928 resultados para two-term control


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Triggered by recent flood catastrophes and increasing concerns about climate change, scientists as well as policy makers increasingly call for making long-term water policies to enable a transformation towards flood resilience. A key question is how to make these long-term policies adaptive so that they are able to deal with uncertainties and changing circumstances. The paper proposes three conditions for making long-term water policies adaptive, which are then used to evaluate a new Dutch water policy approach called ‘Adaptive Delta Management’. Analysing this national policy approach and its translation to the Rotterdam region reveals that Dutch policymakers are torn between adaptability and the urge to control. Reflecting on this dilemma, the paper suggests a stronger focus on monitoring and learning to strengthen the adaptability of long-term water policies. Moreover, increasing the adaptive capacity of society also requires a stronger engagement with local stakeholders including citizens and businesses.

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At a global scale, aquatic ecosystems are being altered by human activities at a greater rate than at any other time in history. In recent years, grassroots efforts have generated interest in the restoration of degraded or destroyed aquatic habitats, especially small wetlands and streams where such projects are feasible with local resources. We present ecological management lessons learned from 17 years of monitoring the fish community response to the channel relocation and reach-level restoration of Juday Creek, a 3rd-order tributary of the St. Joseph River in Indiana, USA. The project was designed to increase habitat complexity, reverse the effects of accumulated fine sediment (< 2 mm diameter), and mitigate for the impacts of a new golf course development. The 1997 restoration consisted of new channel construction within two reaches of a 1.2-km section of Juday Creek that also contained two control reaches. A primary social goal of the golf course development and stream restoration was to avoid harm to the non-native brown trout fishery, as symbolic of community concerns for the watershed. Our long-term monitoring effort revealed that, although fine sediment increased over time in the restored reaches, habitat conditions have promoted the resurgence of native fish species. Since restoration, the fish assemblage has shifted from non-native Salmonidae (brown trout, rainbow trout) to native Centrarchidae (rock bass, largemouth bass, smallmouth bass). In addition, native, nongame species have remained stable or have increased in population abundance (e.g., Johnny darter, mottled sculpin). The results of this study demonstrate the value of learning from a restoration project to adjust management decisions that enhance environmental quality.

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

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The Mediterranean Sea constitutes a unique environment to study cold-seep ecosystems due to the presence of different geodynamic settings, from an active margin along the Mediterranean Ridge (MR) to a passive margin in the Nile Deep-Sea Fan (NDSF). We attempted to identify the structure of benthic communities associated with the Napoli and Amsterdam mud volcanoes (MVs) located on the MR and to establish the links between faunal distribution and environmental conditions at different spatial scales. Comparison between the 2 MVs revealed that the faunal distribution seemed to be mainly controlled by the characteristics of the microhabitats. On both geological structures, the variability between the different microhabitats was higher than the variability observed between replicates of the same microhabitat, and the distribution of macro-fauna was apparently linked to gradients in physico-chemical conditions. The peripheral sites from Napoli were generally more oxygenated and harboured lower species richness than the active sites. The reduced sediment microhabitat from Amsterdam presented the highest methane concentrations and was mainly colonised by symbiont-bearing vesicomyid bivalves and heterotrophic dorvilleid polychaetes. Overall, a higher taxonomic diversity was observed on Napoli. Sub-stratum type was hypothesised to be the second factor influencing faunal distribution. The results of this study highlight the high heterogeneity of faunal communities associated with seep ecosystems within this region and the need to pursue investigations at various spatial and temporal scales.

