Open Access. Powered by Scholars. Published by Universities.®
- Discipline
- Institution
- Publication
- Publication Type
Articles 1 - 22 of 22
Full-Text Articles in Entire DC Network
A Hydrothermal After-Ripening Time Model Of Seed Dormancy Loss In Bromus Tectorum, Necia Beck Bair
A Hydrothermal After-Ripening Time Model Of Seed Dormancy Loss In Bromus Tectorum, Necia Beck Bair
Theses and Dissertations
After-ripening, the process of seed dormancy loss in dry storage is associated with a decrease in the mean base water potential, one of the parameters of hydrothermal time. The rate of change of the mean base water potential is assumed to be a linear function of temperature above a specific base temperature and as a result can be described by a thermal after-ripening (TAR) time model, an extension of hydrothermal modelling. The thermal requirement for after-ripening is the thermal time necessary for the modelling base water potential of the seed to shift from its original value to its final value. …
Generic Process-Based Plant Models For The Analysis Of Landscape Change, B. Reineking, A. Huth, C. Wissel
Generic Process-Based Plant Models For The Analysis Of Landscape Change, B. Reineking, A. Huth, C. Wissel
International Congress on Environmental Modelling and Software
The analysis of landscape change impacts on community composition and dynamics is difficult for species rich plant communities, because of their high complexity. One approach to deal with this challenge are generic process-based models. In these models, the species are described by a common set of parameters and functional responses. Thus, they allow both the integration of knowledge on key processes, and a common description for several ecological patterns. An important aspect of these models are trade-offs in the species’ physiological and life-history traits, which prevent ‘super-species’ that dominate under all environmental conditions. We compare process-based models with two other …
Integrated Assessment Of Water Stress In Ceará, Brazil, Under Climate Change Forcing, Maarten S. Krol, Pieter R. Van Oel
Integrated Assessment Of Water Stress In Ceará, Brazil, Under Climate Change Forcing, Maarten S. Krol, Pieter R. Van Oel
International Congress on Environmental Modelling and Software
Surface water is the main source of fresh water supply in Ceará, lying in the semi-arid Northeast of Brazil.
Dealing With Unidentifiable Sources Of Uncertainty Within Environmental Models, Ann Van Griensven, T. Meixner
Dealing With Unidentifiable Sources Of Uncertainty Within Environmental Models, Ann Van Griensven, T. Meixner
International Congress on Environmental Modelling and Software
Sources of Uncertainty Global Assessment using Split SamplES (SUNGLASSES) is a method for assessing model global uncertainty to aid in the development of integrated models. The method is complementary to the commonly investigated input and parameter uncertainty, as it accounts for errors that may arise due to unknown or unassessable sources of uncertainty, such as model hypothesis errors, simplifications, scaling effects or the lack of the observation period to represent long-term variability and fluctuations in the system. Such sources are typically dominant for most environmental models and they undermine the reliability of environmental models. The SUNGLASSES algorithm directly estimates the …
Operational And Forecasting Real-Time Air Quality Tool For Industrial Plants, R. San José, J. L. Pérez, R. M. González
Operational And Forecasting Real-Time Air Quality Tool For Industrial Plants, R. San José, J. L. Pérez, R. M. González
International Congress on Environmental Modelling and Software
A tool (TEAP) to evaluate in real-time and operational mode the air quality produced by industrial plants (power plants also) has been developed based on the third generation of air quality modelling systems. The system uses the non-hydrostatic mesoscale meteorological model MM5 (PSU/NCAR, USA) and the air quality modelling system (transport and chemistry) CMAQ (Community Multiscale Air Quality Modelling System) (EPA, USA) by using the so-called ON/OFF scenario which allows the user to have in advance (48 - 72 hours) a detailed information in time and space on what is the relative impact of the industrial emissions in an area …
Uncertainty In The Water Framework Directive: Implications For Economic Analysis, J. Myšiak, K. Sigel
Uncertainty In The Water Framework Directive: Implications For Economic Analysis, J. Myšiak, K. Sigel
International Congress on Environmental Modelling and Software
The Water Framework Directive (WFD) imposes a new approach to water resource management in the EU states. Uncertainty surrounding its implementation, however, could badly affect the achievement of the objectives set by the Directive. Although not directly linked to a set of techniques to deal with it, the WFD and accompanying guideline documents identify uncertainty as a factor likely to play a significant role in assessing the risk of failing to achieve the objectives and setting up the required programmes of measures. In this paper, by addressing the initial description of a river basin we analyse uncertainty in socioeconomic descriptors …
