On the determination of the stress-free temperature for alumina–zirconia multilayer structures

Internal residual stresses can enhance the fracture resistance and mechanical reliability of layered ceramics. The magnitude of the stresses depends on the elastic and thermal properties of the layers and the typically assumed reference (stress-free) temperature, below which internal stresses develop. A novel combined experimental and numerical simulation approach has been developed to determine the reference temperature and experimentally proved in alumina–zirconia ceramic laminates. Dilatometric data of monolithic phases are input for the numerical simulation and experimental data on the laminate properties are used for the stress-free temperature determination. In contrast to typical assumptions, reference temperature very near the sintering temperature (i.e. approx. T_ref≈1470 °C) was found, which should be considered for the estimation of internal (residual) stresses in alumina/zirconia-based layered ceramics.     

A REVIEW OF THIRD PHASE FORMATION IN EXTRACTION OF ACTINIDES BY NEUTRAL ORGANOPHOSPHORUS EXTRACTANTS

ABSTRACT

Data are reviewed on the formation of third phase in the extraction of acti-nide(IV.VI) nitrates by neutral organophosphorus extractants, mainly tributyl phosphate. The data are critically evaluated and the effect of variables on the third phase formation is discussed. The variables are the concentrations of nitric acid and the extractant, temperature, the nature of diluent, addition of modifiers and the ionic strength of the aqueous phase. Also discussed are systems involving two extracted actinide ions.     

Linearly tunable quadrature oscillator derived from LC Colpitts structure using voltage differencing transconductance amplifier and adjustable current amplifier

The paper deals with an interesting oscillator solution derived from LC Colpitts circuit structure. Electronically controllable current gain of the current amplifier is utilized for driving of oscillation condition together with two transconductances in frame of voltage differencing transconductance amplifier for adjusting of frequency of oscillation. In the proposed structure these elements replace common bipolar transistor and metal coil. Designed circuit offers important advantages, i.e. absence of metal coil, quadrature outputs, amplitudes of generated signals independent of tuning process, linear electronic control of oscillation frequency (independent of oscillation condition). Implementation of circuit for amplitude stabilization and automatic control of oscillation condition for designed circuit is simple. These benefits are not available in classical LC Colpitts structures or in many well-known third-order oscillators. The theoretical conclusions are supported by experiments with behavioral representation employing commercially available devices and also by simulations using CMOS model.     

Unwanted Pregnancies: Reply.

Responds to the comment by John J. Sigal (see record 2004-14611-009) about the article by David, Dytrych, and Matejcek (see record 2003-03645-009) which showed the long-term negative psychological effects of unwantedness, up to 35 years after birth. The authors state that they were pleased to note Sigal's observation that the conclusions from their Prague study are consistent with findings reported by him and other colleagues on negative psychological effects of unwanted births. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Decision support tools for advanced energy management

Rising fuel costs boost energy prices, which is a driving force for improving efficiency of operation of any energy generation facility. This paper focuses on enhancing the operation of distributed integrated energy systems (IES), system that bring together all forms of cooling, heating and power (CCHP) technologies. Described methodology can be applied in power generation and district heating companies, as well as in small-scale systems that supply multiple types of utilities to consumers in industrial, commercial, residential and governmental spheres. Dispatching of such system in an optimal way needs to assess large number of production and purchasing schemes in conditions of continually changing market and variable utility demands influenced by many external factors, very often by weather conditions. The paper describes a combination of forecasting and optimization methods that supports effective decisions in IES system management. The forecaster generates the future most probable utility demand several hours or days ahead, derived from the past energy consumer behaviour. The optimizer generates economically most efficient operating schedule for the IES system that matches these forecasted energy demands and respects expected purchased energy prices.     

Inductive Effect of Alkyl Chains on Alcohol Dehydration at Bridge-bonded Oxygen Vacancies of TiO2(110)

The activation energies for alkene formation via dehydration of alcohols on bridge-bonded oxygen (BBO) vacancy sites of TiO₂(110) is found to correlate with the inductive electron donating effect of alcohol alkyl groups as measured by the Taft parameter. Based on this correlation we conclude that the reaction involves a single transition state that undergoes concerted rupture of the C–O bond of the alkoxide and a C–H bond of the alkyl group attached to the β-carbon.