Conversion estimates for gas-solid reactions: Improved estimates for irreversible systems

Solid conversion has been of much interest to research workers and the Cumulative Gas Concentration Method (CGCM) has been developed to provide bounds for the reactant solid in irreversible systems having power-law type kinetics. This CGCM is used in conjunction with the Pseudo-Steady-State (PSS) assumption and these bounds appear to be good under certain conditions and for long times.

In this work, the PSS condition is not assumed when deriving the bounds on the cumulative gas concentration and the effect of the inclusion of the transient part is analysed. A technique, based on an iterative scheme incorporating the CGCM, is developed to provide improved estimates for the reactant solid.     

Application of the variational-moment approach to problems of the theory of elasticity of shells

We consider a method of obtaining an approximate system of equations of elasticity theory for shells, based on representing the components of the stress tensor and the displacement vector as a sum of products of moment characteristics depending on the coordinates of the base surface of the shell and functions of the normal coordinate to the base surface.Translated fromMatematicheskie Metody i Fiziko-Mekhanicheskie Polya, Issue 33, 1991, pp. 56–59.     

Studies on solution cast perfluorocarbonsulfonic acid ionomers

The thermal properties of perfluorocarbonsulfonic acid ionomer films cast from solution and their temperature-dependent far infrared spectra have been investigated. In addition to the endotherms and spectral changes associated with the loss of solvent as the films were heated, a significant exotherm has been observed and assigned to the relaxation associated with rearrangements resulting in partially crystallized phases in insoluble thermally treated membranes. © 1993 John Wiley & Sons, Inc.     

Measurement of the spin and temperature dependence of ddµ molecule formation rate in solid and liquid deuterium

The ddµ molecule formation rate is experimentally measured for the two hyperfine states of the dµ-atom in the temperature range of 5–30 K. Results are consistent with a preliminary measurement by the TRIUMF group and contradict theoretical predictions. The work has been performed on the JINR phasotron (Dubna).     

On the solvability of physically nonlinear problems of Thermoelasticity

We study the problem of existence and uniqueness of generalized solutions of nonlinear vector boundary-value problems arising in the physically nonlinear theory of thermoelasticity. We prove the convergence of iteration processes in the space W ¹ ₂.     

Ions and atoms in superfluid helium (4He)

We review the previous conclusion [J.Y. Ryu, Y.C. Chung and S.D. Choi, Phys. Rev. B 32, 7769 (1984)] that the trace property Tr(ABC) = Tr(CAB) leads to two different cyclotron transition absorption formulae in the electron-phonon systems in the lowest order approximation. The pictorial expression and the calculated linewidths in Ge and Si show that the socalled EWC scheme is more seeming than the socalled MWC scheme. The difference is expected to disappear if we take into account all the higher order perturbation terms or start with the many body formalism in the complete scheme.     

Separation of actinides by means of HPLC

A procedure is described separating, identifying and determining the actinides (An) U, Np, Pu, Am and Cm in the presence of the lanthanides (Ln) La, Ce, Pr, Nd, Pm, Sm, Eu and Ho on an analytical scale. It is based on high-pressure liquid chromatography (HPLC) combined with a dual on-line detection system and is accomplished within a short time, in one step and under isocratic conditions (for An). The separation was carried out on a strongly acidic and highly capacitive cationic exchange resin on a polystyrene divinylbenzene copolymer (Aminex A9, co. BioRad) basis. Radionuclides emitting α- and β-particles are detected on-line using a custom-made solid scintillation flow-through cell. Inactive components are monitored by colour reagent complex detection (Arsenazo III, λ-648 nm) with a VIS detector placed in series.