Towards the optimal Pixel size of dem for automatic mapping of landslide areas

Determining appropriate spatial resolution of digital elevation model (DEM) is a key step for effective landslide analysis based on remote sensing data. Several studies demonstrated that choosing the finest DEM resolution is not always the best solution. Various DEM resolutions can be applicable for diverse landslide applications. Thus, this study aims to assess the influence of special resolution on automatic landslide mapping. Pixel-based approach using parametric and non-parametric classification methods, namely feed forward neural network (FFNN) and maximum likelihood classification (ML), were applied in this study. Additionally, this allowed to determine the impact of used classification method for selection of DEM resolution. Landslide affected areas were mapped based on four DEMs generated at 1m, 2m, 5m and 10m spatial resolution from airborne laser scanning (ALS) data. The performance of the landslide mapping was then evaluated by applying landslide inventory map and computation of confusion matrix. The results of this study suggests that the finest scale of DEM is not always the best fit, however working at 1m DEM resolution on micro-topography scale, can show different results. The best performance was found at 5m DEM-resolution for FFNN and 1m DEM resolution for results. The best performance was found to be using 5m DEM-resolution for FFNN and 1m DEM resolution for ML classification

Dense, Fe-rich Ejecta in Supernova Remnants DEM L238 and DEM L249: A New Class of Type Ia Supernova?

We present observations of two LMC supernova remnants (SNRs), DEM L238 and DEM L249, with the Chandra and XMM-Newton X-ray satellites. Bright central emission, surrounded by a faint shell, is present in both remnants. The central emission has an entirely thermal spectrum dominated by strong Fe L-shell lines, with the deduced Fe abundance in excess of solar and not consistent with the LMC abundance. This Fe overabundance leads to the conclusion that DEM L238 and DEM L249 are remnants of thermonuclear (Type Ia) explosions. The shell emission originates in gas swept up and heated by the blast wave. A standard Sedov analysis implies about 50 solar masses in both swept-up shells, SNR ages between 10,000 and 15,000 yr, low (< 0.05 cm^-3) preshock densities, and subluminous explosions with energies of 3x10^50 ergs. The central Fe-rich supernova ejecta are close to collisional ionization equilibrium. Their presence is unexpected, because standard Type Ia SNR models predict faint ejecta emission with short ionization ages. Both SNRs belong to a previously unrecognized class of Type Ia SNRs characterized by bright interior emission. Denser than expected ejecta and/or a dense circumstellar medium around the progenitors are required to explain the presence of Fe-rich ejecta in these SNRs. Substantial amounts of circumstellar gas are more likely to be present in explosions of more massive Type Ia progenitors. DEM L238, DEM L249, and similar SNRs could be remnants of ``prompt'' Type Ia explosions with young (~100 Myr old) progenitors.Comment: 24 pages, 8 figures, ApJ, in pres

Pore-scale modeling of fluid-particles interaction and emerging poromechanical effects

A micro-hydromechanical model for granular materials is presented. It combines the discrete element method (DEM) for the modeling of the solid phase and a pore-scale finite volume (PFV) formulation for the flow of an incompressible pore fluid. The coupling equations are derived and contrasted against the equations of conventional poroelasticity. An analogy is found between the DEM-PFV coupling and Biot's theory in the limit case of incompressible phases. The simulation of an oedometer test validates the coupling scheme and demonstrates the ability of the model to capture strong poromechanical effects. A detailed analysis of microscale strain and stress confirms the analogy with poroelasticity. An immersed deposition problem is finally simulated and shows the potential of the method to handle phase transitions.Comment: accepted in Int. Journal for Numerical and Analytical Methods in Geomechanic

Calibration of Nebular Emission-Line Diagnostics: I. Stellar Effective Temperatures

