基于最小二乘配置的GPS网平差模型及其应用

从最小二乘配置出发，推导了附加先验约束的高精度GPS网平差的参数估计和精度估计公式。分析了先验约束正确与否对平差结果所造成的影响，讨论了附加额外约束对平差结果及平差精度可能造成的影响，并提出了一个非常重要的用于确定附加约束是否有用的指标量。     

Definition of Exclusion Zones Using Seismic Data

—?In verifying compliance with the Comprehensive Nuclear-Test-Ban Treaty (CTBT), there is a motivation to be effective, efficient and economical and to prevent abuse of the right to conduct an On-site Inspection (OSI) in the territory of a challenged State Party. In particular, it is in the interest of a State Party to avoid irrelevant search in specific areas. In this study we propose several techniques to determine `exclusion zones', which are defined as areas where an event could not have possibly occurred. All techniques are based on simple ideas of arrival time differences between seismic stations and thus are less prone to modeling errors compared to standard event location methods. The techniques proposed are: angular sector exclusion based on a tripartite micro array, half-space exclusion based on a station pair, and closed area exclusion based on circumferential networks.     

GIS as a Tool for Seismological Data Processing

—?A computerized application of an integrated seismological GIS model is presented. An object oriented approach of the GIS topology is introduced and the special functions and features of this system are described. A network topology was selected to simulate the network characteristics of seismological data management and analysis. Each seismological entity is considered as a graphical data object, which is associated to other objects by predefined relationships. The graphical user interface introduced by GIS enables to handle seismological software routines and data in a more intuitive way. Examples of interactive processing of seismic waveforms for detecting, locating and characterizing seismic events using GIS visualization capabilities are presented. The benefits of this system during a passive seismic survey in the framework of the CTBT are highlighted.     

Time-stilled space-slowed: how boredom matters

This paper aims to fold the increased attention to issues of materiality in social and cultural geography into the more recent attunement to questions of affect. The vehicle for this aim is a discussion of the complex ways in which boredom, and bodies bored, compose time–space. Somewhat surprisingly, and in stark contrast to its experiential ubiquity, boredom has rarely been discussed within the social sciences. The paper therefore performs a geography of how boredom matters by way of a series of examples of the taking place of boredom drawn from research on music and everyday life. Rather than discuss boredom through the critical concepts that underpin the thesis of disenchantment, such as alienation or anomie, I argue that boredom takes place as a suspension of a body's capacities to affect and be affected forged through an incapacity in habit. Through this discussion I argue that the ‘new materialisms' that increasingly populate social and cultural geography struggle to discern the affectivity of profane social-life and, importantly, cannot conceive of the risk of depletion that boredom, via its connection to meaninglessness and indifference, exemplifies. However, attuning to the movement-from that always accompanies boredom discloses the immanent presence of intensities that on-go even as boredom stills and slows time–space. Based on the ambiguity of boredom that results, the conclusion draws on the ‘not-yet' materialism of Ernst Bloch [The Principle of Hope (vols. 1–3) (N. Plaice, S. Plaice, P. Knight, Trans.), Blackwell, Oxford, 1986] to disclose an image of process-matter that draws on Bennett's [The Enchantment of Modern Life. Attachments, Crossings and Ethics, Princeton University Press, Princeton and Oxford, 2001] concept of an ‘enchanted materialism' but retains a sense of process as incorporating both plentitude and depletion. The basis to this form of affective materialism is the event of hope.     

Impact of Climate Change on Agricultural Production in the Sahel – Part 2. Case Study for Groundnut and Cowpea in Niger

During the last 30 years, the climate of the West African Sahel has undergone various changes, especially in terms of rainfall. This has large consequences for the poor-resource farmers depending mainly on rainfed agriculture. This paper investigates the impacts of current climate variability and future climate change on groundnut and cowpea production in Niger for three major agricultural regions, including the groundnut basin.Niger was one of the largest West African groundnut producing and exporting countries. Groundnut production – as a cash crop – dropped fromabout 312,000 tons in the mid 1960s (about 68% exported) to as low as 13,000tons in 1988 and increased again to 110,000 tons in 2000. Cowpea, a food crop, showsa different tendency, going from 4,000 tons in the mid fifties to a maximum of 775,000 tons in 1997, and its cultivated area is still increasing. It is also a cash crop in local economies (especially for women).To highlight the impact of climate change on groundnut and cowpea production (significantly determined by rainfall in July, August and September), the following components of the rainfall regime were calculated for the period 1951–1998: mean annual and monthly rainfall, beginning, end and lengthof the rainy season, number of rainy days per month, amount of rainfall per rainy day and the maximum length of dry spell per month. Three sub-periods whose duration varied per region were defined: for Dosso 1951–1968,1969–1984 and 1985–1998; for Maradi 1951–1970, 1971–1987 and1988–1998; and for Zinder 1951–1966, 1967–1984 and 1985–1998. A change in rainfallregime components was observed between the three sub-periods, which were characterized in chronological order by wet, dry and intermediate conditions. To assess the impact of climate variability and change on groundnut and cowpea production, a statistical modeling approach has been followed, based on thirteen predictors as described and discussed in the preceding paper. Climate change is mimicked in terms of reduced total amount of rainfall for the three main rainfall months and an increased temperature, while maintaining other significant predictors at a constant level. In 2025,production of groundnut is estimated to be between 11 and 25% lower, while cowpeayield will fall maximally 30%. Various strategies to compensate thispotential loss are presented for the two crops.     

