Spatio-temporal evolution of drought and flood disaster chains in Baoji area from 1368 to 1911     

Honglian Wan  Hailong Song  Chanchan Zhu  Beibei Zhang  Mi Zhang 《地理学报(英文版)》2018,28(3):337-350

Based on the collation and statistical analysis of flood and drought information in Baoji area from 1368 to 1911, and in the context of climate change, we investigated the spatio-temporal evolution characteristics of drought and flood disaster chains in this area during the Ming and Qing dynasties using the methods of moving average, cumulative anomaly and wavelet analysis. The results are as follows: (1) We found a total of 297 drought and flood events from 1368 to 1911 in Baoji. Among these events, droughts and floods occurred separately 191 and 106 times, which accounted for 64.31% and 35.69% of the total events, respectively. (2) We observed distinct characteristics of flood and drought events in Baoji in different phases. The climate was relatively dry from 1368 to 1644. A fluctuant climate phase with both floods and droughts occurred from 1645 to 1804. The climate was relatively wet from 1805 to 1911. Moreover, we observed a pattern of alternating dry and wet periods from 1368 to 1911. In addition, 3 oscillation periods of drought and flood events occurred around 70 a, 110 a and 170 a, which corresponded to sunspot cycles. (3) We also observed an obvious spatial difference in drought and flood events in Baoji. The northern and eastern parts of Weihe River basin were regions with both frequent droughts and floods. (4) The sequential appearance of drought and flood disaster chains in Baoji from 1368 to 1911 was in response to global climate change. Since the 1760s, global climatic deterioration has frequently led to extreme drought and flood events.  相似文献   

1978-2016年中国农业生态效率时空演变及趋势预测   总被引：4，自引：0，他引：4  

侯孟阳  姚顺波 《地理学报》2018,73(11):2168-2183

基于1978-2016年中国各省市面板数据,采用超效率SBM模型测算省际农业生态效率,在时间序列分析和空间相关性分析的基础上,构建传统和空间马尔可夫概率转移矩阵,探讨中国农业生态效率的时空动态演变特征,并预测其长期演变的趋势。研究发现：① 中国农业生态效率呈现出在波动中稳定上升的“双峰”分布特征,且波峰高度的差距在缩小,但整体仍处于较低水平,农业生态效率仍存在较大提升空间,东部地区农业生态效率提升较中西部地区更加显著;② 中国农业生态效率整体上向高水平方向转移的趋势显著,但农业生态效率的演变具有维持原有状态的稳定性,且较难实现跨越式转移。地理空间格局在农业生态效率时空演变过程中发挥着重要作用,空间集聚特性显著,农业生态效率较高的省市具有正向的溢出效应,而农业生态效率较低的省市具有负的溢出效应,从而在空间格局上逐渐形成“高高集聚、低低集聚、高辐射低、低抑制高”的“俱乐部收敛”现象;③ 从长期演变的趋势预测来看,多数省市农业生态效率逐渐向上转移为较高水平,并逐渐演变为由低到高渐次递增的格局,在农业生态效率较低的地理背景下,其长期演变的稳定状态表现为偏“单峰”分布,而在农业生态效率较高的地理背景下,其长期演变为较高水平集聚的偏“双峰”分布。最后,分析当前研究需要改进的方向,并提出控制农业污染排放量、地区间农业生态政策联动、加强地区间农业生态合作交流与借鉴等能够有效提升中国农业生态效率及缩小省市间差距。  相似文献   

马尔可夫切换的汽车悬架系统的事件触发H_∞滤波     

孙家玉  严怀成  李郅辰  詹习生 《南京气象学院学报》2018,10(6):731-739

针对具有马尔可夫切换信道的两自由度（2-DOF） 四分之一汽车悬架系统,研究了事件触发 H_∞ 滤波问题.首先,信道切换由马尔可夫链控制;其次,考虑到事件触发的通信方案,由于有限的网络带宽,产生信号量化和随机丢包问题;然后,采用马尔可夫线性跳变系统模型来表示整个滤波网络系统.利用Lyapunov泛函和线性矩阵不等式方法将事件触发 H_∞ 滤波问题转化为凸优化问题,从而设计了切换信道相关的滤波器,使得滤波误差系统在均方意义上是指数稳定的并达到期望的性能水平.最后,通过仿真实例验证了所提出的设计方法的有效性.  相似文献   

Enhanced change detection index for disaster response,recovery assessment and monitoring of buildings and critical facilities—A case study for Muzzaffarabad,Pakistan     

《International Journal of Applied Earth Observation and Geoinformation》2017

The availability of Very High Resolution (VHR) optical sensors and a growing image archive that is frequently updated, allows the use of change detection in post-disaster recovery and monitoring for robust and rapid results. The proposed semi-automated GIS object-based method uses readily available pre-disaster GIS data and adds existing knowledge into the processing to enhance change detection. It also allows targeting specific types of changes pertaining to similar man-made objects such as buildings and critical facilities. The change detection method is based on pre/post normalized index, gradient of intensity, texture and edge similarity filters within the object and a set of training data. More emphasis is put on the building edges to capture the structural damage in quantifying change after disaster. Once the change is quantified, based on training data, the method can be used automatically to detect change in order to observe recovery over time in potentially large areas. Analysis over time can also contribute to obtaining a full picture of the recovery and development after disaster, thereby giving managers a better understanding of productive management and recovery practices. The recovery and monitoring can be analyzed using the index in zones extending from to epicentre of disaster or administrative boundaries over time.  相似文献   

