Synthesis of a Starchy Photosensitive Material for Additive Manufacturing of Composites Using Digital Light Processing

In this study, digital light processing (DLP) was used to achieve 3D-printed composite materials containing photosensitive resin blended with starch and hemp fibers. The synthesis of 3D-printed composites was performed without heating, according to various material combinations ranging from pure photosensitive resin to a mixture of three phases, including resin, starch, and hemp fibers, with the weight content for each reinforcing phase reaching up to a third of the formulation. The morphology, composition, and structure of the 3D-printed composites were assessed using infrared spectroscopy, laser granulometry, X-ray diffraction, and optical and scanning electron microscopy. In addition, thermal behavior and mechanical performance were studied using calorimetry, differential scanning calorimetry, and tensile testing combined with high-speed optical imaging. The results showed that the post-curing step is a leading factor for improving the mechanical performance of the 3D-printed composites. In addition, hemp fiber or starch did not alter the tensile strength. However, the largest reinforcing effect in terms of stiffness improvement was obtained with starch. Additionally, starchy composites demonstrated the strongest dependence of heat capacity on operating temperature.     

Asymptotic–Newton method for solving incompressible flows

In this paper we present a comparative study of three non-linear schemes for solving finite element systems of Navier–Stokes incompressible flows. The first scheme is the classical Newton–Raphson linearization, the second one is the modified Newton–Raphson linearization and the last one is a new scheme called the asymptotic–Newton method. The relative efficiency of these approaches is evaluated over a large number of examples. © 1997 John Wiley & Sons, Ltd.     

Algebraic Modeling of the Turbulent Heat Fluxes Using the Elliptic Blending Approach—Application to Forced and Mixed Convection Regimes

The present paper focuses on the application of the elliptic blending approach to the modeling of turbulent heat fluxes, in order to account for the influence of solid boundaries. The analytical justification of the extension to the temperature–pressure gradient correlation term of this approach, originally applied to the velocity–pressure gradient, is given. The assumption of weak equilibrium enables the derivation of two new algebraic flux models valid down to the wall. It is shown, with both a priori tests and computations in forced and mixed convection regimes, that the predictions of the streamwise heat-flux and the temperature variance are significantly improved by the use of elliptic blending. A particular attention is devoted to the issue of the modeling of the correlation length scale involved in the elliptic blending for the heat fluxes, which is shown to have a significant influence on the predictions.     

Purification and Biochemical Characterization of a Novel Alkaline (Phospho)lipase from a Newly Isolated Fusarium solani Strain

An extracellular lipase from Fusarium solani strain (F. solani lipase (FSL)) was purified to homogeneity by ammonium sulphate precipitation, gel filtration and anion exchange chromatography. The purified enzyme has a molecular mass of 30 kDa as estimated by sodium dodecyl sulphate polyacrylamide gel electrophoresis. The 12 NH₂-terminal amino acid residues showed a high degree of homology with a putative lipase from the fungus Necteria heamatoccocae. It is a serine enzyme, like all known lipases from different origins. Interestingly, FSL has not only lipase activity but also a high phospholipase activity which requires the presence of Ca²⁺ and bile salts. The specific activities of FSL were about 1,610 and 2,414 U/mg on olive oil emulsion and egg-yolk phosphatidylcholine as substrates, respectively, at pH 8.0 and 37 °C. The (phospho)lipase enzyme was stable in the pH range of 5–10 and at temperatures below 45 °C.     

Concomitant polymorphism in the stereoselective synthesis of a β‐benzyl‐β‐hydroxyaspartate analogue

Two concomitant polymorphs, (I) and (II), of a β‐benzyl‐β‐hydroxyaspartate analogue [systematic name: dibenzyl 2‐benzyl‐2‐hydroxy‐3‐(4‐methylphenylsulfonamido)succinate], C₃₂H₃₁NO₇S, crystallize from a mixture of ethyl acetate and cyclohexane at ambient temperature. The structure of (I) has triclinic (P) symmetry and that of (II) monoclinic (P2₁/c) symmetry. Both crystal structures are made up of a stacking of homochiral racemic dimers (2S,3S and 2R,3R) which are internally connected by a similar R₂²(9) hydrogen‐bonding pattern consisting of intermolecular N—H...O and O—H...O hydrogen bonds. The centroid of the racemic dimer lies on an inversion centre. The main structural difference between the two polymorphs is the conformational orientation of two of the four aromatic rings present in the molecule. Polymorph (II) is found to be twinned by reticular merohedry with twin index 3 and twin fractions 0.854 (1) and 0.146 (1).     

Numerical Simulation of Coherent Structures over Plant Canopy

This paper reports large eddy simulations of the interaction between an atmospheric boundary layer and a canopy (representing a forest cover). The problem is studied for a homogeneous configuration representing the situation encountered above a continuous forest cover, as well as for a heterogeneous configuration representing the situation similar to an edge or a clearing in a forest. The numerical results reproduces correctly all the main characteristics of this flow as reported in the literature: the formation of a first generation of coherent structures aligned transversally with the wind flow direction, the reorganization and the deformation of these vortex tubes into horse-shoe structures. The results obtained when introducing a discontinuity in the canopy (reproducing a clearing or a fuel break in a forest), are compared with the experimental data collected in a wind tunnel; here, the results confirm the existence of a strong turbulence activity inside the canopy at a distance equal to 8 times the height of the canopy, referenced in the literature as the Enhance Gust Zone (EGZ) characterized by a local peak of the skewness factor.     

2-Halogeno-N-phenacylimidazolium salts and their reactions with active methylene species,arylamines and thiocyanate ions

This study describes the reactivity of 2-halogeno-N-phenacylimidazolium salts towards active methylene species, arylamines and thiocyanate ions. The 2-chloro-N-phenacylimidazolium salt undergoes unexpected reactions in the presence of active methylene species and a tertiary amine as the base. The reaction of 2-bromo-N-phenacylimidazolium salts with arylamines led to a mixture of the corresponding 2-(arylamino)-N-phenacylimidazolium salts and imidazolone. The reaction of 2-bromo-N-phenacylimidazolium bromide with KSCN led to the corresponding imidazole-2-thione. The crystal structures of five compounds are reported.     

A nonlinear parabolic equation with a nonlocal boundary term

A nonlinear parabolic problem with a nonlocal boundary condition is studied. We prove the existence of a solution for a monotonically increasing and Lipschitz continuous nonlinearity. The approximation method is based on Rothe’s method. The solution on each time step is obtained by iterations, convergence of which is shown using a fixed-point argument. The space discretization relies on FEM. Theoretical results are supported by numerical experiments.