Least-biased correction of extended dynamical systems using observational data

We consider dynamical systems evolving near an equilibrium statistical state where the interest is in modelling long term behavior that is consistent with thermodynamic constraints. We adjust the distribution using an entropy-optimizing formulation that can be computed on-the- fly, making possible partial corrections using incomplete information, for example measured data or data computed from a different model (or the same model at a different scale). We employ a thermostatting technique to sample the target distribution with the aim of capturing relavant statistical features while introducing mild dynamical perturbation (thermostats). The method is tested for a point vortex fluid model on the sphere, and we demonstrate both convergence of equilibrium quantities and the ability of the formulation to balance stationary and transient- regime errors.Comment: 27 page

A study of planar Richtmyer-Meshkov instability in fluids with Mie-Grüneisen equations of state

We present a numerical comparison study of planar Richtmyer-Meshkov instability with the intention of exposing the role of the equation of state. Results for Richtmyer-Meshkov instability in fluids with Mie-Grüneisen equations of state derived from a linear shock-particle speed Hugoniot relationship (Jeanloz, J. Geophys. Res. 94, 5873, 1989; McQueen et al., High Velocity Impact Phenomena (1970), pp. 294–417; Menikoff and Plohr, Rev. Mod. Phys. 61(1), 75 1989) are compared to those from perfect gases under nondimensionally matched initial conditions at room temperature and pressure. The study was performed using Caltech’s Adaptive Mesh Refinement, Object-oriented C++ (AMROC) (Deiterding, Adaptive Mesh Refinement: Theory and Applications (2005), Vol. 41, pp. 361–372; Deiterding, “Parallel adaptive simulation of multi-dimensional detonation structures,” Ph.D. thesis (Brandenburgische Technische Universität Cottbus, September 2003)) framework with a low-dissipation, hybrid, center-difference, limiter patch solver (Ward and Pullin, J. Comput. Phys. 229, 2999 (2010)). Results for single and triple mode planar Richtmyer-Meshkov instability when a reflected shock wave occurs are first examined for mid-ocean ridge basalt (MORB) and molybdenum modeled by Mie-Grüneisen equations of state. The single mode case is examined for incident shock Mach numbers of 1.5 and 2.5. The planar triple mode case is studied using a single incident Mach number of 2.5 with initial corrugation wavenumbers related by k_1 = k_2+k_3. Comparison is then drawn to Richtmyer-Meshkov instability in perfect gases with matched nondimensional pressure jump across the incident shock, post-shock Atwood ratio, post-shock amplitude-to-wavelength ratio, and time nondimensionalized by Richtmyer’s linear growth time constant prediction. Differences in start-up time and growth rate oscillations are observed across equations of state. Growth rate oscillation frequency is seen to correlate directly to the oscillation frequency for the transmitted and reflected shocks. For the single mode cases, further comparison is given for vorticity distribution and corrugation centerline shortly after shock interaction. Additionally, we examine single mode Richtmyer-Meshkov instability when a reflected expansion wave is present for incident Mach numbers of 1.5 and 2.5. Comparison to perfect gas solutions in such cases yields a higher degree of similarity in start-up time and growth rate oscillations. The formation of incipient weak waves in the heavy fluid driven by waves emanating from the perturbed transmitted shock is observed when an expansion wave is reflected

Predicted hydrodynamic and sediment transport impacts of breakwater construction in Tauranga Harbour, New Zealand

