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通过对平武农村民居的调查分析，根据农村民居的类型，初步探讨了农村民居的历史和现状，并针对目前农村民居建设中存在的抗震设防问题提出了建议和整改措施。 相似文献
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通过对南华县农村民居抗震性能现状调查,找出农村民居抗震性能存在的不足和问题,并提出了提高农村民居抗震性能的对策及措施。 相似文献
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本文从建设社会主义新农村的高度,以提高农村民居抗御地震灾害的能力为目标,论述了在我国农村地区实施地震安全农居工程的必要性、可行性和目标;介绍了“十一五”国家防震减灾规划重点项目-地震安全农居示范工程的建设内容。涉及农村民居基础资料调查与抗震能力评价、农村民居抗震实用化技术研究与开发、地震安全农居示范工程建设、农村民居防震减灾知识宣传和技术培训、农村民居抗震技术服务网建设、地震安全农居工程投入机制、政策研究及国际合作等方面。 相似文献
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山西中部地区农村民居震害特征及抗震对策 总被引：1，自引：0，他引：1
收集整理山西中部地区历史地震灾害资料,总结了山西中部地区农村民居由地震引起的地基震害、建筑结构震害、建筑材料与施工震害三大特征,讨论了今后农村民居和村镇公共建筑的抗震对策。为将地震造成的民居震害损失降到最低程度,提出要实行总体规划,增强防震减灾意识,加强对农村民居抗震工作的指导的建议。 相似文献
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Spatial and temporal distributions of the trends of extreme precipitation indices were analysed between 1986 and 2005, over the Iberian Peninsula (IP). The knowledge of the patterns of extreme precipitation is important for impacts assessment, development of adaptation and mitigation strategies. As such, there is a growing need for a more detailed knowledge of precipitation climate change.This analysis was performed for Portuguese and Spanish observational datasets and results performed by the Weather Research and Forecast (WRF) model forced by the ERA-Interim reanalysis. Extreme precipitation indices recommended by the Expert Team for Climate Change Detection Monitoring and Indices were computed, by year and season. Then, annual and seasonal trends of the indices were estimated by Theil-Sen method and their significance was tested by the Mann-Kendal test. Additionally, a second simulation forced by the Max Planck Institute Earth System Model (MPI-ESM), was considered. This second modelling configuration was created in order to assess its performance when simulating extremes of precipitation.The annual trends estimated for the 1986–2005, from the observational datasets and from the ERA-driven simulation reveal: 1) negative statistically significant trends of the CWD index in the Galicia and in the centre of the IP; 2) positive statistically significant trends of the CDD index over the south of the IP and negative statistically significant trends in Galicia, north and centre of Portugal; 3) positive statistically significant trends of the R75p index in some regions of the north of the IP; 4) positive statistically significant trends in the R95pTOT index in the Central Mountains Chain, Leon Mountains and in the north of Portugal.Seasonally, negative statistically significant trends of the CWD index were found in Galicia, in winter and in the south of the IP, in summer. Positive statistically significant trends of the CWD index were identified in the Leon Mountains, in spring, and in Galicia, in autumn. For the CDD index, negative statistically significant trends were seen in Valencia, in the spring, and, in Galicia and Portugal (north and centre), in summer. Positive statistically significant trends of the CDD index were found: in the east of the IP, in the winter; in the Cantabrian Mountain, in the spring; and, in the south of the IP, in summer. Regarding to the R75p index, negative statistically significant trends were found in Galicia, in winter and positive statistically significant trends in the north of Portugal, in spring and in the Central Mountains Chain and north of Portugal, in autumn. For the R95pTOT index, negative statistically significant trends were found over the Sierra Cuenca and Sierra Cazorla, in winter and positive statistically significant trends were found over the Sierra Cebollera, in winter and in Castile-la Mancha region, in spring.The results of the annual and seasonal trends of the extreme precipitation indices performed for observational datasets and the simulation forced by ERA-Interim, are similar. The results obtained for the simulation forced by MPI-ESM are not satisfactory, and can be a source of criticism for the use of simulation forced by MPI-ESM in this type of climate change studies. Even for the relatively short period used, the WRF model, when properly forced is a useful tool due to the similar results of Portuguese and Spanish observational datasets and the simulation forced by ERA-Interim. 相似文献
