Toughening mechanisms in bioinspired multilayered materials

Outstanding mechanical properties of biological multilayered materials are strongly influenced by nanoscale features in their structure. In this study, mechanical behaviour and toughening mechanisms of abalone nacre-inspired multilayered materials are explored. In nacre''s structure, the organic matrix, pillars and the roughness of the aragonite platelets play important roles in its overall mechanical performance. A micromechanical model for multilayered biological materials is proposed to simulate their mechanical deformation and toughening mechanisms. The fundamental hypothesis of the model is the inclusion of nanoscale pillars with near theoretical strength (σ_th ~ E/30). It is also assumed that pillars and asperities confine the organic matrix to the proximity of the platelets, and, hence, increase their stiffness, since it has been previously shown that the organic matrix behaves more stiffly in the proximity of mineral platelets. The modelling results are in excellent agreement with the available experimental data for abalone nacre. The results demonstrate that the aragonite platelets, pillars and organic matrix synergistically affect the stiffness of nacre, and the pillars significantly contribute to the mechanical performance of nacre. It is also shown that the roughness induced interactions between the organic matrix and aragonite platelet, represented in the model by asperity elements, play a key role in strength and toughness of abalone nacre. The highly nonlinear behaviour of the proposed multilayered material is the result of distributed deformation in the nacre-like structure due to the existence of nano-asperities and nanopillars with near theoretical strength. Finally, tensile toughness is studied as a function of the components in the microstructure of nacre.     

A sample-level DCNN for music auto-tagging

Multimedia Tools and Applications - Deep convolutional neural networks (DCNNs) has been widely used in music auto-tagging which is a multi-label classification task that predicts tags of audio...     

Fabrication and characterization of polyvinyl chloride mixed matrix membranes containing high aspect ratio anatase titania and hydrous manganese oxide nanoparticle for efficient removal of heavy metal ions: Competitive removal study

In this study, novel polyvinyl chloride (PVC) ultrafiltration mixed matrix membranes (MMMs) containing high aspect ratio anatase titania (ANT) and hydrous manganese oxide (HMO) nanoparticles were synthesized in order to decontaminate cadmium and copper metal ions. ANT and HMO nanoparticles with various loadings in a range of 5-15 were used in the casting solution of MMMs. The characterization of fabricated MMMs was carried out with respect to the structural morphology, hydrophilicity, and composition by scanning electron microscopy (SEM), water contact angle, and Fourier transform infrared spectroscopy (FTIR), respectively. With an increase in the nanoparticle loadings, the change in other membrane characteristics such as mean pore size, pure water flux, and porosity were also evaluated. The results revealed that the mean pore size and water flux increased at a higher loading of ANT and HMO nanoparticles, while the contact angle and porosity of the membranes showed reverse trends. Moreover, the higher flux of pure water was obtained for PVC-ANT MMMs compared to PVC-HMO MMMs because of the larger mean pore size, higher porosity, and hydrophilicity of PVC-ANT MMMs. In this study, the decontamination of cadmium and copper metal ions in single and binary systems of heavy metals was investigated and the effect of Mn²⁺ (as an interfering ion) was also studied. The evaluation of the metal ion removal data demonstrated that the affinity sequence of both the PVC-ANT-15 and PVC-HMO-15 MMMs for heavy metal removal was Cu²⁺ > Cd²⁺ > Mn²⁺ in the single and binary systems. It was found through ultrafiltration (UF) experiments that PVC-ANT MMM was the most efficient membrane in the elimination of heavy metals due to the superior ANT adsorption capacity. However, the overall findings disclosed that both ANT and HMO nanoparticles are suitable candidates for the preparation of MMMs used in cadmium and copper decontamination from aqueous solutions.     

Physical properties of fish gelatin-based bio-nanocomposite films incorporated with ZnO nanorods

Well-dispersed fish gelatin-based nanocomposites were prepared by adding ZnO nanorods (NRs) as fillers to aqueous gelatin. The effects of ZnO NR fillers on the mechanical, optical, and electrical properties of fish gelatin bio-nanocomposite films were investigated. Results showed an increase in Young''s modulus and tensile strength of 42% and 25% for nanocomposites incorporated with 5% ZnO NRs, respectively, compared with unfilled gelatin-based films. UV transmission decreased to zero with the addition of a small amount of ZnO NRs in the biopolymer matrix. X-ray diffraction showed an increase in the intensity of the crystal facets of (10^ī1) and (0002) with the addition of ZnO NRs in the biocomposite matrix. The surface topography of the fish gelatin films indicated an increase in surface roughness with increasing ZnO NR concentrations. The conductivity of the films also significantly increased with the addition of ZnO NRs. These results indicated that bio-nanocomposites based on ZnO NRs had great potentials for applications in packaging technology, food preservation, and UV-shielding systems.     

