Sparse representation based facial image compression via multiple dictionaries and separated ROI

Multimedia Tools and Applications - Constant increasing of visual information necessitates most efficient image compression schemes for saving storage space or reducing required transmission...     

Providing a Way to Create Balance Between Reliability and Delays in SDN Networks by Using the Appropriate Placement of Controllers

Wireless Personal Communications - Computer networks covered the entire world and a serious and new development has not formed for many years. But companies and consumer organizations complain...     

Virtual Machine Consolidation in Cloud Computing Systems: Challenges and Future Trends

Wireless Personal Communications - Cloud Computing Systems (CCSs) provides a computing capability through the Internet. It enables organizations or individuals to have a computing power without...     

Microwave-assisted combustion synthesis of ZnAl2O4 and ZnO nanostructure particles for photocatalytic wastewater treatment

ZnAl₂O₄ and ZnO nanostructure particles and in situ crystallization of zinc aluminate and zinc oxide coating layers on sintered α-Al₂O₃ and γ-Al₂O₃ granules by the microwave-assisted combustion method were investigated. For powders, the effects of solution pH value and for coated samples the influence of support type on the structure, microstructure, and photocatalytic activity of powders were studied. Results showed that variation of synthesis pH value caused to considerable change in agglomeration, specific surface area, obtaining up to 88 and 92% yields for zinc aluminate and zinc oxide nanoparticles, respectively. γ-alumina granules were more appropriate supports than the α-alumina ones because of the better photocatalytic activities and lower extent of the attritions for both zinc aluminate and zinc oxide coating layers.     

Low-power CMOS distributed amplifier using new cascade gain cell for high and low gain modes

A CMOS distributed amplifier (DA) with low-power and flat and high power gain (S₂₁) is presented. In order to decrease noise figure (NF) an RL terminating network used for the gate transmission line instead of single resistance. Besides, a flat and high S₂₁ is achieved by using the proposed cascade gain cell consist of a cascode-stage with bandwidth extension capacitor. In the high-gain mode, under operation condition of V _dd  = 1.2 V and the overall current consumption of 7.8 mA, simulation result shown that the DA consumed 9.4 mW and achieved a flat and high S₂₁ of 20.5 ± 0.5 dB with an average NF of 6.5 dB over the 11 GHz band of interest, one of the best reported flat gain performances for a CMOS UWB DA. In the low-gain mode, the DA achieved average S₂₁ of 15.5 ± 0.25 dB and an average NF of 6.6 dB with low power consumption (P_DC) of 3.6 mW, the lowest P_DC ever reported for a CMOS DA or LNA with an average gain better than 10 dB.     

Polyurethane-SAPO-34 mixed matrix membrane for CO2/CH4 and CO2/N2 separation

SAPO-34 nanocrystals (inorganic filler) were incorporated in polyurethane membranes and the permeation properties of CO₂, CH_4, and N₂ gases were explored. In this regard, the synthesized PU-SAPO-34 mixed matrix membranes (MMMs) were characterized via SEM, AFM, TGA, XRD and FTIR analyses. Gas permeation properties of PU-SAPO-34 MMMs with SAPO-34 contents of 5 wt%, 10 wt% and 20 wt% were investigated. The permeation results revealed that the presence of 20 wt% SAPO-34 resulted in 4.45%, 18.24% and 40.2% reductions in permeability of CO_2, CH_4, and N₂, respectively, as compared to the permeability of neat polyurethane membrane. Also, the findings showed that at the pressure of 1.2 MPa, the incorporation of 20 wt% SAPO-34 into the polyurethane membranes enhanced the selectivity of CO₂/CH₄ and CO₂/N₂, 14.43 and 37.46%, respectively. In this research, PU containing 20 wt% SAPO-34 showed the best separation performance. For the first time, polynomial regression (PR) as a simple yet accurate tool yielded a mathematical equation for the prediction of permeabilities with high accuracy (R² > 99%).     

Material encapsulation in poly(methyl methacrylate) shell: A review

Material encapsulation is a relatively new technique for coating a micro/nanosize particle or droplet with polymeric or inorganic shell. Encapsulation technology has many applications in various fields including drug delivery, cosmetic, agriculture, thermal energy storage, textile, and self-healing polymers. Poly(methyl methacrylate) (PMMA) is widely used as shell material in encapsulation due to its high chemical stability, biocompatibility, nontoxicity, and good mechanical properties. The main approach for micro/nanoencapsulation of materials using PMMA as shell comprises emulsion-based techniques such as emulsion polymerization and solvent evaporation from oil-in-water emulsion. In the present review, we first focus on the encapsulation techniques of liquid materials with PMMA shell by analyzing the effective processing parameters influencing the preparation of PMMA micro/nanocapsules. We then describe the morphology of PMMA capsules in emulsion systems according to thermodynamic relations. The techniques to investigation of mechanical properties of capsule shell and the release mechanisms of core material from PMMA capsules were also investigated. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48039.     

Preparation and study of thermal properties of phase change materials based on paraffin–alumina‐filled polyethylene

Novel phase change materials based on paraffin and alumina‐filled polyethylene (FPE) were prepared using a two‐step process. In the first step, PE is synthesized using metallocene catalyst system. The synthesized PE is subsequently purified, whereas hydrated alumina–PE composites will be formed by the hydrolysis of aluminum organic cocatalyst and dispersion of hydrated alumina in the PE matrix. In the second step, paraffin–alumina‐FPE composites were prepared by using the ex situ technique. Scanning electron microscopy, X‐ray diffraction, Fourier‐transform infrared spectroscopy, thermogravimetric analysis, and differential scanning calorimetry were used to evaluate the structure and thermal properties of the composites. The results show that the incorporation of a suitable amount of alumina into the composites changes their thermal stability. It is also possible to improve the thermophysical properties of the thermal energy storage materials by altering the paraffin ratio to the FPE. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Thin water films and particle morphology evolution in nanocrystalline MgO

A key question in the field of ceramics and catalysis is how and to what extent residual water in the reactive environment of a metal oxide particle powder affects particle coarsening and morphology. With X‐ray Diffraction (XRD) and Transmission Electron Microscopy (TEM), we investigated annealing‐induced morphology changes on powders of MgO nanocubes in different gaseous H₂O environments. The use of such a model system for particle powders enabled us to describe how adsorbed water that originates from short exposure to air determines the evolution of MgO grain size, morphology, and microstructure. While cubic nanoparticles with a predominant abundance of (100) surface planes retain their shape after annealing to T = 1173 K under continuous pumping with a base pressure of water p(H₂O) = 10^?5 mbar, higher water partial pressures promote mass transport on the surfaces and across interfaces of such particle systems. This leads to substantial growth and intergrowth of particles and simultaneously favors the formation of step edges and shallow protrusions on terraces. The mass transfer is promoted by thin films of water providing a two‐dimensional solvent for Mg²⁺ ion hydration. In addition, we obtained direct evidence for hydroxylation‐induced stabilization of (110) faces and step edges of the grain surfaces.