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201.
On experimental setup in bioelectromagnetics 总被引:1,自引:1,他引:0
Bioeffects created by electromagnetic field (EMF) are the subject of intensive studies. This paper critically considers estimations
of exposure to EMF in bioelectromagnetic experiments. Results of calculations presented herein show the significant role of
the presence of conducting bodies (the exposure system) near an object under test on EMF energy absorption as well as mutual
interactions between simultaneously exposed objects. Our aims herein are twofold: firstly to find a way to refer measurement
results to free-space conditions in order to enable comparison of results obtained in different laboratories, and secondly
to show that EMF energy absorption in any exposed object is different and that this difference is a function of the size of
the exposure system, the number of exposed objects, and the particular properties (i.e., the electromagnetic structure) of
the objects. In the authors’ opinion the existence of interactions caused by the presence of the exposure system and other
exposed objects is a reason why remarkable differences are observed between experiments performed even under supposedly identical
conditions. The presented considerations and conclusion suggest wider participation of physicists and engineers in bioelectromagnetic
experiments in order to ensure the correctness of metrological aspects of these experiments. 相似文献
202.
Urbanization and its impact on groundwater: a remote sensing and GIS-based assessment approach 总被引:1,自引:0,他引:1
The perils of unplanned urbanization and increasing pressure of human activities on hydro-geomorphologic system often result
in modification of the existing recharge mechanism, which leads to many environmental consequences. In the present research,
an attempt has been made to investigate the applicability of remote sensing and geographical information system (GIS) in dealing
with spatial and temporal variability of dynamic phenomena, like urbanization and its impact on groundwater. This paper covers
primarily, quantitative and qualitative impacts of urban growth on the behavior of aquifer in Ajmer city (India). Urban growth
of the Ajmer city in last 17 years has been estimated from the satellite images. Database related to urbanization and groundwater
has been created in GIS. Groundwater recharge has been computed using a water balance approach known as Water Level Fluctuation
Methodology. Recharge estimation methodology has been implemented in GIS to introduce the spatial variability of hydro-geological
characteristics. Further, temporal and spatial variations in groundwater quality and quantity have been correlated with urban
growth using overlay analysis in GIS. The study reveals a general decline in water table and quality with urbanization. Further,
remote sensing and GIS technologies have been found useful in assessment of spatial and temporal phenomena of urbanization
and its impact on groundwater system. 相似文献
203.
From land cover change to land function dynamics: a major challenge to improve land characterization 总被引:36,自引:0,他引:36
Verburg PH van de Steeg J Veldkamp A Willemen L 《Journal of environmental management》2009,90(3):1327-1335
Land cover change has always had a central role in land change science. This central role is largely the result of the possibilities to map and characterize land cover based on observations and remote sensing. This paper argues that more attention should be given to land use and land functions and linkages between these. Consideration of land functions that provide a wide range of goods and services makes more integrated assessments of land change possible. The increasing attention to multifunctional land use is another incentive to develop methods to assess changes in land functions. A number of methods to quantify and map the spatial extent of land use and land functions are discussed and the implications for modeling are identified based on recent model approaches in land change science. The mixed use of land cover, land use and land function in maps and models leads to inconsistencies in land change assessments. Explicit attention to the non-linear relations between land cover, land use and land function is essential to consistently address land change. New methods to map and quantify land function dynamics will enhance our ability to understand and model land system change and adequately inform policies and planning. 相似文献
204.
Decision–support systems in the field of integrated water management could benefit considerably from social science knowledge,
as many environmental changes are human-induced. Unfortunately the adequate incorporation of qualitative social science concepts
in a quantitative modeling framework is not straightforward. The applicability of fuzzy set theory and fuzzy cognitive maps
for the integration of qualitative scenarios in a decision–support system was examined for the urbanization of the coastal
city of Ujung Pandang, Indonesia. The results indicate that both techniques are useful tools for the design of integrated
models based on a combination of concepts from the natural and social sciences.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
205.
Affum HA Oduro-Afriyie K Nartey VK Adomako D Nyarko BJ 《Environmental monitoring and assessment》2008,137(1-3):15-24
Lichens collected in an unpolluted forest (background) in November 2004, transplanted at 41 sampling sites along the Madina-Tetteh
Quarshie road, retrieved in February 2005 and analysed were found to contain higher concentrations of Manganese (Mn), Vanadium
(V), lead, Cadmium (Cd), Chromium (Cr) and Nickel (Ni) than in the background area. Observations showed that of all the heavy
metals studied, Manganese concentrations were highest at all sampling points with maximum values around a traffic light, an
intersection and car fitting/mechanic workshops. Significant correlations were found between Ni and Mn, Mn and Cr and Mn and
V. Statistical analysis also revealed a relatively even dispersion of the studied elements on the eastern side of the road
than on the western side. 相似文献
206.
