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Glassy carbon (GC) materials demonstrate excellent thermal stability and mechanical response with low mass densities, which makes them excellent candidates for use in ablatives and carbon-carbon composites (C/C composites) used in aerospace and hypersonic vehicle structures. Although GC materials have been in development and use for decades, molecular simulation protocols need to be developed to accelerate the optimization of processing cycles and to drive the development of the next generation of C/C composites. The objective of this research is to establish reactive molecular dynamics (MD) simulation protocols to accurately predict the evolution of the molecular structure and properties of furan resin during polymerization and pyrolysis processes. The polymerization simulation protocols have been validated via comparison of the predicted density and Young’s modulus of furan resin with experimental values. The MD pyrolysis simulations protocols are validated by comparison of calculated density, Young’s modulus, carbon content, sp2 carbon content, the in-plane crystallite size (La), out-of-plane crystallite stacking height (Lc), and inter-planar crystallite spacing (d002) with experimental results from the literature for furan resin derived GC. Simulation parameters, such as temperature and pressure, are optimized within relatively short simulation times (2000 ps), and the predicted structures and mechanical properties are shown to agree with experimental measurements. The modeling methodology established in this work can provide guidance for the development of next-generation C/C composite precursor chemistries for thermal protection systems and other high-temperature applications.

During the manufacturing of composite structures, cure shrinkage of the thermoset matrix and differential thermal contraction mismatch between the matrix and fiber reinforcement cause the formation of residual stresses, which can result in a loss in structural durability. New multiscale computational process modeling is essential for linking material chemistry, processing parameters, residual stress evolution, and optimizing mechanical performance. This study establishes a new multiscale process modeling method to accurately predict residual stresses in a unidirectional carbon fiber/epoxy composite using molecular dynamics and finite element analysis simulation techniques. The results of this work demonstrate that process-induced residual stresses have a significant impact on the composite strength in transverse tension, out-of-plane shear, and in-plane shear, with a maximum reduction in strength of 35%. Moving forward, this method can be used as a design and optimization tool for future composite structures for specific engineering applications and can provide processing parameters that can maximize desirable composite properties and/or minimize composite manufacturing energy and cost.

It is well-known that all-atom molecular dynamics (MD) predictions of mechanical properties of thermoset resins suffer from multiple accuracy issues associated with their viscous nature. The nanosecond simulation times of MD simulations do not allow for the direct simulation of the molecular conformational relaxations that occur under laboratory time scales. This adversely affects the prediction of mechanical properties at realistic strain rates, intermediate degrees of cure, and elevated temperatures. An efficient method of correcting such MD predictions of elastic properties is proposed and demonstrated. The phenomenological approach is used to map the predictions of Young's modulus and Poisson's ratio for a DGEBF/DETDA epoxy system to the corresponding laboratory-based properties for intermediate degrees of cure and temperatures above and below the glass transition temperature. The approach uses characterization data from dynamical mechanical analysis temperature sweep experiments. The mathematical formulation and experimental characterization of the mapping are described, and the resulting corrections to the predicted elastic properties for various degrees of cure and temperatures are compared with the experiment. This mapping is particularly important to mitigate the strain-rate effect associated with MD predictions, as well as to accurately predict mechanical properties at elevated temperatures and intermediate degrees of cure to facilitate accurate and efficient composite material process modeling.

It is well-known that all-atom molecular dynamics (MD) predictions of mechanical properties of thermoset resins suffer from multiple accuracy issues associated with their viscous nature. The nanosecond simulation times of MD simulations do not allow for the direct simulation of the molecular conformational relaxations that occur under laboratory time scales. This adversely affects the prediction of mechanical properties at realistic strain rates, intermediate degrees of cure, and elevated temperatures. An efficient method of correcting such MD predictions of elastic properties is proposed and demonstrated. The phenomenological approach is used to correct the predictions of Young’s modulus and Poisson’s ratio for a DGEBF/DETDA epoxy system for intermediate degrees of cure and temperatures above and below the glass transition temperature. The approach uses characterization data from dynamical mechanical analysis temperature sweep experiments. The mathematical formulation and experimental characterization of the correction is described, and the resulting corrections to the predicted elastic properties for various degrees of cure and temperatures are compared with experiment. This correction is particularly important to mitigate the strain-rate effect associated with MD predictions, as well as to accurately correct predicted mechanical properties at elevated temperatures and intermediate degrees of cure to facilitate accurate and efficient composite material process modeling.

