A Fixed-point Scheme for the Numerical Construction of Magnetohydrostatic Atmospheres in Three Dimensions     

S. A. Gilchrist  D. C. Braun  G. Barnes 《Solar physics》2016,291(12):3583-3603

Magnetohydrostatic models of the solar atmosphere are often based on idealized analytic solutions because the underlying equations are too difficult to solve in full generality. Numerical approaches, too, are often limited in scope and have tended to focus on the two-dimensional problem. In this article we develop a numerical method for solving the nonlinear magnetohydrostatic equations in three dimensions. Our method is a fixed-point iteration scheme that extends the method of Grad and Rubin (Proc. 2nd Int. Conf. on Peaceful Uses of Atomic Energy 31, 190, 1958) to include a finite gravity force. We apply the method to a test case to demonstrate the method in general and our implementation in code in particular.  相似文献   

Floods in megacity environments: vulnerability and coping strategies of slum dwellers in Dhaka/Bangladesh     

Boris Braun  Tibor Aßheuer 《Natural Hazards》2011,58(2):771-787

In many megacities of the global south, the combination of rapid population growth and high pressure on space for housing, results in urban growth taking place in areas particularly prone to natural hazards. Dhaka, the capital of Bangladesh, is no exception to this rule. Many marginal settlements or slums are located on low-lying land at high risk of flooding. This paper analyzes the vulnerability of slum dwellers in Dhaka and highlights the major factors behind their sensitivity to floods and their ability to adapt to the related changes. The empirical findings presented are based on a questionnaire survey covering 625 households in five slum areas of Dhaka. Our data suggests that social capital plays an important role with regard to the ability of slum dwellers to find ways to live with the floods. Regardless of how strongly people are affected, mutual help and support are dominant features in times of crises. While poorly educated and resourced slum dwellers are highly vulnerable to external shocks, they still show a surprising capacity to cope with natural calamities.  相似文献   

A multi-level segmentation methodology for dual-polarized SAR data     

M. Dabboor  V. Karathanassi  A. Braun 《International Journal of Applied Earth Observation and Geoinformation》2011

An innovative methodology for dual-polarized Synthetic Aperture Radar (SAR) data segmentation is proposed. The methodology is based on the thresholding of the 1D-histograms of the two images produced by the dual polarimetric bands. Thresholding of the histograms is performed using a nonparametric algorithm. Histograms after thresholding are combined together in a two dimensional histogram-based space in order to define sub-spaces, which are used for image segmentation. Sub-spaces are further divided based on two criteria which lead to a multi-level segmentation approach. Dual-polarized TerraSAR-X data, both HH and VV, are used in a study area located in the southwestern United Kingdom.  相似文献   

Using geodetic GPS receivers to measure vegetation water content   总被引：1，自引：0，他引：1  

Wei Wan  Kristine M. Larson  Eric E. Small  Clara C. Chew  John J. Braun 《GPS Solutions》2015,19(2):237-248

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A new type of article for Terra Nova          下载免费PDF全文

Max Coleman  Jean Braun  Georges Calas  Carlo Doglioni  Klaus Mezger  Jason Phipps Morgan 《地学学报》2015,27(6):399-399

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Impact of three-dimensional attitude variations of an unmanned aerial vehicle magnetometry system on magnetic data quality     

Callum A. Walter  A. Braun  G. Fotopoulos 《Geophysical Prospecting》2019,67(2):465-479

Optically pumped vapour magnetometers have an orientation dependency in measuring the scalar component of the ambient magnetic field which leads to challenges for integration with mobile platforms. Quantifying the three-dimensional attitude variations (yaw, pitch and roll) of an optically pumped vapour magnetometer, while in-flight and suspended underneath a rotary unmanned aerial vehicle, aids in the successful development of reliable, high-resolution unmanned aerial vehicle magnetometry surveys. This study investigates the in-flight three-dimensional attitude characteristics of a GEM Systems Inc. GSMP-35U potassium vapour magnetometer suspended 3 m underneath a Dà-Jiāng Innovations S900 multi-rotor unmanned aerial vehicle. A series of unmanned aerial vehicle-borne attitude surveys quantified the three-dimensional attitude variations that a simulated magnetometer payload experienced while freely (or semi-rigidly) suspended underneath the unmanned aerial vehicle in fair weather. Analysis of the compiled yaw, pitch and roll data resulted in the design of a specialized semi-rigid magnetometer mount, implemented to limit magnetometer rotation about the yaw axis. A subsequent unmanned aerial vehicle-borne magnetic survey applying this specialized mount resulted in more than 99% of gathered GSMP-35U magnetic data being within industry standards. Overall, this study validates that maintaining magnetometer attitude variations within quantified limits (±5° yaw, ±10° pitch and roll) during flight can yield reliable, continuous and high-resolution unmanned aerial vehicle-borne magnetic measurements.  相似文献   

