The purpose of this paper is to revise von Neumann’s characterizations of selfadjoint operators among symmetric ones. In fact, we do not assume that the underlying Hilbert space is complex, nor that the corresponding operator is densely defined, moreover, that it is closed. Following Arens, we employ algebraic arguments instead of the geometric approach of von Neumann using the Cayley transform.
GLÄNUZEL, W., A characterization theorem based on truncated moments and its application to some distribution families, Mathematical statistics and probability theory (Bad Tatzmannsdorf, 1986), Vol. B, Reidel
Authors:D. Chinn, Sang -Beom Shim, and J. C. Seferis
Five epoxy resins of different chemistry and functionality were cured with DDS (4,4′-diaminodiphenyl sulfone) using 2, 8 and 14 h curecycles. Both Differential Scanning Calorimetry (DSC) and Thermomechanical Analysis (TMA) were used to characterize reaction behavior and cured properties of the resin systems. In addition, static mechanical tests and density measurements were integrated with the thermal characterization methods to correlate resin properties with process time. Flexural three-point bending experiments showed that the resins tended to have higher yield stress and toughness values at extended cure times. The improved mechanical properties could be attributed to the full development of the epoxy molecular structure, in the form of cross-linked networks and molecular rearrangement. These results suggest that extended cure times or high temperature post-curing may be required to obtain the resin's ultimate mechanical properties for high performance composites.
Authors:Dragana Živković, A. Milosavljević, A. Mitovski, and B. Marjanović
The results of thermodynamics and characterization of alloys in ternary Ag-In-Sn system is presented in this paper. Thermodynamic
properties, in three investigated sections with molar ratio In:Sn=1:1, 1:2 and 1:4, have been calculated at the temperature
of 1423 K using different predicting methods (general solution model, Toop, Hillert, Muggianu, Kohler, Redlich-Kister), compared
mutually and with literature experimental data. The alloys in investigated sections have been characterized using DTA, XRD,
SEM and optic microscopy.
The synthesis and characterization of lanthanide(III) citrates with stoichiometries 1:1 and 2:3; [LnL·xH2O] and [Ln2(LH)3·2H2O], Ln=La, Ce, Pr, Nd, Sm and Eu are reported. L stands for (C6O7H5)3− and LH for (C6O7H6)2−. Infrared absorption spectra of both series evidence coordination of carboxylate groups through symmetric bridges or chelation.
X-ray powder patterns show the amorphous character of [LnL·xH2O]. The compounds [Ln2LH3·2H2O] are crystalline and isomorphous. Emission spectra of Eu compounds suggest C2v symmetry for the coordination polyhedron of [LnL·xH2O] and C4v for [Ln2(LH)3·2H2O]. Thermal analyses (TG-DTG-DTA) were carried out for both series. The thermal analysis patterns of the two series are quite
different and both fit in a 4-step model of thermal decomposition, with lanthanide oxides as final products.
Authors:G. Madhurambal, P. Ramasamy, P. AnbuSrinivasan, M. Suganthi, G. Vasudevan, and S. Mojumdar
Good quality benzophenone (BP) crystals were grown by solution technique using CHCl3 as solvent by adopting slow evaporation method at room temperature. The grown crystals were subjected to various characterization
studies to analyze its purity and applications. The condensation product 2,4-dinitro phenyl hydrazone of benzophenone (DNPBP)
was prepared by adopting standard procedure. Then mixed crystal of BP and DNPBP was also grown by solution growth. Both the
condensation product and mixed crystals were characterized by UV, FTIR, 1H NMR spectra. Thermal (TG and DTA) studies have proved to be very useful techniques not only to study the thermal properties
of BP, DNPBP and mixed crystal but also to study their purity. Second harmonic generation (SHG) efficiency of the grown crystals