Experimental performability evaluation of middleware for large-scale distributed systems

We present a tool for experimental evaluation of distributed software that enables performability tests to be incorporated in the agile development of complex middleware systems. The proposed approach combines simulation with the profiling of key components and is achieved by an extension to a standard simulation kernel and reflection, thus leveraging existing simulation models and easing the integration of existing components. The evaluation of database replication middleware in large-scale systems is used to illustrate the approach.Fundação para a Ciência e a Tecnologia (FCT) - Project StrongRep (POSI/CHS/41285/2001)

Aspectos da aplicação do Delft Hydraulics 'SOBEK' no desenvolvimento de um sistema de gestão operacional da água em Alqueva

No âmbito do desenvolvimento de um Sistema de Suporte à Decisão (SSD) para a gestão da água no Empreendimento de Fins Múltiplos de Alqueva (EFMA) foi seleccionado, após uma avaliação de diferentes alternativas de software de modelação hidrodinâmica e de qualidade da água, o programa SOBEK (WL, 2005) para a modelação de problemas de qualidade da água unidimensionais. No presente trabalho apresentam-se as características mais importantes deste programa e descrevem-se os principais aspectos relacionados com a sua integração no ambiente hidroinformático em desenvolvimento para a gestão operacional das infra-estruturas, construídas e em fase de projecto, da rede primária do Subsistema de Alqueva a montante da barragem de Alvito. A construção do modelo hidrodinâmico foi precedida de um estudo pormenorizado das infraestruturas que constituem o sistema em análise, com recurso a informação constante dos seus projectos de execução. A caracterização geométrica das infra-estruturas foi desenvolvida com o detalhe correspondente ao de projecto de execução (ou levantamento no caso de infra-estruturas existentes), distinguindo-se duas situações físicas distintas: albufeiras e sistemas adutores. No casodas albufeiras consideraram-se os seguintes elementos de projecto: fundo ou topografia do terreno; planta correspondente aos níveis relevantes; cortes; características das barragens; descarga de fundo e de caudal ecológico; descarregadores intermédios; descarregadores de cheia. No caso dos canais, túneis e condutas em pressão consideraram-se os seguintes elementos de projecto: planta com traçado do eixo; perfil longitudinal; secções transversais e acessórios

Mathematical modelling of salt water intrusion in a Northern Portuguese estuary

Salinity intrusion is a key issue for estuarine water quality management. Aquatic ecosystem sustainability is highly dependent on salinity concentration dynamics and must be studied for each particular environment. Salinity intrusion into the estuary of the river Lima, in the north-western region of the Iberian Peninsula, was studied based on a two-dimensional hydrodynamic and mass transport model. Tide heights and river discharges are the major causes affecting salinity intrusion, and have been analyzed by means of estuarine circulation simulation for different scenarios. The upstream propagation of the salinity front under unfavorable conditions reaches a river section located at about 12 km upstream the river mouth. The developed model constitutes a powerful tool for evaluation of the salinity intrusion pattern in the river Lima estuary, and an auxiliary instrument for decision making in river basin water management

River water quality modelling in developing a catchment water safety plan

The primary aim of a catchment water safety plan is to reduce risks within the catchment to protect the quality of drinking water sources at the intake point. Even where effective arrangements for catchment management and control have been implemented, unexpected deterioration in raw water quality can pose a risk to treated drinking water quality. Thus potential sources of pollution impacting the area of influence of the intake should be identified and monitored. An important part of any catchment management strategy includes implementation of raw water monitoring programmes, targeted at the most likely microbiological threats to water treatment. When combined with good monitoring datasets, properly calibrated, tested and verified surface water models can be used to forecast or estimate risks under various scenarios. This allows a good insight into impacts associated with known and anticipated land use activities within the catchment. In this work a hybrid methodology based on river water quality data analysis and hydrodynamic and water quality modelling was developed to assess the surface water quality in the Portuguese river Cávado. This component constitutes the base for developing a catchment water safety plan at this river basin

Modelação matemática da produção primária em zonas costeiras

O estudo da dinâmica de produção primária apresenta um interesse especial quando realizado em zonas costeiras utilizadas de forma intensiva para a aquicultura, como é o caso da Ria de Arosa. Nesta ria, a cadeia alimentar é dominada pelas elevadas taxas de produção primária sustentadas pelo afloramento de águas oceânicas ricas em nutrientes, resultando em elevadas quantidades de fitoplâncton que, por sua vez, servem de sustento às culturas de mexilhão em bateas. Neste artigo apresenta-se um modelo da cadeia alimentar proposto para a Ria de Arosa. Procede-se à apresentação das principais variáveis de estado seleccionadas e à caracterização das cinéticas que lhes estão associadas, evidenciando-se ainda as principais potencialidades de um modelo deste tipo na avaliação e previsão de cenários de funcionamento da cadeia alimentar

