808 resultados para top-down effects


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Shifts in global climate resonate in plankton dynamics, biogeochemical cycles, and marine food webs. We studied these linkages in the North Atlantic subpolar gyre (NASG), which hosts extensive phytoplankton blooms. We show that phytoplankton abundance increased since the 1960s in parallel to a deepening of the mixed layer and a strengthening of winds and heat losses from the ocean, as driven by the low frequency of the North Atlantic Oscillation (NAO). In parallel to these bottom-up processes, the top-down control of phytoplankton by copepods decreased over the same time period in the western NASG, following sea surface temperature changes typical of the Atlantic Multi-decadal Oscillation (AMO). While previous studies have hypothesized that climate-driven warming would facilitate seasonal stratification of surface waters and long-term phytoplankton increase in subpolar regions, here we show that deeper mixed layers in the NASG can be warmer and host a higher phytoplankton biomass. These results emphasize that different modes of climate variability regulate bottom-up (NAO control) and top-down (AMO control) forcing on phytoplankton at decadal timescales. As a consequence, different relationships between phytoplankton, zooplankton, and their physical environment appear subject to the disparate temporal scale of the observations (seasonal, interannual, or decadal). The prediction of phytoplankton response to climate change should be built upon what is learnt from observations at the longest timescales.

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Shifts in global climate resonate in plankton dynamics, biogeochemical cycles, and marine food webs. We studied these linkages in the North Atlantic subpolar gyre (NASG), which hosts extensive phytoplankton blooms. We show that phytoplankton abundance increased since the 1960s in parallel to a deepening of the mixed layer and a strengthening of winds and heat losses from the ocean, as driven by the low frequency of the North Atlantic Oscillation (NAO). In parallel to these bottom-up processes, the top-down control of phytoplankton by copepods decreased over the same time period in the western NASG, following sea surface temperature changes typical of the Atlantic Multi-decadal Oscillation (AMO). While previous studies have hypothesized that climate-driven warming would facilitate seasonal stratification of surface waters and long-term phytoplankton increase in subpolar regions, here we show that deeper mixed layers in the NASG can be warmer and host a higher phytoplankton biomass. These results emphasize that different modes of climate variability regulate bottom-up (NAO control) and top-down (AMO control) forcing on phytoplankton at decadal timescales. As a consequence, different relationships between phytoplankton, zooplankton, and their physical environment appear subject to the disparate temporal scale of the observations (seasonal, interannual, or decadal). The prediction of phytoplankton response to climate change should be built upon what is learnt from observations at the longest timescales.

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El artículo analiza la figura del prosumidor desde los estudios visuales a partir de la combinación de la teoría de los actos de habla y los nuevos medios. El objetivo es evaluar si la distinción entre productores y consumidores, estrategias y tácticas de Michel de Certeau continúa siendo operativa en las interfaces gráficas de la cultura global de la información de Scott Lash. Para ello distingue dos tipos de performatividad de los actos de habla: la performatividad top-down del software, y la bottom-up de los juegos del lenguaje y las formas de vida. Estos tipos se aplican al análisis del discurso de los eslóganes que aparecen en los sitios web de las iniciativas “open” y de economía colaborativa, ya que las primeras están dedicadas a la producción de bienes inmateriales y las segundas a la producción de bienes materiales. El desarrollo muestra cómo los dos tipos de performatividad transforman el análisis textual de los estudios literarios y cinematográficos en una metodología capaz de investigar acciones materiales, humanas y no humanas. Las conclusiones describen el surgimiento de nuevas convenciones narrativas de poder y control ajenas a la ficción que apuntan a una “DIY society”.

