Time‐domain hybrid formulations for wave simulations in three‐dimensional PML‐truncated heterogeneous media

We are concerned with the numerical simulation of wave motion in arbitrarily heterogeneous, elastic, perfectly‐matched‐layer‐(PML)‐truncated media. We extend in three dimensions a recently developed two‐dimensional formulation, by treating the PML via an unsplit‐field, but mixed‐field, displacement‐stress formulation, which is then coupled to a standard displacement‐only formulation for the interior domain, thus leading to a computationally cost‐efficient hybrid scheme. The hybrid treatment leads to, at most, third‐order in time semi‐discrete forms. The formulation is flexible enough to accommodate the standard PML, as well as the multi‐axial PML. We discuss several time‐marching schemes, which can be used à la carte, depending on the application: (a) an extended Newmark scheme for third‐order in time, either unsymmetric or fully symmetric semi‐discrete forms; (b) a standard implicit Newmark for the second‐order, unsymmetric semi‐discrete forms; and (c) an explicit Runge–Kutta scheme for a first‐order in time unsymmetric system. The latter is well‐suited for large‐scale problems on parallel architectures, while the second‐order treatment is particularly attractive for ready incorporation in existing codes written originally for finite domains. We compare the schemes and report numerical results demonstrating stability and efficacy of the proposed formulations. Copyright © 2014 John Wiley & Sons, Ltd.     

Drawing in Time: Processes of Design and Fabrication

Drawing embeds time within itself, notating changes in space and duration. For Babak Bryan and Henry Grosman , founding partners of BanG studio in Long Island City, New York: ‘The drawing is a result of process, but it also describes process.’ It is only through this temporal practice that an essential connection is developed between drawing and building. With the widespread adoption of building information modelling (BIM), linear graphic representation finds itself in crisis, challenged by the static inertia of the model. As Bryan and Grosman describe, the well-crafted drawing remains essential to their studio's approach informing the method of ‘making and remaking’.     

Application of mesoporous magnetic carbon composite for reactive dyes removal: Process optimization using response surface methodology

Discharging the effluents of textile wastewaters into potable water resources can endanger the ecosystem, due to their reactivity, toxicity, and chemical stability. In this research, the application of powder activated carbon modified with magnetite nanoparticles (PAC-MNPs) as an adsorbent for removal of reactive dyes (Reactive black 5 (RB5) and reactive red 120 (RR120)) was studied in a batch system. The adsorption performance was evaluated as a function of temperature, contact time and different adsorbent and adsorbate concentrations. The levels of factors were statistically optimized using Box-Behnken Design (BBD) from the response surface methodology (RSM) to maximize the efficiency of the system. The adsorption process of both dyes was fit with the pseudo-second order kinetic and Langmuir isotherm models. The identified optimum conditions of adsorption were 38.7 °C, 46.3 min, 0.8 g/L and 102 mg/L for temperature, contact time, adsorbent dose, and initial dyes concentration, respectively. According to the Langmuir isotherm, the maximum sorption capacities of 175.4 and 172.4 mg/g were obtained for RB5 and RR120, respectively. Thermodynamics studies indicated that the adsorption process of the reactive dyes was spontaneous, feasible, and endothermic. After five cycles, the adsorption efficiency was around 84 and 83% for RB5 and RR120, respectively. A high value of desorption was achieved, suggesting that the PAC-MNPs have a good potential in regeneration and reusability, and also can be effectively utilized in industrial applications. PAC-MNPs also show a good anti-interference potential for removal of reactive dyes in dye-industry wastewaters.     

Investigation of structure and mechanical properties of toughened poly(l‐lactide)/thermoplastic poly(ester urethane) blends

In this study, poly(l ‐lactide) (PLA) is melt‐blended with thermoplastic polyurethane (TPU) to modify the brittleness of PLA. An aliphatic ester‐based TPU was selected in order to have an ester sensitivity for degradation and an inherent biocompatibility. Using this compatible TPU, there was no need to apply problematic compatibilizers, so the main positive properties of PLA such as biocompatibility and degradability were not challenged. The detected microstructure of PLA/TPU blends showed that when the TPU content was lower than 25 wt %, the structure appeared as sea‐islands, but when the TPU content was increased, the morphology was converted to a cocontinuous microstructure. A higher interfacial surface area in the blend with 25 wt % TPU (PLA25) resulted in a higher toughness and abrasion resistance. The various analyses confirmed interactions and successful coupling of two phases and confirmed that melt‐blending of PLA with the aliphatic ester‐based TPU is a convenient, cost‐effective, and efficient method to conquer the brittleness of PLA. The prepared blends are general‐purpose plastics, but PLA25 showed an optimum mechanical strength, toughness, and biocompatibility suitable for a wide range of applications. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43104.     

