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251.
Analyses have been undertaken to examine shoreline positions established from remote sensing data along the northwestern part
of the Nile delta from the Abu Qir Bay to Gamasa embayment (∼143 km length). The image data used (MSS, TM and ETM+ sensors)
are acquired at unequal intervals between 1972 and 2006, i.e., covering a time span of 34 years. Automated waterline positions
extracted from Landsat satellite images during this period of time were computer generated. A digital shoreline analysis software
was used to calculate the annual rate of beach changes at 1,432 cross-shore transects prior to (1972–1990) and after protection
(1993–2006). On comparison, rates estimated from three statistical approaches (the end point rate, the Jackknife and a weighted
linear regression) at corresponding positions are successfully validated with those measured from ground survey. Before protection,
results reveal longshore patterns wherein erosion along a coastal stretch gives way to accretion in an adjacent stretch, refining
the sub-cells previously identified within the littoral system of the delta. Maximum shoreline retreat occurs along the Rosetta
promontory (−138.52 m/year) and along the central bulge of the delta at Burullus headland (−6.07 m/year). In contrast areas
of shoreline accretion exist within saddles or embayments between the promontories at west Abu Qir Bay (20.04 m/year), Abu
Khashaba saddle (16.17 m/year) and Gamasa embayment (20.68 m/year). These rates of changes have been significantly altered
by the construction of intensive shoreline protective structures built from 1990 to combat areas of rapid erosion at both
the Rosetta promontory and Burullus–Baltim headland, ∼15-km length in total. 相似文献
252.
Christine A. Johnson Howard Topoff Robert K. Vander Meer Barry Lavine 《Behavioral ecology and sociobiology》2005,57(3):245-255
Social parasites exploit the behaviours of other social species. Infiltration of host systems involves a variety of mechanisms depending on the conditions within the host society and the needs of the social parasite. For many species of socially parasitic ants, colony establishment entails the usurpation of colonies of other species. This frequently involves the eviction or death of the host colony queen and the subsequent adoption of the invading queen. The social parasite queen achieves host worker acceptance by either manipulating the nest-mate recognition processes of the host or undergoing chemical modification. Little is known, however, about how host workers respond to social parasite eggs or whether host species defend against brood parasitism during parasite invasions. Host species are believed to adopt social parasite offspring because the recent common ancestry between many social parasites and their hosts may grant the sharing of certain characteristics such as chemical cues. Use of multiple host species, however, suggests other processes are needed for the social bond between host and parasite young to form. This study reports the findings of adoption bioassays in which eggs from a slave-maker ant, Polyergus breviceps, were offered to workers of two of its host species from unparasitised or newly parasitised nests to determine whether P. breviceps eggs generally elicit rearing behaviours from multiple host species. Comparisons of parasite egg survival until adulthood with conspecific egg survival reveal that workers of both host species, free-living or newly enslaved, do not typically accept slave-maker eggs. Both host species thus have sufficient discriminatory power to reject social parasite eggs although our hydrocarbon analysis indicates parasite eggs may be adapted to their local host species. Combined these results suggest that host rearing of P. breviceps eggs may reflect an evolutionary equilibrium that is maintained by probability and cost of recognition errors.Communicated by L. Sundström 相似文献
253.
We sutdied the application of the bacteria Azotobacter vinellandi on the treatment of effluents from pulp and paper industry. Two types of treatment employing this microorganism were studied: biological treatment isolated and combined with stages of pre- or post-treatment using ozonation or photocatalysis processes. In the biological treatment, the siderophores production by A. vinellandi had a major effect on the efficiency of effluents degradation. Among the different combined treatments, the best results were obtained with the photocatalytic pre-treatment. 相似文献
254.
255.
256.
