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排序方式: 共有942条查询结果,搜索用时 15 毫秒
931.
Parsa Zamankhan Goodarz Ahmadi Zuocheng Wang Philip K. Hopke Yung-Sung Cheng Wei Chung Su 《Aerosol science and technology》2013,47(6):463-476
A 3D computational model was developed to study the flow and the transport and deposition of nano-size particle in a realistic human nasal passage. The nasal cavity was constructed from a series of MRI images of coronal sections of a nose of a live human subject. For several breathing rates associated with low or moderate activities, the steady state flows in the nasal passage were simulated numerically. The airflow simulation results were compared with the available experimental data for the nasal passage. Despite the anatomical differences of the human subjects used in the experiments and computer model, the simulation results were in qualitative agreement with the experimental data. Deposition and transport of ultrafine particles (1 to 100 nm) in the nasal cavity for different breathing rates were also simulated using an Eulerian-Lagrangian approach. The simulation results for the nasal capture efficiency were found to be in reasonable agreement with the available experimental data for a number of human subjects given typical anatomical differences. The computational results for the nasal capture efficiency for nano-particles and various breathing rates in the laminar regime were found to correlate well with the ratio of particle diffusivity to the breathing rate especially for the particles smaller than 20 nm. Based on the simulated results, a semi-empirical equation for the capture efficiency of the nasal passage for nano-size particles was fitted in terms of Peclet number. 相似文献
932.
Heavy oil and bitumen play an incredible role in Canada's energy resources. The main processes that have already been applied to produce heavy oil and bitumen are in-situ thermal methods. The primary mechanism of production in these reservoirs is a reduction in heavy oil and bitumen viscosities via heat transfer. Having deep knowledge about the rheological behaviour of heavy oil and bitumen is crucial to designing a more accurate and efficient in-situ thermal recovery method. In this work, molecular dynamics (MD) simulation was used to model the rheological behaviour of bitumen under different temperatures. According to MD outputs, the highest diffusion coefficient between bitumen fractions belongs to saturate fractions. On the other hand, the lowest diffusion coefficient belongs to asphaltene fractions. The size of asphaltene, its polarity, and the polarity of a resin fraction affect the diffusion coefficient of asphaltene in a bitumen sample and its rheological behaviour. The MD simulation aims to provide molecular insights and essential information about the rheological trend of bitumen under different thermodynamic conditions. The results of the current work provide essential information about the effect of bitumen fractions on its rheological behaviour. 相似文献
933.
Aliakbar Ahmadi Mojgan Ayoubi-Chianeh Mohamad Z. Kassaee Farhad Bayat 《加拿大化工杂志》2023,101(7):4200-4216
The aim of this research is a comparison of the efficiency of six commercially available cyclodextrins (CDs) to improve the solubility and oral bioavailability of atorvastatin calcium (ATV-Ca) and rosuvastatin calcium (ROV-Ca) drugs in aqueous media. Inclusion complexes of both drugs with non-toxic α-CD, β-CD, γ-CD, HP-β-CD, M-β-CD, and maltodextrin were prepared in a 1:1 stoichiometry via the kneading method. To reach the best CD, various experimental and computational analyses were performed including phase solubility, dynamic light scattering (DLS), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), atomic force microscopy (AFM), hydrogen-1 nuclear magnetic resonance (1HNMR), carbon-13 nuclear magnetic resonance (13CNMR), and molecular docking calculations. The M-β-CD turned out to be the best substrate for the micro-encapsulation of both drugs. Also, ATV showed a higher tendency than ROV to form inclusion complexes with CDs. Molecular docking studies showed that HP–β–CD and M-β-CD are the most suitable substrates for the formation of inclusion complexes, respectively. Our research showed that the β-CD is not necessarily the most efficient substrate for increasing solubility based on previous reports in the literature; meanwhile, the other employed substrates in this study can show acceptable performances in this regard. According to our results, M-β-CD is the best substrate for the micro-encapsulation of both drugs, which increases their solubility in water. 相似文献
934.
Reza Ahmadi Afshin Masoudi Hamid Reza Madaah Hosseini Ning Gu 《Ceramics International》2013,39(5):4999-5005
In the present study, a one step hydrothermal process was employed to synthesize magnetite nanoparticles using oleic acid as surfactant agent at 140 °C. Effects of reaction time and alkalinity were studied on particles size and morphology. By changing these parameters, some monodisperse spherical nanoparticles with mean particle size between 2.71 and 13.88 nm were synthesized and characterized via TEM, XRD, VSM, TGA and FT-IR techniques. Assuming the Avrami behavior of particles formation, a kinetics equation was proposed for the transformation rate at 140 °C. Using some simplifying assumptions, nucleation and growth rates were calculated for the hydrothermal formation of magnetite nanoparticles at 140 °C. 相似文献
935.
Mohammad Javad Kiani Mohammad Taghi Ahmadi Hediyeh Karimi Feiz Abadi Meisam Rahmani Amin Hashim Fauzan Khairi Che harun 《Nanoscale research letters》2013,8(1):173
Graphene has attracted great interest because of unique properties such as high sensitivity, high mobility, and biocompatibility. It is also known as a superior candidate for pH sensing. Graphene-based ion-sensitive field-effect transistor (ISFET) is currently getting much attention as a novel material with organic nature and ionic liquid gate that is intrinsically sensitive to pH changes. pH is an important factor in enzyme stabilities which can affect the enzymatic reaction and broaden the number of enzyme applications. More accurate and consistent results of enzymes must be optimized to realize their full potential as catalysts accordingly. In this paper, a monolayer graphene-based ISFET pH sensor is studied by simulating its electrical measurement of buffer solutions for different pH values. Electrical detection model of each pH value is suggested by conductance modelling of monolayer graphene. Hydrogen ion (H+) concentration as a function of carrier concentration is proposed, and the control parameter (Ƥ) is defined based on the electro-active ions absorbed by the surface of the graphene with different pH values. Finally, the proposed new analytical model is compared with experimental data and shows good overall agreement. 相似文献
936.