Contribution to the preservation of healthy coastal ecosystems

The release of pollutants into coastal zones from municipal and/or industrial drainage systems is a problem with a considerable environmental impact. In order to minimize the contamination of coastal waters in certain places (e.g., along beaches and in aquacultures), solutions based on the construction of submarine sewer outfalls have been proposed. In order to ascertain the optimal conditions for the release of an emissary, in particular the place of release, it is necessary to characterize the hydrodynamic transport processes that govern the evolution and mixture of pollutants in the area of interest. Circulation in the coastal zone is complicated, given that it is determined by a set of forcing mechanisms of diverse origins (meteorological, astronomical, large-scale ocean circulation, etc.) that endow it with a considerable space-time variation. Wastewater plume behaviour and characteristics depend both on the receiving water conditions and on the discharge characteristics. Accordingly, the implementation of a submarine outfall system requires a prior study of the site where the outfall is to be constructed, in order to achieve optimal rates of dilution of the pollutants released to the environment. Mathematical modelling appears to be a very useful tool for coastal zone environmental management either for continuous monitoring analysis or in accidental ecosystem rupture. This work presents some results and conclusions of two case studies. The first is a study of the pollutant cloud released at the São Jacinto submarine sewer outfall, located about 3 km offshore and 3 km north of an important coastal lagoon (NW Portugal). The main focus of this study was to establish the hydrodynamic conditions in which the pollutant release might affect the coastline (principally the existing beaches and lagoon). The second case presents some hydrodynamic results and water quality aspects of the Ria de Arosa (NW Spain), and also includes an assessment of the environmental impact of wastewater discharges from nine submarine outfalls considered in the sanitation plan of this bay. Results of faecal matter concentration distribution were used in the discussion on the outfall discharges’ impact on the natural water system for different hydrodynamic scenarios. In both cases, 3D numerical models were used

Oil spills in coastal zones : environmental impacts and practical mitigating solutions

A computational structure that has been developed to forecast the time-space evolution of oil spills in marine environments is presented. This structure was developed considering widely used mathematica formulations for oil spreading and weathering processes. A Eulerian transport model, that uses hydrodynamic results obtained with a two-dimensional and a quasi three-dimensional hydrodynamic model, was used to predict the oil slick transport and spread. General characteristics of the computational structure and the results of its application to a real case study - the “Cercal” accident in October 1994 - are presented. Georeferenced data are processed via a Geographical Information System tool. Data on the N/T “Prestige” oil spill processed by means of this information system and simulation results are also included.(undefined

Hybrid Maneuver for Gradient Search with Multiple Coordinated AUVs

This work presents a hybrid maneuver for gradient search with multiple AUV's. The mission consists in following a gradient field in order to locate the source of a hydrothermal vent or underwater freshwater source. The formation gradient search exploits the environment structuring by the phenomena to be studied. The ingredients for coordination are the payload data collected by each vehicle and their knowledge of the behaviour of other vehicles and detected formation distortions

Towards the minimization of project duration and cost in stochastic project management environments

There is a general consensus that the rational use of available resources is, nowadays, an important task, since project managers are interested in the maximization of profit and the minimization of risk. In this work, it is proposed a multi-objective model to optimize the use of resources in a stochastic environment. In this multi-objective formulation the aim is to minimize the project duration and the total project cost at the same time. In the future, we intend to solve this problem using multi-objective evolutionary algorithms.Fundação para a Ciência e a Tecnologia (FCT

Performance assessment of different dam discharges schemes influencing river water quality

Hydropower energy production policies are usually defined trying to maximize the economical revenue, obeying to environmental restrictions and established downstream water uses requirements. Behind minimum daily averages of river ecological discharges, the hourly nature of the hydropower production schemes presents a pronounced effect on downstream river water quantity and quality. However, the capacity to control the river behaviour can be used to efficiently improve river water quality management practices if we can anticipate the performance of different management strategies. This paper presents a methodology to assess the performance of different turbine discharges schemes related with downstream river water quality. Three different performance indicators are presented and their computation is derived from a hydrodynamic and water quality river model implemented in Sobek. This methodology is applied to a Portuguese river: the river Cávado