CFD study of non-premixed swirling burners: Effect of turbulence models

This research investigates a numerical simulation of swirling turbulent non-premixed combustion. The effects on the combustion characteristics are examined with three turbulence models: namely as the Reynolds stress model, spectral turbulence analysis and Re-Normalization Group. In addition, the P-1 and discrete ordinate (DO) models are used to simulate the radiative heat transfer in this model. The governing equations associated with the required boundary conditions are solved using the numerical model. The accuracy of this model is validated with the published experimental data and the comparison elucidates that there is a reasonable agreement between the obtained values from this model and the corresponding experimental quantities. Among different models proposed in this research, the Reynolds stress model with the Probability Density Function (PDF) approach is more accurate (nearly up to 50%) than other turbulent models for a swirling flow field. Regarding the effect of radiative heat transfer model, it is observed that the discrete ordinate model is more precise than the P-1 model in anticipating the experimental behavior. This model is able to simulate the subcritical nature of the isothermal flow as well as the size and shape of the internal recirculation induced by the swirl due to combustion.     

Surface modification of multiwalled carbon nanotubes via surface RAFT copolymerization method and capecitabine-loaded anticancer hydrogel for controlled drug delivery in stomach

ABSTRACT

In our work, reversible addition-fragmentation chain transfer (RAFT)/carbon nanotube (CNT)/acrylic acid (AA)/acrylamide (AAm) nanocomposite was synthesized by living radical polymerization. The structure and surface morphology of the synthesized RAFT-CNT-Hydrogel nanocomposites were analyzed by FTIR, ¹HNMR, SEM, TEM, XRD, and TGA/DTG techniques. The results indicated that PAA/AAm chains grafted with CNT by RAFT polymerization. RAFT-CNT-Hydrogel nanocomposites for drug release investigated in different buffers resulted in a strong pH-sensitive behavior. In total, the obtained hydrogel drug-delivery systems are presented a proper effect versus stomach cancer in vitro and in vivo, and it can be used as candidates for controlled release of anticancer drugs in stomach with exalted remedial agents.     

Kinetics and Mechanism of Low-Grade Manganese Ore Reduction by Natural Gas

Metallurgical and Materials Transactions B - The calcination and the reduction behaviors of a low-grade manganese ore by methane was studied at 973 K to 1273 K by several techniques. The onset...     

Evaluation of mustard (Brassica juncea) protein isolate prepared by steam injection heating for reduction of antinutritional factors

A process for the preparation of mustard protein isolate, comprising steps such as dispersion of defatted meal in 0.1 mol/l NaCl solution, incubation, extraction at alkaline pH, followed by treatment of the protein solution with activated carbon was developed. The protein, coagulated by steam injection, was subjected to separation by centrifugation, washing and spray drying. The parameters evaluated were protein yield, purity, presence of antinutritional factors and nutritional quality of proteins. The protein yield was 58-60%. The purity of the protein isolate was 95%. The hydrolysed products of glocosinolates like isothiocyanates and oxazolidine thione levels, phenolics and phytic acid levels were low in the protein isolate. The in vitro digestibility of the protein isolate was 92.4% compared to 80.6% of the meal. Chemical score of the meal and protein isolate were similar; isoleucine was the first limiting amino acid. The calculated nutritional indices, essential amino acid index, biological value, nutritional index and C-PER of protein isolate were higher compared to meal. The protein quality as indicated by amino acid profile and PDCAAS scores for 10-12-years old and adults were 100.     

Unconfined compressive strength prediction of soils stabilized using artificial neural networks and support vector machines

This study aims to improve the unconfined compressive strength of soils using additives as well as by predicting the strength behavior of stabilized soils using two artificial-intelligence-based models. The soils used in this study are stabilized using various combinations of cement, lime, and rice husk ash. To predict the results of unconfined compressive strength tests conducted on soils, a comprehensive laboratory dataset comprising 137 soil specimens treated with different combinations of cement, lime, and rice husk ash is used. Two artificial-intelligence-based models including artificial neural networks and support vector machines are used comparatively to predict the strength characteristics of soils treated with cement, lime, and rice husk ash under different conditions. The suggested models predicted the unconfined compressive strength of soils accurately and can be introduced as reliable predictive models in geotechnical engineering. This study demonstrates the better performance of support vector machines in predicting the strength of the investigated soils compared with artificial neural networks. The type of kernel function used in support vector machine models contributed positively to the performance of the proposed models. Moreover, based on sensitivity analysis results, it is discovered that cement and lime contents impose more prominent effects on the unconfined compressive strength values of the investigated soils compared with the other parameters.     

