极端降雨事件对不同类型生物土壤结皮覆盖土壤碳释放的影响     

赵洋  齐欣林  陈永乐  张志山  贾荣亮  胡宜冈  张鹏 《中国沙漠》2013,33(2):543-548

于2011年5-8月,选择腾格里沙漠东南缘人工固沙植被区藻类、藓类和混生结皮覆盖的土壤为对象,研究了极端降雨量(降雨量44.7 mm、强度0.04 mm,min-1)、极端降雨强度(降雨量8.3 mm、强度0.55 mm·min-1)及普通降雨(降雨量16.3 mm、强度0.02 mm·min-1)条件下的碳释放过程.碳释放量的测定采用Li-6400-09土壤呼吸室,降雨结束后立即开始观测,直到呼吸速率恢复到降雨前水平时停止观测.结果表明:极端降雨(降雨量和降雨强度)结束初期藻类和混生结皮覆盖土壤的呼吸速率受到明显抑制,藻类结皮覆盖土壤呼吸速率分别为0.12 μmol·m-2·s-1和0.41 μmol·m-2·s-1,混生结皮覆盖土壤呼吸速率分别为0.10 μmol·m-2·s-1和0.45μmol·m-2·s-1;而极端降雨对藓类结皮覆盖土壤的影响不明显,呼吸速率分别为0.83 μmol·m-2·s-1和1.69μmol·m-2·s-1.这说明处于演替高级阶段的藓类结皮能够很好地应对短期的极端降雨事件.  相似文献   

昆明市碳源碳汇结构变化及其驱动因子研究     

何云玲  吴志杰  徐蕊 《云南地理环境研究》2013,(6):14-21

基于碳平衡理论,通过综合分析城市区域内主要自然生态系统的固碳功能,以及主要社会经济活动的排碳行为,构建了城市碳平衡分析模型,并以昆明市为例进行了研究。结果表明:昆明市碳收支不平衡,碳汇对碳源的抵消作用很弱;并且随着社会经济的发展这种不平衡状况在加剧,2010年,昆明市碳平衡系数为1.90,即城市释碳量是固碳量的1.90倍;碳供需余缺(释碳量-固碳量)达到1565.35×104t/a。产值增长是碳排放增加的主要动力,而能源强度下降、能源结构和产业结构调整是减缓碳排放的主要动力。  相似文献   

欧盟碳减排目标的经济可能性评估     

石莹  刘昌新  吴静  王铮 《世界地理研究》2013,(3):18-29

经济发展与能源消耗有着密切的关系,文章通过选取1994年至2009年欧盟27国的人口、经济和能源数据,利用碳排放动力学模型对欧盟关于2050年前削减温室气体排放80-95%的承诺进行预测,并对欧盟目标下的减排情景进行了分析。结果表明：（1）以当前的技术进步速率下,沿最优平稳经济增长路线,到2050年欧盟的碳排放量将为775.608MtC,达不到预定的减排要求;（2）在最优经济增长速度得出总能源消费量的基础上,采用调整能源结构与碳捕捉技术,预期可以达到设定减排80%的任务。其每一期的煤炭占比、石油占比、天然气占比应分别有4%、2.26%、1.23%转移至非碳能源占比,非碳能源的上升速率应达到2.21%/年;（3）若以历史的能源结构转移趋势预测未来的能源结构占比,即使考虑能源利用效率和碳捕捉技术的预期目标,欧盟仍然达不到在2050年的减排目标;（4）考虑欧盟提出的四种减排路径上下限组合,可预计出到2050年欧盟的减排范围在80.51%-87.16%;（5）若欧盟重振工业（特别是制造业）,即使考虑欧盟制定的减排路径,仍存在着达不到减排预期的可能。  相似文献   

基于生态足迹模型的福建省生态安全分析与预测     

吴明珠  李小梅  张江山 《福建地理》2013,(3):35-43

生态足迹是目前较通用的衡量区域可持续发展的指标,利用生态足迹模型与其他指标结合,可以测算生态赤字（盈余）、生态足迹压力指数、万元GDP足迹等反映区域生态安全状态的定量指标．本研究计算了2002-2008年福建省人均生态赤字及生态足迹压力指数,得到全省生态压力的变化趋势．利用GM（1,1）灰色预测模型预测2009--2014年福建省人均耕地生态足迹与承载力、人均建筑用地生态足迹与承载力、人均生态赤字及生态足迹压力指数,结果表明,若继续沿着2002--2008年的发展模式,福建省在未来几年内生态安全将面临极大威胁,全省经济发展模式转型刻不容缓．  相似文献   

