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91.
The aim of this paper is to illustrate the results of a preliminary study on aerial landslide-generated waves, which has been mainly intended to establish a method for analyzing water surface records. Some simple physical experiments, reproducing the Scott Russell's wave generator, were carried out in a small two-dimensional wave flume; the Wavelet Transform (WT) is applied to analyze wave measurements and it is shown that useful information can be obtained by means of this technique. The celerity of impulsively generated waves, reflection by an overflow structure and seiching phenomena of the flume are studied. A discussion of the results along with some remarks about ongoing research is also given. 相似文献
92.
Matteo Correnti Francesco Paresce Rossella Aversa Giacomo Beccari Guido De Marchi Marcella Di Criscienzo Xiaoying Pang Loredana Spezzi Elena Valenti Paolo Ventura 《Astrophysics and Space Science》2012,340(2):263-279
We have used new, deep, visible and near infrared observations of the compact starburst cluster in the giant HII region NGC 3603 and its surroundings with the WFC3 on HST and HAWK-I on the VLT to study in detail the physical properties of its intermediate mass (∼1–3 M⊙) stellar population. We show that after correction for differential extinction and actively accreting stars, and the study of field star contamination, strong evidence remains for a continuous spread in the ages of pre-main sequence stars in the range ∼2 to ∼30 Myr within the temporal resolution available. Existing differences among presently available theoretical models account for the largest possible variation in shape of the measured age histograms within these limits. We also find that this isochronal age spread in the near infrared and visible Colour-Magnitude Diagrams cannot be reproduced by any other presently known source of astrophysical or instrumental scatter that could mimic the luminosity spread seen in our observations except, possibly, episodic accretion. The measured age spread and the stellar spatial distribution in the cluster are consistent with the hypothesis that star formation started at least 20–30 Myrs ago progressing slowly but continuously up to at least a few million years ago. All the stars in the considered mass range are distributed in a flattened oblate spheroidal pattern with the major axis oriented in an approximate South-East–North-West direction, and with the length of the equatorial axis decreasing with increasing age. This asymmetry is most likely due to the fact that star formation occurred along a filament of gas and dust in the natal molecular cloud oriented locally in this direction. 相似文献
93.
Mesenbet Yibeltal Atsushi Tsunekawa Nigussie Haregeweyn Enyew Adgo Derege Tsegaye Meshesha Tsugiyuki Masunaga Mitsuru Tsubo Paolo Billi Kindiye Ebabu Mulatu Liyew Berihun 《地球表面变化过程与地形》2021,46(6):1209-1222
Gully erosion is a major cause of soil loss and severe land degradation in sub-humid Ethiopia. The objective of this study was to investigate the role and the effect of subsurface water level change on gully headcut retreat, gully formation and expansion in high rainfall tropical regions in the Ethiopian highlands. During the rainy seasons of 2017–2019, the expansion rate of 16 fixed gullies was measured and subsurface water levels were measured by piezometers installed near gully heads. During the study period, headcut retreats ranged from 0.70 to 2.35 m, with a mean value of 1.49 ± 0.56 m year−1, and average depth of the surface water level varied between 1.12 and 2.82 m, with a mean value of 2.62 m. Gully cross-section areas ranged from 2.90 to 20.90 m2, with an average of 9.31 ± 4.80 m2. Volumetric retreat of gully headcuts ranged from 4.49 to 40.55 m3 and averaged 13.34 ± 9.10 m3. Soil loss from individual gullies ranged from 5.79 to 52.31 t year−1 and averaged 17.21 ± 11.74 t year−1. The headcut retreat rate and sediment yield were closely related over the three study seasons. Elevated subsurface water levels facilitated the slumping of gully banks and heads, causing high sediment yield. When the soil was saturated, bank collapse and headcut retreat were favoured by the combination of elevated subsurface water and high rainfall. This study indicates that area exclosures are effective in controlling subsurface water level, thus reducing gully headcut retreat and associated soil loss. 相似文献
94.
