U–U–Th disequilibria and timescale of sedimentary transfers in rivers: Clues from the Gangetic plain rivers

This study uses ²³⁸U–²³⁴U–²³⁰Th disequilibria in river sediments in order to constrain the transfer times of sediments in alluvial plains of rivers from Himalaya and the Gangetic plain. From the observed distributions we infer sediment transfer times of about 100 ka in the Gangetic plain for rivers taking their source in the Himalayan chain, and longer transfer of about 160–250 ka for foothill-fed rivers. This difference is probably related to the difference in the sediment transport dynamics of these two types of rivers.     

Test application of Bayesian Programming: Adaptive water quality management under uncertainty

A new method, Bayesian Programming (BP), developed by Harrison [Harrison KW. Multi-stage decision-making under uncertainty and stochasticity: Bayesian Programming. Adv Water Resour, submitted for publication] is tested on a case study involving optimal adaptive management of a river basin. The case study considers anew the process of permitting pulp mills on the Athabasca River in Alberta, Canada. The problem has characteristics common to many environmental management problems. There is uncertainty in the water quality response to pollutant loadings that will not be completely resolved with monitoring and the resolution of this uncertainty is impeded by the stochastic behavior of the water quality system. A two-stage adaptive management process is optimized with BP. Based on monitoring data collected after implementation of the first-stage decision, the uncertainties are updated prior to the second decision stage using Bayesian analysis. The worth of this two-stage adaptive management approach to this problem and the worth of monitoring are evaluated. Conclusions are drawn on the general practicality of BP for adaptive management. Potential strategies are outlined for extending the BP approach to secure further benefits of adaptive management.     

黄河流域县域碳排放的时空格局演变及空间效应机制

利用空间面板模型、空间自相关分析和以区域背景与最近邻状况为空间滞后的空间马尔科夫链对2000—2017年黄河流域县域碳排放时空格局与空间效应进行分析,结果表明：① 2000年以来黄河流域碳排放量激增,由山东全域和陕甘宁蒙交界的高值区向外圈层与轴向扩张,形成东高西低碳排放格局;② 存在“俱乐部趋同”现象,高碳排放县集聚于山东全域和陕甘宁蒙交界,低碳排放县集聚于西南部;2000年与2017年对比发现县域碳排放类型稳定性强,较高碳排放变为较低碳排放的县集中在东南部区域,而相反方向转变的县集中在内蒙古;③ 高碳溢出效应与低碳锁定效应是塑造时空格局的重要作用力,前者作用力更强;区域背景增强了“俱乐部趋同”与被包围异常值趋同,作用力强于最近邻状况,不显著区域内碳排放类型转变概率提高。④ 空间面板模型结果显示年轻人口结构、大经济规模、二产为主产业结构、高生活水平和高公共支出促进了碳排放量增加与空间效应作用,其中经济规模与产业结构是重要驱动因素。     

基于投入产出表的中国水资源消耗结构路径分析

为了解各部门在生产链中水资源的具体消耗路径和在消耗路径中所发挥的作用以及维持生产链中水资源消耗的关键部门,论文基于2017年投入产出表和相关气象数据,在农业用水中加入绿水资源消耗量,利用投入产出模型和结构路径分析(structural path analysis, SPA)法分析中国42个部门水资源消耗的总量和结构,以及水资源在生产链中消耗的具体路径。结果表明：① 城镇居民消费和进口的水足迹最高,其次为农村居民消费,大多数水足迹较高的部门,都是以居民消费为主,进口水资源弥补了国内部分生产用水的消耗,但水资源短缺的形势仍然严峻;② 生产链前5个层级的水足迹消耗占比为95%左右,其中部门内部消耗占比最大,水足迹随层级数的增加而下降,水资源反馈循环程度较弱;③ 从部门生产链看,部门内部的水足迹占比最大,部门流入和流出水足迹差值较大,部门之间普遍存在单向依赖特征,关联网络不够稳定;④ 从最终消费角度看,农业部门内部水足迹占比最大,是生产链中重要的衔接结点,多样化的消费需求增加上游部门的水资源压力。研究为调整节水政策和提升水资源配置与管理能力提供了一定的理论基础。     

Study of traditional rural settlements landscape genetic variability in shaanxi province based on accurate-restoration北大核心CSCDCSSCI

Landscape genes of traditional rural settlements are a hotspot of settlements' landscape research. Based on existing research, this study defined the landscape genetic information chain and its hierarchy. The general life-like variation mechanism of landscape genes in traditional rural settlements was also proposed. On these bases, considering the landscape characteristics of traditional rural settlements in Shaanxi Province, the landscape genetic information chains of traditional rural settlements in the province were constructed and the general variation mechanism and characteristics of traditional rural settlements in the province were proposed. A theoretical framework of accurate restoration of the traditional rural settlements' landscape genetic information chain was further put forward. In addition, accurate restoration was applied to the typical settlement with variation in Shaanxi Province as an empirical case. The results verified the necessity and operability of accurate restoration. This research provides some thoughts and methods that are fresh and original for the protection and activation of traditional rural settlements from a landscape genetic perspective. © 2020, Editorial office of PROGRESS IN GEOGRAPHY. All rights reserved.     

灾害链学术思想的提出及两个概念概述

对灾害链的概念的提出及概念进行了研究，对灾害链的两种学术概念进行了讨论，一个是"灾-灾"的灾害链概念，一个是"以灾报灾"的灾与灾共生、共发、及续发的概念，而后一个的价值可以对大灾进行预测。     

马尔可夫切换的汽车悬架系统的事件触发H∞滤波

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.     

1978-2016年中国农业生态效率时空演变及趋势预测

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。     

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

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.