The thermodynamics of collapsing molecular cloud cores using smoothed particle hydrodynamics with radiative transfer

We present the results of a series of calculations studying the collapse of molecular cloud cores performed using a three-dimensional smoothed particle hydr odynamics code with radiative transfer in the flux-limited diffusion approximation. The opacities and specific heat capacities are identical for each calculation. However, we find that the temperature evolution during the simulations varies significantly when starting from different initial conditions. Even spherically-symmetric clouds with different initial densities show markedly different development. We conclude that simple barotropic equations of state like those used in some previous calculations provide at best a crude approximation to the thermal behaviour of the gas. Radiative transfer is necessary to obtain accurate temperatures.Comment: 8 pages, 9 figures, accepted for publication in MNRA

The chronology of the Neolithic ditched settlements of the Tavoliere and the Ofanto valley

The chronology of the southeast Italian Neolithic may appear a rather over-worked subject, since there are several relatively recent treatments of various aspects (Alexander 2005; Skeates 2000; 2003), as well as a range of earlier articles (Pluciennik 1994; 1997; Sargent 1985; Skeates 1994; Whitehouse 1994: 86–90). It therefore may seem not to need additional attention now. Nonetheless, ‘rethinking’ – which is the avowed aim of the present volume – involves updating and adjusting of existing knowledge as well as iconoclasm and the opening up of new areas of research. In the case of chronology, new excavations are taking place, new radiocarbon dates are being published, Bayesian analysis is being introduced and there are several other issues that are worth further consideration. In the present volume, the paper by Keri Brown and Craig Alexander considers the chronology of the beginnings of the Neolithic in southeast Italy using Bayesian modelling, while Robin Skeates includes a discussion of the chronology of the later part of the period in his paper on Neolithic Italy at 4004 BC. My own contribution in this paper relates specifically to the dating of the so-called villaggi trincerati: the Neolithic ditched settlements characteristic of the Tavoliere plain of northern Puglia and the Ofanto valley that forms its southern border (Fig. 1)

Toni Morrison, Beloved, Race and Tragedy

This thesis investigates Toni Morrison’s engagement with tragedy in her novel Beloved. In opposition to late twentieth-century interpretations of Beloved, which see this novel as reordering or revisiting history in order to establish in its characters a sense of self-worth, this thesis understands Beloved as the narrative which calls a halt to the search for a worthy sense of self in a prescribed history. It argues that the form of this novel is designed and arranged in order to present in dramatic time a conception of a consciousness recognisable as already and always existing in African American individuals: that is, before, during and after slavery. This thesis contends that an engagement with tragedy is crucial in the achievement of this end. In an engagement with Morrison’s Nobel Lecture (1993), Chapter One argues that the significations of cultural authority are the result of a process in which negotiations of difference take place (Bhabha 2005). In a study of Morrison’s engagement with Du Bois’s (1897) theory of double consciousness, Chapter Two researches the complex nature of true fulfilment for the marginalized. Du Bois’s difficulty in establishing a simple claim to equality is contrasted with Morrison’s rejection of the discourses of difference, exclusion and marginalization (Morrison 1993). Chapter Three develops this line of enquiry to include Morrison’s adaption of ancient, tragic drama to the demands of African American writing. Morrison’s innovatory use of the separate and external configuration of human sensibilities in the form of Beloved is carefully considered in this chapter. Chapter Four engages with theories concerning the imposition of difference and the material conditions of appropriation, and the signifying system it spawns (Guillaumin 1995). It discusses Morrison’s aesthetic engagement with the master/slave relationship

