Characterization of polyacrylonitrile,poly(acrylonitrile‐co‐vinyl acetate), and poly(acrylonitrile‐co‐itaconic acid) based activated carbon nanofibers

In this study, three different acrylonitrile (AN)‐based polymers, including polyacrylonitrile (PAN), poly(acrylonitrile‐co‐vinyl acetate) [P(AN‐co‐VAc)], and poly(acrylonitrile‐co‐itaconic acid) [P(AN‐co‐IA)], were used as precursors to synthesize activated carbon nanofibers (ACNFs). An electrospinning method was used to produce nanofibers. Oxidative stabilization, carbonization, and finally, activation through a specific heating regimen were applied to the electrospun fibers to produce ACNFs. Stabilization, carbonization, and activation were carried out at 230, 600, and 750 °C, respectively. Scanning electron microscopy, thermogravimetric analysis (TGA), and porosimetry were used to characterize the fibers in each step. According to the fiber diameter variation measurements, the pore extension procedure overcame the shrinkage of the fibers with copolymer precursors. However, the shrinkage process dominated the scene for the PAN homopolymer, and this led to an increase in the fiber diameter. The 328 m²/g Brunauer–Emmett–Teller surface area for ACNFs with PAN precursor were augmented to 614 and 564 m²/g for P(AN‐co‐VAc) and P(AN‐co‐IA), respectively. The TGA results show that the P(AN‐co‐IA)‐based ACNFs exhibited a higher thermal durability in comparison to the fibers of PAN and P(AN‐co‐VAc). The application of these copolymers instead of AN homopolymer enhanced the thermal stability and increased the surface area of the ACNFs even in low‐temperature carbonization and activation processes. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44381.     

Simplex lattice mixture design approach on physicochemical and sensory properties of wheat chips enriched with different legume flours: An optimization study based on sensory properties

In this study, physicochemical and sensory characteristics of wheat chips enriched with different legume flours were investigated. Wheat chips formulations were composed with the mixture of wheat flour and the mixture of three different legume flours (wheat–legume ratio 80:20). Mixture design approach was used to determine the effect of interactions between pea, chickpea and soy flour on the physicochemical and sensory properties of chips produced with wheat–legume flour mixture. In addition, product optimization was carried out by using ridge analysis to determine the optimum legume flour mixture proportions based on sensory properties of chips samples. Chickpea flour was found to be highest desired component depending on the general acceptability scores of chips. Protein content of chips increased significantly with the addition of soy flour. Optimum limit values of chickpea, pea and soy flour in the legume flour mixture used for the enrichment of the wheat chips were found to be 50–100 g/100 g, 0–60 g/100 g and 0–45 g/100 g legume flour, respectively, with respect to sensory properties. Additionally, ridge analysis results showed that the wheat chips should include only chickpea flour in the legume flour fraction to obtain maximum overall preference score (6.08).     

Channel Switching Cost-Aware Energy Efficient Routing in Cognitive Radio-Enabled Internet of Things

Mobile Networks and Applications - Routing is the process of determining the data transmission path from the source to the destination considering restrictions. Optimizing the transmission...     

Investigation effects of environmental and operating factors on PV panel efficiency using by multivariate linear regression

The aim of this study is to show the investigation effects of environmental and operating factors on photovoltaic (PV) panel efficiency using by multivariate linear regression. Also in this study, the relationship between PV panel efficiency and some environmental and operating factors (solar radiation, open‐circuit voltage, short circuit current (I_sc), power, fill factor, outside temperature, humidity, wind speed, and voltage) were investigated using multivariate linear regression. The effect of binary parameter interactions on panel performance was investigated using the backward elimination (or deletion) method. The data used in the analysis were obtained from monocrystal and polycrystal panels in December in the winter season. In all analyzes, the regression values are close to 1, which indicates that the compatibility between binary parameters and performance characteristics is perfect. In addition, the three most effective parameters on panel efficiency were found to be solar radiation, maximum power (P_max), and I_sc, respectively.     

Synthesis,characterization, bactericidal activity,and mechanical properties of hydroxyapatite nano powders impregnated with silver and zinc oxide nanoparticles (Ag-ZnO-Hap)

Hydroxyapatite (Hap) doped or embedded with silver has shown improved bactericidal properties, and its mechanical properties were greatly improved by doping or impregnating Hap with metals such as Magnesium or Zinc, or by impregnating Hap with metal oxides such as MgO, or ZnO. This work describes the preparation of Ag-ZnO-Hap nanocomposites with 4 different Ag-ZnO–Ca mole ratios. XRD, FTIR, SEM, and TEM analysis of all prepared materials identified Hap as the only crystalline phase present in all samples exhibiting a uniform rod-like morphology with particles in the 20–40 nm size range. Microwave Plasma-Atomic Emission Spectroscopy confirmed the presence of zinc and silver in all embedded Hap samples. The antibacterial activity was tested against two different strains; Escherichia coli (E. coli (MV10Nal), and Gram-negative Aggregatibacter actinomycetemcomitans (A.a). The mechanical testing consisted of evaluating breaking force, work of fracture, and brittleness/ductility of Hap and Ag/ZnO/Hap composites. Our study clearly shows that reinforcing Hap with silver and zinc oxide yields superior bactericidal and mechanical properties.     

