A Second Order Godunov Method for Multidimensional Relativistic Magnetohydrodynamics

We describe a new Godunov algorithm for relativistic magnetohydrodynamics (RMHD) that combines a simple, unsplit second order accurate integrator with the constrained transport (CT) method for enforcing the solenoidal constraint on the magnetic field. A variety of approximate Riemann solvers are implemented to compute the fluxes of the conserved variables. The methods are tested with a comprehensive suite of multidimensional problems. These tests have helped us develop a hierarchy of correction steps that are applied when the integration algorithm predicts unphysical states due to errors in the fluxes, or errors in the inversion between conserved and primitive variables. Although used exceedingly rarely, these corrections dramatically improve the stability of the algorithm. We present preliminary results from the application of these algorithms to two problems in RMHD: the propagation of supersonic magnetized jets, and the amplification of magnetic field by turbulence driven by the relativistic Kelvin-Helmholtz instability (KHI). Both of these applications reveal important differences between the results computed with Riemann solvers that adopt different approximations for the fluxes. For example, we show that use of Riemann solvers which include both contact and rotational discontinuities can increase the strength of the magnetic field within the cocoon by a factor of ten in simulations of RMHD jets, and can increase the spectral resolution of three-dimensional RMHD turbulence driven by the KHI by a factor of 2. This increase in accuracy far outweighs the associated increase in computational cost. Our RMHD scheme is publicly available as part of the Athena code.Comment: 75 pages, 28 figures, accepted for publication in ApJS. Version with high resolution figures available from http://jila.colorado.edu/~krb3u/Athena_SR/rmhd_method_paper.pd

Post-graduate education, training and extension at Central Marine Fisheries Research Institute, Cochin

In view of the increasing demand for trained personnel to meet the requirements of mariculture and brackishwater culture activities in the country, the Central Marine Fisheries Research Institute took steps to institute a post-graduate education programme In mariculture at the institute, leading to the M.Sc. and Ph.D. degrees awarded by the Cochin University of Science and Technology. Through this programme a number of post-graduates have been turned out in the subject during the past seven years. The students were given both theoretical and practical instructions in different aspects of mariculture including basic subjects like physiology, nutrition, genetics and pathology. The Scientists of the Institute constitute the faculty for the programme and a number of members of the faculty have also been trained abroad in different specialisations. The Programme also had the advantage of consultants from other countries who have contributed greatly to its improvement and also in the development of Infrastructural facilities at the Institute. As a result of the consultancy, a number of manuals on special subjects have also been published. The Krishi Vigyan Kendra and the Trainers' Training Centre handle a number of courses at the farmers level and at the trainers level based on the technologies developed at the Institute. In addition, an integrated programme of training including subjects in agriculture, animal husbandry and home management is also conducted

γ2˘7\gamma\u27-Realizability and Other Musings on Inverse Domination

We introduce and study $\gamma\u27$-realizable sequences. For a finite, simple graph $G$ containing no isolated vertices, $I \subseteq V(G)$ is said to be an \emph{inverse dominating set} if $I$ dominates all of $G$ and $I$ is contained by the complement of some minimum dominating set $D$. Define a sequence of positive integers $(x_1, \ldots , x_n)$ to be \emph{$\gamma\u27$-realizable} if there exists a graph $G$ having exactly $n$ distinct minimum dominating sets $D_1, \ldots, D_n$ where for each $i \in \{1, \ldots, n\}$, the minimum size of an inverse dominating set in $V(G) \setminus D_i$ is equal to $x_i$. In this work, we show which sequences having minimum entry 2 or less are $\gamma\u27$-realizable. We then detail a few observations and results arising during our investigations that may prove useful in future research

An Integrated Systems Approach to the Development of Winter Maintenance / Management Systems

Winter road maintenance operations require many complex strategic and operational planning decisions. The five primary problems involved in this intricate planning procedure include locating depots, designing sectors, routing service vehicles, scheduling vehicles, and configuring the vehicle fleet. The complexity involved in each of these decisions has resulted mainly in research that approaches each of the problems separately and sequentially, which can lead to isolated and suboptimal solutions. After discussing the complexity of the relaxed subproblems that would need to be solved to optimize the intricate winter maintenance operations, the research turns to a heuristic approach to more feasibly address the interrelated problems. This report subsequently presents a systematic, heuristic-based optimization approach to integrate the winter road maintenance planning decisions for depot location, sector design, vehicle route design, vehicle scheduling, and fleet configuration. The approach presented is illustrated through an example of public sector winter road maintenance planning for a rural transportation network in Boone County, Missouri. When applied to the real-world winter road maintenance planning problems for Boone County, the methodology delivered very promising results. The solution methodology successfully achieves the objective of a more integrated and less sequential approach to the problems considered. The integrated solution would allow the Missouri Department of Transportation (MoDOT) to maintain the same high level of service with significantly fewer resources. The results indicate that this methodology is a successful step towards solving realistic multiple-depot problems involving heterogeneous winter maintenance fleets

Numerical and Experimental Investigation of Joule Heating in a Carbon Fibre Powder Epoxy Towpregging Line

Powder epoxy based towpregs offer favourable processing and storage properties, thanks to the low viscosity and thermal stability of the powder epoxy. Low-cost, high-quality towpregs, which are suitable for automated fibre placement or filament winding applications, can be produced at a high production rate with an automated towpregging line. This study focuses on improving the towpregging process by analysing the heating charac-teristics of a towpregging line that employs Joule heating to impregnate carbon fibre tows with powder epoxy. A finite element analysis heat transfer model was developed to identify the relationship between processing pa-rameters and heating of the carbon fibre tows. Model predictions matched well with experimental results. Using the temperature distribution predicted by the model, powder epoxy melting and sintering behaviour was investigated using semi-empirical equations. Results revealed that Joule heating provides efficient heating with very low power consumption. It was found that while it is possible to produce towpregs at high production speeds (15 m/min), slower speeds might yield more consistent quality. Using parametric studies in the model, it was shown that it is possible to increase towpregging line production rate without compromising the towpreg quality, by altering some of the key process parameters (supplied current, electrode distance etc.)

