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61.
Characterization of coke on equilibrium, fluid catalytic cracking (FCC) catalysts contaminated with metals was investigated
using temperature-programmed oxidation (TPO). TPO spectra of spent equilibrium catalysts from cracking of sour imported heavy
gas oil (SIHGO) were deconvoluted into four peaks (Peak K, L, M and N). The four peaks were assigned to different types of
coke on the catalyst. Peak L in the TPO spectrum was assigned to the 'contaminant' coke in the vicinity of metals. The amount
of contaminant coke (Peak L) correlates with metal-contaminant concentration. The size of Peak L which is related to amount
of contaminant coke decreased significantly for the spent highly contaminated catalyst pretreated with hydrogen and methane
prior to cracking reactions as compared to the non-pretreated catalysts. Since both hydrogen and methane pretreatment can
reduce oxidation state of the vanadium that present at high concentrations on the equilibrium catalysts the decrease in the
amount of contaminant-coke represented by Peak L was explained by the reduction of the oxidation state of vanadium. Less contaminant
coke was produced after the equilibrium catalysts were pretreated using hydrogen and methane gases since reduced vanadium
has lower dehydrogenation activity compared to oxidized vanadium.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
62.
D. Yalcin O. Ozcalik E. Altiok O. Bayraktar 《Journal of Thermal Analysis and Calorimetry》2008,94(3):767-771
Tartaric acid is mainly used in food, pharmaceuticals and cosmetics industries. In this study, the waste samples, which contain
tartaric acid, from the wastes of wine and grape juice industries were characterized by using TG, DSC, FTIR and XRD techniques.
HPLC was used to determine tartaric acid content of samples. The decomposition temperatures of waste samples were found to
be relatively higher compared with that of pure tartaric acid. This difference in decomposition temperatures was attributed
to the presence of potassium tartrate since high potassium content was detected with ICP-AES. 相似文献
63.
64.
Hydrophobic coatings from photochemically prepared hydrophilic polymethacrylates via electrospraying 下载免费PDF全文
Tuğba Isık Mustafa M. Demir Cansu Aydogan Mustafa Ciftci Yusuf Yagci 《Journal of polymer science. Part A, Polymer chemistry》2017,55(8):1338-1344
Linear poly(hydroxyethyl methacrylate‐co‐methyl methacrylate) P(HEMA‐co‐MMA) and poly(dimehylaminoethyl methacrylate‐co‐methyl methacrylate) P(DMAEMA‐co‐MMA) and their corresponding hyperbranched copolymers were synthesized by conventional photoinitiated free radical polymerization and self‐condensing vinyl polymerization (SCVP) using Type I and Type II photoinitiators, respectively. Then, the polymers were processed by electrospraying in N, N‐dimethylformamide. The surface of the resulting electrospray coatings was examined by SEM, XPS, and WCA then compared with those prepared by drop casting. Regardless of the structural nature of the polymers, electrospraying allows the preparation of rough surface that shows more hydrophobic behavior. Electrospray coatings with linear and hyperbranched copolymers exhibited WCA as ~150° and ~130°, respectively, indicating that branching reduces the WCA. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 1338–1344 相似文献
65.
Bahman Angoshtari Erhan Bayraktar 《Stochastics An International Journal of Probability and Stochastic Processes》2016,88(6):946-958
We determine the optimal investment strategy in a Black–Scholes financial market to minimize the so-called probability of drawdown, namely, the probability that the value of an investment portfolio reaches some fixed proportion of its maximum value to date. We assume that the portfolio is subject to a payout that is a deterministic function of its value, as might be the case for an endowment fund paying at a specified rate, for example, at a constant rate or at a rate that is proportional to the fund’s value. 相似文献
66.
