A new K2Ca2(SO4)3:Cu+ nanocrystalline TLD phosphor was prepared by chemical coprecipitation method using calcium chloride, potassium chloride and ammonium sulphate as reactants and copper chloride (Cu2Cl2, as impurity) in the presence of ethanol. The samples were characterized by X-ray diffraction (XRD), Transmission electron microscopy (TEM), Differential thermal and thermogravimetric analysis (DT-TGA) techniques. XRD and DTA data show that there is a phase transformation from orthorhombic to cubic occurring at around 550 K. The effects of impurity concentration, annealing temperature and γ rays dose on TL characteristics of the material have been studied. Different glow curves have been theoretically deconvoluted using computerized glow curve deconvolution (CGCD method) into simple glow peaks to determine their trapping parameters. The results show that different phases existing in the material on annealing might have reorganized the electron-traps (energy levels) and hole-traps (luminescence centers) and are responsible for changing glow curve structures. This is very important to know as any change in the glow curve structure would cause errors in estimation of doses of high-energy radiations and also may lose its reusability. The photoluminescence (PL) studies show that there are no redox reactions (Cu+ Cu2+) taking place and Cu remains in its Cu+ form after annealing and even after irradiation. 相似文献
An essential cycle on a surface is a simple cycle that cannot be continuously deformed to a point or a single boundary. We
describe algorithms to compute the shortest essential cycle in an orientable combinatorial surface in O(n2log n) time, or in O(nlog n) time when both the genus and number of boundaries are fixed. Our results correct an error in a paper of Erickson and Har-Peled
(Discrete Comput. Geom. 31(1):37–59, 2004). 相似文献
The joint-scalar probability density function (PDF) approach provides a comprehensive framework for large eddy simulation (LES) based combustion modeling. However, currently available stochastic approaches for solving the high-dimensional PDF transport equation can be error prone and numerically unstable in highly compressible shock-containing flows. In this work, a novel Eulerian approach called the direct quadrature method of moments (DQMOM) is developed for evolving the PDF-based supersonic combustion model. The DQMOM technique uses a set of scalar transport equations with specific source terms to recover the PDF. The new technique is coupled to a compressible LES solver through the energy equation. The DQMOM approach is then used to simulate two practical flow configurations: a supersonic reacting jet and a cavity-stabilized supersonic combustor. Comparisons with experimental data demonstrate the predictive accuracy of the method. 相似文献
In this, an efficient flame retardant composite has been prepared using biowaste derived phosphorous groups decorated graphene supported nanomaterial. The eggshell was utilized as a source of calcium carbonate, which was converted to monocalcium phosphate (CP) by phosphoric acid treatment. As-prepared monocalcium phosphate was functionalized with graphene to prepare graphene functionalized monocalcium phosphate (GCP). The GCP-coated fabric didn't ignite during the flame test and sustained more than 600 s on continuous exposure to flame without changing its initial length and shape. Whereas, graphene oxide (GO), and CP coated cotton fabric burnt out very easily within a short time. The efficient flame retardant property of as synthesized GCP coated cotton fabric was confirmed with a high limiting oxygen index (34.1) and char length of 2.5 cm was generated from the VFT test. The synthesized GCP coated cotton fabric also confirmed efficient flame retardant properties. This facile method enables an easy process for mass production of cost-effective, bio-waste derived nanomaterial for a significantly highly efficient candidate for different applications in sustainable chemistry, including flame-retardant applications.
Excited-state proton transfer (ESPT) of pyranine (8-hydroxypyrene-1,3,6-trisulphonate, HPTS) to acetate in methanol has been
studied by steady-state and time-resolved fluorescence spectroscopy. The rate constant of direct proton transfer from pyranine
to acetate (k1) is calculated to be ∼1 × 109 M−1 s−1. This is slower by about two orders of magnitude than that in bulk water (8 × 1010 M−1 s−1) at 4 M acetate. 相似文献
Summary The permanganate ion oxidation of PhCHO in HClO4 medium is first order in [MnO
inf4sup-
], but of complex order with respect to [aldehyde] as well as [H+]. The influence of substituents on the reaction rate and mechanism has also been studied in 40% (v/v) aqueous AcOH and convincing evidence favours an ester formation mechanism. Thermodynamic values associated with 11 intermediate ester formation and the activation parameters associated with the disproportionation steps involved have been evaluated. 相似文献
The present work was designed to develop suitable transdermal matrix patches using the polymer blends of hydroxy propyl methyl cellulose (HPMC) and Eudragit RL100 (ERL) with triethyl citrate as a plasticizer in group A and in group B, other than HPMC and ERL, crosslinking agent, succinic acid was added. A 32 full factorial design was employed for both groups. The concentration of HPMC and ERL were used as independent variables, while percentage drug release was selected as dependent variable. Physical evaluation was performed such as moisture content, moisture uptake, tensile strength, flatness and folding endurance. In vitro diffusion studies were performed using cellulose acetate membrane (pore size 0.45 μ) in a Franz's diffusion cell. The concentration of diffused drug was measured using UV-visible spectrophotometer (V-530, Jasco) at λmax 272 nm. The experimental results shows that the transdermal drug delivery system (TDDS) containing ERL in higher proportion gives sustained the release of drug and patches containing crosslinking agent shows more release than those do not contains succinic acid. 相似文献