A New Estimate of the Best Value for the Solar Galactocentric Distance     

Bobylev  V. V.  Bajkova  A. T. 《Astronomy Reports》2021,65(6):498-506

Astronomy Reports - Using data from the literature, we made a list of individual estimates of the solar Galactocentric distance, which were performed after 2017 by different methods. These values...  相似文献   

Comparative Analysis of the Propagation Conditions of Millimeter Radio Waves at Radio Astronomy Polygons in Russia and Uzbekistan     

Bubukin  I. T.  Rakut  I. V.  Agafonov  M. I.  Yablokov  A. A.  Pankratov  A. L.  Gorbunova  T. Yu.  Gorbunov  R. V. 《Astronomy Reports》2021,65(7):598-614

Astronomy Reports - The feasibility of expanding the evaluation parameters was discussed when selecting the “Karadag” test site for the installation of millimeter-wave antennas based on...  相似文献   

Analysis of Photoelectric Occultations and Development of a Digital Model of the Lunar Libration Zone     

Churkin  K. O.  Nefedyev  Yu. A.  Andreev  A. O.  Demina  N. Yu.  Kronrod  E. V. 《Astronomy Reports》2021,65(7):580-587

Astronomy Reports - One of the priority tasks of modern astronomy is the observation and study of transient celestial processes, which also concerns photoelectric observations of lunar occultations...  相似文献   

Destruction of a Star during the Evolution of a Star + Supermassive Black Hole System     

Fedorova  A. V.  Tutukov  A. V. 《Astronomy Reports》2021,65(2):95-109

Astronomy Reports - Stars located closely to supermassive black holes (SMBHs) can, under certain conditions, form close binary systems with the SMBHs, in which the star may fill the Roche lobe and...  相似文献   

Investigation of Spectral Characteristics and Statistical Properties of Flicker Noise of the X-Ray Nova A0620-00     

Sazhina  O. S.  Bulygin  I. I.  Cherepashchuk  A. M. 《Astronomy Reports》2021,65(9):839-863

Astronomy Reports - Methodological studies of spectral characteristics and statistical analysis of flicker noise are presented on the example of two data samples (2016–2017) on the X-ray nova...  相似文献   

Backward automatic calibration for three-dimensional landslide models     

Giacomo Titti  Giulia Bossi  Gordon G.D.Zhou  Gianluca Marcato  Alessandro Pasuto 《地学前缘(英文版)》2021,12(1):231-241

Back-analysis is broadly used for approaching geotechnical problems when monitoring data are available and information about the soils properties is of poor quality.For landslide stability assessment back-analysis calibration is usually carried out by time consuming trial-and-error procedure.This paper presents a new automatic Decision Support System that supports the selection of the soil parameters for three-dimensional models of landslides based on monitoring data.The method considering a pool of possible solutions,generated through permutation of soil parameters,selects the best ten configurations that are more congruent with the measured displacements.This reduces the operator biases while on the other hand allows the operator to control each step of the computation.The final selection of the preferred solution among the ten best-fitting solutions is carried out by an operator.The operator control is necessary as he may include in the final decision process all the qualitative elements that cannot be included in a qualitative analysis but nevertheless characterize a landslide dynamic as a whole epistemological subject,for example on the base of geomorphological evidence.A landslide located in Northeast Italy has been selected as example for showing the system potentiality.The proposed method is straightforward,scalable and robust and could be useful for researchers and practitioners.  相似文献   

Late Neoarchean crustal growth under paired continental arc-back arc system in the North China Craton     

Xin He  Wei Wang  M. Santosh  Jiachen Yao  Kangting Gao  Yuhan Zhang  Denggang Lu  Lishuang Guo 《地学前缘(英文版)》2021,12(3):101120

