Strongly lensed neutral hydrogen emission: detection predictions with current and future radio interferometers

Strong gravitational lensing provides some of the deepest views of the Universe, enabling studies of high-redshift galaxies only possible with next-generation facilities without the lensing phenomenon. To date, 21 cm radio emission from neutral hydrogen has only been detected directly out to z~0.2, limited by the sensitivity and instantaneous bandwidth of current radio telescopes. We discuss how current and future radio interferometers such as the Square Kilometre Array (SKA) will detect lensed HI emission in individual galaxies at high redshift. Our calculations rely on a semi-analytic galaxy simulation with realistic HI disks (by size, density profile and rotation), in a cosmological context, combined with general relativistic ray tracing. Wide-field, blind HI surveys with the SKA are predicted to be efficient at discovering lensed HI systems, increasingly so at z > 2. This will be enabled by the combination of the magnification boosts, the steepness of the HI luminosity function at the high-mass end, and the fact that the HI spectral line is relatively isolated in frequency. These surveys will simultaneously provide a new technique for foreground lens selection and yield the highest redshift HI emission detections. More near term (and existing) cm-wave facilities will push the high redshift HI envelope through targeted surveys of known lenses.Comment: Accepted for publication in MNRAS Letters, 6 pages, 3 figures, 1 tabl

SKA HI end2end simulation

The current status of the HI simulation efforts is presented, in which a self consistent simulation path is described and basic equations to calculate array sensitivities are given. There is a summary of the SKA Design Study (SKADS) sky simulation and a method for implementing it into the array simulator is presented. A short overview of HI sensitivity requirements is discussed and expected results for a simulated HI survey are presented.Comment: 7 pages, 6 figues, need skads2009.cls file to late

Computer simulation of the heavy-duty turbo-compounded diesel cycle for studies of engine efficiency and performance

Reductions in heat loss at appropriate points in the diesel engine which result in substantially increased exhaust enthalpy were shown. The concepts for this increased enthalpy are the turbocharged, turbocompounded diesel engine cycle. A computer simulation of the heavy duty turbocharged turbo-compounded diesel engine system was undertaken. This allows the definition of the tradeoffs which are associated with the introduction of ceramic materials in various parts of the total engine system, and the study of system optimization. The basic assumptions and the mathematical relationships used in the simulation of the model engine are described

Increasing vertical mixing to reduce Southern Ocean deep convection in NEMO3.4

Most CMIP5 (Coupled Model Intercomparison Project Phase 5) models unrealistically form Antarctic Bottom Water by open ocean deep convection in the Weddell and Ross seas. To identify the mechanisms triggering Southern Ocean deep convection in models, we perform sensitivity experiments on the ocean model NEMO3.4 forced by prescribed atmospheric fluxes. We vary the vertical velocity scale of the Langmuir turbulence, the fraction of turbulent kinetic energy transferred below the mixed layer, and the background diffusivity and run short simulations from 1980. All experiments exhibit deep convection in the Riiser-Larsen Sea in 1987; the origin is a positive sea ice anomaly in 1985, causing a shallow anomaly in mixed layer depth, hence anomalously warm surface waters and subsequent polynya opening. Modifying the vertical mixing impacts both the climatological state and the associated surface anomalies. The experiments with enhanced mixing exhibit colder surface waters and reduced deep convection. The experiments with decreased mixing give warmer surface waters, open larger polynyas causing more saline surface waters and have deep convection across the Weddell Sea until the simulations end. Extended experiments reveal an increase in the Drake Passage transport of 4 Sv each year deep convection occurs, leading to an unrealistically large transport at the end of the simulation. North Atlantic deep convection is not significantly affected by the changes in mixing parameters. As new climate model overflow parameterisations are developed to form Antarctic Bottom Water more realistically, we argue that models would benefit from stopping Southern Ocean deep convection, for example by increasing their vertical mixing

The role for Federal R & D on alternative automotive power systems

Report submitted to the Office of Energy R & D Policy, National Science Foundatio

A computer simulation of the turbocharged turbo compounded diesel engine system: A description of the thermodynamic and heat transfer models

A computer simulation of the turbocharged turbocompounded direct-injection diesel engine system was developed in order to study the performance characteristics of the total system as major design parameters and materials are varied. Quasi-steady flow models of the compressor, turbines, manifolds, intercooler, and ducting are coupled with a multicylinder reciprocator diesel model, where each cylinder undergoes the same thermodynamic cycle. The master cylinder model describes the reciprocator intake, compression, combustion and exhaust processes in sufficient detail to define the mass and energy transfers in each subsystem of the total engine system. Appropriate thermal loading models relate the heat flow through critical system components to material properties and design details. From this information, the simulation predicts the performance gains, and assesses the system design trade-offs which would result from the introduction of selected heat transfer reduction materials in key system components, over a range of operating conditions

Separate processing of texture and form in the ventral stream : evidence from fMRI and visual agnosia.

