Simulation of an orifice scrubber performance based on Eulerian/Lagrangian method

A mathematical model based on Eulerian/Lagrangian method has been developed to predict particle collection efficiency from a gas stream in an orifice scrubber. This model takes into account Eulerian approach for particle dispersion, Lagrangian approach for droplet movement and particle-source-in-cell (PSI-CELL) model for calculating droplet concentration distribution. In order to compute fluid velocity profiles, the normal k− turbulent flow model with inclusion of body force due to drag force between fluid and droplets has been used. Experimental data of Taheri et al. [J. Air Pollut. Control Assoc. 23 (11) (1973) 963] have been used to test the results of the mathematical model. The results from the model are in good agreement with the experimental data. After validating the model the effect of operating parameters such as liquid to gas flow rate ratio, gas velocity at orifice opening, and particle diameter were obtained on the collection efficiency.     

Effect of Ti-ion non-stoichiometry on microstructure and microwave dielectric characteristic of Li<Subscript>2</Subscript>ZnTi<Subscript>3</Subscript>O<Subscript>8</Subscript> ceramics

This paper studies the microwave dielectric properties, microstructure, vibration and densification of Li₂ZnTi_3+xO_8+2x (\(- 0.04 \le {\text{x}} \le +0.06\)) ceramics, manufactured via a conventional mixed oxide route. The X-ray diffraction and Raman spectroscopy revealed the unit cell parameter and cation ordering in LZT non-stoichiometry in their vibrational modes. The densification and phase composition were characterized by the EDX and SEM methods. It was found that a slight Ti vacancy can improve the relative density to the maximum value (96.2%). The XRD results showed that the second phase of TiO₂ in the Li₂ZnTi_3.06O_8.12 composition is formed. The sintered samples were detected in the microwave frequency range by using the resonance technique. The \({\text{~}}{\tau _f}\) values of the ceramics within Ti excess adjusted to near zero. The Li₂ZnTi_2.96O_7.92 ceramic showed the best relative density, single phase and best microwave dielectric \({\varepsilon _r}~={\text{ }}25.98\), Q?×?f?=?61,000 GHz, \({\tau _f}={\text{ }} - 17.4{\text{ ppm/}}^\circ {\text{C}}\) sintered at 1100 °C for 4 h.     

Shape memory response of porous NiTi shape memory alloys fabricated by selective laser melting

Porous NiTi scaffolds display unique bone-like properties including low stiffness and superelastic behavior which makes them promising for biomedical applications. The present article focuses on the techniques to enhance superelasticity of porous NiTi structures. Selective Laser Melting (SLM) method was employed to fabricate the dense and porous (32–58%) NiTi parts. The fabricated samples were subsequently heat-treated (solution annealing?+?aging at 350?°C for 15?min) and their thermo-mechanical properties were determined as functions of temperature and stress. Additionally, the mechanical behaviors of the samples were simulated and compared to the experimental results. It is shown that SLM NiTi with up to 58% porosity can display shape memory effect with full recovery under 100?MPa nominal stress. Dense SLM NiTi could show almost perfect superelasticity with strain recovery of 5.65 after 6% deformation at body temperatures. The strain recoveries were 3.5, 3.6, and 2.7% for samples with porosity levels of 32%, 45%, and 58%, respectively. Furthermore, it was shown that Young’s modulus (i.e., stiffness) of NiTi parts can be tuned by adjusting the porosity levels to match the properties of the bones.

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Modeling and simulation of photovoltaic (PV) system during partial shading based on a two-diode model

This paper proposes accurate partial shading modeling of photovoltaic (PV) system. The main contribution of this work is the utilization of the two-diode model to represent the PV cell. This model requires only four parameters and known to have better accuracy at low irradiance level, allowing for more accurate prediction of PV system performance during partial shading condition. The proposed model supports a large array simulation that can be interfaced with MPPT algorithms and power electronic converters. The accurateness of the modeling technique is validated by real time simulator data and compared with the three other types of modeling, namely Neural Network, P&O and single-diode model. It is envisaged that the proposed work is very useful for PV professionals who require simple, fast and accurate PV model to design their systems.     

Piezoelectric-Based Degradation Assessment of a Pipe Using Fourier and Wavelet Analyses

Abstract:   One of the most important issues in today's oil and gas industry is the access to an effective and reliable damage-detection system for health monitoring of pipeline systems. Vibration-based damage-detection systems have been contemplated in the past with varying success. This article demonstrates the effectiveness of a series of coupled mathematical/engineering approaches that are used to detect damage in pipes, reliably and accurately. The proposed health-monitoring methodology is based on monitoring the vibration response of pipes using piezoelectric sensors. Finite element analysis is used to simulate the response of a healthy pipe, as well as pipes with various size damage. The degradations (defects) have been assumed to exist on the pipes in the form of local corrosion, simulated by reducing the wall thickness in various areas around the circumference of pipes. Fast Fourier transformation (FFT), FFT integration, wavelet transformation (WT), and wavelet packet transformation (WPT) methods are used to examine the pipe's dynamic response to an impacting force. Novel "Damage indices" expressions are developed based on the evaluation of vibration-signal-induced energies. As it will be seen, the damage indices can effectively establish the existence of defects. Moreover, the energy indices can distinguish the differences among various size defects. It was observed that all the approaches considered could essentially establish the existence of the defects with good accuracy; however, incorporation of the WT and WPT energy components yielded a more precise identification of damage in the pipes examined.     

