Enhanced mechanical and thermal properties of graphene nanoplatelets-reinforced polyamide11/poly(lactic acid) nanocomposites

The present paper aims to obtain a sustainable nanocomposite by using bio-based polyamide 11 and biodegradable poly (lactic acid) blend as matrix and graphene nanoplatelets (GNP) as nanofiller. GNP was incorporated in the PA11/PLA blend matrix in the ratio of 0.5-1-3-5-10 wt% through the twin-screw extruder. The crystallinity of PA11 in the blend, which was 12.9%, increased with the inclusion of GNP, and the highest crystallinity value was observed at 20% for the 1GNP sample. The crystallinity of PLA in the blend, which was 2.3%, increased to 4.6% with 5 wt% GNP addition. The inclusion of GNP to PA11/PLA improved the thermal degradation temperatures and increase the char residue. Also, increments were observed for storage modulus, loss modulus, and glass transition temperature of the matrix with the inclusion of GNP. The addition of GNP caused the tensile strength of the matrix to increase first and then decrease at higher amounts due to the agglomerations. 0.5–1 wt% GNP increased tensile strength by 10% and 5%, respectively. Increasing the amount of GNP to 10 wt% led to a sharp decrease in tensile strength by 24%. Overall, GNP is a suitable nanofiller to enhance the thermal and mechanical features of the PA11/PLA blend.     

Comparison of Blackbodies for Calibration of Infrared Ear Thermometers

The article presents the results of the EURAMET Project No. 927 ??Comparison of blackbodies for calibration of infrared ear thermometers (IRETs)??. The objective of the comparison was to determine the agreement of blackbodies used for the calibration of IRETs among European national laboratories. To verify the accuracy of an IRET, a suitable blackbody (BB) is needed. Such a blackbody related to the EN standard, designed for the calibration of ear thermometers and immersed in a stirred water bath, was provided for the comparison by the pilot laboratory. The pilot provided also the transfer IRET and organized the comparison.     

Fatigue characteristics of continuous welded rails and the effect of residual stress on fatigue-ratchetting interaction

ABSTRACT

The importance of ratchetting-fatigue interaction is garnering interest due to complex failure mechanism of rail welds under cyclic loading. The objective of this paper is to investigate the fatigue characteristics of continuous welded rails (CWRs) and the effect of residual stress on fatigue-ratchetting interaction. For this purpose, UIC60 rails have been modeled using a three-dimensional finite element model, including a combination of nonlinear kinematic and isotropic hardening. In addition, the interaction between cyclic loading and the effect of residual stress on fatigue is taken into consideration. Finite element model is validated against representative experimental findings. Smith–Watson–Topper (SWT) method is utilized in order to estimate the fatigue life of rail welds under static and cyclic loading. Lower fatigue life is predicted with increasing load due to the contact between rails and wheels. Simulation results also show that failure in the form of ratchetting occurs during the 10,236th cycle, while failure corresponds to the 15,290th cycle and the 145,161st cycle based on the SWT and Coffin-Manson fatigue models, respectively. These findings suggest that investigations on ratchetting and fatigue should be carried out simultaneously to estimate the failure of the CWRs.     

Preparation and characterization of coenzyme Q10-Eudragit solid dispersion

A solid dispersion of Coenzyme Q10 and Eudragit L 100-55 was prepared using solvent evaporation method. Solid dispersion, physical mixture, and pure compound were then characterized using differential scanning calorimetry and powder x-ray diffraction. Solubility of CoQ10 in different surfactant media was measured, and a suitable dissolution medium was developed to compare the dissolution patterns of the solid dispersion, physical mixture, and the pure compound. Combining labrasol with different surfactants in dissolution media demonstrated an additive effect on CoQ10 solubility. The solubility of CoQ10 in a 4% Labrasol/2% Cremophor EL solution was 562 microg/ml, which was five times higher than the combined solubility in 5% Labrasol (91 microg/ml) and 5% Cremophor EL (7.8 microg/ml). Moderate change in the crystalline pattern of CoQ10 was observed, which was attributed to solvent displacement rather than the degree of crystallinity change. The dissolution test indicated that the in-vitro release of Coenzyme Q10 from its solid dispersion was much faster than its physical mixture, which in turn was faster than the pure drug. The amount of drug released in 12 hours from solid dispersion, physical mixture, and the pure drug was 100, 26.5 and 12.5% respectively. CoQ10 was photostable throughout the dissolution experiments.     

