Certain similarities between the types of data reported in retrospective citation analyses and lifetime/survival/reliability models are noted. Graphical techniques much used in reliability analyses are exploited to throw further light on observed citation age distributions and these are then compared and contrasted with previously reported studies. These simple techniques allow systematic departures of empirical data from assumed theoretical models to be highlighted and the models to be compared.
A graphic method is proposed to determine all of the kinetic parameters in Wigner-Polanyi equation of desorption. A desorption rate curve from a single temperature-programmed desorption experiment is required by this method to determine the order of reaction (n), the activation energy (Ed) and the pre-exponential factor (v) of the equation. The proposed method has been applied to the oxygen desorption from PdO/Al2O3 samples prepared by impregnating γ-Al2O3 with H2PdCl4 solution used as examples. From the graphic method, the values ofn=2, andv=1.37±0.80×109 s−1 were successfully determined for the desorption. The value ofEd depended on the dispersion of palladium (D) on PdO/Al2O3 samples, and was expressed by the equation:Ed=175+174D kJ·mol−1. This graphic method is a direct and time-saving technique, on comparing with other methods suggested in the literature, for analysis of data from temperature-programmed desorption of simple desorption processes.
Authors:C. Barros Leite, G. Baptista, E. Montenegro, and A. Paschoa
A graphical method was developed to relate data from Rutherford backscattering spectrometry to sample characteristics, such as thickness and concentration profiles. The method was then applied to analyze these characteristics of a gold film.
The applicability of the numerical-graphical method for determining the ion exchange capacity described previously1 was examined for the system Sr2+−H+-polyantimonic(V) acid in 0.1–0.5M HNO3. The construction of the ion exchange isotherms by a modified McCabe—Thiele procedure is also discussed.
A numerical-graphical method is described for determining the apparent capacity of an ion exchanger for univalent and multivalent
ions, assuming that other interactions with the electrolyte, such as adsorption, precipitation, etc., are vanishingly small
in comparison with the ion exchange process.
A simple graphical method for determination of thermodynamic equilibrium constants, developed for ion-exchange and solvent
extraction processes, was successfully applied to a liquid exchangersystem. Close values of the thermodynamic equilibrium
constants for the system uranyl chloride—hydrochloric acid—di-2-ethylhyxyl phosphoric acid—toluene (K=7.8±0.8) were obtained
when the ionic strength of the aqueous phase was varied and the concentration of di-2-ethylhexyl phosphoric acid in the organic
phase was kept constant, and vice versa.
Authors:C. Telea, O. Chilom, Gabriela Geambas, and V. Popa
In this paper a graphical and analytical method is presented for generating reaction isotherms from a set of non-isotherms
andvice versa. The method was tested by using computer generated curves. The method was also checked by studying the kinetics of dehydration
of calcium oxalate in a static atmosphere. The reaction was monitored in both non-isothermal (with nine heating rates between
0.5 and 60°C min−1) and isothermal modes (at 150, 160 and 170°C). The 160°C isotherm obtained experimentally was compared with that obtained
by graphical method from non-isotherms determined experimentally and the differences of α were less than 3%.
Spectrophotometric study of solvation equilibria of uranium(VI) with N,N-dimethyl formamide (DMF) in solutions with ionic strength I = 3.0 mol.dm-3 (Na, H)ClO4 shows that DMF forms with UO22+ several relatively stable solvates absorbing in VIS range (350-490 nm). The absorbance of UO22+ bands increases and their absorption maxima shift to longer wavelengths while uranyl solvates are formed stepwise with increasing concentration of DMF. Areas of prevailing existence of individual solvates with stoichiometry 1 :n(n= 1, 2, 4, 6) have been found and their stability constants and molar absorption coefficients estimated using both graphical methods and computer minimization programs.
The co-ordination of plutonyl ions with 2-thenoyltrifluoroacetone (HTTA) has been investigated by distribution studies of239Pu between benzene and aqueous perchlorate medium at 25°C in order to understand the nature of the extracted species and their
stability. The formation constants of the first and second complexes have been evaluated by Rydberg's graphical method as
well as by least squares analysis of the distribution data using a computer programme. The overall formation constant (β2) for Pu(VI)-HTTA system has been found to be of the order of 1012.
The mechanics of thermally-activated gaseous diffusion in polymers have long been studied for development of theoretical understanding
of the interactive forces responsible for the non-linear nature of diffusion and the resultant enthalpic changes in the polymer.
Methodologies and calculations have been developed in this work for treatment of experimental data for elimination of thickness-related
anomalies in water vapor diffusion and for delineation of pressure effects. Linearized data for different polymer thicknesses
and the attendant internal thermal effects have been generated by using calculated single molecule diffusion values. Equally
linear data are obtained for different pressures by the use of a graphical method from which identical diffusion values are
obtained, independent of material thickness and external pressure. True comparisons and classification of polymers as to their
diffusivities are thus possible for development of barrier materials for food and drug packaging and for protective encapsulation
of electronic devices.
Results will be reported for three structurally different polymers.