Stream Database Research Articles

Spatial data for modelling and management of freshwater ecosystems

Fluvial habitats are inherently variable. They are shaped by flow magnitude, frequency, timing and duration, by the effects of upstream and downstream features along flow paths and by bioclimatic processes and human activities in upstream contributing catchments. Managing freshwater ecosystems requires tools and data that effectively account for these multi-scale processes. We tackle these challenges in this analysis of the distribution of 17 native and alien fish species in south-eastern Australia. A fine-scale, stream-link-based GIS database comprising an extensive set of ecologically meaningful attributes at multiple scales was developed to characterise the multidimensional environmental space of freshwater biota. This article describes the methods and data required to construct such a database. Boosted regression tree models were employed to analyse relationships between species and 20 candidate environmental predictors. For some species, competitors/predators were also included as predictors. Models were evaluated from several viewpoints: the ecological plausibility and intuition arising from them, their ability to predict to river links within the training area and for 11 species for which data were sufficient, their ability to predict to an adjacent but geographically distinct region. Despite modest environmental contrasts in the study area, these data and species distribution models (SDMs) produced predictions with useful predictive ability and discriminatory power. Critically, predictors of distribution identified as important for the various species modelled were ecologically interpretable. Several – but not all – of the models tested for transferability also predicted distributions reasonably well in the adjacent region. The GIS stream database and SDMs have immediate applications, but also provide a valuable foundation for developing more sophisticated tools for management and conservation in Australian freshwater environments.

The Determinants of Capital Structure: An Empirical Study of Listed Firms on the Vietnamese Stock Exchange

Since the appearance of the pioneering work of Modigliani and Miller (1958, 1963) has created a system of theoretical foundations of corporate finance theory. There have been numerous studies to clarify the Modigliani and Miller theory, but most of empirical studies have been carried out in the developed countries and few studies are mentioned in the context of developing countries. This paper will attempt to fill the gap of the determinants of capital structure in developing countries through conducting an empirical analysis of capital structure of listed companies in Thailand, Malaysia, China and Vietnam. In addition, this study will address the impact of ownership structure of the capital structure of enterprises in Vietnam. Indeed, the capital structure of Vietnamese enterprises has a number of features that are different to other countries. These differences come from the specific characteristics of the economy and capital structure of Vietnam, where most of companies belong to state. However, along with the shift from a centralized economy to the market-oriented economy there is growing participation by privately owned companies and foreigners as shareholders in Vietnam companies. This study will use panel data for listed companies from the countries Thailand, Malaysia, China and Vietnam in the period from 2004 to 2009. Capital structure and firm attributed information will be collected from the Data Stream, Thomson Reuters and Osiris databases. To analyze these data, econometric methods such as ordinary least squares (OLS) and generalized method of moments (GMM) will be used to explore the relationship between financial factors as well as non-financial factors and capital structure choice. Based on the findings, there will be comparisons between countries as well as explanations for the similarities and differences.

情報システム運用におけるストリームDBによるメッセージ分析方式

Based upon survey conducted by the authors to large scale data centers, monitoring of messages produced by operating systems, middleware and applications is widely adopted as a method for detecting system failures and malfunctions. According to the result of survey, not only the monitoring of message occurrences, but also analyzing message occurrences in particular patterns is used. Those patterns include, multiple occurrences surpassing a threshold in a predefined time period, consecutive occurrences within a predefined time period, or occurrences violating predefined sequences and so on. A custom made application is currently used for message analysis. Some problems are known in operation of the application and implementation of patterns of message analyzing. The authors proposed a message analyzing mechanism for information system management using stream database to overcome these problems and proved its effectiveness by experiments.

Managing Frequent Updates in R-Trees for Update-Intensive Applications

Managing frequent updates is greatly important in many update-intensive applications, such as location-aware services, sensor networks, and stream databases. In this paper, we present an R-tree-based index structure (called Rsb-tree, R-tree with semibulk loading) for efficiently managing frequent updates from massive moving objects. The concept of semibulk loading is exploiting a small in-memory buffer to defer, buffer, and group the incoming updates and bulk-insert these updates simultaneously. With a reasonable memory overhead (typically only 1 percent of the whole data set), the proposed approach far outperforms the previous works in terms of update and query performance as well in a realistic environment. In order to further increase buffer hit ratio for the proposed approach, a new page-replacement policy that exploits the level of buffered node is proposed. Furthermore, we introduce the concept of deferring threshold ratio (dtr) that simply enables deferring CPU- and I/O-intensive operations such as node splits and removals. Extensive experimental evaluation reveals that the proposed approach is far more efficient than previous approaches for managing frequent updates under various settings.