2020年国外地震灾害及其影响综述     

李华玥  文鑫涛  陈雅慧  郑通彦 《震灾防御技术》2021,16(3):583-588

基于中国地震台网中心、美国地质勘探局（USGS）、相关新闻报道及EM-DAT （OFDA/CRED）国际灾害数据库等不同信息源给出的数据,提取全球2020年地震灾害的相关信息,对2020年国外地震活动情况进行汇总,并对主要受灾国家的地震灾害及其影响和国外地震灾害损失特点进行概括与阐述,为后续国际地震动态分析、地震灾害研究、应急救援探索等提供基础资料。  相似文献   

湖北刘家场地区奥陶系地层沉积相及马尔科夫链分析          下载免费PDF全文

周斌  汤军  周金应 《江苏地质》2013,37(4):621-625

根据野外实测剖面分析刘家场地区奥陶系从西陵峡组到临湘组的地层特征、古生物类型和沉积相演化规律,表明该区奥陶系以碳酸盐岩台地相序为主,主要由局限台地、开阔台地、台地边缘生物礁和沉没台地组成。在此基础上,运用马尔科夫链随机过程建立研究区沉积序列概率模式。以定量的数学地质方法估计了岩相在垂直剖面上的转移概率,克服了传统的定性沉积相模式建立方法中存在的由人为因素导致的差异,研究结果表明这是一种行之有效的将复杂地质问题简化的处理方法。  相似文献   

两种纯化方法获得脂肪酸的链长及碳同位素分布特征对比   总被引：1，自引：0，他引：1  

赵江涛  刘卫国  安芷生 《岩矿测试》2013,32(1):101-107

饱和脂肪酸及其同位素组成是重建古环境和古气候的重要代用指标,目前存在多种提取及纯化流程。在全球变化研究中,基于不同原理的纯化流程得到的脂肪酸含量及其同位素组成是否一致,直接影响着该指标应用于不同区域重建结果的对比。本文用两种常见的脂肪酸纯化流程提取脂肪酸标准、现生植物和泥炭样品类脂物,通过对比发现:对脂肪酸标准两种流程都可以得到纯净的单体脂肪酸,而且回收率均较高(85%以上),都是较为可靠的脂肪酸纯化流程;然而对于天然样品,虽然高碳数脂肪酸(碳数>C₂₄)的回收率相近,流程1却能够获得相对较多的低碳数饱和脂肪酸,如泥炭样品中该流程获得的n-C₂₂脂肪酸是流程2的3倍;两种流程纯化狗尾草(Setaira viridis)和三叶草(Trifolium repens)得到n-C₁₆脂肪酸的δ¹³C不同,流程1分别为-21.1‰和-36.2‰;流程2分别为-23.3‰和-34.9‰,表明两个实验流程得到的低碳数脂肪酸的含量、脂肪酸链长分布模式以及碳同位素组成均存在明显的差异。实验结果显示,流程2分离纯化样品可得到几乎全部的游离态脂肪酸,而流程1可提纯样品中游离态和酯态存在的总脂肪酸。由于在沉积物中游离态脂肪酸和酯态脂肪酸可以相互转化,因此使用流程1分析样品中的总脂肪酸更为合适,也可以将类脂物皂化使酯态脂肪酸释放为游离态,然后使用流程2。  相似文献   

基于最短路径分析的中间件设计与应用研究     

张铮 《测绘与空间地理信息》2013,(12):179-181

最短路径分析的根本目的是研究、筹划一项网络工程应如何安排而使其运行效果最好,其在社会生活中应用广泛且研究意义重大。在软件开发方面,q-间件能够屏蔽底层多源异构系统环境和数据环境,提高模型复用率和软件开发效率,因此本文提出通过中间件方式实现最短路径分析算法与应用系统的集成,为实际应用提供新的思路。  相似文献   

Farm Size and Land Use Pattern Changes in Postsocialist Poland∗     

Peter Dannenberg  Tobias Kuemmerle 《The Professional geographer》2013,65(2):197-210

The postsocialist transition resulted in widespread structural change in Polish agriculture, but fine-scale assessments of how these changes affected farming and rural landscapes are scarce. This article examines changes in farm sizes and land use patterns after the breakdown of socialism in Poland using micro-census data and satellite images. Our study area is Pyrzyce County. The analysis indicates a polarization of the farm size distribution (e.g., medium-sized farms disappeared) as well as marked changes in land use patterns (e.g., increasing field sizes and field aggregation). Interviews with farmers and stakeholders suggest that this shift can be explained by decreasing competitiveness of medium-sized farms in the emerging new agricultural value chain, which forced farmers to increase and intensify production or to downsize their farms, especially when the preference was for other occupations.  相似文献   

Participatory 3-dimension mapping: A tool for encouraging multi-caste collaboration to climate change adaptation and disaster risk reduction     

《Applied geography (Sevenoaks, England)》2013

This article reflects upon the use of participatory 3-dimensional mapping (P3DM) for facilitating the collaboration of different castes in disaster risk reduction (DRR) and climate change adaptation (CCA). Unequal power relationships amongst upper and lower castes has indeed been identified has a major driver of people's vulnerability to natural hazards, including the negative effects of climate change, in Nepal and elsewhere in South Asia. However, this does not prevent the members of all these castes, including the lowest untouchables, to display significant capacities in facing these natural hazards and changes in climate patterns. It is therefore similarly important to harness those capacities and address the unequal power relationships underpinning vulnerability. Achieving these goals requires fostering dialogue amongst upper and lower castes as well as with other stakeholders of DRR and CCA, e.g. scientists, NGOs, government agencies, which often tend to work with a single caste because it is easier. P3DM provides a platform for such a dialogue as it makes the knowledge of every caste tangible and credible to others. This proves essential in both assessing and planning for reducing the risk of disasters and adapting to climate change. This article particularly documents activities conducted in a small village of the Terai plain of Nepal frequently affected by flooding.  相似文献