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Objective
Pedestrian detection under video surveillance systems has always been a hot topic in computer vision research. These systems are widely used in train stations, airports, large commercial plazas, and other public places. However, pedestrian detection remains difficult because of complex backgrounds. Given its development in recent years, the visual attention mechanism has attracted increasing attention in object detection and tracking research, and previous studies have achieved substantial progress and breakthroughs. We propose a novel pedestrian detection method based on the semantic features under the visual attention mechanism.
Method
The proposed semantic feature-based visual attention model is a spatial-temporal model that consists of two parts: the static visual attention model and the motion visual attention model. The static visual attention model in the spatial domain is constructed by combining bottom-up with top-down attention guidance. Based on the characteristics of pedestrians, the bottom-up visual attention model of Itti is improved by intensifying the orientation vectors of elementary visual features to make the visual saliency map suitable for pedestrian detection. In terms of pedestrian attributes, skin color is selected as a semantic feature for pedestrian detection. The regional and Gaussian models are adopted to construct the skin color model. Skin feature-based visual attention guidance is then proposed to complete the top-down process. The bottom-up and top-down visual attentions are linearly combined using the proper weights obtained from experiments to construct the static visual attention model in the spatial domain. The spatial-temporal visual attention model is then constructed via the motion features in the temporal domain. Based on the static visual attention model in the spatial domain, the frame difference method is combined with optical flowing to detect motion vectors. Filtering is applied to process the field of motion vectors. The saliency of motion vectors can be evaluated via motion entropy to make the selected motion feature more suitable for the spatial-temporal visual attention model.
Result
Standard datasets and practical videos are selected for the experiments. The experiments are performed on a MATLAB R2012a platform. The experimental results show that our spatial-temporal visual attention model demonstrates favorable robustness under various scenes, including indoor train station surveillance videos and outdoor scenes with swaying leaves. Our proposed model outperforms the visual attention model of Itti, the graph-based visual saliency model, the phase spectrum of quaternion Fourier transform model, and the motion channel model of Liu in terms of pedestrian detection. The proposed model achieves a 93% accuracy rate on the test video.
Conclusion
This paper proposes a novel pedestrian method based on the visual attention mechanism. A spatial-temporal visual attention model that uses low-level and semantic features is proposed to calculate the saliency map. Based on this model, the pedestrian targets can be detected through focus of attention shifts. The experimental results verify the effectiveness of the proposed attention model for detecting pedestrians.

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SILVA, Alexandre Reche e. Rudimentos de uma inspeção topográfica aplicados à Passacaglia para orquestra, opus 1, de Anton Webern. Ictus - Periódico do PPGMUS/UFBA, Salvador, v. 7, p.189-208, 2010

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A escola portuguesa do século XXI tem sido alvo de reformas sucessivas procedentes de imposições económicas, políticas e sociais, sem o devido acompanhamento de inovação bottom up. A mudança decorrente tem-se processado sobretudo formalmente (inovação top down), menosprezando, ainda em larga escala, as pessoas e o seu capital (intelectual, emocional, social e psicológico), num momento em que a globalização impulsiona a transição do paradigma funcional para o paradigma das competências. Sendo os indivíduos parte integrante das soluções e êxitos organizacionais, bem como cada vez mais manifesta a preocupação dos líderes com a eficácia, eficiência e qualidade do serviço prestado ao nível das escolas de interesse público, direcionamos a análise para a gestão dos recursos humanos, mais particularmente ao nível da dualidade: instabilidade na carreira docente/estabilidade do diretor de turma. O interesse supremo da temática reside nas potencialidades deste cargo de gestão intermédia na concretização da missão da escola, a partir do papel que o seu detentor assume na teia de relações em que se insere por imposição das suas funções, e que pode fomentar quando dotado de determinadas características. Este estudo de caso, de natureza essencialmente quantitativa, traduz a análise crítica acerca do impacto da continuidade do desempenho do cargo ao longo do 2.º ciclo do ensino básico no sucesso educativo dos alunos, partindo da análise dos resultados de medidas adotadas no ano escolar 2010/2011. Para o efeito recorreu-se à análise do aproveitamento, da atuação do conselho de turma e da comunicação escola-família em seis turmas do sexto ano de escolaridade, três com o mesmo diretor de turma, de uma escola pública do concelho de Câmara de Lobos. Concluímos que a manutenção do diretor de turma nas turmas visadas teve repercussões na vertente relacional, principalmente, não tendo sido confirmada a conexão entre a continuidade do profissional que assume o cargo ao longo do ciclo e os resultados académicos dos discentes, pese embora a opinião contrária de 87,9% dos docentes inquiridos, e de a maioria quer dos estudantes, quer dos seus encarregados de educação, ser favorável à sua prossecução.

