Nonlinear optical and structural properties of M@C N endohedrals (M = Li,Ca and Sc,N = 60 and 70)

We have investigated the static (ω = 0) and frequency-dependent nonlinear optical (NLO) properties of the M@C _N endohedrals (M = Li, Ca, Sc, N = 60 and 70) using the SSH (Su–Schrieffer–Heeger) approximation and sum-over-state (SOS) approach. Also, we study the effects of displacement and alkali, alkaline earth and lanthanide metal atoms and type of cage on the hyperpolarisabilities of the M@C _N endohedrals. The hyperpolarisability magnitudes and spectra are in agreement with experiment and the work of others using the SSH approximation. Our results indicate that the cage-type effect on the NLO spectra of M@C _N endohedrals is dramatic. Also, atom type has little effect on the highest peak value. These relationships between the atom and cage type and hyperpolarisability values may be beneficial to experimentalists when designing new NLO materials with large NLO responses.     

On the performance of density functional schemes for computing the static dipole polarizability of 4d transition-metal monohalides

This article presents the static dipole polarizabilities of 4d transition-metal monohalides in the framework of density functional theory. The behavior of a large number of density functionals, including various types of the local spin density approximation (LSDA), the generalized gradient approximation (GGA), meta GGA (MGGA), hybrid GGA (HGGA), and hybrid meta GGA (HMGGA), has been assessed in polarizability calculations. The highly accurate CCSD(T) methodology is used to benchmark a variety of functionals. Our results indicate that there is a large variation in performance of the various functionals of each type in the calculation of the dipole polarizability. It turned out that, in the LSDA class, SVWN5 gives better results than SVWN3 for the reference values. Of the GGA methods, BP86 and BPW91 give the best results for our data set, followed by G96LYP. The TPSS functional is the best method of the MGGA class, followed by the VSXC and BB95 functionals. Moreover, the B98 and mPW1PW91 functionals are the best methods of the HGGA lineage, predicting the most accurate static dipole polarizabilities. Finally, TPSS1KCIS and PBE1KCIS are the best methods of the HMGGA functionals for that purpose. In general, it was found that the HGGA and HMGGA functionals provide the best performance.     

On monoids over which all generators satisfy a flatness property

This paper addresses conditions under which all generators in the category of right S-acts (where S is a monoid) satisfy a flatness property. There are characterizations for monoids over which all generators satisfy a flatness property α where α can stand for freeness, projectivity, strong flatness, Condition (P), principal weak flatness and torsion freeness. To our knowledge, the problem has not been studied for other flatness properties such as weak flatness, Condition (E) and regularity. The present paper addresses this gap.     

SiO2‐POCl2 nanoparticles promoted the synthesis of novel structure of 2,3‐dihydrooxazole derivatives

Silica‐POCl₂ was used as promoter for the three‐component reaction of ethyl 3‐phenyl glycidate, aniline derivatives, and dimethylformamide (DMF), which leads to the synthesis of ethyl 4‐phenyl‐3‐aryl‐2,3‐dihydrooxazole‐5‐carboxylate derivatives. The desired product was obtained in high yields.     

A cost-effective form-stable PCM composite with modified paraffin and expanded perlite for thermal energy storage in concrete

Journal of Thermal Analysis and Calorimetry - High thermal conductivity in phase change materials (PCM) is preferred in thermal energy storage (TES) systems. Carbon additives are considered as...     

Numerical prediction of humidification process in planar porous membrane humidifier of a PEM fuel cell system to evaluate the effects of operating and geometrical parameters

In present study, a numerical model is employed to investigate the effects of different operating parameters and channel geometry on the performance of membrane humidifier. Simulations are performed by a commercial CFD code and based on user defined functions. Three-dimensional counter-flow humidifier model for a gas-to-gas case is considered. Results show that an increase in porosity or permeability leads to better humidification. Moreover, increase in inlet temperature of dry and wet channels as well as inlet mass flowrate of water vapor would enhance humidifying process. On the other hand, by reduction in inlet mass flowrate of gas channel and thickness of the porous medium in membrane, better humidifier performance would be achieved. To investigate the geometric parameters, three different channel types including stepped, sinusoidal and zigzag are considered. It is found that stepped geometry has the best performance in humidifying.

     

Copper chromite decorated on nitrogen-doped graphene aerogel as an efficient catalyst for thermal decomposition of ammonium perchlorate particles

Journal of Thermal Analysis and Calorimetry - The present study reports numerical simulations of water-based Al2O3 nanofluid flowing in a 2D channel with a heated wall-mounted obstacle. The...     

Isometries between completely regular vector-valued function spaces

Periodica Mathematica Hungarica - In this paper, first we study surjective isometries (not necessarily linear) between completely regular subspaces A and B of $$C_0(X,E)$$ and $$C_0(Y,F)$$ where X...     

Highly stretchable,self-adhesive,and self-healable double network hydrogel based on alginate/polyacrylamide with tunable mechanical properties

A number of synthetic hydrogels suffer from low mechanical strength. Despite of the recent advances in the fabrication of tough hydrogels, it is still a great challenge to simultaneously construct high stretchability, and self-adhesive and self-healing capability in a hydrogel. Herein, a new type of double network hydrogel was prepared based on irreversible cross-linking of polyacrylamide chains and Schiff-base reversible cross-linking between glycidyl methacrylate-grafted ethylenediamine and oxidized sodium alginate (OSA). The combination of both cross-linkings and their synergistic effect provided a novel hydrogel with high strength, stretchable, rapid self-healing, and self-adhesiveness to different material. Besides, the hydrogels with diverse OSA content could maintain their original shapes after loading–unloading tensile test. The resulting hydrogel has a great potential in various fields for supporting and load-bearing substance.