The comparison between the effects of solvent casting and melt intercalation mixing processes on different characteristics of polylactide‐nanographite platelets composites

This study investigates the influence of enhanced dispersion of nanographite platelets (NGP) fillers through solvent casting mixing process on rheological, electrical and thermal properties of polylactide (PLA)/NGP composites. PLA/NGP composites were fabricated at 1 to 5 wt% filler contents by means of three processing techniques: (i) dry mixing and melt intercalation; (ii) solvent casting using dichloromethane organic solvent; and (iii) combination of solvent casting and melt intercalation techniques. The extent of dispersion of nanofillers within polymer matrix was evaluated through X‐ray diffraction and transmission electron microscopy analysis of the composites. Morphological studies of the samples revealed that the maximum extent of dispersion of NGP fillers within PLA matrix was achieved when the combination of solvent casting and melt intercalation processes occurred. Rheological analyses of the samples were indicative of deterioration in the composites produced through solvent casting mixing process. Despite of initial reduction in electrical resistivity of the composites after the addition of 1 wt% of NGP fillers, further addition of nanofillers did not exhibit a considerable enhancement in their electrical conductivity of the composites. Thermogravimetric analysis of the composites was demonstrative of enhancing impact of nanofiller loading, along with detrimental effect of solvent casting on the thermal stability of the PLA matrix. POLYM. ENG. SCI., 55:1560–1570, 2015. © 2014 Society of Plastics Engineers     

A rapid method for determination of the origin of meat and meat products based on the extracted fat spectra by using of Raman spectroscopy and chemometric method

Raman spectroscopy and the principal component analysis (PCA) were successfully applied to differentiate the origin of the meat and meat products based on their extracted fat samples in the present study. A total of 132 extracted fat samples that were obtained from different meat species (cattle, sheep, pig, fish, poultry, goat and buffalo) and their salami products were examined based on their Raman measurements. Then, the collected Raman data were analyzed with a four-stage PCA method. Seven meat species and their salami products were successfully differentiated from each other according to their origin. The results of this study showed that the Raman spectroscopy with a chemometric method can be used to detect the origin of the meat species in a very short analysis time (30 s) after fat extraction, without requiring complicated chromatographic, immunologic or genetic methods and instruments as well as trained personnel.     

Effects of Different Calcium Compounds on the Corrosion Resistance of Andalusite-Based Low-Cement Castables in Contact with Molten Al-Alloy

Andalusite containing low-cement castables (LCCs) have been used in aluminum casthouses for several decades. CaF₂ is commonly added to the refractory to improve its corrosion resistance mainly because of its role in the formation of anorthite (CaAl₂Si₂O₈); the latter has been reported to decrease the penetration of molten aluminum alloys into refractories. This article investigates the effect of the addition of different calcium containing compounds (CaO, CaCO₃, CaSO₄, CaF₂, Clinker white cement, calcia feldspar, wollastonite, and Ca₃(PO₄)₂) on reactions with the refractory constituents to form anorthite as well as the effect of the additives on both the subsequent physical properties and the corrosion resistance of andalusite LCC refractories. Corrosion tests using the Alcoa cup test at temperatures (1123 K [850 °C] for 150 hours and 1433 K [1160 °C] for 72 hours) were conducted to determine the extent of penetration, whereas immersion tests in boiling water were conducted to determine the extent of open porosity in the material. Scanning electron microscopy coupled with energy dispersive spectrometer, optical microscopy, and X-ray diffraction techniques were employed to characterize the phase formations in the materials after the tests. The study demonstrated that both calcia feldspar and clinker white cement had the potential to be used as new additives for decreasing the penetration of molten Al-alloy into the refractory materials. Anorthite formation (in the refractory matrix), along with the absence of glassy phases, were responsible for the improvement in the corrosion resistance of the castables containing calcia feldspar. However, in the sample containing cement, the presence of calcium silicate phases were observed to resist reactions with molten aluminum. The observed results were validated using thermodynamic calculations, which indicated that tricalcium silicates (3CaO.SiO₂) and dicalcium silicate (2CaO.SiO₂) phases were more resistant than wollastonite (CaSiO₃) for applications involving contact with molten aluminum.     

Study of Creep–Fatigue Crack Growth Behavior in a Gas Turbine Casing

Journal of Failure Analysis and Prevention - A creep–fatigue crack growth on the outer surfaces of a turbine casing was assessed, and the turbine casing’s overall lifetime was...     