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Con la crescita in complessità delle infrastrutture IT e la pervasività degli scenari di Internet of Things (IoT) emerge il bisogno di nuovi modelli computazionali basati su entità autonome capaci di portare a termine obiettivi di alto livello interagendo tra loro grazie al supporto di infrastrutture come il Fog Computing, per la vicinanza alle sorgenti dei dati, e del Cloud Computing per offrire servizi analitici complessi di back-end in grado di fornire risultati per milioni di utenti. Questi nuovi scenarii portano a ripensare il modo in cui il software viene progettato e sviluppato in una prospettiva agile. Le attività dei team di sviluppatori (Dev) dovrebbero essere strettamente legate alle attività dei team che supportano il Cloud (Ops) secondo nuove metodologie oggi note come DevOps. Tuttavia, data la mancanza di astrazioni adeguata a livello di linguaggio di programmazione, gli sviluppatori IoT sono spesso indotti a seguire approcci di sviluppo bottom-up che spesso risulta non adeguato ad affrontare la compessità delle applicazione del settore e l'eterogeneità dei compomenti software che le formano. Poichè le applicazioni monolitiche del passato appaiono difficilmente scalabili e gestibili in un ambiente Cloud con molteplici utenti, molti ritengono necessaria l'adozione di un nuovo stile architetturale, in cui un'applicazione dovrebbe essere vista come una composizione di micro-servizi, ciascuno dedicato a uno specifica funzionalità applicativa e ciascuno sotto la responsabilità di un piccolo team di sviluppatori, dall'analisi del problema al deployment e al management. Poichè al momento non si è ancora giunti a una definizione univoca e condivisa dei microservices e di altri concetti che emergono da IoT e dal Cloud, nè tantomento alla definzione di linguaggi sepcializzati per questo settore, la definzione di metamodelli custom associati alla produzione automatica del software di raccordo con le infrastrutture potrebbe aiutare un team di sviluppo ad elevare il livello di astrazione, incapsulando in una software factory aziendale i dettagli implementativi. Grazie a sistemi di produzione del sofware basati sul Model Driven Software Development (MDSD), l'approccio top-down attualmente carente può essere recuperato, permettendo di focalizzare l'attenzione sulla business logic delle applicazioni. Nella tesi viene mostrato un esempio di questo possibile approccio, partendo dall'idea che un'applicazione IoT sia in primo luogo un sistema software distribuito in cui l'interazione tra componenti attivi (modellati come attori) gioca un ruolo fondamentale.

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Thesis (Ph.D.)--University of Washington, 2016-08

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This study provides the first spatially detailed and complete inventory of Ambrosia pollen sources in Italy – the third largest centre of ragweed in Europe. The inventory relies on a well tested top-down approach that combines local knowledge, detailed land cover, pollen observations and a digital elevation model that assumes permanent ragweed populations mainly grow below 745m. The pollen data were obtained from 92 volumetric pollen traps located throughout Italy during 2004-2013. Land cover is derived from Corine Land cover information with 100m resolution. The digital elevation model is based on the NASA shuttle radar mission with 90m resolution. The inventory is produced using a combination of ArcGIS and Python for automation and validated using cross-correlation and has a final resolution of 5km x 5km. The method includes a harmonization of the inventory with other European inventories for the Pannonian Plain, France and Austria in order to provide a coherent picture of all major ragweed sources. The results show that the mean annual pollen index varies from 0 in South Italy to 6779 in the Po Valley. The results also show that very large pollen indexes are observed in the Milan region, but this region has smaller amounts of ragweed habitats compared to other parts of the Po Valley and known ragweed areas in France and the Pannonian Plain. A significant decrease in Ambrosia pollen concentrations was recorded in 2013 by pollen monitoring stations located in the Po Valley, particularly in the Northwest of Milan. This was the same year as the appearance of the Ophraella communa leaf beetle in Northern Italy. These results suggest that ragweed habitats near to the Milan region have very high densities of Ambrosia plants compared to other known ragweed habitats in Europe. The Milan region therefore appears to contain habitats with the largest ragweed infestation in Europe, but a smaller amount of habitats is a likely cause the pollen index to be lower compared to central parts of the Pannonian Plain. A low number of densely packed habitats may have increased the impact of the Ophraella beetle and might account for the documented decrease in airborne Ambrosia pollen levels, an event that cannot be explained by meteorology alone. Further investigations that model atmospheric pollen before and after the appearance of the beetle in this part of Northern Italy are needed to assess the influence of the beetle on airborne Ambrosia pollen concentrations. Future work will focus on short distance transport episodes for stations located in the Po Valley, and long distance transport events for stations in Central Italy that exhibit peaks in daily airborne Ambrosia pollen levels.

