Effect of particle content, size and temperature on magneto-thermo-mechanical creep behavior of composite cylinders

The effects of particle content, particle size, operating temperature and magnetic field on steady-state creep behavior of thick-walled rotating cylinders made of Al-SiC composites have been investigated. Loading is composed of a uniform magnetic field in axial direction, steady-state heat conduction in radial direction and an inertia body force due to rotation. The composite creep constitutive equation has been described by Norton’s law in which the creep parameters are functions of particle size, temperature and particle content. The composite properties are radial dependent based on volume fraction of SiC reinforcement. It has been found that the minimum effective creep strain rate belongs to a composite identified by 25% SiC at the inner and 5% at the outer surfaces. Therefore this composite has been selected for the design of the cylinder. It has been concluded that increasing particle size and operating temperature significantly increases the effective creep strain rates. It has also been illustrated that magnetic field decreases the stresses and the effective creep strain rates.     

Functionalized nanostructured silica by tetradentate-amine chelating ligand as efficient heavy metals adsorbent : Applications to industrial effluent treatment

Organofunctionalized nanostructured silica SBA-15 with tri(2-aminoethyl)amine tetradentate-amine ligand was synthesized and applied as adsorbent for the removal of Cu²⁺, Pb²⁺, and Cd²⁺ from both synthetic wastewater and real paper mill and electroplating industrial effluents. The prepared materials were characterized by XRD, N₂ adsorption-desorption, TGA, and FT-IR analysis. The Tren-SBA-15 was found to be a fast adsorbent for heavy metal ions from single solution with affinity for Cu²⁺, Pb²⁺, than for Cd²⁺ due to the complicated impacts of metal ion electronegativity. The kinetic rate constant decreased with increasing metal ion concentration due to increasing of ion repulsion force. The equilibrium batch experimental data is well described by the Langmuir isotherm. The maximum adsorption capacity was 1.85 mmol g^?1 for Cu²⁺, 1.34 mmol g^?1 for Pb²⁺, and 1.08 mmol g^?1 for Cd²⁺ at the optimized adsorption conditions (pH=4, T=323 K, t=2 h, C₀=3 mmol L^?1, and adsorbent dose=1 g L^?1). All Gibbs energy was negative as expected for spontaneous interactions, and the positive entropic values from 103.7 to 138.7 J mol^?1 K^?1 also reinforced this favorable adsorption process in heterogeneous system. Experiment with real wastewaters showed that approximately a half fraction of the total amount of studied metal ions was removed within the first cycle of adsorption. Hence, desorption experiments were performed by 0.3M HCl eluent, and Tren-SBA-15 successfully reused for four adsorption/desorption cycles to complete removal of metal ions from real effluents. The regenerated Tren-SBA-15 displayed almost similar adsorption capacity of Cu²⁺, Pb²⁺, and Cd²⁺ even after four recycles. The results suggest that Tren-SBA-15 is a good candidate as an adsorbent in the removal of Cu²⁺, Pb²⁺, and Cd²⁺ from aqueous solutions.     

SBR COMPOSITES REINFORCED WITH N-ISOPROPYL-N'PHENYL-P-PHENYLENEDIAMINE-MODIFIED CLAY

SBR compounds including the N-isopropyl-N'-phenyl-p-phenylenedianfine-modified clay (organoclay) were prepared. Effects of modified clay and antioxidant (IPPD) contents on mechanical and rheological properties of SBR composites were studied. FTIR results confirmed that the clay was chemically modified by IPPD and changed into an organoclay. X-ray diffraction (XRD) results confirmed the increase in interlayer distance of the clay due to the insertion of IPPD. Rheological and cure characteristics of SBR compounds were determined using RPA (Rubber Process Analyzer) and rheometer. Scorch time and cure time of SBR compounds decreased with introduction of the organoclay. Mechanical properties and heat aging resistance of the SBR composites were improved significantly by incorporation of the organoclay.     

Laboratory test and FEM analysis on a developed continuous rail absorber (CRA)

Rail has a significant contribution in overall produced noise in railway freight tracks. Implementing rail noise absorbers is a promising way to increase the attenuation of the vibration. Designing of a rail noise absorber to work in critical frequencies in which the rail undergoes its maximum vibration is crucial. Moreover, total cost of installation, maintenance, repair, and operations as practical aspects of manufacturing have drew the attention of researchers. Regard to this point, the authors have developed a continuous rail noise absorber (CRA) which is composed of steel and elastomeric layers. The lateral and bottom surfaces of the rail is covered by the layers using specialized proprietary adhesive. The initial investigations and survey of the problem is reported in the authors’ previous paper which resulted in proposition of CRA. In this research CRA is produced and laboratory tests are carried out on a disjointed section of Tehran-Zanjan commercial rail track to determine the efficiency of the noise absorber system. It is revealed that the noise of rail availed of CRA is decreased about 9 dB in frequency range 500-2000 Hz. Owing to its noncomplex structure and lower cost of installation, CRA is a desirable noise absorber system for railway administrations. Furthermore, experimental values are compared with those ones obtained through a finite element model which are in a good agreement.     