The study predicted the impact of a proposed breakwater development, along the northern boundary of the Tauranga Bridge Marina, on existing hydrodynamics and sediment transport. Numerical modelling was undertaken using the DHI MIKE 21 modelling suite. A 25 m grid resolution regional hydrodynamic model of Tauranga Harbour was established to provide boundary conditions for a 4 m grid resolution local hydrodynamic model of the Stella Passage, Town Reach, and Waipu Bay region. Calibration and verification was achieved by comparing model predictions with measurements from tidal gauges and field deployed ADV instruments. A wave model was set-up to provide predictions of wave-induced sediment transport. A sediment transport model was developed to identify sediment transport pathways and areas of erosion and accretion. A pile and panel breakwater was recommended based on predictions of reduced current velocity within the marina and a limited increase along the Sulphur Point wharf. Flow diversion and channel constriction contributed to increased maximum velocities of 10% near the Stella Passage drop-off, increased peak tide velocities of up to 0.3 m.s⁻¹ west of the breakwater, and flood jet development off the western tip of the breakwater. Increased accretion north of the drop-off was predicted in response to increased annual spring transport rates in Town Reach from 10 m³/yr/m. Peak tide velocities within the marina were reduced by 0.2 – 0.5 m.s⁻¹ in the north and up to 0.2 m.s⁻¹ in the south and annual spring transport rates decreased from up to 50 m³/yr/m to predominantly <5 m³/yr/m. Two dredging scenarios proposed by the Port of Tauranga were also simulated. In dredging scenario one, the Stella Passage was deepened to 16.0 m below Chart Datum. Variation in flow patterns were predicted within the Stella Passage and flood velocity increased through the western side. In dredging scenario two, the dredged area and Sulphur Point wharf were extended southward into Town Reach. In the western Stella Passage, maximum flood velocity increased by 0.2 m.s⁻¹ and peak ebb velocity increased by up to 0.3 m.s⁻¹. Peak flood velocity decreased by up to 0.3 m.s⁻¹ north of the marina. Breakwater addition to the dredging scenario one simulation produced similar results compared with the combined breakwater and existing bathymetry simulation. The breakwater and dredging extension in scenario two, both independently acted to focus flow through west side of Town Reach. Increased erosion was predicted toward the drop-off into the dredging extension. Dredging reduced the influence of the breakwater through the western Stella Passage. The breakwater increased maximum ebb velocity by 29% for the existing bathymetry, 25% for dredging scenario one, and 20% for dredging scenario two. Existing sediment transport patterns in Waipu Bay were unaltered by breakwater development or the combined breakwater development and dredging and wharf extensions. An area of high seabed elevation, in western Waipu Bay, was the preferred location for an artificial bird roost. The existing bathymetry was altered to simulate different dredge island dimensions. The recommended design was oval shaped with an east-west orientation. This design displayed consistently low annual spring transport rates of <0.1 m³/yr/m

Development of a Fast Gas-Solid Flow Simulation for Control of the Pneumatic Conveying System on Air Seeders

Limitations of the pneumatic conveying system are an obstacle to the improvement of air seeding technology. Operators often run conveying velocities far above the minimum requirement. This is common because lower conveying velocities - which could reduce waste, energy consumption and hydraulic requirements - put the system at risk of blockages and non-uniform distribution. Furthermore, new precision technologies such as variable rate application and sectional control introduce imbalances to the highly coupled and distributed conveying system. Incorporating adaptive control mechanisms has been theorized as a potential means of improving conveying system performance. Real-time prediction of conveying system flow conditions is a prerequisite for the proposed control strategies. There is limited existing research regarding control and modeling for air seeders or similar pneumatic conveying systems. While there is extensive research for multiphase flow modeling, few examples prioritize computational efficiency to the extent that real-time simulation is feasible. Application to control dictates that computational speed, in addition to accuracy, is essential. The purpose of this research was to identify, develop and validate a method for predicting flow conditions within a pneumatic conveying system that is suitable for control applications. A low-computational cost, one-dimensional model and simulation have been developed for fast prediction of bulk multiphase flow conditions within the pneumatic conveying system. The model is a simplified form of the Eulerian-Eulerian (two-fluid) equations for fluid-particle flows. The differential model equations were discretized via the finite volume method and solved using computational fluid dynamics techniques. Specifically, the SIMPLER algorithm for the solution of coupled equations was used. The simulation program, which employs the numerical methods to obtain solutions to the discrete equations, was implemented in MATLAB®. Experimental data were collected using a laboratory apparatus which approximated a straight horizontal pneumatic conveying line. The inner diameter of the experimental conveying line was 57.4 mm. Spherical plastic particles with a mean diameter of 3.56 mm were conveyed. Testing consisted of dilute flows only that were relevant for air seeding conditions. Experiments covered air velocities of 20 to 30 m/s and mass loadings of 0.84 to 4.68. Recorded data included steady-state and transient measurements for fluid pressure and bulk particle velocity. The experimental data were used to validate simulation results. The accuracy of the model for steady-state conditions was acceptable for sufficiently dilute and well-developed flow. The simulation predicted experimental fluid pressure within 6% in all tests. For moderate mass loadings, simulation error for particle velocity was below 10%. At higher mass loadings, accuracy for particle velocity began to deteriorate and an error of > 25% was observed. Analysis of the model’s accuracy for transient conditions was inconclusive. Evidence suggested that transient simulation results may be quite good. However, limitations of the continuous equations and experimental factors complicated the analysis, preventing a definitive verdict regarding transient accuracy. Simulation performance with respect to computing time was excellent. Simulation results were found to be relatively insensitive to the size of time and spatial step used, allowing for the program to execute in less time than was being simulated. The fastest execution recorded required 5.0 sec to simulate 60 sec of transient flow, and results deviated minimally from higher resolution simulations. Results indicated the potential for optimization between speed and accuracy. While the simplified model only calculates a limited number of bulk flow properties, it delivered timely results with reasonable accuracy and with relatively low computational effort. Assessment of the developed model and simulation has concluded a suitable potential for control application. Acceptable accuracy and computing speed were obtained to justify further development efforts. The prescribed methodology provides a foundation for future expansion and improvement. There is potential to incorporate fast multiphase flow simulation into control infrastructure to improve the performance of the air seeder conveying system

