The dicalcium orthosilicate and its hydraulic activity examination by DTA-TG and calorimetric methods

The belite material produced from limestone and waste silica was the subject of numerous investigations. In order to improve the hydraulic activity, some amount of barite was added to the raw mixture. The properties of belite phase were studied by use of differential thermal analysis, calorimetry and other methods. The influence of barium on the hydraulic activity of belite has been thus confirmed. The hydraulic activity increase in the presence of barium depends on the stabilizing action of additive accompanied by the proper thermal treatment in the α′-Ca₂SiO₄ stability range.     

Structural constrained controllers for discrete-time linear systems

In this paper, we present an approach for designing structural constrained controllers for discrete-time linear systems, based on a new stabilizability property of the Riccati equation solution. First, the feedback stabilization problem under a general structural constraint is considered and a simple numerical procedure to solve it is presented. Special attention is given to the output feedback stabilization problem, for which sufficient conditions for the existence and convergence toward a stabilizing matrix are provided. Some examples are solved and comparisons with other methods available in the literature are made.This research has been developed with the financial support of the Conselho Nacional de Desenvolvimento Científico e Tecnológico, CNPq, Brasília, Brazil.     

Estimation of plate elastic moduli through vibration testing

This paper considers the identification problem for 2D-structures by comparing a modal method with a new method based on the estimation of the dispersion equation in k-space. Both methods are validated by numerical simulation and by measurements based on an acoustic holography experiment.     

Ligand-stabilized Nickel and Palladium Boride Colloids

A route to the first ligand stabilized nickel and palladium boride colloids with core diameters of 1.4 and 1.6 nm is described. The particles are formed by reaction of the metal complexes Cl₂M(PR₃)₂ (M = Ni, Pd, PR₃ = PPr₃, PBu₃) with B₂H₆ in toluene at room temperature with 40–70% yield. The characterization of the pyrophoric brown powders occurred by elementary analyses, resulting in smallest formula units, which then could be extended to averaged molecular formulas by mass determinations, using an analytical ultracentrifuge: [Ni₆B₁₀Cl_1.5(PPr₃)]_12.5 ( 1 ), [Ni₆B₁₀Cl_1.5(PBu₃)]_8.5 ( 2 ), [Pd₄B₆Cl(PPr₃)]_16.5 ( 3 ), and [Pd₄B₆Cl(PBu₃)]_16.5 ( 4 ). From the masses of the colloid cores and their roughly calculated densities the size of the boride particles could be estimated. The diameters of 1.6 nm for 1, 3 , and 4 are identical within the experimental error. Only 2 seems to have a slightly reduced diameter of 1.4 nm. 1–4 can be dispersed in inert organic solvents in any concentration. To confirm these relatively uncertain values high resolution transmission electron microscopy has been used. Investigations of 1 and 3 show indeed an averaged particle size of 1.6 ± 0.3 nm in agreement with the data derived from the mass determinations. Surprisingly most of the observed particles appear to have amorphous structure. This finding is supported by X-ray powder diffraction experiments, as no significant reflex data could be registered. ³¹P and ¹¹B NMR measurements have been performed too, however, do not contribute to further characterization.     

Measurement of electrodynamic parameters of superconducting films in the far-infrared and submillimeter frequency ranges

Possibilities of determing the complex conductivity of thin super-conducting films using far-infrared and submillimeter reflectivity and transmissivity techniques are discussed. It is shown that within the framework of standard approaches a satisfactory accuracy is available only for the imaginary part of the conductivity (dielectric permittivity). Different resonator methods are suggested for measuring the real part of the conductivity. Data for superconducting NbN films at frequencies 3 – 25 cm^–1 are presented.     

Neck propagation in polyethylene

Intrinsic true stress–true strain response was evaluated at room temperature for three linear polyethylene samples deformed in conventional tensile tests. It was observed that high crystallinity is associated with a low rate of strain hardening that results in a sharp neck and a large drop in nominal stress. The maximum and minimum deformation loads are accounted for by Considère's analysis of neck initiation and stabilization, respectively. Following stabilization, neck propagation occurs at a load or nominal stress that is lower than the yield stress. The jump analysis of Ericksen and Hutchinson/Neale predicts steady state neck propagation stresses that are in very good (ca. 10%) agreement with experiment. Although the jump analysis is done in terms of uniaxial stress, the actual value of the propagation stress is established by the triaxial stress state in the neck shoulders. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2081–2091, 2004     

