Plane wave analysis of acoustic wedges using the boundary-condition-transfer algorithm

The present work delineates the applicability of the boundary-condition-transfer algorithm for analyzing the performance of the acoustic wedge. The theoretical model, based on the plane wave acoustical coupling between two interacting ducts of variable cross-sectional area, outlines the simplicity as well as the usefulness of the current approach. The proposed model assumes bulk reaction and hence a wave propagation in the wedge material. An asymptotic solution using the Peano-Baker series of matrix calculus is derived with the aid of an inherently stable boundary condition transfer (BCT) algorithm. The proposed method is validated extensively against the available literature in order to establish the utility of this elemental approach over its much more complex and time consuming counterparts like FEM and BEM.     

Size effect in nanocrystalline manganites La<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript><Emphasis Type="Italic">A</Emphasis><Subscript>x</Subscript>MnO<Subscript>3</Subscript> (<Emphasis Type="Italic">A</Emphasis>=Ag,Sr)

Nanocrystalline samples of the manganites La_0.9Ag_0.1MnO₃, La_0.7Ag_0.3MnO₃, and La_0.7Sr_0.3MnO₃ were synthesized through pyrolysis and isothermally annealed. The atomic, subatomic, and magnetic structures of these manganites were studied using magnetic, x-ray, and neutron diffraction measurements. Increasing the annealing temperature from 600 to 1200°C coarsens the grains from 30–40 to 600–700 nm in size. All the samples studied have rhombohedral structure and are ferromagnets. The Curie temperature decreases for the samples doped by silver and increases for the samples doped by strontium as the anneal temperature is increased. The magnetization of the Mn ions increases with nanoparticle size in all the three systems, which indicates the presence of a size effect.     

Formanilide and carbanilide from aniline and carbon dioxide

Earlier syntheses of formamides from the catalytic hydrogenation of CO₂ in the presence of amines were only successful for the preparation of dialkylformamides. After an analysis of the reason for the failure of the reaction using aniline as a starting material, formanilide has been prepared, for the first time, from CO₂, H₂ and aniline with the use of 1,8-diazabicyclo[5.4.0]undec-7-ene. Omission of the H₂ reductant causes the selectivity to switch to the production of carbanilide (1,3-diphenylurea).     

Sobolev regularity of the second biharmonic problem on a rectangle

Summary It is proved that for any f &esin; L²(Ω) the weak solution of the second biharmonic problem on a rectangle satisfies u&esin; H⁴(Ω). The proof uses the decomposition of the problem into two Poisson equations and a general condition for H⁴-regularity via the eigenvalues and eigenfunctions of second order elliptic operators.     

Synthesis,photophysical, and electrochemical properties of wide band gap tetraphenylsilane-carbazole derivatives: Effect of the substitution position and naphthalene side chain

Four tetraphenylsilane-carbazole derivatives with wide bandgaps (3.38–3.55 eV) were synthesized. The effects of the substitution position and of the presence of naphthalene groups on the photophysical, electrochemical and thermal properties were investigated. The derivatives exhibited maximum absorption peaks ranging from 293 to 304 nm and maximum emission peaks ranging from 347 to 386 nm. Changing the carbazole substitution position on the tetraphenylsilane did not significantly change the photophysical and electrochemical properties. However, p-substituted compounds exhibited higher glass transition temperatures than m-substituted compounds. Naphthalene groups with bulky structures had extended the conjugation lengths that red-shifted both the absorption and emission spectra. The LUMO level was decreased, which reduced the optical bandgap and triplet energy level. However, the naphthalene groups significantly improved the thermal stability by increasing the glass transition temperature of the compounds.     

