101,138 research outputs found

    Statistical modeling, parameter estimation and measurement planning for PV degradation

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    Photovoltaics (PV) degradation is a key consideration during PV performance evaluation. Accurately predicting power delivery over the course of lifetime of PV is vital to manufacturers and system owners. With many systems exceeding 20 years of operation worldwide, degradation rates have been reported abundantly in the recent years. PV degradation is a complex function of a variety of factors, including but not limited to climate, manufacturer, technology and installation skill. As a result, it is difficult to determine degradation rate by analytical modeling; it has to be measured. As one set of degradation measurements based on a single sample cannot represent the population nor be used to estimate the true degradation of a particular PV technology, repeated measures through multiple samples are essential. In this chapter, linear mixed effects model (LMM) is introduced to analyze longitudinal degradation data. The framework herein introduced aims to address three issues: 1) how to model the difference in degradation observed in PV modules/systems of a same technology that are installed at a shared location; 2) how to estimate the degradation rate and quantiles based on the data; and 3) how to effectively and efficiently plan degradation measurements

    Setting an integrated soil monitoring system for Malta : strategy, feasibility and recommendations

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    Chapter 6Since 2010, MEPA has embarked on a project (which attracted co-funded ERDF assistance) (1) to develop a multi-thematic environment strategy that would lead to updating of its data/ information monitoring capabilities for a number of environmental sectors. The monitoring and continuous evaluation of soil properties is one important sector within this project. Essentially, a multi-criterion assessment of existing available information has been carried out with a view to objectively chart the most appropriate process to carry out a pilot field sampling by testing a pre-agreed set of indicators. The latter were established after taking into consideration all degradation pressures threatening the continued sustainability of this resource. Multi-criterion analysis was carried out by means of a limited set of soil-related datasets published in past editions of Malta’s State of the Environment Report in order to support a number of objectives stipulated within the Project’s ambitious Terms of Reference. Information was derived from earlier attempts to establish a soil information system for Malta. All soil degradation threats, officially determined by the European Commission’s Technical Working Groups, have been taken into consideration within the aforementioned project and its research methodology with a view of establishing a shared GIS environment in accordance with state-of-the-art information dissemination standards.peer-reviewe

    The role of economics in ecosystem based management:The case of the EU Marine Strategy Framework Directive; first lessons learnt and way forward

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    The EU Marine Strategy Framework Directive (MSFD) sets out a plan of action relating to marine environmental policy and in particular to achieving ‘good environmental status’ (GES) in European marine waters by 2020. Article 8.1 (c) of the Directive calls for ‘an economic and social analysis of the use of those waters and of the cost of degradation of the marine environment’. The MSFD is ‘informed’ by the Ecosystem Approach to management, with GES interpreted in terms of ecosystem functioning and services provision. Implementation of the Ecosystem Approach is expected to be by adaptive management policy and practice. The initial socio-economic assessment was made by maritime EU Member States between 2011 and 2012, with future updates to be made on a regular basis. For the majority of Member States, this assessment has led to an exercise combining an analysis of maritime activities both at national and coastal zone scales, and an analysis of the non-market value of marine waters. In this paper we examine the approaches taken in more detail, outline the main challenges facing the Member States in assessing the economic value of achieving GES as outlined in the Directive and make recommendations for the theoretically sound and practically useful completion of the required follow-up economic assessments specified in the MSFD

    Cognitive fluctuations in connection to disgraphia a comparison of Alzheimer's disease with dementia Lewy bodies

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    Background: The purpose of the present study was to examine the relationship between cognitive impairment and the performance of handwritten scripts presented as “letter-writing” to a close relative by patients with dementia Lewy bodies (DLB), as fluctuations of the symptoms phase, and in a matched group of patients with Alzheimer’s disease (AD). The degree of writing disability and personal, spatial, and temporal orientation was compared in these two groups. Design and methods: Fourteen simple questions, designed in a form that could be utilized by any general practitioner in order to document the level of cognitive functioning of each patient, were presented to 30 AD patients and 26 DLB patients. The initial cognition test was designated PQ1. The patients were examined on tests of letter-writing ability. Directly after the letter-writing, the list of 14 questions presented in PQ1 was presented again in a repeated procedure that was designated PQ2. The difference between these two measures (PQ1 – PQ2) was designated D∆. This test of letter-writing ability and cognitive performance was administered over 19 days. Results: Several markedly strong relationships between dysgraphia and several measures of cognitive performance in AD patients and DLB patients were observed, but the deterioration of performance from PQ1 to PQ2 over all test days were markedly significant in AD patients and not significant in DLB patients. It is possible that in graphic expression even by patients diagnosed with moderate to relatively severe AD and DLB there remains some residual capacity for understanding and intention that may be expressed. Furthermore, the deterioration in performance and the differences noted in AD and DLB patients may be due to the different speed at which the process of the protein degradation occurs for functional modification of synapses. Conclusion: Our method can be used as part of neuropsychological tests to differentiate the diagnosis between AD and DL