Alireza Bahramian Martin Olazar Goodarz Ahmadi 《American Institute of Chemical Engineers》2013,59(12):4502-4518
The hydrodynamic performance of micrometric TiO2 particles has been experimentally studied in a conical fluidized bed and the results compared with numerical simulations. Local solid velocities in the bed have been measured by means of an optical fiber technique under different operating conditions of particle loading and air velocity. The radial profiles of axial solid velocities have been simulated to assess the sensitivity of grid size, and different drag models, namely, those by Syamlal and O'Brien, Ahmadi and Ma, Arastoopour et al., and Gidaspow, for no‐slip, partial‐slip, and free‐slip boundary conditions (BCs). The different drag models record almost similar results, but those provided by the Gidaspow and Ahmadi–Ma models, together with free‐slip BCs, are in somewhat better agreement with the experimental data for conical fluidized beds with smooth walls. © 2013 American Institute of Chemical Engineers AIChE J, 59: 4502–4518, 2013 相似文献
937.
Summary Intermacromolecular complexes of poly (acrylic acid) (PAA) with poly (ethylene oxide) (PEO), poly (ethylene imine) (PEI) and
poly (vinyl pyrrolidon) (PVP) were prepared. The stability constants and thermodynamic parameters (e.g. ΔH0 and ΔS0) of these complexes were determined at several temperatures. The enthalpy and entropy changes of the systems with temperature
have been interpreted in terms of various mode of interaction between the components and compared with each other. 相似文献
938.
Ali Ahmadi Orkomi 《Chemical Engineering Communications》2013,200(7):870-895
In this article, solving the population balance equation (PBE) and controlling the final particle size for crystallization problems have been addressed. For solving the general form of multidimensional PBE, a numerical method called conservation element and solution element (CE/SE) has been used. By applying this method to one- and two-dimensional crystallization problems, it has been shown that this technique can handle all types of source terms in the PBE. Model accuracy has been checked with experimental data reported in the literature and also with the analytical solution of PB-type equations. Control of final particle size was formulated in an optimization framework. To obtain a desired final size distribution for one-dimensional crystallization, the optimal temperature trajectory was achieved for size-dependent growth rate case with the agglomeration effect. For the two-dimensional case, the aspect ratio was controlled and the crystallization batch time minimized. To track the optimal temperature trajectories, PI controllers were used. Simulation results indicate that the desired final size distribution for the one-dimensional case and the aspect ratio for the two-dimensional case were approached very closely. 相似文献
939.
Poly [2,2′-(m-pyrazolidene)-5,5′-bibenzimidazole] (PPBI) was synthesized from pyrazole-3,5-dicarboxylic acid and 3,3′,4,4′-tetraaminobiphenyle (TAB) through polycondensation reaction in polyphosphoric acid (PPA) as reaction solvent. And polymer-grafted SiO2 and TiO2 nanoparticles were prepared through radical polymerization of 1-vinylimidazole and sulfonated vinylbenzene on the surface-vinylated nanoparticles. The polymer-grafted SiO2 and TiO2 nanoparticles were utilized as a functional additive to prepare PPBI/polymer-grafted SiO2 and TiO2 nanocomposite membranes. Imidazole and sulfonated vinylbenzene groups on the surface of modified nanoparticles forming linkages with PPBI chains, improved the compatibility between PPBI and nanoparticles, and enhanced the mechanical strength of the prepared nanocomposite membranes. The prepared nanocomposite membranes showed higher water uptake and acid doping levels comparing to PPBI. Also, after acid doping with phosphoric acid, nanocomposite membranes exhibited enhanced proton conductivity in comparison to the pristine PPBI and PPBI/un-modified SiO2 and TiO2 nanocomposite membranes. The enhancement in proton conductivity of nanocomposite membranes resulted from modified SiO2 nanoparticles showed higher conductivity than modified TiO2 nanoparticles. The above results indicated that the PPBI/modified SiO2 and TiO2 nanocomposite membranes could be utilized as proton exchange membranes for medium temperature fuel cells. 相似文献
940.
Various surfactants have been used in upstream petroleum processes like chemical flooding. Ultimately, the performance of these surfactants depends on their ability to reduce the interfacial tension between oil and water. The surfactant concentration in the aqueous solution decreases owing to the loss of the surfactant on the rock surface in the injection process. The main objective of this paper is to inhibit the surfactant loss by means of adding nanoparticles. Sodium dodecyl sulfate and silica nanoparticles were used as ionic surfactant and nanoparticles in our experiments, respectively. AEROSIL~? 816 and AEROSIL~?200 are hydrophobic and hydrophilic nanoparticles. To determine the adsorption loss of the surfactant onto rock samples, a conductivity approach was used. Real carbonate rock samples were used as the solid phase in adsorption experiments. It should be noted that the rock samples were water wet. This paper describes how equilibrium adsorption was investigated by examining adsorption behavior in a system of carbonate sample(solid phase) and surfactant solution(aqueous phase). The initial surfactant and nanoparticle concentrations were 500–5000 and 500–2000 ppm, respectively. The rate of surfactant losses was extremely dependent on the concentration of the surfactant in the system, and the adsorption of the surfactant decreased with an increase in the nanoparticle concentration. Also, the hydrophilic nanoparticles are more effective than the hydrophobic nanoparticles. 相似文献