Query scheme and its optimization for distributed data stream

Stream database system is a new type of database system designed to facilitate the execution of queries to continuous streams of data.Many stream-based applications are inherently distributed.Since input stream rates and other system parameters such as the amount of available computing resources can fluctuate significantly,a stream query plan must be able to adapt to these changes.This paper proposed a distributed stream query plan and optimized,and defined performance metrics for response time and system throughput.The experimental result proves that this plan is optimal compared with other plans.

Variability in wintertime position and strength of the North Pacific jet stream as represented by re‐analysis data

AbstractThe popular National Center for Environmental Prediction (NCEP)/National Center for Atmospheric Research (NCAR) re‐analysis database was used to create a mean winter seasonal jet stream database for the northern Pacific Ocean region for the period 1948–1949 through 2004–2005. Grids of mean seasonal 300 hPa scalar wind were used to determine the latitudinal position of the primary mid‐latitude jet on a longitudinal resolution of 2.5° from eastern Asia to western North America. The position and strength of the jet stream across this region are key determinants of winter precipitation variability downstream across the predominantly arid western region of North America.Results show that the latitudinal position of the jet exhibits greater variance over the eastern half of the northern Pacific Ocean, while the greatest variance in the speed of the seasonal jet occurs across the central northern Pacific Ocean. A statistically significant increase in the speed of the mean seasonal jet occurred over the central area of the northern Pacific Ocean during the last half of the 20th century. A spatially consistent but statistically insignificant trend toward a more southerly position of the jet occurred during the study period. The results do not confirm current theories of a general pole‐ward shift in mid‐latitude jet streams in association with recent and future climate change, suggesting that such an observed or theoretical hemispheric shift may not necessarily be evident within a particular region or that any shift over the last 50 years has been less than the 2.5° resolution of the NCEP/NCAR dataset. The jet stream data support the connection between the jet and the Pacific‐North American atmospheric teleconnection pattern and between the jet and the oscillation of sea surface temperature anomalies in the northern Pacific Ocean known as the Pacific Decadal Oscillation. Copyright © 2008 Royal Meteorological Society

MedSMan: a live multimedia stream querying system

Querying live media streams is a challenging problem that is becoming an essential requirement in a growing number of applications. Research in multimedia information systems has addressed and made good progress in dealing with archived data. Meanwhile, research in stream databases has received significant attention for querying alphanumeric symbolic streams. The lack of a data model capable of representing different multimedia data in a declarative way, hiding the media heterogeneity and providing reasonable abstractions for querying live multimedia streams poses the challenge of how to make the best use of data in video, audio and other media sources for various applications. In this paper we propose a system that enables directly capturing media streams from sensors and automatically generating more meaningful feature streams that can be queried by a data stream processor. The system provides an effective combination between extendible digital processing techniques and general data stream management research. Together with other query techniques developed in related data stream management streams, our system can be used in those application areas where multifarious live media senors are deployed for surveillance, disaster response, live conferencing, telepresence, etc.

Query processing of multi-way stream window joins

This paper introduces a class of join algorithms, termed W-join, for joining multiple infinite data streams. W-join addresses the infinite nature of the data streams by joining stream data items that lie within a sliding window and that match a certain join condition. In addition to its general applicability in stream query processing, W-join can be used to track the motion of a moving object or detect the propagation of clouds of hazardous material or pollution spills over time in a sensor network environment. We describe two new algorithms for W-join and address variations and local/global optimizations related to specifying the nature of the window constraints to fulfill the posed queries. The performance of the proposed algorithms is studied experimentally in a prototype stream database system, using synthetic data streams and real time-series data. Tradeoffs of the proposed algorithms and their advantages and disadvantages are highlighted, given variations in the aggregate arrival rates of the input data streams and the desired response times per query.

Modeling the Concentration of Aluminum in Surface Waters

Although the increased mobilization of aluminum from soils to surface waters is widely recognized as one of the most important ecological effects of acidic deposition, lumped-parameter mathematical models of acidification response typically overestimate the change in Al concentration under changing deposition by a considerable margin. The assumption of equilibrium with gibbsite (Al(OH)3) in the MAGIC model and other models of acid-base chemistry is shown to be inconsistent with measured values for a large variety of lake and stream databases. A modified algorithm for predicting Al concentration, based on empirical relationships evident in field data, provided superior estimates of changes in Al concentration in three long-term monitoring data sets and under experimental conditions at two experimental watershed manipulation sites.

