The Degasperis-Procesi equation as a non-metric Euler equation

In this paper we present a geometric interpretation of the periodic Degasperis-Procesi equation as the geodesic flow of a right invariant symmetric linear connection on the diffeomorphism group of the circle. We also show that for any evolution in the family of $b$-equations there is neither gain nor loss of the spatial regularity of solutions. This in turn allows us to view the Degasperis-Procesi and the Camassa-Holm equation as an ODE on the Fr\'echet space of all smooth functions on the circle.Comment: 17 page

Shakedown analysis for rolling and sliding contact problems

There is a range of problems where repeated rolling or sliding contact occurs. For such problems shakedown and limit analyses provides significant advantages over other forms of analysis when a global understanding of deformation behaviour is required. In this paper, a recently developed numerical method. Ponter and Engelhardt (2000) and Chen and Ponter (2001), for 3-D shakedown analyses is used to solve the rolling and sliding point contact problem previously considered by Ponter, Hearle and Johnson (1985) for a moving Herzian contact, with friction, over a half space. The method is an upper bound programming method, the Linear Matching Method, which provides a sequence of reducing upper bounds that converges to the least upper bound associated with a finite element mesh and may be implemented within a standard commercial finite element code. The solutions given in Ponter, Hearle and Johnson (1985) for circular contacts are reproduced and extended to the case when the frictional contact stresses are at an angle to the direction of travel. Solutions for the case where the contact region is elliptic are also given

Fault seal controls on security of CO2 storage in aquifers

Structural traps for engineered storage of CO2 usually rely on a component of fault seal. In assessing the performance risk of storage sites, the conditions under which natural CO2 and CO2/hydrocarbon mixtures are retained by faults is poorly known. Mechanical failure can occur by flow along the fault plane due to extension, compression or shear. Geometric juxtaposition of aquifers or lack of low permeability fault gouge can enable flow across the fault plane. It is well established that faults which are close to being critically stressed have markedly different properties with respect to both their fluid flow and geomechanical characteristics. Here we examine three case studies. In the first two, the Rotliegend Sandstone reservoirs of the Oak and Fizzy Fields in the Southern North Sea, both of which are natural fault-bound gas fields with high CO2 content, we modify standard fault seal approaches to account for the different physical and chemical properties of CO2 to oil and CH4. In particular the impact of IFT and contact angle on threshold capillary pressure is investigated. Faults of both the Oak and Fizzy fields are analysed for fracture stability and slip tendency and are found to be stable (relative to present-day stresses) in all modelled scenarios and could withstand CO2 column heights in excess of trap height. However, under detailed assessment of fault seal potential for CO2-CH4 mixtures, both fields appear to be limited in column height by cross-fault leakage through carbonate layers of the overlying Zechstein Group. The third case study assessed the Captain Sandstone saline aquifer of the Inner Moray Firth. The in situ stress field was characterised using data available from hydrocarbon exploration wells. A range of potential stress fields were identified, and regional 3D geometric mapping of the major faults was then used to assess fault stability under the different potential stress regimes. Additionally, stereographic plots of fault dip angle and strike were used to deduce the pore pressure perturbation that could cause the mechanical reactivation of faults of any orientation. This accounted for unmapped faults that might truncate the storage reservoir and its overburden. In the stress scenario with the highest differential stress magnitudes low overpressures in the region of ~1.5 MPa could cause the reactivation of preferentially oriented faults, whereas higher induced pressures may be supported in lower differential stress regimes. Higher overpressure would also be required to cause the reactivation of the non-optimally oriented faults

Effect of Optaflexx and days on feed on feedlot performance, carcass characteristics, and skeletal muscle gene expression in yearling steers

Two-thousand two-hundred fifty-two yearling steers (690 lb) were used to evaluate the effects of Optaflexx and days on feed on finishing steer performance and carcass characteristics. Treatment groups included serial harvest dates of 150, 171, or 192 days. Within each harvest date, steers either received Optaflexx (200 mg/steer daily of ractopamine-HCl) for the final 28 days, or did not receive Optaflexx. All steers were initially implanted with Revalor-IS and were re-implanted with Revalor-S after 75 days on feed. At harvest, muscle samples from the inside round were obtained for mRNA analysis of the β- adrenergic receptors (AR). Optaflexx increased daily gains, hot carcass weight, and ribeye area, and improved feed efficiency. Optaflexx did not affect dressing percentage, USDA yield grade, or quality grade. Optaflexx did not change overall feed intake across the entire feeding period, but feed intake was increased during the 28-day period that steers received Optaflexx. As expected, greater days on feed decreased daily gains, overall feed intake, and the number of yield grade 1 and 2 carcasses, and worsened feed efficiency. Also, greater days on feed increased hot carcass weight, dressing percentage, and the number of prime and choice carcasses, as well as the number of yield grade 4 and 5 carcasses. Increasing days on feed decreased the abundance of mRNA for β1-AR and β3-AR, and increased the abundance of β2-AR mRNA. Optaflexx had no effect on abundance of mRNA for β1-AR or β3-AR, but it increased the abundance of mRNA for β2-AR. Optaflexx may affect expression of the β2-AR gene in skeletal muscle, which could impact the performance responses to Optaflexx feeding in steers

