Urbanisation and psychiatric admission rates in The Netherlands

This article discusses the possible links between urbanisation, demographic variables and psychiatric admission rates. Inpatient psychiatric admission rates were determined for the 647 Dutch municipalities. Then urbanisation was determined using 'area address density', a unit of measurement developed by the Dutch Central Statistical Office. Five degrees of urbanisation are distinguished. Twenty-nine demographic variables which might have a theoretical link with admission rates were collated for all municipalities. The results show that standardised total admission rates increase with urbanisation. The mean admission rate for the least urbanised municipalities is 2.02 per 1000 resident population, the rate for the most urbanised municipalities is 3.72 per 1000. It was then found that the prevalence of demographic risk factors increased with urbanicity. At the same time, it was found that almost all demographic variables correlated with admission rates. A multiple regression mode--which accounts for 22% of variance--shows that income distribution, address density and mortality all contribute significantly to the variance in admission rates for the 647 Dutch municipalities.     

Modeling of Thermal Stresses in Joining Two Layers with Multi- and Graded Interlayers

The technique of introducing interlayers has been used extensively to mitigate residual thermal stresses in joining dissimilar materials. Finite-element analyses have often been used to quantify thermal stresses in these layered structures in case-by-case studies. Recently, simple analytical models containing only three unknowns have been developed to derive closed-form solutions for elastic thermal stresses in both multilayer systems and two layers joined by a graded junction. The analytical solutions are exact for locations away from the free edges of the system. Application of these solutions is shown here to provide a systematic study of thermal stresses in Si₃N₄ and Al₂O₃ layers joined by various sialon polytypoid-based multi- and graded interlayers. The effects of the thickness, stiffness, and coefficient of thermal expansion of the interlayer on thermal stresses in the system are examined. The differences in thermal stresses resulting from multi- and graded interlayers are shown.     

Asymptotic expression for the equivocation probability of the NDA FF carrier synchroniser

Equivocation in nonlinear feedforward carrier synchronisers considerably degrades the symbol error rate performance. A simple asymptotic (high E/sub s//N/sub 0/) expression for the equivocation probability is derived for two types of averaging filter and general nonlinearity. The expression is proven accurate in the E/sub s//N/sub 0/ region of practical interest. The results extend previous work.<>     

Precoarsening to Improve Microstructure and Sintering of Powder Compacts

MgO and Al₂O₃ were sintered by two types of processes: a conventional isothermal sintering and a two-step sintering consisting of an initial low-temperature precoarsening treatment before conventional isothermal sintering. The final microstructure from two-step sintering can be more uniform and finer than that of compacts sintered conventionally. A narrow-size-distribution alumina powder was sintered under constant-heating-rate conditions, with and without a precoarsening treatment, and the results were compared. The differences between two-step and conventional processing were clarified by experiments on precoarsened and as-received ZnO powders. These compacts were precoarsened at 450°C for 90 h with virtually no increase in the overall density. The resulting grain size was 1.7 times the starting one, but the standard deviation of the precoarsened powder size distribution was smaller than that of the asreceived powder. Precoarsened compacts sintered to nearly full density showed improved homogeneity. The sintering stress of the precoarsened ZnO was approximately 0.8 that of the as-received one. A computational model has been used with two components of coarsening to describe the differences in pore spacing evolution between the precoarsened and the as-received system. The benefit of two-step sintering is attributed to the increase in uniformity resulting from precoarsening. The increased uniformity decreases sintering damage and allows the system to stay in the open porosity state longer, delaying or inhibiting additional coarsening (grain growth) during the final stage of densification. Two-step sintering is especially useful for nonuniform powder systems with a wide size distribution and is a simple and convenient method of making more uniform ceramic bodies without resorting to specialized powders or complicated heat schedules.     

Whisker growth in reduction of oxides

Cobalt ferrite (CoFe₂O₄) was reduced in CO-CO₂ gas mixtures at 1173 K at total pressure between 6.6 × 10³ and 3.3 × 10⁴ Pa, and at CO/CO₂ ratios between 2.9 and 11.8. The reduction led to the formation of metal whiskers. The experiments and analysis emphasized the behavior of the whisker diameter during reduction. Impurities such as calcium and potassium stimulate metal nucleation but appear to inhibit catalysis of gas reactions at the metal/gas/oxide triple junction. The steady state whisker diameter was found to be inversely proportional to the total gas pressure at constant CO/CO₂ ratio. A new model is proposed to explain whisker development. It considers metal/oxide interface diffusion coupled with a metal/oxide/gas triple junction reaction at the whisker base as the process determining the whisker diameter.     

Data compression of ECG''s by high-degree polynomial approximation

A method for the compression of ECG data is presented. The method is based on high-degree polynomial expansions. Data rates of about 350 bits per second are achievable at an acceptable signal quality. The high compression is obtained by a carefully selected subdivision of the ECG signal into intervals that make optimal use of the special properties of the polynomial base functions. Each interval corresponds to one ECG period. The method is compared to the discrete cosine transform and is found to yield a significantly higher data compression for a given signal quality (quantified by mean squared error and peak error).     

Tracking performance comparison of two feedforward ML-orientedcarrier-independent NDA symbol synchronizers

The authors deal with two types of feedforward carrier-independent non-decision-aided (NDA) symbol synchronizers for PAM, which are based upon the maximum-likelihood criterion. Their timing error variances are compared, for two important classes of signal constellations     

Effect of Rigid Inclusions on the Sintering of Glass Powder Compacts

The effect of rigid inclusions on the sintering of glass powder compacts has been investigated at 600°C. The densification rates show good agreement with the rule of mixtures for inclusion volume fractions of °0.1 The transient stresses generated during sintering by the presence of the inclusions were evaluated from the sintering data. Below inclusion volume fractions of °0.12, the results are in excellent agreement with Scherer's theory for viscous sintering with rigid inclusions. At higher inclusion volume fractions, interactions between the inclusion particles lead to large deviations from theoretical predictions.     

Grain boundaries and ionic conduction in sodium beta alumina

Grain boundary morphology and structure has been examined by means of transmission electron microscope lattice imaging, and a plausible correlation is advanced between the grain boundary structure and its transgranular ionic resistivity and capacitance. The geometrical aspects and resistance of the grain boundaries depend on whether or not dislocations with ab=1 spinel block can accommodate the misorientation. Such dislocations are shown to exist in a wide range of grain boundaries. The wide spread in grain boundary structure and the complexity of the microstructure, making parallel current path considerations necessary, can account qualitatively for the deviation from the ideal Maxwell dispersive behaviour. However, a physically relevant interpretation of equivalent circuit parameters determined from dispersive type measurements seems not justified. Several model circuits are used to illustrate the interpretational difficulties. The structure and effects of intergranular phases also have been studied and are discussed.     

Low-angle tilt boundaries and inhomogeneous current densities in sodium beta alumina

Observation of [h k.0] low-angle tilt boundaries in sodium beta alumina is reported. The boundaries have a habit plane close to the (00.1) planes, and are evidence for the existence of dislocations with a Burgers vector component in the [00.1] direction. The indications are that these dislocations dissociate according toc ₀[00.1]1/2c ₀[00.1]+1/2c ₀[00.1].Such tilt boundaries can cause micro-inhomogeneities in sodium ion current flow and both enhancement and decrease of conduction plane current density seems possible.