Social information-processing patterns partially mediate the effect of early physical abuse on later conduct problems.

The authors tested the hypothesis that early physical abuse is associated with later externalizing behavior outcomes and that this relation is mediated by the intervening development of biased social information-processing patterns. They assessed 584 randomly selected boys and girls from European American and African American backgrounds for the lifetime experience of physical abuse through clinical interviews with mothers prior to the child's matriculation in kindergarten. Early abuse increased the risk of teacher-rated externalizing outcomes in Grades 3 and 4 by fourfold, and this effect could not be accounted for by confounded ecological or child factors. Abuse was associated with later processing patterns (encoding errors, hostile attributional biases, accessing of aggressive responses, and positive evaluations of aggression), which, in turn, predicted later externalizing outcomes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Modelling of degradation i n black copper photothermal collector coatings

The degradation mechanism in black copper photothermal collector coatings was investigated through the use of kinetic analysis, microstructural determinations and optical modelling. The initial structure of black copper was identified using reflection electron diffraction, scanning electron microscopy and Auger electron spectroscopy sputter profiles. These results were used to develop an optical model of the as-deposited coatings. In this model, the coatings was best described as a two-layer film. The layer next to the substrate consists of dense copper oxide with metallic copper inclusions, while the rough outer layer is modelled as copper oxide dispersed in air. A substantial decrease in the solar absorptance (from 0.96 to 0.80) of coatings exposed to temperatures above 150°C in air was found to occur within 30 min and was explained by a decrease in the surface roughness of the coatings. After longer exposures, an increase in the thickness of the oxide layer near the substrate occurs at the expense of the surface layer. Incorporating this change in the model, the optical properties after thermal ageing were predicted.     

PERFORMANCE OF ABSORPTION AND DISTILLATION COLUMNS IN A LUNAR ENVIRONMENT

The establishment of a permanent lunar base will employ separation processes that may be conducive to column operation. Reclamation of precious bodily fluids and products from chemical manufacture will be a part of routine necessity. The lunar environment, with reduced gravity and pressure, will offer some intriguing possibilities for operation such as vacuum distillation. The area for plate and packed columns will need to be increased in order to compensate for the reduction of gravitational forces responsible for moving the fluids. Plate efficiencies, hence column height, can increase or decrease, depending on the choice of scaling criteria applied to the plate geometry. Packed column height remains almost independent of gravity.     

Laser, fiber optic, and CCD array sensing systems

Lasers and fiber optics have recently been accepted in industry for sensing as well as for communications. Charge-coupled devices (CCD) and charge-injection devices (CID) are important new solid-state image sensors for fast display inputs to computers. The sensors may be coupled in a sensor fusion system by optical fibers to bring to the plant floor the advantages of intrinsic safety and immunity to radio frequency, electromagnetic, and optical noise. These new developments in sensing by lasers, fiber optics, and CCD arrays may be applied singly or in combination. For example, improved Raman spectroscopy employs a hostile environment fiber optic probe interface, an infrared laser diode to avoid fluorescence, and a CCD array detector for better sensitivity. We will examine recent developments that will help us with rapid, accurate real-time information for better monitoring and control.     

Accelerated cyclic oxidation testing protocols for thermal barrier coatings and alumina‐forming alloys and coatings

The oxide spallation resistance of oxide scales and ceramic thermal barrier coatings is a key design factor for developing high‐temperature alloy systems. Determination of the lifetimes of such alloy and coating systems is highly desirable. However, as improved systems are developed, lifetimes become so long that the time required to test a system to failure becomes prohibitive. Therefore, reliable protocols for accelerated testing and lifetime prediction are needed. This paper describes two attempts at developing such protocols. The first involves modification of the NASA COSP model to predict cyclic oxidation behavior of alloys and metallic coatings and the incorporation of acoustic emission data into this model. The second involves use of an indentation technique to induce spalling of thermal barrier coatings (TBCs) after short‐term thermal exposures. The first effort involves using the COSP Model, developed at NASA, as the basis for the prediction of oxide spallation. Acoustic emission measurements are used in an attempt to obtain critical parameters in the model from short‐time experiments for a variety of alloys and coatings which rely on alumina scales for oxidation resistance. The model is then used to predict the lives of these alloys and coatings when subjected to cyclic oxidation at 1100°C. A principal concern with ceramic thermal barrier coatings (TBCs) used in gas turbines is their loss of adhesion during service, leading to coating spallation. In this paper, an overview is given of an indentation test for brittle coatings on ductile substrates which is used to quantify decreases in interfacial toughness of TBC systems due to cyclic high‐temperature exposures. The indentation test involves penetration of the TBC and the oxide layer below it, inducing plastic straining in the underlying metal bond coat and superalloy substrate. The indentation strains cause an axisymmetric delamination of the TBC and oxide layers. Measurement of the extent of the delamination, coupled with finite‐element modeling, provides a measure of the adherence of the coating. Test results are presented tracking the loss of interfacial toughness for EBPVD TBC systems cyclically exposed at 1100°C.     

The development of protective borosilicate layers on a Mo-3Si-1B (weight percent) alloy

Molybdenum-based alloys with the addition of small amounts of silicon (2 to 4.5 wt pct) and boron (∼1 wt pct) can form a passivating layer that protects the alloy from further rapid oxidation. When such molybdenum-based alloys are exposed to oxidizing environments at high temperatures, a borosilicate glass layer can form that will reduce the transport of oxygen to the alloy to limit further oxidation. Oxidation is then controlled by diffusion through the borosilicate glass layer. The focus of this research was to study the development of the borosilicate layer on a Mo-3Si-1B (wt pct) alloy. The oxidation of this alloy was studied in a variety of gas environments over a range of temperatures in order to elucidate the critical factors that allow it to develop a protective borosilicate glass layer. The borosilicate glass layer is protective when no continuous channels exist in the layer extending from the gas interface to the alloy interface. The borosilicate layer is believed to contain channels in the early stages of development, and the elimination of the channels is obtained by appropriate control of the temperature and gas-flow conditions, whereby MoO₃ is removed via vaporization while the borosilicate viscosity is not increased due to loss of B₂O₃. Once the borosilicate layer is continuous and free of channels, subsequent oxidation occurs by inward diffusion of oxygen and outward diffusion of molybdenum through this layer, with vaporization of MoO₃ occurring at the gas/borosilicate-layer interface and MoO₂ and additional borosilicate forming at the alloy/MoO₂ interface.     

Factors affecting the microstructural stability and durability of thermal barrier coatings fabricated by air plasma spraying

The high‐temperature behavior of high‐purity, low‐density (HP‐LD) air plasma sprayed (APS) thermal barrier coatings (TBCs) with NiCoCrAlY bond coats deposited by argon‐shrouded plasma spraying is described. The high purity yttria‐stabilized zirconia resulted in top coats which are highly resistant to sintering and transformation from the metastable tetragonal phase to the equilibrium mixture of monoclinic and cubic phases. The thermal conductivity of the as‐processed TBC is low but increases during high temperature exposure even before densification occurs. The porous topcoat microstructure also resulted in good spallation resistance during thermal cycling. The actual failure mechanisms of the APS coatings were found to depend on topcoat thickness, topcoat density, and the thermal cycle frequency. The failure mechanisms are described and the durability of the HP‐LD coatings is compared with that of state‐of‐the‐art electron beam physical vapor deposition TBCs.