Graph-theoretical conditions for inscribability and Delaunay realizability

We present new graph-theoretical conditions for inscribable polyhedra and Delaunay triangulations. We establish several sufficient conditions of the following general form: if a polyhedron has a sufficiently rich collection of Hamiltonian subgraphs, then it is inscribable. These results have several consequences:All 4-connected polyhedra are inscribable.All simplical polyhedra in which all vertex degrees are between 4 and 6, inclusive, are inscribable.All triangulations without chords or nonfacial triangles are realizable as Delaunay triangulations.We also strengthen some earlier results about matchings in inscribable polyhedra. Specifically, we show that any nonbipartite inscribable polyhedron has a perfect matching containing any specified edge, and that any bipartite inscribable polyhedron has a perfect matching containing any two specified disjoint edges. We give examples showing that these results are best possible

Transfer Problem Dynamics: Macroeconomics of the Franco-Prussian War Indemnity

We study the classic transfer problem of predicting the effects of an international transfer on the terms of trade and the current account. A two-country model with debt and capital allows for realistic features of historical transfers: they follow wartime increases in government spending and are financed partly by borrowing. The model is applied to the largest historical transfer, the Franco-Prussian War indemnity of 1871-1873. In these three years, France transferred to Germany an amount equal to 22 percent of a year's GDP. When the transfer is combined with measured shocks to fiscal policy and a proxy for productivity shocks over the period, the model provides a very close fit to the historical sample paths of French GDP, terms of trade, net exports, and aggregate consumption. This makes a strong case for the dynamic general equilibrium approach to studying the transfer problem.transfer problem, current account, terms of trade

Three-dimensional inversion of large-scale EarthScope magnetotelluric data based on the integral equation method: geoelectrical imaging of the Yellowstone conductive mantle plume

Journal ArticleInterpretation of the EarthScope MT (magnetotelluric) data requires the development of a large-scale inversion method which can address two common problems of 3D MT inversion: computational time and memory requirements. We have developed an efficient method of 3D MT inversion based on an IE (integral equation) formulation of the MT forward modeling problem and a receiver footprint approach, implemented as a massively parallel algorithm. This method is applied to the MT data collected in the western United States as a part of the EarthScope project. As a result, we present one of the first 3D geoelectrical images of the upper mantle beneath Yellowstone revealed by this large-scale 3D inversion of the EarthScope MT data. These images show a highly conductive body associated with the tomographically imaged mantle plume-like layer of hot material rising from the upper mantle toward the Yellowstone volcano. The conductive body identified in these images is west-dipping in a similar way to a P-wave low-velocity body

The modest professor:Interpretive charity and interpretive humility in John Rawls's lectures on the history of political philosophy

Governmen

Sequence stratigraphy, chemostratigraphy and facies analysis of Cambrian Series 2 – Series 3 boundary strata in northwestern Scotland

Globally, the Series 2 – Series 3 boundary of the Cambrian System coincides with a major carbon isotope excursion, sea-level changes and trilobite extinctions. Here we examine the sedimentology, sequence stratigraphy and carbon isotope record of this interval in the Cambrian strata (Durness Group) of NW Scotland. Carbonate carbon isotope data from the lower part of the Durness Group (Ghrudaidh Formation) show that the shallow-marine, Laurentian margin carbonates record two linked sea-level and carbon isotopic events. Whilst the carbon isotope excursions are not as pronounced as those expressed elsewhere, correlation with global records (Sauk I – Sauk II boundary and Olenellus biostratigraphic constraint) identifies them as representing the local expression of the ROECE and DICE. The upper part of the ROECE is recorded in the basal Ghrudaidh Formation whilst the DICE is seen around 30m above the base of this unit. Both carbon isotope excursions co-occur with surfaces interpreted to record regressive–transgressive events that produced amalgamated sequence boundaries and ravinement/flooding surfaces overlain by conglomerates of reworked intraclasts. The ROECE has been linked with redlichiid and olenellid trilobite extinctions, but in NW Scotland, Olenellus is found after the negative peak of the carbon isotope excursion but before sequence boundary formation