Temperature Dependency of Steady, Dynamic, and Creep-Recovery Rheological Properties of Ice Cream Mix

In this study, effect of processing temperature (5, 15, 25, and 35 °C) on the steady, dynamic, and creep recovery rheological properties of the ice cream mix (ICM) was investigated. It was found that processing temperature significantly affected all rheological parameters of the ICM sample. The flow behavior of the ICM sample was fitted to the Ostwald de Waele model. The magnitude of storage modulus (G′) was higher than that of loss modulus (G″) indicating that ICM sample had weak gel-like structure. Modified Cox–Merz rules were satisfactorily applied to the ICM sample to observe relationship between steady and dynamic shear properties. Additionally, Burger model was used to characterize the viscoelastic properties of the ICM sample. The gel strength (S) value was also calculated, and a decrease was observed with the increase of temperature. Arrhenius equation satisfactorily described the temperature dependency of the rheological parameters such as apparent viscosity at 50 s^?1 (η ₅₀), consistency coefficient (K), the instantaneous shear modulus of the Maxwell unit (G ₀), permanent deformation (J _∞ ), and S values that may be predicted by using established equations depending on the temperature. The increase in processing temperature caused a decrease in resistance of the mixture subjected to the deformation, which is very important for production of high quality ice cream.     

Rating and Reliability of Existing Bridges in a Network

Currently, the load rating is the method used by State DOTs for evaluating the safety and serviceability of existing bridges in the United States. In general, load rating of a bridge is evaluated when a maintenance, improvement work, change in strength of members, or addition of dead load alters the condition or capacity of the structure. The AASHTO LRFD specifications provide code provisions for prescribing an acceptable and uniform safety level for the design of bridge components. Once a bridge is designed and placed in service, the AASHTO Manual for Condition Evaluation of Bridges provides provisions for determination of the safety and serviceability of existing bridge components. Rating for the bridge system is taken as the minimum of the component ratings. If viewed from a broad perspective, methods used in the state-of-the-practice condition evaluation of bridges at discrete time intervals and in the state-of-the-art probability-based life prediction share common goals and principles. This paper briefly describes a study conducted on the rating and system reliability-based lifetime evaluation of a number of existing bridges within a bridge network, including prestressed concrete, reinforced concrete, steel rolled beam, and steel plate girder bridges. The approach is explained using a representative prestressed concrete girder bridge. Emphasis is placed on the interaction between rating and reliability results in order to relate the developed approach to current practice in bridge rating and evaluation. The results presented provide a sound basis for further improvement of bridge management systems based on system performance requirements.     

The Shear Stress-Strain Behaviour of Low-modulus Structural Adhesives

The shear stress-strain behaviour of two low-modulus structural adhesives has been measured using the butt-torsion test. The Nadai correction for non-linear shear behaviour is explained as it is necessary to understand how this correction can be applied to butt joints. The results for one adhesive were accurately used to predict the strength of a lap joint, and it was shown that the strength of such a joint can approach that of a conventional, modern, structural epoxy. Structural adhesives are usually reckoned to be those with a high strength (50 MPa and upwards) and (these days), a strain to failure of at least 10% in tension, and which usually have a tensile modulus of 2 GPa or so. However, adhesives which are significantly less stiff, less strong, but much more ductile are entering the 'structural' arena. In order to evaluate their effectiveness and use in design, it is necessary to be able to measure accurately their stress-strain behaviour. Two such materials are 3M 9245 Structural Bonding Tape (SBT) and 3M 7838 B/A.     

Comparison of two isolation methods for essential oil from rosemary leaves: Hydrodistillation and microwave hydrodiffusion and gravity

Traditional hydrodistillation (HD) and innovative Microwave Hydrodiffusion and Gravity (MHG) methods have been compared and evaluated for their effectiveness in the isolation of essential oil from fresh Rosmarinus officinalis leaves. The microwave method offers important advantages over traditional alternatives, namely: shorter isolation times (15 min against 3 h for hydrodistillation), environmental impact (energy cost is fairly higher to perform HD than that required for rapid MHG isolation), cleaner features (as no residue generation and no water or solvent used), increases antimicrobial activities, increases antioxidant activity and provides a more valuable essential oil (with high amount of oxygenated compounds). It offers also the possibility for a better reproduction of natural aroma of the essential oil from rosemary leaves than the HD essential oil. Moreover, microwave procedure yielded essential oils that could be analysed or used directly without any clean-up, solvent exchange or centrifugation steps. Scanning electron microscopy shows important structural changes for MHG extraction in contrast to those obtained by HD. Electron micrographs show clearly that the cells are broken and damaged during microwave treatment. Finally, the mechanism of Microwave Hydrodiffusion and Gravity is proposed and discussed.