As the adage goes, a picture is worth a thousand words. Yet, anthropologists have not typically sought study‐participant drawings. Using a protocol in which a request for a drawing was embedded, this study captures the internal dynamics of three successful university‐based teams. Our questions followed a specific Describe–Draw–Explain sequence. All interviewees offered some novel element in their drawings (Draw step) beyond what they conveyed in their verbal descriptions (Describe step), while 85 percent of them again offered additional detail in the Explain step. The data also revealed stark and surprising cultural contrasts across teams, including one that was understood best as a network that could be activated upon demand. Gathering drawings is a fast yet valid and reliable method when the prescribed sequence of questions is followed. Another virtue of this approach is that the interviews can be conducted virtually, essential during the COVID‐19 era.

Background Analysis of comparative effectiveness uses different metrics to ensure that a new treatment is both effective and economical. However, there is a lack of financial frameworks to estimate the costs of introducing new technologies in medical and surgical education. Methods After conducting a literature review, we created and applied a framework ('REC') for the evaluation of three recent neurosurgery video modules aimed at medical students at Harvard Medical School. Results The most expensive component of these video-based education (VBE) modules was time cost. This cost was highly variable depending on the level of clinical seniority of the individuals involved in the video production process. Conclusion Application of the REC framework to the three modules showed highly variable time and monetary cost differences between the modules. Usage of the REC framework will enable educators to institute effective planning, efficiently use resources, and clearly define a minimal viable education product to achieve desired learning outcomes.

Ethiopia’s mass-scale subsidized housing delivery programme has driven the rapid expansion of middle-income, mid-rise settlements on the outskirts of Addis Ababa, requiring the provision of infrastructure to newly developed areas. In the case of the Kotari housing project, established sanitation systems were deemed inappropriate for the site, resulting in the deployment of novel technology, a Membrane Bioreactor (MBR). Such decentralised technologies contribute to the heterogenous infrastructure configurations which characterise Addis Ababa’s sanitation landscape, reflected not only in material configurations but also in how they are governed. In this paper, we use the concept of ‘infrastructure interfaces’ as an analytical device to identify the key material connection points in the system. Working across scales, we scrutinise the governance arrangements at these critical junctures: the household, the block, the condominium, and the city. Our analysis challenges established understandings of infrastructural heterogeneity driven by the private sector, either through financialized elite infrastructures or informal survivalist practices. In Kotari, the state is the driver and the target is the lower middle class. Centring the state in these infrastructure configurations provides nuance to our understanding of how heterogeneity emerges. Our methodological approach accounts for governance at various scales, providing fresh insights into the relationality of infrastructure, particularly the human/technology interface and infrastructural failures. The case shows the importance of transcending binary readings of infrastructure configurations, such as on/off grid, state/private and formal/informal. Future work on the post-network city must go beyond simply denigrating or valorising alternative modes of service delivery.

As part of the Natural Sciences and Engineering Research Council of Canada–Canada Mining Innovation Council (NSERC-CMIC) Mineral Exploration Footprints project, three selected magnetic inve...

This article discusses the phenomenon of personal inscriptions in manuscripts and printed books associated with the sisters of Syon Abbey (founded 1415), the sole English Birgittine house. It argues that personal inscriptions reveal the Syon sisters’ complex ownership-like relationships with their books, and that the sisters were able to demonstrate both their individual and communal devotional identity through their interaction with each other and their books. In the first section, the article defines ‘ownership’ in its legal context and discusses it in relationship to ‘use’. The second section closely reads the Syon legislative documents to discuss the sisters’ conceptualizations of book ownership within the bounds of their order. The third section discusses the practice of inscription, using evidence from extant Syon manuscripts and early printed books. The fourth section brings these contexts together to discuss two cases of hybrid book ownership: the functional ownership developed through repeated use of the Syon processionals, and the collective individual ownership of multiple copies of printed books. The article presents a new way of understanding inscriptions and their potential for community building and individuation at Syon Abbey and contributes to our understanding of women’s reading experiences and ownership practices in England at the turn of the sixteenth century and the late-medieval period as a whole.