Comprehensive simulations of superhumps

(Abridged) We use 3D SPH calculations with higher resolution, as well as with more realistic viscosity and sound-speed prescriptions than previous work to examine the eccentric instability which underlies the superhump phenomenon in semi-detached binaries. We illustrate the importance of the two-armed spiral mode in the generation of superhumps. Differential motions in the fluid disc cause converging flows which lead to strong spiral shocks once each superhump cycle. The dissipation associated with these shocks powers the superhump. We compare 2D and 3D results, and conclude that 3D simulations are necessary to faithfully simulate the disc dynamics. We ran our simulations for unprecedented durations, so that an eccentric equilibrium is established except at high mass ratios where the growth rate of the instability is very low. Our improved simulations give a closer match to the observed relationship between superhump period excess and binary mass ratio than previous numerical work. The observed black hole X-ray transient superhumpers appear to have systematically lower disc precession rates than the cataclysmic variables. This could be due to higher disc temperatures and thicknesses. The modulation in total viscous dissipation on the superhump period is overwhelmingly from the region of the disc within the 3:1 resonance radius. As the eccentric instability develops, the viscous torques are enhanced, and the disc consequently adjusts to a new equilibrium state, as suggested in the thermal-tidal instability model. We quantify this enhancement in the viscosity, which is ~10 per cent for q=0.08. We characterise the eccentricity distributions in our accretion discs, and show that the entire body of the disc partakes in the eccentricity.Comment: 18 pages (mn2e LaTeX), 14 figures, 5 tables, Accepted for publication in MNRA

Dynamic Analysis of Executables to Detect and Characterize Malware

It is needed to ensure the integrity of systems that process sensitive information and control many aspects of everyday life. We examine the use of machine learning algorithms to detect malware using the system calls generated by executables-alleviating attempts at obfuscation as the behavior is monitored rather than the bytes of an executable. We examine several machine learning techniques for detecting malware including random forests, deep learning techniques, and liquid state machines. The experiments examine the effects of concept drift on each algorithm to understand how well the algorithms generalize to novel malware samples by testing them on data that was collected after the training data. The results suggest that each of the examined machine learning algorithms is a viable solution to detect malware-achieving between 90% and 95% class-averaged accuracy (CAA). In real-world scenarios, the performance evaluation on an operational network may not match the performance achieved in training. Namely, the CAA may be about the same, but the values for precision and recall over the malware can change significantly. We structure experiments to highlight these caveats and offer insights into expected performance in operational environments. In addition, we use the induced models to gain a better understanding about what differentiates the malware samples from the goodware, which can further be used as a forensics tool to understand what the malware (or goodware) was doing to provide directions for investigation and remediation.Comment: 9 pages, 6 Tables, 4 Figure

Inviscid disturbance dynamics in barotropic shear flows

June 1994.Also issued as Gerald B. Smith's thesis (M.S.) -- Colorado State University, 1994.Includes bibliographical references.The inviscid nature of disturbance evolution in shear flows is investigated as an initial-value problem within the framework of nondivergent vorticity dynamics. To ensure a basic understanding of physical processes, disturbance evolution is first considered in a rectilinear system of simple shear. Particular emphasis is placed on identifying how the disturbance evolution depends on the zonal wavenumber and on the meridional structure of the initial conditions. Insight acquired from the rectilinear problem is then applied to a bounded Rankine vortex. Here, the dependency of disturbance evolution on the azimuthal wavenumber is of special interest. Recent development of a low-frequency balance theory for rapidly rotating vortices has provided observational evidence that the low azimuthal wavenumber asymmetries, especially wavenumber one, are dominant in the near-vortex region. The results of this work provide further theoretical evidence of an inviscid wave number selection mechanism that preferentially damps the higher wavenumber asymmetries. The radial structure and location of the initial conditions are found to be critical factors in determining how rapidly a disturbance is compressed or elongated. This in turn controls the rate of disturbance growth or decay. For swirling flows, a definition of an effective shear that accounts for both the radial variations in the initial conditions as well as the radial variation in the angular velocity is proposed. Using the reciprocal of this effective shear, time scales for a disturbance to decay to half its initial energy, the half-life time, are calculated for initial conditions and symmetric wind profiles that are found in hurricanes. Simple shear flow and the bounded Rankine vortex do not admit discrete modal solutions since there is no mean state vorticity gradient to support them. The unbounded Rankine vortex is briefly considered in order to investigate how the presence of discrete neutral modes modifies the nonmodal solutions presented in this work.Sponsored by the Office of Naval Research grant ONR N00014-93-1-0456, and the National Science Foundation grant NSF ATM-9312655