排序方式： 共有72条查询结果，搜索用时 20 毫秒
21.
Leila M. Harris Danika Kleiber Lucy Rodina Sule Yaylaci Jacqueline Goldin Germaine Owen 《社会与自然资源》2018,31(1):89-105
We analyze the relationship between perceptions of domestic water access, and quality, in relation community engagement. While others have suggested linkages between material conditions of water access and engagement (e.g., that poor water access might spur engagement), to date there have been no studies those test these relationships using statistical methods. Based on a quantitative analysis of survey data from underserved sites in Accra, Ghana, and Cape Town, South Africa, our results show that water access and quality are both predictive of community engagement. The analysis also makes a strong case that there are different dimensions when considering the material conditions of water—in this case, water access and quality each condition engagement in opposite directions. Furthermore, consistent with other studies, our study also shows different demographics (notably gender) mediate these relationships in important ways. 相似文献
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Leila Hashemi Beni Sébastien Villeneuve Denyse I. LeBlanc Pascal Delaquis 《Transactions in GIS》2011,15(Z1):95-108
A Geographical Information System (GIS)‐based approach was developed for the identification of vulnerabilities and the measurement of risks associated with contamination of food systems with biological agents. In this research work, a tight integration of ArcGIS with the Arena simulation tool has been implemented. Arena was used to simulate and track contamination in a food distribution network and transmit the time dependent information to GIS. ArcGIS was employed to provide the primary user interface, process network data, and visualize the results. In addition, the GIS, through its powerful capabilities to process spatial data, could allow decision‐ makers to quickly determine the potential impact of a contamination event, at any stage, as a function of both time and geography. Two contamination scenarios along the farm‐to‐fork chain were examined to show the geographic zone and the proportion of the population affected by the contamination. A constraint Voronoi data structure was developed to define influence zones (these were color coded according to a dynamic risk index), to identify those areas that are at greatest immediate risk as time progresses, and to estimate the population affected by these contamination events. This approach thus appears to have general application to many GIS‐based risk assessment problems. 相似文献
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Weak ion-acoustic (IA) solitary wave propagation is investigated in the presence of electron trapping and background nonextensivity. A physically meaningful distribution is outlined and a Schamel-like equation is derived. The role a background electron nonextensivity may play on the energy carried by the IA soliton is then examined. It is found that nonextensivity may cause a soliton energy depletion. An increase of the amount of electron trapping leads to a net shift towards higher values of the soliton energy. 相似文献
25.
Weak ion-acoustic double-layers (IA-DLs) in a two-component plasma are investigated in the context of the nonextensive statistics
proposed by Tsallis. Due to the entropic index q, our plasma model can admit compressive as well as rarefactive IA-DLs. It is shown that the values
\frac53 < q < 3\frac{5}{3}q-parameters for the existence of small-DLs. As long as the Mach number M is less than ∼1.42, the only admissible q-values which may lead to IA-DLs are all positive. For −1<q<1 (1<q<5/3), the effect of increasing q is to lower (to shift towards higher values) the critical Mach number M
cr above which only compressive IA-DL are admitted. Beyond q=3, only compressive small-amplitude ion-acoustic double layers are observed. Furthermore, due to the flexibility of the q-parameter, the obtained results bring a possibility to deal with small-DLs with relatively high Mach numbers. Our investigation
may be of wide relevance to astronomers and space scientists working on interstellar plasmas. 相似文献
26.
Scott T. Kay Leila C. Powell rew R. Liddle Peter A. Thomas 《Monthly notices of the Royal Astronomical Society》2008,386(4):2110-2114
The relativistic Sunyaev–Zel'dovich (SZ) effect offers a method, independent of X-ray, for measuring the temperature of the intracluster medium (ICM) in the hottest systems. Here, using N -body/hydrodynamic simulations of three galaxy clusters, we compare the two quantities for a non-radiative ICM, and for one that is subject both to radiative cooling and to strong energy feedback from galaxies. Our study has yielded two interesting results. First, in all cases, the SZ temperature is hotter than the X-ray temperature and is within 10 per cent of the virial temperature of the cluster. Secondly, the mean SZ temperature is less affected by cooling and feedback than the X-ray temperature. Both these results can be explained by the SZ temperature being less sensitive to the distribution of cool gas associated with cluster substructure. A comparison of the SZ and X-ray temperatures (measured for a sample of hot clusters) would therefore yield interesting constraints on the thermodynamic structure of the intracluster gas. 相似文献
27.
