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排序方式: 共有77条查询结果,搜索用时 15 毫秒
1.
永海会地区的区域构造、含矿地层和建造、中生代火山侵入岩体特征、局部控矿构造以及成矿物质来源、硫氢氧同位素、铅同位素、年龄同位素等成矿信息,都与扬子区、萍乐区已知铜金矿集区有许多相似之处。通过对比表明,永海会地区具有极大的找矿前应景。 相似文献
2.
从环境水文地质学的角度出发,对济南市地下水污染的主要途径和方式,以及局部地下水重污染区进行了较为详细的分析,济南市地下水污染以浅层地下水污染为主,局部地区深层地下水也已受到污染,并有进一步加重的趋势,地下水严重超采,造成多处地表塌陷和降落漏斗,并成为济南市地下水的重污染区。 相似文献
3.
Doug P. Armstrong Elizabeth H. Parlato Barbara Egli Wendy J. Dimond Renske Kwikkel Åsa Berggren Mhairi McCready Kevin A. Parker John G. Ewen 《Conservation biology》2021,35(3):859-869
Inbreeding depression is an important long-term threat to reintroduced populations. However, the strength of inbreeding depression is difficult to estimate in wild populations because pedigree data are inevitably incomplete and because good data are needed on survival and reproduction. Predicting future population consequences is especially difficult because this also requires projecting future inbreeding levels and their impacts on long-term population dynamics, which are subject to many uncertainties. We illustrate how such projections can be derived through Bayesian state-space modeling methods based on a 26-year data set for North Island Robins (Petroica longipes) reintroduced to Tiritiri Matangi Island in 1992. We used pedigree data to model increases in the average inbreeding level (F ) over time based on kinship of possible breeding pairs and to estimate empirically Ne/N (effective/census population size). We used multiple imputation to model the unknown components of inbreeding coefficients, which allowed us to estimate effects of inbreeding on survival for all 1458 birds in the data set while modeling density dependence and environmental stochasticity. This modeling indicated that inbreeding reduced juvenile survival (1.83 lethal equivalents [SE 0.81]) and may have reduced subsequent adult survival (0.44 lethal equivalents [0.81]) but had no apparent effect on numbers of fledglings produced. Average inbreeding level increased to 0.10 (SE 0.001) as the population grew from 33 (0.3) to 160 (6) individuals over the 25 years, giving a ratio of 0.56 (0.01). Based on a model that also incorporated habitat regeneration, the population was projected to reach a maximum of 331–1144 birds (median 726) in 2130, then to begin a slow decline. Without inbreeding, the population would be expected stabilize at 887–1465 birds (median 1131). Such analysis, therefore, makes it possible to empirically derive the information needed for rational decisions about inbreeding management while accounting for multiple sources of uncertainty. 相似文献
4.
Jessica M. Driscoll Lauren E. Hay Melanie K. Vanderhoof Roland J. Viger 《Journal of the American Water Resources Association》2020,56(1):16-29
This study explores the viability of using simulated monthly runoff as a proxy for landscape‐scale surface‐depression storage processes simulated by the United States Geological Survey’s National Hydrologic Model (NHM) infrastructure across the conterminous United States (CONUS). Two different temporal resolution model codes (daily and monthly) were run in the NHM with the same spatial discretization. Simulated values of daily surface‐depression storage (treated as a decimal fraction of maximum volume) as computed by the daily Precipitation‐Runoff Modeling System (NHM‐PRMS) and normalized runoff (0 to 1) as computed by the Monthly Water Balance Model (NHM‐MWBM) were aggregated to monthly and annual values for each hydrologic response unit (HRU) in the CONUS geospatial fabric (HRU; n = 109,951) and analyzed using Spearman’s rank correlation test. Correlations between simulated runoff and surface‐depression storage aggregated to monthly and annual values were compared to identify where which time scale had relatively higher correlation values across the CONUS. Results show Spearman’s rank values >0.75 (highly correlated) for the monthly time scale in 28,279 HRUs (53.35%) compared to the annual time scale in 41,655 HRUs (78.58%). The geographic distribution of HRUs with highly correlated monthly values show areas where surface‐depression storage features are known to be common (e.g., Prairie Pothole Region, Florida). 相似文献
5.
J. Kent Mitchell Benjamin A. Jones 《Journal of the American Water Resources Association》1976,12(6):1205-1222
ABSTRACT: Micro-relief surface depression storage is one of the components of the rainfall-runoff process. The quantification of surface depression storage values and a depth-storage model to describe the storage was the subject of this study. Point measurement data were collected on 258 surfaces of 5 soils and three artificial surfaces. Five methods of computing storage, 15 depth-storage models, two depth increments, and six grid spacings were investigated. The 1-inch grid computational method, 0.1-inch depth increment, and 1-inch grid spacings were recommended. The surface depression storage function is best described by the model S = aDb, which relates surface depression storage as a function of depth with two equation parameters. Equations for describing the surface depression storage model parameters have been developed. 相似文献
6.
针对影响油气管道安全运营的落石冲击问题,基于弹塑性力学、Cowper-Symonds本构模型和有限元方法,建立了球形落石冲击油气管道的计算模型,对管道动态响应过程进行了数值模拟。对冲击速度、落石半径、管道内压力和落石冲击位置进行了参数敏感性分析,研究了各参数对管道冲击变形的影响规律。结果表明:落石的冲击能量主要用于管道塑性变形;冲击过程中,落石与管道的接触区域由初始的椭圆斑逐渐变成了椭圆环;管道塑性变形随着冲击速度和落石半径的增大而增大,随内压和落石偏移度的增大而减小。该研究工作为油气管道的安全评价及防护工程的设计提供了参考依据,对保障油气安全运输具有重要的工程意义。 相似文献
7.