Detection of a Substantial Molecular Gas Reservoir in a brightest cluster galaxy at z = 1.7

We report the detection of CO(2-1) emission coincident with the brightest cluster galaxy (BCG) of the high-redshift galaxy cluster SpARCS1049+56, with the Redshift Search Receiver (RSR) on the Large Millimetre Telescope (LMT). We confirm a spectroscopic redshift for the gas of z = 1.7091+/-0.0004, which is consistent with the systemic redshift of the cluster galaxies of z = 1.709. The line is well-fit by a single component Gaussian with a RSR resolution-corrected FWHM of 569+/-63 km/s. We see no evidence for multiple velocity components in the gas, as might be expected from the multiple image components seen in near-infrared imaging with the Hubble Space Telescope. We measure the integrated flux of the line to be 3.6+/-0.3 Jy km/s and, using alpha_CO = 0.8 Msun (K km s^-1 pc^2)^-1 we estimate a total molecular gas mass of 1.1+/-0.1x10^11 Msun and a M_H2/M_star ~ 0.4. This is the largest gas reservoir detected in a BCG above z > 1 to date. Given the infrared-estimated star formation rate of 860+/-130 Msun/yr, this corresponds to a gas depletion timescale of ~0.1Gyr. We discuss several possible mechanisms for depositing such a large gas reservoir to the cluster center -- e.g., a cooling flow, a major galaxy-galaxy merger or the stripping of gas from several galaxies -- but conclude that these LMT data are not sufficient to differentiate between them.Comment: accepted for publication in ApJ Letter

Contact Resistance Heating of Unidirectional Carbon Fibre Tows in a Powder-Epoxy Towpregging Line

Contact resistances play a major role in Joule heating systems. Identifying contact resistances provides a better understanding of the heating process and increases the accuracy of the process models. In this study, contact resistances of the Joule heating section in a powder-epoxy-based towpregging line were explored. For different process parameters, such as production speed, tension, and temperature, contact resistances occurring between metal roller electrodes and dry carbon fibre tows (i.e. without powder-epoxy) were measured to gain an insight into the heating process. Moreover, the effect of contact resistance heating on the temperature profile of the carbon fibre tows was determined with an infrared thermal camera. A simplified finite element model was developed to calculate the temperature distribution onthe carbon fibre tow, which showed a good agreement with the experimental data. Results suggest that contact resistances in the towpregging line were significant and contact resistance heating changed the heating profile

Nature and origin of mineral coatings on volcanic rocks of the Black Mountain, Stonewall Mountain, and Kane Springs, Wash volcanic centers, Southern Nevada

LANDSAT Thematic Mapper imagery was evaluated over 3 Tertiary calderas in southern Nevada. Each volcanic center derived from a highly evolved silici magmatic system represented today by well exposed diverse lithologies. Distinctive imagery contrast between some of the late ash flows and earlier units follows from the high relative reflectance in longer wavelength bands (bands 5 and 7) of the former. Enhancement techniques provide color composite images which highlight some of the units in remarkable color contrast. Inasmuch as coatings on the tuffs are incompletely developed and apparently largely dependent spectrally on rock properties independent of petrochemistry, it is felt that the distinctive imagery characteristics are more a function of primary lithologic or petrochemical properties. Any given outcrop is backdrop for a variety of cover types, of which coatings, at various stages of maturity, are one. Petrographic and X-ray diffraction analysis of the outer air-interface zone of coatings reveal they are composed chiefly of amorphous compounds, probably with varying proportions of iron and manganese. Observations support an origin for some outer (air-interface) coating constituents exogenous to the underlying host

Climate-induced changes in river flow regimes will alter future bird distributions

Anthropogenic forcing of the climate is causing an intensification of the global water cycle, leading to an increase in the frequency and magnitude of floods and droughts. River flow shapes the ecology of riverine ecosystems and climate-driven changes in river flows are predicted to have severe consequences for riverine species, across all levels of trophic organization. However, understanding species' responses to variation in flow is limited through a lack of quantitative modelling of hydroecological interactions. Here, we construct a Bioclimatic Envelope Model (BEM) ensemble based on a suite of plausible future flow scenarios to show how predicted alterations in flow regimes may alter the distribution of a predatory riverine species, the White-throated Dipper (Cinclus cinclus). Models predicted a gradual diminution of dipper probability of occurrence between present day and 2098. This decline was most rapid in western areas of Great Britain and was principally driven by a projected decrease in flow magnitude and variability around low flows. Climate-induced changes in river flow may, therefore, represent a previously unidentified mechanism by which climate change may mediate range shifts in birds and other riverine biota