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There is increasing advocacy for inclusive community-based approaches to environmental management, and growing evidence that involving communities improves the sustainability of social-ecological systems. Most community-based approaches rely on partnerships and knowledge exchange between communities, civil society organizations, and professionals such as practitioners and/or scientists. However, few models have actively integrated more horizontal knowledge exchange from community to community. We reflect on the transferability of community owned solutions between indigenous communities by exploring challenges and achievements of community peer-to-peer knowledge exchange as a way of empowering communities to face up to local environmental and social challenges. Using participatory visual methods, indigenous communities of the North Rupununi (Guyana) identified and documented their community owned solutions through films and photostories. Indigenous researchers from this community then shared their solutions with six other communities that faced similar challenges within Guyana, Suriname, Venezuela, Colombia, French Guiana, and Brazil. They were supported by in-country civil society organizations and academics. We analyzed the impact of the knowledge exchange through interviews, field reports, and observations. Our results show that indigenous community members were significantly more receptive to solutions emerging from, and communicated by, other indigenous peoples, and that this approach was a significant motivating force for galvanizing communities to make changes in their community. We identified a range of enabling factors, such as building capacity for a shared conceptual and technical understanding, that strengthens the exchange between communities and contributes to a lasting impact. With national and international policy-makers mobilizing significant financial resources for biodiversity conservation and climate change mitigation, we argue that the promotion of community owned solutions through community peer-to-peer exchange may deliver more long-lasting, socially and ecologically integrated, and investment-effective strategies compared to top-down, expert led, and/or foreign-led initiatives.

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Portland cement concrete (PCC) pavement undergoes repeated environmental load-related deflection resulting from temperature and moisture variations across the pavement depth. This phenomenon, referred to as PCC pavement curling and warping, has been known and studied since the mid-1920s. Slab curvature can be further magnified under repeated traffic loads and may ultimately lead to fatigue failures, including top-down and bottom-up transverse, longitudinal, and corner cracking. It is therefore important to measure the “true” degree of curling and warping in PCC pavements, not only for quality control (QC) and quality assurance (QA) purposes, but also to achieve a better understanding of its relationship to long-term pavement performance. In order to better understand the curling and warping behavior of PCC pavements in Iowa and provide recommendations to mitigate curling and warping deflections, field investigations were performed at six existing sites during the late fall of 2015. These sites included PCC pavements with various ages, slab shapes, mix design aspects, and environmental conditions during construction. A stationary light detection and ranging (LiDAR) device was used to scan the slab surfaces. The degree of curling and warping along the longitudinal, transverse, and diagonal directions was calculated for the selected slabs based on the point clouds acquired using LiDAR. The results and findings are correlated to variations in pavement performance, mix design, pavement design, and construction details at each site. Recommendations regarding how to minimize curling and warping are provided based on a literature review and this field study. Some examples of using point cloud data to build three-dimensional (3D) models of the overall curvature of the slab shape are presented to show the feasibility of using this 3D analysis method for curling and warping analysis.

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Tackling societal and environmental challenges requires new approaches that connect top-down global oversight with bottom-up subnational knowledge. We present a novel framework for participatory development of spatially explicit scenarios at national scale that model socioeconomic and environmental dynamics by reconciling local stakeholder perspectives and national spatial data. We illustrate results generated by this approach and evaluate its potential to contribute to a greater understanding of the relationship between development pathways and sustainability. Using the lens of land use and land cover changes, and engaging 240 stakeholders representing subnational (seven forest management zones) and the national level, we applied the framework to assess alternative development strategies in the Tanzania mainland to the year 2025, under either a business as usual or a green development scenario. In the business as usual scenario, no productivity gain is expected, cultivated land expands by ~ 2% per year (up to 88,808 km²), with large impacts on woodlands and wetlands. Despite legal protection, encroachment of natural forest occurs along reserve borders. Additional wood demand leads to degradation, i.e., loss of tree cover and biomass, up to 80,426 km² of wooded land. The alternative green economy scenario envisages decreasing degradation and deforestation with increasing productivity (+10%) and implementation of payment for ecosystem service schemes. In this scenario, cropland expands by 44,132 km² and the additional degradation is limited to 35,778 km². This scenario development framework captures perspectives and knowledge across a diverse range of stakeholders and regions. Although further effort is required to extend its applicability, improve users’ equity, and reduce costs the resulting spatial outputs can be used to inform national level planning and policy implementation associated with sustainable development, especially the REDD+ climate mitigation strategy.

