Adaptive finite elements for viscoelastic deformation problems

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.This thesis is concerned with the theoretical and computational aspects of generating solutions to problems involving materials with fading memory, known as viscoelastic materials. Viscoelastic materials can be loosely described as those whose current stress configuration depends on their recent past. Viscoelastic constitutive laws for stress typically take the form of a sum of an instantaneous response term and an integral over their past responses. Such laws are called hereditary integral constitutive laws. The main purpose of this study is to analyse adaptive finite element algorithms for the numerical solution of the quasistatic equations governing the small displacement of a viscoelastic body subjected to prescribed body forces and tractions. Such algorithms for the hereditary integral formulation have appeared in the literature. However the approach here is to consider an equivalent formulation based on the introduction of a set of unobservable interval variables. In the linear viscoelastic case we exploit the structure of the quasistatic problem to remove the displacement from the equations governing the internal variables. This results in an elliptic problem with right hand side dependent on the internal variables, and a separate independent system of ordinary differential equations in a Hilbert space. We consider a continuous in space and time Galerkin finite element approximation to the reformulated problem for which we derive optimal order a priori error estimates. We then apply the techniques of the theory of adaptive finite element methods for elliptic boundary value problems and ordinary differential equations, deriving reliable and efficient a posteriori error estimates and detailing adaptive algorithms. We consider the idea of splitting the error into space and time portions and present results regarding a splitting for space time projections. The ideas for splitting the error in projections is applied to the finite element approximation and a further set of a posteriori error estimates derived. Numerical studies confirm the theoretical properties of all of the estimators and we show how they can be used to drive adaptive in space and time solution algorithms. We consider the extension of our results for the linear case to the constitutively nonlinear case. A model problem is formulated and the general techniques for dealing with a posterior error estimation for nonlinear space time problems are considered.EPSRC; Japanese Society for the Promotion of Science(JSPS

Alien Registration- Hill, Harry (Holden, Penobscot County)

https://digitalmaine.com/alien_docs/8130/thumbnail.jp

L’implacable rythme : Edgar Allan Poe et la pédagogie

Faire pénétrer les étudiants du baccalauréat dans le rythme et la structure phonétique de la nouvelle « The Fall of the House of Usher », c'est éveiller leur sensibilité aux aspects rhétoriques de la communication écrite. Pour cette raison, cet objectif est plus important, à court et à long terme, que des considérations purement psychologiques ou thématiques. Cet essai, qui utilise l'imagination auditive du lecteur, le fait pénétrer dans les mécanismes de l'écriture à l'oeuvre dans la première page de la nouvelle d'Edgar Allan Poe, afin d'illustrer son principal but, qui est d'instruire par le plaisir.To instill in undergraduates a facility with rhythm and phonetic structure as found in "The Fall of The House Of Usher" is to awaken a central feeling for the rhetorical patterns of written communication, and as such is immediately and in the long run more important than considerations of a merely psychological and thematic kind. This paper takes the reader, using the auditory imagination, into the workings of the opening paragraph of the work as illustration of its principal argument, which is that of instruction through delight

Alien Registration- Hill, Harry L. (Houlton, Aroostook County)

https://digitalmaine.com/alien_docs/34575/thumbnail.jp

Space environmental effects on LDEF composites: A leading edge coated graphite epoxy panel

The electronics module cover for the leading edge (Row D 9) experiment M0003-8 was fabricated from T300 graphite/934 epoxy unidirectional prepreg tape in a (O(sub 2), +/- 45, O(sub 2), +/- 45, 90, 0)(sub s) layup. This 11.75 in x 16.75 in panel was covered with thermal control coatings in three of the four quadrants with the fourth quadrant uncoated. The composite panel experienced different thermal cycling extremes in each quadrant due to the different optical properties of the coatings and bare composite. The panel also experienced ultraviolet (UV) and atomic oxygen (AO) attack as well as micrometeoroid and space debris impacts. An AO reactivity of 0.99 x 10(exp -24) cm(sup 3)/atom was calculated for the bare composite based on thickness loss. The white urethane thermal control coatings (A276 and BMS 1060) prevented AO attack of the composite substrate. However, the black urethane thermal control coating (Z306) was severely eroded by AO, allowing some AO attack of the composite substrate. An interesting banding pattern on the AO eroded bare composite surface was investigated and found to match the dimensions of the graphite fiber tow widths as prepregged. Also, erosion depths were greater in the darker bands. Five micrometeoroid/space debris impacts were cross sectioned to investigate possible structural damage as well as impact/AO interactions. Local crushing and delaminations were found to some extent in all of the impacts. No signs of coating undercutting were observed despite the extensive AO erosion patterns seen in the exposed composite material at the impact sites. An extensive microcrack study was performed on the panel along with modeling of the thermal environment to estimate temperature extremes and thermal shock. The white coated composite substrate displayed almost no microcracking while the black coated and bare composite showed extensive microcracking. Significant AO erosion was seen in many of the cracks in the bare composite