大别造山带构造归属：海西期以来地幔化学成分特征证据

通过对海西湘以来幔源岩石化学成分（特别是高度不相容元素对比值和具有相似性质的元素对比值）研究并与相邻构造单元（扬子板块北缘，华北板块南缘，北秦岭带，南秦岭带）地幔特征对比表明，大别造山带中海西期春秋庙－王母观辉长岩，碰撞后晚燕山早期镁铁－超镁铁质岩体（包括南，北大别造山带）以及产于大别造山带南部和扬子地块北缘的晚燕山晚期碱性玄武岩源区地，均具有富Sc,Cu,贫MgO，低Zr/Hf和高Rb/Sr,Ba/Sr,Ba/La,Nb/Ta,Yb/Hf等特征，源区地幔的这些特点与元古宙以来扬子地幔特征相似，而与华北地幔特征存在显著区别，反映大别造山带发育在扬子地幔上，根据大量的地质学，构造地质学，岩石学，地球物理及地球化学等研究结果，指出桐柏－商城－磨子潭－晓天断裂带是秦岭造山带中商丹断裂带的东延，综合研究证实大别造山带主体属南秦岭的组成部分。     

Evaluating magnetic lineations (AMS) in deformed rocks

Magnetic lineation in rocks is given by a cluster of the principal axes of maximum susceptibility (K_max) of the Anisotropy of Magnetic Susceptibility (AMS) tensor. In deformed rocks, magnetic lineations are generally considered to be the result of either bedding and cleavage intersection or they parallel the tectonic extension direction in high strain zones. Our AMS determinations, based on a variety of samples that were taken from mudstones, slates and schists from the Pyrenees and Appalachians, show that strain is not the only factor controlling the development of magnetic lineation. We find that the development and extent to which the magnetic lineation parallels the tectonic extension direction depends on both the original AMS tensor, which in turn depends on the lithology, and the deformation intensity. Rocks having a weak pre-deformational fabric will develop magnetic lineations that more readily will track the tectonic extension.     

Urban agriculture in Cameroon: an anti-politics machine in the making?

Urban agriculture in Africa is a growth area for development institutions and researchers. It is often portrayed as a coping strategy through which the urban poor have adapted to structural adjustment. It is enframed in an apolitical, ahistorical way because development institutions seek to create spaces into which development projects can be inserted in the future. This paper uses a case study from the town of Buea in south-west Cameroon to illustrate the differences between the international image of urban agriculture and its practice in one particular place. The increase in agricultural production in Buea in the 1990s initially appears to conform to the standard picture of urban farming as a recent, pragmatic and unplanned response to falling household incomes. However, such a portrayal neglects the history of urban farming, the pleasure that agriculture brings to farmers and the political consequences of expanding agricultural production. One of the concrete outcomes of increased urban agriculture in Buea in the 1990s has been to act as a `safety valve' against social unrest. It has acted as an `anti-politics machine'; a mechanism through which a sensitive political operation (reducing the salaries of civil servants) is achieved through apparently disconnected apolitical acts (enabling urban households to expand agricultural production). The Cameroonian government has opportunistically encouraged urban agriculture during a period of rapid economic change as one strategy for reproducing existing social relations.     

黄河源区生态环境恶化的现状及其原因

黄河是中华民族的母亲河 ,黄河流域是世界上著名的四大文明古国的发祥地之一。远古时代黄河流域气候湿润、水源丰富、土地肥沃。轩猿黄帝和他的沿黄部落就在这里开始创造中华文明。而今黄河下游常年发生断流 ,中游水土流失严重 ,河源区生态环境恶化 ,已引起我国政府和民众的关注。目前 ,防治黄河源区生态环境进一步恶化的研究工作必须加大力度 ,在财力、人力方面应给予更大的支持 ,及早编制该区治理生态环境的规划 ,加强环境保护措施     

Spatio-temporal fluctuations in the distribution and abundance of demersal fish and epibenthic crustaceans in Yaquina Bay,Oregon

A total of over 32,000 demersal fish and epibenthic crustaceans belonging to 62 species were caught in 42 biweekly trawls from 10 stations in Yaquina Bay, Oregon, during 1967 and 1968. English sole,Parophrys vetulus, was the most abundant species. Seventeen species (13 fishes and 4 crustaceans) constituted 95% of the catch. Total numerical abundances of both individuals (mainly juvenile fishes) and species were greatest in the lower 12 km of the estuary during summer and early fall, a period of water mass stability and increased water temperature and salinity. This section of the estuary is used by many immature fishes and crustaceans as a “nursery area”. These fishes generally emigrate from the estuary as subadults in the fall around the onset of the rainy season. The fewest species were taken in January 1968 from the central, upper-estuarine, and riverine areas of the bay, this being a time when high rainfall and river discharge result in low salinity and temperature. Crustaceans (shrimp and subadult crabs) were generally most abundant in late winter and early spring throughout the estuary. Changes in diversity indices reflected variations in community structure, the influence of migratory species and juvenile fishes, and seasonal changes in dominance. Year-to-year fluctuations in abundance may be due, in part, to local hydrographic and meteorological conditions along the central Oregon coast.