Effect of α-Fe2O3 addition on the morphological,optical and decolorization properties of ZnO nanostructures

Visible light sensitive photocatalysts of Fe₂O₃/ZnO nanocomposites were prepared by a simple solid-state reaction method, using zinc acetate, α-Fe₂O₃ and sodium hydroxide at room temperature. The products were characterized by scanning electron microscopy, powder X-ray diffraction, N₂ adsorption–desorption measurement, UV–vis absorption, and photoluminescence spectroscopy and used for photodecolorization of Congo red. The characterization results showed that the morphology, crystallite size, BET surface area and optical absorption of the samples varied significantly with the Fe³⁺ to Zn²⁺ ratios. The nanocomposites show two absorption edges at ultraviolet and visible region. The optical band gap values of these nanocomposites were calculated to be about 3.98–3.81 eV and 2.88–2.98 eV, which show a red shift from that of pure ZnO. These red shifts are related to the formation of Fe s-levels below the conductive band edge of ZnO and effectively extend the absorption edge into the visible region. The growth mechanisms of the samples are proposed. These nanocomposites showed high decolorization ability in visible light with wavelength up to about 400 nm. Among the samples, Fe₂O₃/ZnO nanoflower (molar ratio of Fe³⁺ to Zn²⁺ is 1:100) exhibited higher decolorization efficiency than the other nanocomposites. It could be considered as a promising photocatalyst for dyes treatment.     

Text Encryption Using Pell Sequence and Elliptic Curves with Provable Security

The demand for data security schemes has increased with the significant advancement in the field of computation and communication networks. We propose a novel three-step text encryption scheme that has provable security against computation attacks such as key attack and statistical attack. The proposed scheme is based on the Pell sequence and elliptic curves, where at the first step the plain text is diffused to get a meaningless plain text by applying a cyclic shift on the symbol set. In the second step, we hide the elements of the diffused plain text from the attackers. For this purpose, we use the Pell sequence, a weight function, and a binary sequence to encode each element of the diffused plain text into real numbers. The encoded diffused plain text is then confused by generating permutations over elliptic curves in the third step. We show that the proposed scheme has provable security against key sensitivity attack and statistical attacks. Furthermore, the proposed scheme is secure against key spacing attack, ciphertext only attack, and known-plaintext attack. Compared to some of the existing text encryption schemes, the proposed scheme is highly secure against modern cryptanalysis.     

Radiofrequency Shielding by Polypyrrole-Coated Nano and Regular Fibrous Mats

This work investigates radiofrequency shielding by polypyrrole (PPy)-coated fibrous mats consisting of nano and regular fibers. Radiofrequency shielding protects human beings as well as electronic devices from the harmful effects of radiofrequency waves. The results of this study show that, generally, lowering the fiber diameter of the coated mats increases the reflection but decreases the absorption of radiofrequency radiation in the range of 5 GHz to 8 GHz. Moreover, absorption of higher frequencies is greater than that of lower frequencies, whereas for reflection the opposite trend is observed. The sum of absorption and reflection of radiofrequencies in the range of 5 GHz to 8 GHz by PPy-coated mats is not affected by the fiber diameter of the mats. PPy-coated regular poly(acrylonitrile) (PAN) and poly(ethylene terephthalate) (PET) fiber mats with weight per unit area of 16.67 mg/cm² provide radiofrequency shielding above 85%. Nanofibrous mats with weight per unit area of nearly 60 times less showed similar radiofrequency shielding effectiveness as regular fiber mats, highlighting the importance of the high specific surface area of nanofibers.     

SNEFL: Social network explicit fuzzy like dataset and its application for Incel detection

In this paper, with respect to reviewing and comparing existing social networks’ datasets, we introduce SNEFL dataset: the first social network dataset that includes the level of users’ likes (fuzzy like) data in addition to the likes between users. With users’ privacy in mind, the data has been collected from a social network. It includes several additional features including age, gender, marital status, height, weight, educational level and religiosity of the users. We have described its structure, analysed its features and evaluated its advantages in comparison with other social network datasets. On top of that, using unique feature of SNEFL dataset (fuzzy like) for the first time a rule-based algorithm has been developed to detect involuntary celibates (Incels) in social networks. Despite Incels activities in online social networks, until now no study on computer science has been performed to identify them. This study is the first step to address this challenge that society is facing today. Experimental results show that the accuracy of the proposed algorithm in identifying Incels among all social network users is 23.21% and among users who have fuzzy like data is 68.75%. In addition to the Incel detection, SNEFL dataset can be used by researchers in different fields to produce more accurate results. Some study areas that SNEFL dataset can be used in are network analysis, frequent pattern mining, classification and clustering.

