Voltage-controlled transmission through a dielectric slab doped with quantum dot molecules

Transmission and reflection of an electromagnetic pulse through a dielectric slab doped with the quantum dot molecules are investigated. It is shown that the transmission and reflection coefficients depend on the inter-dot tunneling effect and can be simply controlled by applying a gate voltage without any changing in the refractive index or thickness of the slab. Such simple controlling prepares an active beam splitter which can be used in all optical switching, optical limiting, and other optical systems.     

Free vibration analysis of two-dimensional functionally graded cylindrical shells

In this paper, the free vibration of a two-dimensional functionally graded circular cylindrical shell is analyzed. The equations of motion are based on the Love’s first approximation classical shell theory. The spatial derivatives of the equations of motion and boundary conditions are discretized by the methods of generalized differential quadrature (GDQ) and generalized integral quadrature (GIQ). Two kinds of micromechanics models, viz. Voigt and Mori–Tanaka models are used to describe the material properties. To validate the results, comparisons are made with the solutions for FG cylindrical shells available in the literature. The results of this study show that the natural frequency of the material can be modified in order to meet the expected results through manipulation of the constituent volume fractions. A comprehensive comparison is then drawn between ordinary and 2-D FG cylindrical shells.     

Numerical Simulation of Pressure-Swirl Spray Dispersion by Using Eulerian-Lagrangian Method

To gain a general understanding of atomization and sheet breakup processes, the interaction of pressure-swirl hollow-cone sprays and a quiescent medium was investigated computationally. The spray characteristics of Iso-octane (n-C₈H₁₈) with high pressure-swirl injector in the ambient conditions are modeled. The Linearized Instability Sheet Atomization (LISA) model has been used to describe the primary breakup processes of the spray. Sauter Mean Diameter, sheet thickness and exit velocity were computed as the results of primary breakup. Disintegration of large drops is simulated using Taylor analogy breakup (TAB) model in which the Rosin-Rammler distribution is used. Evaporation and collision models are deactivated in this study. The model considers the transient behavior of the pre-spray and steady-state behavior of the main spray for three various injection pressures and liquid mass flow rates. Qualitative and quantitative comparisons between the simulated and experimentally measured results were made. The numerical simulations can successfully demonstrate the spray characteristics, such as spray tip penetration, drop sizes and overall spray structure.     

Presentation of a new index for estimation of aromaticity in halo‐ and cyanobenzenes: The role of potential energy in aromaticity

A linear correlation has been obtained between average values of Hamiltonian kinetic energy ( ) and potential energy ( ) calculated at the bond critical points using atoms in molecules method. This relation was used to introduce a new index ( ) for estimation of aromaticity in halo‐ and cyanobenzenes. Potential energy has different terms such as attraction between nuclei and electrons, also repulsion of electrons which affect the inertia and mobility of electrons, respectively. Therefore, contribution of potential energy in this relation must be controlled. Contribution of potential energy in aromaticity has been managed using a fitting parameter. This parameter was obtained by fitting the aromaticity stabilization energy data with values of aromaticity calculated by index for halo‐ and cyanobenzenes. The contribution of potential energy in index is complete when molecule is nonaromatic and is negligible when molecule is antiaromatic. Indeed, molecule is aromatic when contribution of potential energy in index lies between above limits. © 2013 Wiley Periodicals, Inc.     

Experimental Study on the Elastic–plastic Transitions of the Hetero-structured High Pressure Die Casting Mg–Al-RE Alloy

Background

High pressure die casting (HPDC) Mg alloy has a hetero-structure in which the microstructures gradually coarsen from the casting surface to the interior, leading to the different elastic–plastic (E-P) transitional behaviors among the layers.

Objective

In this paper, we quantitively determined the diverse E-P transitions among the HPDC layers and related them to the microstructural evolution.

Methods

To investigate independently the E-P transitional behavior of the layer, the surface, middle, and central layers were deliberately sliced in sequence from the casting surface to the interior of the HPDC Mg-4Al-5.7RE (in wt.%) component. The onset and the end of E-P transition in each layer were quantitively determined by cyclic tensile test and Kocks-Mecking analysis, respectively.

Results

It was found that the plastic deformation for all layers occurred in the first unloading loop near zero strain, indicating the start of the E-P transition. With increasing strain, the E-P transition ended first in the middle layer at 0.0081 strain due to the lowest fraction of the second phases and ended last at the small-grained surface layer at 0.0090 strain. Excluding the twinning-dependent anelastic strain, the E-P transitions ended in advance at the strains of 0.0059 and 0.0062 in the middle and surface layer, respectively.

Conclusions

A combination of cyclic tensile test and Kocks-Mecking analysis provided a method to quantitively determine the diverse E-P transitions among the HPDC layers resulted from the hetero-structure regarding grains, the second phases, and twins.

     

Nanostructured Base Electrochemical Sensor for Simultaneous Quantification and Voltammetric Studies of Levodopa and Carbidopa in Pharmaceutical Products and Biological Samples

A novel carbon paste electrode modified with carbon nanotubes and 5‐amino‐2′‐ethyl‐biphenyl‐2‐ol (5AEB) was fabricated. The electrochemical study of the modified electrode, as well as its efficiency for electrocatalytic oxidation of levodopa (LD) and carbidopa (CD), is described. Cyclic voltammetry (CV) was used to investigate the redox properties of this modified electrode at various scan rates. The apparent charge transfer rate constant, k_s, and transfer coefficient, a, for electron transfer between 5AEB and CPE were calculated as 17.3 s^?1 and 0.5, respectively. Square wave voltammetry (SWV) exhibits a linear dynamic range from 2.5×10^?7 to 2.0×10^?4 M and a detection limit of 9.0×10^?8 M for LD.     

Efficient One-Pot Synthesis of Polyhydroquinoline Derivatives Using Silica Sulfuric Acid as a Heterogeneous and Reusable Catalyst Under Conventional Heating and Energy-Saving Microwave Irradiation

An efficient Hantzsch four-component condensation reaction for the synthesis of polyhydroquinoline derivatives was reported under two conditions: solvent-free conventional heating and energy-saving microwave irradiation. The process is simple and environmentally benign, and the use of a heterogeneous and reusable catalyst, high yields, and short reaction times are the key features of this protocol.