Fatma Cansu Yücel Fabian Habicht Myles D. Bohon Christian Oliver Paschereit 《Proceedings of the Combustion Institute》2021,38(3):3815-3823
The reliable generation of quasi-homogeneous autoignition inside a combustor fed by a continuous air flow would represent a milestone in realizing pressure gain combustion in gas turbines. In this work, the ignition distribution inside a stratified fuel–air mixture is analyzed. The ability of precise and reproducible injection of a desired fuel profile inside a convecting air flow is verified by applying tunable diode laser absorption spectroscopy in non-reacting measurements. High-speed, static pressure sensors and ionization probes allow for simultaneous detection of the flame and pressure rise at several axial positions in reactive measurements with dimethyl ether as fuel. A second, exchangeable combustion tube enables optical observation of OH* intensity in combination with pressure measurements. Experiments with three arbitrary fuel profiles show a set of ignition distributions that vary in shape, homogeneity, and the number of simultaneous autoignition events. Although the measurements show notable variation, a significant and reproducible influence of the fuel injection on the ignition distribution is observed. Results show that uniform autoignition leads to a coupling of the reaction front with the pressure rise and, therefore, induces a greater aerodynamic constraint than non-uniform ignition distributions, which are dominated by propagating deflagration fronts. 相似文献
67.
Type II photoinitiated self‐condensing vinyl polymerization for the preparation of hyperbranched polymers is explored using 2‐hydroxyethyl methacrylate (HEMA) or 2‐(dimethylamino)ethyl methacrylate (DMAEMA), and methyl methacrylate as hydrogen donating inimers and comonomer, respectively, in the presence of benzophenone and camphorquinone under UV and visible light. Upon irradiation at the corresponding wavelength, the excited photoinitiator abstracts hydrogen from HEMA or DMAEMA leading to the formation of initiating radicals. Depending on the concentration of inimers, type of the photoinitiator, and irradiation time, hyperbranched polymers with different branching densities and cross‐linked polymers are formed.
68.
Two new acylhydrazone copper(II) complexes of 4‐hydroxy‐N′‐[(1E)‐1‐(4‐methylphenyl)ethylidene]benzohydrazide (HL1) and 4 ethyl [4‐({(2E)‐2‐[1‐(4‐methylphenyl)ethylidene]hydrazinyl}carbonyl)phenoxy]acetate (HL2) have been synthesized and characterized. The structures of both acylhydrazone and copper(II) complexes were identified by elemental analysis, infrared spectra, UV–visible electronic absorption spectra, magnetic susceptibility measurements, TGA and powder X‐ray diffraction. DNA binding and DNA cleavage activities of the synthesized copper complexes were examined by using UV‐visible titration and agarose gel electrophoresis, respectively. The effect of complex concentration on the DNA cleavage reactions in the absence and presence of H2O2 was also investigated. The results indicate that all the complexes bind slightly to calf thymus DNA and cleavage pBR322 DNA. The mechanistic studies demonstrate that a hydrogen peroxide‐derived species and singlet oxygen (1O2) are the active oxidative species for DNA cleavage. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
69.
In this paper, we accomplish two objectives: First, we provide a new mathematical characterization of the value function for impulse control problems with implementation delay and present a direct solution method that differs from its counterparts that use quasi-variational inequalities. Our method is direct, in the sense that we do not have to guess the form of the solution and we do not have to prove that the conjectured solution satisfies conditions of a verification lemma. Second, by employing this direct solution method, we solve two examples that involve decision delays: an exchange rate intervention problem and a problem of labor force optimization. 相似文献
70.
We extend the work of Milevsky et al., [Milevsky, M.A., Promislow, S.D., Young, V.R., 2005. Financial valuation of mortality risk via the instantaneous Sharpe ratio (preprint)] and Young, [Young, V.R., 2006. Pricing life insurance under stochastic mortality via the instantaneous Sharpe ratio (preprint)] by pricing life insurance and pure endowments together. We assume that the company issuing the life insurance and pure endowment contracts requires compensation for their mortality risk in the form of a pre-specified instantaneous Sharpe ratio. We show that the price Pm,n for m life insurances and n pure endowments is less than the sum of the price Pm,0 for m life insurances and the price P0,n for n pure endowments. Thereby, pure endowment contracts serve as a hedge against the (stochastic) mortality risk inherent in life insurance, and vice versa. 相似文献