The synthesis of bi- and trichromophoric dyes bearing an s-triazinyl ring spacer

An alternative procedure has been described for the syntheses of several bi- and trichromophoric compounds consisting of 1-aminopyrene and 3-aminobenzanthrone chromophoric subsystems connected by an s-triazinyl ring spacer. The synthetic method used, which utilises an autoclave under autogenous pressure, is suitable for the nucleophilic substitution of both chlorine atoms within the triazinyl ring by weakly basic aromatic amines. The structures of the synthesized compounds were confirmed using elemental analysis, ¹H NMR, and mass spectra. UV/vis absorption and fluorescence spectra and fluorescence quantum yields were measured. The dependence of fluorescence intensity and fluorescence quantum yields on solvent polarity was investigated.     

Representativity of the singular stress state in the failure of adhesively bonded joints between metals and composites

Several critical points, where both geometry and material properties change abruptly, arise in an adhesively bonded lap joint between a metallic and a composite material. These critical points, called multimaterial corners or cross-points, at which the linear theory of elasticity predicts unbounded (singular) stresses, are potential points for failure initiation. In this work, a complete stress characterization at these multimaterial corners has been carried out to analyze, after a preliminary experimental test program, the suitability of the application of the parameters defining the singular stress state in the characterization of the failure of these joints. The comparative analysis of the numerical and experimental results obtained show that the singular stress state controlled by a series of the generalized stress intensity factors is controlling the failure path at these corners.     

Anomalous dilatation-temperature curves of PZT-ZrO2 composites

The dilatation-temperature curves of the PZT-ZrO₂ composites, containing 1.3–13.2 vol% ZrO₂ were studied. The course of martensitic transformation (MT) of dispersed ZrO₂ particles in the PZT matrix was followed. Upon cooling, a spontaneous microcrack formation occurred during the MT from tetragonal to monoclinic crystal phase of ZrO₂. The phenomenon of intensive shrinkage above 800 °C upon heating is explained as a process of microcrack healing in the presence of the PbO-rich liquid phase.     

The influence of cavitation damage upon high temperature creep under stationary and non-stationary loading conditions: Part IV: Cyclic creep at constant load amplitude and constant true stress amplitude

The aim of the present paper is to investigate the influence of high temperature cavitation upon the creep behavior of ideally plastic materials subjected to tensile load cycling. In the present treatment the oscillating tensile stress is replaced by a static equivalent stress which is a function of the loading conditions. Creep equations are derived for cavitating and non-cavitating specimens respectively. The volume change for constant load amplitude cycling is calculated. The main results derived for different loading procedures are also compared.     

Thermophysical Properties of Electrically Conductive SiC–(Nb,Ti–C)<Subscript>ss</Subscript>-Based Cermets

Multifunctional cermets are being developed for a range of novel applications. The present paper deals with thermophysical properties of electrically conductive SiC-based cermets. The cermets were prepared by in situ reaction using a two-step sintering process. The thermophysical properties, namely, thermal conductivity, thermal diffusivity, and heat capacity, were measured using the pulse transient technique. The microstructure and chemical composition of the samples were characterized by SEM (scanning electron microscopy), TEM (transmission electron microscopy), STEM (scanning transmission electron microscopy), and EDX (energy dispersive X-ray analysis) techniques. The observed thermophysical data were correlated with the observed microstructures and chemical nature of the SiC-based cermets.     

Special paraunitary matrices, Cayley transform, and multidimensional orthogonal filter banks.

We characterize and design multidimensional (MD) orthogonal filter banks using special paraunitary matrices and the Cayley transform. Orthogonal filter banks are represented by paraunitary matrices in the polyphase domain. We define special paraunitary matrices as paraunitary matrices with unit determinant. We show that every paraunitary matrix can be characterized by a special paraunitary matrix and a phase factor. Therefore, the design of paraunitary matrices (and thus of orthogonal filter banks) becomes the design of special paraunitary matrices, which requires a smaller set of nonlinear equations. Moreover, we provide a complete characterization of special paraunitary matrices in the Cayley domain, which converts nonlinear constraints into linear constraints. Our method greatly simplifies the design of MD orthogonal filter banks and leads to complete characterizations of such filter banks.     

Organobentonite as Efficient Textile Dye Sorbent

Domestic bentonite clay was modified using cationic surfactant – hexadecyltrimethylammonium bromide (HDTMA‐bromide) in order to obtain more efficient sorbent. Removal of Acid Orange 10 from aqueous solution at different dye concentrations, adsorbent doses, and pH was studied. These studies were carried out under unaltered pH value in order to prove that adjusting pH as an additional operation in wastewater treatment is not entirely necessary. The results obtained confirmed the adsorption capacity is significant even for unaltered pH. The adsorption isotherm data were well fitted with both the Freundlich and Langmuir model and the latter was shown as more appropriate. Dynamical data were well represented with the pseudo second‐order kinetic model. The results indicate that HDTMA‐bentonite could be employed as low‐cost sorbent in textile dye wastewater treatment.     

Ultimate strength of I-girders under eccentric patch loading: Derivation of a new strength reduction coefficient

In structural applications I-girders are subjected to eccentric patch loading since even a small eccentricity of applied loads relative to the web plane is unavoidable in practice. Experimental research shows that the behaviour of eccentrically loaded girders differs from that of concentrically loaded girders. A reduction in ultimate strength due to eccentricity is evident, and some expressions for the reduction have been proposed. We show that these expressions overestimate the reduction in capacity for large eccentricities. In this paper, results of 102 tests on I-girders subjected to eccentric patch loading are presented and the variables involved in the phenomenon are evaluated based on a parametric study of experimental data and the results of several finite element models. The parametric study confirms that the parameters previously identified for evaluating the effect of small eccentricities are sufficient for addressing cases with larger eccentricities. New mathematical expressions are proposed herein to represent the reduction in strength across the full range of eccentricities considered.