Real-life visual object recognition requires the processing of more than just geometric (shape, size, and orientation) properties. Surface properties such as color and texture are equally important, particularly for providing information about the material properties of objects. Recent neuroimaging research suggests that geometric and surface properties are dealt with separately, within the lateral occipital cortex (LOC) and the collateral sulcus (CoS), respectively. Here we compared objects that either differed in aspect ratio or in surface texture only, keeping all other visual properties constant. Results on brain-intact participants confirmed that surface texture activates an area in the posterior CoS, quite distinct from the area activated by shape within LOC. We also tested two patients with visual object agnosia, one of whom (DF) performed well on the texture task but at chance on the shape task, while the other (MS) showed the converse pattern. This behavioral double dissociation was matched by a parallel neuroimaging dissociation, with activation in CoS but not LOC in patient DF, and activation in LOC but not CoS in patient MS. These data provide presumptive evidence that the areas respectively activated by shape and texture play a causally necessary role in the perceptual discrimination of these features

Frontal Structure of the Antarctic Circumpolar Current in the South Indian Ocean

Using recently published atlas data [Olbers et al., 1992] and the Fine Resolution Antarctic Model (FRAM) [Webb et al., 1991], an investigation has been conducted into the structure of the frontal jets centered around the region of the islands of Crozet (46°27'S, 52°0'E) and Kerguelen (48°15'S, 69°10'E) in the south Indian Ocean. Geostrophic current velocities and transports were calculated from the temperature and salinity fields available from the atlas and compared with results from FRAM and previous studies. We have identified the Agulhas Return Front (ARF) and the Subtropical Front (STF), as well as the following fronts of the Antarctic Circumpolar Current (ACC): the Subantarctic Front (SAP), the Polar Front (PF), and the Southern ACC Front (SACCF), from temperature and salinity characteristics and from geostrophic currents. This analysis of model and atlas data indicates that the jets associated with the ARF, STF, and SAF are topograpliically steered into a unique frontal system north of the islands, having some of the largest temperature and salinity gradients anywhere in the world ocean. The frontal jet associated with the ARF is detectable up to 75°E and has associated with it several northward branching jets. The PF bifurcates in the region of the Ob'Lena (Conrad) seamount; subsurface and surface expressions are identified, separated by as much as 8° of latitude immediately west of the Kerguelen Plateau. The surface expression, carrying the bulk of the transport (~65 Sv), is steered through the col in the Kerguelen Plateau at 56°S, 6° south of the latitude normally associated with the PF at this meridian. On crossing the plateau it rejoins the subsurface expression. In the south, passing eastward along the margin of the Antarctic continent and through the Princess Elizabeth Trough, a frontal jet is identified transporting up to 35 Sv, believed to be the SACCF [Orsi et al., 1995], placing the southern extent of the ACC in the region at 67°S. Copyright 1996 by the American Geophysical Union

Data-parallel agent-based microscopic road network simulation using graphics processing units

Road network microsimulation is computationally expensive, and existing state of the art commercial tools use task parallelism and coarse-grained data-parallelism for multi-core processors to achieve improved levels of performance. An alternative is to use Graphics Processing Units (GPUs) and fine-grained data parallelism. This paper describes a GPU accelerated agent based microsimulation model of a road network transport system. The performance for a procedurally generated grid network is evaluated against that of an equivalent multi-core CPU simulation. In order to utilise GPU architectures effectively the paper describes an approach for graph traversal of neighbouring information which is vital to providing high levels of computational performance. The graph traversal approach has been integrated within a GPU agent based simulation framework as a generalised message traversal technique for graph-based communication. Speed-ups of up to 43 ×  are demonstrated with increased performance scaling behaviour. Simulation of over half a million vehicles and nearly two million detectors at a rate of 25 ×  faster than real-time is obtained on a single GPU