Network analysis reveals open forums and echo chambers in social media discussions of climate change     

《Global Environmental Change》2015

Action to tackle the complex and divisive issue of climate change will be strongly influenced by public perception. Online social media and associated social networks are an increasingly important forum for public debate and are known to influence individual attitudes and behaviours – yet online discussions and social networks related to climate change are not well understood. Here we construct several forms of social network for users communicating about climate change on the popular microblogging platform Twitter. We classify user attitudes to climate change based on message content and find that social networks are characterised by strong attitude-based homophily and segregation into polarised “sceptic” and “activist” groups. Most users interact only with like-minded others, in communities dominated by a single view. However, we also find mixed-attitude communities in which sceptics and activists frequently interact. Messages between like-minded users typically carry positive sentiment, while messages between sceptics and activists carry negative sentiment. We identify a number of general patterns in user behaviours relating to engagement with alternative views. Users who express negative sentiment are themselves the target of negativity. Users in mixed-attitude communities are less likely to hold a strongly polarised view, but more likely to express negative sentiment towards other users with differing views. Overall, social media discussions of climate change often occur within polarising “echo chambers”, but also within “open forums”, mixed-attitude communities that reduce polarisation and stimulate debate. Our results have implications for public engagement with this important global challenge.  相似文献   

环境污染中三维捕食_被捕食系统生存和绝灭的阈值     

刘宇红  刘志美 《广东海洋大学学报》2007,27(3):96-99

研究了一类受环境污染的3种群系统,得到了三维捕食_被捕食系统持续生存与绝灭的阈值,并由此对系统的正平衡点的稳定性进行了分析。  相似文献   

Total Lightning Characteristics and Electric Structure Evolution in a Hailstorm          下载免费PDF全文

ZHENG Dong  ZHANG Yijun  MENG Qing  LU Weitao  YI Xiaoyuan 《Acta Meteorologica Sinica》2009,23(2):233-249

In this paper, total lightning data observed by SAFIR3000 3-D Lightning Locating System combined to radar data to analyze characteristics of lightning activity and electric structure of a hailstorm that occurred in Beijing on 31 May 2005.The results indicated that there were two active periods for the lightning activity during the hailstorm process. The hail shooting was found in the first period. After the end of the hail shooting,lightning frequency decreased suddenly. However, more active lightning activities occurred in the second period with lots of them appearing in the cloud anvil region. The peak of the lightning frequency came about 5 min prior to the hail shooting. Only 6.16\% of the total lightning was cloud-to-ground (CG)lightning, among which 20\% had positive polarity. This percentage was higher than that in normal thunderstorms. In addition, heavier positive CG lightning discharge occurred before rather than after the hail shooting. In the stage of the hail shooting, the electric structure of the hailstorm was inverted, with the main negative charge region located around the -40℃ level and the main positive charge region around the -15℃ level. In addition, a weak negative charge region existed below the positive charge region transitorily. After the hail shooting, the electric structure underwent fast and persistent adjustments and became a normal tripole and lower levers with positive charge in the upper levels and negative charge in the middle level. However, the electric structure was tilted under the influence of the westly wind in the middle and upper levels. The lightning activity and electric structure were closely related to the dynamic and microphysical processes of the hailstorm. It was believed that severe storms with stronger updrafts were more conducive to an inverted tripolar electric structure than normal thunderstorms,and the inverted distribution could then facilitate more positive CG lightning in the severe storms.  相似文献   

泰州市大气挥发性有机物化学组分特征、活性及来源解析     

樊凡  宋锴  俞颖  万子超  陆思华  唐荣志  陈仕意  曾立民  郭松 《南京气象学院学报》2020,12(6):695-704

挥发性有机物（VOCs）是臭氧和大气颗粒物的重要前体物,本研究利用在线气相色谱-质谱仪（Online-GC-MS）于2018年5—6月对江苏省泰州市大气中98种VOCs进行监测,依据监测结果对泰州市大气VOCs的组成特征、日变化趋势进行分析,对醛酮类VOCs数据进行参数化拟合探究其一次二次贡献,并采用正矩阵因子分解模型（PMF）对VOCs数据进行来源分析,用最大增量反应活性（MIR）计算臭氧生成潜势（OFP）.研究结果表明：泰州市大气VOCs中烷烃占比最高,其次为醛酮;烷烃、烯烃、卤代烃和芳香烃浓度日变化趋势明显,特征相近;参数化方法表明醛类物质主要来自于二次生成,而酮类物质主要来自一次排放;PMF模型结果表明泰州市VOCs的主要贡献源分别为机动车排放、油气溶剂挥发、生物质燃烧、其他工业和天然源;OFP的主要贡献物种为烯烃类,占比34.18%.研究结果表明,控制工业排放和溶剂使用是泰州市大气污染物控制的重点.  相似文献   

地闪不规则先导的多尺度熵特征   总被引：2，自引：2，他引：0       下载免费PDF全文

李婵  张阳  吕伟涛  郑栋  谭涌波 《应用气象学报》2014,25(3):347-353

针对不规则脉冲簇难以判别问题,将多尺度熵应用于不规则先导分析中,探讨闪电信号不规则脉冲分析应用中多尺度熵关键参量的选择方法。在此基础上,将不规则先导与直窜先导及梯级先导闪电信号的多尺度熵进行比较。统计分析表明:不规则先导和直窜先导熵值随尺度先增加后趋于平稳,但熵值有很大差异;梯级先导熵值随尺度变化不明显,整体呈增长趋势,与不规则先导的熵值在大于3的尺度上也有所差异,因此当尺度大于3时可将熵值大于1.5的先导归类为不规则先导,熵值小于1.5的先导归类为梯级先导或直窜先导。不规则先导的特征熵平均值为2.0~2.1,最大值范围为2.6~2.8,最小值范围为1.51~1.59。  相似文献   

