نتایج جستجو برای: sand dune

تعداد نتایج: 29993  

2016
Valentina Cusseddu Giulia Ceccherelli Mark Bertness

Coastal sand dunes have attracted the attention of plant ecologists for over a century, but they have largely relied on correlations to explain dune plant community organization. We examined long-standing hypotheses experimentally that sand binding, inter-specific interactions, abiotic factors and seedling recruitment are drivers of sand dune plant community structure in Sardinia, Italy. Removi...

2003
B. S. DAYA SAGAR M. B. R. MURTHY P. RADHAKRISHNAN

Avalanches of various sizes occur due to instability during sand dune dynamics. A physically viable equation to model sand dune dynamics is a first order nonlinear difference equation. To visualize the size distribution of avalanches, sand dune dynamics has been numerically simulated by changing the strength of nonlinearity parameter (λ) that shows different impacts on dune dynamics. An equatio...

2015
Xin Gao Clément Narteau Olivier Rozier Sylvain Courrech du Pont

New evidence indicates that sand availability does not only control dune type but also the underlying dune growth mechanism and the subsequent dune orientation. Here we numerically investigate the development of bedforms in bidirectional wind regimes for two different conditions of sand availability: an erodible sand bed or a localized sand source on a non-erodible ground. These two conditions ...

پایان نامه :وزارت علوم، تحقیقات و فناوری - دانشگاه خلیج فارس - دانشکده مهندسی 1393

in civil engineering concrete is a material combined of hydraulic cement, sand, gravel and water. gravel and sand compose 60 to 70 percent of concrete. these aggregates support compression force of concrete. cement paste acts as glue to stick grain together. in bushehr factories producing aggregates do not operate according to astm standards, so that fineness modulus (fm) of the produced sands ...

2005
Yulin LI Douglas A. JOHNSON Yongzhong SU Jianyuan CUI Tonghui ZHANG

We investigated the variations in specific leaf area (SLA) and leaf dry matter content (LDMC) of 20 species (10 annuals and 10 perennials) that have different distributional patterns in the Kerqin Sandy Land in northern China. The main purpose of our study was to determine if SLA and/or LDMC could be used as indicators of plant resource-use strategy in sand dune environments. The selected speci...

2006
Jae Hwan Lee A. O. Sousa E. J. R. Parteli H. J. Herrmann

We model formation and evolution of transverse dune fields. In the model, only the cross section of the dune is simulated. The only physical variable of relevance is the dune height, from which the dune width and velocity are determined, as well as phenomenological rules for interaction between two dunes of different heights. We find that dune fields with no sand on the ground between dunes are...

2018
Baoli Fan Allen David McHugh Shujiang Guo Quanlin Ma Jianhui Zhang Xiaojuan Zhang Weixing Zhang Juan Du Qiushi Yu Changming Zhao

Calligonum mongolicum is a successful pioneer shrub to combat desertification, which is widely used for vegetation restoration in the desert regions of northwest China. In order to reveal the limitations to natural regeneration of C. mongolicum by asexual and sexual reproduction, following the process of sand dune stabilization, we assessed clonal shoots, seedling emergence, soil seed bank dens...

2009
Orencio Durán Veit Schwämmle Pedro G. Lind Hans J. Herrmann

Barchans are isolated mobile dunes often organized in large dune fields. Dune fields seem to present a characteristic dune size and spacing, which suggests a cooperative behavior based on dune interaction. In Duran et al. (2009), we propose that the redistribution of sand by collisions between dunes is a key element for the stability and size selection of barchan dune fields. This approach was ...

Journal: :CoRR 2015
Luca Bruno Davide Fransos

The engineering interest about dune fields is dictated by the their interaction with a number of human infrastructures in arid environments. Sand dunes dynamics is dictated by wind and its ability to induce sand erosion, transport and deposition. A deep understanding of dune aerodynamics serves then to ground effective strategies for the protection of human infrastructures from sand, the so-cal...

2008
Tsung-Yi Lin Jiing-Yih Liou

Coastal dunes, as a whole, represent a natural barrier between the sea and the land, playing a vital role in the coastal defense against the waves and tides. Compared to the use of hard, man-made structures, not only is it a less expensive method to counteract the coastal erosion problems, but it is also a method that has higher ecological and scenic values in the environmental management aspec...

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