Interfacial strength development in thermoplastic resins and fiber-reinforced thermoplastic composites

An experimental program to develop test methods to be used to characterize interfacial (autohesive) strength development in polysulfone thermoplastic resin and graphite-polysulfone prepreg during processing is reported. Two test methods were used to examine interfacial strength development in neat resin samples. These included an interfacial tension test and a compact tension (CT) fracture toughness test. The interfacial tensile test proved to be very difficult to perform with a considerable amount of data scatter. Thus, the interfacial test was discarded in favor of the fracture toughness test. Interfacial strength development was observed by measuring the refracture toughness of precracked compact tension specimens that were rehealed at a given temperature and contact time. The measured refracture toughness was correlated with temperature and contact time. Interfacial strength development in graphite-polysulfone unidirectional composites was measured using a double cantilever beam (DCB) interlaminar fracture toughness test. The critical strain energy release rate of refractured composite specimens was measured as a function of healing temperature and contact time

Magnetic fluctuation power near proton temperature anisotropy instability thresholds in the solar wind

The proton temperature anisotropy in the solar wind is known to be constrained by the theoretical thresholds for pressure anisotropy-driven instabilities. Here we use approximately 1 million independent measurements of gyroscale magnetic fluctuations in the solar wind to show for the first time that these fluctuations are enhanced along the temperature anisotropy thresholds of the mirror, proton oblique firehose, and ion cyclotron instabilities. In addition, the measured magnetic compressibility is enhanced at high plasma beta ($\beta_\parallel \gtrsim 1$) along the mirror instability threshold but small elsewhere, consistent with expectations of the mirror mode. The power in this frequency (the 'dissipation') range is often considered to be driven by the solar wind turbulent cascade, an interpretation which should be qualified in light of the present results. In particular, we show that the short wavelength magnetic fluctuation power is a strong function of collisionality, which relaxes the temperature anisotropy away from the instability conditions and reduces correspondingly the fluctuation power.Comment: 4 pages, 4 figure

Polarized Neutron Matter: A Lowest Order Constrained Variational Approach

In this paper, we calculate some of the polarized neutron matter properties, using the lowest order constrained variational method with the $AV_{18}$ potential and employing a microscopic point of view. A comparison is also made between our results and those of other many-body techniques.Comment: 23 pages, 8 figure

Using Synthetic Spacecraft Data to Interpret Compressible Fluctuations in Solar Wind Turbulence

Kinetic plasma theory is used to generate synthetic spacecraft data to analyze and interpret the compressible fluctuations in the inertial range of solar wind turbulence. The kinetic counterparts of the three familiar linear MHD wave modes---the fast, Alfven, and slow waves---are identified and the properties of the density-parallel magnetic field correlation for these kinetic wave modes is presented. The construction of synthetic spacecraft data, based on the quasi-linear premise---that some characteristics of magnetized plasma turbulence can be usefully modeled as a collection of randomly phased, linear wave modes---is described in detail. Theoretical predictions of the density-parallel magnetic field correlation based on MHD and Vlasov-Maxwell linear eigenfunctions are presented and compared to the observational determination of this correlation based on 10 years of Wind spacecraft data. It is demonstrated that MHD theory is inadequate to describe the compressible turbulent fluctuations and that the observed density-parallel magnetic field correlation is consistent with a statistically negligible kinetic fast wave energy contribution for the large sample used in this study. A model of the solar wind inertial range fluctuations is proposed comprised of a mixture of a critically balanced distribution of incompressible Alfvenic fluctuations and a critically balanced or more anisotropic than critical balance distribution of compressible slow wave fluctuations. These results imply that there is little or no transfer of large scale turbulent energy through the inertial range down to whistler waves at small scales.Comment: Accepted to Astrophysical Journal. 28 pages, 7 figure

