基于Dreamlet变换的地震数据压缩理论与方法

为达到更加有效地表示地震数据的目的,仅仅将地震数据当作普通的图像数据处理是远远不够的,地震数据中蕴含的地震波的运动学特性也应作为重要因素而被考虑到.本文讨论了利用Dreamlet变换方法实现地震数据压缩的方法,并针对地震数据本身所蕴含的频散关系特性进一步提出了多尺度Dreamlet变换压缩方法.Dreamlet变换由2个一维局部谐波变换的张量积构成,它在提供地震波场时间-空间局部化性质的同时可以保留波场的运动学特性.通过对二维SEG/EAGE叠前、叠后数据的算例说明了Dreamlet变换用于地震数据压缩的有效性.利用压缩后的数据进行成像的结果更表明,与Curvelet变换方法相比,Dreamlet与多尺度Dreamlet方法可以提供更高的压缩比;在相同压缩比的条件下,使用Dreamlet与多尺度Dreamlet方法压缩重建后的数据进行成像能更好地保留成像结果中的重要结构.     

Reconstructing the migration patterns of late Pleistocene mammals from northern Florida, USA

We used analyses of the strontium isotope (⁸⁷Sr/⁸⁶Sr) ratios of tooth enamel to reconstruct the migration patterns of fossil mammals collected along the Aucilla River in northern Florida. Specimens date to the late-glacial period and before the last glacial maximum (pre-LGM). Deer and tapir displayed low ⁸⁷Sr/⁸⁶Sr ratios that were similar to the ratios of Florida environments, which suggest that these taxa did not migrate long distance outside of the Florida region. Mastodons, mammoths, and equids all displayed a wide range of ⁸⁷Sr/⁸⁶Sr ratios. Some individuals in each taxon displayed low ⁸⁷Sr/⁸⁶Sr ratios that suggest they ranged locally, while other animals had high ⁸⁷Sr/⁸⁶Sr ratios that suggest they migrated long distances (> 150 km) outside of the Florida region. Mastodons were the only taxa from this region that provided enough well-dated specimens to compare changes in migration patterns over time. Pre-LGM mastodons displayed significantly lower ⁸⁷Sr/⁸⁶Sr ratios than late-glacial mastodons, which suggests that late-glacial mastodons from Florida migrated longer distances than their earlier counterparts. This change in movement patterns reflects temporal changes in regional vegetation patterns.     

再论地震数据偏移成像

利用地震波正向传播方程对属于波形线性反演问题近似求解方法的地震数据偏移成像进行重新推导,得到了适合散射地震数据的散射偏移成像方法和适合反射地震数据的反射偏移成像方法.以地震波传播的散射理论为出发点,首先根据描述一次散射波正向传播的线性方程研究建立散射地震数据的偏移成像方法理论;利用高频近似对产生散射波场的地下速度扰动函数的空间变化进行近似,推导出地下反射率函数,再由散射波传播方程推导出基于反射率函数的反射波传播方程,然后根据描述一次反射波正向传播的线性方程研究建立反射地震数据的偏移成像方法理论.本文指出和修正了Claerbout偏移成像方法中的不足,提出的地震数据偏移成像方法是对当前偏移成像方法理论的完善,使反射地震数据偏移成像具有了更坚实的数学物理理论基础,得到的偏移成像结果相位正确、位置准确、分辨率提高.     

Neoliberal reforms in elder care in Norway: Roles of the state, Norwegian employers, and Polish nurses

After a worldwide financial crisis in the early 1980s, many states decided to implement new public management strategies. These strategies consist of private sector management practices that aim to reduce the cost of public services. The US and the UK first adopted the new public management model and other states soon followed. The Norwegian state was initially reluctant to adopt private management practices, but it eventually implemented modified reforms that suited the Norwegian socio-political context. This article investigates the ways in which the Norwegian state and Norwegian employers shape the labor force in Norwegian nursing homes through new public management strategies, and the tools that foreign-born nurses use to challenge these structures. The Norwegian state shapes the labor force through labor market policies and the rescaling of public services to local governments, and Norwegian employers reinforce the neoliberal values of the state in their hiring practices and daily operations in the workplace. In particular, this article analyzes the interweaving neoliberal institutional and personal factors that influence the working experiences of Polish nurses in a semi-private nursing home in Oslo. The city of Oslo created a unique public–private partnership with a city-owned company that manages three nursing homes in Oslo. The findings of this study indicate that Polish nurses in one of these nursing homes were negatively affected by the new public management strategies. They improved some of their working conditions over time but structural barriers still persist despite high demand for their skills.     

Modeling network autocorrelation within migration flows by eigenvector spatial filtering

Although the assumption of independence among interaction flows frequently is engaged in spatial interaction modeling, in many circumstances it leads to misspecified models and incorrect inferences. An informed approach is to explicitly incorporate an assumed relationship structure among the interaction flows, and to explicitly model the network autocorrelation. This paper illustrates such an approach in the context of U.S. interstate migration flows. Behavioral assumptions, similar to those of the intervening opportunities or the competing destinations concepts, exemplify how to specify network flows that are related to particular origin–destination combinations. The stepwise incorporation of eigenvectors, which are extracted from a network link matrix, captures the network autocorrelation in a Poisson regression model specification context. Spatial autocorrelation in Poisson regression is measured by the test statistic of Jacqmin-Gadda et al. (Stat Med 16(11):1283–1297, 1997). Results show that estimated regression parameters in the spatial filtering interaction model become more intuitively interpretable.

