نتایج جستجو برای: boulders

تعداد نتایج: 736  

Journal: :Proceedings of the National Academy of Sciences 2017

2008
J Bret Bennington Tim Young

Introduction Glacial erratic boulders are plucked from bedrock by flowing ice, transported in the direction of ice flow, and deposited at the terminus of the glacier. If derived from a localized, distinctive region of bedrock, glacial erratics may be used as indicator stones to map the direction of ice flow. Furthermore, glacial erratics evolve during transport, becoming smaller and more rounde...

Journal: :Remote Sensing 2021

It is of great significance to apply the object detection methods automatically detect boulders from planetary images and analyze their distribution. This contributes selection candidate landing sites understanding geological processes. paper improves state-of-the-art method YOLOv5 with attention mechanism designs a pyramid based approach images. A new feature fusion layer has been designed cap...

Journal: :Science 2008
G H Jones E Roussos N Krupp U Beckmann A J Coates F Crary I Dandouras V Dikarev M K Dougherty P Garnier C J Hansen A R Hendrix G B Hospodarsky R E Johnson S Kempf K K Khurana S M Krimigis H Krüger W S Kurth A Lagg H J McAndrews D G Mitchell C Paranicas F Postberg C T Russell J Saur M Seiss F Spahn R Srama D F Strobel R Tokar J-E Wahlund R J Wilson J Woch D Young

Saturn's moon Rhea had been considered massive enough to retain a thin, externally generated atmosphere capable of locally affecting Saturn's magnetosphere. The Cassini spacecraft's in situ observations reveal that energetic electrons are depleted in the moon's vicinity. The absence of a substantial exosphere implies that Rhea's magnetospheric interaction region, rather than being exclusively i...

2013
BLANCA LEÓN CARL J. ROTHFELS KENNETH R. YOUNG KATHLEEN M. PRYER

—Fern identification usually requires the use of mature sporophytes, since attempts to identify juveniles using morphological traits often provides unsatisfactory results. Here we examined young sporophytes found among boulders in a river basin of a xeric valley in central Peru. Attempts to identify these sporophytes first pointed to four different genera, two in Pteridaceae (Anogramma and Pity...

2016
Dave Mount

• Planning the coordinated motion of a group of agents who wish to move to a specified location amidst many obstacles • Planning the motion of an articulated skeletal model subject to constraints, such as maintaining hand contact with a door handle or avoiding collisions while passing through through a narrow passageway • Planning the motion of a character while navigating through a dense crowd...

2001
Thomas E. Lisle

A fundamental difference between a canal and a natural stream is structure. Structure includes all the typical anomalies of natural streams that deflect the general downstream flow, such as bends, bars, bedrock knobs, boulders, landslide deposits, and large woody debris. This results in the storage of watershed products in the channel, and in a great heterogeneity in depth, velocity, stream gra...

2011

mowing. It is run along the ground on one large wheel which is f ree of the motor operat ing the cutter bar. I t can be tilted to cut up or down slopes and can be pivoted sharply in any direction. It has been found part icularly valuable for cutting around trees, boulders, t raps, creek-bottoms, and other golf course obstructions which formerly required hand cutt ing. The motor scythe, powered ...

Journal: :Earth-Science Reviews 2021

A landscape’s sediment grain size distribution is the product of, and an important influence on, earth surface processes landscape evolution. Grains can be large enough that motion of a single grain, infrequently mobile in size-selective transport systems, constitutes or triggers significant geomorphic change. We define these grains as boulders. Boulders affect evolution; their dynamics effects...

Journal: :The astrophysical journal 2023

Abstract We present deep Hubble Space Telescope images taken to examine the ejecta from DART spacecraft impact into asteroid Dimorphos. The reveal an extensive population of comoving boulders, largest which is ∼7 m in diameter (geometric albedo 0.15 assumed). Measurements 37 boulders show a mean sky-plane velocity dispersion 0.30 ± 0.03 s −1 , only slightly larger than 0.24 gravitational escape...

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