    Driver-pressure-impact and response-recovery chains in European rivers: observed and predicted effects on BQEs

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    The report presented in the following is part of the outcome of WISER’s river Workpackage WP5.1 and as such part of the module on aquatic ecosystem management and restoration. The ultimate goal of WP5.1 is to provide guidance on best practice restoration and management to the practitioners in River Basin Management. Therefore, a series of analyses was undertaken, each of which used a part of the WP5.1 database in order to track two major pathways of biological response: 1) the response of riverine biota to environmental pressures (degradation) and 2) the response of biota to the reduction of these impacts (restoration). This report attempts to provide empirical evidence on the environment-biota relationships for both pathways

    Climate warming, marine protected areas and the ocean-scale integrity of coral reef ecosystems

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    Coral reefs have emerged as one of the ecosystems most vulnerable to climate variation and change. While the contribution of a warming climate to the loss of live coral cover has been well documented across large spatial and temporal scales, the associated effects on fish have not. Here, we respond to recent and repeated calls to assess the importance of local management in conserving coral reefs in the context of global climate change. Such information is important, as coral reef fish assemblages are the most species dense vertebrate communities on earth, contributing critical ecosystem functions and providing crucial ecosystem services to human societies in tropical countries. Our assessment of the impacts of the 1998 mass bleaching event on coral cover, reef structural complexity, and reef associated fishes spans 7 countries, 66 sites and 26 degrees of latitude in the Indian Ocean. Using Bayesian meta-analysis we show that changes in the size structure, diversity and trophic composition of the reef fish community have followed coral declines. Although the ocean scale integrity of these coral reef ecosystems has been lost, it is positive to see the effects are spatially variable at multiple scales, with impacts and vulnerability affected by geography but not management regime. Existing no-take marine protected areas still support high biomass of fish, however they had no positive affect on the ecosystem response to large-scale disturbance. This suggests a need for future conservation and management efforts to identify and protect regional refugia, which should be integrated into existing management frameworks and combined with policies to improve system-wide resilience to climate variation and change

    Economics of soil and water conservation

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    The Ethiopian highlands, inhabited by the vast majority of the Ethiopian human and livestock populations, are under continuous threat from soil erosion. Land degradation induced by soil erosion is considered to be among the major factors responsible for the recurrent malnutrition and famine problems in Ethiopia. Conservation efforts during recent decades have succeeded neither in triggering voluntary adoption of conservation practices nor in mitigating soil erosion problems. The purpose of this thesis is, therefore, to understand the socio-economic aspects underlying soil and water conservation decisions in the context of subsistence farmers in the Eastern Highlands of Ethiopia. In articles I, III, and IV, the farmers’ decision problem is modeled as a utility maximization problem, and econometric models are used to link the statistical model of observed data and the economic model. Stochastic dominance criteria are used, in article I, to determine whether adoption of a conservation practice results in higher expected grain yield and income and/or reduced variability. Limited dependent variable econometric models are used in articles III and IV in order to determine factors that influence farmers’ decisions on soil and water conservation, and their preference for types of development intervention. In article II, the decision problem is modeled as an intertemporal net benefit maximization problem, and a dynamic programming optimization model is applied to determine the optimal path of investment in soil and water conservation. Findings in article I suggest that conservation results in higher expected grain yield and income, but does not support the hypothesis that conservation unambiguously results in less variability than no-conservation. In article II, it is shown that the optimal path of investment in soil and water conservation depends on the discount rate and grain prices. The results also suggest that erosive agricultural practices yield higher return in the short-term, whereas conservation yields a higher and sustainable return in the long-term. The need to design incentive mechanisms that encourage farmers to have a longer planning horizon are among important suggestions proposed in articles I and II. Results, in article III, suggest that specific physical conditions of plots and socioeconomic characteristics of farm households influence the soil and water conservation decision behavior of farmers. Article IV suggests that the perceived priority of farmers with regard to agricultural problems and socio-economic characteristics, determines their preference for the type of development intervention. The results also suggest that there exists a complementarity between different interventions and hence a need to address them simultaneously to ensure a higher return from interventions. An important lesson to be drawn from articles III and IV is that differences in farming conditions and complementarities between policy programs need to be noted in any intervention program
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