A simplified model of the Martian atmosphere - Part 1: a diagnostic analysis

In this paper we derive a reduced-order approximation to the vertical and horizontal structure of a simplified model of the baroclinically unstable Martian atmosphere. The original model uses the full hydrostatic primitive equations on a sphere, but has only highly simplified schemes to represent the detailed physics of the Martian atmosphere, e.g. forcing towards a plausible zonal mean temperature state using Newtonian cooling. Three different norms are used to monitor energy conversion processes in the model and are then compared. When four vertical modes (the barotropic and first three baroclinic modes) are retained in the reduced-order approximation, the correlation norm captures approximately 90% of the variance, while the kinetic energy and total energy norms capture approximately 83% and 78% of the kinetic and total energy respectively. We show that the leading order Proper Orthogonal Decomposition (POD) modes represent the dominant travelling waves in the baroclinically-unstable, winter hemisphere. In part 2 of our study we will develop a hierarchy of truncated POD-Galerkin expansions of the model equations using up to four vertical modes

A simplified model of the Martian atmosphere - Part 2: a POD-Galerkin analysis

In Part I of this study Whitehouse et al. (2005) performed a diagnostic analysis of a simplied model of the Martian atmosphere, in which topography was absent and in which heating was modelled as Newtonian relaxation towards a zonally symmetric equilibrium temperature field. There we derived a reduced-order approximation to the vertical and the horizonal structure of the baroclinically unstable Martian atmosphere, retaining only the barotropic mode and the leading order baroclinic modes. Our objectives in Part II of the study are to incorporate these approximations into a Proper Orthogonal Decomposition-Galerkin expansion of the spherical quasi-geostrophic model in order to derive hierarchies of nonlinear ordinary differential equations for the time-varying coefficients of the spatial structures. Two different vertical truncations are considered, as well as three different norms and 3 different Galerkin truncations. We investigate each in turn, using tools from bifurcation theory, to determine which of the systems most closely resembles the data for which the original diagnostics were performed

FISH: A 3D parallel MHD code for astrophysical applications

FISH is a fast and simple ideal magneto-hydrodynamics code that scales to ~10 000 processes for a Cartesian computational domain of ~1000^3 cells. The simplicity of FISH has been achieved by the rigorous application of the operator splitting technique, while second order accuracy is maintained by the symmetric ordering of the operators. Between directional sweeps, the three-dimensional data is rotated in memory so that the sweep is always performed in a cache-efficient way along the direction of contiguous memory. Hence, the code only requires a one-dimensional description of the conservation equations to be solved. This approach also enable an elegant novel parallelisation of the code that is based on persistent communications with MPI for cubic domain decomposition on machines with distributed memory. This scheme is then combined with an additional OpenMP parallelisation of different sweeps that can take advantage of clusters of shared memory. We document the detailed implementation of a second order TVD advection scheme based on flux reconstruction. The magnetic fields are evolved by a constrained transport scheme. We show that the subtraction of a simple estimate of the hydrostatic gradient from the total gradients can significantly reduce the dissipation of the advection scheme in simulations of gravitationally bound hydrostatic objects. Through its simplicity and efficiency, FISH is as well-suited for hydrodynamics classes as for large-scale astrophysical simulations on high-performance computer clusters. In preparation for the release of a public version, we demonstrate the performance of FISH in a suite of astrophysically orientated test cases.Comment: 27 pages, 11 figure

Generation Solutions of Lynchburg (B)1

This case was developed to support classroom discussion of a market choice problem. Students are asked to make a recommendation on the market areas that a small entrepreneurial organization should enter next. Tabular data is provided to support demand estimation for selected geographic areas

Investigation of mixed element hybrid grid-based CFD methods for rotorcraft flow analysis

Accurate first-principles flow prediction is essential to the design and development of rotorcraft, and while current numerical analysis tools can, in theory, model the complete flow field, in practice the accuracy of these tools is limited by various inherent numerical deficiencies. An approach that combines the first-principles physical modeling capability of CFD schemes with the vortex preservation capabilities of Lagrangian vortex methods has been developed recently that controls the numerical diffusion of the rotor wake in a grid-based solver by employing a vorticity-velocity, rather than primitive variable, formulation. Coupling strategies, including variable exchange protocols are evaluated using several unstructured, structured, and Cartesian-grid Reynolds Averaged Navier-Stokes (RANS)/Euler CFD solvers. Results obtained with the hybrid grid-based solvers illustrate the capability of this hybrid method to resolve vortex-dominated flow fields with lower cell counts than pure RANS/Euler methods