流动VLBI系统及其应用

本文首先探讨了影响流动VLBI系统性能及观测和解算精度的各种因素,提出了建立我国流动VLBI系统的一组参数指标;作为一个应用,探讨了用流动VLBI技术建立特级大地网对可能布设的全国GPS网的定向、尺度和定位控制与改善的情况。     

Seismicity of the Koyna region and regional tectonomagmatism of the Western Margin (India)

Recent findings on the Meso-Cenozoic tectonomagmatism and deep-seated anomalous geophysical structures suggest a close linkage between the seismicity of the Koyna region, the Westernghat uplift (WG-U) and associated thermomechanical and fluid activities. The WG-U seems to be the result of late Cretaceous thermal mobilization, erosion of the Deccan trap cover and superposition of compressional stress. The association of seismicity with uplift seems to result from movement of deep-seated heat and fluids/volatiles along the edges (or boundary faults) of the uplift; because the force required for crustal deformation depends on the relief. Observed gradients in relief may be attributed to the differential erosion-rates and heat inputs, due to the time gap of 50 Ma in the break-ups and plume activities on the eastern and western sides and consequence magmatism. Further, the geology and tectonics strongly indicate that the western margin (WM) is a relic of a mobile arm (MA), that included Madagascar, and which formed a part of the Proterozoic mobile belt of greater India (fort>85 Ma). The mobile nature of the WM facilitates mantle upwellings and transient elevation of isotherms at depth, raising the possibility of intermittent metamorphism and greater deformation.Superposition of the ongoing compression and uplift-induced forces make local permeability and pore-fluid pressure vital in triggering the seismic slip over the Peninsular shield. Certain representative model calculations have been carried out to estimate change in the e.m. induction characteristics caused by an intermittent hydraulic connectivity. The results show a drop in the resistivity which could be a useful monitoring index. The close connection of uplift and fluid activity as discussed here seems applicable for other active parts of the South Indian Shield (SIS) also.     

Unveiling hidden migration and mobility patterns in climate stressed regions: A longitudinal study of six million anonymous mobile phone users in Bangladesh

Climate change is likely to drive migration from environmentally stressed areas. However quantifying short and long-term movements across large areas is challenging due to difficulties in the collection of highly spatially and temporally resolved human mobility data. In this study we use two datasets of individual mobility trajectories from six million de-identified mobile phone users in Bangladesh over three months and two years respectively. Using data collected during Cyclone Mahasen, which struck Bangladesh in May 2013, we show first how analyses based on mobile network data can describe important short-term features (hours–weeks) of human mobility during and after extreme weather events, which are extremely hard to quantify using standard survey based research. We then demonstrate how mobile data for the first time allow us to study the relationship between fundamental parameters of migration patterns on a national scale. We concurrently quantify incidence, direction, duration and seasonality of migration episodes in Bangladesh. While we show that changes in the incidence of migration episodes are highly correlated with changes in the duration of migration episodes, the correlation between in- and out-migration between areas is unexpectedly weak. The methodological framework described here provides an important addition to current methods in studies of human migration and climate change.     

Understanding the bias of call detail records in human mobility research

ABSTRACT

In recent years, call detail records (CDRs) have been widely used in human mobility research. Although CDRs are originally collected for billing purposes, the vast amount of digital footprints generated by calling and texting activities provide useful insights into population movement. However, can we fully trust CDRs given the uneven distribution of people’s phone communication activities in space and time? In this article, we investigate this issue using a mobile phone location dataset collected from over one million subscribers in Shanghai, China. It includes CDRs (~27%) plus other cellphone-related logs (e.g., tower pings, cellular handovers) generated in a workday. We extract all CDRs into a separate dataset in order to compare human mobility patterns derived from CDRs vs. from the complete dataset. From an individual perspective, the effectiveness of CDRs in estimating three frequently used mobility indicators is evaluated. We find that CDRs tend to underestimate the total travel distance and the movement entropy, while they can provide a good estimate to the radius of gyration. In addition, we observe that the level of deviation is related to the ratio of CDRs in an individual’s trajectory. From a collective perspective, we compare the outcomes of these two datasets in terms of the distance decay effect and urban community detection. The major differences are closely related to the habit of mobile phone usage in space and time. We believe that the event-triggered nature of CDRs does introduce a certain degree of bias in human mobility research and we suggest that researchers use caution to interpret results derived from CDR data.     

