Optimizing of Balances of the Second Generation

At the 3rd Conference on Vacuum Microbalance Techniques in Los Angeles in 1962, we suggested the use of the equation of motion of a balance T=J+α+kα+Cα for the calculation of the unknown torque T, and the measurement for that purpose of the values of all the other quantities in this equation. The present paper discusses the consequences of two sources of error relevant for this method. First, the errors caused in the first and second derivatives of the deflection are considered, deduced from two or three deflection measurements separated by small time intervals. Secondly, the consequences of the errors caused by the uncertainties in the deflection measurements are discussed. Consideration of the two errors together leads to an optimal set of values of parameters for the balance handling. This revised version was published online in July 2006 with corrections to the Cover Date.     

Criticism on Jäntti's Three Point Method on Curtailing Gas Adsorption Measurements

Jäntti introduced a method to reduce the time required for the stepwise measurement of adsorption isotherms (Jäntti et al., Progress in Vacuum Microbalance Techniques, Vol. 1, Heyden, London, pp. 345–353, 1972). After a pressure change he measured the adsorbed mass three times and calculated its equilibrium value for the new pressure. In the present paper we discuss the applicability of this method in a broader scope (without starting from a single combination of gas and solid adsorbent) and also discuss the influence of measurement inaccuracies. It is shown that the method can serve as an early warning system, which decides whether an improvement of the adsorption model is necessary.     

Evaluation of the applicability of Jäntti’s method to volumetric sorption measurements

Jäntti published in 1970 a method to obtain values of the sorption parameters at an early stage of gravimetric sorption measurements. In the present paper we apply that method to volumetric sorption measurements to discuss its applicability. A method is presented to cope with inaccuracies when using Jäntti’s method. This will be of special importance for volumetric measurements where accuracy plays a major part. In the paper a second order regression method is used. We use a computer simulation as well as experimental data on desorption of nitrogen from a silica aerogel at 77 K.     

Effect of Sπ on the Polymerization of Liquid Sulfur and the Nature of Sπ

The Tobolsky-Eisenberg theory serves to explain the equilibrium polymerization of sulfur in terms of the dependence of S₈ (ring) concentration on temperature and the dependence of number-average degree of polymerization on temperature. The predictions of the theory are completely in accord with experiment. In this paper it is shown that it is possible to take the presence of another component in the melt, Sπ, into account, using a slightly modified version of the Tobolsky-Eisenberg theory. When this is done it is found that the earlier conclusions remain valid. The molecular complexity and structure of Sπ is also discussed.     

Extension of The Applicability of Jäntti's Method For Fast Calculation of Adsorption Data

The time for adsorption measurements can be substantially reduced by measuring several values at short time intervals at the beginning of the kinetic curve and extrapolation of the equilibrium value. The method used by Jäntti for simple adsorption processes has been extended for complicated processes using a second order differential equation. A simulated example is calculated.     

Application of the nonunitary model operator approach to the16O nucleus

The nonunitary model operator approach, which has been previously described, is applied to the¹⁶O nucleus. Approximate expressions are given for the ground-state energy of this nucleus, by using both variational methods with the separation condition, developed in our previous work. Simple hardand softcore potentials are employed in the computations and the results obtained with the two methods are discussed.     

The measurement of magnetic susceptibilities with commercially available milli-oerstedmeters,III

In preceeding papers a method was described for measuring magnetic susceptibilities without the use of a balance. In the present paper the application of that method to low and high temperature measurements is reported. The measurement accuracy is some factor 30 smaller than in the earlier experiments, because of the necessary alterations in the set-up. Measurements on CuSO₄-5H₂O are in support of the data reported by Reekie.     

Calculations of the velocity profiles in the vicinity of a sphere at intermediate Reynolds numbers; consequences for the micro-anemometer calibration unit

The axi-symmetrical steady viscous flow past a sphere in a uniform flow in a cylinder of finite length is calculated with the finite element method and a penalty function approach. Our numerical results for the drag coefficient, the standing eddy length and the angle of flow separation as a function of Reynolds number agree well with literature. The velocity profiles in the vicinity of the sphere show that for distances larger than 3 × radius of the sphere and angles much larger than the angle of flow separation the influence of the sphere is less than 5%. The velocity at the position of our micro-anemometer is equal to the velocity generated by the calibration unit within 5%. From the numerical calculations the conclusion can be drawn that spherical micro-anemometers with diameters up to 20% of the diameter of the calibration unit can be calibrated.     

The influence of state dependent short range correlations on the depletion of the nuclear Fermi sea

The inlfuence of state dependent short range correlations on the occupation numbers of the single particle shell model orbits of the doubly closed shell nuclei¹⁶O and⁴⁰Ca is examined. The study shows that the effect of the state dependence of the short range correlations is rather small. The total depletion of the nuclear Fermi sea changes slightly compared with the one calculated by considering state independent short range correlations.