Comparison of high-energy galactic and atmospheric tau neutrino flux

We compare the tau neutrino flux arising from the galaxy and the earth atmosphere for 10³E/GeV10¹¹. The intrinsic and oscillated tau neutrino fluxes from both sources are calculated. The intrinsic galactic ν_τ flux (E10³ GeV) is calculated by considering the interactions of high-energy cosmic-rays with the matter present in our galaxy, whereas the oscillated galactic ν_τ flux is coming from the oscillation of the galactic ν_μ flux. For the intrinsic atmospheric ν_τ flux, we extend the validity of a previous calculation from E10⁶ GeV up to E10¹¹ GeV. The oscillated atmospheric ν_τ flux is, on the other hand, rather suppressed. We find that, for 10³E/GeV5×10⁷, the oscillated ν_τ flux along the galactic plane dominates over the maximal intrinsic atmospheric ν_τ flux, i.e., the flux along the horizontal direction. We also briefly mention the presently envisaged prospects for observing these high-energy tau neutrinos.     

Fisheries: Hope or despair?

Recent work suggesting that fisheries depletions have turned the corner is misplaced because analysis was based largely on fisheries from better-managed developed-world fisheries. Some indicators of status show improvements in the minority of fisheries subjected to formal assessment. Other indicators, such as trophic level and catch time series, have been controversial. Nevertheless, several deeper analyses of the status of the majority of world fisheries confirm the previous dismal picture: serious depletions are the norm world-wide, management quality is poor, catch per effort is still declining. The performance of stock assessment itself may stand challenged by random environmental shifts and by the need to accommodate ecosystem-level effects. The global picture for further fisheries species extinctions, the degradation of ecosystem food webs and seafood security is indeed alarming. Moreover, marine ecosystems and their embedded fisheries are challenged in parallel by climate change, acidification, metabolic disruptors and other pollutants. Attempts to remedy the situation need to be urgent, focused, innovative and global.     

Integration of air pollution data collected by mobile sensors and ground-based stations to derive a spatiotemporal air pollution profile of a city

ABSTRACT

Air pollution has become a serious environmental problem causing severe consequences in our ecology, climate, health, and urban development. Effective and efficient monitoring and mitigation of air pollution require a comprehensive understanding of the air pollution process through a reliable database carrying important information about the spatiotemporal variations of air pollutant concentrations at various spatial and temporal scales. Traditional analysis suffers from the severe insufficiency of data collected by only a few stations. In this study, we propose a rigorous framework for the integration of air pollutant concentration data coming from the ground-based stations, which are spatially sparse but temporally dense, and mobile sensors, which are spatially dense but temporally sparse. Based on the integrated database which is relatively dense in space and time, we then estimate air pollutant concentrations for given location and time by applying a two-step local regression model to the data. This study advances the frontier of basic research in air pollution monitoring via the integration of station and mobile sensors and sets up the stage for further research on other spatiotemporal problems involving multi-source and multi-scale information.     

Skills in Professional Geography: An Assessment of Workforce Needs and Expectations

This study compares the skills of professional geographers and the needs of employer organizations across major sectors of the U.S. workforce. Following a series of focus groups, two surveys were developed to explore: (1) the extent to which specific skills were performed by geographers in different professional positions, and (2) the value of and anticipated demand for those skills from the perspective of employers. Overall, respondents in the focus groups and both surveys emphasized the need for general skills ranging from time management and writing ability to information management and computer literacy. Employers also cited many geographic skills as being vital for enhancing the work of professionals in all types of organizations. Competency in field methods, the ability to work across disciplinary boundaries, and spatial thinking were three skill areas that characterized the work of geographic professionals irrespective of specialty.     

Seismic performance of cable-sliding friction bearing system for isolated bridges

During past strong earthquakes, highway bridges have sustained severe damage or even collapse due to excessive displacements and/or very large lateral forces. For commonly used isolation bearings with a pure friction sliding surface, seismic forces may be reduced but displacements are often unconstrained. In this paper, an alternative seismic bearing system, called the cable-sliding friction bearing system, is developed by integrating seismic isolation devices with displacement restrainers consisting of cables attached to the upper and lower plates of the bearing. Restoring forces are provided to limit the displacements of the sliding component. Design parameters including the length and stiffness of the cables, friction coefficient, strength of the shear bolt in a fixed-type bearing, and movements under earthquake excitations are discussed. Laboratory testing of a prototype bearing subjected to vertical loads and quasi-static cyclic lateral loads, and corresponding numerical finite element simulation analysis, were carried out. It is shown that the numerical simulation shows good agreement with the experimental force-displacement hysteretic response, indicating the viability of the new bearing system. In addition, practical application of this bearing system to a multi-span bridge in China and its design advantages are discussed.     

Structure and taxonomic composition of free-living nematode and macrofaunal assemblages in a eutrophic subtropical harbour,Hong Kong

The spatial and seasonal taxonomic composition patterns of macrofauna and nematodes in a eutrophic subtropical harbour, previously suffered from sewage pollution, were studied in relation to a number of sediment parameters. In the polluted, inner-harbour area, levels of organic contents and heavy metals were high, whereas species number, abundance and diversity of nematodes and macrofauna were the lowest in comparison to the cleaner, outer-harbour area. Different taxonomic composition patterns of nematodes and macrofaunal assemblages were found between inner-harbour and outer-harbour area, which was highly correlated with sediment nutrient levels. Different responses of macrofaunal and nematode communities to sewage pollution suggested that macrofauna might be more tolerant than nematodes to eutrophic conditions due to their ability to modify the sediment. The present findings indicated the usefulness of studying both nematode and macrofaunal communities, in order to reveal different aspects of the benthic ecosystems in response to organic enrichment.     

基于基础设施性能的资产管理策略(英文)

基础设施的可持续发展需要系统地研究包括资产管理在内的基础设施管理的各个相关方面。本文构建了基于基础设施性能的资产管理策略的框架,并详细讨论了其主要原则与关键内容。     

A study on one-dimensional consolidation of layered systems

A general analytical solution, which is more explicit than the one given by Schiffman and Stein,¹ for the problem of one-dimensional consolidation of layered soils is presented. A relevant computer program is developed and the computed results on some examples are included. From these results, an in-depth study on the one-dimensional consolidation behaviour of layered systems is then made. It is demonstrated through these examples that both the solution technique and the computer program developed are very efficient. It is found that the effects of coefficients of permeability and volume compressibility of soil on the consolidation of layered systems are different and cannot be embodied into the coefficient of consolidation of soil. The stiffness of soil layer also plays an important role on the rate of consolidation.