New Approaches for Estimation of Monthly Rainfall Based on GEP-ARCH and ANN-ARCH Hybrid Models

Accurate estimation of rainfall has an important role in the optimal water resources management, as well as hydrological and climatological studies. In the present study, two novel types of hybrid models, namely gene expression programming-autoregressive conditional heteroscedasticity (GEP-ARCH) and artificial neural networks-autoregressive conditional heteroscedasticity (ANN-ARCH) are introduced to estimate monthly rainfall time series. To fulfill this purpose, five stations with various climatic conditions were selected in Iran. The lagged monthly rainfall data was utilized to develop the different GEP and ANN scenarios. The performance of proposed hybrid models was compared to the GEP and ANN models using root mean square error (RMSE) and coefficient of determination (R²). The results show that the proposed GEP-ARCH and ANN-ARCH models give a much better performance than the GEP and ANN in all of the studied stations with various climates. Furthermore, the ANN-ARCH model generally presents better performance in comparison with the GEP-ARCH model.     

Polymer Encapsulants Incorporating Light‐Guiding Architectures to Increase Optical Energy Conversion in Solar Cells

The fabrication of a new type of solar cell encapsulation architecture comprising a periodic array of step‐index waveguides is reported. The materials are fabricated through patterning with light in a photoreactive binary blend of crosslinking acrylate and urethane, wherein phase separation induces the spontaneous, directed formation of broadband, cylindrical waveguides. This microstructured material efficiently collects and transmits optical energy over a wide range of entry angles. Silicon solar cells comprising this encapsulation architecture show greater total external quantum efficiencies and enhanced wide‐angle light capture and conversion. This is a rapid, straightforward, and scalable approach to process light‐collecting structures, whereby significant increases in cell performance may be achieved.     

Green synthesis of ZnO and ZnO/CuO nanocomposites in <Emphasis Type="Italic">Mentha longifolia</Emphasis> leaf extract: characterization and their application as anti-bacterial agents

In this work, we fabricated ZnO and ZnO/CuO nanocomposites using Mentha longifolia leaf extract as a natural, non-toxic, and efficient stabilizer. Anti-bacterial activities of the prepared samples against two pathogenic bacteria, Escherichia coli (Gram-negative), and Staphylococcus aureus (Gram-positive) were investigated. The properties of the as-prepared samples were characterized by XRD, EDX, SEM, TEM, TGA, FT-IR, UV–Vis DRS, and BET instruments. The XRD analysis indicated that the size of crystallites was decreased for the ZnO powder prepared in the presence of the leaf extract. The SEM images showed that the samples consist of spherical shaped well-distributed particles. In addition, the presence of biomolecules from the leaf extract was revealed by EDX, TGA, FT-IR, and UV–Vis DRS analyses, which are important in biosynthesis process. The highest anti-bacterial activity belonged to the ZnO/CuO (10%) nanocomposite and the other compounds, including ZnO/CuO (5%), ZnO (ext), and ZnO (W) were in the next ranks, respectively. It was observed that the viability percentages against E. coli (10.16?±?2.2) is higher than that of S. aureus (17.1?±?0.87) in the presence of the ZnO/CuO (10%) nanocomposite. Ultimately, the mechanism for the action of the ZnO/CuO (10%) nanocomposite was explored through the SEM images, which involved the disruption of the bacterial membranes.     

Photocatalytic decomposition of VOCs by AC–TiO2 and EG–TiO2 nanocomposites

Clean Technologies and Environmental Policy - In this study, TiO2 nanoparticles (NPs)-based catalysts were prepared for the photocatalytic removal of toluene as a model VOC from air under UV light....     

Nanocrystalline samarium tungstate: facile morphology-controlled preparation,characterization and investigation of optical and photocatalytic properties

In the current study, samarium tungstate Sm₂(WO₄)₃ nanoparticles were synthesized via a new route based on the reaction between samarium nitrate hexahydrate and sodium tungstate dihydrate in an aqueous solution. Besides, three amino acids such as cysteine, alanine, and glycine were introduce as capping agents and their effects on the morphology and particle size of Sm₂(WO₄)₃ were investigated. It was found that size and morphology could be easily realized by changing the type of amino acids. XRD, SEM, EDS, and UV–Vis spectroscopy were employed to characterize structural, morphological, and optical properties of Sm₂(WO₄)₃ nanoparticles. Sm₂(WO₄)₃ nanoparticles indicated a paramagnetic behavior at room temperature, as evidenced by using vibrating sample magnetometer. Furthermore, the photocatalytic properties of as synthesized Sm₂(WO₄)₃ were evaluated by degradation of methyl orange as water contaminant.     