Nonformal education for sustainable development: A Bangladeshi perspective

Sustainable development means ‘development that meets the needs of the present without compromising the ability of future generations to meet their needs’ (WCED, 1987:43). Meanwhile, any education worth the name is a life-long process for the betterment of human well-being. The social purposes of education are located in the long term, and it is right therefore that education should be oriented towards the construction and maintenance of a sustainable future. However, many children in developing countries get very little education. They have little chance to attend even low-quality primary schools, and dropout and failure rates are alarming; many leave semi-literate, soon to relapse into illiteracy, with disastrous consequences for their participation as individuals in the creation of a sustainable world. Moreover, the majority of those who are at school experience a traditional, formal education paradigm, aimed primarily at selecting and building human capital for economic growth. This paradigm is seen to be increasingly at odds with the concept of education for sustainability. Since the 1960s, nonformal education has comprised a wide spectrum of educational and training activities organised outside the formal school system. Innovative learning methods are aimed at the development of practical skills, including matters of health, sanitation, literacy, to be applied in real life situations. As an alternative approach to basic education, the nonformal sector as a whole thus increases pressure for change in the wider education system. Drawing on a three-year empirical study of young people at the point of transition between the nonformal and formal sectors of schooling in Bangladesh, this paper will develop a framework for analysing how the nonformal education paradigm could usefully and realistically increase practice for sustainability in the formal system

Imagining inclusive teachers: contesting policy assumptions in relation to the development of inclusive practice in schools

In this paper we reflect on data from two research projects in which inclusive practice in schools is at issue, in the light of wider field experience (our own and others’) of school and teacher development. We question what we understand to be relatively common, implicit policy assumptions about how teachers develop, by examining the way in which teachers are portrayed and located in these projects. The examples discussed in this paper draw on experience in Lao PDR and Bangladesh, critically exploring teachers’ roles, position and agency in practice. Similarities and differences rooted in cultural, political and institutional contexts highlight in a very productive way the significance and potential dangers of policy assumptions about teachers within the process of development. In Bangladesh, a success story is presented: the case of a group of schools in which an institutional context for learning appears to sustain teachers’ commitment and motivation, with the effect of creating meaningful outcomes for young people who were previously outside the education system. These data raise questions about the significance of institutional context to teachers’ practices, and questions about approaches to teacher development which omit consideration of that context by, for example, focusing inadvertently on features of individual teachers. We then consider teachers’ responses to the movement for inclusive education in a school in the Lao PDR since 2004. Inclusion here was understood to require a significant shift in teacher identity and a movement away from authoritative pedagogy towards the facilitation of a pedagogy which aimed to encourage the active participation of all students. Through a longitudinal study of teachers in one school, the conditions for such change were identified and again cast doubt on some of the assumptions behind large-scale attempts at teacher development. Reflecting on these experiences and the evidence they provide, we suggest that teacher development programmes are more likely to be effective where teachers are considered not as individuals subject to training but as agents located in an influential institutional context

Linguistic Indicators of Severity and Progress in Online Text-based Therapy for Depression

Mental illnesses such as depression andanxiety are highly prevalent, and therapyis increasingly being offered online. Thisnew setting is a departure from face-to-face therapy, and offers both a challengeand an opportunity – it is not yet knownwhat features or approaches are likely tolead to successful outcomes in such a dif-ferent medium, but online text-based ther-apy provides large amounts of data for lin-guistic analysis. We present an initial in-vestigation into the application of compu-tational linguistic techniques, such as topicand sentiment modelling, to online ther-apy for depression and anxiety. We findthat important measures such as symptomseverity can be predicted with compara-ble accuracy to face-to-face data, usinggeneral features such as discussion topicand sentiment; however, measures of pa-tient progress are captured only by finer-grained lexical features, suggesting thataspects of style or dialogue structure mayalso be important

Kinetic Scale Density Fluctuations in the Solar Wind

We motivate the importance of studying kinetic scale turbulence for understanding the macroscopic properties of the heliosphere, such as the heating of the solar wind. We then discuss the technique by which kinetic scale density fluctuations can be measured using the spacecraft potential, including a calculation of the timescale for the spacecraft potential to react to the density changes. Finally, we compare the shape of the density spectrum at ion scales to theoretical predictions based on a cascade model for kinetic turbulence. We conclude that the shape of the spectrum, including the ion scale flattening, can be captured by the sum of passive density fluctuations at large scales and kinetic Alfven wave turbulence at small scales