Sophie Dabo-Niang Leila Hamdad Camille Ternynck Anne-Françoise Yao 《Stochastic Environmental Research and Risk Assessment (SERRA)》2014,28(8):2075-2099
A nonparametric density estimate that incorporates spatial dependency has not been studied in the literature. In this article, we propose a new spatial density estimator that depends on two kernels: one controls the distance between observations while the other controls the spatial dependence structure. The uniform almost sure convergence of the density estimate is established with the rate of convergence. The consistency of the mode of this kernel density is also studied. Then a spatial hierarchical unsupervised clustering algorithm based on the mode estimate is presented. Some simulations as well as an application to the Monsoon Asia Drought Atlas data illustrate the efficiency of our algorithm, and a comparison of the spatial structures of these data detected by the density estimate and clustering algorithm are done. 相似文献
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Leila Hazout Zein El-Abidine Zitouni Mostefa Belkhatir Tom Schanz 《Geotechnical and Geological Engineering》2017,35(5):2079-2105
Liquefaction of soils is a natural phenomenon associated with a dramatic loss of the soil shear strength in undrained conditions due to a development of excess pore water pressure. It usually causes extensive damages to buildings and infrastructures during earthquakes. Thus, it is important to evaluate extent of influential parameters on the liquefaction phenomenon of soils in order to clearly understand the different mechanisms leading to its triggering. The soil gradation is one of the most important parameters affecting the liquefaction phenomenon. In this context, a series of undrained compression triaxial tests were carried out on eighteen natural loose (Dr = 25%) sandy samples containing low plastic fines content of 2% (Ip = 5%) considering different extreme sizes (1.6 mm ≤ Dmax ≤ 4 mm and 0.001 mm ≤ Dmin ≤ 0.63 mm) and two mean grain size ranges (0.25 mm ≤ D50 ≤ 1.0 mm) and (1.0 mm ≤ D50 ≤ 2.5 mm). The initial confining pressure for all tests was kept constant (P′c = 100 kPa). The obtained test results indicate that the mean grain size (D50) and extreme grain sizes (Dmax and Dmin) have a significant influence on the undrained shear strength (known as liquefaction resistance) and appear as pertinent factors for the prediction of the undrained shear strength for the soil gradation under study. The undrained shear strength and the excess pore water pressure can be correlated to the extreme grain sizes (Dmax and Dmin) and the mean grain size (D50) of tested wet deposited samples. 相似文献
29.
Rahimi Leila Malekmohammadi Bahram Yavari Ahmad Reza 《Natural Resources Research》2020,29(6):3701-3718
Natural Resources Research - Understanding the spatial–temporal dynamics of wetland land cover (LC) changes and their impacts on ecosystem services (ESs) is essential for wetland conservation... 相似文献
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The main goal of the proposed work is to delineate structural boundaries in a very complex geology environment using the spatial
and statistical properties of the potential field data. The analysis is performed using magnetic anomaly of the total field
data over In Ouzzal, an Archaean north–south elongated block belonging to the Hoggar (Algeria). This region is geologically
and geophysically very poorly known except some localized areas. The intrinsic properties of high-frequency signals and the
related causative sources are explored, thanks to two-dimensional continuous wavelet transform. The obtained results, represented
by spatial distribution of the maxima of the modulus of the wavelet transform at each scale, clearly show that the major magnetic
singularities of the field may be related to geological features. Comparison with the Euler’s deconvolution solutions exhibits
a very good correlation. Even though where geological structures are known, our method shows better resolution and accuracy.
The proposed multiscale method proves to be more powerful, easy to use, and versatile where classical methods of potential
field interpretation fail or are very constraining. However, work is still ongoing to try to better and fully characterize
the causative sources of the potential fields. 相似文献