Identifying barriers to sustainable food production by low resource producers and purchase by low income consumers in Washington and Beaufort Counties, North Carolina

Serving the interests of our client, Resourceful Communities of the Conservation Fund, our project investigates ways to better connect low-resource producers and low-income consumers of fresh produce in 31 low-income counties in NE North Carolina. To better characterize barriers rural producers and consumers face to produce and access healthy food, we conducted three separate analyses. A general linear model statistical analysis based on the USDA Food Environment Atlas data was used to identify significant demographic and socioeconomic variables that affect food access at the macro-level. For a qualitative analysis, surveys and interviews were used to define barriers producers and consumers face on the intra-county scale. Using Geographic Information Systems, a spatial analysis was developed to understand spatial patterns of food deserts and access barriers. The qualitative and spatial analyses were focused on two low-income counties: Beaufort County and Washington County, NC Community stakeholders, local food producers, consumers, and grocery retailers were interviewed. The statistical analysis focused both on 31 target North Carolina counties and on the entire Eastern Coastal plain. Two general linear models revealed that persistent poverty counties and counties experiencing population loss were more likely to experience little or no access to grocery stores. Race was also a factor, particularly within North Carolina where minorities are more vulnerable to food insecurity. Both Washington and Beaufort Counties exhibit a high level of economic and demographic stratification. Two-thirds of consumers from the survey had problems stretching their food budget, and identified a weekly food box at low or no-cost as the best intervention. Retail grocery stores already can and do buy local food. However, retailers buy locally according to the season and price. Major barriers to connecting low-resource producers and low-income consumers were identified as the decrease in the number of small farms, increasing bureaucracy, high cost of entry, and historical divisions between ethnic and socioeconomic groups. Using the geographic and socio-economic barriers, the spatial analysis identified three food deserts, in SE Beaufort County, NE Beaufort County, and SW Washington County and the main drivers for each

Active Carboxylic Acid-Terminated Alkanethiol Self-Assembled Monolayers on Gold Bead Electrodes for Immobilization of Cytochromes c

It is extremely difficult to immobilize cytochrome c (cyt c) on carboxylic acid-terminated alkanethiol self-assembled monolayers (HOOC-SAM) on gold bead electrodes prepared in a hydrogen flame. We found that simple pretreatment of a HOOC-SAM/gold bead electrode by potential cycling in buffer solution in the range ±300 mV prior to immobilization of the protein facilitated stable cyt c binding to HOOC-SAMs. The stability of cyt c on the HOOC-SAMs is independent of the topology of the gold surface

Achieving 100% pass rate and NSS feedback for a module: How we did it

Assessment exercises a major influence on student learning and achievement (Boud 2007). Yet QAA reviews and pedagogic literature identify assessment practices as one of the weakest features of Higher Education (Rust et al. 2005). In terms of the student learning experience the feedback process following assessment is the least satisfactory element. This is exemplified in consistently low satisfaction scores for assessment and feedback in National Student Surveys (NSS), where most concern surrounds the timeliness, quality and effectiveness of feedback. The research presented here is based on the premise that feedback should occupy a central position within a dialogic approach to learning, teaching and assessment (Alexander 2004). We adopt a qualitative case study approach, undertaking semi-structured interviews with students from two consecutive cohorts who have undertaken dialogic feed-forward coursework on a second year undergraduate physical geography module at UWE. The assessment consists of submitting a considered draft of a coursework essay, which is discussed and evaluated face-to-face with the course tutor before a self-reflective piece is written about the assessment process and a final essay is submitted for formal grading. Using thematic analysis of transcripts we explore student perspectives of the assessment process. We test the social constructivist theory that if academic staff and students discuss feedback together students might negotiate meaning and learn to actively reflect upon feedback, developing their capacity to translate key content and ‘feeding forward’ this learning (Brown 2007; Nicol 2010). We present evidence that this process asserts a positive influence on the student learning experience in a number of inter-related cognitive and affective ways, in supporting student performance/achievement, and in enhancing NSS and TEF metrics related to feedback (Higgins et al. 2001, Sutton 2009). We finish by presenting a model of good practice for dialogic feed-forward assessment that can guide both module and programme planning and delivery