High‐accuracy upwind method using improved characteristics speeds for incompressible flows

In this study, the Nervier–Stokes equations for incompressible flows, modified by the artificial compressibility method, are investigated numerically. To calculate the convective fluxes, a new high‐accuracy characteristics‐based (HACB) scheme is presented in this paper. Comparing the HACB scheme with the original characteristic‐based method, it is found that the new proposed scheme is more accurate and has faster convergence rate than the older one. The second order averaging scheme is used for estimating the viscose fluxes, and spatially discretized equations are integrated in time by an explicit fourth‐order Runge–Kutta scheme. The lid driven cavity flow and flow in channel with a backward facing step have been used as benchmark problems. It is shown that the obtained results using HACB scheme are in good agreement with the standard solutions. Copyright © 2015 John Wiley & Sons, Ltd.     

4E analysis and tri-objective optimization of a triple-pressure combined cycle power plant with combustion chamber steam injection to control NOx emission

This article presents a novel triple-pressure combined cycle power plant (CCPP) with a heat recovery steam generator (HRSG) configured with heat exchangers of multiple pressure levels, same as the real case. In addition, combustion chamber steam injection is added to the top cycle in order to reduce hazardous emissions. The research investigates energy, exergy, economic, and environmental aspects of the system to initiate sustainable development in said areas. A thorough parametric study is carried out to evaluate the effects of steam injection and other decision variable on emissions and system performance. Then, the total cost rate and the CO₂ index are minimized while maximizing the second law efficiency via a tri-objective optimization using the genetic algorithm. The outcome of the economic analysis is that the HRSG has the maximum total cost rate among all the components, namely 0.1673 $/s. The environmental impact  assessments indicate that the CO₂ and NO emission has considerable molar fractions of 0.035 and 6.88?×?10^?4, respectively. As a result of the tri-objective optimization, a 3D Pareto Frontier is presented, which pointed out the maximum attainable exergy efficiency is 50.32%, as well as the minimum total cost rates of 8.04 $/s and CO₂ index of 0.34 kg/kWh. Finally, the scatter distribution of major decision variables revealed the optimum range of decision variables in which the optimum points of the Pareto Frontier are obtained. Accordingly, the scatter distribution showed that 46 kg s^?1 is the optimum value for steam injection flow rate in terms of efficiency, cost and emission optimization.

     

Optimal design of microphone array in a planar circular configuration by genetic algorithm enhanced beamforming

Journal of Thermal Analysis and Calorimetry - This paper investigated an optimized-microphone array configuration based on a genetic algorithm (GA) to improve the map resolution of output...     

A combined experimental and density functional theory study on the complexation ability of 15-crown-5 with Li+, Na+, K+, and NH4 + cations

The complexation processes among Li⁺, Na⁺, K⁺, and NH₄ ⁺ cations with the macrocyclic ligand, 15-crown-5 (15C5) have been studied in acetonitrile–methanol binary mixtures at different temperatures using conductometric method. The stability constants of the resulting 1:1 complexes were calculated from the computer fitting of the molar conductance–mole ratio data at various temperatures. The values of thermodynamic parameters ( $ \Updelta H_{\text{c}}^{^\circ } $ and $ \Updelta S_{\text{c}}^{^\circ } $ ) for the formation of the complexes were obtained from temperature dependence of the stability constants of complexes using van’t Hoff plots. In addition, a theoretical study has been carried out using density functional theory to obtain the stability of the complexes and the geometrical structure of the 15C5 and its complexes with Li⁺, Na⁺, K⁺ and NH₄ ⁺ cations in the gas phase. We compared the experimental data with those obtained by quantum chemistry calculations to investigate the effect of the solvent on complexation process.     

Multiparameter Sensor Chip with Barium Strontium Titanate as Multipurpose Material

It is well known that biochemical and biotechnological processes are strongly dependent and affected by a variety of physico‐chemical parameters such as pH value, temperature, pressure and electrolyte conductivity. Therefore, these quantities have to be monitored or controlled in order to guarantee a stable process operation, optimization and high yield. In this work, a sensor chip for the multiparameter detection of three physico‐chemical parameters such as electrolyte conductivity, pH and temperature is realized using barium strontium titanate (BST) as multipurpose material. The chip integrates a capacitively coupled four‐electrode electrolyte‐conductivity sensor, a capacitive field‐effect pH sensor and a thin‐film Pt‐temperature sensor. Due to the multifunctional properties of BST, it is utilized as final outermost coating layer of the processed sensor chip and serves as passivation and protection layer as well as pH‐sensitive transducer material at the same time. The results of testing of the individual sensors of the developed multiparameter sensor chip are presented. In addition, a quasi‐simultaneous multiparameter characterization of the sensor chip in buffer solutions with different pH value and electrolyte conductivity is performed. To study the sensor behavior and the suitability of BST as multifunctional material under harsh environmental conditions, the sensor chip was exemplarily tested in a biogas digestate.     