Identification of essential amino acids within the proposed CuA binding site in subunit II of Cytochrome c oxidase

To explore the nature of proposed ligands to the CuA center in cytochrome c oxidase, site-directed mutagenesis has been initiated in subunit II of the enzyme. Mutations were introduced into the mitochondrial gene from the yeast Saccharomyces cerevisiae by high velocity microprojectile bombardment. A variety of single amino acid substitutions at each of the proposed cysteine and histidine ligands (His-161, Cys-196, Cys-200, and His-204 in the bovine numbering scheme), as well as at the conserved Met-207, all result in yeast which fails to grow on ethanol/glycerol medium. Similarly, all possible paired exchange Cys,His and Cys,Met mutants show the same phenotype. Furthermore, protein stability is severely reduced as evidenced by both the absence of an absorbance maximum at 600 nm in the spectra of mutant cells and the underaccumulation of subunit II, as observed by immunolabeling of mitochondrial extracts. In the same area of the protein, a variety of amino acid substitutions at one of the carboxylates previously implicated in binding cytochrome c, Glu-198, allow (reduced) growth on ethanol/glycerol medium, with normal intracellular levels of protein. These results suggest that a precise folding environment of the CuA site within subunit II is essential for assembly or stable accumulation of cytochrome c oxidase in yeast.     

Nitric oxide-20-hydroxyeicosatetraenoic acid interaction in the regulation of K+ channel activity and vascular tone in renal arterioles

The present study examined whether inhibition of P4504A enzyme activity and the formation of 20-HETE contributes to the activation of K+ channels and vasodilator effects of nitric oxide (NO) in renal arterioles. Addition of an NO donor to the P4504A2 enzyme that produces 20-HETE increased visible light absorbance at 440 nm indicating that NO binds to heme in this enzyme. NO donors also dose-dependently inhibited the formation of 20-HETE in microsomes prepared from renal arterioles. In patch-clamp experiments, NO donors increased the open-state probability of a voltage-sensitive, large-conductance (195+/-9 pS) K+ channel recorded with cell-attached patches on renal arteriolar smooth muscle cells. Blockade of guanylyl cyclase with [1H-[1,2,4]Oxadiazolo[4,3-a] quinoxalin-1-one] (ODQ, 10 micromol/L), or cGMP-dependent kinase with 8R,9S,11S-(-)-9-methoxycarbamyl-8-methyl-2,3,9,10-tetrahydro-8, 11-epoxy-1H,8H,11H-2,7b,11a-trizadibenzo-(a,g)-cy-cloocta-(c ,d, e)-trinden-1-one (KT-5823) (1 micromol/L) did not alter the effects of NO on this channel. In contrast, inhibition of the formation of 20-HETE with 17-octadecynoic acid (1 micromol/L) activated this channel and masked the response to NO. Preventing the NO-induced reduction in intracellular 20-HETE levels also blocked the effects of NO on this channel. Sodium nitroprusside (SNP) increased the diameter of renal interlobular arteries preconstricted with phenylephrine to 80+/-4% of control. Blockade of guanylyl cyclase with ODQ (10 micromol/L) attenuated the response to SNP by 26+/-2%; however, fixing 20-HETE levels at 100 nmol/L reduced the response by 67+/-8%. Blockade of both pathways eliminated the response to SNP. These results indicate that inhibition of the formation of 20-HETE contributes to the activation of K+ channels and the vasodilator effects of NO in the renal microcirculation.     

Utilization of the finite element and Monte Carlo model for simulating the recrystallization of inhomogeneous deformation of copper

In this paper the finite element method and Monte Carlo model are coupled to simulate the grain size distribution of inhomogeneously deformed copper wire after annealing. The wire flat rolling process is chosen as an inhomogeneous deformation. The finite element method is utilized to calculate the stored energy distribution due to deformation and is then used in Monte Carlo model to obtain the distribution of grain size. A new relationship is developed to simulate the nucleation in recrystallization phenomenon. The modeling results are compared with the experimental results and an acceptable agreement is achieved.     

Modelling of metal flow during hot forging with regard to microstructural aspects

A mathematical model has been proposed for evaluation of velocity and temperature fields in hot forging operations for axisymmetric parts. The model can be applied to determine forging load, strain rate, strain and temperature distributions. In addition, the effects of temperature and strain rate on metal flow have been considered through simultaneous modelling of dynamic phase transformation within the deforming metal. Hot forging experiments have been carried out under different working conditions and the results have been compared with the predictions. A good agreement between the simulated and experimental results was found.