Global coherence of GPS-measured high-frequency surface tremor motions     

Alexey Lyubushin 《GPS Solutions》2018,22(4):116

The traditional approach of GPS investigations is determining trends which are connected with the motion of tectonic plates. At the same time, a global GPS network provides the possibility of investigating statistical properties of high-frequency earth surface tremor in different parts of the world. Based on the results of coherence and correlation analysis of noise components of daily three-component GPS time series, representing measurements of earth surface displacements at 1097 stations, we have found that, during 2010–2011, there was a significant increase in the average level of noise coherence or correlation with dominant periods 7–9 days of surface tremor in nine regions of the earth, and in some of these regions, the average level of coherence or correlation is still high and does not return to the previous level. The increase of the average level of coherence and correlation could be detected on the graphs purely visually, while the middle time point of the time interval in which the ascending occurred is detected more precisely by a formal method based on the use of the Fisher’s ratio.  相似文献   

The Fe–C–O–H–N system at 6.3–7.8 GPa and 1200–1400 °C: implications for deep carbon and nitrogen cycles     

Alexander?G.?SokolEmail authorView author&#;s OrcID profile  Anatoly?A.?Tomilenko  Taras?A.?Bul’bak  Alexey?N.?Kruk  Pavel?A.?Zaikin  Ivan?A.?Sokol  Yurii?V.?Seryotkin  Yury?N.?Palyanov 《Contributions to Mineralogy and Petrology》2018,173(6):47

Interactions in a Fe–C–O–H–N system that controls the mobility of siderophile nitrogen and carbon in the Fe⁰-saturated upper mantle are investigated in experiments at 6.3–7.8 GPa and 1200–1400 °C. The results show that the γ-Fe and metal melt phases equilibrated with the fluid in a system unsaturated with carbon and nitrogen are stable at 1300 °C. The interactions of Fe₃C with an N-rich fluid in a graphite-saturated system produce the ε-Fe₃N phase (space group P6₃/mmc or P6₃22) at subsolidus conditions of 1200–1300 °C, while N-rich melts form at 1400 °C. At IW- and MMO-buffered hydrogen fugacity (fH₂), fluids vary from NH₃- to H₂O-rich compositions (NH₃/N₂?>?1 in all cases) with relatively high contents of alkanes. The fluid derived from N-poor samples contains less H₂O and more carbon which mainly reside in oxygenated hydrocarbons, i.e., alcohols and esters at MMO-buffered fH₂ and carboxylic acids at unbuffered fH₂ conditions. In unbuffered conditions, N₂ is the principal nitrogen host (NH₃/N₂?≤?0.1) in the fluid equilibrated with the metal phase. Relatively C- and N-rich fluids in equilibrium with the metal phase (γ-Fe, melt, or Fe₃N) are stable at the upper mantle pressures and temperatures. According to our estimates, the metal/fluid partition coefficient of nitrogen is higher than that of carbon. Thus, nitrogen has a greater affinity for iron than carbon. The general inference is that reduced fluids can successfully transport volatiles from the metal-saturated mantle to metal-free shallow mantle domains. However, nitrogen has a higher affinity for iron and selectively accumulates in the metal phase, while highly mobile carbon resides in the fluid phase. This may be a controlling mechanism of the deep carbon and nitrogen cycles.  相似文献   

From Craton to Shelf: example from the Barents Sea     

Alexey Shulgin  Rolf Mjelde  Jan Inge Faleide 《《地质学报》英文版》2018,92(Z1):105-105

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Room semantics inference using random forest and relational graph convolutional networks: A case study of research building     

Xuke Hu  Hongchao Fan  Alexey Noskov  Zhiyong Wang  Alexander Zipf  Fuqiang Gu  Jianga Shang 《Transactions in GIS》2021,25(1):71-111

Semantically rich maps are the foundation of indoor location‐based services. Many map providers such as OpenStreetMap and automatic mapping solutions focus on the representation and detection of geometric information (e.g., shape of room) and a few semantics (e.g., stairs and furniture) but neglect room usage. To mitigate the issue, this work proposes a general room tagging method for public buildings, which can benefit both existing map providers and automatic mapping solutions by inferring the missing room usage based on indoor geometric maps. Two kinds of statistical learning‐based room tagging methods are adopted: traditional machine learning (e.g., random forests) and deep learning, specifically relational graph convolutional networks (R‐GCNs), based on the geometric properties (e.g., area), topological relationships (e.g., adjacency and inclusion), and spatial distribution characteristics of rooms. In the machine learning‐based approach, a bidirectional beam search strategy is proposed to deal with the issue that the tag of a room depends on the tag of its neighbors in an undirected room sequence. In the R‐GCN‐based approach, useful properties of neighboring nodes (rooms) in the graph are automatically gathered to classify the nodes. Research buildings are taken as examples to evaluate the proposed approaches based on 130 floor plans with 3,330 rooms by using fivefold cross‐validation. The experiments conducted show that the random forest‐based approach achieves a higher tagging accuracy (0.85) than R‐GCN (0.79).  相似文献   

Supercritically accreting stellar mass black holes as ultraluminous X-ray sources     

Juri Poutanen  Galina Lipunova  Sergei Fabrika  Alexey G. Butkevich  Pavel Abolmasov 《Monthly notices of the Royal Astronomical Society》2007,377(3):1187-1194

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L‐chondrite asteroid breakup tied to Ordovician meteorite shower by multiple isochron 40Ar‐39 Ar dating     

