DME/TACAN interference mitigation for GNSS: algorithms and flight test results     

Grace Xingxin Gao  Liang Heng  Achim Hornbostel  Holmer Denks  Michael Meurer  Todd Walter  Per Enge 《GPS Solutions》2013,17(4):561-573

The Galileo E5a/E5b signals and the Global Positioning System (GPS) L5 signal lie within the aeronautical radionavigation services (ARNS) band. They suffer interference from the services in this frequency band, in particular, pulsed signals from distance measuring equipment (DME) and tactical air navigation (TACAN) systems. To maintain system accuracy and integrity, interference mitigation is beneficial and necessary. We first present the real DME/TACAN environment at Stanford, CA as an example to illustrate the need for mitigating DME/TACAN interference. We then propose a time and frequency joint mitigation algorithm—Hybrid Blanking and its simplified version, frequency domain adaptive filtering (FDAF) for hardware implementation. Finally, a flight measurements campaign was performed over a European DME/TACAN hotspot near Frankfurt, Germany, to record a worst-case DME interference environment. Recorded data from the flight tests mixed with injected GNSS signals verify the effectiveness of the proposed mitigation algorithm.  相似文献   

Evidence of the North Atlantic Oscillation in varve composition and diatom assemblages from recent, annually laminated sediments of Lake Belau, northern Germany     

Jürgen Zahrer  Stefan Dreibrodt  Achim Brauer 《Journal of Paleolimnology》2013,50(2):231-244

The recent sediment record of Lake Belau (Schleswig–Holstein, Germany), deposited in the period 1945–2002, was compared with instrumental meteorological and limnological data. The sediments deposited during this period are annually laminated. A varve chronology was established and supported by ¹³⁷Cs measurements. Micro-facies and diatom assemblage composition analyses were confirmed in thin sections and compared statistically with limnological and meteorological data. Comparison of phytoplankton data with diatom assemblage data from the sediment for the time interval from 1988 to 1999 proved that the sediments reflect limnological processes in the lake and record seasonal changes in the primary producer communities. Among the climatological data, the number of contiguous ice days (days with maximal temperatures ≤0 °C) and the state of the winter NAO are strong predictors for micro-facies development and diatom assemblage composition. Furthermore, solar and local (nutrient input) influences are visible in the diatom assemblage compositions. Our study illustrates the high potential for using analyses of micro-facies and diatom assemblages to reconstruct past weather conditions in varved sediments of Lake Belau.  相似文献   

Astrodynamical Space Test of Relativity Using Optical Devices I (ASTROD I)—A class-M fundamental physics mission proposal for Cosmic Vision 2015–2025     

Thierry Appourchaux  Raymond Burston  Yanbei Chen  Michael Cruise  Hansjörg Dittus  Bernard Foulon  Patrick Gill  Laurent Gizon  Hugh Klein  Sergei Klioner  Sergei Kopeikin  Hans Krüger  Claus Lämmerzahl  Alberto Lobo  Xinlian Luo  Helen Margolis  Wei-Tou Ni  Antonio Pulido Patón  Qiuhe Peng  Achim Peters  Ernst Rasel  Albrecht Rüdiger  Étienne Samain  Hanns Selig  Diana Shaul  Timothy Sumner  Stephan Theil  Pierre Touboul  Slava Turyshev  Haitao Wang  Li Wang  Linqing Wen  Andreas Wicht  Ji Wu  Xiaomin Zhang  Cheng Zhao 《Experimental Astronomy》2009,23(2):491-527

ASTROD I is a planned interplanetary space mission with multiple goals. The primary aims are: to test general relativity with an improvement in sensitivity of over three orders of magnitude, improving our understanding of gravity and aiding the development of a new quantum gravity theory; to measure key solar system parameters with increased accuracy, advancing solar physics and our knowledge of the solar system; and to measure the time rate of change of the gravitational constant with an order of magnitude improvement and the anomalous Pioneer acceleration, thereby probing dark matter and dark energy gravitationally. It is an international project, with major contributions from Europe and China and is envisaged as the first in a series of ASTROD missions. ASTROD I will consist of one spacecraft carrying a telescope, four lasers, two event timers and a clock. Two-way, two-wavelength laser pulse ranging will be used between the spacecraft in a solar orbit and deep space laser stations on Earth, to achieve the ASTROD I goals. A second mission, ASTROD (ASTROD II) is envisaged as a three-spacecraft mission which would test General Relativity to 1 ppb, enable detection of solar g-modes, measure the solar Lense–Thirring effect to 10 ppm, and probe gravitational waves at frequencies below the LISA bandwidth. In the third phase (ASTROD III or Super-ASTROD), larger orbits could be implemented to map the outer solar system and to probe primordial gravitational-waves at frequencies below the ASTROD II bandwidth.

