Ring torque of Saturn from interplanetary meteoroid impact     

W.-H. Ip 《Icarus》1984,60(3):547-552

Reevaluation of the interplanetary meteoroid mass flux at 10 AU obtains a value of M≈6×10⁴g sec^?1 for the meteoroid mass loading rate to the rings of Saturn. This meteoroid impact flux suggests that a large change to the configuration of the ring system could occur in a relatively short time (?10⁹years). This new element thus should be taken into consideration in discussion of the dynamical evolution of the rings.  相似文献   

First-Order Inconsistencies Caused by Rogue Trajectories     

John V. Postma  Eugene Yee  John D. Wilson 《Boundary-Layer Meteorology》2012,144(3):431-439

A theoretical requirement of the Interaction by Exchange with the Conditional Mean (IECM) micromixing model is that the mean concentration field produced by it must be consistent with the mean concentration field produced by a traditional Lagrangian stochastic (LS) marked particle model. We examine the violation of this requirement that occurs in a coupled LS–IECM model when unrealistically high particle velocities occur. No successful strategy was found to mitigate the effects of these rogue trajectories. It is our hope that this work will provide renewed impetus for investigation into rogue trajectories and methods to eliminate them from LS models.  相似文献   

Amino acids produced from the ultraviolet/extreme-ultraviolet irradiation of naphthalene in a H₂O+NH₃ ice mixture     

Y.-J. Chen  M. Nuevo  T.-S. Yih  W.-H. Ip  H.-S. Fung  C.-Y. Cheng  H.-R. Tsai  C.-Y. R. Wu 《Monthly notices of the Royal Astronomical Society》2008,384(2):605-610

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An integrated web-based air pollution decision support system – a prototype     

Yee Leung  Kwong-Sak Leung  Man-Hong Wong  Terrence Mak  Kwan-Yau Cheung  Leung-Yau Lo 《International journal of geographical information science》2018,32(9):1787-1814

To efficiently and effectively monitor and mitigate air pollution in the urban environment, it is of paramount importance to integrate into a unified whole air pollutant concentration databases coming from different sources including the ground-based stations, mobile sensors, remote sensing, atmospheric-chemical-transport models and social media for the analysis and unraveling of the complex air pollution processes in space and time. This study constructs and implements for the first time a prototype of the fully integrated air pollution decision support system (APDSS) that put together in an integrated manner all relevant multi-scale, multi-type and multi-source data for decision-making on urban air pollution. The prototype contains the main system that handles the multi-source, multi-type and multi-scale databases, queries, visualization and data mining algorithms and the integrated modules that individually and holistically capitalize on the power of the ground-based stations, ground and aerial mobile sensors, satellite-borne remote-sensing technologies, atmospheric-chemical-transport models and social media. It renders a solid scientific foundation and system development methodology for the study of the spatiotemporal air pollution profiles crucial to the mitigation of urban air pollution. Real-life applications of the prototype are employed to illustrate the functionality of the APDSS.  相似文献   

Numerical Study of Dual-Plume Interference in a Turbulent Boundary Layer     

Shahin N. Oskouie  Bing-Chen Wang  Eugene Yee 《Boundary-Layer Meteorology》2017,164(3):419-447

Direct numerical simulation is used to investigate the interference arising from the dispersion of passive scalar plumes released from a pair of point sources in a fully-developed wall-bounded shear flow. Four different lateral separations of the two sources for both near ground-level and elevated releases are considered. The downwind evolution of the correlation between the plume concentrations along the centreline between the two sources and the behaviour of the lateral profiles of the correlation at various locations downwind of the two sources are examined in detail. Differences in the exceedance probability over a high concentration level for a single plume and the total plume are highlighted and studied, and the effects of destructive and constructive interferences on the exceedance probabilities for the total plume are used to explain these differences. One significant result is that all higher-order (third-order and above) moments of the total concentration can be inferred from the application of a clipped-gamma distribution using the information embodied in only the first- and second-order concentration moments of each single plume, and in the cross-correlation coefficient of the instantaneous concentration of the two plumes.  相似文献   

Seismic shear distribution among interconnected cantilever walls of different lengths          下载免费PDF全文

Katrin Beyer  Sabrina Simonini  Raluca Constantin  Avigdor Rutenberg 《地震工程与结构动力学》2014,43(10):1423-1441

Mid‐rise to high‐rise buildings in seismic areas are often braced by slender reinforced concrete (RC) walls, which are interconnected by RC floor diaphragms. In design, it is typically assumed that the lateral forces are distributed in proportion to the wall's elastic stiffness. Pushover analyses of systems comprising walls of different lengths have, however, shown that large compatibility forces can develop between them, which should be considered in design, but the analyses have also shown that the magnitude of the computed forces is very sensitive to the modelling assumptions. Using the results of a complex shell element model as benchmark, different simple hand‐calculation methods and inelastic beam element models are assessed and improved to yield reliable estimates of the base shear distribution among the individual walls comprising the interconnected wall system. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

Characterization of Quaternary faults by electric resistivity tomography in the Andean Precordillera of Western Argentina     

Sabrina Y. Fazzito  Augusto E. Rapalini  Jos M. Corts  Carla M. Terrizzano 《Journal of South American Earth Sciences》2009,28(3):217-228

El río San Juan, situado en la Provincia de San Juan (Argentina) cruza la Precordillera y otras unidades geológicas incluyendo la Depresión de Ullum y la Zona de La Laja, entre las latitudes 31°S y 32°S. El curso del río tiene un cierto caracter antecedente como puede deducirse por sus dos trazas perpendiculares unidas por otra casi paralela a las alineaciones estructurales principales. En la zona de la Precordillera, el valle del río San Juan muestra numerosos abanicos aluviales, situados en las zonas de confluencia entre el río principal y sus tributarios. Las superficies de los abanicos aluviales cuaternarios estan cortadas por una serie de escalones que consideramos como terrazas aluviales generadas por episodios repetitivos de agradación y degradación. El sector estudiado incluye una zona con una importante actividad sísmica reciente(La Laja), otra sin una importante actividad sísmica reciente (Precordillera), y una zona subsidente (Ullum) donde se formó un gran lago natural hace unos 6500 años. El antiguo río San Juan fue capturado por el valle de la Quebrada de Ullum mediante una incisión del orden de 25 m, que implicó una nueva adecuación del gradiente del río mediante los efectos de la erosión remontante. El gradiente del río San Juan muestra algunas irregularidades que, aunque no se presenten relacionadas directamente con las estructuras principales, estan relacionadas con la propia dinámica fluvial que acentúa la diferenciación litológica. La anchura del valle del río principal, la geometria y el gradiente de cada tributario, junto a las litologias del basamento y a las dimensiones de cada area fuente local, son los factores principales que controlan los procesos de la generación de las terrazas aluviales. En la zona de La Laja, donde la terraza mas alta soporta un nivel de travertino, la datación de los depósitos travertínicos proporciona datos como para suponer una tasa de incisión del orden de 0,9–1 mm/año, asociada a la actuación periódica de la falla de La Laja.