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This paper examines present and future resource utilization in the tidal section of the Georges River in the southern part of Sydney. Over the last 30 years, the physical characteristics of the river have changed as a result of urbanization, changed hydrologic regime and sand dredging. Urbanization has resulted in an increase in population from 190,000 in 1947 to 550,000. This has resulted in an increase in runoff, sediment input to the river and waste disposal. The change in hydrologic regime has resulted in a substantial increase in the magnitude and frequency of flooding which has increased erosion. Sand dredging has increased the channel capacity, enlarged the tidal prism and increased water turbidity. It has also resulted in extensive bank erosion in the upper part of the river and extensive deposition lower down as tailings are deposited. Although most of these changes have resulted in the deterioration of environmental quality, use of the river for recreation and as an urban amenity has increased. 相似文献
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淮河流域焦岗湖水质参数时空变化及影响因素 总被引：3，自引：1，他引：2
焦岗湖是淮河左岸一个天然湖泊,集防洪、灌溉、养殖、旅游等多种功能于一体.利用焦岗湖4个季节水质监测数据,运用Kriging方法,分析焦岗湖水质参数的时空变化及影响因素.结果表明:由于受水文季节变化过程及人类活动等综合影响,焦岗湖水质参数在时间及空间上均存在一定差异.从时间变化来看,夏季透明度较低、秋季较高;溶解氧浓度在春、冬季显著高于夏、秋季;总氮、总磷浓度与高锰酸盐指数均表现为夏季最高、秋季最低.从空间变化来看,4个季节的透明度空间差异较为显著;溶解氧浓度在春、冬季空间分布较为均匀,夏季呈现中心高周围低的变化趋势,秋季则表现为西高东低;总磷浓度春季分布较为均匀,夏、秋及冬季则呈西高东低之势;高锰酸盐指数在春、秋季节呈现东高西低之势,夏季高浓度主要集中在湖区北部,冬季浓度变化不大. 相似文献
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Contrast in capillary pressure of heterogeneous permeable media can have a significant effect on the flow path in two-phase immiscible flow. Very little work has appeared on the subject of capillary heterogeneity despite the fact that in certain cases it may be as important as permeability heterogeneity. The discontinuity in saturation as a result of capillary continuity, and in some cases capillary discontinuity may arise from contrast in capillary pressure functions in heterogeneous permeable media leading to complications in numerical modeling. There are also other challenges for accurate numerical modeling due to distorted unstructured grids because of the grid orientation and numerical dispersion effects. Limited attempts have been made in the literature to assess the accuracy of fluid flow modeling in heterogeneous permeable media with capillarity heterogeneity. The basic mixed finite element (MFE) framework is a superior method for accurate flux calculation in heterogeneous media in comparison to the conventional finite difference and finite volume approaches. However, a deficiency in the MFE from the direct use of fractional flow formulation has been recognized lately in application to flow in permeable media with capillary heterogeneity. In this work, we propose a new consistent formulation in 3D in which the total velocity is expressed in terms of the wetting-phase potential gradient and the capillary potential gradient. In our formulation, the coefficient of the wetting potential gradient is in terms of the total mobility which is smoother than the wetting mobility. We combine the MFE and discontinuous Galerkin (DG) methods to solve the pressure equation and the saturation equation, respectively. Our numerical model is verified with 1D analytical solutions in homogeneous and heterogeneous media. We also present 2D examples to demonstrate the significance of capillary heterogeneity in flow, and a 3D example to demonstrate the negligible effect of distorted meshes on the numerical solution in our proposed algorithm. 相似文献
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Structure and Significance of S-wave Velocity and Poisson’s Ratio in the Crust beneath the Eastern Side of the Qinghai-Tibet Plateau 总被引：2，自引：0，他引：2
The receiver functions of body waves of distant earthquakes obtained for the regions beneath 41 digital stations (Lhasa and
GANZ in Tibet, Mandalay and Rangoon in Myanmar, SHIO in India, CHTO in Thailand, and station network in Sichuan and Yunnan)
were used to invert for S-wave structure in the crust and upper mantle in Sichuan, Yunnan, and their surrounding areas. Meanwhile
the distribution characteristics of the Poisson’s ration and the crustal thickness in Sichuan and Yunnan areas were also obtained.