Evolution of sedimentary environments of the middle Jiangsu coast, South Yellow Sea since late MIS 3   总被引：3，自引：0，他引：3  

Fei Xia  Yongzhan Zhang  Qiang Wang  Yong Yin  Karl W. Wegmann  J. Paul Liu 《地理学报(英文版)》2013,23(5):883-914

An evolutionary model of sedimentary environments since late Marine Isotope Stage 3 （late MIS 3, i.e., ca. 39 cal ka BP） along the middle Jiangsu coast is presented based upon a reinterpretation of core 07SR01, new correlations between adjacent published cores, and shallow seismic profiles recovered in the Xiyang tidal channel and adjacent northern sea areas. Geomorphology, sedimentology, radiocarbon dating and seismic and sequence stratigraphy are combined to confirm that environmental changes since late MIS 3 in the study area were controlled primarily by sea-level fluctuations, sediment discharge of paleo-rivers into the South Yellow Sea （SYS）, and minor tectonic subsidence, all of which impacted the progression of regional geomorphic and sedimentary environments （Le., coastal barrier island freshwater lacustrine swamp, river floodplain, coastal marsh, tidal sand ridge, and tidal channel）. This resulted in the formation of a fifth-order sequence stratigraphy, comprised of the parasequence of the late stage of the last interstadial （Para-Sq2）, including the highstand and forced regressive wedge system tracts （HST and FRWST）, and the parasequence of the postglacial period （Para-Sql）, including the transgressive and highstand system tracts （TST and HST）. The tidal sand ridges likely began to develop during the postglacial transgression as sea-level rise covered the middle Jiangsu coast at ca. 9.0 cal ka BP. These initially submerged tidal sand ridges were constantly migrating until the southward migration of the Yellow River mouth to the northern Jiangsu coast during AD 1128 to 1855. The paleo-Xiyang tidal channel that was determined by the paleo-tidal current field and significantly different from the modern one, was in existence during the Holocene transgressive maxima and lasted until AD 1128. Following the capture of the Huaihe River in AD 1128 by the Yellow River, the paleo-Xiyang tidal channel was infilled with a large amount of river-derived sediments from AD 1128 to 1855, causing the emergence of some of the previously submerged tidal sand ridges. From AD 1855 to the present, the infilled paleo-Xiyang tidal channel has undergone scouring, resulting in its modern form. The modern Xiyang tidal channel continues to widen and deepen, due both to strong tidal current scouring and anthropogenic activities.  相似文献   

The role of visualisation in the choice of stationary non-separable space–time covariance functions: an application to air pollution data     

José-María Montero 《International journal of geographical information science》2013,27(10):1887-1909

Modelling spatio-temporal dependencies resulting from dynamic processes that evolve in both space and time is essential in many scientific fields. Spatio-temporal Kriging is one of the space–time procedures, which has progressed the most over the last few years. Kriging predictions strongly depend on the covariance function associated with the stochastic process under study. Therefore, the choice of such a covariance function, which is usually based on empirical covariance, is a core aspect in the prediction procedure. As the empirical covariance is not necessarily a permissible covariance function, it is necessary to fit a valid covariance model. Due to the complexity of these valid models in the spatio-temporal case, visualising them is of great help, at least when selecting the set of candidate models to represent the spatio-temporal dependencies suggested by the empirical covariogram. We focus on the visualisation of the most interesting stationary non-separable covariance functions and how they change as their main parameters take different values. We wrote a specialised code for visualisation purposes. In order to illustrate the usefulness of visualisation when choosing the appropriate non-separable spatio-temporal covariance model, we focus on an important pollution problem, namely the levels of carbon monoxide, in the city of Madrid, Spain.  相似文献   