     

Influence of processing conditions on polymorphic behavior,crystallinity, and morphology of electrospun poly(VInylidene fluoride) nanofibers

The polymorphism and crystallinity of poly(vinylidene fluoride) (PVDF) membranes, made from electrospinning of the PVDF in pure N,N‐dimethylformamide (DMF) and DMF/acetone mixture solutions are studied. Influence of the processing and solution parameters such as flow rate, applied voltage, solvent system, and mixture ratio, on nanofiber morphology, total crystallinity, and crystal phase content of the nanofibers are investigated using scanning electron microscopy, wide‐angle X‐ray scattering, differential scanning calorimetric, and Fourier transform infrared spectroscopy. The results show that solutions of 20% w/w PVDF in two solvent systems of DMF and DMF/acetone (with volume ratios of 3/1 and 1/1) are electrospinnable; however, using DMF/acetone volume ratio of 1/3 led to blockage of the needle and spinning process was stopped. Very high fraction of β‐phase (～79%–85%) was obtained for investigated nanofiber, while degree of crystallinity increased to 59% which is quite high due to the strong influence of electrospinning on ordering the microstructure. Interestingly, ultrafine fibers with the diameter of 12 and 15 nm were obtained in this work. Uniform and bead free nanofiber was formed when a certain amount of acetone was added in to the electrospinning solution. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42304.     

On the encapsulation of natural pesticide using polyvinyl alcohol/alginate–montmorillonite nanocomposite for controlled release application

A representative pesticide, NeemAzal was encapsulated into polyvinyl alcohol/alginate‐montmorillonite (PVA/Alg‐MMT) nanocomposite by cross‐linking with glutaraldehyde. Different formulations of capsule beads containing NeemAzal were prepared with different concentration of materials. Evidence of cross‐linking of PVA and Alg was obtained by comparison of the Fourier transform infrared spectra of the initial substrates and capsule beads. X‐ray diffraction and transmission electron microscopy techniques confirmed the intercalated structure of capsule bead nanocomposites. In addition the swelling behavior of capsule beads was investigated. Results showed that swelling ratio of capsule beads decreases with introduction of MMT as well as increase of PVA content in capsule bead formulations. The release characteristics of NeemAzal from capsule beads were monitored using UV–visible spectrophotometer in distilled water. The addition of sodium MMT to these formulations was found to have a profound inhibitory effect on the release of NeemAzal. Furthermore, the release data were fitted to several empirical equations to estimate the kinetic parameters. The NeemAzal encapsulated PVA/Alg‐MMT nanocomposite capsule beads, designed and discussed in this work, have the potential for controlled release of pesticide. POLYM. ENG. SCI., 54:2707–2714, 2014. © 2013 Society of Plastics Engineers     

Simulation and the Future of Design Tools for Ecological Research

In sustainable terms, the complexity and inefficiencies of buildings present the most challenging environmental problem. Simulation remains the primary tool for the designer to develop intuitions and analysis of performance. As Azam Khan, Head of the Environment & Ergonomics Research Group at Autodesk, and Andrew Marsh, Senior Principal Engineer at Autodesk , explain, simulation can only be improved through the development of three key areas: more detailed modelling, building integration and by becoming indispensable to the design process. Copyright © 2011 John Wiley & Sons, Ltd.     

Studies on physicochemical characteristics of chitosan derivatives with dicarboxylic acids

Chitosan (N-deacetylated derivative of chitin) was solubilised in different aqueous dicarboxylic acid solutions, including oxalic acid, malonic acid, adipic acid, azelaic acid and also in monocarboxylic acetic acid. These dicarboxylic acid solutions were used with the objective that they not only act as solvents but also enhance material properties of chitosan gel films through chemical cross-linking. The properties including conformational changes of chitosan, chemical interaction, and mechanical, morphological and thermal characteristics of selected chitosan samples studied in this work. The circular dichroism study indicated that the intensity of the broad negative transition of chitosan helical structure in the wavelength region of 190–230 nm decreased with decreasing the chain length of the dicarboxylic acids. The infrared spectra revealed the formation of amide linkage between chitosan and carboxylic acids in solid state. The cross-sections of the films produced from malonic acid and acetic acid solutions of chitosan exhibited granular morphologies with different granule sizes and hill-valley-structures under atomic force microscope. The chitosan/malonic acid film showed improved water resistance and decreased tensile properties compared with the chitosan/acetic acid and chitosan/adipic acid films. These physical characteristics of chitosan/malonic acid film are attributed to the dual effects of malonic acid, which acts as a chemical cross-linker and also as a plasticizer. A strong glass transition (T _g) peak at 166 °C in differential scanning calorimetric analysis was observed, indicating the possible plasticizing effect with malonic acid.     

Modified calibrated control charts for monitoring the population mean under stratified sampling

In this research paper, we discuss the use of calibration technique to propose some new estimators under stratified sampling design and its use in reliability engineering. We first proposed the estimators using the calibration technique and then modify the already existing control charts such as Shewhart, exponentially weighted moving average and hybrid exponentially weighted moving averages using these calibration estimators. We also have studied the use of the proposed control charts in detail by showing their efficiency in terms of average run length. We find out that a hybrid control chart is more effective to detect the early shifts in the mean of the process.