Adaptive Markov-based approach for dynamic virtual machine consolidation in cloud data centers with quality-of-service constraints

Dynamic virtual machine (VM) consolidation is one of the emerging technologies that has been considered for low-cost computing in cloud data centers. Quality-of-service (QoS) assurance is one of the challenging issues in the VM consolidation problem since it is directly affected by the increase of resource utilization due to the consolidations. In this paper, we take advantage of Markov chain models to propose a novel approach for VM consolidation that can be used to explicitly set a desired level of QoS constraint in a data center to ensure the QoS goals while improving system utilization. For this purpose, an energy-efficient and QoS-aware best fit decreasing algorithm for VM placement is proposed, which considers QoS objective when determining the location of a migrating VM. This algorithm employs an online transition matrix estimator method to deal with the nonstationary nature of real workload data. We also propose new policies for detecting overloaded and underloaded hosts. The performance of our proposed algorithms is evaluated through simulations. The results show that the proposed VM consolidation algorithms in this paper outperforms the benchmark algorithms in terms of energy consumption, service-level agreement violations, and other cost factors.     

Study of graphene device electronic properties with horizontal and vertical double vacancy defects

Abstract

Graphene device electronic properties with double vacancy (DV) defects for two cases, along the direction and perpendicular to the current pathways graphene device, were investigated by using the first principles calculations in combination with density functional theory. The bond lengths, density of states, transmission probability, and current-voltage curves are computed. For relaxed pristine graphene the bond length is around 1.43?Å. However, the bond lengths near the defects for relaxed graphene for DV case are modified to 1.40-1.49?Å. It is also observed that I???V graph is nonlinear based on the current-voltage curve of graphene device which contain DV defects. Furthermore, it has been shown that having the DV defects lead to reduce the current relative to the case of perfect graphene device. Moreover, we noted that when the voltage is increased from zero to one volt new peaks are created near Fermi level in the transmission spectrum graphs. In addition, we noted that the current for the vertical DV defect is smaller than the pristine and horizontal DV device because the number of blocked electrons current pathways in vertical DV defect is larger than the two other cases, namely the pristine and horizontal DV defect cases The obtained results can be useful for the construction of new nanoelectronic devices and may have practical applications.     

Effect of alumina content and heat treatment on microstructure and upconversion emission of Er3+ions in oxyfluoride glass-ceramics

The effect of alumina content and heat treatment temperature and time, on microstructure and Er3+ (0.5 mol.%) emission of oxy-fluoride glass-ceramics were investigated in this research. Two values of 1.8 (SA1.8Er0.5) and 2.18 (SA2.18Er0.5) were selected in this re-search for SiO2/Al2O3 ratio. According to DTA results, precursor glasses were heat treated at 630, 660 and 690 °C for 4 h and some glasses were also heat treated at 630 °C for 48 and 72 h. The results indicated that alumina content had significant effect on phase separation and vis-cosity of the glasses. Therefore the size, size distribution, and volume concentration of nano CaF2 crystals which precipitated during the heat treatment depended on alumina content of the glass. Due to the much smaller size of the precipitated CaF2 crystals in the glasses of low alumina content, these samples maintained excellent transparency and had narrower crystal size distribution than the high alumina glasses. The crystal size was increased markedly with the temperature increasing from 630 to 690 °C. On the other hand a slight increase was observed in the crystal size by raising the heat treatment time in both glasses. Results indicated that in low alumina content glass (SA2.18Er0.5) the size of CaF2 nanocrystals was controlled in one order of magnitude. The increase of heat treatment time and temperature led to the incorporation of Er3+ ions into CaF2 crystalline phase, increasing significantly the upconversion intensity. After heat treatment at 690 ℃ for 4 h, atomic force microscope (AFM) re-vealed the development of small crystals with an average size of 80 and 30 nm in SA1.8Er0.5 and SA2.18Er0.5 samples, respectively.     

Effect of heat treatment and solution preparation procedure on colloidal stability of whey protein sour cherry beverage

In this study, a whey protein sour cherry beverage was prepared using whey protein concentrate, sour cherry concentrate, Angum gum, water and sugar as initial ingredients. Whey protein concentrate and gum solutions were prepared by four methods. Heat treatment of the solutions led to denaturation of proteins, a change in the solubility of proteins and sediment formation. Our results showed that denaturation of proteins made the peptide fragments of the proteins to bind the gum, thus preventing the separation of the serum.