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In 2013 the European Commission launched its new green infrastructure strategy to make another attempt to stop and possibly reverse the loss of biodiversity until 2020, by connecting habitats in the wider landscape. This means that conservation would go beyond current practices to include landscapes that are dominated by conventional agriculture, where biodiversity conservation plays a minor role at best. The green infrastructure strategy aims at bottom-up rather than top-down implementation, and suggests including local and regional stakeholders. Therefore, it is important to know which stakeholders influence land-use decisions concerning green infrastructure at the local and regional level. The research presented in this paper served to select stakeholders in preparation for a participatory scenario development process to analyze consequences of different implementation options of the European green infrastructure strategy. We used a mix of qualitative and quantitative social network analysis (SNA) methods to combine actors’ attributes, especially concerning their perceived influence, with structural and relational measures. Further, our analysis provides information on institutional backgrounds and governance settings for green infrastructure and agricultural policy. The investigation started with key informant interviews at the regional level in administrative units responsible for relevant policies and procedures such as regional planners, representatives of federal ministries, and continued at the local level with farmers and other members of the community. The analysis revealed the importance of information flows and regulations but also of social pressure, considerably influencing biodiversity governance with respect to green infrastructure and biodiversity.

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One of the most important theories in the study of environmental governance and policy is the pathology of command and control, which describes the negative consequences of top-down, technocratic governance of social and ecological systems. However, to date, this theory has been expressed somewhat inconsistently and informally in the literature, even by the seminal works that have established its importance and popularized it. This presents a problem for the sustainability science community if it cannot be sure of the precise details of one of its most important theories. Without such precision, applications and tests of various elements of the theory cannot be conducted reliably to advance the knowledge of environmental governance. I address this problem by synthesizing several seminal works to formalize this theory. The formalization involves the identification of the individual elements of the theory and a diagrammatic description of their relationships with each other that unfold in a series of semi-independent causal paths. Ideally, with such a formalization, scholars can use this theory more reliably and more meaningfully in their future work. I conclude by discussing the implications this theory has for the governance of natural resources.

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Reindeer herding is an emblematic livelihood for Northern Finland, culturally important for local people and valuable in tourism marketing. We examine the livelihood resilience of Finnish reindeer herding by narrowing the focus of general resilience on social-ecological systems (SESs) to a specific livelihood while also acknowledging wider contexts in which reindeer herding is embedded. The questions for specified resilience can be combined with the applied DPSIR approach (Drivers; Pressures: resilience to what; State: resilience of what; Impacts: resilience for whom; Responses: resilience by whom and how). This paper is based on a synthesis of the authors’ extensive anthropological fieldwork on reindeer herding and other land uses in Northern Finland. Our objective is to synthesize various opportunities and challenges that underpin the resilience of reindeer herding as a viable livelihood. The DPSIR approach, applied here as a three step procedure, helps focus the analysis on different components of SES and their dynamic interactions. First, various land use-related DPSIR factors and their relations (synergies and trade-offs) to reindeer herding are mapped. Second, detailed DPSIR factors underpinning the resilience of reindeer herding are identified. Third, examples of interrelations between DPSIR factors are explored, revealing the key dynamics between Pressures, State, Impacts, and Responses related to the livelihood resilience of reindeer herding. In the Discussion section, we recommend that future applications of the DPSIR approach in examining livelihood resilience should (1) address cumulative pressures, (2) consider the state dimension as more tuned toward the social side of SES, (3) assess both the negative and positive impacts of environmental change on the examined livelihood by a combination of science led top-down and participatory bottom-up approaches, and (4) examine and propose governance solutions as well as local adaptations by reindeer herders as equally relevant responses to enhance livelihood resilience.