We present a detailed comparison of optical H II region spectra to photoionization models based on modern stellar atmosphere models. We examine both spatially resolved and integrated emission-line spectra of the HII regions DEM L323, DEM L243, DEM L199, and DEM L301 in the Large Magellanic Cloud. The published spectral classifications of the dominant stars range from O7 to WN3, and morphologies range from Stromgren sphere to shell structure. Two of the objects include SNR contamination. The overall agreement with the predictions is generally within 0.2 dex for major diagnostic line ratios. An apparent pattern in the remaining discrepancies is that the predicted T_e is ~1000 K hotter than observed. (Abridged) Our analysis of the complex DEM L199 allows a nebular emission-line test of unprecedented detail for WR atmospheres. Surprisingly, we find no nebular He II 4686 emission, despite the fact that both of the dominant WN3 stars should be hot enough to fully ionize He I in their atmospheres. We confirm that the \eta-prime emission-line parameter is not as useful as hoped for determining the ionizing stellar effective temperature, T*. Both empirically and theoretically, we find that it is insensitive for T* >40 kK, and that it also varies spatially. The shock-contaminated objects show that \eta-prime will also yield a spuriously high T* in the presence of shocks. It is furthermore sensitive to shell morphology. We suggest [Ne III]/Hb as an additional probe of T*. Although it is abundance-dependent, [Ne III]/Hb has higher sensitivity to T*, is independent of morphology, and is insensitive to shocks in our objects. We attempt a first empirical calibration of these nebular diagnostics of T*.Comment: Accepted to ApJS. 37 pages, 14 figures, including 12 jpeg files. Uses emulateapj Latex style file. Single PS file preprint available at http://www.stsci.edu/~oey, along with unabridged abstrac

The stable long-run CAPM and the cross-section of expected returns

The capital-asset-pricing model (CAPM) is one of the most popular methods of financial market analysis. But, evidence of the poor empirical performance of the CAPM has accumulated in the literature. For example, based on their empirical results regarding the relation between market Beta and average return, Fama and French (1996) conclude that the CAPM is no longer a useful tool for empirical financial market analysis. Most empirical studies of the conventional CAPM take, however, neither the fat-tails of return data nor the price relationship between an asset of interest and the bench market portfolio into account. In the framework of a univariate Beta-model we consider a stable long-run CAPM taking account of the fat-tails of stock returns and the common stochastic trends between stock prices. Using the same data used by Fama and French (1996), the stable long-run CAPM demonstrates that Markowitz rule of the expected returns and variance of returns can (still) -without any use of firm specific variables- explain the variation of the cross-sectional average returns. -- Das Capital-Asset-Pricing-Modell (CAPM) ist einer der populärsten empirischen Ansätze zur Analyse der Finanzmarktdaten. In der Literatur jedoch sind eher Gegenbeweise über seine empirische Tauglichkeit akkumuliert. Fama und French (1996) haben beispielsweise aufgrund ihrer empirischen Untersuchungsergebnisse über die Beziehung zwischen dem Markt-Beta und der Durchschnittsrendite schlussgefolgert, daß das CAPM keine nützliche Methode für empirische Finanzmarktanalyse mehr sein kann. Die meisten Arbeiten aber, die sich mit dem CAPM beschäftigen, berücksichtigen weder die ausreißerreiche empirische Renditenverteilung noch die Preisbeziehung zwischen dem einzelnen Kurs und dem Benchmark. In der vorliegenden Arbeit wird im Rahmen univariater Beta-Modelle ein Versuch zur Spezifikation eines stabilen langfristigen CAPM gemacht, das sowohl die ausreißerreiche empirische Renditenverteilung als auch die Preisbeziehung zwischen dem einzelnen Kurs und dem Benchmark berücksichtigt. Mit dem Datensatz von Fama und French (1996) wird gezeigt, daß das stabile langfristige CAPM in der Lage ist, anhand der Markowitz?schen Mittelwert-Varianz-Regel ?ohne Hinzufügen firmspezifischer Variablen? die Variabilität durchschnittlicher Rendite in Querschnittsdaten zu erklären.CAPM,Stable Paretian distribution,Sto chastic common trend