单轴分级循环加载时冻结粉质黏土的动力特性试验研究          下载免费PDF全文

罗飞  何俊霖  朱占元  刘恩龙  姚澜  黄秋阳 《地震工程学报》2019,41(2):385-391,398

为研究冻结黏土的动力特性,在不同温度(-0.6℃,-1.0℃,-1.5℃)和不同频率(0.5 Hz,1.0 Hz,1.5 Hz,2.0 Hz,3.0 Hz)时开展单轴分级加载试验。结果表明,随动应变幅的增加,温度和加载频率对土的动刚度、阻尼特性和残余应变特性的影响越来越显著;骨干曲线均呈线性变化特征,相同动应变幅时动刚度随温度的降低和频率的增加而增大;阻尼比随动应变幅的增加先增加再逐渐减小,加载末期呈略微增加趋势;相同动应变幅值时阻尼比随温度的降低和频率的增加而减小;同一级荷载下残余应变随循环次数呈线性不断增加,加载级数越高,残余应变增长越快;不同温度和频率时dε_(pd)/dt随动应变幅的增加而增大,相同动应变幅时dε_(pd)/dt随温度的升高和频率的降低而增大。  相似文献   

Late Holocene hydroclimatic variations and possible forcing mechanisms over the eastern Central Asia     

Lan  Jianghu  Xu  Hai  Yu  Keke  Sheng  Enguo  Zhou  Kangen  Wang  Tianli  Ye  Yuanda  Yan  Dongna  Wu  Huixian  Cheng  Peng  Abuliezi  Waili  Tan  Liangcheng 《中国科学:地球科学(英文版)》2019,62(8):1288-1301

Hydroclimatic variations over the eastern Central Asia are highly sensitive to changes in hemispheric-scale atmospheric circulation systems. To fully understand the long-term variability and relationship between hydroclimate and atmospheric circulation system, we present a high-resolution lascustrine record of late Holocene hydroclimate from Lake Sayram, Central Tianshan Mountains, China, based on the total organic carbon, total nitrogen, and carbonate contents, carbon/nitrogen ratios, and grain size. Our results reveal four periods of substantially increased precipitation at the interval of 4000–3780, 3590–3210, 2800–2160, and 890–280 cal yr BP, and one period of slightly increased precipitation from 1700–1370 cal yr BP. These wetter periods broadly coincide with those identified in other records from the mid-latitude Westerlies-dominated eastern Central Asia, including the northern Tibetan Plateau. As such, a similar hydroclimatic pattern existed over this entire region during the late Holocene. Based on a close similarity of our record with reconstruction of North Atlantic Oscillation indices and solar irradiance, we propose that decreased solar irradiance and southern migration of the entire circum-North Atlantic circulation system, particularly the main pathway of the mid-latitude Westerlies, significantly influenced hydroclimate in eastern Central Asia during the late Holocene. Finally, the inferred precipitation at Lake Sayram has increased markedly over the past 100 years, although this potential future changes in hydroclimate in Central Asia need for further investigation.  相似文献   

鄱阳湖湿地土壤微生物活性对年际水文变化的响应   总被引：1，自引：0，他引：1  

邹锋  李金前  韩丽丽  马燕天  王滨花  葛刚  吴兰 《湖泊科学》2019,31(2):551-559

湿地自然水文节律的改变影响着湿地生态系统的稳定与安全.为探究湿地水文变化对土壤微生物活性的影响,以鄱阳湖洲滩湿地3种典型植被狗牙根（Cynodon dactylon）、南荻（Triarrhena lutarioriparia）和苔草（Carex cinerascens）下表层土壤（0~20 cm）为研究对象,对湿地土壤微生物呼吸、微生物生物量和水解酶等土壤活性特征进行连续3年的实验监测,分析年际水位变化对不同植被湿地土壤微生物活性的影响.结果表明：丰水年显著提高土壤中养分的可利用性（有机质、总磷、速效磷）,提高土壤微生物生物量、微生物熵、水解酶活性,表明丰水年有利于湿地生态系统的物质循环转化.水文条件也能通过影响湿地植被生长改变土壤养分状况,进而对植被下土壤微生物活性产生显著影响.诸多土壤理化因子中,可溶性有机碳是驱动微生物活性变化最关键的因子.进一步分析表明,由植被类型所代表的长期水文累积效应对湿地土壤理化及微生物活性的调节作用大于单纯的年际水文变化.  相似文献   

