Growth mechanism of NaClO3 and NaBrO3 crystals from aqueous solutions

A study of growth rates of NaClO₃ and NaBrO₃ has been carried out using a small growth cell by in situ observation. Normal growth rates of (100) faces of NaClO₃ and (111) faces of NaBrO₃ along 〈110〉 direction are measured under relatively high supersaturation ranging from 3–8%. In the initial stages of growth, (100), (110) and (111) faces develop in NaClO₃ and gradually all the faces are replaced by the (100) faces only. In the case of NaBrO₃, mostly (111) faces develop with occasional occurrence of small (100) faces at the intersection of (111) faces. The growth mechanisms are investigated from growth rate vs supersaturation plots and from the observations of surface features. In the present supersaturation range, the growth mechanism appears to be due to two-dimensional growth mechanism.     

Three-Dimensional Numerical Modeling of Heat and Moisture Transfer in Natural Rubber Sheet Drying Process

The effects of heat and moisture transfer on rubber sheet drying were investigated by 3-D modeling using computational fluid dynamics (CFD). Complexities arose due to the inclusion of moisture transport. Local convective heat transfer coefficients for the sheets were predicted and then used to determine the mass transfer coefficients using the Chilton–Colburn analogy. Deviations between experimental and simulated temperatures were observed to range from 4.0 to 7.7°C. Temperature and moisture content of the rubber sheets were accurately predicted, and agreement between the experimental and simulated results was acceptable. This is useful for the design of an efficient rubber sheet drying chamber.     

Monodispersed and Stable Nano Copper(0) from Copper‐ Aluminium Hydrotalcite: Importance in C?C Couplings of Deactivated Aryl Chlorides

A simple one‐step approach for the preparation of highly monodispersed nano copper(0) stabilized on alumina [Cu(0)/Al₂O₃] by thermal reduction of copper‐aluminium hydrotalcite (Cu‐Al HT) under a hydrogen atmosphere is described. The transformation of Cu‐Al HT to Cu(0)/Al₂O₃ occurrs via dehydroxylation of divalent and trivalent metal hydroxides and decarboxylation of carbonate anions present in the interlayers of hydrotalcite, as confirmed by XPS, XANES, XRD and TEM analysis. Cu(0)/Al₂O₃ nano composites were used as an efficient catalyst in the C C coupling of deactivated aryl chlorides. The high efficiency and reusability exhibited by Cu(0)/Al₂O₃ outline its potential as an alternative over traditional noble metal‐based catalysts in C C coupling reactions.     

Effect of horizontal pressure gradient on Rayleigh–Bénard convection of a Newtonian nanoliquid in a high porosity medium using a local thermal non-equilibrium model

A study of linear and weakly nonlinear stability analyses of Darcy–Brinkman convection in a water–alumina, nanoliquid-saturated porous layer for stress-free isothermal boundaries, when the solid and nanoliquid phases are in local thermal nonequilibrium, is conducted. The critical eigenvalue is found using the Galerkin approach. The effect of the pressure gradient, thermal conductivity ratio, interphase heat transfer coefficient, inverse Darcy number, and Brinkman number on the heat transport and onset of convection is examined and represented graphically. The critical values of wavenumber and nanoliquid Rayleigh number are found for different problem parameter values. The effect of increasing the porosity-modified ratio of thermal conductivity advances the onset of convection and increases the amount of heat transport, whereas the remaining parameters have the opposite impact on the onset of convection and amount of heat transport. The classical results of the local thermal equilibrium case and Darcy–Bénard convection in the presence of pressure gradient are obtained as a limiting case of the present problem.     

Optimization model for handoff-aware channel assignment problem for multi-radio wireless mesh networks

Optimal channel assignment (CA) in multi-radio wireless mesh networks is an NP-hard problem for which solutions usually leave several links interfering. Most of these solutions usually consider the overall throughput as the main optimization objective. However, other objectives have to be considered in order to provide better quality wireless connections to non stationary users. In this paper, we propose a multi-objective optimization model that, besides maximizing throughput, improves fairness and handoff experience of mesh clients. In this model, we use the Jain’s index to maximize users’ fairness and we allow same-channel assignments to links involved in the same high handoff traffic, thus reducing handoff-triggered re-routing characterized by its high latency. Then, we propose a centralized variable neighborhood search and a Tabu search heuristics to efficiently solve our model as an offline CA process. Moreover, in order to adapt to traffic dynamics caused especially by user handoffs, we propose an online CA scheme that carefully re-assigns channels to interfaces with the purpose of continuously minimizing the re-routing overhead/latency during user handoffs. We further improve this online scheme using load balancing. Simulation results show the good performance of our proposed approach in terms of delay, loss rate, overall throughput and fairness. Particularly, performance results of our online handoff-aware CA show the effectiveness of handoffs not involving path re-routing in decreasing the delay, especially when considering load balancing.     