Polypropylene cellulose‐based composites: The effect of bagasse reinforcement and polybutadiene isocyanate treatment on the mechanical properties

Using bagasse fiber as the reinforcing filler and polypropylene as the thermoplastic matrix polymer, a reinforced composite was prepared, and its mechanical properties examined as a function of the amount of compatibilizing agents used. In the sample preparation, four levels of fiber loading (10, 20, 30, and 40 wt %), three levels of polybutadiene isocyanate (PBNCO) content (0, 2, and 4 wt %) and two levels of maleated polypropylenes (MAPP) content (0 and 3 wt %) as compatibilizing agents were used. The tensile properties of the composites improved as the fiber loading and the compatibilizing agents increased, but the impact strength was significantly decreased. The mechanical study revealed that the positive effect of compatibilizing agents on interfacial bonding. The composites treated with PBNCO showed superior tensile and impact properties than those without treatment. The findings indicated that bagasse as agro‐waste material is a valuable renewable natural resource for composite production and could be utilized as a substitute for wood in composite industries. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Solving the stochastic support vector regression with probabilistic constraints by a high-performance neural network model

This paper offers a recurrent neural network to support vector machine (SVM) learning in stochastic support vector regression with probabilistic constraints. The SVM is first converted into an equivalent quadratic programming (QP) formulation in linear and nonlinear cases. An artificial neural network for SVM learning is then proposed. The presented neural network framework guarantees obtaining the optimal solution of the SVM problem. The existence and convergence of the trajectories of the network are studied. The Lyapunov stability for the considered neural network is also shown. The efficiency of the proposed method is shown by three illustrative examples.

     

Dual-Function Semaphorin 4D Released by Platelets: Suppression of Osteoblastogenesis and Promotion of Osteoclastogenesis

Effects of the antiosteoblastogenesis factor Semaphorin 4D (Sema4D), expressed by thrombin-activated platelets (TPs), on osteoblastogenesis, as well as osteoclastogenesis, were investigated in vitro. Intact platelets released both Sema4D and IGF-1. However, in response to stimulation with thrombin, platelets upregulated the release of Sema4D, but not IGF-1. Anti-Sema4D-neutralizing monoclonal antibody (mAb) upregulated TP-mediated osteoblastogenesis in MC3T3-E1 osteoblast precursors. MC3T3-E1 cells exposed to TPs induced phosphorylation of Akt and ERK further upregulated by the addition of anti-sema4D-mAb, suggesting the suppressive effects of TP-expressing Sema4D on osteoblastogenesis. On the other hand, TPs promoted RANKL-mediated osteoclastogenesis in the primary culture of bone-marrow-derived mononuclear cells (BMMCs). Among the known three receptors of Sema4D, including Plexin B1, Plexin B2 and CD72, little Plexin B2 was detected, and no Plexin B1 was detected, but a high level of CD72 mRNA was detected in RANKL-stimulated BMMCs by qPCR. Both anti-Sema4D-mAb and anti-CD72-mAb suppressed RANKL-induced osteoclast formation and bone resorptive activity, suggesting that Sema4D released by TPs promotes osteoclastogenesis via ligation to a CD72 receptor. This study demonstrated that Sema4D released by TPs suppresses osteogenic activity and promotes osteoclastogenesis, suggesting the novel property of platelets in bone-remodeling processes.     

Microstructural and mechanical assessment of transient liquid phase bonded commercially pure titanium

Diffusion joining of commercially pure titanium was successfully prepared via transient liquid phase bonding in vacuum environment. The process was carried out using AMS 4772 silver-based filler alloy at 900–1000°C for various holding time under the vacuum of 6?×?10^?7?Torr. Optical and scanning electron microscopy equipped with an EDS analyzer was conducted for microstructural evaluations. Mechanical properties were also investigated by shear test, fractographic assessment and X-ray diffraction analyses. The tendency to achieve isothermally solidified joint increased by increasing bonding time. No sign of athermal solidification was detected of sample bonded at 1000°C for 90?min. Consequently, the bonding condition of a high quality joint was obtained. Elemental analyses revealed that filler alloy’s elements (Ag, Cu) distributed more uniformly in fully isothermal solidified bond, whereas the aggregation of these elements is considerable in athermally solidified bond. Shear test results represented that the highest shear strength attributed to the sample bonded in isothermal solidified condition (bonded at 1000°C for 90?min).