深圳市快递自提点的空间分布特征与影响因素     

刘玲  李钢  杨兰  薛淑艳 《地球信息科学学报》2019,21(8):1240-1253

随着信息技术的发展,电子商务的盛行推动着快递行业的迅猛发展,快递自提点成为人们日常生活的重要场所,从而成为城市地理与物流地理的重要研究对象。本文基于2018年4月深圳市菜鸟驿站和中国邮政速递物流站点的POI数据,综合运用文本分析、数理统计、空间分析方法,解析深圳市快递自提点的空间分布特征和影响因素。研究发现：① 快递自提点依托类型多样：由市场主导的菜鸟驿站主要依托专业的快递公司、便利店等;由政府主导的邮政站点一般设于中国邮政的分支服务网点;② 快递自提点服务对象种类繁多,二者都主要以服务社区为主,企业、工业园、酒店等为辅;③ 快递自提点的区位选择一般靠近服务对象的出入口,80%的快递自提点分布在距其最近出入口200 m范围内,邮政站点更接近服务对象;④ 快递自提点的空间分布不均衡,呈现“中西部多,东部少”的特点,沿“东-西”走向集聚分布,为多核集聚模式;⑤ 快递自提点的空间格局是区域经济发展水平、人口分布、交通便捷程度、土地利用类型等多因素综合作用的结果,最后探索了快递自提点选址与分布的综合影响机制。  相似文献   

Rotenone treatment has a short-term effect on New Zealand stream macroinvertebrate communities     

Lan Pham  David West  Gerard P. Closs 《新西兰海洋与淡水研究杂志》2018,52(1):42-54

Invasive fish eradication is a key management strategy in aquatic ecosystems, and is often accomplished using piscicides such as rotenone. However, the effects of piscicides on aquatic invertebrate communities are poorly understood, particularly over long time scales. We monitored invertebrate communities in two treatment and two reference streams prior to and for one year following the use of rotenone to eradicate trout in Zealandia wildlife sanctuary, Wellington. Immediately following treatment, invertebrate density and taxonomic richness declined significantly, and community composition diverged markedly relative to reference streams, with pollution sensitive taxa declining greater than more tolerant taxa. Treatment streams recovered to pre-treatment conditions within 4–12 months of rotenone application, indicating minor long-term impacts on invertebrate communities. Speed of recovery of individual taxa appeared to be associated with life history variables, e.g. generation times and dispersal ability. Untreated upstream reaches and nearby water bodies likely facilitated successful invertebrate community recovery. Our results demonstrate that rapid recovery of New Zealand stream invertebrate communities is possible within one year of rotenone application.  相似文献   

无像控无人机倾斜摄影测量在农村地籍测量中的应用     

郭岚  王春涛  赵元务 《测绘与空间地理信息》2019,42(4):216-218

为了进一步提高无人机倾斜摄影测量的效率,本文提出了无像控无人机倾斜摄影测量的方法,并将该技术应用到农村地籍测量中。陕西省宝鸡市岐山县实验结果表明:所提出的无像控无人机倾斜摄影测量技术可以在保证农村地籍测量精度的前提下,提高无人机倾斜摄影测量在农村地籍测量中的工作效率。  相似文献   

多巴胺对凡纳滨对虾血细胞免疫作用效应途径的研究     

潘珊珊  潘鲁青  张兰 《海洋湖沼通报》2018,(6):150-158

本文通过血细胞体外培养,研究了多巴胺(DA)及多巴胺受体(DARs)拮抗剂对凡纳滨对虾血细胞信号转导通路和免疫防御效应的影响。结果表明:DA及DARs拮抗剂对凡纳滨对虾血细胞内信号通路因子(AC、PLC、cAMP、DAG、PKA、PKC)和免疫防御效应(酚氧化酶原活力、酚氧化酶活力、吞噬率及抗菌活力)影响显著(P <0.05)。在DA作用下血细胞第二信使合成酶(AC、PLC)、第二信使(cAMP、DAG)及蛋白激酶(PKA、PKC)含量显著升高;与DA处理组相比,DARs 1型拮抗剂对血细胞信号通路因子具有显著抑制作用,且表现出剂量效应,而DARs 2型拮抗剂引起AC、cAMP和PKA信号通路因子明显升高,PLC、DAG和PKC信号通路因子无显著变化。DA作用后血细胞酚氧化酶原活力、吞噬率及抗菌活力均显著降低,而胞吐酚氧化酶活力显著升高;与DA处理组相比,DARs 1型拮抗剂对血细胞上述免疫防御效应具有显著抑制作用,且呈剂量效应,而DARs 2型拮抗剂血细胞吞噬活力显著降低,而其他免疫防御效应无显著变化。混合DARs拮抗剂均与1型拮抗剂作用类似。综合上述研究结果得出,DA主要通过凡纳滨对虾膜上1型DAR激活AC-cAMP-PKA和PLC-DAG-PKC信号通路调控血细胞吞噬活力、proPO系统和免疫活性因子的胞吐,2型DARs抑制AC-cAMP-PKA信号通路,辅助调控吞噬作用。  相似文献   