A Full-Sun Magnetic Index from Helioseismology Inferences     

I. González Hernández  M. Díaz Alfaro  K. Jain  W. K. Tobiska  D. C. Braun  F. Hill  F. Pérez Hernández 《Solar physics》2014,289(2):503-514

Solar magnetic indices are used to model the solar irradiance and ultimately to forecast it. However, the observation of such indices is generally limited to the Earth-facing hemisphere of the Sun. Seismic maps of the far side of the Sun have proven their capability to locate and track medium–large active regions at the non-visible hemisphere. We present here the possibility of using the average signal from these seismic far-side maps, combined with similarly calculated near-side maps, as a proxy to the full-Sun magnetic activity.  相似文献   

Buchbesprechungen     

Rudolf Braun  Hanspeter Woker  H. Ambübl 《Aquatic Sciences - Research Across Boundaries》1952,14(2):483-485

Ohne Zusammenfassung Technische Hochschule Karlsruhe  相似文献   

Calibration of JASON-1 Altimeter over Lake Erie     

C. Shum  Y. Yi  K. Cheng  C. Kuo  A. Braun  S. Calmant  D. Chambers 《Marine Geodesy》2003,26(3):335-354

This article describes absolute calibration results for both JASON-1 and TOPEX Side B (TSB) altimeters obtained at the Lake Erie calibration site, Marblehead, Ohio, USA. Using 15 overflights, the estimated JASON altimeter bias at Marblehead is 58 ± 38 mm, with an uncertainty of 19 mm based on detailed error analysis. Assuming that the TSB bias is negligible, relative bias estimates using both data from the TSB-JASON formation flight period and data from 48 water level gauges around the entire Great Lakes confirmed the Marblehead results. Global analyses using both the formation flight data and dual-satellite (TSB and JASON) crossovers yield a similar relative bias estimate of 146 ± 59 mm, which agrees well with open ocean absolute calibration results obtained at Harvest, Corsica, and Bass Strait (e.g., Watson et al. 2003). We find that there is a strong dependence of bias estimates on the choice of sea state bias (SSB) models. Results indicate that the invariant JASON instrument bias estimated oceanwide is 71 mm, with additional biases of 76 mm or 28 mm contributed by the choice of Collecte Localisation Satellites (CLS) SSB or Center for Space Research (CSR) SSB model, respectively. Similar analysis in the Great Lakes yields the invariant JASON instrument bias at 19 mm, with the SSB contributed biases at 58 mm or 13 mm, respectively. The reason for the discrepancy is currently unknown and warrants further investigation. Finally, comparison of the TOPEX/POSEIDON mission (1992-2002) data with the Great Lakes water level gauge measurements yields a negligible TOPEX altimeter drift of 0.1 mm/yr.  相似文献   

Numerical SPH analysis of debris flow run-out and related river damming scenarios for a local case study in SW China     

Anika Braun  Sabatino Cuomo  Stefano Petrosino  Xueliang Wang  Luqing Zhang 《Landslides》2018,15(3):535-550

A smoothed particle hydrodynamics (SPH) numerical modeling method implemented for the forward simulation of propagation and deposition of flow-type landslides was combined with different empirical geomorphological index approaches for the assessment of the formation of landslide dams and their possible evolution for a local case study in southwestern China. The SPH model was calibrated with a previously occurred landslide that formed a stable dam impounding the main river, and it enabled the simulation of final landslide volumes, and the spatial distribution of the resulting landslide deposits. At four different sites on the endangered slope, landslides of three different volumes were simulated, respectively. All landslides deposited in the main river, bearing the potential for either stable impoundment of the river and upstream flooding scenarios, or sudden breach of incompletely formed or unstable landslide dams and possible outburst floods downstream. With the empirical indices, none of the cases could be identified as stable formed landslide dam when considering thresholds reported in the literature, showing up the limitations of these indices for particular case studies of small or intermediate landslide volumes and the necessity to adapt thresholds accordingly for particular regions or sites. Using the occurred benchmark landslide as a reference, two cases could be identified where a complete blockage occurs that is more stable than the reference case. The other cases where a complete blockage was simulated can be considered as potential dam-breach scenarios.  相似文献