Tuning the primary resonances of a micro resonator,using piezoelectric actuation

Microbeam dynamics is important in MEMS filters and resonators. In this research, the effect of piezoelectric actuation on the resonance frequencies of a piezoelectrically actuated capacitive clamped-clamped microbeam is studied. The microbeam is sandwiched with piezoelectric layers throughout its entire length. The lower piezoelectric layer is exposed to a combination of a DC and a harmonic excitation voltage. The DC electrostatic voltage is applied to prevent the doubling of the excitation frequency. The traditional resonators are tuned using DC electrostatic actuation, which tunes the resonance frequency only in backward direction on the frequency domain. The proposed model enables tuning the resonance frequencies in both forward and backward directions. For small amplitudes of harmonic excitation and high enough quality factor, the frequency response curves obtained by the shooting method are validated with those of the multiple time scales technique. Unlike the perturbation technique, which imposes limitation on both the amplitude of the harmonic excitation and the quality factor to be applicable, the shooting method can be applied to capture the periodic attractors regardless of how big the amplitude of harmonic excitation and the quality factor are.     

2-Isoxazolidineethanols: an NMR study of the effect of intramolecular H-bonding on the population of nitrogen invertomers and inversion process

A series of (betaR,5R)- and (betaR,5S)-2,5-disubstituted isoxazolidines: 5-(substituent)-beta-phenyl-2-isoxazolidineethanols, have been prepared by asymmetric nitrone cycloaddition reactions and their NMR spectra recorded over a wide range of temperatures. The spectra at low temperatures indicate the presence of the (betaR,5S) diasteromer almost exclusively as a single invertomer having trans disposition of the substituents at N(2) and C(5), while the (betaR,5R) diasteromer remained as a mixture of two interconverting invertomers in deuterated chloroform. The effect of H-bonding - intramolecular in CDCl(3) and intermolecular in CD(3)OD - on the population ratio of the invertomers and nitrogen inversion process has been investigated. The nitrogen inversion barriers are determined using complete line-shape analysis, and their dependence on solvent is discussed. Due to steric factor the trans-invertomers are found to be more stable than their cis counterparts.     

Dansyl‐peptides matrix‐assisted laser desorption/ionization mass spectrometric (MALDI‐MS) and tandem mass spectrometric (MS/MS) features improve the liquid chromatography/MALDI‐MS/MS analysis of the proteome

Peptide tagging is a useful tool to improve matrix‐assisted laser desorption/ionization tandem mass spectrometric (MALDI‐MS/MS) analysis. We present a new application of the use of the dansyl chloride (DNS‐Cl). DNS‐Cl is a specific primary amine reagent widely used in protein biochemistry. It adds a fluorescent dimethylaminonaphthalene moiety to the molecule. The evaluation of MALDI‐MS and MS/MS analyses of dansylated peptides shows that dansylation raises the ionization efficiency of the most hydrophilic species compared with the most hydrophobic ones. Consequently, higher Mascot scores and protein sequence coverage are obtained by combining MS and MS/MS data of native and tagged samples. The N‐terminal DNS‐Cl sulfonation improves the peptide fragmentation and promotes the generation of b‐fragments allowing better peptide sequencing. In addition, we set up a labeling protocol based on the microwave chemistry. Peptide dansylation proved to be a rapid and cheap method to improve the performance of liquid chromatography (LC)/MALDI‐MS/MS analysis at the proteomic scale in terms of peptide detection and sequence coverage. Copyright © 2010 John Wiley & Sons, Ltd.     

An optical redox chemical sensor for determination of iodide

A novel optical sensor based on a redox reaction for the determination of iodide has been developed. The optode membrane is constructed by immobilization of methyltrioctylammonium chloride on triacetylcellulose polymer. The exchange of chloride as counter ion with iodate in the membrane changes the color to yellow, when it is placed in acidic solution of iodide. The sensor can readily be regenerated by 0.1 mol L⁻¹ NaOH in less than 15 s. The optode has a linear range of 3.94 × 10⁻⁶ to 5.51 × 10⁻⁵ mol L⁻¹ of iodide ions with a limit of detection 7.44 × 10⁻⁷ mol L⁻¹. The relative standard deviation for eight replicate measurements of 3.94 × 10⁻⁶ and 1.57 × 10⁻⁵ mol L⁻¹ of iodide was 2.83 and 1.38%, respectively. The sensor was successfully applied to the determination of iodide in tablet, powdered milk and urine samples.     

Textural and adsorption characteristics of carbon xerogel adsorbents for removal of Cu (II) ions from aqueous solution

Resorcinol–formaldehyde (RF) carbon xerogels were synthesized using different resorcinol/sodium carbonate catalyst molar ratios (R/C = 50, 200, 500 and 1000) and heat treatment temperatures (HTT = 500, 600 and 700) under no external gas flow. The carbon adsorbents were extensively characterized by CHO content, FTIR, TEM and nitrogen adsorption isotherm at 77 K. The effect of R/C, HTT and oxygen content on the development of porosity within carbons was studied. Also, the adsorption capacity of these adsorbents was investigated by the removal of copper (II) ions from aqueous solution using single bottle test. The produced carbon xerogels exhibit a micro-mesopore character, but with different extents depending on the mechanism of porosity generation in relation to R/C, HTT and oxygen functional groups. Results show that the optimum conditions to obtain porous carbon xerogels were the highest R/C = 500–1000 in combination with carbonization preferably at 600 or 700 °C. Single bottle removal of Cu (II) ions indicated the developed carbons with appreciable capacity (q_u = 32–130 mg/g) which are controlled by the surface area and surface chemical nature (acidic O-functional groups). Finally, the present investigation provides a new, nanoporous type of porous carbon adsorbents with high adsorption capacity for removal of heavy metals from wastewater media.