Synthesis and Characterization of NiO Nano‐Spheres by Templating on Chitosan as a Green Precursor

In this study, nickel oxide was prepared through the calcination of extrusion dripped chitosan/nickel nitrate beads. The morphology and structural properties of the products were studied using various characterization techniques. Uniformly distributed nickel oxide was formed as observed from the studies of surface morphology where the processing parameters play a huge role on the resulting morphology. TEM results have shown that nickel oxide with crystallite sizes of 10–30 nm was obtained. The Fourier‐transform infrared spectra studies show an intense peak at 525 cm^?1, which is attributed to the vibration of Ni–O bond. Furthermore, the XRD results show NiO diffraction peaks correspond to (111), (200), (220), (311), and (222) which indicates that a bunsenite structure with a face‐centered cubic phase was produced in this study. The usage of 500°C as the lower limit in this study is justified due to the complete removal of the templating material as seen in the thermalgravimetric analysis studies. Furthermore, it was obtained that the largest surface area of nickel oxide synthesized using this technique is 48.024 m²/g with pore sizes of 19.843 nm. The usage of chitosan as a green template for the synthesis of nanoparticles has shown promising results which allows a more economical and sustainable approach for the fabrication of nanomaterials.     

Protective properties of PPy‐Au nanocomposite coatings prepared by sonoelectrochemisty and optimized by the Taguchi method

The polypyrrole (PPy) and polypyrrole‐Au (PPy‐Au) nanocomposite films have been sonoelectrochemically synthesized on St‐12 steel electrodes using the galvanostatic technique. Experimental design according to the Taguchi method has been applied to optimize the factors on the synthesis of PPy‐Au nanocomposite coating. Three factors were used to design an orthogonal array L9: Synthesis time (t), Current density (I), and Concentration of HAuCl₄ (C). The synthesized Au nanoparticles during polymerization were characterized by Ultraviolet–visible (UV‐visible) spectroscopy. Characterization of the surfaces was done by scanning electron microscope (SEM), energy dispersive X‐ray spectrum (EDX), and atomic force microscope (AFM). The scanning electron microscopy (SEM) image of PPy shows a smooth surface while PPy‐Au nanocomposite film has a compact morphology. Moreover, energy dispersive X‐ray spectrum (EDX) is evidence for the incorporation of Au nanoparticles. The corrosion protection of coatings was investigated by open circuit potential (OCP) time trends, potentiodynamic polarization technique, and electrochemical impedance spectroscopy (EIS) in a NaCl 3.5% solution. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41087.     

A White Plaque,Associated with Genomic Deletion,Derived from M13KE-Based Peptide Library Is Enriched in a Target-Unrelated Manner during Phage Display Biopanning Due to Propagation Advantage

The nonspecific enrichment of target-unrelated peptides during biopanning remains a major drawback for phage display technology. The commercial Ph.D.^TM-7 phage display library is used extensively for peptide discovery. This library is based on the M13KE vector, which carries the lacZα sequence, leading to the formation of blue plaques on IPTG-X-gal agar plates. In the current study, we report the isolation of a fast-propagating white clone (displaying WSLGYTG peptide) identified through screening against a recombinant protein. Sanger sequencing demonstrated that white plaques are not contamination from environmental M13-like phages, but derive from the library itself. Whole genome sequencing revealed that the white color of the plaques results from a large 827-nucleotide genomic deletion. The phenotypic characterization of propagation capacity through plaque count- and NGS-based competitive propagation assay supported the higher propagation rate of Ph-WSLGYTG clone compared with the library. According to our data, white plaques are likely to arise endogenously in Ph.D. libraries due to mutations in the M13KE genome and should not always be viewed as exogenous contamination. Our findings also led to the conclusion that the deletion observed here might be an ancestral mutation already present in the naïve library, which causes target-unrelated nonspecific enrichment of white clone during biopanning due to propagation advantage.     

Estimation of optimum binder content of recycled asphalt incorporating a wax warm additive using response surface method

This paper presents a new approach to estimate the optimum binder content (OBC) of recycled asphalts (RAs) incorporating a warm mix additive based on the interaction effects of compaction temperature, RA content and binder content using volumetric and strength characterisation. The experimental design was developed using response surface method (RSM) based on central composite design for various compaction temperatures (130–160 °C), RA contents (30–50%) and binder contents (4.9–6.0%). Laboratory tests were performed and analysed to meet the desired volumetric and strength properties according to the Malaysian specifications for the design of dense asphalt mixtures. Statistical analysis and mathematical models proposed by RSM were used to determine the OBC. The results showed that compaction temperature is the most significant factor in determining the OBC. There are minimum differences in the OBC variation of samples incorporating different dosage of RA. The developed model can be used for quick estimation of OBC for various levels of compaction temperature and RA content.     

Modeling the response of HCP polycrystals deforming by slip and twinning using a finite element representation of the orientation space

A continuum approach is presented for predicting the constitutive response of HCP polycrystals using a simple non-hardening constitutive model incorporating both slip and twinning. This has been achieved by considering a physically based methodology for restricting the amount of the twinning activity. A continuum approach is used in modeling the texture evolution that eliminates the need for increasing the number of discrete crystal orientations to account for new orientations created by twinning during deformation. The polycrystal is represented by an orientation distribution function using the Rodrigues parameterization. A total Lagrangian framework is used to model the evolution of microstructure. Numerical examples are used to show the application of the methodology for modeling deformation processes.     

Optical Pattern Switching in Semiconductor Microresonators as All‐Optical Switch

In this paper, we present a spatial perturbation method to control the optical patterns in semiconductor microresonators in the far‐field configuration. We propose a fast all‐optical switch which operates at a low light level. The switching beam controls the behavior of output beams with strong intensities. The method has been applied successfully to different optical patterns such as rolls, squares, and hexagons.