Bayesian inferences on nonlinear functions of the parameters in linear regression

A variety of statistical problems (e.g. the x-intercept in linear regression, the abscissa of the point of intersection of two simple linear regression lines or the point of extremum in quadratic regression) can be viewed as questions of inference on nonlinear functions of the parameters in the general linear regression model. In this paper inferences on the threshold temperatures and summation constants in crop development will be made. A Bayesian approach for the general formulation of this problem will be developed. By using numerical integration, credibility intervals for individual functions as well as for linear combinations of the functions of the parameters can be obtained. The implementation of an odds ratio procedure is facilitated by placing a proper prior on the ratio of the relevant parameters.Financially supported by the University of the Orange Free State Research Fund.     

Measurement of optical constants of thin polymer films using spectrally resolved white light interferometry

Using the spectrally resolved white light interferometry we present our experimental results on the measurement of the optical constants of thin polymer films coated on a transparent substrate. As an extension to our previous work (J. Opt. Soc. Am. B12, 1559 (1995)) on thick glass plates, we have shown here that this technique can be effectively applied to very thin polymer films also. We have improved the accuracy of our results by using the Sellmeier dispersion formula for fitting the data. From the width and position of the zero-order fringe and the frequency of modulations in the white light spectrum, the refractive indexn(λ) and thicknesst of the thin polymer films are calculated. To study the accuracies involved in the technique, PVA, PMMA and PS films of varied thicknesses are coated on glass plates and the measured values are compared with ellipsometer studies.     

Spectroscopy of nickel chloride: Identification of the [15.0] Π3/2 and [15.0] Δ5/2 states

Vibrational bands belonging to the [15.0] ²Δ_5/2-A²Δ_5/2, [15.0] ²Δ_5/2-X²Π_3/2, and [15.0] ²Π_3/2-X²Π_3/2 electronic transitions of NiCl have been observed in the 14 000-16 000 cm⁻¹ region. The [15.0] ²Δ_5/2 and [15.0] ²Π_3/2 states are identified for the first time. The observed bands have been recorded at high spectral resolution using several techniques, which include intracavity laser spectroscopy (ILS), Fourier transform emission spectroscopy (FTS), and laser induced fluorescence (LIF) spectroscopy. For the ILS absorption spectra, NiCl molecules were produced in a nickel hollow cathode operated with a small amount of CCl₄. For the FTS emission spectra, excited NiCl molecules were produced in a King-type carbon tube furnace loaded with NiCl₂ and heated to 1600 °C. In the LIF work, NiCl molecules were produced by reacting laser-ablated nickel with PCl₃ seeded in argon. Detailed analysis of rotational transition lines indicates that the observed [15.0] ²Δ_5/2 and [15.0] ²Π_3/2 states are only separated by 10 cm⁻¹ and are interacting with each other. Molecular constants for these newly observed electronic states are reported.     

Multi-isotopologue analyses of new vibration-rotation and pure rotation spectra of ZnH and CdH

High resolution infrared emission spectra of ZnH, ZnD, CdH, and CdD have been recorded with a Fourier transform spectrometer. The v = 1 → 0 and v = 2 → 1 bands of ZnH, ZnD, CdH, and CdD, as well as the v = 3 → 2 band of ZnD were observed for the X²Σ⁺ ground electronic state. In addition, new rotational spectra have been recorded for CdH and CdD using a tunable far-infrared spectrometer, and pure rotational transitions in the v = 1 level of the ground state were measured. The new data were combined with the previous data from diode laser infrared spectra and pure rotation spectra of ZnH/ZnD and CdH/CdD available in the literature. The data from all isotopologues were fitted together using a Dunham-type energy level expression for ²Σ⁺ states, and Born-Oppenheimer breakdown correction parameters were obtained. The equilibrium rotational constants (B_e) of ⁶⁴ZnH, ⁶⁴ZnD, ¹¹⁴CdH, and ¹¹⁴CdD were determined to be 6.691332(17), 3.402156(7), 5.447074(18), and 2.750761(6) cm⁻¹, respectively, and the associated equilibrium internuclear distances (r_e) are 1.593478(2), 1.593001(2), 1.760098(3), and 1.759695(2) Å, respectively. Simple reduced mass scaling for the spin-rotation interaction constants of ZnH and CdH fully accounted for their isotopologue dependence, and no Born-Oppenheimer breakdown correction was required for these parameters.