Fractional factorial design for the optimization of supercritical carbon dioxide extraction of La, Ce and Sm ions from a solid matrix using bis(2,4,4-trimethylpentyl)dithiophosphinic acid + tributylphosphate

In this study, La³⁺, Ce³⁺ and Sm³⁺ were removed from a solid matrix using supercritical CO₂ which contained bis(2,4,4-trimethylpentyl)dithiophosphinic acid (Cyanex 301) as a chelating agent and tributylphosphate (TBP) as a co-extractant. The fractional factorial design, 2⁵⁻¹, was employed to optimize the SFE of these ions from spiked filter paper matrices. Effect of five experimental factors: amount of Cyanex 301, flow rate, temperature, pressure and amount of TBP and each factor at two levels on the SFE of these ions were studied and optimized. The results showed that these ions could be quantitatively extracted from the solid matrix at amount of Cyanex 301 of 0.14 g, flow rate of 4 ml min⁻¹, 313 K, 250 bar and amount of TBP of 30 μl. Finally, by employing a regression analysis a model was proposed. Results showed that obtained recoveries are similar to those predicted by the model.     

Generation and transmission of dispersion tolerant 10-Gbps RZ-OOK signal for radio over fiber link

We proposed and demonstrated the generation and transmission of 10-Gbps return-to-zero ON/OFF keying (RZ-OOK) signal using a new technique without pulse carving at transmitter.The new technique is char...     

Novel sensing and joint beam and null steering based resource allocation for cross-tier interference mitigation in cognitive femtocell networks

Wireless Networks - Cognitive radios and femtocell networks are gaining much popularity due to the formers ability to carry out unlicensed transmission in licensed bands and the latter’s...     

Optimal and near-optimal algorithms for multiple fault diagnosiswith unreliable tests

We consider the problem of constructing optimal and near-optimal multiple fault diagnosis (MFD) in bipartite systems with unreliable (imperfect) tests. It is known that exact computation of conditional probabilities for MFD is NP hard. The novel feature of our diagnostic algorithms is the use of Lagrangian relaxation and subgradient optimization methods to provide: 1) near optimal solutions for the MFD problem and 2) upper bounds for an optimal branch and bound algorithm. The proposed method is illustrated using several examples. Computational results indicate the following: 1) our algorithm has superior computational performance to the existing algorithms (approximately three orders of magnitude improvement over the algorithm by Z. Binglin et al. (1993)); 2) near optimal algorithm generates the most likely candidates with a very high accuracy; 3) our algorithm can find the most likely candidates in systems with as many as 1000 faults     

The finite volume spectral element method to solve Turing models in the biological pattern formation

It is well known that reaction-diffusion systems describing Turing models can display very rich pattern formation behavior. Turing systems have been proposed for pattern formation in various biological systems, e.g. patterns in fish, butterflies, lady bugs and etc. A Turing model expresses temporal behavior of the concentrations of two reacting and diffusing chemicals which is represented by coupled reaction-diffusion equations. Since the base of these reaction-diffusion equations arises from the conservation laws, we develop a hybrid finite volume spectral element method for the numerical solution of them and apply the proposed method to Turing system generated by the Schnakenberg model. Also, as numerical simulations, we study the variety of spatio-temporal patterns for various values of diffusion rates in the problem.     

Ultra trace quantification of chromium(VI) in food and water samples by highly sensitive catalytic adsorptive stripping voltammetry with rubeanic acid

A simple and highly selective and sensitive catalytic adsorptive stripping voltammetric procedure for determination of ultra trace levels of chromium(VI) on hanging mercury drop electrode is reported. The method is based on the adsorptive preconcentration of the Cr(III)–dithiooxamide (rubeanic acid) complex and the utilization of the catalytic reaction in the presence of nitrate. At optimized conditions the calibration graph is linear from 0.01 to 6 ng/ml and detection limit is 0.002 ng/ml for accumulation time of 50 s. The interference of some common ions was studied and this method has been applied to the determination of chromium in food and waste water samples with satisfactory results.     

