Effect of Surface Preparation Methods on Mechanical Properties of 3D Structures Fabricated by Stereolithography and 3D Printing for Electroless Ni Plating

Stereolithography (SL) and 3D Printing (3DP) are useful technologies for three-dimensional prototyping applications, providing highly accurate and detailed part geometries with high quality surface finishes. It is desired to improve the materials performance of the existing photocurable SL and 3DP resins for rapid tooling and other functional applications by applying a nickel (Ni) coating. In this work, surface preparation methods for electroless plating of commercial photopolymer resins such as NanoFormTM15120 (NanoForm) and Objet FullCure®840 (Veroblue) were explored in order to enhance the structural integrity of RP components. This study examined different surface preparation methods (chemical etching) and their effect on the surface morphology and mechanical strength of the polymers. It was observed that surface preparation of the resins significantly affected the mechanical properties and Ni plating of the substrate polymers. This is a critical step, since the Ni film takes on the surface structure of the substrate.Mechanical Engineerin

In Fear We Trust: Anxious Political Rhetoric & the Politics of Punishment, 1960s-80s

Senior Project submitted to The Division of Social Studies of Bard College

Broad Band X-ray Spectra of M31 Sources with BeppoSAX

We present the first spectral study of the X-ray emitting stellar sources in M31 in the energy band from 0.1 to 10 keV. We find that the globular cluster sources have spectral characteristics consistent with those of the Milky Way object, namely that the spectrum can be described by a thermal model with 6-20 keV from 2 to 10 keV. Evidence of high absorption in some of these sources is most likely an indication that they lie in or behind the HI ring in the disk of the galaxy. We also find one peculiar globular cluster source, with spectral characteristics more typically associated with either High Mass X-ray Binaries or black hole candidates. We therefore suggest that either the source has been wrongly identified with a globular cluster or that the system contains a Black Hole. We confirm earlier report that the spectrum of the bulge of M31 is consistent with the superposition of many LMXB spectra. It is likely that a large fraction of the 15-30 keV detection obtained from the PDS instrument is associated with the bulge, thus extending the spectral data for this complex of sources up to 30 keV. The high energy part of the spectrum can be parameterized with typical LMXB spectra, while at low energies an additional component is required.Comment: Accepted for publication in A&A, main journa

Dynamiser l’enseignement de l’écrit dans les classes à effectifs pléthoriques dans les lycées du Ghana : les avis des enseignants du FLE dans la métropole de Cape Coast

Les exigences socio-économiques mondiales du 21 siècle éveillent plusieurs gouvernements à l’obligation de promouvoir l’accès à l’éducation de leurs citoyens, le Ghana ne fait pas exception. Parfois, les efforts dans ce domaine ne viennent pas sans des coûts ou des inconvénients surtout à la mise en œuvre des politiques du gouvernement. Cette étude a recensé et analysé les avis des enseignants concernant la gestion des classes à effectifs pléthoriques lors de la production écrite. L’étude repose sur l’hypothèse que le grand nombre d’étudiants dans les salles de classe est du au respect du lycée gratuit introduit par le gouvernement actuel. Les questionnaires, les guides d’observation et d’entrevue ont été utilisés pour la collecte des données auprès de 22 enseignants et leurs étudiants dans les dix lycées publics dans la métropole de Cape Coast. Les analyses ont été faite de manière quantitative et qualitative pour confirmer l’hypothèse. L’étude a révélé qu’à cause du nombre élevé d’étudiants en classe de FLE, il y a le manque de suivi individuel par les enseignants ; le devoir de groupe devient le plus préféré et la correction des travaux scolaires individuels est affaiblie. Il y a une révision des activités pédagogiques résultant aux retombées négatives sur l’écrit des étudiants. Les propositions, issues des avis envisagées par les enquêtés, sont les suivantes : motivation des enseignants au niveau des matériels pédagogiques, enrichissement des activités de groupe en classe par les enseignants et, en long terme, recrutement des enseignants et amélioration des infrastructures scolaires. The global socio-economic demands of the 21st century have prompted many governments to promote their citizens’ access to education, and Ghana is no exception. Sometimes, efforts in achieving these objectives do not come without costs or inconveniences, especially in the implementation of government policies. This study gathered and analyzed various views of French teachers about managing large class sizes during the teaching of written expression. The study was based on the hypothesis that the resurgence of the large class sizes was due to the introduction of free Senior High School policy by government without corresponding adequate infrastructure. Questionnaires, interview, and observation guides were used to collect data from 22 teachers and students in ten public schools in the Cape Coast Metropolis. Quantitative and qualitative approaches were used to analyze the data which confirmed the hypothesis. The study revealed that due to the large number of students in the FLE class, there is lack of individual attention given to students, most of the teachers were left with the choice of group works during lessons, and the correction of individual school work is weakened. Revisions of pedagogical activities led to a decrease in the output of students in their written expressions. Recommendations which are based on the opinions envisaged by the respondents focus on the following: motivation of teachers in terms of teaching/learning materials and enrichment of group activities in the classroom. As an imminent measure, there should be recruitment of teachers and improvement of school infrastructure

Bayesian models of syntactic category acquisition

Discovering a word’s part of speech is an essential step in acquiring the grammar of a language. In this thesis we examine a variety of computational Bayesian models that use linguistic input available to children, in the form of transcribed child directed speech, to learn part of speech categories. Part of speech categories are characterised by contextual (distributional/syntactic) and word-internal (morphological) similarity. In this thesis, we assume language learners will be aware of these types of cues, and investigate exactly how they can make use of them. Firstly, we enrich the context of a standard model (the Bayesian Hidden Markov Model) by adding sentence type to the wider distributional context.We show that children are exposed to a much more diverse set of sentence types than evident in standard corpora used for NLP tasks, and previous work suggests that they are aware of the differences between sentence type as signalled by prosody and pragmatics. Sentence type affects local context distributions, and as such can be informative when relying on local context for categorisation. Adding sentence types to the model improves performance, depending on how it is integrated into our models. We discuss how to incorporate novel features into the model structure we use in a flexible manner, and present a second model type that learns to use sentence type as a distinguishing cue only when it is informative. Secondly, we add a model of morphological segmentation to the part of speech categorisation model, in order to model joint learning of syntactic categories and morphology. These two tasks are closely linked: categorising words into syntactic categories is aided by morphological information, and finding morphological patterns in words is aided by knowing the syntactic categories of those words. In our joint model, we find improved performance vis-a-vis single-task baselines, but the nature of the improvement depends on the morphological typology of the language being modelled. This is the first token-based joint model of unsupervised morphology and part of speech category learning of which we are aware