A recent development for the numerical modelling of material discontinuities is presented in this thesis. The concepts considered here are founded on the idea that for each physical variable (e.g. temperature, enthalpy, etc.) there exists an associated non-physical variable. The numerical technique presented here that utilises non-physical variables is called the non-physical finite element method (NPFEM). The NPFEM involves the replacement of a discontinuous physical field with a limiting-continuous non-physical field (i.e. abstract mathematical object) which is continuous over the domain but has a source-like behaviour at the place of a discontinuity. Non-physical variables are rigorously defined in the thesis and are related to their physical counterparts by means of transport equations. As a consequence of the coupling of physical and non-physical variables, equivalent forms of transport equations arise. However, as a consequence of limiting continuity the adopted approach permits the representation of non-physical variables by means of a polynomial basis standard to the continuous Galerkin finite element method (CGFEM).The non-physical method was originally devised for the modelling of material discontinuities in solidification problems involving a strong discontinuity in enthalpy and a weak discontinuity in temperature. The work presented here extends previous works by providing a general framework for the non-physical method to facilitate modelling of strong material discontinuities in all the state variables along with velocity arising with material discontinuities. The approach is founded on the integral transport form of the governing conservation laws. The advantage of the non-physical methodology is that it permits the precise annihilation of discontinuous behaviour in the governing finite element equations by means of a distribution like source term at the discontinuity location. Different case studies of single and multiple stationary and transient 1-D shock waves in fluids and solids are undertaken to show the accuracy, flexibility and robustness of the non-physical finite element method. Also presented as part of the work is a newly developed analytical model for the 1-D high velocity crushing of the cellular bars.

Phase change in solidification and melting can be described with the aid of discontinuous functions. The aim of this project is to establish effective methodologies for the solution of discontinuous phase-change problems. The classic capacitance method, which distributes the effect of any discontinuity present over a finite region (typically an element), can suffer from inaccurate energy transport. Improvement is possible with the application of the classic non-physical enthalpy method. However, this approach is known to suffer with the imposition of material velocity, which gives rise to negative thermal capacitance providing a source of error and instability. In order to improve on the performance of the capacitance method and the classic non-physical enthalpy method, this research introduces a series of new non-physical variables. Firstly, a new non-physical enthalpy is defined via the weak form of the energy transport equation. The classical non-physical enthalpy was defined using a temporal integral term. In the new definition, the non-physical enthalpy involves both a temporal and an advection term, which is shown to avoid the generation of negative capacitance and improve the stability of advection heat transfer in numerical methods. Secondly, control volume analysis is performed on weighted and unweighted forms of the governing energy equation involving non-physical enthalpy. The analysis is shown to reveal non-physical source terms that facilitate the removal of phase-change discontinuities. Thirdly, it is demonstrated in the thesis how a non-physical heat source must be introduced into the governing non-physical transport equation to remove discontinuities arising from non-physical terms related to advection. To demonstrate the accuracy and stability of the new method, it is implemented in the finite element method for both one-dimensional linear rod elements and two dimensional triangular elements. Update techniques and root finding methods, such as the predictor-corrector method, the secant method and the homotopy method, are applied to solve the non-linear system of equations, which are constructed with the new theory. Results returned from the one-dimensional numerical experiments are compared with exact solutions, which show reasonable accuracy. Numerical experiments for isothermal solidification with advection-diffusion in both one and two dimensions demonstrate the feasibility of the new methodology.

Masters of Art / The writing of history in postapartheid South Africa constitutes a crisis for the discipline of history as, I argue, it requires the discipline to confront its role in contributing towards the constitution of the condition of possibility of the discourse of apartheid. Stated differently, the relationship between the discipline of history and nationalist or identity politics, a relationship that is characterized by history performing the role of alibi, is highlighted as problematic within the question of the postapartheid. It is in this context that I want to broach the concept of the historical playas an antidisciplinary object that works to unsettle the discipline of history and thereby its role as alibi. Such an engagement with the historical play would, I argue, enable a progressive politics of the sort that Michel Foucault calls for. In his essay 'History, Discourse and Discontinuity' (1972) which he wrote in response to a question posed to him of the possibility of resistance within the corpus of his work, Foucault argues that a progressive politics would be one that takes into account a discourse's conditions of possibility - one that limits the claims of discourses on life through defining their grammars, as it were." While this current study does not seek to, and also does not claim to, subject the discourse of history to such a critique (I am not proposing to investigate the emergence of the discipline), Foucault's understanding of a progressive politics is especially significant to it. Particularly, rather than reading for the grammar of history - this has been done by others such as (but not limited to) Gayatri Spivak, Hayden White and Friederich Nietzsche and will be discussed later - this dissertation starts from the position that the discipline of history played (and plays) a fundamental role in establishing the conditions of possibility of the discourse of apartheid." This is not to argue that apartheid can be reduced to an outworking of nationalist history (apartheid as a discursive field).

