A study in the developing region of square jet

The developing region of a turbulent square jet is investigated using high-resolution particle image velocimetry (PIV). The mean velocity and turbulence stresses are presented in various horizontal planes, along the jet centerline covering the initial region of the jet as well as the transition to the self-similar region. To study the flow structure away from the central plane, velocity measurements in two additional horizontal planes, one located halfway from the jet central plane toward the edge and the other at the edge of the square jet, are also examined. Analysis of the instantaneous velocity fields reveal the presence of an arrow-like feature in the square jet due to the higher instability generated in the jet shear layer compared with a round jet. To elucidate the imprints of the vortex structures present in the jets, a swirling strength-based vortex identification methodology is applied on a large ensemble of instantaneous velocity fields. Statistical analysis of the number of vortex cores, and their size and rotational strength in the measurement plane is undertaken. Vortex population at the edge was found to be very different compared with that in the central plane.     

Synthesis of monodisperse and high moment nickel–iron (NiFe) nanoparticles using modified polyol process

Monodisperse NiFe nanoparticles with different compositions have been successfully synthesized by surfactant free simple modified polyol method. In the process, polyethylene glycol was used as a solvent media and it has been found to play a key role to act as a reducing agent as well as a stabilizer simultaneously. XRD, TEM, and EDS analysis techniques were used to characterize the synthesized nanoparticles. TEM images displayed formation of a thin oxide layer around the nanoparticles, and confirmed by detection of some oxygen element using EDS measurement. The magnetic properties of the synthesized NiFe NPs samples were measured by vibrating sample magnetometer (VSM) at room temperature, and the saturation magnetization value was found to be iron content dependent.     

Three-component reactions of isocyanides, dialkyl acetylenedicarboxylates, and trans-cinnamoyl chlorides for the synthesis of highly functionalized 2-vinyl furans

Abstract  

In this study, we present a convenient and efficient method for the synthesis of novel, highly substituted 2-vinyl furans using a three-component reaction. The zwitterions generated from the reaction of isocyanides and dialkyl acetylenedicarboxylates are reacted with trans-cinnamoyl chlorides to produce the desired products in good yields.     

Simple and efficient synthesis of 5‐substituted 1‐H‐tetrazoles using metal‐modified clay catalysts

The synthesis of 5‐substituted 1‐H‐tetrazoles based on reaction of a series of aromatic nitriles with sodium azide was investigated. The reaction was catalyzed by modified montmorillonite K‐10 including Cu²⁺, Fe³⁺, Ni²⁺, and Zn²⁺ metal ions. The best results obtained by Mont‐K10‐Cu catalyst. The catalysts were reused several times without loss of their activity. The present procedure offers advantages such as a shorter reaction time, simple workup, recovery, and reusability of the catalyst. © 2011 Wiley Periodicals, Inc. Heteroatom Chem 22:168–173, 2011; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.20672     

Theoretical study of reorientation and torque of liquid crystal molecules under influence of external electric field and experimentally generation of spatial optical soliton beam and getting a sharp switching in chiral nematic liquid crystal

Liquid crystals (LC) are anisotropic materials which experience a torque if an electric field is present. This field can be due to an external voltage or to the presence of a light beam. Reorientation due to light leads to non-linear behavior in the optical behavior. Due to this kind of nonlinearity therefore it is possible to generate optical spatial soliton beam in LC by bias voltage or without it and interestingly chiral nematic liquid crystals has a opportunity to generate spatial optical solitons without the need for a bias voltage. In this paper we also demonstrate that a sharp switching of the helix structure occurs when the spatial soliton is launched in the middle of two regions where soliton generation is favorable. Due to the optical nonlinearity, the helical structure becomes asymmetric and a sharp switching in one direction can be obtained. Moreover, in this paper, the torque and reorientation of the liquid crystal and the change in angular momentum of the light are discussed.     

Multiplexed ladar fiber-optic sensor system

Abstract

Practical considerations in the design of an optically multiplexed ladar fiber-optic linear-position sensing system are discussed, including network architecture, bus fiber count, fault location, sensor separation, and network efficiency. The results of a six-channel multiplexing experiment using a single laser diode are presented.     

Fixed Points of Quasi (f,g)-Nonexpansive Multivalued Mapping

Fixed point theorems for hybrid pair of single valued and multivalued R-subweakly commuting maps are proved.     

Preconcentration of trace amounts of formaldehyde from water, biological and food samples using an efficient nanosized solid phase, and its determination by a novel kinetic method

This work presents a sensitive method for the determination of formaldehyde. It is based on the use of modified alumina nanoparticles for its preconcentration, this followed by a new and simple catalytic kinetic method for its determination. Alumina nanoparticles were chemically modified by immobilization of 2,4-dinitrophenylhydrazine via sodium dodecyl sulfate as a surfactant. The formaldehyde retained on the modified adsorbent was then desorbed and determined via its catalytic effect on the oxidation of thionine by bromate ion. Factors affecting the preconcentration and determination of formaldehyde have been investigated. Formaldehyde can be detected in the range from 0.05 to 38.75 μg L^?1, and no serious interferences have been observed. The method has been successfully applied to the quantitation of formaldehyde in water, food, and certain biological samples.