This article represents a Full Paper. Students are often the beneficiaries of staff-led and managed programs where they acquire and hone professional development skills outside the classroom. Given the ongoing transformation toward a "whole new engineer" [1], we decided to focus on university staff and their involvement in improving student outcomes. The three teams profiled in this article were part of a larger set of 12 grassroots teams at a large, public U.S. university. We examine these three successful teams, all staff-led, two with six members and one with eight members. We were interested in how team members conceptualized their individual roles and their professional networks in helping their teams accomplish their goals. The data, illustrated through their statements and drawings, enable us to capture and explain their insider perspectives on these collaborations, the strategies they employed to overcome issues, the value they placed on divergent team-member views, and the factors they believed to be essential for success.

This case study explores the data management practices of medieval manuscript scholars working on the Digital Tools for Manuscript Study project at the University of Toronto. We chose this user gro...

Cochlear implants are neuroprosthetic devices that provide hearing to deaf patients, although outcomes are highly variable even with prolonged training and use. The central auditory system must process cochlear implant signals, but it is unclear how neural circuits adapt—or fail to adapt—to such inputs. The knowledge of these mechanisms is required for development of next-generation neuroprosthetics that interface with existing neural circuits and enable synaptic plasticity to improve perceptual outcomes. Here, we describe a new system for cochlear implant insertion, stimulation, and behavioral training in rats. Animals were first ensured to have significant hearing loss via physiological and behavioral criteria. We developed a surgical approach for multichannel (2- or 8-channel) array insertion, comparable with implantation procedures and depth in humans. Peripheral and cortical responses to stimulation were used to program the implant objectively. Animals fitted with implants learned to use them for an auditory-dependent task that assesses frequency detection and recognition in a background of environmentally and self-generated noise and ceased responding appropriately to sounds when the implant was temporarily inactivated. This physiologically calibrated and behaviorally validated system provides a powerful opportunity to study the neural basis of neuroprosthetic device use and plasticity.

Infrastructure convenes social relations, thereby revealing how city dwellers access shared resources in the context of growing inequality. Our exploration of migrant infrastructure engages with how highly variegated migrant groups develop a ‘transaction economy’ (Simone, 2004) within marginalised city streets, exchanging goods and services, and information and care. In the context of ethnically diverse and deprived urban places, where state resources are increasingly diminished, we explore how a precarious yet skilled resourcefulness emerges through the street. Our empirical exploration of migrant infrastructure is located on Rookery Road in Birmingham and on Narborough Road in Leicester, and draws on qualitative surveys with 195 self-employed proprietors from many countries of origin. The streets reveal transaction economies that intersect local and migratory resources, eluding the categorisation of cities associated with either a global North or a global South. Further, the lively nature of street transactions decentres western-centric measures of economic value. From the street, we develop a postcolonial analysis of infrastructure that relates properties of historic depth (power), socio-spatial texture (materiality) and locality (place).

California frequently experiences water scarcity, especially in high population areas. This has generated increased interest in using the Pacific Ocean as a water resource, with seawater desalination becoming a popular solution. To mitigate the environmental impacts of the high salinity brine from seawater desalination, California recommends commingling brine with wastewater effluent before ocean discharge. Results reveal that throughout the California coast, approximately 4872 MLD (1287 MGD) of treated wastewater are discharged into the ocean and might be available as dilution water. Most of this dilution water resource is produced in Southern California (3161 MLD or 835 MGD) and the San Francisco Bay Area (1503 MLD or 397 MGD), which are also the areas with the highest need for alternative water sources. With this quantity of dilution water, in principle, over 5300 MLD (1400 MGD) of potable water could be produced in California through seawater desalination. Furthermore, this study provides a survey of the treatment levels and typical discharge violations of ocean wastewater treatment facilities in California.

