Adhesion of Self-Compacting Overlays Applied to Different Concrete Substrates and Its Prediction by Fuzzy Logic

An experimental and analytical study was performed to evaluate the adhesion between concrete and overlays using five different substrate surfaces and six different mixtures of self-compacting concrete and mortar. Saw cut surfaces of high strength concrete slabs were used as substrate. After the application of self-compacting concrete or mortar layers to dry, saturated surface dry, saturated surface wet, dry with bonding grout, and saturated with bonding grout surfaces of concrete slabs, they were covered with wet hessian and polythene sheets for curing. At the age of 28 days, friction-transfer tests were performed to evaluate the adhesion. The results indicate that while dry and saturated wet surfaces produced the lowest bond strength, the application of cement bonding grout improved the bond strength significantly. The results also showed that despite the noticeable correlations between the adhesion and the results of different flow tests, aggregate/cement ratio, fly ash/cement ratio, compressive strength, and water/powder ratio, the effect of the other constituents of the employed self-compacting overlays on their adhesion were not so significant. In order to predict the adhesion of self-compacting mixtures applied to concrete substrates, a fuzzy logic model was also devised. The results obtained from the fuzzy logic prediction model were compared with the average results of the friction-transfer method and found to be in very close agreement. The results show that fuzzy logic can be used to predict adhesion of self-compacting overlays.     

The interaction of hydrogen with Li-coated C70 fullerene: A DFT study

We have applied density functional calculations to study the structure, stability and hydrogen storage properties of Li-coated C₇₀ fullerenes. Our results show that among different possibilities for the geometry of Li-coated C₇₀ fullerenes, Li atoms prefer to occupy exohedral and endohedral positions on top of the pentagons. Among isomers of Li₂C₇₀ and Li₆C₇₀, those in which one of the Li atoms occupy the endohedral position of one of the polar pentagonal rings and the other ones situate on the top of the pentagons around the opposite polar pentagon, have higher binding energies. Charge transfer is occurred from Li to C₇₀, putting extra electrons in the vicinity of the Li atom. This results in the binding of hydrogen in atomic form to the on-top C site that is nearest to the Li atom in the preferred configuration of hydrogenated Li-coated C₇₀ fullerene. Therefore, there are two types of hydrogen binding in Li₆C₇₀. One group of hydrogen bind to Li atoms in quasi-molecular form, which will desorb at a lower temperature, and the other group of H atoms bind to C in atomic form, which will desorb at higher temperatures.     

The role of zinc aluminum phosphate anticorrosive pigment in Protective Performance and cathodic disbondment of epoxy coating

Protective performance and cathodic disbondment of epoxy coating pigmented with zinc aluminum phosphate (ZPA) were studied in this work. In solution, superior corrosion inhibition of ZPA extracted from EIS and electrochemical noise data was connected to deposition of a protective layer. EIS evaluation of the pigmented coatings indicated significant effect of modification of zinc phosphate on the protective performance as well as resistance to cathodic disbonding. Compared to ZPA, introduction of zinc phosphate resulted in inferior performance in cathodic disbonding test. In presence of ZPA, precipitation at disbonding front inferred from EIS data was confirmed by SEM.     

Bandwidth enhancement of injection-locked 1.3 μm quantum-dot DFB laser

Optical injection locking of a quantum-dot distributed-feedback laser at 1.3 mum is reported. Using an injection ratio of 5.3 dB, an optical detuning of -40 pm, and a slave laser biased at 20 mA, the modulation bandwidth of the injection-locked laser was 16.3 GHz. This is over four times higher than the modulation bandwidth of the free-running quantum-dot laser. At a slave laser bias of 5.0 mA, injection locking resulted in a resonance frequency of 21.9 GHz, over eleven times higher than the relaxation frequency of the free-running slave laser.     

The influence of matrix viscosity and composition on the morphology,rheology, and mechanical properties of thermoplastic elastomer nanocomposites based on EPDM/PP

The morphological and rheological properties of thermoplastic elastomer nanocomposites (TPE nanocomposites) were studied using different viscosities of polypropylene (PP) and ethylene‐propylene‐diene monomer (EPDM) rubber content (20, 40, 60 wt%). The components, namely EPDM, PP, Cloisite 15A, and maleic anhydride‐modified PP as compatibilizer, were compounded by a one‐step melt mixing process in a laboratory internal mixer. The structure of the nanocomposites was characterized with X‐ray diffraction, scanning electron microscopy, transmission electron microscopy, and rheometry in small amplitude oscillatory shear. The distribution state of the clay between the two phases (PP and EPDM) was found to be dependent on the viscosity ratio of PP to EPDM. In the nanocomposites prepared based on low viscosity PP (LVP) and EPDM, the clay was mostly dispersed into the PP phase and the size of the dispersed rubber particles decreased in comparison with unfilled but otherwise similar blends. However, the dispersed elastomer droplet size in the high viscosity PP (HVP) blends containing 40 and 60% EPDM increased with the introduction of the clay. For TPE nanocomposites, the dependence of the storage modulus (G′) on angular frequency (ω) followed a clear nonterminal behavior. The increase in the storage modulus and the decrease in the terminal zone slope of the elastic modulus curve were found to be larger in the LVP nanocomposite in comparison with the HVP sample. The yield stress of nanoclay‐filled blends prepared with LVP increased more than that of HVP samples. The tensile modulus improved for all nanocomposites but a higher percentage of increase was observed in the case of LVP samples. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