罕遇地震作用下的框架-摇摆刚架结构体系动力可靠度研究     

刘迪  杜永峰  李慧  李春锋 《地震学刊》2013,(6):691-697

针对钢筋混凝土框架结构的受力特点,采用增设摇摆刚架的抗震设计方法,以提高罕遇地震下建筑结构的安全性。建立了框架一摇摆刚架结构体系的计算模型,结合状态空间法与虚拟激励法,求解结构的平稳随机响应,并根据计算所得随机响应对框架一摇摆刚架体系的动力可靠度进行分析。以西部地区某已建成的6层框架结构为算例,探讨了罕遇地震作用下不同刚度比的摇摆刚架对新结构体系动力可靠度的影响。结果表明,通过增设不同刚度比的摇摆刚架,可以有效协调结构体系的变形模式,充分发挥结构的耗能能力,降低整体结构的条件失效概率。  相似文献   

磁敏感加权成像临床应用和在血管瘤评估中的研究进展     

高盛  吴戈  曾庆玉 《CT理论与应用研究》2013,(4):749-757

磁敏感加权成像是一种近年发展的MRI新技术,在中枢神经系统疾病中的诊断及鉴别诊断中的重要作用已经得到了广大临床大夫的认可,具有很高的应用价值和拓展前景。SWI作为常规MRI检查的重要补充序列,采用3D梯度回波扫描,完全速度补偿,射频脉冲扰相等技术,具有三维、高分辨率、高信噪比的特点,可以更好地分析软组织血管瘤的结构成分,鉴别活动性出血、机化血栓、钙化及铁沉积等。而且SWI相位图能够清楚显示瘤体内部新生血管、瘤体周围静脉血管位置和形态改变,更有利于准确评估病变范围及程度,为血管瘤定位及定性诊断可以提供更多的影像信息,对于临床诊断及治疗方案的制定、预后评估都具有重要的应用价值。  相似文献   

Impact of lateral force-resisting system and design/construction practices on seismic performance and cost of tall buildings in Dubai, UAE     

Mohammad AlHamaydeh  Khaled Galal  Sherif Yehia 《地震工程与工程振动(英文版)》2013,12(3):385-397

The local design and construction practices in the United Arab Emirates(UAE),together with Dubai’s unique rate of development,warrant special attention to the selection of Lateral Force-Resisting Systems(LFRS).This research proposes four different feasible solutions for the selection of the LFRS for tall buildings and quantifies the impact of these selections on seismic performance and cost.The systems considered are: Steel Special Moment-Resisting Frame(SMRF),Concrete SMRF,Steel Dual System(SMRF with Special Steel Plates Shear Wall,SPSW),and Concrete Dual System(SMRF with Special Concrete Shear Wall,SCSW).The LFRS selection is driven by seismic setup as well as the adopted design and construction practices in Dubai.It is found that the concrete design alternatives are consistently less expensive than their steel counterparts.The steel dual system is expected to have the least damage based on its relatively lesser interstory drifts.However,this preferred performance comes at a higher initial construction cost.Conversely,the steel SMRF system is expected to have the most damage and associated repair cost due to its excessive flexibility.The two concrete alternatives are expected to have relatively moderate damage and repair costs in addition to their lesser initial construction cost.  相似文献   

Study of the seismic response of a recycled aggregate concrete frame structure     

Changqing Wang  Jianzhuang Xiao 《地震工程与工程振动(英文版)》2013,12(4):669-680

Based on six-degree-of-freedom three-dimensional shaking table tests, the seismic response of a recycled aggregate concrete （RAC） frame was obtained. The analysis results indicate that the maximum story shear force and overturning moment reduce proportionally along the height of the model under the same earthquake wave. The story shear force, base shear coefficient and overturning moment of the structure increase progressively as the acceleration amplitude increases. The base shear coefficient is primarily controlled by the peak ground acceleration （PGA）. The relationships between the PGA and the shear coefficient as well as between the PGA and the dynamic amplification factor are obtained by mathematical fitting. The dynamic amplification factor decreases rapidly at the elastic-plastic stage, but decreases slowly with the development of the elastic-plasticity stage. The results show that the RAC frame structure has reasonable deformability when compared with natural aggregate concrete frame structures. The maximum inter-story drift ratios of the RAC frame model under frequent and rare intensity 8 test phases are 1/266 and 1/29, respectively, which are larger than the allowable value of 1/500 and 1/50 according to Chinese seismic design requirements. Nevertheless, the RAC frame structure does not collapse under base excitations with PGAs from 0.066 g up to 1.170 g.  相似文献