Although gold in high-sulfidation epithermal deposits generally occurs as the native metal or electrum, in some deposits, a significant proportion of the gold is hosted in pyrite. Here we use a combination of petrography, whole-rock geochemistry, pyrite chemistry, crystallography, and phase stability relationships to determine how gold was transported and incorporated into pyrite in two relatively young high-sulfidation epithermal deposits, where the gold occurs almost exclusively in solid solution or as nanoparticles in pyrite. The genetically related Bawone and Binebase Au (Cu-Ag) deposits, located 1 km apart on the volcanic island of Sangihe, northeastern Indonesia, are hosted by andesitic volcaniclastic rocks that were altered to a proximal advanced argillic association of quartz + pyrite (py I) + pyrophyllite + natroalunite + alunite + dickite + kaolinite and a more distal intermediate argillic association of quartz + pyrite (py I) + kaolinite + dickite + illite. The economic mineralization takes the form of multiple generations of auriferous pyrite, the first of which, pyrite I (py I), developed during advanced argillic alteration. Mass balance calculations show that all elements were mobile with the exception of Nb, Ti, some rare earth elements, and possibly Al. The highest gold concentration is in pyrite II (py II), which occurs in veins that cut pyrite I. This drusy variety of pyrite is characterized by complex growth and sector zoning, and contains as much as 6.0 wt % Cu. The elevated Cu concentrations correlate positively with Au and As concentrations, whereas the Ag concentration correlates strongly with Au but not Cu. Later barite-enargite mineralization exploited py II veins and vugs, and significant concentrations of Ag and Au are hosted by enargite, although the Au concentration in enargite is lower than in py II or py I. A model is presented in which the fluid responsible for advanced argillic and intermediate argillic alteration and associated stage 1 gold mineralization was a condensed magmatic vapor derived from an oxidized magma. The gold and other metals were transported as hydrated species that ascended through the volcanic pile via fractures and zones of enhanced permeability to a depth between 900 and 1300 m, where the vapor condensed at a temperature between 250 and 340°C to form an acidic liquid with a pH of ~2.5; f o2 ranged up to four log units above the hematite-magnetite buffer. Interaction of this liquid with the host andesites caused advanced argillic and intermediate argillic alteration, including sulfidation of mafic minerals to form py I. During crystallization of py I, Au, Cu and Ag were adsorbed onto the surface of the pyrite and deposited as nanoparticles, or were incorporated in the pyrite structure. Adsorption of Au, Cu, and Ag from the condensed vapor reached a peak during the crystallization of vein-hosted py II, and the uptake of Ag and minor Au continued during later crystallization of enargite. From the distribution of metals among growth and sector zones in py II, incorporation of gold and other metals appears to have been maximized when physicochemical conditions were relatively stable. This is in contrast to the requirement for native gold precipitation, namely that physicochemical gradients be steep to ensure supersaturation of gold in the ore fluid.

The study examined how preschool intervention programmes set up by three Scottish local authorities changed parents’ cognitions. Quantitative parent outcomes were measured using Parenting Daily Hassles Scales (N = 88). A matched comparison group of parents (N = 55) recruited from the same areas of disadvantage but whose children did not attend the intervention programmes also completed questionnaires. Qualitative outcomes were evaluated using semi‐structured interviews (N = 30). A significant group × time interaction effect was found for daily hassle cognitions, Parenting Task–Intensity, Challenging Behaviour–Frequency and Challenging Behaviour–Intensity, with comparison group parents showing an increase in their experience of hassles during the ‘terrible twos’ compared with intervention group parents. Complementary qualitative data indicated that intervention group parents had gained valuable new insights into their children’s behaviour, changing how they thought about their role as parents and their beh...

To determine age and sex-specific pediatric reference intervals for serum alpha fetoprotein, homocysteine, insulin, insulin-like growth factor-I, insulin-like growth factor binding protein-3, C-peptide, immunoglobulin E and parathyroid hormone.The study was conducted at both Children's National Medical Center and Georgetown University, Washington D.C. Results for the above analytes were obtained from the Children's National Medical Center laboratory information system over the period of 1/5/2001-3/8/2007. Patient results using the IMMULITE 2000(R) were accessed and used to establish reference intervals for the analytes studied. All patient identifiers were removed except age and sex. Analysis of the data was performed at Georgetown University in the Bioanalytical Core Laboratory. The data was analyzed using the Hoffmann approach, and was computer adapted. The number of patient samples studied varied with each analyte and were: Alpha fetoprotein (557), homocysteine (924), insulin-like growth factor-1 (1352), insulin-like growth factor binding protein-3 (711), insulin (3239), C-peptide (267), immunoglobulin E (2691) and parathyroid hormone (513).This study provides pediatric reference intervals for the eight analytes for children from birth to 18 years of age. All the analytes exhibited at least some age dependence. Sex differences between early and late childhood and adolescence were also frequently found.

