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The focus of this paper is on understanding the exchange between dissolved fats and fat crystals in dispersions by quantifying the rate of the exchange between the fats in solution and in crystals. In the studies reported here, tripalmitin (PPP) was used as model fat. The dispersions contained PPP crystals and dissolved radio-labelled PPP (14C-PPP, used as the probe) in a medium chain triglyceride oil (MCT). The exchange process between the dissolved 14C-PPP and unlabelled PPP crystals was followed using a radio-detector. The effect of the crystal concentration on the exchange rate was studied. The results suggested that the rate of the exchange is dependent upon both the dissolution of the surface of the crystals and also diffusion and crystallisation of the dissolved compounds. 相似文献
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In this paper,an axial dispersion mathematical model is developed to simulate a three-phase slurry bubble column reactor for direct synthesis of dimethyl ether(DME) from syngas.This large-scale reactor is modeled using mass and energy balances,catalyst sedimentation andsingle-bubble as well as two-bubbles class flow hydrodynamics.A comparison between the two hydrodynamic models through pilot plantexperimental data from the literature shows that heterogeneous two-bubbles flow model is in better agreement with the experimental data thanhomogeneous single-bubble gas flow model.Also,by investigating the heterogeneous gas flow and axial dispersion model for small bubblesas well as the large bubbles and slurry(i.e.including paraffins and the catalyst) phase,the temperature profile along the reactor is obtained.Acomparison between isothermal and non-isothermal reactors reveals no obvious performance difference between them.The optimum values ofreactor diameter and height were obtained at 7 m and 50 m,respectively.The effects of operating variables on the axial catalyst distribution,DME productivity and CO conversion are also investigated in this research. 相似文献
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Mehdi Adib Ehsan Sheikhi Pouyan Haghshenas Saideh Rajai-Daryasarei Hamid Reza Bijanzadeh Long-Guan Zhu 《Tetrahedron letters》2014
A novel one-pot, five-component synthesis of 1-(alkylimino)-5,5-dicyano-3a-aryloctahydro-3-oxacyclobuta[cd]pentalene-1a,2,5a,5b(2H,3aH)-tetracarboxylates is described. A mixture of phenacyl bromide, malononitrile, isocyanide, and two equivalents of a dialkyl acetylenedicarboxylate undergoes a novel 1:1:1:2 addition reaction at ambient temperature in absolute ethanol to produce diastereoselectively the title compounds in good yields. 相似文献
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Nonlinear Dynamics - Different architectures and techniques have developed in the neuromorphic field to mimic and investigate the activity of biological neural networks. This paper presents a set... 相似文献
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Meccanica - The issue of gear noise is fairly common in power transmission systems. This noise largely stems from the gear pairs vibration triggered by transmission error excitation. This is mainly... 相似文献
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Ion-acoustic solitary waves in a dense pair-ion plasma containing degenerate electrons and positrons
Fully nonlinear propagation of ion-acoustic solitary waves in a collisionless dense/quantum electron–positron–ion plasma is investigated. The electrons and positrons are assumed to follow the Thomas–Fermi density distribution and the ions are described by the hydrodynamic equations. An energy balance-like equation involving a Sagdeev-type pseudo-potential is derived. Finite amplitude solutions are obtained numerically and their characteristics are discussed. The small-but finite-amplitude limit is also considered and an exact analytical solution is obtained. The present studies might be helpful to understand the excitation of nonlinear ion-acoustic solitary waves in a degenerate plasma such as in superdense white dwarfs. 相似文献
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S. K. El-Labany W. M. Moslem Kh. A. Shnishin S. A. El-Tantawy 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2011,61(2):409-420
By using the hydrodynamic equations of positive and two negative ions,
Boltzmann electron density distribution, and Poisson equation with immobile
positive/negative dust particles, a cylindrical Korteweg-de Vries (CKdV)
equation is derived for small but finite amplitude ion-acoustic waves. At the
critical total negative ion concentration and/or the critical density rate of
the second-negative ions, the pulses collapse at this limit as nonlinearity
fails to balance dispersion. Then the CKdV equation is not appropriate to
describe the system. Therefore, the modified CKdV (MCKdV) and extended CKdV
(ECKdV) equations are derived at the critical plasma compositions and in the
vicinity of the critical plasma compositions, respectively. The physical
parameters of two plasma environments (e.g., Xe+–F-–SF6-_{6}^{-} and
Ar+–F-–SF6-_{6}^{-} plasmas) are examined on the wave phase velocity and
the nonlinear localized pulse profile. The latter should satisfy necessary
condition to exist. The localized pulse of Ar+–F-–SF6-_{6}^{-} plasma is
much spiky than Xe+–F-–SF6-_{6}^{-} plasma. Thus, the mass ratio of the
negative-to-positive ions is focused upon and it emphasizes to play an
important role on the pulse profile. Dependence of the geometrical divergence
on the pulse profile is also investigated, which indicates that the localized
pulse damps with time. The implications of our results agrees with the
experimental observations. 相似文献
10.
Elnaz Iranmanesh Moslem Jahani Azizollah Nezhadali Maliheh Mojarrab 《Journal of separation science》2020,43(6):1164-1172
This paper describes the synthesis of a molecularly imprinted polymer by chemical oxidation of pyrrole as the functional monomer, and at the presence of guaifenesin as the template. The prepared polymer was used as adsorbent in molecularly imprinted solid‐phase extraction followed by spectrophotometric determination. Different parameters in the solid‐phase extraction including sample pH, adsorbent weight, washing solution, and elution solvent were studied to determine optimum conditions for isolation and enrichment of guaifenesin. The results showed guaifenesin was quantitatively adsorbed on the molecularly imprinted polymer at pH 6.0 and completely eluted with an ethanol–water solution (50% v/v). An enrichment factor of four with satisfactory recoveries (87.0–95.0%) was obtained. The solid‐phase extraction columns could be used for up to six consecutive elution‐loading cycles without significant decreases in the analyte recoveries. The method had a dynamic range of 3.0 × 10?6–1.5 × 10?4 mol/L with a limit of detection and limit of quantification of 1.4×10?6 and 4.5×10?6 mol/L, respectively. The proposed procedure was used for the extraction and determination of guaifenesin in different pharmaceutical formulations, with satisfying results being achieved. 相似文献