Optimal Networks from Error Correcting Codes

To address growth challenges facing large Data Centers and supercomputing clusters a new construction is presented for scalable, high throughput, low latency networks. The resulting networks require 1.5-5 times fewer switches, 2-6 times fewer cables, have 1.2-2 times lower latency and correspondingly lower congestion and packet losses than the best present or proposed networks providing the same number of ports at the same total bisection. These advantage ratios increase with network size. The key new ingredient is the exact equivalence discovered between the problem of maximizing network bisection for large classes of practically interesting Cayley graphs and the problem of maximizing codeword distance for linear error correcting codes. Resulting translation recipe converts existent optimal error correcting codes into optimal throughput networks.Comment: 14 pages, accepted at ANCS 2013 conferenc

Proton-Ion Medical Machine Study (PIMMS), 1

The Proton-Ion Medical Machine Study (PIMMS) group was formed following an agreement between the Med-AUSTRON (Austria) and the TERA Foundation (Italy) to combine their efforts in the design of a cancer therapy synchrotron. CERN agreed to host this study in its PS Division and a close collaboration was set up with GSI (Germany). The study group was later joined by Onkologie-2000 (Czech Republic). Effort was first focused on the theoretical understanding of slow extraction and the techniques required to produce a smooth beam spill for the conformal treatment of complex-shaped tumours with a sub-millimetre accuracy by active scanning with proton and carbon ion beams. Considerations for passive scanning were also included. The more general and theoretical aspects of the study are recorded in Part I and the more specific technical design considerations are presented in a second volume Part II. The PIMMS team started their work in January 1996 in the PS Division and continued for a period of three years

Proceedings of the 2011 New York Workshop on Computer, Earth and Space Science

The purpose of the New York Workshop on Computer, Earth and Space Sciences is to bring together the New York area's finest Astronomers, Statisticians, Computer Scientists, Space and Earth Scientists to explore potential synergies between their respective fields. The 2011 edition (CESS2011) was a great success, and we would like to thank all of the presenters and participants for attending. This year was also special as it included authors from the upcoming book titled "Advances in Machine Learning and Data Mining for Astronomy". Over two days, the latest advanced techniques used to analyze the vast amounts of information now available for the understanding of our universe and our planet were presented. These proceedings attempt to provide a small window into what the current state of research is in this vast interdisciplinary field and we'd like to thank the speakers who spent the time to contribute to this volume.Comment: Author lists modified. 82 pages. Workshop Proceedings from CESS 2011 in New York City, Goddard Institute for Space Studie

Morphodynamics of the Whitianga Tidal Inlet and Buffalo Bay, New Zealand

The primary aim of this study was to investigate the sedimentation processes within Buffalo Bay, particularly within and adjacent to the Whitianga tidal inlet, in order to ascertain reasons for the shoaling at both the inlet, and the identified shallow zone around Pandora Rock. Comparison of historic bathymetries suggests the ebb delta and ebb discharge channel of the Whitianga tidal inlet are rapidly accreting and the ebb tidal discharge channel is gradually migrating northeast towards Whakapenui Point. Accretion rates of up to 25 cm y-1 were calculated in the ebb delta and inlet discharge channel area between 1979 and 1995 and aerial photo comparisons suggest the ebb delta area had increased by 400 % between 1990 and 2002. Results of the hydrodynamic and sediment transport modelling suggest the rapid accretion in the ebb delta vicinity is likely to be caused by a combination of catchment estuary inputs, which are deposited on the ebb tide as the ebb flow decelerates over the ebb delta, and inputs that have been moved south along Buffalo Beach by flood currents and an eddy that forms landward of the ebb tidal discharge. Residual tidal velocities further suggest a deposition zone in the ebb delta vicinity resulting from opposing currents and the deceleration of currents. Hydrodynamic modelling results indicate the isolated shallow zone around Pandora rock appears to be caused by a transient eddy in the southern section of Buffalo Bay. The eddy is formed by the ebb tidal discharge from the inlet. Accretion probably occurs in the centre of the eddy which moves north as the ebb tide progresses. Results obtained from a current meter and sediment trap deployed in northern Buffalo Bay suggest suspended sediment transport is minimal in northern Buffalo Bay, only occurring with large wave activity. Results of the hydrodynamic and sediment transport modelling further demonstrate that this area experiences low flow velocities, and has little interaction with the rest of Buffalo Bay. The minimal sediment input to this area, combined with the occasional erosion of the seafloor, primarily by wave activity, is thought to have resulted in long term erosion of northwestern Buffalo Bay between 1938 and 1979. Although the beach and nearshore is eroding, it is likely the addition of sediment would act to stabilise this section of eroding beach. Renourishment material could be provided by the ebb delta, the southern tip of Buffalo Bay or the isolated sandbar northeast of the inlet entrance