What do animals hear? While it remains challenging to adequately assess sensory perception in animal models, it is important to determine perceptual abilities in model systems to understand how physiological processes and plasticity relate to perception, learning, and cognition. Here we discuss hearing in rodents, reviewing previous and recent behavioral experiments querying acoustic perception in rats and mice, and examining the relation between behavioral data and electrophysiological recordings from the central auditory system. We focus on measurements of critical bands, which are psychoacoustic phenomena that seem to have a neural basis in the functional organization of the cochlea and the inferior colliculus. We then discuss how behavioral training, brain stimulation, and neuropathology impact auditory processing and perception.

Fatigue crack growth in high strength aluminium alloy 7150 commercial plate material has been studied in both laboratory air and acidified aqueous salt solution. The aggressive aqueous environment enhanced fatigue crack growth rates by up to an order in magnitude compared to laboratory air. The enhancement in fatigue crack growth rate was accompanied by evidence of embrittlement in the crack path, involving both brittle intergranular and transgranular failure modes. Both the enhancement of fatigue crack growth rates and the extent of intergranular growth modes are dependent on cyclic frequency which, along with the absence of a similar frequency effect in a spray-formed version of the material with a significantly different grain structure, supports a mechanism of grain boundary hydrogen diffusion for intergranular corrosion fatigue crack growth. The convergence of corrosion fatigue crack growth rates at high ΔK in both spray-formed and conventional plate materials coincides with the operation of identical transgranular corrosion fatigue modes dependent on strain-controlled hydrogen diffusion ahead of the crack tip. © 1997 Acta Metallurgica Inc.

The purpose of this study was to identify the vocabulary use patterns of 65- to 74-year-old and 75- to 85-year-old adults. Communication samples of routine conversations were collected from 10 individuals (5 men and 5 women) for each age cohort using voice-activated portable audiotape recorders. Analysis for frequency and commonality of word use was completed using custom computer software and are reported in extensive appendices.

Tensile tests were carried out using specimens of 2009 aluminium alloy reinforced by either SiC whiskers or particles. The size distributions of the whiskers and particles in the matrix were obtained by image analysis. It was found that failure was a result of uniform void nucleation and coalescence in the as fabricated composites, or a result of fast crack propagation initiated by a flaw developed at clusters of SiC in the aged or stretched and aged composites. The strengths of the as fabricated composites were estimated based on the results of image analysis using continuum mechanics and dislocation theories. The estimation indicated that the tensile strengths are largely contributed to by composite strengthening, supplemented by residual dislocation strengthening and work hardening. Owing to the flaw controlled failure, the tensile strengths of the aged or stretched and aged composites were independent of aging time, aging temperature, and the amount of stretching. The elastic moduli of the composites were estimated using the Halpin-Tsai model and a good correlation was found between the measured and estimated moduli. © 1996 The Institute of Materials.

In part I of this article, cleavage initiation in the intercritically reheated coarse-grained heat affected zone (IC CG HAZ) of high-strength low-alloy (HSLA) steels was determined to occur between two closely spaced blocky MA particles. Blunt notch, crack tip opening displacement (CTOD), and precracked Charpy testing were used in this investigation to determine the failure criteria required for cleavage initiation to occur by this mechanism in the IC CG HAZ. It was found that the attainment of a critical level of strain was required in addition to a critical level of stress. This does not occur in the case of high strain rate testing, for example, during precracked Charpy testing. A different cleavage initiation mechanism is then found to operate. The precise fracture criteria and microstructural requirements (described in part I of this article) result in competition between potential cleavage initiation mechanisms in the IC CG HAZ.

This paper compares the crack growth resistance of an experimental spray-formed extrusion with that of a commercial aluminium alloy, the two alloys having similar compositions but markedly different grain structures. Tensile and fracture behaviour is similar in both materials and is influenced by inclusion content. The two materials differ in their crack growth resistance, which is shown to be dependent upon grain size and shape. Environmentally-induced crack growth is favoured by aligned grain boundaries and small grain size.

Knoop and Vickers indentation cracks have frequently been used as model 'precracks' in ceramic bend specimens for fracture toughness (K1c) determination. Indentation residual stress reduces the measured K1c but can be removed or accounted for by grinding, annealing, or modelling. Values of K1c are obtained for four materials using Vickers indentations and an improved stress intensity factor. Methods for residual stress removal or incorporation are compared, and the most reliable stress removal alternative is identified for each material. © 1996 The Institute of Materials.