Integration Of Moneris And Great-Er In The Decision Support System For The German Elbe River Basin, Jürgen Berlekamp, Neil Graf, Oliver Hess, Sven Lautenbach, Silke Reimer, Michael Matthies
Integration Of Moneris And Great-Er In The Decision Support System For The German Elbe River Basin, Jürgen Berlekamp, Neil Graf, Oliver Hess, Sven Lautenbach, Silke Reimer, Michael Matthies
International Congress on Environmental Modelling and Software
The Elbe-DSS is a tool for integrated river basin management of the German part of River Elbe basin. Various simulation models are used to assess the impact of measures such as reforestation, changes of agro-practices or efficiency of wastewater treatment plants and of external scenarios on a set of management objectives. For the assessment of nutrient and pollutant loads and impacts, MONERIS and GREAT-ER are integrated in the Elbe-DSS. MONERIS calculates nutrient inputs from diffuse and point sources on a sub catchment scale of about 1,000 km². GREAT-ER was developed as a tool for exposure assessment of point source emissions …
Forecasting Municipal Solid Waste Generation In Major European Cities, P. Beigl, Gudrun Wassermann, F. Schneider, Stefan Salhofer
Forecasting Municipal Solid Waste Generation In Major European Cities, P. Beigl, Gudrun Wassermann, F. Schneider, Stefan Salhofer
International Congress on Environmental Modelling and Software
An understanding of the relationships between the quantity and quality of environmentally relevant outputs from human processes and regional characteristics is a prerequisite for planning and implementing ecologically sustainable strategies. Apart from process-related parameters, continuous and discontinuous socio-economic long-term trends often play a key role in the assessment of environmental impacts. This paper describes the development of a prognosis model for municipal solid waste (MSW) generation in European regions. The objective is to assess future municipal waste streams in major European cities. We therefore focussed on cities, which face significant social and economic changes, e.g. in central and east European …
Flood Frequency Quantification For Ungauged Sites Using Continuous Simulation: A Uk Approach, A. Calver, A. L. Kay, D. A. Jones, T. Kjeldsen, N. S. Reynard, S. Crooks
Flood Frequency Quantification For Ungauged Sites Using Continuous Simulation: A Uk Approach, A. Calver, A. L. Kay, D. A. Jones, T. Kjeldsen, N. S. Reynard, S. Crooks
International Congress on Environmental Modelling and Software
The paper outlines recent and ongoing research addressing the quantification of river floodfrequencies at ungauged sites across Britain. The approach is one of modelling continuous time series ofcatchment runoff. Model parameters are established where data permit: the spatial generalisation toungauged sites is effected by relating model parameters to widely available catchment properties which thenprovide the route to model use in data-sparse areas. The particular aspects of research described are (i) themerging of data of different time discretisation, (ii) considerations in the calibration of parameter-sparserainfall-runoff models, (iii) considerations of site similarities in spatial generalisation and (iv) quantificationof uncertainties arising from parameter …
Chemometrics Modelling Of Environmental Data, Roma Tauler, Emma Peré-Trepat, Silvia Lacorte, Damià Barceló
Chemometrics Modelling Of Environmental Data, Roma Tauler, Emma Peré-Trepat, Silvia Lacorte, Damià Barceló
International Congress on Environmental Modelling and Software
Environmental monitoring studies produce huge amounts of concentration values of chemicalsspread at distant geographical sites and during different time periods. Moreover, the content of chemicals isalso estimated at different environmental compartments (i.e. air, water, sediments, biota...). All these datavalues are difficult to cope and evaluate in a simple and fast way using simple univariate statistical tools,specially due to their large number and to their multivariate correlation. In order to discover relevant patternswithin large multivariate data sets, the application of modern chemometric methods based in statisticalmultivariate data analysis and in Factor Analysis is proposed. The basic assumption of chemometric methodsis that …
Air Quality Modelling In Latvia, I. Steinberga, L. Lizuma
Air Quality Modelling In Latvia, I. Steinberga, L. Lizuma
International Congress on Environmental Modelling and Software
As a potential member country to the European Union (EU), Latvia has harmonized the nationalenvironmental legislation with the EU air quality (AQ) legislation. The AQ management system in thecountry is being developed in accordance with the requirements laid down in the appropriate EU directivesthus introducing advanced management tools based on the AQ modelling. According to the Latvianlegislation, the simple empirical model, “Ecolog” (Russia), should not be used for air quality modelling. Thenew tool for pollution dispersion assessment and management, EnviMan, OPSIS AB Company, Sweden wasobtained by the Latvian Hydrometeorological Agency in 1998. Initially it was used only for processing andstorage …
