Statistical emulation of a tsunami model for sensitivity analysis and uncertainty quantification

Due to the catastrophic consequences of tsunamis, early warnings need to be issued quickly in order to mitigate the hazard. Additionally, there is a need to represent the uncertainty in the predictions of tsunami characteristics corresponding to the uncertain trigger features (e.g. either position, shape and speed of a landslide, or sea floor deformation associated with an earthquake). Unfortunately, computer models are expensive to run. This leads to significant delays in predictions and makes the uncertainty quantification impractical. Statistical emulators run almost instantaneously and may represent well the outputs of the computer model. In this paper, we use the Outer Product Emulator to build a fast statistical surrogate of a landslide-generated tsunami computer model. This Bayesian framework enables us to build the emulator by combining prior knowledge of the computer model properties with a few carefully chosen model evaluations. The good performance of the emulator is validated using the Leave-One-Out method

New Teachers Enacting Culturally Relevant Pedagogy in Literacy Instruction

This multiple case study investigated the experiences of majority culture teachers at the beginning of their careers as they navigated enacting culturally relevant pedagogy (CRP) in their literacy instruction. The study explored how the new teachers described and enacted CRP in their classrooms, what they described as formative to their work as culturally relevant educators, what they identified as challenging, and what they found to be sustaining. The study shares case reports of each participant followed by a cross case analysis. Several themes were noteworthy from the analysis: 1) participants viewed an event or time period as formative, 2) participants felt their agency as teachers to incorporate CRP into their literacy instruction was limited; 3) participants persisted in enacting CRP within and beyond the curriculum and 4) participants held certain dispositions requisite for culturally relevant educators. Implications for teacher preparation programs include calls to prioritize cultural relevance in recruitment and hiring practices as well as ongoing professional development for instructors. Implications for school districts include recognizing that new teachers bring fresh ideas and resources regarding CRP. Ultimately, CRP requires nuanced and context dependent perspectives as well as ongoing reflexivity and collaboration

Shocks in unmagnetized plasma with a shear flow: Stability and magnetic field generation

A pair of curved shocks in a collisionless plasma is examined with a two-dimensional particle-in-cell (PIC) simulation. The shocks are created by the collision of two electron-ion clouds at a speed that exceeds everywhere the threshold speed for shock formation. A variation of the collision speed along the initially planar collision boundary, which is comparable to the ion acoustic speed, yields a curvature of the shock that increases with time. The spatially varying Mach number of the shocks results in a variation of the downstream density in the direction along the shock boundary. This variation is eventually equilibrated by the thermal diffusion of ions. The pair of shocks is stable for tens of inverse ion plasma frequencies. The angle between the mean flow velocity vector of the inflowing upstream plasma and the shock's electrostatic field increases steadily during this time. The disalignment of both vectors gives rise to a rotational electron flow, which yields the growth of magnetic field patches that are coherent over tens of electron skin depths.Comment: 10 pages, 10 figures accepted for publication in Physics of Plasma

Emulators in the investigation of sensitivities and uncertainties in tsunami models

This thesis consists of three parts with the unifying theme of applying emulators and other statistical methods to the investigation of sensitivities and uncertainties in tsunami models. The first part contains the statistical emulation of the wave time series at fixed locations that are obtained using an analytical landslide-generated tsunami computer model. Leave-one-out diagnostics are used to validate the emulator, showing excellent agreement in predictions and model evaluations. The emulator is used for sensitivity and uncertainty analyses, where many evaluations are necessary. The computational time required for both analyses is at least 20,000 times lower using the emulator instead of the computationally expensive model. The second part investigates the significance of the seabed deformation representation on tsunami wave predictions of the advanced VOLNA tsunami model. A novel realistic representation of the tsunami source deformation using quadratic curves is compared with simpler representations used in existing tsunami models: single block, four blocks, sixteen blocks and “piano keys”. Factor-of-two differences in wave elevations obtained for different representations of seabed deformation. The last part presents an investigation of tsunamis produced by different fault rupture scenarios on the Cascadia Subduction Zone. Polygons are used to model the source geometry and quadratic curves the deformation in different source event scenarios that are chosen using experimental design. The VOLNA model is evaluated for these scenarios to explore how the source characteristics affect the wave amplitude and coastal inundation predictions. Statistical emulation is applied to a large number of locations in order to investigate the use of emulators in place of expensive tsunami simulators in practical applications. The leave-one-out diagnostics show that the application of Registration and Functional Principal Components techniques to the emulation process leads to improved predictions. Finally, a limiting event is investigated in order to obtain the worst-case scenario inundation along the whole margin in a single simulation