The isothermal fatigue behavior of a high-activity aluminide-coated single-crystal superalloy was studied in air at test temperatures of 600 °C, 800 °C, and 1000 °C. Tests were performed using cylindrical specimens under strain control at ∼0.25 Hz; total strain ranges from 0.5 to 1.6 pet were investigated. At 600 °C, crack initiation occurred at brittle coating cracks, which led to a significant reduction in fatigue life compared to the uncoated alloy. Fatigue cracks grew from the brittle coating cracks initially in a stage II manner with a subsequent transition to crystallographic stage I fatigue. At 800 °C and 1000 °C, the coating failed quickly by a fatigue process due to the drastic reduction in strength above 750 °C, the ductile-brittle transition temperature. These cracks were arrested or slowed by oxidation at the coating-substrate interface and only led to a detriment in life relative to the uncoated material for total strain ranges of 1.2 pet and above 800 °C. The presence of the coating was beneficial at 800 °C for total strain rangesless than 1.2 pet. No effect of the coating was observed at 1000 °C. Crack growth in the substrate at 800 °C was similar to 600 °C; at 1000 °C, greater plasticity and oxidationrwere observed and cracks grew exclusively in a stage II manner.

Static mechanical properties of 2124 Al/SiCp MMC have been measured as a function of solution temperature and time. An optimum solution treatment has been established which produces significant improvements in static mechanical properties and fatigue crack growth resistance over conventional solution treatments. Increasing the solution treatment parameters up to the optimum values improves the mechanical properties because of intermetallic dissolution, improved solute and GPB zone strengthening and increased matrix dislocation density. Increasing the solution treatment parameters beyond the optimum values results in a rapid reduction in mechanical properties due to the formation of gas porosity and surface blisters. The optimum solution treatment improves tensile properties in the transverse orientation to a greater extent than in the longitudinal orientation and this results in reduced anisotropy. © 1996 Elsevier Science Limited.

The effects of a thermal residual stress field on fatigue crack growth in a silicon carbide particle-reinforced aluminum alloy have been measured. Stress fields were introduced into plates of material by means of a quench from a solution heat-treatment temperature. Measurements using neutron diffraction have shown that this introduces an approximately parabolic stress field into the plates, varying from compressive at the surfaces to tensile in the center. Long fatigue cracks were grown in specimens cut from as-quenched plates and in specimens which were given a stress-relieving overaging heat treatment prior to testing. Crack closure levels for these cracks were determined as a function of the position of the crack tip in the residual stress field, and these are shown to differ between as-quenched and stress-relieved samples. By monitoring the compliance of the specimens during fatigue cycling, the degree to which the residual stresses close the crack has been evaluated.

The nature of subsurface cracks formed under and around Vickers hardness indentations is often assumed rather than identified. Subsurface cracks in four engineering ceramics are revealed using a penetrant technique, and flaw dimensions are recorded. The resulting data are used to investigate several aspects of indentation cracking, such as crack shape, functional relationships between indentation load and flaw dimensions, and the performance of indentation fracture toughness equations. An R curve is constructed for each of the materials. © 1995 The Institute of Materials.

Interfaces in conventional monolithic alloys exert an important influence on fatigue and fracture behavior. In discontinuously reinforced metal matrix composites (MMCs), the role of interface is even more dominant. The interfacial is higher in MMCs and the interfaces are generally of high energy and chemically unstable. This paper reviews the factors which can affect interfacial strength in discontinuously reinforced MMCs, and the ways in which interfacial strength can be controlled. The effects of interfacial strength on fatigue crack propagation and fracture behavior are then illustrated.

Pack aluminide coating is a useful method for conferring oxidation resistance on nickel-base superalloys. Nominally, these coatings have a matrix composed of a Ni-Al based B2-type phase (commonly denoted as Β). However, following high-temperature exposure in oxidative envi-ronments, aluminum is depleted from the coating. Aluminum depletion in turn, leads to de-stabilization of the Β phase, resulting in the formation of a characteristic lathlike Β-derivative microstructure. This article presents a transmission electron microscopy study of the formation of the lathlike Β-derivative microstructure using bulk nickel aluminides as model alloys. In the bulk nickel aluminides, the lathlike microstructure has been found to correspond to two distinct components: L10-type martensite and a new Β derivative. The new Β derivative is characterized and the conditions associated with the presence of this feature are identified and compared with those leading to the formation of the L10 martensitic phase.