Free piston Stirling engines: A review

This paper presents a detailed review on free piston Stirling engines (FPSEs) technology. Generally, the Stirling engines can be categorized into two broad classes comprising kinematic and dynamic converters among which FPSEs are known as the dynamic type. Other well-known dynamic Stirling converters are Fluidyne and thermosacoustic engines among which the thermosacoustic ones are the most advanced Stirling converters recently presented. In this research, the dynamic Stirling engines are first introduced and reviewed. Then, the review work is directed toward the FPSEs, one of the most reliable dynamic Stirling converters utilized in different applications such as combined heat and power systems (CHPs). Subsequently, the working principles of different types of FPSEs and their performance are summarized. Next, several manufactured FPSEs, as well as their corresponding features and applications, are discussed. Finally, the article is conducted to analysis and modeling approaches of FPSEs. Accordingly, linear and nonlinear analytical techniques of FPSEs are introduced, and some comparative data are provided to verify the modeling schemes. Then, various design parameters affecting the engine performance are introduced and studied. The outcomes of this review work demonstrate the potential of FPSEs for different applications and reveal that the perturbation-based model is likely the most comprehensive nonlinear method for modeling and design of the FPSEs.     

Fabrication of superhydrophobic unplasticized poly(vinyl chloride)/nanosilica sheets using Taguchi design methodology

This study introduces a relatively simple technique for the manufacture of superhydrophobic coatings on polymeric surfaces. Plastics such as unplasticized poly(vinyl chloride) (UPVC ) do not have a strong hydrophobic nature that is characterized by their low contact angles. Techniques of both increasing surface roughness and lowering surface energy are required to change their hydrophilicity to superhydrophobicity. In the present study, a coating of a low‐surface‐energy thermoplastic polyurethane (TPU ) was spin‐coated with chemically treated nanosilica to reduce the surface energy of UPVC . Nanosilica particles were embedded on the surface using a hot‐press. Taguchi design was used to optimize multiple processing parameters. Samples spin‐coated with 10 g L^?1 nanosilica suspension in ethanol at a rate of 400 rpm for 5 s and then hot‐pressed at 155 °C under 2 atm (203 kPa ) for 4 min had a contact angle of ca 157° and sliding angle of ca 6°, which are characteristic of superhydrophobic surfaces. Atomic force microscopy (AFM) and scanning electron microscopy (SEM ) imaging showed that these superhydrophobic surfaces were highly rough with nanoscale features. Peel test and SEM analysis showed that silica nanoparticles embedded in the TPU coating were more stable than particles immobilized on UPVC sheet without TPU coating, proving that a layer of more flexible coating can improve the longevity of superhydrophobic surfaces manufactured using this facile method. © 2016 Society of Chemical Industry     

Effect of non-uniform parallel channel on performance of passive direct methanol fuel cell

In this paper, the effects of current collector on passive direct methanol fuel cell's (passive DMFC) performance and removing CO₂ gas is studied. For this purpose, a single cell with two arrangements of current collector in anode and cathode side is considered. In first arrangement, non-uniform parallel channels with 53.76% open ratio is used in the anode side and a perforated flow field with 34.5% open ratio is applied in the cathode side. In second arrangement, uniform parallel channels with 42.28% open ratio has been used in both anode and cathode sides. At the first arrangement, a maximum power of 20 mW cm⁻² in 4 M methanol concentrations and in the second arrangement a maximum power of 17.7 mW cm⁻² in 5 M methanol concentrations has been obtained. Furthermore, it is shown that using the current collector with non-uniform parallel channels is more effective in removing CO₂ gas than other parallel channels.     

A comparative study on the effects of material blending method on the physico‐mechanical properties of WPCs made from MDF dust

The present study was carried out to investigate the effect of material ‐ blending method and filler content on the physical and mechanical properties of medium density fiberboard (MDF) dust/PP composites. In the sample tests preparation, 40, 50, and 60 wt % of MDF dust were used as lignocellulosic material. Test samples were made to measure the influence of material ‐ blending method and MDF dust content on water absorption (WA), thickness swelling (TS), modulus of elasticity (MOE), modulus of rupture (MOR), tensile strength, tensile modulus, and withdrawal strengths of fasteners. The mechanical properties of the test panels significantly decreased with increasing MDF dust contents due to the reduction of interface bond between the fiber and polymer matrix. The WA and TS values also increased by increasing the amount of MDF dust. So with the increase in the MDF dust content, there are more water residence (high hydroxyl groups (? OH) of cellulose and hemicelluloses) sites, thus more water is absorbed, so it can reduce mechanical strength. Furthermore, the results indicated that the physical and mechanical properties of samples made with melt ‐ blend method were more acceptable than those of dry ‐ blend method. Field emission scanning electron microscopy micrographs also showed that the polymer and the filler phase mixed better in the melt ‐ blend method. On the basis of the findings of this research, it appears evident that certain amount of MDF dust material with suitable material ‐ blending method can be used in manufacturing of wood–plastic composites for providing good physical and mechanical properties. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40513.