Adolfo L. Méndez Berhondo Ramón E. Rodríguez Taboada Paolo Zlobec 《Astrophysics and Space Science》2008,318(1-2):73-78
Pulsating structures recorded at 237 MHz that are associated to decimetric continuum enhancement during the September 9, 2001 solar radio burst are described. We analyzed the radiopolarimetric data recorded at the Trieste Solar Radio System (INAF—Trieste Astronomical Observatory—Basovizza Observing Station) with very high time resolution (1 ms) at metric frequencies. Two different types of pulsations that occur in about 4 minutes at the same frequency are described. The possible mechanisms are analyzed and some parameters of the associated magnetic structure are estimated. 相似文献
95.
We investigated the Coulomb stress changes in the active faults surrounding a moderate‐magnitude normal‐faulting earthquake (2009 L'Aquila, Mw 6.3) and the associated variations in the expected ground motion on regional probabilistic seismic hazard maps. We show that the static stress variations can locally increase the seismic hazard by modifying the expected mean recurrence time on neighbouring faults by up to ~290 years, with associated variations in the probability of occurrence of the maximum expected earthquake of up to ~2%. Our findings suggest that the increase in seismic hazard on neighbouring faults following moderate‐magnitude earthquakes is probably not sufficient to necessitate systematic upgrades of regional probabilistic seismic hazard maps, but must be considered to better address and schedule strategies for local‐scale mitigation of seismic risk. 相似文献
96.
Alessio De ANGELIS Marco DIONIGI Paolo CARBONE Mauro MONGIARDO 车文荃 王清华 Franco MASTRI Giuseppina MONTI 《南京气象学院学报》2017,9(1):64-72
中程无线功率传输(WPT)可以采用几种不同的方式实现,如通过电感或电容耦合、谐振或非谐振网络实现.本文主要研究了通过感应耦合谐振器实现的WPT链路,而且只着重研究了利用2个谐振器的链路(直接链路)并工作在主谐振频率下的情况.研究结果表明,当工作在主谐振频率下,可以根据网络参数来对传输效率或负载功率进行优化. 相似文献
97.
Andrea Blašković Paolo Fastelli Hrvoje Čižmek Cristiana Guerranti Monia Renzi 《Marine pollution bulletin》2017,114(1):583-586
This paper reports baseline levels of litter (macro, meso and microplastics) in sediments collected from different areas of the Croatian MPA of the Natural Park of Tela??ica bay (Adriatic Sea, GSA n. 17). The distribution of total abundance according to size, for all analysed locations evidences that microplastics are the dominant fraction concerning item's numbers. In all analysed samples no macroplastics were found, while microplastics are 88.71% and mesoplastics are 11.29% of the total. 相似文献
98.
99.
Ponziani Michel Pogliotti Paolo Stevenin Hervé Ratto Sara Maria 《Natural Hazards》2020,104(2):1819-1839
Natural Hazards - Aosta Valley, an Alpine region in north-western Italy, has an early warning system (EWS) that issues hydrogeological alerts based on hydrological modelling and rainfall thresholds... 相似文献
100.
Paolo Clemente 《地震工程与结构动力学》1998,27(5):513-522
The dynamic analysis of stone arches, made up of rigid voussoir laid dray, can be performed in two phases. First of all the value of the horizontal acceleration necessary to turn the structure into a mechanism and the corresponding mechanism must be determined. Then the dynamic behaviour of such a mechanism under a given acceleration time history can be studied. The first step is a static matter. The second one requires the solution of the non-linear equation of motion of the one-degree-of-freedom system in which the arch is turned. In this paper an iteration procedure is proposed to find out the mechanism. Then the structural behaviour of the mechanism is analysed. Both free and forced vibrations are investigated and the study is limited to the first-half cycle of vibration. Damping is not considered and sliding between the blocks at the hinge sections is not allowed. © 1998 John Wiley & Sons, Ltd. 相似文献