This study investigated adults' rate preferences when listening to synthetic speech. Twenty younger and 20 older adults listened to phonemically balanced sentences generated by MultiVoice™ (DECtalk™) and presented at randomized rates between 120 to 250 words per minute (wpm). Participants rated their listening comfort on a 7-point Likert-type scale. Analysis revealed a significant quadratic trend between comfort rating and speech rate. Most comfortable rates ranged from 150 to 200 wpm for both age groups; differences between the groups occurred at both ends of the rate continuum. The findings provide guidelines for selecting synthetic speech presentation rates when interacting with AAC users and communication partners of different ages.

Engineering ceramics are often difficult to prepare metallographically because of their hardness, wear resistance and chemical inertness. Two silicon carbides, a silicon nitride and a sialon, are prepared and etched using several different techniques. The most efficient methods are identified. © 1995.

Anecdotally, expert adult augmentative and alternative communication (AAC) users have stated the importance of small talk in successful interactions. Small talk includes those utterances used in any environment that serve a social function but do not contain specific cognitive or communicative content. AAC systems are increasingly being designed to efficiently manage (store and retrieve) small talk messages to allow users of AAC technology to participate in social conversations more effectively. This study sought to determine the frequency and form of small talk used by adults in three age cohorts (20 to 30, 65 to 74, and 75 to 84 years). Approximately one-third of all communicative utterances for each age group was classified as small talk, with 50% to 60% of those utterances being unique, that is not used more than once. The average small talk utterance was between two and three words in length for all age groups. Similarities and differences between the three age groups, as well as examples of small ta...

This chapter explores the potential for electric vehicles to contribute to decarbonising surface transport. Decarbonising transport is a major global challenge—meeting CO2 emissions reduction targets for 2050, with a rapidly growing, and urbanising global population.

Fatigue crack initiation and propagation in duplex stainless steels are strongly affected by microstructure in both inert and aggressive environments. Fatigue crack growth rates in wrought Zeron 100 duplex stainless steel in air were found to vary with orientation depending on the frequency of crack tip retardation at ferrite/austenite grain boundaries. Fatigue crack propagation rates in 3.5% NaCl solution and high purity water are increased by hydrogen assisted transgranular cyclic cleavage of the ferrite. The corrosion fatigue results are interpreted using a model for the cyclic cleavage mechanism.

Fatigue crack growth under Mode I loading, and static fracture in both symmetrical and asymmetrical notched four point bend specimens, have been examined in SiC whisker reinforced 2009 aluminium alloy. In the fatigue tests a range of orientations of the starter notch, with respect to the extrusion direction, L, was examined. Slanted crack propagation was observed in all specimens except that in the T-L configuration. For the monotonic tests the specimen orientation (L-T) remained constant whilst the ratio of Mode I to Mode II loading was varied. Again crack deflection was observed in all cases apart from the L-T specimen under pure Mode I loading. Whisker debonding was found to be the dominant factor controlling crack deflection, independent of the mixity of the loading mode. Under mixed-mode static loading, the deflection angle was controlled by the average orientation of the whiskers subject to the asymmetrically distributed maximum principal stress. In fatigue loading, however, the crack tended to follow the most frequently observed whisker orientation. These contrasting observations are interpreted in terms of the different sampling volumes at the crack tip in monotonic fracture and in fatigue crack growth.

While many studies have been devoted to the microstructure/property relationship during aging of MMCs, few studies have been made of this relationship during quenching. Both Al alloys and Al matrix MMCs exhibit quench sensitivity i.e. a change in as-quenched properties and precipitation behavior with cooling rate, although the sensitivity differs between alloy systems. Papazian showed, using DSC analysis, that the quench sensitivity of discontinuously reinforced MMCs was increased over that of unreinforced alloys, for a range of matrix alloys. The least sensitive alloys were affected most when reinforcement was added. This could have important consequences regarding the heat treatment of MMCs, in that the quench parameters may have to be more tightly controlled than for unreinforced alloys in order to ensure consistent as-quenched properties. The current study investigates the effect of cooling rate on the as-quenched hardness and subsequent aging behavior of a powder metallurgy (PM) 2124 Al alloy and 2124 Al/SiC[sub p] MMC. Extensive use has been made of data available in the literature. Throughout this paper the term quench sensitivity'' refers to the magnitude of the change in as-quenched properties with cooling rate.