Male philopatry,extra-pack copulations and inbreeding avoidance in Ethiopian wolves (Canis simensis) 总被引:6,自引:0,他引:6
Claudio Sillero-Zubiri Dada Gottelli D. W. Macdonald 《Behavioral ecology and sociobiology》1996,38(5):331-340
Monogamous pairings have been regarded as the fundamental social unit in all canid species, including those living in packs.
In Ethiopian wolves, however, habitat saturation limits dispersal, which raises the question of whether they avoid inbreeding
and, if so, by what mechanism. In two study areas Ethiopian wolf packs had stable memberships. Each pack comprised two to
eight adult males, one to three adult females, including a clear-cut dominant individual of each sex, together with one to
six yearlings and up to six pups (n = 9 packs). Males remained in their natal packs, apparently throughout their lives. Some females also failed to disperse
while others dispersed in their second or third year and became floaters. Dominant females monopolized breeding, and were
succeeded either by their most dominant daughters (three cases) or by floaters (two cases). In the former case there is potential
for incest; however, 70% of 30 copulations observed were between the dominant female of one pack and a male from an adjoining
pack. In Ethiopian wolves, under conditions where dispersal is constrained and the potential for inbreeding is high, extra-pack
matings (and associated multiple paternity) result in outbreeding. We raise the possibility that extra-pair copulations may
be widespread in canid societies and that the monogamy supposedly fundamental to the family may be more sociological than
genetic.
Received: 15 October 1994/Accepted after revision: 9 December 1995 相似文献
8.
Xyleborini are a species-rich tribe of ambrosia beetles, which are haplodiploid and typically mate among siblings within their
natal brood chamber. Several characteristics of this tribe would predict the evolution of higher levels of sociality: high
genetic relatedness within galleries due to inbreeding, high costs of dispersal and the potential benefit of cooperation in
brood care within the natal gallery (e.g. by fungus gardening, gallery extension, offspring feeding and cleaning). However,
information on the social system of these beetles is very limited. We examined the potential for cooperative breeding in Xyleborinus saxeseni by monitoring dispersal in relation to brood size and composition. Results show that adult female offspring delay dispersal
despite dispersal opportunities, and apparently some females never disperse. The females’ decision to stay seems to depend
on the presence of eggs and dependent siblings. We found no indication that female offspring reproduce in their natal gallery,
as colonies with many mature daughters do not contain more eggs than those with few or no daughters. There is a significant
positive relationship between the number of females present and the number of dependent siblings (but not eggs), which suggests
that cooperative brood care of female offspring raises colony productivity by improving survival rates of immatures. Our results
suggest that cooperative breeding is likely to occur in X. saxeseni and possibly other xyleborine species. We argue that a closer look at sociality within this tribe may yield important information
on the factors determining the evolution of cooperative breeding and advanced social organization. 相似文献
9.
Qiusheng Wu Charles R. Lane Lei Wang Melanie K. Vanderhoof Jay R. Christensen Hongxing Liu 《Journal of the American Water Resources Association》2019,55(2):354-368
In terrain analysis and hydrological modeling, surface depressions (or sinks) in a digital elevation model (DEM) are commonly treated as artifacts and thus filled and removed to create a depressionless DEM. Various algorithms have been developed to identify and fill depressions in DEMs during the past decades. However, few studies have attempted to delineate and quantify the nested hierarchy of actual depressions, which can provide crucial information for characterizing surface hydrologic connectivity and simulating the fill‐merge‐spill hydrological process. In this paper, we present an innovative and efficient algorithm for delineating and quantifying nested depressions in DEMs using the level‐set method based on graph theory. The proposed level‐set method emulates water level decreasing from the spill point along the depression boundary to the lowest point at the bottom of a depression. By tracing the dynamic topological changes (i.e., depression splitting/merging) within a compound depression, the level‐set method can construct topological graphs and derive geometric properties of the nested depressions. The experimental results of two fine‐resolution Light Detection and Ranging‐derived DEMs show that the raster‐based level‐set algorithm is much more efficient (~150 times faster) than the vector‐based contour tree method. The proposed level‐set algorithm has great potential for being applied to large‐scale ecohydrological analysis and watershed modeling. 相似文献
10.
Two potential mechanisms for reducing the level of inbreeding, sex-biased dispersal and kin avoidance, were examined in the
Australian sleepy lizard, Tiliqua rugosa. The home range centres, and the genotypes at four polymorphic microsatellite DNA loci were determined for adult lizards
in a 70-ha study area near Mount Mary, South Australia. From estimates of genetic relatedness, females were as closely related
to other females as they were to males, both within the whole study area, and within home ranges. Similarly, males were as
closely related to other males as they were to females. This suggests that dispersal in the population is not sex-biased.
Sleepy lizards form monogamous pairs during the spring. Partners were less closely related to each other than to other potential
partners in the home range area. This suggests active choice of unrelated partners. The mechanism for recognising related
from unrelated individuals is unknown, but the behaviour could reduce inbreeding.
Received: 7 November 1998 / Accepted: 30 May 1999 相似文献