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31.
One of the characteristic examples of the inability of the classical linear frequency response (FR) method to identify the correct kinetic mechanism is adsorption of some substances (p-xylene, 2-butane, propane or n-hexane) on silicalite-1. The linear FR resulted with bimodal FR characteristic functions, which fitted equally well to three different kinetic models: nonisothermal micropore diffusion, two independent isothermal diffusion processes, and an isothermal diffusion-rearrangement process. We show that the second order frequency response functions (FRFs), obtained from the nonlinear FR, can be used for discrimination among these three mechanisms. Starting from the nonlinear models, we derive the theoretical expressions for the first and second order FRFs corresponding to these three mechanisms and show that different shapes of the second order FRFs are obtained for each mechanism. This would enable identification of the real mechanism from nonlinear FR data. 相似文献
32.
epan S. Miljanic Bojan B. Radak Ljubica T. Petkovska 《Journal of Chemical Sciences》1991,103(3):405-408
Spectra of coincidence of CH3F IR absorption with CO2-laser emission at pressures of 2, 10 and 60 Torr were recorded by the use of a photoacoustic detection method in the whole
range of CO2-laser emission. The spectra show that CH3F absorbs many CO2-laser lines in the range 1084–1071 cm−1 with the strongest absorption at 1046.80cm−1, laser line P(20). Absorption is predominantly due to the fundamental of v3, which is well spread over the whole laser emission range. The intensities of all absorptions rise with increasing pressure,
but some absorptions change their relative intensity with respect to one another. In addition, the fine structure of the line
spectrum, characteristic of lower pressure samples, disappears as pressure is increased. 相似文献
33.
Maria A. Simonova Andrey R. Khayrullin Valerija O. Turina Sofija I. Kamorina Denis M. Kamorin Anton Yu Sadikov 《International Journal of Polymer Analysis and Characterization》2019,24(7):630-638
Thermo- and pH-responsive statistical copolymers of N-(dimethylamino)ethyl methacrylate and lauryl methacrylate were synthesized by free radical copolymerization. Obtained samples differed in content of hydrophobic components (3 and 6?mol. %). Their molar masses were close to 30,000?g/mol. Self-organization in buffer solutions of copolymers were studied using light scattering and turbidimetry. It was found that copolymers as well as of poly(N-(dimethylamino)ethyl methacrylate) were thermosensitive at pH?>?7. Phase separation temperatures of investigated solutions decreased with dilution and pH increasing. Growth of lauryl methacrylate content in copolymers caused the decrease in phase separation temperatures. 相似文献
34.
Kuzmanović Predrag Todorović Nataša Filipović Petrović Leposava Mrđa Dušan Forkapić Sofija Nikolov Jovana Knežević Jovana 《Journal of Radioanalytical and Nuclear Chemistry》2020,324(3):1077-1087
Journal of Radioanalytical and Nuclear Chemistry - This paper presents a gamma spectrometric analysis of 47 samples of building materials produced and used in Serbia. Based on the measured activity... 相似文献
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36.
Theoretical development of a new experimental method for investigation of mass transport in porous membranes, based on the
principle of the modified Wicke-Kallenbach diffusion cell and the nonlinear frequency response analysis is presented. The
method is developed to analyze the transport of a binary gas mixture in a porous membrane. The mixture is assumed to consist
of one adsorbable and one inert component. Complex mass transfer mechanism in the membrane, where bulk or transition diffusion
in the pore volume and surface diffusion take place in parallel, is assumed. Starting from the basic mathematical model equations
and following a rather standardized procedure, the frequency response functions (FRFs) up to the second order are derived.
Based on the derived FRFs, correlations between some characteristic features of these functions on one side, and the whole
set of equilibrium and transport parameters of the system, on the other, are established. As the FRFs can be estimated directly
from different harmonics of the measured outputs, these correlations give a complete theoretical basis for the proposed experimental
method. The method is illustrated by quantifying the transport of helium (inert gas) and C3H8 and CO2 (adsorbable gases) through a porous Vycor glass membrane. 相似文献
37.
Ksenija Babić-Samardžija Norman Hackerman Sofija P. Sovilj Vladislava M. Jovanović 《Journal of Solid State Electrochemistry》2008,12(2):155-163
The inhibiting effect of cobalt(III) complexes with macrocyclic ligand cyclam (1,4,8,11-tetraazacyclotetradecane) and β-diketonato ligands have been investigated on iron corrosion in 0.1 M HClO4 by potentiodynamic, linear polarization resistance (LPR), and electrochemical impedance spectroscopy (EIS) measurements.
Analysis of the polarization curves and impedance spectra, by adding complex compounds to the acid solution and comparing
with inhibitor-free solution, show corrosion current decrease and charge transfer resistance increase, respectively. Impedance
data are fitted with equivalent circuit models. The stability of the adsorbed film was followed by LPR. Scanning electron
microscopy (SEM) was used to screen physical changes of the reacted surfaces both treated and untreated. The differences in
inhibitor efficiencies depend on the substituent group of the coordinated β-diketone ligand. Structural and electronic properties
of this group of compounds in relation to inhibitor efficiency were analyzed by using the molecular modeling structures and
correlated with previously reported spectroscopy data. 相似文献