南京市居民网络购物行为特征——以书籍和衣服为例

随着信息通讯技术(ICT)的飞速发展,网络购物日益成为当今社会经济生活的重要组成部分,深刻影响了居民的购物消费行为和传统零售业的发展。不同国家、不同人群、不同商品类型的居民购物行为具有一定差异。本文在问卷调查的基础上,分析南京市居民网络购物行为特征,并区分不同商品类型的居民网购行为特征差异,对理解网络购物和实体购物相互作用关系及网购对于交通出行和城市零售业空间的影响具有重要意义。结果表明：居民网络购物行为是一个复杂的过程,不同类型商品、不同频率网购人群在社会经济属性、空间特征、网络使用及购物习惯、购物态度上有明显差异,其中不同频率网购衣服的人群在特征上的差异更为显著,体验型商品对网络购物这一新型购物方式的响应更为强烈。     

Tools for a new climate conversation: A mixed-methods study of language for public engagement across the political spectrum

Political orientation and ideology are amongst the most significant influences on climate change attitudes and responses. Specifically, those with right-of-centre political views are typically less concerned and more sceptical about climate change. A significant challenge remains to move beyond this ideological impasse and achieve a more open and constructive debate across the political spectrum. This paper reports on novel mixed-methods research in the UK to develop and test a series of ‘narratives’ to better engage citizens with centre-right political views. Qualitative work in Study 1 revealed two particularly promising narratives. The first focused on the idea that saving energy is predicated on the ‘conservative’ principle of avoiding waste; the second focused on the advantages of ‘Great British Energy’ (based on patriotic support for domestic low-carbon technologies). An online experiment in Study 2 with a representative UK sample compared these narratives with a more typically left-of-centre narrative focused on the concept of ‘climate justice’ with a representative sample of the UK public. Results indicate that the first two narratives elicited broad agreement and reduced scepticism amongst centre-right participants, while the ‘climate justice’ narrative (which reflects a common environmental message framing) polarised audiences along political lines. This research offers clear implications for how climate change communicators can move beyond preaching to the converted and initiate constructive dialogue about climate change with traditionally disengaged audiences.     

Study mobile underwater positioning system with expendable and multi-functional bathythermographs

The purpose of the current study is to introduce a set of mobile underwater positioning systems (MUPS) that will enable non-offshore vessels to execute underwater missions. Besides mobility, the system would also possess the advantage of having to use fewer acoustic instruments than conventional acoustic positioning systems. The method adopted by the system will involve the use of expendable and multi-functional bathythermographs (XBT) to measure the underwater acoustic speed and the depth of water at the same time. Then it must utilize the geometric relations formed by measuring the position of underwater targets at set intervals during navigation. In addition, since sound does not travel in a straight line when underwater, the iteration and convergence method must be used to perform corrections on the transmission speed and positional errors to obtain an accurate coordinate of the underwater target. After simulation testing, the positioning system established by the current study has proven to be fast in converging the error values along with high positioning accuracy of the system. The results of the study indicate that the MUPS built by the research institute can be utilized on a vessel, and will be very helpful in assisting the management of urgent underwater positioning missions.     

Personalized risk messaging can reduce climate concerns

One potential barrier to climate policy action is that individuals view climate change as a problem for people in other parts of the world or for future generations. As some scholars argue, risk messaging strategies that make climate change personally relevant may help overcome this barrier. In this article, we report a large-n survey experiment on San Francisco Bay Area residents to investigate how providing spatially-resolved risk information to individuals shapes their climate risk perceptions in the context of sea-level rise. Our results suggest that personalized risk messaging can sometimes reduce concern about sea-level rise. These experimental effects are limited to respondents who believe that climate change is happening. Further, we do not find an effect of providing local risk messages on an individual's willingness to pay for regional climate adaptation measures. Our results emphasize that local messaging strategies around sea-level rise risks may not have the clear impacts that some advocates and scholars presume.     

An iconic approach for representing climate change

International and national greenhouse gas emissions reduction goals implicitly rely in part on individuals undertaking voluntary emissions reductions through lifestyle decisions. Whilst there is widespread public recognition of climate change as an issue, there are many barriers – cognitive, psychological and social – preventing individuals from enacting lifestyle decarbonisation. More effective climate change communication approaches are needed which allow individuals to engage meaningfully with climate change, thus opening new prospects for lifestyle decarbonisation. This study presents an iconic approach to engagement, tested in the UK context, which allows individuals to approach climate change through their own personal values and experiences. The iconic approach harnesses the emotive and visual power of climate icons with a rigorous scientific analysis of climate impacts under a different climate future. Although some climate icons already exist – for example the Thermohaline Circulation shutdown – these ‘expert-led’ icons fail to effectively engage ‘non-experts’. We demonstrate that the non-expert-led iconic approach helps overcome some of the cognitive and affective barriers that impede action towards lifestyle decarbonisation.     

大同地区几次中强震前后的重力变化

本文对华北北环重力重复测量资料进行了分析研究，探讨了排除浅层干扰因素，提取与地震相关的重力变化的途径。以大同地震为例，详细分析了地震前后重力场变化，结果表明，其变化是明显的，远远超过了各项误差。