Monopulse Cassegrain antenna design using evolutionary algorithms

Using evolutionary programming (EP), monopulse Cassegrain antennas with four feeds can be designed for the desired sum gain, side lobe level and minimum possible antenna size. A method is proposed to achieve the optimum monopulse difference pattern. cos^q(θ) type feeds are considered as the feed system and the final designs have been checked using real feeds. Proper cost functions are proposed to achieve the desired gain, side lobe level and optimum slope in the difference pattern, taking into account the feasibility of the feed system. The effects of the parameters involved in the optimization are investigated.     

Experimental Investigation of Poly-β-Hydroxybutyrate Production by Azohydromonas lata: Kinetics and Artificial Neural Network Modeling

Batch culture of Azohydromonas lata was investigated for the production of intracellular poly-β-hydroxybutyrate (PHB). In order to determine the C:N value of the culture media for maximizing the microbial productivity of PHB, different concentrations of glucose and ammonium chloride were used as carbon and nitrogen sources, respectively. The optimal temperature and shaking rate was obtained at 30°C and 180 rpm, respectively. The maximum intracellular PHB concentration obtained was 5.09 g/l, which was 20% (w/w) of the cell dry weight (CDW) after 72 h. Also, the synthesis of PHB was growth associated with the C:N ratio of 153.71. The maximum calculated Y_p/s was 0.212 (gr/gr) and the specific production rate value after 12 h was 0.264 g/l/h, with 40 and 50 g/l of glucose concentrations, respectively, with 0.5 g/l ammonium chloride kept constant. The chemical composition of the resulting PHB was analyzed by Fourier transform infrared spectroscopy and proton nuclear magnetic resonance spectroscopy. The Leudeking–Piret model was used for kinetic analysis of the PHB production, the statistical analysis of which was modeled by response surface methodology. An artificial neural network technique was applied for modeling of the microbial production of PHB by A. lata as a function of the glucose concentration and CDW, where the minimum mean square error of the model was 0.0012 and 0.0038 for glucose concentrations of 50 g/l and 40 g/l, respectively, when 0.5 g/l ammonium chloride was kept constant.     

Reversible Data Hiding in Encryption Domain based on two dimensional histogram shifting and secure encryption system

Multimedia Tools and Applications - Reversible Data Hiding in Encryption Domain (RDHED) can be used in different areas such as secure remote sensing or telemedicine. Since data structure is...     

COD removal from landfill leachate using a high-performance and low-cost activated carbon synthesized from walnut shell

An activated carbon with high adsorption capacity was synthesized from walnut shell as a solid waste using different chemical reagents. It was used to mitigate chemical oxygen demand from municipal landfill leachate. The activated carbon synthesized with impregnation ratio of 4:1 (H₃PO₄ to char) at a temperature of 500°C (ACH4-500) demonstrated the best textural properties based on Brunauer–Emmett–Teller analysis, i.e., specific surface area of 1,851.1?m²/g, total pore volume of 1.03?cm³/g, and mean pore diameter of 2.24?nm and was selected for adsorption experiments. The maximum adsorption capacity and removal were 123.1?mg/g and 84.7% under optimum condition, respectively. The equilibrium data were fitted with different model isotherms and Redlich–Peterson model showed the best match with experimental data. Kinetic data were well described by pseudo-second-order equation. Study of adsorption thermodynamics revealed spontaneous and endothermic nature of adsorption. In addition, the adsorbent showed satisfactory results, e.g., 100% removal of Pb²⁺, Cd²⁺, and Mn²⁺, in diminishing heavy metals as hazardous materials from landfill leachate.     

Kinetics and thermodynamic studies of Cr(VI) adsorption using environmental friendly multifunctional zeolites synthesized from coal fly ash under mild conditions

Abstract

The Na-P1 zeolite was produced from coal fly ash and modified with different environmental friendly surfactants. The potential of these green modified zeolites was investigated as adsorbents for Cr(VI) ions in a batch system. XRD, SEM, XRF, and ICP-AES analyses were used for the characterization of raw materials and zeolite samples. The environmental friendly modified zeolites successfully immobilized different toxic elements in their framework inhibiting the transfer of these toxic elements to the surrounding liquid phase. The effects of various operational parameters on Cr(VI) removal were studied. The Hexamethylenediamine (HDTMA) and Ammonyx KP (KP) modified zeolites had larger chromium removal potential than the other samples at all temperatures. The effectiveness of Cr(VI) ions elimination became greater as the pH decreased and the adsorbent dose increased. The Freundlich, Langmuir, and Dubinin–Radushkevich isotherms were fitted to the equilibrium data. The Dubinin–Radushkevich and Langmuir models gave a better fitness to equilibrium data of HDTMA-Na-P1 and KP-Na-P1, respectively. The positive and high ΔH° values showed the endothermic nature of the total Cr(VI) sorption procedure and indicated that Cr(VI) adsorption onto HDTMA-Na-P1 and KP-Na-P1 is a chemisorption. The negative ΔS° values also showed that chromium ions were stable on the surface of adsorbents. The adsorption potential of the developed eco-friendly KP-Na-P1 was higher than those of other adsorbents reported in the literature.