Predicting potential distributions of geographic events using one-class data: concepts and methods     

Q. Guo  W. Li  Y. Liu  D. Tong 《International journal of geographical information science》2013,27(10):1697-1715

One common problem with geographic data is that, for a specific geographic event, only occurrence information is available; information about the absence of the event is not available. We refer to these specific types of geospatial data as geographic one-class data (GOCD). Predicting the potential spatial distributions that a particular geographic event may occur from GOCD is difficult because traditional binary classification methods that require availability of both positive and negative training samples cannot be used. The objective of this research is to define GOCD and propose novel approaches for modelling potential spatial distributions of geographic events using GOCD. We investigate the effectiveness of one-class support vector machine (OCSVM), maximum entropy (MAXENT) and the newly proposed positive and unlabelled learning (PUL) algorithm for solving GOCD problems using a case study: species distribution modelling from synthetic data. Our experimental results indicate that generally OCSVM, MAXENT and PUL are effective in modelling the GOCD. Each method has advantages and disadvantages, but PUL seems to be the most promising method.  相似文献   

基于物理模型的起伏地表构造成像叠加速度分析研究     

张明  薛诗桂 《地球物理学进展》2013,28(3)

在起伏地表构造条件下,共中心点反射已不复存在,其波场特征较为复杂,速度分析时受浅层动校畸变影响较大,加上其他干扰因素,利用常规处理手段已很难得到较为准确的近地表构造和起伏地表浅层的叠加速度.为此,设计了两个物理模型,利用地震物理模拟实验数据采集系统对模型进行了数据采集.在采集到的地震物理模拟数据的资料处理过程中,对单炮记录进行向上延拓,然后再进行速度分析,并在动校正后多次调整叠加速度来得到视叠加速度,从而避免了浅层动校畸变大的影响.物理模型的模拟实验及处理结果表明,向上延拓是解决近地表构造和起伏地表浅层叠加速度的有效手段,通过向上延拓处理可以得到较为准确的近地表构造的视叠加速度,利用这样的叠加速度成像,可以得到近地表构造和起伏地表浅层构造较为真实有效的信息.  相似文献   

���ģ�����MPI���������㷨��������     

�ܺ�  ��־��  �Ӳ� 《大地测量与地球动力学》2014,34(5):120-124

?????С????????е????????????????????MPI?????????????????????Gauss??Jordan????????????????????????????????????д???洢????????????????????????????????????????????????????ж?дЧ????????????????????????Ч??????????????????Ч???????????????????????ж?д????С???????????????????????????????Ч???????60%??????????????????????????????????8??????????????????120??240??????????????????????229 s??7 395 s???????????????÷???205 MB??1.57 GB???????????10^-18??????????????????????????????С?????????????????  相似文献   

2012年7月27日陕北佳县特大暴雨天气的成因   总被引：1，自引：0，他引：1  

刘勇  郭大梅  胡启元 《干旱气象》2014,(3):424-430,438

利用常规高低空气象观测资料、地面逐小时降水、物理量、NCEP再分析资料和卫星云图,对2012年7月27日发生在陕北佳县的一次特大暴雨天气进行诊断分析,结果表明：暴雨前期副热带高压较强,当西风带的冷空气与副热带高压西北侧的西南暖湿气流交汇时,触发对流产生;低层700 hPa西南气流、850 hPa东南气流为特大暴雨提供了比较充沛的水汽;大气低层存在大量不稳定能量;高空200 hPa陕西北部位于浅槽的前部、急流入口区的右侧,存在正涡度平流,这一区域有强烈的辐散,提供了较强的上升运动,是特大暴雨产生的主要机制;在卫星云图上表现为一个水平尺度为200~400km、云顶亮温最低为-60℃,生命史为14 h的中-α尺度对流云团。  相似文献   

Flow exchange between the deep and shallow groundwaters in the Sbeϊtla synclinal basin (Tunisia): an isotopic approach     

Lassaad Dassi  Kamel Zouari  Klaus Peter Seiler  Serigne Faye  Samir Kamel 《Environmental Geology》2005,47(4):501-511

Stable (¹⁸O, ² H) and radiogenic (³H, ¹⁴C) isotopes of water have been used to constrain the source, origin, age, migration pathway and mixing processes in the Sbeïtla (Tunisia) system. The system is composed of an upper unconfined Middle Miocene aquifer with a variable thickness from 10–300 m, an intermediate confined/unconfined Lower Miocene aquifer about 100 m thick and a deeper confined Lower Cretaceous aquifer about 150 m thick separated by a thin clay layer. A total of 53 groundwater samples from the three aquifers and spring samples were collected during February and March 2000 and isotopically analysed using conventional methods. The stable isotopes composition of waters establishes that the deep groundwater (depleted as compared to present corresponding local rainfall) is ancient water recharged probably during the late Pleistocene and the early Holocene periods. The relatively recent water in the superficial aquifer is composed of mixed waters resulting presumably from upward leakage from the deeper groundwater. The radiogenic (³H, ¹⁴C) isotopes data confirm that the recent water, with a tritium content between 6.5 and 19 TU, represents post-nuclear recharge and the ancient groundwater with low carbon-14 contents between 7 and 26 pmC infiltrated between 8,000 to 20,000 years ago. When used in conjunction with the stable isotopes data, the mixing process can be clearly identified, especially in the Sbeïtla sill area. Groundwater of the upper aquifer exhibits isotopic signatures of both the old and recent waters. By using isotopic mass balance, the computed contribution of the deep groundwater in recharging the upper aquifer is up to 94%.  相似文献