Wei-Tou NiEmail:

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Global methane emission through mud volcanoes and its past and present impact on the Earth's climate   总被引：4，自引：0，他引：4  

Achim?J.?KopfEmail author 《International Journal of Earth Sciences》2003,92(5):806-816

Mud volcanism is an abundant, global phenomenon whereby fluid-rich, low-density sediments extrude both on land and offshore. Methane, which generally exceeds 90 vol% of the gas phase, is emitted at high rates during and after emplacement of the mud domes and is known for its high global warming potential (GWP). This comprehensive estimate of the annual contribution of mud volcano degassing assesses the significance of mud volcanism for the accumulation of greenhouse gases in the atmosphere. A first-order estimate for the earlier, pre-anthropogenic volume of methane released through mud volcanoes further supports their profound effect on the Earth's climate since at least the Paleozoic (570 Ma).  相似文献   

Human impact and soil erosion during the last 5000 yrs as recorded in lacustrine sedimentary organic matter at Lac d'Annecy, the French Alps   总被引：2，自引：0，他引：2  

Hervé Noël  Emmanuel Garbolino  Achim Brauer  Elisabeth Lallier-Vergès  Jacques-Louis de Beaulieu  Jean-Robert Disnar 《Journal of Paleolimnology》2001,25(2):229-244

Sedimentary organic matter has been systematically studied in an eight-metre long core from the centre of the Petit Lac (Annecy, French Alps). The palynofacies composition identifies different terrestrial organic sources including forest floors, soil-horizons and geological substratum. The amount of recycled organic matter derived from the geological substratum is estimated and subtracted from the other contributions from the catchment area. The palynological record indicates that the relative variations in organic sources are directly dependent on human land-use. From ca. 5000 to 1700 BP, the human impact on soil cohesion is very low and organic matter is mainly exported from the surficial forest floor. The Roman invasion (ca. 1700 BP) marks the most important ecological and hydrological change. From 1700 to 900 BP, the clearing of forests released deeper-soil components. This trend is increased after 900 BP with agriculture intensification, which resulted in a higher sedimentation rate. In all the periods, extreme events such as flood or intensive run-off are characterised by notable increases of organic matter from surface (5000 to 1700 BP) and deep (1700 BP to now) soils.  相似文献   

Granulite-facies metabasite ejecta in the Laacher See area,Eifel, West Germany     

Martin Okrusch  Bernd Schröder  Achim Schnutgen 《Lithos》1979,12(4):251-270

Near the village of Engeln, Laacher See area, garnet-bearing pyriclasite and pyribolite ejecta were recognized as constituents of alkaline basaltic tuffs; they are interpreted as fragments of the lowermost crust. During the first main stage of granulite facies metamorphism, assemblages with garnet (Alm₄₇Pyr₃₄Spess₂Gross + Andr₁₇), clinopyroxene (Wo₃₇En₃₅Fs₁₅Ts_8.5Jd_4.5), orthopyroxene I (En₃₄Fs₃₈Ts₄Jd₂), and plagioclase I (An₄₀-An₆₀) were formed in a temperature range of 730–850°C and rock pressures somewhere between 6.5 and 12 kb, $\text{P}{}_{\mathrm{tot}}\text{>}\text{P}{}_{\mathrm{<mtext>H</mtext>}}{}_2\text{O}\text{> 0}$. The rare sulfate-rich meionite, and at least a part of the ubiquitous brown hornblende were presumably also formed during this stage. A retrograde metamorphic event under slightly lower pressures and temperatures led to the breakdown of the assemblage garnet + clinopyroxene thereby forming coronas of plagioclase II $\text{(}\text{An}{}_{75}\text{) +}\text{orthopyroxene}\text{II +}\text{Ti-magnetite}\text{±}\text{brown hornblende}$.  相似文献   

Cross-section through the frontal Japan Trench subduction zone: Geochemical evidence for fluid flow and fluid–rock interaction from DSDP and ODP pore waters and sediments     

