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961.
The literature indicates climate change is likely to cause more frequent and intense extreme weather events along with higher temperatures and altered precipitation. Taiwan frequently suffers from extremes in the form of typhoons, and their effects threaten both social stability and public security. Temperature effects through climate change are also expected to alter crime rates. We examine the immediate and longer-run impacts of typhoons and other climate variables on crime rates in Taiwan. The immediate results suggest that typhoon intensity has a significantly negative influence on rates of crime, including all violent crimes and automobile thefts. They also show that warmer temperatures have a strong positive effect on all violent crimes and all the subtypes of violent crimes. In addition, longer duration typhoons increase the immediate rates of all violent crimes, automobile thefts and muggings while decreasing the rate of burglaries. In the long run, we find that typhoon intensity, duration and landfall have persistent, lagged effects on crime that vary from negative to positive. For example, strong-intensity typhoons have significantly negative lagged effects on crimes 3–5 months in the future but positive lagged effects on crimes in future months 6–9. Finally, projections under the IPCC climate change scenarios show all violent crimes will increase. 相似文献
962.
A low-dimensional model that describes both saturated and unsaturated flow processes in a single equation is presented. Subsurface flow processes in the groundwater, the vadose zone, and the capillary fringe are accounted for through the computation of aggregated hydrodynamic parameters that result from the integration of the governing flow equations from the bedrock to the land surface. The three-dimensional subsurface flow dynamics are thus described by a two-dimensional equation, allowing for a drastic reduction of model unknowns and simplification of the model parameterizations. This approach is compared with a full resolution of the Richards equation in different synthetic test cases. Because the model reduction stems from the vertical integration of the flow equations, the test cases all use different configurations of heterogeneity for vertical cross-sections of a soil-aquifer system. The low-dimensional flow model shows strong consistency with results from a complete resolution of the Richards equation for both the water table and fluxes. The proposed approach is therefore well suited to the accurate reproduction of complex subsurface flow processes. 相似文献
963.
The main objective of this paper was to investigate the dewatering behaviour of a clayey uranium ore slurry. The slurry (containing 28% clay size) exhibited moderate water adsorption (w l = 83% and w p = 30%). Primarily composed of muscovite (46%) and quartz (30%), the clay minerals included illite (8%), chlorite (5%) and kaolinite (2%) alongside a CEC of 41 (cmol(+)/kg) with Ca2+ and Mg2+ as the dominant cations. Likewise, the high EC (17,600 μS/cm) and ionic strength (1.15 mol/L) indicated a flocculated microstructure due to the presence of SO4 2? (22,600 mg/L) and Mg2+ (1340 mg/L) in the slurry water. Settling included sedimentation and consolidation at low initial solids condition (25–35%) whereas only consolidation was observed at high initial solids contents (40–50%). The average k reduced from 1.2 × 10?6 m/s (initial s = 25%) to 5.3 × 10?8 m/s (initial s = 50%) along with a void ratio reduction from 7.4 to 2.6. Due to thixotropic strength, volume compressibility during consolidation showed apparent pre-consolidation at low effective stress (0.3–2 kPa) with a reduction in void ratio from 2.6 to 2.5. The e s was found to be 2.46 at σ′ = 2 kPa and was followed by a steeper slope with the void ratio reducing to 2.1 at σ′ = 31 kPa. Likewise, the hydraulic conductivity during consolidation decreased from 2.6 × 10?9 m/s (at e = 2.6) to 2.0 × 10?10 m/s (at e = 2.1). 相似文献
964.
Akbar Balani Hamid Chakeri Ghodrat Barzegari Yilmaz Ozcelik 《Geotechnical and Geological Engineering》2017,35(6):2747-2762
The Cerchar test is one of the appropriate and routine tests for determining the rock abrasion; but as for the costs and pin wear measurement errors in laboratory procedures and lack of access to laboratory equipment, using of numerical modeling can lead to use of greater number of samples required during the course of mechanized excavation and reduce the costs and errors in the laboratory test. In this study, the Cerchar abrasivity test was modeled using PFC3D (Particle Flow Code in 3 Dimensions) software. In order to verify the simulation results, Cerchar laboratory test results obtained by Rostami (Rock Mech Rock Eng 47(5):1905–1919, 2014) were compared with the numerical modeling results. In modeling studies, the effects of some parameters such as apply load, test speed, pin hardness and scratching distance on pin wear were investigated. As a conclusion of the study, good agreement between modeling and experimental results was obtained for a given condition. As in the experiment with various loads in both laboratory tests and modeling, with increasing applied load the Cerchar abrasivity index also increased in the experiment with Rockwell hardness HRC (An abbreviation for Rockwell Hardness measured on the C scale. The Rockwell test determines the hardness by measuring the depth of penetration of an indenter under a large load compared to the penetration made by a preload, that on the C scale use from a indenter with 120° cone and 150 kgf load) 42. 相似文献
965.