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Interpreting soil wetness in upland transported soils on flat broad summits in the central Piedmont of Virginia containing chroma ≥ 3 redoximorphic features (RMFs) can be difficult. It is imperative to understand their saturation regimes because onsite wastewater disposal systems, which are sited based upon soil evaluations, have failed prematurely when installed into these problematic soils. My objectives were to determine if soil morphology was an accurate predictor of soil wetness and permeability, to differentiate interpretations for colluvial soils from residual soils, and to determine the effect of canopy cover on seasonal wetness. Soil morphology, soil wetness regimes in open and wooded canopies, and in-situ saturated hydraulic conductivity were documented in transported Appomattox, Bentley, Brockroad, Catharpin, and Dothan and residual Clifford, Minnieville, and Penhook soil series at eight sites. Transported soils had average winter water levels, and met 30-day and 20-day NRCS oxyaquic criteria at 81, 66, and 91 cm, respectively. Transported soils with depleted ped faces, Fe- concentrations, and chroma 3 depletions were saturated an average of 41, 23, and 41% of the winter, respectively. Residuum found ≥ 1.5 m beneath transported soils exhibited little saturation, thus confirming epiaquic conditions. Residual soils did not perch water for extended periods; and were saturated for significantly (p<0.001) shorter durations and shallower depths (average 93 and 82 cm for 30-day and 20-day oxyaquic criteria, respectively). Transported soils under clear cuts had significantly (p<0.001) shallower average water levels (79 cm) and 30-day and 20-day oxyaquic conditions (51 and 88 cm, respectively) than wooded locations (87 and 83 cm average water levels and 30-day oxyaquic water table, respectively). In-situ hydraulic testing confirmed the presence of low permeability layers as determined by soil evaluation. Restrictive layers were thicker and less permeable in transported soils than in residual soils. In summary, water perches seasonally for extended periods over thick impermeable layers in transported soils. A recommended best management practice for problematic transported soils would be to not install septic systems in zones of saturation and low permeability, including the 1.5 m below a discontinuity. Drainfield designs should utilize permeable saprolite beneath transported material and an upslope curtain drain. / Ph. D.

Yes / Cross-sectional and longitudinal studies have consistently reported an association between education and myopia. However, conventional observational studies are at risk of bias due to confounding by factors such as socioeconomic position and parental educational attainment. The current study aimed to estimate the causal effect of education on refractive error using regression discontinuity analysis. Methods: Regression discontinuity analysis was applied to assess the influence on refractive error of the raising of the school leaving age (ROSLA) from 15 to 16 years introduced in England and Wales in 1972. For comparison, a conventional ordinary least squares (OLS) analysis was performed. The analysis sample comprised 21,548 UK Biobank participants born in a nine-year interval centered on September 1957, the date of birth of those first affected by ROSLA. Results: In OLS analysis, the ROSLA 1972 reform was associated with a −0.29 D (95% confidence interval [CI]: −0.36 to −0.21, P < 0.001) more negative refractive error. In other words, the refractive error of the study sample became more negative by −0.29 D during the transition from a minimum school leaving age of 15 to 16 years of age. Regression discontinuity analysis estimated the causal effect of the ROSLA 1972 reform on refractive error as −0.77 D (95% CI: −1.53 to −0.02, P = 0.04). Conclusions: Additional compulsory schooling due to the ROSLA 1972 reform was associated with a more negative refractive error, providing additional support for a causal relationship between education and myopia. / Global Education program of the Russian Federation government (DP) and an NIHR Senior Research Fellowship award SRF-2015-08-005 (CW), The Department for Health through an award made by the NIHR to the Biomedical Research Centre at Moorfields Eye Hospital NHS Foundation Trust, and UCL Institute of Ophthalmology, London, United Kingdom (grant no. BRC2_009). Additional support was provided by The Special Trustees of Moorfields Eye Hospital, London, United Kingdom (grant no. ST 12 09)

The foundations of democracy is a very popular subject in our time period because there are many states seeking to establish democratic governments but are unsure of what exactly a democratic government is or how to build one. A democracy does not spring out of the ground overnight; it takes many years of painstakingly slow evolution in the direction of democracy. The main push for democracy comes from the people themselves by means of a gradual expansion of rights. The point of this study is to discover underlying determinants of a strong democracy. For this study, three states will be looked at. The three states are Bulgaria, Poland and the Czech Republic, and they are vital components to understanding the patterns of democratic development in Eastern Europe. Although as a whole the states within this region share many traits, there are sub-regional differences setting them apart that affect their chances of creating democracy. Of the three cases the Czech Republic stands out as the most likely to establish a viable democracy, and part of that has to do with its geographic proximity to Western Europe. Because the Czechs have always been closer to Western Europe they have imbibed more successful practices.