Annette Deyhle  Achim Kopf  Sabine Pawlig 《Island Arc》2004,13(1):271-288

Abstract Fluids and sediments from Deep Sea Drilling Project/Ocean Drilling Program Legs (56, 57, 87 and 186) along a transect extending from the subducting plate, across the midslope and upper slope of the Japan Trench forearc were analyzed for B and B isotopes in order to assess their composition and fluid–sediment interaction. At the reference Site 436 on the subducting plate, changes in B contents and B isotopes are controlled by the lithology and diagenesis only. The midslope Sites 440 and 584 showed stronger variations in the B geochemistry, which can be related to diagenesis and tectonic dewatering along faults. The strongest changes in the B geochemistry were observed on the upper slope Sites 1150 and 1151, where profound down‐hole freshening (chlorinities as low as ～310 mmol) coincides with a B enrichment (up to 9.3 × seawater concentration). The B isotope pore fluid profile of Site 1150 displayed a bimodal variation with depth, first increasing to values more positive than seawater, then shifting to lower signatures typical for deep‐seated fluids, whereas Site 1151 showed a constant B decrease with depth. Sites 1150 and 1151 sediments showed B increases with depth to values as high as ～164 p.p.m. and isotopic compositions ranging from ～+4 to ?9‰. A linear decrease in B_solid/B_fluid ratio, suggests that B geochemistry of the upper slope sites is controlled by fluid–rock interaction and deep‐seated fluid flow, whereas constant B_solid/B_fluid ratios were observed at the reference site on the incoming plate. This fluid overprint is probably caused by normal faults in the sediment cover which might be interconnected to deep thrusts in the underlying Cretaceous accreted wedge. This suggests that the erosive Japan Trench margin is characterized by back‐flux of deep‐seated, B‐enriched fluids into the ocean, which is facilitated by extensional normal faulting as a result of tectonic erosion and subsidence.  相似文献   

Geomorphic Effects of the Extreme Rainfall Event of 20–21 July, 2004 in the Latnjavagge Catchment, Northern Swedish Lapland     

Achim A. Beylich  Olga Sandberg 《Geografiska Annaler: Series A, Physical Geography》2005,87(3):409-419

Mass transfers triggered by a rare rainfall event on 20–21 July, 2004, with 58.4 mm of rain within 24 h and 71.7 mm of rain within 48 h in the Latnjavagge catchment (9 km² , 950–1440 m a.s.l.; 68°20'N, 18°30'E) in the higher Abisko mountain region (Swedish Lapland), are quantified and analysed in direct comparison with mean annual mass transfers in this drainage basin. In years without rare rainfall events the Latnjavagge catchment is characterized by restricted sediment availability resulting in low mechanical denudation and mass transfers. During the rare rainfall event of 20–21 July, 2004, major stability thresholds on the slope systems (triggering debris flows and slides) and in the channel systems (break‐up of channel debris pavements and step–pool systems) in the Latnjavagge catchment were passed and mass transfers by debris flows, slides and fluvial debris transport in creeks and channels were several times higher than the mean annual mass transfers in Latnjavagge. In the calculation of longer‐term mass transfers and sediment budgets, rare events like the 20–21 July, 2004 rainfall event have to be considered as essential components. A reliable estimation of the recurrence intervals of such rare events is especially problematic. The general problem of defining an adequate length of process monitoring programmes is pointed out.  相似文献   

Water chemistry and its diversity in relation to local factors in the Latnjavagge drainage basin, arctic–oceanic Swedish Lapland     

Achim A. Beylich  Else Kolstrup  Tage Thyrsted  Dorothea Gintz 《Geomorphology》2004,58(1-4):125-143

The chemistry of precipitation, snow pack and surface water has been analysed on 205 samples collected during the 2001 field season at 25 selected sites within the Latnjavagge drainage basin in arctic–oceanic northern Swedish Lapland. Additionally, daily discharge and yield of dissolved solids have been calculated for several subcatchments and the entire Latnjavagge catchment during the years 2000, 2001 and 2002. Chemical water analysis included the components Ca²⁺, Mg²⁺, Na⁺, K⁺, Fe²⁺, Mn²⁺, Cl⁻, NO₃⁻, SO₄²⁻ and PO₄³⁻, with SO₄²⁻ and Ca²⁺ being the dominant ones in the surface water. Solute concentrations and chemical denudation were low, but showed significant differences within the basin. In areas of shade, longer snow cover, frozen ground and thin regolith, concentrations over the summer were perceptible but so low that solutes brought into the basin from precipitation could be detected in the surface water. In one locality, it was even found that lake water could reflect snowmelt to such an extent that the solute concentration was less than that of summer precipitation. The highest concentrations were found at a radiation-exposed, W-facing, vegetated, moderately steep slope with relatively thick regolith that was thawed at the time of snowmelt in early June. In such well-drained sites with continuous subsurface water flow, a maximum of contact between water and mineral particles could take place. The concentration values revealed differences in the rate of thawing of frozen ground between shaded areas and/or areas at higher altitude on the one hand and radiation-exposed areas on the other. A comparison with published results from Kärkevagge a few kilometres to the northwest as well as from other periglacial locations indicates that the chemical denudation values from Latnjavagge are more representative of periglacial oceanic environments than the values from the Kärkevagge catchment, which shows especially high chemical denudation rates. The investigation in Latnjavagge stresses the importance of spatial variability within even small catchments of homogeneous lithology as it demonstrates that solute concentrations from different subbasins can differ substantially dependent on exposure to radiation, duration of snow cover and frozen ground conditions, regolith thickness and possibly also to vegetation cover and slope angle as factors steering water turbulence and retention of drainage.  相似文献   

Thermodynamic calculations of ice production in the northern Baltic proper     

Achim Stössel 《Ocean Dynamics》1985,38(6):261-284

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