The late Archean (~3.0–2.5 Ga) was a key period of continental growth globally, which is widely considered to reflect the onset of vigorous plate tectonic activity, although related continental growth modes remain contentious. Here we investigate a suite of late Neoarchean metavolcanic rocks from the southwest Qixia area of the Jiaobei terrane in the North China Craton. The rocks in this suite include amphibolites, clinopyroxene amphibolites, and hornblende plagioclase gneisses. We present zircon U-Pb isotopic data which indicate that the protoliths of these rocks formed during ~2549–2511 Ma.The (clinopyroxene) amphibolites correspond to meta-basaltic rocks, with some containing high modal content of titanite. These rocks show moderate to high FeO_T (8.96–13.62 wt.%) and TiO₂ (0.59–1.59 wt.%), flat to less fractionated REE patterns, and mildly negative Th, Nb, and Ta anomalies, resembling those of Fe-tholeiites. In addition, they display positive zircon ?_Hf(t) values (+2.6 to +8.7), and are devoid of crustal contamination or fractional crystallization. Combined with the low Nb/Yb (mostly < 1.60) and (Hf/Sm)_N (mostly < 0.95), low to moderate Th/Yb (0.08–0.54), and low V/Sc (5.53–9.19) ratios, these basaltic rocks are interpreted to have been derived from a relatively reduced and depleted mantle source that was mildly metasomatized by hydrous fluids. The hornblende plagioclase gneisses are meta-andesitic rocks, and occur interlayered with the basaltic rocks. They are transitional between tholeiitic and calc-alkaline rock series, and show fractionated REE patterns with evidently negative Th, Nb, and Ta anomalies. The depleted zircon ?_Hf(t) values (+2.4 to +8.4) and quantitative chemical modeling suggest that the andesitic rocks were most likely generated by injection and mixing of juvenile felsic magmas with the tholeiitic basaltic magmas.In general, the chemical features and genesis of late Neoarchean meta-basaltic rocks in our study area resemble those of Mariana back-arc basin basalts. Combined with regional geological data, it is proposed that the Jiaobei terrane witnessed late Neoarchean crustal growth under a paired continental arc-back arc setting. On a regional context, we propose two distinct geodynamic mode of late Neoarchean continental growth across North China Craton (particularly the Eastern Block), i.e., (1) arc-continent accretion along northwestern part of the Eastern Block; and (2) paired continental arc-back arc system surrounding the ~3.8–2.7 Ga continental nuclei to the southeast.  相似文献   

Metal-enriched nanoparticles and black carbon: A perspective from the Brazil railway system air pollution     

Bianca D. Lima  Elba C. Teixeira  James C. Hower  Matheus S. Civeira  Omar Ramírez  Cheng-Xue Yang  Marcos L.S. Oliveira  Luis F.O. Silva 《地学前缘(英文版)》2021,12(3):101129

Having a better understanding of air pollutants in railway systems is crucial to ensure a clean public transport. This study measured, for the first time in Brazil, nanoparticles (NPs) and black carbon (BC) on two ground-level platforms and inside trains of the Metropolitan Area of Porto Alegre (MAPA). An intense sampling campaign during thirteen consecutive months was carried out and the chemical composition of NPs was examined by advanced microscopy techniques. The results showed that highest concentrations of the pollutants occur in colder seasons and influenced by variables such as frequency of the trains and passenger densities. Also, internal and external sources of pollution at the stations were identified. The predominance of NPs enriched with metals that increase oxidative stress like Cd, Fe, Pb, Cr, Zn, Ni, V, Hg, Sn, and Ba both on the platforms and inside trains, including Fe-minerals as hematite and magnetite, represents a critical risk to the health of passengers and employees of the system. This interdisciplinary and multi-analytical study aims to provide an improved understanding of reported adverse health effects induced by railway system aerosols.  相似文献   

Pre-failure behaviour of reconstituted peats in triaxial compression     

Muraro  S.  Jommi  C. 《Acta Geotechnica》2021,16(3):789-805

This paper discusses the results of an experimental programme designed to investigate the deviatoric behaviour of peats. The results are obtained from triaxial experiments carried out on reconstituted peat samples. The interpretation of the experimental results follows a hierarchical approach in an attempt to derive the ingredients that an elastic–plastic model for peats should contain, including the yield locus, the hardening mechanism and the flow rule. The results obtained from stress tests along different loading directions show that purely volumetric hardening is not adequate to describe the deviatoric response of peat and that a deviatoric strain-dependent component should be included. The plastic deformation mechanism also depends on the previous stress history experienced by the sample. Stress and strain path dependence of the interaction mechanisms between the peat matrix and the fibres is discussed as a possible physical reason for the observed behaviour. This work offers a relevant set of data and information to guide the rational development and the calibration of constitutive laws able to model the deviatoric behaviour of peats.

  相似文献   

CPT correlations for thermal properties of soils     

Vardon  P. J.  Peuchen  J. 《Acta Geotechnica》2021,16(2):635-646

Acta Geotechnica - Obtaining in situ thermal properties of soils is often difficult and time-consuming. Here, cone penetration test (CPT) correlations are proposed and validated for thermal...  相似文献