Nanocrystalline Magnesium Oxide Stabilized Palladium(0): An Efficient Reusable Catalyst for Room Temperature Selective Aerobic Oxidation of Alcohols

Nanocrystalline magnesium oxide‐stabilized palladium(0) [NAP‐Mg‐Pd(0)], as an efficient catalytic system has been employed for the selective oxidation of alcohols using atmospheric oxygen as a green oxidant at room temperature. Various alcohols could be transformed into their corresponding aldehydes or ketones in good to excellent yields using a set of optimal conditions. NanoActive™ Magnesium Oxide Plus, [NAP‐MgO] with its three‐dimensional structure and well‐defined shape acts as an excellent support for well dispersed palladium(0) nanoparticles. This catalyst can be recovered and reused for several cycles without any significant loss of catalytic activity.     

Copper Nanoparticles from Copper Aluminum Hydrotalcite: An Efficient Catalyst for Acceptor‐ and Oxidant‐Free Dehydrogenation of Amines and Alcohols

An efficient and simple process for the preparation of stable nanocopper(0) on alumina [Cu(0)/Al₂O₃] from the inorganic composite precursor copper aluminum hydrotalcite (Cu‐Al HT) by a chemical reduction method is described. Cu(0)/Al₂O₃ was employed as an efficient catalyst in the acceptor‐ and oxidant‐free dehydrogenation of various amines and alcohols to their corresponding dehydrogenated products in good to excellent yields. The stability of Cu(0)/Al₂O₃ was assessed by studying its recoverability and reusability in the dehydrogenation of amines and alcohols for up to five cycles.

     

Highly efficient heterogenous catalyst for O-arylation of phenols with aryl halides using natural ferrous chamosite

Natural ferrous chamosite-catalyzed arylation of phenols with aryl iodides and bromides afforded the corresponding ethers in moderate to excellent yields. This ligand-free, natural catalyst catalyzed coupling of aryl iodides and aryl bromides with phenols resulted in high yields of diaryl ether formation in the absence of any additive. The catalyst was quantitatively recovered from the reaction by a simple filtration and reused for a number of cycles.     

Reusable Copper‐Aluminum Hydrotalcite/rac‐BINOL System for Room Temperature Selective Aerobic Oxidation of Alcohols

An efficient catalyst system consisting of copper‐aluminum hydrotalcite/rac‐BINOL ligand has been developed for the oxidation of alcohols using air as a green oxidant at room temperature. Various alcohols could be transformed into their corresponding aldehydes or ketones in good to excellent yields using the set of optimal conditions. This composite catalytic system can also be recovered and reused for several cycles without a significant loss of catalytic activity.     

A novel method for assessing the chromatic integration of architecture in the Ksourian landscape of M'zab Valley,Algeria

Ksour are original architectural models of fortified villages located in the north of Africa. They offer, through their urban and natural visual sceneries, specific visible features that we name them Ksourian Landscapes. The present research, accordingly, addresses an investigation; relying on a new methodic perspective, of the chromatic character of the Ksourian landscape of M'zab valley in Algeria which is listed as an UNESCO World Heritage Site. Using the Natural Color System (NCS), a natural palette (NP) has been conducted; encapsulating 12 representative colors from the natural landscape of the site in congruence with a second palette (human settlements palette), which includes around 16 colors from the urban landscape of the Mozabite Ksour. The primary purpose of this research article aims at identifying perceptual similarities between the two palettes after comparison; which relies upon the NCS nominal identities (blackness [s], whiteness [w], chromaticness [c], yellowness [y], and redness [r]); and the NCS relation identities (hue [φ], saturation [m], delta [δ], and beta [β]). Graphical representations of these comparisons are demonstrated in the NCS triangle and the NCS 3D color space. We have demonstrated through our experimental outcomes the strong chromatic integration of the urban settlements in their natural landscape, the original chromatic character as being a constituent of the heritage values of the Mozabite Ksourian landscape, as well as its possible use in the urban restoration processes.