The Synergistic Effect of a Mixed Surfactant (Tween 80 and SDBS) on Wettability Alteration of the Oil Wet Quartz Surface

The synergistic effect of a new combination of Tween 80 and sodium dodecylbenzenesulfonate (SDBS) surfactants has been studied for wettability alteration of a reservoir rock. The contact angle decreased substantially for the aqueous solution of the mixed surfactant on a crude oil aged quartz substrate when compared to water and individual surfactants viz. SDBS and Tween 80. This established synergism between anionic and non-ionic surfactants. The optimal salinity for reduction of the contact angle has been figured out. The rheological effect of the mixed surfactant solution on the wettability alteration has been investigated. Adsorption of crude components at the solid–fluid interfaces has been observed to visualize the activity at the micro scale. Quantification of adsorption for the mixed surfactant on sand has been studied to meet the economical aspect. Reaction aspects of the mixed surfactant–quartz–crude oil system have been interpreted from FTIR. Functional groups present in the system have also been enquired.     

Core–shell functionalized MWCNT/poly(m‐aminophenol) nanocomposite with large dielectric permittivity and low dielectric loss

Core–shell carboxyl‐functionalized multiwall carbon nanotube (c‐MWCNT)/poly(m‐aminophenol) (PmAP) nanocomposite were prepared through in‐situ polymerization of m‐aminophenol (m‐AP) in the presence of MWCNTs, and explicated as a dielectric material for electronic applications. The formation of thin PmAP layer on individual c‐MWCNT with excellent molecular level interactions at interfaces was confirmed by morphological and spectroscopic analyses. Here we conducted a comparative study of the dielectric performances of PmAP based nanocomposite films with pristine MWCNTs and c‐MWCNTs as fillers. Compared to PmAP/MWCNT nanocomposites, the PmAP/c‐MWCNT nanocomposites exhibited higher dielectric permittivity and lower dielectric loss. The well dispersed c‐MWCNTs in PmAP/c‐MWCNT nanocomposite produce huge interfacial area together with numerous active polarized centers (crystallographic defects), which in turn intensified the Maxwell‐Wagner‐Sillars (MWS) effect based on excellent molecular level interactions and thus, produce large dielectric permittivity (8810 at 1 kHz). The percolation threshold of PmAP/c‐MWCNT nanocomposites is found lower than that of the PmAP/MWCNT nanocomposites, which could be attributed to homogeneous distribution of c‐MWCNTs and strong c‐MWCNT//PmAP interfacial interactions in the nanocomposites. Copyright © 2016 John Wiley & Sons, Ltd.     

Insight into the Multistate Emissive N,P-doped Carbon Nano-Onions: Emerging Visible-Light Absorption for Photocatalysis

Carbon dots (CDs) have become one of the most emerging materials as an alternative solar light-induced photocatalyst in contrast to traditional metal-based systems. However, one of the major challenges is the lack of visible light absorption. Herein, we have fabricated unique N, P-co-doped CDs with a self-assembled onion-like layered structure by using a bottom-up facile synthesis technique from chitosan gel and phosphoric acid as molecular precursors. This typical layered structure of N, P-co-doped carbon nano onions (N, P-CNOs), with an average size of 25–50 nm, displays an enhanced visible light absorption. Detailed structural and elemental characterizations confirm the extensive aromatic domain with P-containing surface functionalities, while electrochemical study clarifies the lowering of band gaps as well as the creation of new electronic states in comparison to the pristine N-CDs. Furthermore, the intrinsic structural features are correlated with the underpinning photophysical processes by steady-state and time-resolved fluorescence spectroscopy. In addition, steady-state polarized emission and thermo-responsive PL properties have been carried out to unveil further the structure-property correlation of N, P-CNOs, and their comparative study with pristine N-CDs at the different excitation wavelengths. Finally, N, P-CNOs exhibit efficient visible-light-induced photocatalysis, and the detailed mechanistic study is carried out by trapping the photogenerated species in an aqueous medium. The prepared N, P-CNOs displayed an excellent visible-light photocatalytic performance over MB dye with a degradation efficiency of 75.8% within 120 min along with a degradation rate constant of ∼0.0109 min⁻¹. It is concluded that the easy to synthesize and low-cost N, P-CNOs with a unique morphology hold great potential for application in visible-light photocatalysis.