Results indicate that the depth of Moho beneath the eastern side of Qinghai-Tibetan plateau varies strikingly. It is obvious
that the greatest changes in crustal thickness occur in a north-south direction. The crustal thickness decreases from north
to south, being as thick as 70 km in eastern Tibet, the northern portion of our area of interest, and less than 30 km in Chaing
Mai and Rangoon, the southern portion of our area. There are, however, exceptions regarding the trend. The thickness exhibits
an east-west variation trend in the area from Ma’erkong-Kongding in Sichuan to Lijiang in Yunnan. In general the Jinpingshan-Longmenshan
fault and Anninghe fault can be taken as the boundaries of this exception area. The thickness in Kongding in the west is 68 km,
while it is only 39 km in Yongchuan in the east. Moreover the Poisson’s ratio values in the blocks of central Sichuan and
Sichuan-Yunnan Diamond are high, and a low velocity layer in the crust of this area can be obviously detected. The distribution
characteristics of the high Poisson’s ratio and the low velocity of the crust in this block correspond to the tectonic structure,
being in contrast with the surrounding areas. Combining with the distribution features of the modern tectonic stress field,
it is deduced that the Sichuan-Yunnan area is probably the channel through which the materials of the lithosphere flow eastward. 相似文献
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We apply a geospeedometer previously developed in this lab to investigate cooling rate profiles of rhyolitic samples initially held at 720–750°C and quenched in water, liquid nitrogen, and air. For quench of mm-size samples in liquid nitrogen and in air, the cooling rate is uniform and is controlled by heat transfer in the quench medium instead of heat conduction in the sample. The heat transfer coefficient in ‘static’ air decreases with increasing sample size. For quench of mm-size samples in water, heat transfer in water is rapid and the cooling rate is largely controlled by heat conduction in the sample. Our experimental results are roughly consistent with previous calculations for cooling in air and in water (although constant heat transfer coefficients were used in these calculations), but cooling rate in liquid nitrogen is only 1.8–2.3 times that in ‘static’ air, and slower by a factor of 2 than calculated by previous authors. Cooling rate in compressed airflow is about the same as that in liquid nitrogen. The experimental results are applied to interpret cooling rates of pyroclasts in ash beds of the most recent eruptions of the Mono Craters. Cooling rates of pyroclasts are inversely correlated with sample size and slower than those in air. The results indicate that the hydrous species concentrations of the pyroclasts were frozen in the eruption column, rather than inside ash beds or in flight in ambient air. From the cooling rates, we infer eruption column temperature in a region where and at a time when hydrous species concentrations in a pyroclast were locked in. The temperature ranges from 260 to 570°C for the most recent eruptions of Mono Craters. These are the first estimates of temperatures in volcanic eruption columns. The ability to estimate cooling rates and eruption column temperatures from eruptive products will provide constraints to dynamic models for the eruption columns. 相似文献
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Pawe? Koperski 《Limnologica》2010,40(3):233-240
Reduced biological diversity in freshwater habitats situated in urban areas has been discussed in numerous studies. Certain municipal areas, however, can help save animal diversity of freshwater invertebrates. In the present study animals were collected or observed alive in 13 freshwater environments localized in Warsaw - the second largest city of Central Europe - in a densely populated, urban building complex close to the city, and also in suburban areas. Leech assemblages in all the environments under observation were numerically dominated by a few common species, but on the whole 19 species were collected or observed. The populations of six rare leech species inhabit both flowing and standing waters in Warsaw. Five of these species are on the Polish Red List of Species and one is strictly protected. The shallow Lake Powsinkowskie is the richest freshwater environment in the studied area in terms of species richness and rarity and also one of the richest lakes in Poland. Taxonomic diversity in the environments under study seems not to be directly related to the size of the water body or the level of degradation but rather to the habitat complexity, especially the diversity of the bottom in littoral zone. Certain freshwater habitats located inside this great urban complex still create good conditions for rare, highly specialized species. 相似文献
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Spatial and seasonal patterns of flood change across Brazil 总被引：1，自引：1，他引：0
Brazil has some of the largest rivers in the world and has the second greatest flood loss potential among the emergent countries. Despite that, flood studies in this area are still scarce. In this paper, we used flood seasonality and trend analysis at the annual and seasonal scales in order to describe flood regimes and changes across the whole of Brazil in the period 1976–2015. We identified a strong seasonality of floods and a well-defined spatio-temporal pattern for flood occurrence. There are positive trends in the frequency and magnitude of floods in the North, South and parts of Southeast Brazil; and negative trends in the North-east and the remainder of Southeast Brazil. Trends in the magnitude (frequency) were predominant in the winter (summer). Overall, floods are becoming more frequent and intense in Brazilian regions characterized by wet conditions, and less frequent and intense in drier regions. 相似文献
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《Limnologica》2020
The ecological functioning of floodplain lakes is largely influenced by the interaction with the river mainstem. In this study, seasonal variation in water chemistry and the relationship with the river conditions were compared between floodplain lakes that differ in the level of connection to the Usumacinta River, the largest river of Mesoamerica. Samples for suspended solids, nutrients, and chlorophyll a were collected through the year in lakes permanently connected to the river and in lakes that only received water from the Usumacinta for a short period during peak flow. Floodplain lakes showed higher total suspended solids than the river during the dry season while during the rainy season greater differences were observed between the river and the lakes, probably explained by higher concentrations in the river and greater sedimentation in the lakes. Greater organic matter content in the suspended solids was observed in the floodplain lakes, particularly in the more isolated lakes, likely related to high algal biomass. Nitrate concentrations were always higher in the river than in the lakes and lower nitrate concentrations occurred at the isolated lakes, suggesting that processes that remove nitrate occur through the year and are a common feature of floodplain lakes. Phosphorus in the connected lakes was higher than in the river only during the dry season, while in the isolated lakes concentrations were always greater than in the river. Chlorophyll a concentrations were higher in the connected lakes than in the river only during the dry season, while the more isolated lakes exhibited higher values through the year, showing signs of eutrophication. Suspended organic matter, nitrate, and chlorophyll showed larger differences between lake and river sites in the more isolated lakes, probably related to greater water residence time and its influence on primary production. Less connected lakes are more vulnerable to flow alteration because the brief period of connection to the river can be compromised and the effects of eutrophication exacerbated. 相似文献