Morphology and barrier mechanism of biaxially oriented poly(ethylene terephthalate)/poly(ethylene 2,6‐naphthalate) blends

To improve the barrier properties of poly(ethylene terephthalate) (PET), PET/poly(ethylene 2,6‐naphthalate) (PEN) blends with different concentrations of PEN were prepared and were then processed into biaxially oriented PET/PEN films. The air permeability of bioriented films of pure PET, pure PEN, and PET/PEN blends were tested by the differential pressure method. The morphology of the blends was studied by scanning electron microscopy (SEM) observation of the impact fracture surfaces of extruded PET/PEN samples, and the morphology of the films was also investigated by SEM. The results of the study indicated that PEN could effectively improve the barrier properties of PET, and the barrier properties of the PET/PEN blends improved with increasing PEN concentration. When the PEN concentration was equal to or less than 30%, as in this study, the PET/PEN blends were phase‐separated; that is, PET formed the continuous phase, whereas PEN formed a dispersed phase of particles, and the interface was firmly integrated because of transesterification. After the PET/PEN blends were bioriented, the PET matrix contained a PEN microstructure consisting of parallel and extended, separate layers. This multilayer microstructure was characterized by microcontinuity, which resulted in improved barrier properties because air permeation was delayed as the air had to detour around the PEN layer structure. At a constant PEN concentration, the more extended the PEN layers were, the better the barrier properties were of the PET/PEN blends. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1309–1316, 2006     

A study on the effect of compositing silver oxide nanoparticles by carbon on the ‎electrochemical behavior and electronic properties of zinc‐silver oxide batteries ‎

In this study, the effect of compositing silver oxide nanoparticles by carbon on the electrochemical behavior and electronic properties of zinc‐silver oxide batteries have been investigated. For this purpose, firstly four silver oxide electrodes containing 5, 10, 15, and 20 wt% carbon powder were produced by powder metallurgy method. For the next step, all four silver oxide electrodes were sintered at 500°C for 10 minutes. Afterward and in order to investigate the microstructure, phase and elemental analysis of the electrodes were carried out using Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), X‐ray Diffraction (XRD), and Energy Dispersive Spectroscopy (EDS), respectively. Moreover, in order to investigate the effect of compositing silver oxide nanoparticles by carbon on the electrochemical behavior and electronic properties of zinc‐silver oxide, electrochemical tests (potentiodynamic polarization and electrochemical impedance spectroscopy) and electric discharge test in 1.4 wt%KOH electrolyte were carried out respectively. The microstructural observations revealed that increasing carbon content in the silver oxide electrodes results in increasing the apparent porosities in these electrodes. Investigating the phase and elemental analysis results showed that by increasing the content of carbon in the silver oxide electrode, the amount of Ag₂O and AgO phases in this electrode reduces and also the extent of pure silver formation increases. Investigations on the results of electrochemical tests showed that increasing carbon content results in the reduction of corrosion resistance in silver oxide electrodes. Moreover, the results of electric discharge test revealed that the silver oxide electrode containing 10wt% carbon yields the highest energy efficiency in the zinc‐silver oxide batteries.     

Cooperative caching for content dissemination in vehicular networks

The explosive growth of mobile data traffic has made cellular operators to seek low‐cost alternatives for cellular traffic off‐loading. In this paper, we consider a content delivery network where a vehicular communication network composed of roadside units (RSUs) is integrated into a cellular network to serve as an off‐loading platform. Each RSU subjecting to its storage capacity caches a subset of the contents of the central content server. Allocating the suitable subset of contents in each RSU cache such that maximizes the hit ratio of vehicles requests is a problem of paramount value that is targeted in this study. First, we propose a centralized solution in which, we model the cache content placement problem as a submodular maximization problem and show that it is NP‐hard. Second, we propose a distributed cooperative caching scheme, in which RSUs in an area periodically share information about their contents locally and thus update their cache. To this end, we model the distributed caching problem as a strategic resource allocation game that achieves at least 50% of the optimal solution. Finally, we evaluate our scheme using simulation for urban mobility simulator under realistic conditions. On average, the results show an improvement of 8% in the hit ratio of the proposed method compared with other well‐known cache content placement approaches.