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L. I. Abalkin 《Water Resources》2006,33(6):713-714
Chronicles
In memory of G.P. Kalinin (1916–1975) 相似文献2.
Fabio Mazza 《地震工程与结构动力学》2019,48(4):432-453
The out-of-plane (OOP) behaviour of masonry infills (MIs), inserted in reinforced concrete (r.c.)–framed buildings, is recognized as one of the most important failure modes of this nonstructural element during an earthquake, which may be a consequence of simultaneous or prior in-plane (IP) damage. A five-element macro-model, with four diagonal OOP non-linear beams and one horizontal IP non-linear truss, with an equivalent mass of the infill panel divided between two central nodes, takes into account the IP and OOP failure modes occurring in the event of seismic loading. Pivot hysteretic models predict the non-linear IP and OOP force-displacement laws of the infill panel, based on geometrical rules defining loading and unloading branches. Firstly, a calibration of the proposed IP-OOP interaction model of MIs is carried out considering full-scale experimental results of traditional masonry typologies. Each specimen is initially subjected to in-plane quasi-static cyclic loading, until a maximum drift is reached, and then one-sided OOP cycles are imposed pushing in the horizontal direction and back to zero force. Then a numerical investigation considers masonry infills of an existing six-storey r.c.-framed building designed in compliance with a former Italian seismic code. To evaluate the interaction, the results of simultaneous IP and OOP cyclic tests on MIs at the top, intermediate, and lowest levels of the test structure are presented, assuming different displacement histories: (1) OOP loading faster than IP, at the sixth storey; (2) equal IP and OOP loading, at the third storey; (3) IP loading faster than OOP, at the first storey. Finally, attention is focused on the contribution of masonry infills to the IP and OOP energy dissipation of r.c.-framed structures. 相似文献
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M. A. BENSON 《水文科学杂志》2013,58(3):5-6
Abstract This study was made to define the relation between floods in a humid region and the causative factors that account for their variability. The study covered the basic relationships between peak discharges and hydrologic factors as well as the practical working methods for generalizing the results on a regional basis. Statistical multiple-correlation techniques were applied to hydrologic data in New England. A field and library investigation of historical flood data extended the period of flood knowledge to as much as 300 years. The relation of many topographic and climatic factors to flood peaks was tested. Flood peaks with recurrence intervals at 9 levels, from 1.2 to 300 years, were related to 6 independent variables, 3 of which are topographic, 2 climatic, and 1 orographic. 相似文献
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Five ground-tilt stations were established on the flanks of the Soufriere of St. Vincent; two in 1977, two in 1980, and one in 1983. Four of these stations have survived; two consist of lines oriented radially to the volcano, and the other two consist of cross-shaped arrays. Collectively, this network showed that the volcano inflated gradually before the eruption of 1979 and then deflated rapidly during the eruption and for about a year after it had ended. The volcano then reinflated during much of 1981 and inflated only slightly, if at all, during the 7-year period 1982–1989. The measured amount of ground tilt from 1977 to 1989 was relatively small; the maximum recorded change of radial tilt at a station 6.5 km from the summit of the volcano totaled about 20 rad. Local seismicity correlates well with measured ground deformation: numerous earthquakes accompanied the 1979–1981 deflation/inflation cycle; relatively few earthquakes occurred during the 1982–1989 period of little or no ground deformation. In the hope that the experience we have gained might be of use to others who are considering a program of ground-tilt monitoring on volcanoes elsewhere in the humid tropics, we describe many practical aspects of our program that have evolved over the years. For example: (1) stainless steel bench marks cemented into solid bedrock appear to be stable for at least 12 years, (2) bench marks can be located in concrete-filled drums where bedrock is absent, (3) bench marks should be concealed to protect them from vandalism, (4) care must be exercised where sight lines graze the ground (<0.5 m), and (5) automatic levels are preferable because of their efficiency of operation, especially with inexperienced personnel. 相似文献
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We analyse the seismic catalogue of the local earthquakes which occurred at Somma-Vesuvius volcano in the past three decades (1972–2000). The seismicity in this period can be described as composed of a background level, characterised by a low and rather uniform rate of energy release and by sporadic periods of increased seismic activity. Such relatively intense seismicity periods are characterised by energy rates and magnitudes progressively increasing in the critical periods. The analysis of the b value in the whole period evidences a well-defined pattern, with values of b progressively decreasing, from about 1.8 at the beginning of the considered period, to about 1.0 at present. This steady variation indicates an increasing dynamics in the volcanic system. Within this general trend it is possible to identify a substructure in the time sequence of the seismic events, formed by the alternating episodes of quiescence and activity. The analysis of the source moment tensor of the largest earthquakes shows that the processes at the seismic source are generally not consistent with simple double-couples, but that they are compatible with isotropic components, mostly indicating volumetric expansion. These components are shown to be statistically significant for most of the analysed events. Such focal mechanisms can be interpreted as the effect of explosion phenomena, possibly related to volatile exsolution from the crystallising magma. The availability of a reduced amount of high quality data necessary for the inversion of the source moment tensor, the still limited period of systematic observation of Vesuvius micro-earthquakes and, above all, the absence of eruptive events during such interval of time, cannot obviously permit the outlining of any formal premonitory signal. Nevertheless, the analysis reported in this paper indicates a progressively evolving dynamics, characterised by a generally increasing trend in the seismic activity in the volcanic system and by a significant volumetric component of recent major events, thus posing serious concern for a future evolution towards eruptive activity. 相似文献