User behavior modeling of voice communications: an empirical study

In this study, analysis and modeling of arrival and service processes are presented in a comprehensive fashion in order to determine statistical properties of voice traffic from end‐user perspective in accordance with the queueing theory. For the first time in the literature, we introduce a user centric approach and examine these services considering both flow directions of voice traffic, the uplink and the downlink as opposed to existing studies with the network centric approach. In our study, we use experimental data composed of actual phone calls collected from 2G/3G networks. To achieve this, we designed and implemented a data collection system for mobile users and compared the results by using data from an operational cellular network. In order to determine the time correlation of voice calls, Hurst parameter estimation methods are used. On the basis of the outcomes, independency of call arrivals is shown. Additionally, it is shown that calls acquired from user and network centric approaches are both Poisson distributed. Next, looking at the problem from service process perspective, thorough analyses are performed to determine mathematical models that can best characterize call holding times. Maximum likelihood estimation and expectation maximization algorithm are used, and it is shown that the optimum mathematical model for the characterization of call holding times is the lognormal distribution family. Copyright © 2014 John Wiley & Sons, Ltd.     

Reduced graphene oxide reinforced PET/PBT nanocomposites: Compatibilization and characterization

This research work focused on the effects of different compatibilizers on the properties of reduced graphene oxide (rGO) reinforced poly(ethylene terephthalate) (PET)/poly(butylene terephthalate) (PBT) nanocomposites. The samples were prepared via melt compounding and injection molding methods. The Joncryl and glycidyl isooctyl polyhedral oligomeric silsesquioxane (GPOSS) were used as compatibilizers at different loading levels (0.5%-4%). The structural, thermal, mechanical, morphological, and electrical properties of the nanocomposites were investigated. The Fourier transform infrared analysis results revealed that no significant interaction was observed when GPOSS was added. On the other hand, there were more obvious changes in the peaks of the nanocomposite containing Joncryl. The thermal results showed that the compatibilizer addition caused small changes while rGO addition did not considerably affect the thermal stability of blend. The glass transition temperature of the nanocomposite significantly decreased with the addition of GPOSS. The tensile test indicated that compatibilizers improved the mechanical performance of PET/PBT/rGO nanocomposite.     

Hydropower Plant Site Assessment by Integrated Hydrological Modeling,Gene Expression Programming and Visual Basic Programming

Water Resources Management - The integrated hydrological modeling techniques were used to create a conceptual rainfall-runoff model for Hurman River watershed. The HEC-HMS and water modeling system...     

The inhibitory effects of Lactobacillus casei and Lactobacillus helveticus on Bacillus species isolated from raw milk in various salt concentrations

Nineteen strains of Bacillus were isolated and identified from 111 samples of raw milk. The inhibitory effects of Lactobacillus casei and Lactobacillus helveticus on strains of Bacillus were studied. The inhibitory effects were evaluated (using the well diffusion method) on nutrient agar, with NaCl added at concentrations of 40, 45, 50, 55, 60 and 65 g/L. Lactobacillus casei inhibited 16 strains of Bacillus on nutrient agar without salt, and 18 strains in the presence of salt. When the salt concentration was 6.5%, the inhibitory effect decreased, and L. casei inhibited only eight strains of Bacillus ( Bacillus cereus , Bacillus sphaericus , Bacillus licheniformis , Bacillus macerans , Bacillus firmus , Bacillus coagulans , Bacillus polymyxa and Bacillus stearothermophilus ). Lactobacillus helveticus formed the inhibitory zones against five strains of Bacillus on nutrient agar without salt, but with 4% NaCl concentration, it showed an inhibitory effect on 13 strains; a further two strains were inhibited in the presence of 4.5 and 5.0% salt. In 5.5% NaCl, the same 15 strains were inhibited by L. helveticus, whilst in 6 and 6.5% salt, the inhibitory effect decreased and only six and seven strains were affected, respectively. The maximum inhibitory effect with both L. casei and L. helveticus was observed in the presence of 4.5–5.5% salt.