第四纪水泉尖山-崛峿山南麓断裂带活动的迁移及其机制

位于甘肃靖远地区的水泉尖山-崛峿山南麓断裂带早第四纪前为走向逆断 层,第四纪中期出现左旋走滑迹象。研究结果表明,水泉尖山-崛峿山南麓断裂带断裂 活动的横向迁移与海原活动断裂带的形成和强烈活动有着密切的关系。     

基于腾讯迁徙数据的中国城市群国庆长假城际出行模式与网络特征

城际出行具有时间依赖性,不同时间约束与特定时期的城际出行具有相异性,反映的出行模式与表达的地理空间联系规律具有差异性。迁徙大数据记录的人口移动实时记录为开展基于时间依赖的城际出行网络提供了可能。本文以全国 19个城市群为研究区域,利用腾讯平台提供的居民城际出行数据,对国庆长假期间（2016年10月1—7日）中国城市群城际出行时段变化特征、城际出行模式及其网络结构进行了研究。结果表明：① 黄金周城际出行具有明显的基于出行期、返程期和旅途期的时段变化规律;② 国庆长假期间的中国城市群城际出行分别形成了轴辐式、多中心与单中心3种城际出行模式; ③ 出行期、返程期的城际出行具有类似于春运人口流动的时空对称规律,城市群城际出行呈现出以主要城市群整体、城市群核心城市与邻近外围城市间的中短距离流动的长假出行特征,中西部城市群城际出行具有典型的“潮汐式”流动特征;④ 基于腾讯人口迁徙大数据,通过对黄金周期间出行期、返程期与旅途期的科学划分,较好地实现了国庆长假城际出行特征与模式的挖掘,同时也为长假城际交通管理与道路资源优化调配方案的制定提供支撑。     

Challenging climate change and migration discourse: Different understandings of timescale and temporality in the Maldives

This article draws on ongoing research in the Maldives to explore differences between elite and non-elite perceptions of climate change and migration. It argues that, in addition to variations in perceptions based on diverse knowledge, priorities and agendas, there exists a more fundamental divergence based upon different understandings of the timescale of climate change and related ideas of urgency and crisis. Specifically, elites tend to focus on a distant future, which is generally abstracted from people's everyday lived realities, and to utilise the language of a climate change-induced migration ‘crisis’ in their discussions about impacts in a manner not envisaged by non-elites. The article concludes that, rather than unproblematically mapping global, external facing narratives wholesale onto ordinary people's lives and experiences, there needs to be more dialogue between elites and non-elites on climate change and migration issues. These perspectives should be integrated more effectively into the development of policy interventions designed to support people in adapting to the impacts of global environmental change.     

断层垂向封油气性综合定量评价方法探讨及应用

在断层垂向上封油气机理及影响因素分析的基础上,通过物理模拟建立了原油通过断裂带运移速度与断层填充物粒度、倾角和泥质含量之间的函数关系。根据断裂带粒度、泥质含量和倾角,基于求取油气通过断裂带运移速度的大小,建立了利用油气通过断裂带运移速度研究断层垂向封油气性的综合定量评价方法。将该方法分别应用于库车坳陷克拉2气田和车古20潜山主要断层垂向封气和油性评价中,评价结果与实际地质条件吻合较好,表明该方法用于评价断层对油气的垂向封闭性均是可行的,是一种综合定量的评价方法。     

Defining geographical mobility: Perspectives from higher education

Context is generally overlooked when selecting measures to define geographical mobility in mobility and migration research. This paper contributes to a discussion on the importance of context when defining geographical mobility and draws on examples from higher education in Sweden. Using binary logistic regression, statistical outcomes are compared when different measures of mobility to and mobility from higher education are employed. The measures produce different statistical outcomes, and these differences are illuminated when comparing results of common measures of mobility (e.g. crossing administrative boundaries or moving a certain distance) against two measures constructed specifically for Swedish higher education-related mobility. The results indicate that using municipality boundaries for measuring mobility in the Swedish higher education context is particularly inappropriate because the measure does not differentiate commuters from movers. This challenge surfaces because mobility must be determined in relation to the locations of students’ higher education institutions since administratively registered moves are unreliable in the educational context. These findings emphasize the importance of considering the geographical locations and characteristics of higher education institutions in addition to feasible commuting possibilities in research on higher education-related mobility. The two measures developed for the Swedish higher education context are identified as most appropriate because they center on the geographical distribution of higher education, and this distribution is perceived as having an important role in influencing mobility in this context. Consequently, this study accentuates the need for considering the geographical arrangement of resources (e.g. schools, hospitals) relevant to the context under investigation when determining measures to define mobility.