Denna uppsats studerar hur de tillfälliga uppehållstillstånden påverkar nyanländas incitament att ta sig in på den svenska arbetsmarknaden. En av motiveringarna bakom den tillfälliga lagen var – förutom att ge svenskt flyktingmottagande ett andrum – att ge nyanlända personer starkare drivkrafter att komma in på arbetsmarknaden. För att undersöka detta görs en brytpunktsanalys (Regression Discontinuity design) där individer som registrerat sin asylansökan hos Migrationsverket före och efter den 24 november 2015 jämförs. Detta datum avgör om barn och barnfamiljer behandlas enligt den gamla eller den tillfälliga lagen, och därmed om de har möjlighet att få permanenta eller tillfälliga uppehållstillstånd. Resultaten visar att individer på olika sidor om datumgränsen inte verkar skilja sig åt i förutbestämda variabler, vilket tyder på att de inte har haft möjlighet att bestämma vilken sida av datumgränsen de hamnat på. Individer som passerat gränsen har signifikant lägre sannolikhet att få permanenta uppehållstillstånd, minskningen är dock marginell. Det beror troligen på att uppföljningsperioden är kort. Som indikation på hur incitamenten att komma in på arbetsmarknaden påverkas av reformen studeras invandrartäthet samt arbetslöshetsnivå i de län som sökande bor i ett år efter ankomsten. Resultaten tyder på att individer som fick sin ansökan registrerad efter brytpunkten inte bor i län där invandrartätheten eller arbetslösheten är annorlunda. Även detta kan bero på att det än så länge gått för kort tid för att kunna se några effekter. / This paper studies how the temporary residence permits affects immigrants’ incentives to enter the Swedish labor market. One of the reasons behind the adoption of the temporary permits was – in addition to provide Swedish refugee reception a relief – to give immigrants stronger incentives to enter the labor market. To study this, a Regression Discontinuity design study is done, where individuals who had their asylum application registered at the Swedish Migration Agency before and after November 24, 2015 are compared. This date will determine if children and families are treated by the old or the temporary law, and thus if they can get permanent or temporary residence permit.   The results show that individuals on different sides of the dateline do not seem to differ in predetermined variables, suggesting that they have not been able to decide which side of the dateline they are on. Individuals who crossed the threshold are significantly less likely to have permanent residence permits, the decrease is however marginal. This is probably because the follow-up period is short. As an indication of how the incentives to enter the labor market are affected by the reform, immigrant density and unemployment rate in the county that the applicant lives in a year after the arrival is used. The results suggest that individuals who registered their applications after the threshold does not live in counties with a different immigrant density or unemployment rate. This as well can be due to that the follow-up period is short.

Since 1997, fully noncontributory minimum pensions have been established in many Latin American countries, and have more recently been encouraged as a "zero pillar" of social security by the World Bank and other IFIs. These policies came into being under diverse political regimes and display a range of levels of generosity and universality. Becuase these policies are generally part of a modern bureaucratic welfare state project, they require identity documents, something that many low-income citizens do not possess. States have lowered barriers to the supply of identity documents, and new social policies, like noncontributory pensions and conditional or unconditional cash transfers, have stimulated demand for identity documents among those who do not currently have them. Brazils noncontributory pension, the BPC, has a means test and a large benefit (equivalent to the minimum wage), but requires providing identity documents for all household members. This report discusses the propagation of noncontributory pensions, then examines Brazilian government records to determine the size of the incentive to demand documents in Brazil using a logit model and a more novel survival time regression discontinuity design, raising questions of the relationships between benefit size, universality, document requirements, and poverty. / text

Two separate problems are to be investigated in this thesis. The first problem is the propagation of waves through a short rod (or slug) of viscoelastic material. The second problem is the study of impact of a short viscoelastic rod (or slug) on a stationary semi-infinite viscoelastic. rod. The viscoelastic materials are modelled as standard linear solids which involve 3 material parameters and the motion is treated. as one-dimensional. For the first study, a viscoelastic slug is placed between two semi-infinite elastic rods and a wave initiated in the first rod is transmitted through the slug into the second rod. The objective is to relate the transmitted signal to the material parameters of the slug. We solve the governing system of partial differential equations using the Laplace transform and we examine the propagating velocity discontinuity using discontinuity analysis and the limit theorem of the Laplace transform. We then approximate the solution of the propagating disturbance using the regular perturbation method. We invert the Laplace transformed solution numerically to obtain the transmitted signal for several viscosity time constants and ratios of acoustic impedances. We compare the results obtained using the above techniques. In the second problem, we first model the impact and solve the governing system of partial differential equations in the Laplace transform domain. Then we examine the propagating stress and velocity discontinuities using discontinuity analysis. We approximate the solutions of the propagating stress and velocity using the regular and multiple scales perturbation methods. In this problem, we first consider the slug is elastic and the rod is viscoelastic. Secondly, we consider the slug is viscoelastic and the rod is elastic and thirdly, we consider both materials are viscoelastic. Numerically we invert the Laplace transformed solutions for the interface stress and interface velocity for several viscosity time constants and ratios of acoustic impedances to determine whether the slug and the rod part company or remain in contact. Then we compare the results obtained using the discontinuity analysis, regular and multiple scales perturbation methods.