Incorporating Level Set Methods In Geographical Information Systems (Gis) For Land-Surface Process Modeling, D. Pullar
International Congress on Environmental Modelling and Software
Land-surface processes include a broad class of models that operate at a landscape scale. Currentmodelling approaches tend to be specialised towards one type of process, yet it is the interaction of processesthat is increasing seen as important to obtain a more integrated approach to land management. This paperpresents a technique and a tool that may be applied generically to landscape processes. The technique tracksmoving interfaces across landscapes for processes such as water flow, biochemical diffusion, and plantdispersal. Its theoretical development applies a Lagrangian approach to motion over a Eulerian grid space bytracking quantities across a landscape as an evolving front. …
Ict Requirements For An ‘Evolutionary’ Development Of Wfd Compliant River Basin Management Plans, M. Blind
Ict Requirements For An ‘Evolutionary’ Development Of Wfd Compliant River Basin Management Plans, M. Blind
International Congress on Environmental Modelling and Software
The Water Framework Directive (WFD) poses an immense challenge to integrated water man-agement in Europe. Aiming at a “good ecological status” of all water resources in 2015, integrated river ba-sin management plans need to be in place by 2009, and need to be broadly supported by stakeholders. Cost effective programmes of measures must be put in place to meet the objective of “good ecological status”. These measures reach beyond the direct water domain and touch on fields such as spatial planning, public participation and socio-economics. Much information and knowledge needs to be available to create these plans. Information and Communication …
Estimation Of Air Quality At Trier, Germany - A Case Study With Street 5., Jürgen Junk, Alfred Helbig
Estimation Of Air Quality At Trier, Germany - A Case Study With Street 5., Jürgen Junk, Alfred Helbig
International Congress on Environmental Modelling and Software
In the course of the European Council Directive on permissible air pollutant limit values, validstarting from 2005 there is an urgent call for action, particularly for fine dust (PM10). Current investigations(Junk and Helbig 2003, Reuter and building Mueller 2003) show that the limit values in certain places incongested areas are exceeded. Only if it is possible to located these Hot Spots purposeful measures to reducethe ambient air pollution can be conducted. For an efficient identification of these Hot Spots complexcomputer models or establishing special measurements networks are to expensive. Using the statistical modelSTREET 5,0 (KTT 2003) a cost-effective screening of …
Benthic Macroinvertebrates Modelling Using Artificial Neural Networks (Ann): Case Study Of A Subtropical Brazilian River, D. Pereiraa
International Congress on Environmental Modelling and Software
Back-propagation Artificial Neural Networks (ANN) were tested with the aim of modelling the occurrence of benthic macroinvertebrate families in a south Brazilian river. The dataset, consisting of 67 sets of observations of macroinvertebrate abundance (families Hydrobiidae, Tubificidae, Chironomidae, Baetidae and Leptophlebiidae) and water quality variables (pH, temperature, dissolved oxygen, biochemical oxygen demand, nitrate, phosphate, total solids, turbidity and fecal coliforms), was collected at eleven sampling sites in the Sinos River Basin during 1991-1993. Five different ANN architectures, with one hidden layer and 2, 5, 10, 20 and 25 neurons were tested. The ANN models were trained using the gradient descendent …
Numerical Modeling Of Friction Stir Welding: A Comparison Of Alegra And Forge3, Alma H. Oliphant
Numerical Modeling Of Friction Stir Welding: A Comparison Of Alegra And Forge3, Alma H. Oliphant
Theses and Dissertations
The objective of this research was to evaluate the capabilities of ALEGRA, a Sandia National Labs hydrocode, and Forge3, a Transvalor S.A. product, to accurately model the Friction Stir Welding Process. ALEGRA and Forge3 are discussed in light of the inherent challenges of modeling Friction Stir Welding, and a rotational boundary condition is added to ALEGRA. Results are presented from Friction Stir Welding modeling outputs from both ALEGRA and Forge3. ALEGRA is shown to be incapable of modeling the Friction Stir Welding process, in large part due to its focus on shock propagation, which causes extremely small time steps. Forge3 …
Vsp Traveltime Inversion: Near-Surface Issues, Geoff J. M. Moret, William P. Clement, Michael D. Knoll, Warren Barrash
Vsp Traveltime Inversion: Near-Surface Issues, Geoff J. M. Moret, William P. Clement, Michael D. Knoll, Warren Barrash
Geosciences Faculty Publications and Presentations