A New Dental Superalloy System: IV. X-Ray Diffraction Analysis

X-ray diffraction analysis of the alloy system Co-Ni-Cr-Ta showed that the ternary alloy base consisted of three phases (a, β, and σ). Addition of Ta caused a decrease in the intensity of the β lines. Further Ta additions caused diffraction lines characteristic of the intermetallic compound α-Co3Ta. At higher Ta concentrations, the intensity of the lines characteristic of the σ phase increased and lines characteristic of Co2Ta appeared.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66588/2/10.1177_00220345730520041701.pd

Generating socially appropriate tutorial dialog

Analysis of student-tutor coaching dialogs suggest that good human tutors attend to and attempt to influence the motivational state of learners. Moreover, they are sensitive to the social face of the learner, and seek to mitigate the potential face threat of their comments. This paper describes a dialog generator for pedagogical agents that takes motivation and face threat factors into account. This enables the agent to interact with learners in a socially appropriate fashion, and foster intrinsic motivation on the part of the learner, which in turn may lead to more positive learner affective states

Alloy Films Deposited by Electroplating as Precursors for Protective Oxide Coatings on Solid Oxide Fuel Cells Metallic Interconnect Materials

The successful development of stainless steel interconnects for intermediate temperature solid oxide fuel cells (SOFC) may be the materials breakthrough that makes SOFC technology truly commercial. Many of the ferritic stainless steels, however, suffer from a relatively high area specific resistance (ASR) after long exposure times at temperature and the Cr in the native oxide can evaporate and contaminate other cell components. Conductive coatings that resist oxide scale growth and chromium evaporation may prevent both of these problems. In the present study electrochemical deposition of binary alloys followed by oxidation of the alloy to form protective and conductive oxide layers is examined. Results are presented for the deposition of Mn/Co and Fe/Ni alloys via electroplating to form a precursor for spinel oxide coating formation. Analysis of the alloy coatings is done by SEM, EDS and XRD

QUICKSILVER - a general tool for electromagnetic PIC simulation

The dramatic increase in computational capability that has occurred over the last ten years has allowed fully electromagnetic simulations of large, complex, three-dimensional systems to move progressively from impractical, to expensive, and recently, to routine and widespread. This is particularly true for systems that require the motion of free charge to be self-consistently treated. The QUICKSILVER electromagnetic Particle-In-Cell (EM-PIC) code has been developed at Sandia National Laboratories to provide a general tool to simulate a wide variety of such systems. This tool has found widespread use for many diverse applications, including high-current electron and ion diodes, magnetically insulated power transmission systems, high-power microwave oscillators, high-frequency digital and analog integrated circuit packages, microwave integrated circuit components, antenna systems, radar cross-section applications, and electromagnetic interaction with biological material. This paper will give a brief overview of QUICKSILVER and provide some thoughts on its future development

An Improved Description of the Dielectric Breakdown in Oxides Based on a Generalized Weibull distribution

In this work, we address modal parameter fluctuations in statistical distributions describing charge-to-breakdown $(Q_{BD})$ and/or time-to-breakdown $(t_{BD})$ during the dielectric breakdown regime of ultra-thin oxides, which are of high interest for the advancement of electronic technology. We reobtain a generalized Weibull distribution ($q$-Weibull), which properly describes $(t_{BD})$ data when oxide thickness fluctuations are present, in order to improve reliability assessment of ultra-thin oxides by time-to-breakdown $(t_{BD})$ extrapolation and area scaling. The incorporation of fluctuations allows a physical interpretation of the $q$-Weibull distribution in connection with the Tsallis statistics. In support to our results, we analyze $t_{BD}$ data of SiO$_2$-based MOS devices obtained experimentally and theoretically through a percolation model, demonstrating an advantageous description of the dielectric breakdown by the $q$-Weibull distribution.Comment: 5 pages, 3 figure