Oral administration of chestnut tannins to reduce the duration of neonatal calf diarrhea

Background: Neonatal calf diarrhea is generally caused by infectious agents and is a very common disease in bovine practice, leading to substantial economic losses. Tannins are known for their astringent and anti- inflammatory properties in the gastro-enteric tract. The aim of this study was to evaluate the effect of the oral administration of chestnut tannins (Castanea sativa Mill.) in order to reduce the duration of calf neonatal diarrhea. Twenty-four Italian Friesian calves affected by neonatal diarrhea were included. The duration of the diarrheic episode (DDE) was recorded and the animals were divided into a control group (C), which received Effydral® in 2 l of warm water, and a tannin-treated group (T), which received Effydral® in 2 l of warm water plus 10 g of extract of chestnut tannins powder. A Mann-Whitney test was performed to verify differences for the DDE values between the two groups. Results: The DDE was significantly higher in group C than in group T (p = 0.02), resulting in 10.1 ± 3.2 and 6.6 ± 3. 8 days, respectively. Conclusions: Phytotherapic treatments for various diseases have become more common both in human and in veterinary medicine, in order to reduce the presence of antibiotic molecules in the food chain and in the environment. Administration of tannins in calves with diarrhea seemed to shorten the DDE in T by almost 4 days compared to C, suggesting an effective astringent action of chestnut tannins in the calf, as already reported in humans. The use of chestnut tannins in calves could represent an effective, low-impact treatment for neonatal diarrhea

One-dimensional thermal pressure-driven expansion of a pair cloud into an electron-proton plasma

Recently a filamentation instability was observed when a laser-generated pair cloud interacted with an ambient plasma. The magnetic field it drove was strong enough to magnetize and accelerate the ambient electrons. It is of interest to determine if and how pair cloud-driven instabilities can accelerate ions in the laboratory or in astrophysical plasma. For this purpose, the expansion of a localized pair cloud with the temperature 400 keV into a cooler ambient electron-proton plasma is studied by means of one-dimensional particle-in-cell (PIC) simulations. The cloud's expansion triggers the formation of electron phase space holes that accelerate some protons to MeV energies. Forthcoming lasers might provide the energy needed to create a cloud that can accelerate protons.Comment: 5 pages 4 figures, accepted for publication in Physics of Plasma

Multi-response Optimization of Laser Welding of Stainless Steels in a Constrained Fillet Joint Configuration Using RSM

This paper presents experimental design approach to process parameter optimization for CW Nd/YAG laser welding of ferritic/austenitic stainless steels in a constrained fillet configuration. To determine the optimal welding parameters, response surface methodology was used to develop a set of mathematical models relating the welding parameters to each of the weld characteristics. The quality criteria considered to determine the optimal settings were the maximization of weld resistance length and shearing force, and the minimization of weld radial penetration. Laser power, welding speed, and incident angle are the factors that affect the weld bead characteristics significantly. A rapid decrease in weld shape factor and increase in shearing force with the line energy input in the range of 15-17 kJ/m depicts the establishment of a keyhole regime. A focused beam with laser power and welding speed respectively in the range of 860-875 W and 3.4-4.0 m/min and an incident angle of around 12° were identified as the optimal set of laser welding parameters to obtain stronger and better welds

Laser beam welding of dissimilar stainless steels in a fillet joint configuration

This paper investigates laser beam welding of dissimilar AISI 304L and AISI 430 stainless steels. Experimental studies were focused on effects of laser power, welding speed, defocus distance, beam incident angle, and line energy on weld bead geometry and shearing force. Metallurgical analysis was conducted on a selected weld only to show various microstructures typically formed at different zones and consequent change in microhardness. Laser power and welding speed were the most significant factors affecting weld geometry and shearing force. All the bead characteristics but radial penetration depth decreased with increased beam incident angle. The focused beam allowed selecting lower laser power and faster welding speed to obtain the same weld geometry. Weld shape factor increased rapidly due to keyhole formation for line energy input ranging from 15 kJ/m to 17 kJ/m. Fusion zone microstructures contained a variety of complex austenite-ferrite structures. Local microhardness of fusion zone was greater than that of both base metals