Prediction of fatigue crack nucleation life in polycrystalline AA7075‐T651 using energy approach

A crystal plasticity (CP) simulation and an energy‐based model is presented to predict the fatigue nucleation onset for polycrystalline AA 7075‐T651. Different microstructure morphology and grain sizes are employed in the simulations. Using a simple method, statistically stored dislocation (SSD) and geometrically necessary dislocation (GND) as decoupled with crystal plasticity model are estimated using a double round‐notch specimen test data, and CP simulation. The dislocation density parameter approximated from plastic energy density, stored energy density, elastic energy and accumulated slip validated with double hole experimental data. Sensitivity analysis is performed with respect to different microstructures and dislocation density parameters. Roughly, maximum 30% difference between experimental nucleation life and the simulated one is observed. The simulated predictions are in fair agreement with test data. The proposed strategy is suitable to study the scatter of fatigue nucleation life.     

Handling multiple materials for exposure of digital forgeries using 2-D lighting environments

The distribution of incident light is an important physics-based cue for exposing image manipulations. If an image has been composed from multiple sources, it is likely that the illumination environments of the spliced objects differ. Johnson and Farid introduced a proof-of-principle algorithm for a forensic comparison of lighting environments. However, this baseline approach suffers from relatively strict assumptions that limit its practical applicability. In this work, we address one of the biggest limitations, namely the need to compute a lighting environment from patches of homogeneous material. To compute a lighting environment from multiple-color surfaces, we propose a method that we call “intrinsic contour estimation” (ICE). ICE is able to integrate reflectances from multiple materials into one lighting environment, as long as surfaces of different materials share at least two similar normal vectors. We validate the proposed method in a controlled ground-truth experiment on two datasets, with light from three different directions. These experiments show that using ICE can improve the median estimation error by almost 50 %, and the mean error by almost 30 %.     

Effect of single-walled carbon nanotubes on morphology and mechanical properties of NBR/PVC blends

Dynamically vulcanized thermoplastic elastomer based on Nitrile butadiene-rubber (NBR)/PVC with functionalized single-walled carbon nanotubes (f-SWNTs) and non-functionalized single-walled carbon nanotubes (SWNTs) were prepared using a brabender internal mixer. Effects of two types of SWNTs (functionalized and non-functionalized) on morphology and mechanical properties of NBR/PVC blends were studied. Results showed that the mechanical properties of NBR/PVC/SWNTs nanocomposites improved with the increasing of SWNTs content and in particular with the increase of f-SWNTs content. Moreover, the enhancement of mechanical properties of NBR/PVC blends reinforced with functionalized SWNT was higher than that of NBR/PVC blends with non-functionalized SWNT. Dispersion of SWNTs and morphology of NBR/PVC/SWNT nanocomposites were determined by scanning electron microscopy and transmission electron microscopy (TEM) techniques. TEM images illustrated that f-SWNTs were dispersed uniformly in NBR/PVC matrix while non-functionalized SWNTs showed much aggregation. Dynamic mechanical thermal analysis of NBR/PVC/SWNTs nanocomposites was also studied. The outcomes indicated that in the case of f-SWNTs, the intensity of tan ?? peak was lower than that in the case of non-functionalized SWNTs. Meanwhile, the intensity of tan ?? peak reduced when the content of f-SWNTs was increased.     

A hybrid artificial immune algorithm for a realistic variant of job shops to minimize the total completion time

This paper investigates an extended problem of job shop scheduling to minimize the total completion time. With aim of actualization of the scheduling problems, many researchers have recently considered realistic assumptions in their problems. Two of the most applied assumptions are to consider sequence-dependent setup times and machine availability constraints (MACs). In this paper, we deal with a specific case of MACs caused by preventive maintenance (PM) operations. Contrary to the previous papers considering fixed or/and conservative policies, we consider flexible PM operations, in which PM operations may be postponed or expedited as required. A simple technique is employed to schedule production jobs along with the flexible MACs caused by PM. To solve the given problem, we present a novel meta-heuristic method based on the artificial immune algorithm (AIA) incorporating some advanced features. For further enhancement, the proposed AIA is hybridized with a simple and fast simulated annealing (SA). To evaluate the proposed algorithms, we compare our proposed AIA with three well-known algorithms taken from the literature. Finally, we find that the proposed AIA outperforms other algorithms.