Developing nutrient targets to control benthic chlorophyll levels in streams: A case study of the Clark Fork River

Approaches for assessing the effects of lowering nutrients on periphyton biomass in streams and rivers are poorly developed in contrast to those for lakes. Here we present two complementary approaches to assess target nutrient concentrations in streams, given desired mean and maximum standing crops of benthic algal chlorophyll. In the first approach, a reference portion or reach of the river that typically exhibits acceptable levels of benthic chlorophyll is identified (i.e. seasonal mean and maximum values do not exceed desirable levels), and the target levels for instream nutrient concentrations are defined by mean nutrient levels in the reference region. In the second approach, regression and graphical analysis of a large stream database are used to identify acceptable levels of instream total N and total P. The first approach supplies site-specific nutrient targets, whereas the second places nutrient control into a broader, more comparative perspective. In order to link these target concentrations to specific nutrient control measures, we describe a spreadsheet model that can be used to translate changes in external loading by point sources into predicted new instream nutrient concentrations. These quantitative methods are applied here to the control of nuisance algal growth in the Clark Fork River, Montana. We suggest that, in general, maintenance of mean instream total N concentrations below 350 μg l −1 and total P below 30 μg l −1 will result in mean benthic algal chlorophyll a density below nuisance levels of 100 mg m −2 in most streams.

Orientation studies of stream water hydrogeochemistry for environmental and economic applications in North Wales

s 91 Orientation studies of stream water hydrogeochemistry for environmental and economic applications in North Wales P.R. Simpson 1, W.M. Edmunds 2, N. Breward 1, J.M.Cook 3, D. Flight 1 G.E.M. Hall4and T.R. Lister 1 1Geochemistry Group, British Geological Survey Nottingham NG12 5GG. UK 2Hydrogeology Group, British Geological Survey, Wallingford, OXlO 8BB, UK 3Analytical Geochemistry Group, British Geological Survey, Nottingham, NG 12 5GG, UK 4Geological Survey of Canada, 601 Booth Street, Ottawa, Ontario, KIA OE8, Canada The stream water hydrogeochemical database, prepared by the BGS's Geochemical Survey Programme in conjunction with databases for stream sediments , soil samples and mineral concentrates, has recently 'been enhanced for a range of economic and environmental objectives. The density of systematic stream water sampling and analysis has been increased to one sample per km 2 and a much broader spectrum of additional determinands introduced. An orientation suite of coregistered hydrogeochemical maps has been produced from water samples collected at 1,279 sample sites in North Wales. The preliminary results obtained indicate that bedrock geology and mineralisation are the most important variables which influence the surface water chemistry. These primary geological parameters are variously modified by secondary influences which include a tmospher ic (c l imat ic and coastal effects) , a n t h r o p o g e n i c ( ag r i cu l tu re and urban developments) and geomorphological factors. Such regional hydrogeochemical stream water maps have a wide range of economic and environmental appl icat ions, especial ly when interpreted in conjunction with geological data. Results obtained so far indicate that interpretation is likely to be further enhanced in the future by comparison with regional stream sediment , hydrogeolog ica l , geomorphologica l , pedological , agricultural, landuse, climatic and remotely sensed datasets in a GIS environment. Hydrogeochemical sampling and analysis therefore represents a costeffective addition to the Regional Geochemical Survey of the UK. The identification of mining related contamination in the UK using high resolution geochemical mapping: examples from Northeast England and North Wales D.M.A. Flight, T.R. Lister and F.M. Fordyce Geochemistry Group, British Geological Survey, Nottingham NG 12 5GG, UK The Geochemical Survey programme (GSP) of the BGS is currently undertaking the systematic multi-element regional geochemical mapping of the UK landmass° The GSP database presently holds information on the concentration of up to 35 elements determined in stream sediment, stream water, heavy mineral concentrate and soil samples collected at an average aensity of one sample per 1.25 km 2 in an area of northern Britain extending f rom S h e t l a n d to Nor th Wales. R e g i o n a l geochemical maps based on analysis of high density stream sediment samples from Northeast England and North Wales, both of which contain historically important mining fields are considered here. The Northern Pennine Orefield has been worked from Roman times until the early parts of this century primarily for galena but also for associated Zn, Ba and Cu bearing ores. The many historical mining centres of North Wales include Halkyn-Minera (Pb-Zn), Llanlwst (Pb-Zn), Llansannan (Cu-Pb-Zn), Beddgeler t (Cu-Pb-Zn) and Parys Mountain, Anglesey (Cu).