Ekaterina V. KOROCHANTSEVA  Mario TRIELOFF  Cyrill A. LORENZ  Alexey I. BUYKIN  Marina A. IVANOVA  Winfried H. SCHWARZ  Jens HOPP  Elmar K. JESSBERGER 《Meteoritics & planetary science》2007,42(1):113-130

Abstract— Radiochronometry of L chondritic meteorites yields a rough age estimate for a major collision in the asteroid belt about 500 Myr ago. Fossil meteorites from Sweden indicate a highly increased influx of extraterrestrial matter in the Middle Ordovician ～480 Myr ago. An association with the L‐chondrite parent body event was suggested, but a definite link is precluded by the lack of more precise radiometric ages. Suggested ages range between 450 ± 30 Myr and 520 ± 60 Myr, and can neither convincingly prove a single breakup event, nor constrain the delivery times of meteorites from the asteroid belt to Earth. Here we report the discovery of multiple ⁴⁰Ar‐³⁹Ar isochrons in shocked L chondrites, particularly the regolith breccia Ghubara, that allow the separation of radiogenic argon from multiple excess argon components. This approach, applied to several L chondrites, yields an improved age value that indicates a single asteroid breakup event at 470 ± 6 Myr, fully consistent with a refined age estimate of the Middle Ordovician meteorite shower at 467.3 ± 1.6 Myr (according to A Geologic Time Scale 2004). Our results link these fossil meteorites directly to the L‐chondrite asteroid destruction, rapidly transferred from the asteroid belt. The increased terrestrial meteorite influx most likely involved larger projectiles that contributed to an increase in the terrestrial cratering rate, which implies severe environmental stress.  相似文献   

CAD Tool Simulates and Evaluates GPS Receiver Designs     

Michael Vorobiev  Alexey Zhdanov  Mark Zhodzishsky  Javad Ashjaee 《GPS Solutions》2000,4(1):13-20

A new computer-aided design (CAD) program called Falcon 3.0 has been created to simulate and evaluate receiver designs. This CAD tool aims to solve tasks at the design stage of navigation receivers that operate with signals from Navigational Satellite Time and Ranging (NAVSTAR) and Global Navigational Satellite System (GLONASS). Specific tasks include: · Defining the receiver frequency plan (frequencies of oscillators and filters that guarantee accuracy of the receiver) · Specifying parameters for the digital processing of received signal · Computing interpath and interchannel biases · Computing statistical characteristics of correlation signals I, Q, dl, and dQ · Calculating noise and multipath errors of measurements · Determeining energy losses This CAD tool has been used in the design of receivers such as Javad Positioning Systems (JPS) Legacy, Regency, Odyssey, and Eurocard and in the prediction of their accuracy. It has been shown that experimental and predicted data agree well. ? 2000 John Wiley & Sons, Inc.  相似文献   

Interannual variability of Mars global dust storms: an example of self-organized criticality?     

Alexey A Pankine  Andrew P Ingersoll 《Icarus》2004,170(2):514-518

Previous simulations of martian global dust storms with a simple low-order model showed the desired interannual variability of storms if one of the model parameters—the threshold wind speed for starting saltation and lifting dust from the surface—was finely tuned. In this paper we show that the fine-tuning of this parameter could be the result of negative feedback in which processes associated with global dust storms raise the threshold and small-scale processes like dust devils, which are active in years between the storms, lower the threshold.  相似文献   

GIS-Supported Airfield Selection near Zhongshan Station,East Antarctica,based on Multi-Mission Remote Sensing Data     

Xiangbin Cui  Jiaxin Liu  Bo Sun  Alexey Markov 《Marine Geodesy》2013,36(5):422-446

Abstract

As Antarctica attracts increasing attention in global climate change studies, the demand for field expeditions has increased in recent decades. Aircraft has become the most efficient mode of transportation because of the advantages of short travel times over long distances, access to unreachable locations and capability to carry different types of sensors to obtain large areal coverages. However, few studies have been published regarding Antarctic airfield site selection for heavy-wheeled aircraft. In this paper, we present methods and results of blue-ice airfield preliminary selection near Zhongshan station, East Antarctica. The geographic information system (GIS)-based method is supported by multi-mission high-resolution images from the ZY-3, WorldView-2 and Landsat-8 satellites along with existing remote sensing products. Ground truth observations were integrated with satellite panchromatic and spectral information to identify runway candidate areas. The information inferred by remote sensing data, including firn type, ice movement, surface slope and ice fracture, is used for evaluation of the airfield selection rules. Finally, the rankings and recommendations of runway candidates were performed in a GIS analysis environment. The site selection approach developed in this paper can be applied in preconstruction studies of other similar cryosphere environments to provide appropriate candidates for a final stage field investigation.  相似文献   

Lake-margin ecosystems of saline lakes of the Borzya group （Zabaikalsky Krai,Russia） during the initial filling phase   总被引：1，自引：0，他引：1  

Evgenia R GORLACHEVA Gazhit Ts. TSYBEKMITOVA Alexey V. AFONIN Natalya A. TASHLIKOVA Ekaterina Yu. AFONINA Alexey P. KUKLIN Natalia V. SALTANOVA 《中国海洋湖沼学报》2014,32(4):871-878

This article presents the results ofhydrochemical and hydrobiological studies of shallow saline lakes of the Borzya group （Zabaikalsky K_rai, Russia） at the initial filling phase. The lake-margin ecosystems of the studied lakes are characterized by varying degrees of salinity from polyhaline to brine water. Cyclical variations of meteorological conditions and high salinity determined that the compositions of the aquatic organisms are specific, mostly between stenohaline and euryhaline species, the quantities are low, and the community structures are simple.  相似文献