P-wave velocity information obtained from vertical seismic profiles (VSPs) can be useful in imaging subsurface structure, either by directly detecting changes in the subsurface or as an aid to the interpretation of seismic reflection data. In the shallow subsurface, P-wave velocity can change by nearly an order of magnitude over a short distance, so curved rays are needed to accurately model VSP traveltimes. We used a curved-ray inversion to estimate the velocity profile and the discrepancy principle to estimate the data noise level and to choose the optimum regularization parameter. The curved-ray routine performed better than a straight-ray inversion for …
Flux Profile Modelling Using Numerical Methods, Bharat Reddy Pemmireddy
Flux Profile Modelling Using Numerical Methods, Bharat Reddy Pemmireddy
UNLV Retrospective Theses & Dissertations
Molecular beam Epitaxy (MBE) is a physical vapor deposition system, used to grow semiconductor layers (epilayers). In order to increase the economics of MBE, the industry has increased the size and number of wafers processed in one stage. This lead to, non-uniformity in thickness of material grown. In this work a process simulation tool based on numerical methods was developed to study different parameters which affect the thickness. The process of emission in open cells was identified as free evaporation and for computer simulation of these types of cells Model I was developed. The process of emission in closed cells …
Testing Density-Dependent Groundwater Models: Two-Dimensional Steady State Unstable Convection In Infinite, Finite And Inclined Porous Layers, Douglas Weatherill, Craig T. Simmons, Clifford I. Voss, Neville I. Robinson
Testing Density-Dependent Groundwater Models: Two-Dimensional Steady State Unstable Convection In Infinite, Finite And Inclined Porous Layers, Douglas Weatherill, Craig T. Simmons, Clifford I. Voss, Neville I. Robinson
United States Geological Survey: Staff Publications
This study proposes the use of several problems of unstable steady state convection with variable fluid density in a porous layer of infinite horizontal extent as two-dimensional (2-D) test cases for density-dependent groundwater flow and solute transport simulators. Unlike existing density-dependent model benchmarks, these problems have well-defined stability criteria that are determined analytically. These analytical stability indicators can be compared with numerical model results to test the ability of a code to accurately simulate buoyancy driven flow and diffusion. The basic analytical solution is for a horizontally infinite fluid-filled porous layer in which fluid density decreases with depth. The proposed …
Groundwater Investigation Buntine-Marchagee Natural Diversity Recovery Catchment, Russell John Speed, M Strelein
Groundwater Investigation Buntine-Marchagee Natural Diversity Recovery Catchment, Russell John Speed, M Strelein
Resource management technical reports
A groundwater investigation was initiated in the Buntine-Marchagee Natural Diversity Recovery Catchment 200 kms north-east of Perth, Western Australia in 2002. The investigation aimed to install a regional groundwater monitoring network and characterise the regolith throughout the catchment. Drill site selection was based on establishing a series of transects to enable construction of hydrogeological cross-sections to enhance conceptual understanding of the catchment.
Modelling Trust Relationships In Distributed Environments, Weiliang Zhao, Vijay Varadharajan, George Bryan
Modelling Trust Relationships In Distributed Environments, Weiliang Zhao, Vijay Varadharajan, George Bryan
Faculty of Engineering - Papers (Archive)
Trust management and trustworthy computing are becoming increasingly significant at present. Over the recent years there have been several research works that have addressed the issue of trust management in distributed systems. However a clear and comprehensive definition that can be used to capture a range of commonly understood notions of trust is still lacking. In this paper, we give a formal definition of trust relationship with a strict mathematical structure that can not only reflect many of the commonly used extreme notions of trust but also provides a taxonomy framework where a range of useful trust relationships can be …
Geometric Modelling Of The Temporal Bone For Cochlea Implant Simulation, Catherine Todd, Fazel Naghdy, S. J. O'Leary
Geometric Modelling Of The Temporal Bone For Cochlea Implant Simulation, Catherine Todd, Fazel Naghdy, S. J. O'Leary
Faculty of Engineering - Papers (Archive)
The first stage in the development of a clinically valid surgical simulator for training otologic surgeons in performing cochlea implantation is presented. For this purpose, a geometric model of the temporal bone has been derived from a cadaver specimen using the biomedical image processing software package Analyze (AnalyzeDirect, Inc) and its three-dimensional reconstruction is examined. Simulator construction begins with registration and processing of a Computer Tomography (CT) medical image sequence. Important anatomical structures of the middle and inner ear are identified and segmented from each scan in a semi-automated threshold-based approach. Linear interpolation between image slices produces a three-dimensional volume …