Because of fast urban sprawl, land use competition, and the gap in available funds and needed funds, municipal decision makers
and planners are looking for more cost-effective and sustainable ways to improve their sewer infrastructure systems. The dominant
approaches have turned to planning the sanitary sewer systems within a regional context, while the decentralized and on-site/cluster
wastewater systems have not overcome the application barriers. But regionalization policy confers uncertainties and risks
upon cities while planning for future events. Following the philosophy of smart growth, this paper presents several optimal
expansion schemes for a fast-growing city in the US/Mexico borderlands—the city of Pharr in Texas under uncertainty. The waste
stream generated in Pharr is divided into three distinct sewer sheds within the city limit, including south region, central
region, and north region. The options available include routing the wastewater to a neighboring municipality (i.e., McAllen)
for treatment and reuse, expanding the existing wastewater treatment plant (WWTP) in the south sewer shed, and constructing
a new WWTP in the north sewer shed. Traditional deterministic least-cost optimization applied in the first stage can provide
a cost-effective and technology-based decision without respect to associated uncertainties system wide. As the model is primarily
driven by the fees charged for wastewater transfer, sensitivity analysis was emphasized by the inclusion of varying flat-rate
fees for adjustable transfer schemes before contracting process that may support the assessment of fiscal benefits to all
parties involved. Yet uncertainties might arise from wastewater generation, wastewater reuse, and cost increase in constructing
and operating the new wastewater treatment plant simultaneously. When dealing with multiple sources of uncertainty, the grey
mixed integer programming (GIP) model, formulated in the second stage, can further allow all sources of uncertainties to propagate
throughout the optimization context, simultaneously leading to determine a wealth of optimal decisions within a reasonable
range. Both models ran for three 5-year periods beginning in 2005 and ending in 2020. The dynamic outputs of this analysis
reflect the systematic concerns about integrative uncertainties within this decision analysis, which enable decision makers
and stakeholders to make all-inclusive decisions for sanitary sewer system expansion in an economically growing region. 相似文献
207.
Matteo Carpentieri Paolo Giambini Andrea Corti 《Environmental Modeling and Assessment》2008,13(3):415-429
Several wind tunnel experiments of tracer dispersion from reduced-scale landfill models are presented in this paper. Different
experimental set-ups, hot-wire anemometry, particle image velocimetry and tracer concentration measurements were used for
the characterisation of flow and dispersion phenomena nearby the models. The main aim of these experiments is to build an
extensive experimental data set useful for model validation purposes. To demonstrate the potentiality of the experimental
data set, a validation exercise on several mathematical models was performed by means of a statistical technique. The experiments
highlighted an increase in pollutant ground level concentrations immediately downwind from the landfill because of induced
turbulence and mean flow deflection. This phenomenon turns out to be predominant for the dispersion process. Tests with a
different set-up showed an important dependence of the dispersion phenomena from the landfill height and highlighted how complex
orographic conditions downwind of the landfill do not affect significantly the dispersion behaviour. Validation exercises
were useful for model calibration, improving code reliability, as well as evaluating performances. The Van Ulden model proved
to give the most encouraging results. 相似文献
208.
209.
We describe the development and parameterization of a grid-based model of African savanna vegetation processes. The model
was developed with the objective of exploring elephant effects on the diversity of savanna species and structure, and in this
formulation concentrates on the relative cover of grass and woody plants, the vertical structure of the woody plant community,
and the distribution of these over space. Grid cells are linked by seed dispersal and fire, and environmental variability
is included in the form of stochastic rainfall and fire events. The model was parameterized from an extensive review of the
African savanna literature; when available, parameter values varied widely. The most plausible set of parameters produced
long-term coexistence between woody plants and grass, with the tree–grass balance being more sensitive to changes in parameters
influencing demographic processes and drought incidence and response, while less sensitive to fire regime. There was considerable
diversity in the woody structure of savanna systems within the range of uncertainty in tree growth rate parameters. Thus,
given the paucity of height growth data regarding woody plant species in southern African savannas, managers of natural areas
should be cognizant of different tree species growth and damage response attributes when considering whether to act on perceived
elephant threats to vegetation. 相似文献
210.
Laluraj CM Krishnan KP Thamban M Mohan R Naik SS D'Souza W Ravindra R Chaturvedi A 《Environmental monitoring and assessment》2009,149(1-4):377-383
The scanning electron microscopy-energy dispersive spectroscopic (SEM-EDS) study of selected samples from an ice core collected from Central Dronning Maud Land (CDML), East Antarctica, revealed several microparticles. They are mainly siliceous and carbonaceous particles and have distinct variations in their shape and composition. The morphology and major element chemistry of the particles suggest their origin from either volcanic eruptions or continental dust. The EDS analysis revealed that the volcanic particles are enriched in silica (average SiO2 62%), compared to the continental dust particle (average SiO2 56%). We found that the tephra relating to Agung (1963) and Karkatau (1883) volcanic eruptions, as recorded, in the ice core harbored microbial cells (both coocoid and rods). The occurrence of organic and inorganic particles which bear relation to volcanic eruption and continental dust implies significant environmental changes in the recent past. 相似文献