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The July–August 2001 eruption of Mt. Etna stimulated widespread public and media interest, caused significant damage to tourist facilities, and for several days threatened the town of Nicolosi on the S flank of the volcano. Seven eruptive fissures were active, five on the S flank between 3,050 and 2,100 m altitude, and two on the NE flank between 3,080 and 2,600 m elevation. All produced lava flows over various periods during the eruption, the most voluminous of which reached a length of 6.9 km. Mineralogically, the 2001 lavas fall into two distinct groups, indicating that magma was supplied through two different and largely independent pathways, one extending laterally from the central conduit system through radial fissures, the other being a vertically ascending eccentric dike. Furthermore, one of the eccentric vents, at 2,570 m elevation, was the site of vigorous phreatomagmatic activity as the dike cut through a shallow aquifer, during both the initial and closing stages of the eruption. For 6 days the magma column feeding this vent was more or less effectively sealed from the aquifer, permitting powerful explosive and effusive magmatic activity. While the eruption was characterized by a highly dynamic evolution, complex interactions between some of the eruptive fissures, and changing eruptive styles, its total volume (~25×10 6 m 3 of lava and 5–10×10 6 m 3 of pyroclastics) was relatively small in comparison with other recent eruptions of Etna. Effusion rates were calculated on a daily basis and reached peaks of 14–16 m 3 s -1, while the average effusion rate at all fissures was about 11 m 3 s -1, which is not exceptionally high. The eruption showed a number of peculiar features, but none of these (except the contemporaneous lateral and eccentric activity) represented a significant deviation from Etna's eruptive behavior in the long term. However, the 2001 eruption could be but the first in a series of flank eruptions, some of which might be more voluminous and hazardous. Placed in a long-term context, the eruption confirms a distinct trend, initiated during the past 50 years, toward higher production rates and more frequent eruptions, which might bring Etna back to similar levels of activity as during the early to mid seventeenth century. 相似文献
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The purpose of this study is the evaluation of dynamic behavior induced by seismic activity on a silo system, containing bulk material, with a soil foundation. The interaction effects between the silo and bulk material, as well as the effects produced between the foundation of the silo and the soil, were taken into account. Proposed simplified approximation, as well as the finite model, were used for analysis. The results, from the presented approximation, were compared with a more rigorous obtainment method. Initially, the produced simplified approximation, with elastic material assumption for the grain, could determine the pressures on the dynamic material along with displacements along the height of the silo wall and base shear force, etc., with remarkable precision. Some comparisons, via a change of soil and/or foundation conditions, were also made regarding the seismic pressure of the dynamic material pressure, displacement and base shear forces for both squat and slender silos. Comparing the analytical predictions to results from the numerical simulations produced good results. It can be concluded that the model can be used effectively to perform a broad suite of parametric studies, not only at the design stage but also as a reliable tool for predicting system behavior under the limit state of the system. The results and comprehensive analysis show that displacement effects and base shear forces generally decreased when soil was softer; however, soil structure interaction (SSI) did not have any considerable effects on squat silos and therefore need not be taken into practice. 相似文献
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The results of a periodogramanalysis of the variations in the ionospheric parameters, measured using the vertical radio sounding
method at midlatitude Irkutsk observatory (Eastern Siberia), are presented. The 1984–1986 period of observations was used.
It has been indicated that the statistically significant oscillations with periods typical of planetary waves are present
in the variations in f
0Es, f
bEs, h′Es, f
min, f
0F2, and h′F. 相似文献
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D. S. Kotova M. V. Klimenko V. V. Klimenko V. E. Zakharov 《Geomagnetism and Aeronomy》2017,57(3):288-300
A study of HF wave propagation in the three-dimensional inhomogeneous ionosphere has been carried out in an approximation of geometrical optics. The three-dimensional medium of radio wave propagation is considered to be inhomogeneous, absorbing, and anisotropic due to the influence of the geomagnetic field. The parameters of the medium are described by the results of calculations on the basis of the Global Self-Consistent Model of the Thermosphere, Ionosphere, and Protonosphere (GSM TIP). The propagation of radio waves in the equatorial, middle-, and high-latitude ionosphere was studied. Comparisons of the ray trajectories, integral attenuation, deviations of the projection of radio wave trajectories onto the Earth’s surface from the great-circle arc, and the behavior of the angle between the wave phase and wave energy directions, as well as the angle between the direction of propagation and the external magnetic field obtained for quiet and disturbed conditions, have been performed. We consider a geomagnetic storm that occurred in 2011, with the main storm phase occurring on September 26, and the day after geomagnetic disturbances, September 29, as disturbed conditions in the ionosphere. 相似文献
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Nachasova I. E. Pilipenko O. V. Tsetlin Yu. B. 《Izvestiya Physics of the Solid Earth》2022,58(2):203-215
Izvestiya, Physics of the Solid Earth - Abstract—Archaeomagnetic studies have been carried out for the ceramics from cultural deposits of multilayered archaeological monuments Sakhtysh I and... 相似文献
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Geomagnetism and Aeronomy - The results of reconstruction of the heliospheric modulation potential based on radiocarbon data for the time interval 17 000–5000 years B.C. are presented.... 相似文献
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N. Gopalswamy S. Akiyama S. Yashiro G. Michalek R.P. Lepping 《Journal of Atmospheric and Solar》2009,71(8-9):1005-1009
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Izvestiya, Physics of the Solid Earth - Abstract—Dynamics of complex plasma structures, that drive precipitation and current systems into the ionosphere, produce a multitude of physical and... 相似文献