Experimental and numerical study of wing boundary layer behavior in propeller flowfield

Journal of Visualization - In this research, the effects of propeller slipstream on wing boundary layer and transition front were studied through wind tunnel tests and numerical analysis. In this...     

Inside-tube solid-phase microextraction as an interlink between solid-phase microextraction and needle device for n-hexane evaluation in air and urine headspace

Monitoring the trace amount of chemicals in various samples remains a challenge. This study was conducted to develop a new solid-phase microextraction (SPME) system (inside-tube SPME) for trace analysis of n-hexane in air and urine matrix. The inside-tube SPME system was prepared based on the phase separation technique. A mixture of carbon aerogel and polystyrene was loaded inside the needle using methanol as the anti-solvent. The air matrix of n-hexane was prepared in a Tedlar bag, and n-hexane vapor was sampled at a flow rate of 0.1 L/min. Urine samples spiked with n-hexane were used to simulate the sampling method. The limit of detection using the inside-tube SPME was 0.0003 μg/sample with 2.5 mg of adsorbent, whereas that using the packed needle was 0.004 μg/sample with 5 mg of carbon aerogel. For n-hexane analysis, the day-to-day and within-day coefficient variation were lower than 1.37%, with recoveries over 98.41% achieved. The inside-tube SPME is an inter-link device between two sample preparation methods, namely, a needle trap device and an SPME system. The result of this study suggested the use of the inside-tube SPME containing carbon aerogel (adsorbent) as a simple and fast method with low cost for n-hexane evaluation.     

Fluorescence “turn-on” chemosensor for the selective detection of zinc ion based on Schiff-base derivative

N,N′-phenylenebis(salicylideaminato) (L) has been used to detect trace amounts of zinc ion in acetonitrile–water solution by fluorescence spectroscopy. The fluorescent probe undergoes fluorescent emission intensity enhancement upon binding to zinc ions in MeCN/H₂O (1:1, v/v) solution. The fluorescence enhancement of L is attributed to the 1:1 complex formation between L and Zn(II), which has been utilized as the basis for selective detection of Zn(II). The linear response range for Zn(II) covers a concentration range of 1.6 × 10^?7 to 1.0 × 10^?5 mol/L, and the detection limit is 1.5 × 10^?7 mol/L. The fluorescent probe exhibits high selectivity over other common metal ions, and the proposed fluorescent sensor was applied to determine zinc in water samples and waste water.     

Sinc-collocation method for solving the Blasius equation

Sinc-collocation method is applied for solving Blasius equation which comes from boundary layer equations. It is well known that sinc procedure converges to the solution at an exponential rate. Comparison with Howarth and Asaithambi's numerical solutions reveals that the proposed method is of high accuracy and reduces the solution of Blasius' equation to the solution of a system of algebraic equations.     

A new approach to improve the order of approximation of the Bernstein operators: theory and applications

This paper presents a new approach to improve the order of approximation of the Bernstein operators. Three new operators of the Bernstein-type with the degree of approximations one, two, and three are obtained. Also, some theoretical results concerning the rate of convergence of the new operators are proved. Finally, some applications of the obtained operators such as approximation of functions and some new quadrature rules are introduced and the theoretical results are verified numerically.     

Ultrasound promoted one-pot synthesis of 2-amino-4,8-dihydropyrano[3,2-b]pyran-3-carbonitrile scaffolds in aqueous media: A complementary ‘green chemistry’ tool to organic synthesis

A green and simple approach to assembling of 2-amino-4,8-dihydropyrano[3,2-b]pyran-3-carbonitrile scaffolds via three-component reaction of kojic acid, malononitrile, and aromatic aldehydes in aqueous media under ultrasound irradiation is described. The combinatorial synthesis was achieved for this methodology with applying ultrasound irradiation while making use of water as green solvent. In comparison to conventional methods, experimental simplicity, good functional group tolerance, excellent yields, short routine, and selectivity without the need for a transition metal or base catalyst are prominent features of this green procedure.     

Applications of classification based on similarities and dissimilarities

In this paper, we first review some definitions and propositions regarding similarities between two objects (2-similarity), or among three or more objects (3-similarity/n-similarity). Then the notion of 3-dissimilarity is introduced and the relationships and connections between 2-dissimilarities and 3-dissimilarities are studied. Through some examples, the applications regarding the concepts of 3-similarity, 4-similarity, and dissimilarity relations will be brought out.     

Photonic crystal narrow filters with two neighboring waveguides and a semiconducting point defect

A tunable filter is demonstrated based on a squared lattice two-dimensional photonic crystal. The filter is formed by a single semiconducting point defect and two neighboring waveguides. Modal properties of the defect modes and the transmittance of the proposed system are analyzed using supercell method and finite difference time domain method, respectively. We show that there is a narrow pass band for each temperature between 218 and 240 Kelvin. The peak of the pass band transmittance and the frequency can be highly tunable with the temperature of an intrinsic semiconducting point defect. Also, we have showed that the frequency and temperature of the desired high transmitted filter do not sensitive on the cavity size.