This paper proposes a computable stochastic equilibrium model to represent the possible competition between Russia and China on the international market of carbon emissions permits. The model includes a representation of the uncertainty concerning the date of entry of developing countries (e.g., China) on this market in the form of an event tree. Assuming that this date of entry is an uncontrolled event, we model the competition as a dynamic game played on an event tree and we look for a solution called S-adapted equilibrium. We compare the solution obtained from realistic data describing the demand curves for permits and the marginal abatement cost curves in different countries, under different market and information structures: (i) Russia's monopoly, (ii) Russia–China competition in a deterministic framework, (iii) Russia–China competition in a stochastic framework. The results show the possible impact of this competition on the pricing of emissions permits and on the effectiveness of Kyoto and post-Kyoto agreements, without a US participation. 相似文献
257.
目的研究Gaussian白噪声作用下分数阶欠阻尼双稳系统的随机共振现象。方法采用统计复杂度方法探究分数阶导数、余弦信号的幅值及频率、阻尼系数等参数对分数阶系统随机共振效应的影响。结果当这些参数变化时,分数阶系统的统计复杂度曲线和标准Shannon熵曲线会产生不同的变化趋势,且在分数阶导数q=0.3时,系统最易发生随机共振现象。此外,当信号振幅增加至0.2时,可以增强随机共振效应;相反,信号频率增大至0.07时,可以削弱此现象。结论这些因素可以有效地调节分数阶双稳系统的随机共振现象。 相似文献
258.
为客观地评价尾矿坝稳定性,在随机场理论和极限平衡分析框架下,采用考虑参数空间变异性尾矿坝可靠度分析的非侵入式随机有限元法,通过Karhunen Loève级数展开方法离散尾矿材料参数(渗透系数、摩擦角等)随机场,利用Hermite随机多项式展开拟合尾矿坝安全系数与输入参数之间的隐式函数关系;再采用拉丁超立方抽样技术产生输入参数样本点求解多项式展开系数;最后,通过应用到一实际尾矿坝工程说明了该方法的有效性。结果表明,该方法可以真实地模拟尾矿材料的空间变异性对尾矿坝稳定性的影响,保证尾矿坝可靠度分析与确定性稳定分析互不耦合,与10 000次直接拉丁超立方抽样方法相比,该方法具有较高的计算精度和效率。 相似文献
259.
中国工业过程大气铅排放特征 总被引:2,自引:1,他引:1
依据典型行业活动水平数据和排放因子,采用"自下而上"排放因子法构建了2000—2010年我国有色金属冶炼、钢铁冶炼、建筑材料生产和铅酸电池生产等工业生产过程大气铅(Pb)排放清单.结果显示,我国工业过程大气Pb排放呈逐年递增趋势,年均增长率为12.5%,2010年排放量高达14920.47t;有色金属冶炼过程为大气Pb的主要来源,比重高达66.7%,其中,铅冶炼过程对整个工业过程的Pb排放贡献达到29.0%.钢铁烧结过程大气Pb排放仅次于有色金属冶炼过程,排放贡献率达23.1%,其排放主要来源于粗钢冶炼.另外,由于产业集中度低和控制技术相对落后,导致建材生产行业和铅酸电池生产过程排放对周边的环境影响也不容忽视.受矿产资源分布不均及产业布局等因素影响,我国工业过程大气Pb排放地区分布差异明显,主要集中在湖南、河南、云南、河北和江西等省份. 相似文献
260.
Amanda Guidero 《Disasters》2022,46(1):162-184
Attacks against humanitarian aid workers have received increasing attention in the media, particularly high-profile incidents such as those against the hospitals of Médecins Sans Frontières in Afghanistan, Syria, and Yemen. Concurrently, scholarly research has given rise to a number of articles, white papers, and books on humanitarian insecurity. Most of this work centres on external threats, neglecting the internal mechanisms that humanitarian organisations use to mitigate security situations. This paper builds on the existing literature by focusing on the decision-making processes of humanitarian organisations, drawing on data collected from 16 security managers or advisers. The findings reveal that several factors contribute to contextual uncertainty and complexity, including recipient perceptions, local government actions, the behaviour of other non-governmental organisations (NGOs) in the area, logistical issues, risk variance within a single location, and organisational mandate. Furthermore, the results indicate that NGOs utilise a combination of decision-making processes to determine how to manage security in high-risk environments. 相似文献