Modeling and solving a multi-objective supplier quota allocation problem considering transaction costs

Suppliers’ evaluation is a subject, which has attracted the attention of many researchers. The performance of potential suppliers is evaluated against multiple criteria rather than considering a single factor such as cost or quality. One of the major objectives of suppliers’ evaluation is to determine the optimal quota assigned to each supplier while needing to replenish an order. This problem has been studied by many researchers as a multi-objective problem. The usual objectives are minimizing the purchasing cost, rejected units, and late delivered units. However, in a few researches maximizing the evaluation scores of the selected suppliers is considered as fourth objective. In this paper, we present a model with five objectives including minimizing the transaction costs of purchasing from suppliers as well as the four addressed objectives. We convert the model to a single objective one using the well-known weighting method, solve it utilizing two meta-heuristic algorithms, and analyze the efficiency of the heuristics. The reason why we utilize the meta-heuristic algorithms is that the problem is proved to be an NP-hard one.     

$$H_{\infty }$$ Performance Analysis of 2D Continuous Time-Varying Delay Systems

This paper deals with the problem of \(H_{\infty }\) performance analysis of 2D continuous time-varying delay systems described by Roesser model. Using a simple Lyapunov–Krasovskii functional, a new delay-dependent stability criterion is derived in terms of linear matrix inequalities. The obtained result is then extended to the problem of \(H_{\infty }\) performance analysis. Several examples are provided in order to illustrate the effectiveness of our results.     

Effects of flow history on oil entrapment in porous media: An experimental study

The effect of flow history on fluid phase entrapment during immiscible two‐phase flow in Hele‐Shaw cells packed with spherical and crushed glass beads is investigated. The wetting fluid is injected into an initially oil saturated cell at a well‐defined capillary number. It is observed that the size and shape of the trapped clusters strongly depend on the history of flooding such that less oil was trapped in the medium when the injecting capillary number gradually increased to the final maximum capillary number compared to the case when the injection was started and maintained constant at the maximum capillary number. In addition, a comprehensive series of experiments were conducted to delineate the effects of the capillary number on the phase entrapment. Contrary to previously published data, our experimental data reveal that the residual oil saturation depends on capillary number nonmonotonically. A physically based relationship to scale the capillary desaturation curve is proposed. © 2014 American Institute of Chemical Engineers AIChE J, 61: 1385–1390, 2015     

A statistical approach to engineer a biocomposite formulation from biofuel coproduct with balanced properties

A 3²‐full factorial design of experiment (DOE) and regression modeling were implemented together as a practical approach to attain a distillers' grains‐filled biocomposite with balanced mechanical and physical properties. The effects of compatibilizer and lubricant on tensile strength, flexural modulus, impact strength and melt flow index of the biocomposites were studied. Analysis of variance (ANOVA) was implemented to develop least square regression models containing statistically significant main effects (linear and quadratic) and interaction effect. The developed models showed good predictability for the new measurements. The statistical approach adopted in this work including overlaying contour plots of the response surfaces in the studied level domain was effective in highlighting an optimized region that leads to balanced mechanical and physical properties. © 2014 The Authors Journal of Applied Polymer Science Published by Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40443.     

NBTI and hot-carrier effects in accumulation-mode Pi-gate pMOSFETs

Negative bias temperature instability (NBTI) and hot-carrier induced device degradation in accumulation-mode Pi-gate pMOSFETs have been studied for different fin widths ranging from 20 to 40 nm. The NBTI induced device degradation is more significant in narrow devices. This result can be explained by enhanced diffusion of hydrogen at the corners in multiple-gate devices. Due to larger impact ionization, hot-carrier induced device degradation is more significant in wider devices. Finally, hot-carrier induced device degradation rate is highest under stress conditions where V_GS = V_TH.