transform infrared spectroscopy. Furthermore, the variations of density and mechanical properties (tensile and Shore D hardness) were considered, and the variations of the mass of the samples, the glass transition temperature (T_g), the molar mass distribution, and the weight loss were followed as a function of duration of soil burial. The morphological changes were tracked by scanning electron microscopy. Results showed that the nature of the plasticizer and heat stabilizer affects the properties of PVC as well as the phenomena of migration and biodegradation. J. VINYL ADDIT. TECHNOL., 19:183‐191, 2013. © 2013 Society of Plastics Engineers     

Low Power Circuit and System Design Hierarchy and Thermal Reliability of Tunnel Field Effect Transistor

Silicon - Tunnel FET is one of the promising devices advocated as a replacement of conventional MOSFET to be used for low power applications. Temperature is an important factor affecting the...     

Influence of polluted atmospheres on the natural aging of poly(vinyl chloride) stabilized with epoxidized sunflower oil

Semirigid and plasticized poly(vinyl chloride) (PVC) samples, stabilized with epoxidized sunflower oil (ESO), Zn, and Ca stearates, were exposed in Algiers (hot, Mediterranean climate) for 12 months in three sites where the concentrations of atmospheric pollutants (NO_x, O₃, hydrocarbons) are known. The evolution of the mechanical properties (tensile test and shore D hardness) was followed according to the aging time. The modification structure of polymer was investigated by Fourier transform infrared spectroscopy. The results have shown that all the considered properties were affected. Furthermore, it seems that the O₃ exerted the most deleterious effect, followed by hydrocarbons and then by NO_x. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Transverse compression behavior of textile rovings: finite element simulation and experimental study

Results from finite element simulation of the transverse compression of Polyamide 6.6 rovings made of 40 filaments are compared in this paper against experimental data. The finite element simulation, using a finite strain beam model to represent each filament of the roving, focuses on the modeling of contact–friction interactions between filaments. Experimental tests, consisting in crushing rovings between two rigid planes, varying the twist and the tensile force, are reproduced by simulation. Experimental and simulation results are compared with a good agreement. The simulation studies the influence of the roving twist, the applied tensile force, and the friction coefficient on the transverse compression behavior. The occurrence of plateaus in the transverse compression curve is highlighted and discussed.     

Poly(2‐(dimethylamino)ethyl methacrylate) Brushes with Incorporated Nanoparticles as a SERS Active Sensing Layer

A simple, fast, and versatile approach to the fabrication of outstanding surface enhanced Raman spectroscopy (SERS) substrates by exploiting the optical properties of the Ag nanoparticles and functional as well as organizational characteristics of the polymer brushes is reported. First, poly(2‐(dimethylamino)ethyl methacrylate) brushes are synthesized directly on glassy carbon by self‐initiated photografting and photopolymerization and thoroughly characterized in terms of their thickness, wettability, morphology, and chemical structure by means of ellipsometry, contact angle, AFM, and XPS, respectively. Second, Ag nanoparticles are homogeneously immobilized into the brush layer, resulting in a sensor platform for the detection of organic molecules by SERS. The surface enhancement factor (SEF) as determined by the detection of Rhodamine 6G is calculated as 6 × 10⁶.     

Electrochemically deposited poly(3,4-propylenedioxythiophene) for dye-sensitized solar cell

Journal of Applied Electrochemistry - In this work, poly(3,4-propylenedioxythiophene) (PProDOT)-based counter electrode (CE) was elaborated. The PProDOT polymer was electropolymerized by using...     

Elaboration and characterization of bioblends based on PVC/PLA

With the aim to develop new biomaterials (bioblends) to be used in the field of waste elimination, this contribution focuses on the elaboration and characterization of new materials based on poly (vinyl chloride) (PVC) and poly (lactic acid) (PLA). The bioblends based on PVC/PLA were prepared by melt mixing in the absence and presence of maleic anhydride (MAH). The binary blends were first characterized in terms of thermal (glass transition temperature) and mechanical properties (tensile and micro‐hardness). Their thermal stability was investigated by thermogravimetric analysis (TGA). The results showed that this pair of polymers is not miscible and exhibited lower properties than those of the separated polymers. The in situ compatibilization was then performed using MAH and dicumyl peroxide (DCP) as an initiator. The presence of MAH enhanced the processability of the bioblends by decreasing the temperature of mixing. The properties of subsequent PVC/PLA bioblends were investigated through tensile and micro‐hardness testing, thermal analysis (DSC and TGA), and SEM. From the mechanical results, high level of compatibility was found when introducing MAH. The TGA studies indicated that the incorporation of PLA in PVC (matrix) increased thermal stability of the bioblend. Microscopic observations revealed uniformly dispersed PLA in the PVC matrix, confirming that phase separation has disappeared in the presence of MAH. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40045.