Microfluidic and Nanofluidic Cavities for Quantum Fluids Experiments

The union of quantum fluids research with nanoscience is rich with opportunities for new physics. The relevant length scales in quantum fluids, ³He in particular, are comparable to those possible using microfluidic and nanofluidic devices. In this article, we will briefly review how the physics of quantum fluids depends strongly on confinement on the microscale and nanoscale. Then we present devices fabricated specifically for quantum fluids research, with cavity sizes ranging from 30 nm to 11?μm deep, and the characterization of these devices for low temperature quantum fluids experiments.     

Vibration of circular plate with multiple eccentric circular perforations by the Rayleigh-Ritz method

The free vibration of a circular plate with multiple perforations is analyzed by using the Rayleigh-Ritz method. Admissible functions are assumed to be separable functions of radial and tangential coordinates. Trigonometric functions are assumed in the circumferential direction. The radial shape functions are the boundary characteristic orthogonal polynomials generated following the Gram-Schmidt recurrence scheme. The assumed functions are used to estimate the kinetic and the potential energies of the plate depending on the number and the position of the perforations. The eigenvalues, representing the dimensionless natural frequencies, are compared with the results obtained using Bessel functions, where the exact solution is available. Moreover, the eigenvectors, which are the unknown coefficients of the Rayleigh-Ritz method, are used to present the mode shapes of the plate. To validate the analytical results of the plates with multiple perforations, experimental investigations are also performed. Two unique case studies that are not addressed in the existing literature are considered. The results of the Rayleigh-Ritz method are found to be in good agreement with those from the experiments. Although the method presented can be employed in the vibration analysis of plates with different boundary conditions and shapes of the perforations, circular perforations that are free on the edges are studied in this paper. The results are presented in terms of dimensionless frequencies and mode shapes.     

Analysis of cold expanded fastener holes subjected to short time creep: Finite element modelling and fatigue tests

The beneficial effects of cold expansion have been well documented in previous studies, yet the performance of cold expanded plates exposed to elevated temperatures is an area of technical interest. In this research, finite element (FE) simulations along with experimental fatigue tests have been carried out to investigate the effect of exposure to elevated temperature on residual stress distribution and subsequent fatigue life of cold expanded fastener holes. According to the obtained results, creep stress relaxation occurs due to exposure to 120 °C for 50 h. FE results demonstrate a non-uniform residual stress relaxation regime through the plate thickness around the cold expanded hole and the fatigue test results show that the subsequent fatigue lives have significantly decreased.     

An optical chemical sensor for thorium (IV) determination based on thorin

A selective method for the determination of thorium (IV) using an optical sensor is described. The sensing membrane is prepared by immobilization of thorin–methyltrioctylammonium ion pair on triacetylcellulose polymer. The sensor produced a linear response for thorium (IV) concentration in the range of 6.46 × 10^?6 to 9.91 × 10^?5 mol L^?1 with detection limit of 1.85 × 10^?6 mol L^?1. The regeneration of optode was accomplished completely at a short time (less than 20 s) with 0.1 mol L^?1 of oxalate ion solution. The relative standard deviation for ten replicate measurements of 2.15 × 10^?5 and 8.62 × 10^?5 mol L^?1 of thorium was 2.71 and 1.65%, respectively. The optode membrane exhibits good selectivity for thorium (IV) over several other ionic species and are comparable to those obtained in case of spectrophotometric determination of thorium using thorin in solution. A good agreement with the ICP-MS and spiked method was achieved when the proposed optode was applied to the determination of thorium (IV) in dust and water samples.     

Influence of the Thermal Barrier Coatings Design on the Oxidation Behavior

The properties of two different types of thermal barrier coatings(TBCs) were compared to improve the surface characteristics on high temperature components.These TBCs consisted of a duplex TBC and a five-layered functionally graded TBC.NiCrAlY bond coats were deposited on a number of Inconel-738LC specimens using high velocity oxy-fuel spraying(HVOF) technique.For duplex coating,a group of these specimens were coated with yttria stabilized zirconia(YSZ) using plasma spray technique.Functionally graded NiCrA...     

Application of ion-engineered Persian Gulf seawater in EOR:effects of different ions on interfacial tension,contact angle,zeta potential,and oil recovery

In this study,we initially performed interfacial tension(IFT)tests to investigate the potential of using the Persian Gulf sea-water(PGSW)as smart water with dif...     

A linear genetic programming approach for the prediction of solar global radiation

In this article, the linear genetic programming (LGP) is utilized to predict the solar global radiation. The solar radiation is formulated in terms of several climatological and meteorological parameters. Comprehensive databases containing monthly data collected for 6 years (1995–2000) in two nominal cities in Iran are used to develop LGP-based models. Separate models are established for each city. To verify the performance of the proposed models, they are applied to estimate the solar global radiation of test data of database. The contribution of the parameters affecting the solar radiation is evaluated through a sensitivity analysis. The results indicate that the LGP models give precise estimations of the solar global radiation and significantly outperform traditional angstrom’s model.     

Thermal Integration of Sulfuric Acid and Continuous Catalyst Regeneration of Naphtha Reforming Plants

An optimal reactor design is proposed that simultaneously improves the naphtha reforming reactor performance and increases sulfur trioxide production. In this new configuration, the naphtha reforming process as an endothermic reaction is coupled with the oxidation reaction of sulfur dioxide, which is an exothermic reaction. The differential evolution optimization technique is applied to maximize the produced amounts and yields of aromatics and hydrogen. The results obtained with the optimized thermally coupled reactor are compared with those of the conventional and thermally coupled reactors, proving the superiority of the proposed configuration.     

A comparative study of subgrid-scale stress models in the context of a transitional boundary layer

In this paper, four important subgrid-scale (SGS) stress models are investigated in order to assess their predictive performance on modeling of the SGS physics. The analysis is conducted using the a priori method based on a comprehensive direct numerical simulation (DNS) data set of a transitional boundary layer flow over a flat plate. The study includes examination of the correlations between the modeled SGS stress tensor and that directly computed from the DNS data, investigation of the effects of filter sizes on modeled SGS stresses, and evaluation of forward and backward scatter of the kinetic energy of the flow in the transitional and turbulent regions.     

Study effect of different parameters on the sulphate sorption onto nano alumina

The aim of this research work is to investigate sorption characteristic of modified nano alumina (n-Al) for the removal of SO₄^2? from aqueous solutions and wastewater. The sorption of SO₄^2? by batch method is carried out. The optimum conditions of sorption were found to be: a sorbent dose of 0.3 g in 100 ml of SO₄^2?, contact time of 35 min, pH = 5. In optimum condition, removal efficiency was 85.6% for the SO₄^2?. Three equations, i.e. Morris–Weber, Lagergren and pseudo second order have been tested to track the kinetics of removal process. The Langmuir, Freundlich and D–R are subjected to sorption data to estimate sorption capacity. It can be concluded that n-Al has potential to remove SO₄^2? ions from aqueous solutions at different concentrations. It was found that the temperature has positive effect on the process and negative ΔG values indicated thermodynamically feasible and spontaneous nature of the sorption. Positive value of ΔS reveals the increased randomness at the solid–solution interface during the fixation of the ion on the active sites of the sorbent. The effect of other anions was studied and it was found the existence of them in the solution has considerable effect on the sulphate removal.