风场对SWAN模式在台湾海峡后报结果的影响   总被引：2，自引：2，他引：0  

滕陈轲敏  岳显昌  吴雄斌  王少华  黄奇华  张兰 《海洋学报》2019,41(5):59-69

本文利用SWAN模式模拟分析了CCMP和DASCAT两种常用风场数据在台湾海峡海面的浪场结果。东北季风期3个月的浪场模拟结果与浮标实测波高时序数据相比,偏差均值不大于0.33 m,偏差均方根不大于0.59 m。一般在浮标波高大于3.5 m和小于1.0 m时,偏差偏大。6 h分辨率的风场数据相较于24 h分辨率风场数据对应的模拟结果更接近于浮标实测结果。在6 h和24 h分辨率的CCMP风场数据和24 h分辨率的DASCAT风场数据的模拟结果中,两两结果间的空间相关系数均不低于0.90,偏差均值不大于0.32 m,偏差均方根不大于0.4 m。  相似文献   

Introduction to the China-Vietnam Cooperation Project: A Comparative Study of the Holocene Sedimentary Evolution of the Yangtze and Red River Deltas     

Ping Yin  Van Phach Phung  Dinh Lan Tran  Huy Cuong Do  Van Vuong Bui  Xiaoyong Duan 《中国海洋大学学报(英文版)》2018,17(6):1269-1271

Both China and Vietnam confront the challenges of natural geohazards and environmental changes in their deltas and coastal zones due to rapid urbanization, economic development, and the impacts of global climate change. China and Vietnam initiated a comparative study of the Holocene sedimentary evolution of the Yangtze River Delta(YRD) and Red River Delta(RRD) for the period 2015–2018 in order to improve the understanding of the two delta evolution histories in the Holocene. Previous investigative data of the two rivers, onshore delta plains, and offshore subaqueous deltas have been explored and reinterpreted. New data gleaned from boreholes, piston cores, shallow seismic and hydrodynamic sources have been collected from the offshore YRD and the East China Sea inner shelf, and surface sediments and short cores have been collected from the RRD near-shore areas. Six focal areas of the joint project have been defined for comparative studies of the two deltas, including morphological development, sequential stratigraphy, coastline shifting, sedimentary characteristics, sedimentary dynamics, and correlation with anthropogenic global climate change. The results of these study areas are presented herein. The joint project also includes cooperative capacity building; exchanges of young scientists have been organized during the project period, and hands-on training in laboratory geochemical analysis, numerical modeling, and seismic data processing and interpretation have been provided by China and its Vietnamese geoscientist partners. Joint field excursions were organized to the upstream of the Yangtze and Red Rivers in Yunan Province, China, all the way downstream along the Vietnamese portion of the Red River. These joint studies have, over the past three years, improved understanding of the evolutionary history of these two major rivers and their mechanisms of source to sink. Joint project results of these two major deltas are not limited to the geosciences; the cooperative mechanical and operational experiences have been helpful for future cooperation in the field of marine geoscience between China and Vietnam, as well for cooperative activities with other ASEAN member countries.  相似文献   

孢粉证据揭示MIS5a以来福建东北沿海地区人类活动、海平面及气候变化          下载免费PDF全文

于俊杰  彭博  兰佑  武彬  王继龙  丁大林  劳金秀  李帅丽  戴璐 《地球科学》2021,46(1):281-292

通过获取了位于福建省宁德市海岸带的两个钻孔,并使用孢粉分析的方法来重建古环境.光释光和放射性碳十四测年结果表明,钻孔中最老的沉积物来自于深海氧同位素(MIS5a)阶段.孢粉组合中,海相沟鞭藻出现在MIS5a,MIS3早期和早、中全新世阶段,反映了这些时段的海侵事件.MIS5a以来,孢粉组合受控于常绿栎(Quercus)...  相似文献