A complete classification of 5-regular circulant graphs that allow cyclic orthogonal double covers

Journal of Algebraic Combinatorics - Graph theory and its applications attract several researchers from different areas of research. It is used to model wide range of systems, for example in...     

A new multi-criteria scenario-based solution approach for stochastic forward/reverse supply chain network design

Analyzing current trends in supply chain management, lead to find unavoidable steps toward closing the loop of supply chain. In order to expect best performance of Closed-Loop Supply Chain (CLSC) network, an integrated approach in considering design and planning decision levels is necessary. Further, real markets usually contain uncertain parameters such as demands and prices of products. Therefore, the next important step is considering uncertain parameters.     

Four-channel optical demultiplexer based on hexagonal photonic crystal ring resonators

In this paper, photonic crystal ring resonators with hexagonal lattice structure are used to design a four-channel optical demultiplexer. The structure size, the average transfer coefficient, the quality factor, and the channel spacing are equal to 424.5 µm², 95.8%, 1943, and 2 nm, respectively. The average crosstalk is also computed to be ?18.11 dB. In this study, the plane wave expansion (PWE) and finite-difference time-domain (FDTD) methods are used, respectively, to characterize the photonic bandgap and to investigate the optical behavior of the structure. The proposed design can be used in dense wavelength division multiplexing (DWDM) systems.     

Cyclotron production and parameters calculation of <Superscript>48</Superscript>V Nitinol stent for renal arteries in brachytherapy

The Nitinol stent was bombarded in a cyclotron at a flux rate of 4 μA/cm² to produce ⁴⁸V via ⁴⁸Ti (p, n) ⁴⁸V reaction. In this study dose distribution of ⁴⁸V radioactive stent was investigated for renal arteries. Version X-2.6 of the MCNP Monte Carlo radiation transport system code was employed to calculate dose distribution around the stent. As ⁴⁸V is a mixed gamma and beta particle emitter, two separate runs of MCNP for both beta and gamma particles were performed and the total deposited dose was acquired by adding the two mentioned values. In order to verify the simulation, the calculated results have been compared with previous published data for the source. Calculated results show high dose gradient near the stent and the maximum amount of dose deposits at the vessel wall. According to (AAPM) TG-60/149 protocol, the dosimetric parameters, including geometry function, G(ρ,z), radial dose function, g _L (ρ), and anisotropy function, F(ρ,z), were also determined.     

On the nonlinear primary resonances of a piezoelectric laminated micro system under electrostatic control voltage

In this article, a comprehensive nonlinear analysis for a piezoelectric laminated micro system around its static deflection is presented. This static deflection is created by an electrostatic DC control voltage through an electrode plate. The micro system beam is assumed as an elastic Euler-Bernoulli beam with clamped-free end conditions. The dynamic equations of this model have been derived by using the Hamilton method and considering the nonlinear inertia, curvature, piezoelectric and electrostatic terms. The static and dynamic solutions have been achieved by using the Galerkin method and the multiple-scales perturbation approach, respectively. The results are compared with numerical and other existing experimental results. By studying the primary resonance excitation, the effects of different parameters such as geometry, material and excitations voltage on the system?s softening and hardening behaviors are evaluated. In a piezoelectrically actuated micro system it was showed that because of existence of curvature and inertia nonlinear terms a small change in excitation amplitude can lead to the formation and expansion of nonlinear response. In this paper, it is demonstrated that by applying an electrostatic DC control voltage, these nonlinearities can be controlled and altered to a linear domain. This model can be used to design a nano or micro-scale smart device.     

Heat transfer analysis in the flow of Walters' B fluid with a convective boundary condition

Radiative heat transfer in the steady two-dimensional flow of Walters' B fluid with a non-uniform heat source/sink is investigated. An incompressible fluid is bounded by a stretching porous surface. The convective boundary condition is used for the thermal boundary layer problem. The relevant equations are first simplified under usual boundary layer assumptions and then transformed into a similar form by suitable transformations. Explicit series solutions of velocity and temperature are derived by the homotopy analysis method(HAM). The dimensionless velocity and temperature gradients at the wall are calculated and discussed.     

Making Oil-in-Water Emulsions by Ultrasound and Stability Evaluation Using Taguchi Method

Oil-in-water emulsions containing 40% wt sunflower oil were prepared using ultrasound with the frequency of 30 kHz. The effect of sonication time, stabilizer concentration, NaCl, and pH of aqueous phase on the stability and particle size distribution of samples was investigated using Taguchi statistical method. The results showed that increasing sonication time decreased mean diameter of droplets and narrowed droplet size distribution curves. NaCl was found to have a positive effect on the stability of samples. More stable emulsions were prepared when using xanthan and pectin together at pH 4.     

Synthesis of Nanocrystalline Polycalix[4]amides Containing Mesogenic Triazole Units and Investigations of Their Thermo Physical Properties and Heavy Metal Sorption Behavior

Novel polyamides bearing calix[4]arene and triazole units, polytriazolecalixamides (PTCAs), were prepared by direct polycondensation of a new bistriazole substituted dicarboxylic acid derivative of calix[4]arene with commercial diamines. The polytriazolecalixamides were obtained in high yields and possessed inherent viscosities in the range of 0.42–0.59 dl/g. These polytriazolecalixamides were readily soluble in polar aprotic solvents such as NMP, DMSO, DMAc at room temperature and in THF by heating. Nanocrystalline structures were determined by XRD patterns and confirmed by DSC as well as TEM and AFM imaging techniques. The photophysical study was performed by UV-absorption spectroscopy and maximum wavelength for each polymer specified in details. Glass transition temperatures were between 134 and 154°C. Thermogravimetric analysis showed that these polyamides displayed high thermal stability ranged from 273 to 312°C at the point of 10% weight loss, and char yields were about 51.4–67.4% at 600°C in nitrogen. All of these nanocrystalline polycalixamides showed promising sorption properties towards transition metal ions such as Cu²⁺, Cr²⁺, Co²⁺, Cd²⁺ and especially Pb²⁺ in solid-liquid extraction which fulfill our needs in synthesizing novel high performance polyamides.     

Thermal and morphological characteristics of solution blended epoxy/NBR compound

Systematic study about the effect of acrylonitrile–butadiene rubber (NBR) concentration on the fracture toughness and thermal behavior of epoxy resin is conducted in this study. NBR is solved in an aromatic hydrocarbon solvent and is added to epoxy resin. We used diethylene-teriamin as the curing agent for epoxy resin. Tensile test results, performed followed by molding procedure, show that the toughness is improved owing to the increase of rubber content. Scanning electron microscopy (SEM) and atomic force microscopy besides thermogravimetric analysis (TG) are used to investigate the epoxy/rubber interface and chemical decomposition of the resultant mixture. The thermal behavior of cured epoxy resin was analyzed via TG instrument at different heating rates. Thermogravimetry curves showed that the thermal decomposition of epoxy system was occurred in only one stage regardless of the rubber content. The apparent activation energies of the rubber/epoxy systems containing 0, 5, and 10 phr of rubber were determined by Flynn–Wall–Ozawa, Kissinger–Akahira–Sunose, and Friedman methods. The results prove that the thermal stability of epoxy resin was decreased with enhancing the rubber content. However, the trend of changing activation energy versus conversions is totally different followed by adding the elastomer to the system compared to neat epoxy resin. Moreover, the results obtained via our proposed facile solution blending method are compared to those of resins modified with nano-powdered elastomer.