Seasonal residence and counterurbanization: the role of second homes in population redistribution in Finland 总被引:1,自引:0,他引:1
Since the late twentieth century, many developed countries have experienced population deconcentration, labelled as counterurbanization. There has been an academic discussion on the meaning, validity and universality of this concept, drivers of counterurbanization and its impacts on rural areas. To date, research on counterurbanization mostly apply static and discrete definitions of residence, migration and population, which is an increasingly simplistic view in the contemporary reality of a growing multitude of forms of mobility, often related to dual residence. Particularly large-scale quantitative studies on counterurbanization are confined by existing statistical practices. This paper attempts to overcome this obstacle and describe the transformation of the settlement system in Finland acknowledging the role of second home mobility. To achieve this goal, it introduces two alternative measures of population, seasonal and average population, and analyses their spatial dynamics between the years 1990 and 2010 based on georeferenced grid statistical data. The study finds that although registered population has been concentrating during the period in analysis, seasonal population has been increasingly dispersed due to the growing number of second homes. It shows that the counterurbanization process, though not noticed by conventional statistics, does occur in Finland, manifested by seasonal rather than permanent moves. The article concludes that various forms of mobility should be taken into account when analysing the urban–rural population dynamics and transformations of settlement systems as well as in rural development planning. 相似文献
966.
967.
U-Pb, Hf and O isotope evidence for two episodes of fluid-assisted zircon growth in marble-hosted eclogites from the Dabie orogen 总被引:9,自引:0,他引:9
Yuan-Bao Wu Yong-Fei Zheng Zi-Fu Zhao Bing Gong Fu-Yuan Wu 《Geochimica et cosmochimica acta》2006,70(14):3743-3761
A combined study of internal structure, U-Pb age, and Hf and O isotopes was carried out for metamorphic zircons from ultrahigh-pressure eclogite boudins enclosed in marbles from the Dabie orogen in China. CL imaging identifies two types of zircon that are metamorphically new growth and recrystallized domain, respectively. The metamorphic zircons have low Th and U contents with low Th/U ratios, yielding two groups of 206Pb/238U age at 245 ± 3 to 240 ± 2 Ma and 226 ± 4 to 223 ± 2 Ma, respectively. Anomalously high δ18O values were obtained for refractory minerals, with 9.9 to 21.4‰ for garnet and 16.9‰ for zircon. This indicates that eclogite protolith is sedimentary rocks capable of liberating aqueous fluid for zircon growth during continental subduction-zone metamorphism. Most of the zircons are characterized by very low 176Lu/177Hf ratios of 0.000001-0.000028, indicating their growth in association with garnet recrystallization. A few of them falling within the older age group have comparatively high 176Lu/177Hf ratios of 0.000192-0.000383, suggesting their growth prior to the formation of garnet in the late stage of subduction. The variations in the Lu/Hf ratios for zircons can thus be used to correlate with garnet growth during eclogite-facies metamorphism. In either case, the zircons have variable εHf (t) values for individual samples, suggesting that their protolith is heterogeneous in Hf isotope composition with localized fluid availability in the bulk processes of orogenic cycle. Nevertheless, a positive correlation exists between 206Pb/238U ages and Lu-Hf isotope ratios for the metamorphically recrystallized zircons, suggesting that eclogite-facies metamorphism in the presence of fluid has the identical effect on zircon Lu-Hf and U-Th-Pb isotopic systems. We conclude that the zircons of the older group grew in the presence of fluid during the subduction prior to the onset of peak ultrahigh-pressure metamorphism, whereas the younger zircons grew in the presence of fluid released during the initial exhumation toward high-pressure eclogite-facies regime. 相似文献
968.
以广西大厂镇鲁塘铅锌矿尾砂为研究对象,通过淋滤实验研究了不同氧化还原条件下尾砂中Cu、Cd、Zn、Pb和As等元素的活化和迁移规律。结果表明:经高浓度氧化、高浓度还原条件处理的尾矿表现为pH<7的酸性环境,经低浓度氧化环境条件处理的尾砂呈现pH>7的弱酸性至弱碱性环境;尾砂中Cu、Cd元素活化迁移受pH值的影响明显,即高浓度还原和高浓度氧化条件可以促进Cu和Cd元素的迁移,酸性条件对Cu和Cd元素的迁移起到促进作用;Zn与Cd元素存在竞争吸附关系,但二者仍有明显差别;Pb和As元素受到还原条件的影响,能有效促进Pb和As元素的释放迁移。在淋滤实验前期,铅锌矿的表面阻力较小,由于环境酸碱性的改变,初始尾砂对重金属元素的吸附位能发生变化,重金属元素初期迁移能力得到加强;淋滤后期,矿物颗粒表面由于发生氧化还原反应,促使颗粒表面的阻力增加,重金属元素的溶出量减少,迁移能力受到抑制。 相似文献
969.
大庆市环境地质问题及防治对策研究 总被引:1,自引:1,他引:1
通过统计、对比等方法,在大庆市环境地质问题调查研究的基础上,分析、归纳了大庆市存在环境地质问题的类型、规模、产生原因、危害程度等;并有针对性地提出了相应的防治对策. 相似文献
970.