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Human standing posture is inherently unstable. The postural control system (PCS), which maintains standing posture, is composed of the sensory, musculoskeletal, and central nervous systems. Together these systems integrate sensory afferents and generate appropriate motor efferents to adjust posture. The PCS maintains the body center of mass (COM) with respect to the base of support while constantly resisting destabilizing forces from internal and external perturbations. To assess the human PCS, postural sway during quiet standing or in response to external perturbation have frequently been examined descriptively. Minimal work has been done to understand and quantify the robustness of the PCS to perturbations. Further, there have been some previous attempts to assess the dynamical systems aspects of the PCS or time evolutionary properties of postural sway. However those techniques can only provide summary information about the PCS characteristics; they cannot provide specific information about or recreate the actual sway behavior. This dissertation consists of two parts: part I, the development of two novel methods to assess the human PCS and, part II, the application of these methods. In study 1, a systematic method for analyzing the human PCS during perturbed stance was developed. A mild impulsive perturbation that subjects can easily experience in their daily lives was used. A measure of robustness of the PCS, 1/MaxSens that was based on the inverse of the sensitivity of the system, was introduced. 1/MaxSens successfully quantified the reduced robustness to external perturbations due to age-related degradation of the PCS. In study 2, a stochastic model was used to better understand the human PCS in terms of dynamical systems aspect. This methodology also has the advantage over previous methods in that the sway behavior is captured in a model that can be used to recreate the random oscillatory properties of the PCS. The invariant density which describes the long-term stationary behavior of the center of pressure (COP) was computed from a Markov chain model that was applied to postural sway data during quiet stance. In order to validate the Invariant Density Analysis (IDA), we applied the technique to COP data from different age groups. We found that older adults swayed farther from the centroid and in more stochastic and random manner than young adults. In part II, the tools developed in part I were applied to both occupational and clinical situations. In study 3, 1/MaxSens and IDA were applied to a population of firefighters to investigate the effects of air bottle configuration (weight and size) and vision on the postural stability of firefighters. We found that both air bottle weight and loss of vision, but not size of air bottle, significantly decreased balance performance and increased fall risk. In study 4, IDA was applied to data collected on 444 community-dwelling elderly adults from the MOBILIZE Boston Study. Four out of five IDA parameters were able to successfully differentiate recurrent fallers from non-fallers, while only five out of 30 more common descriptive and stochastic COP measures could distinguish the two groups. Fall history and the IDA parameter of entropy were found to be significant risk factors for falls. This research proposed a new measure for the PCS robustness (1/MaxSens) and a new technique for quantifying the dynamical systems aspect of the PCS (IDA). These new PCS analysis techniques provide easy and effective ways to assess the PCS in occupational and clinical environments.

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Background: Obesity and asthma are an important public health problem in Saudi Arabia. An increasing body of data supports the hypothesis that obesity is a risk factor for asthma. Asthma appears to be associated with low bone mineral density (BMD) due to long-term use of corticosteroids. Studies recently showed that weight bearing exercise training can increase mineral bone density, reduce weight and improve metabolic control. Objective: The present study aimed to measure the effects of treadmill walking exercises on bone mineral status and inflammatory cytokines in obese asthmatic patients treated with long term intake of corticosteroids. Methods: Eighty obese asthmatic patients of both sexes, their age ranged from 41 to 53 years. Subjects were divided into two equal groups: training group (group A) received aerobic exercise training on treadmill for six months in addition to the medical treatment where, the control group (group B) received only the medical treatment. Results: The results of this study indicated a significant increase in BMD of the lumbar spine & the radius, serum calcium and high density lipoprotein cholesterol (HDL-c) & significant reduction in parathyroid hormone, leptin, tumor necrosis factor– alpha(TNF-α), interleukin-2 (IL-2), interleukin-4 (IL-4), interleukin-6 (IL-6), low density lipoprotein cholesterol (LDL-c), triglycerides (TG) and body mass index (BMI) in group (A), while these changes were not significant in group (B).Also; there was a significant difference between both groups at the end of the study. Conclusion: Treadmill walking exercise training is an effective treatment policy to improve bone mineral status and modulates inflammatory cytokines and blood lipids profile in obese asthmatic patients with long term intake of corticosteroids.

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Recommendation for Oxygen Measurements from Argo Floats: Implementation of In-Air-Measurement Routine to Assure Highest Long-term Accuracy As Argo has entered its second decade and chemical/biological sensor technology is improving constantly, the marine biogeochemistry community is starting to embrace the successful Argo float program. An augmentation of the global float observatory, however, has to follow rather stringent constraints regarding sensor characteristics as well as data processing and quality control routines. Owing to the fairly advanced state of oxygen sensor technology and the high scientific value of oceanic oxygen measurements (Gruber et al., 2010), an expansion of the Argo core mission to routine oxygen measurements is perhaps the most mature and promising candidate (Freeland et al., 2010). In this context, SCOR Working Group 142 “Quality Control Procedures for Oxygen and Other Biogeochemical Sensors on Floats and Gliders” (www.scor-int.org/SCOR_WGs_WG142.htm) set out in 2014 to assess the current status of biogeochemical sensor technology with particular emphasis on float-readiness, develop pre- and post-deployment quality control metrics and procedures for oxygen sensors, and to disseminate procedures widely to ensure rapid adoption in the community.

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Wild boar is a recognized reservoir of bovine tuberculosis (TB) in the Mediterranean ecosystems, but information is scarce outside of hotspots in southern Spain. We describe the first high-prevalence focus of TB in a non-managed wild boar population in northern Spain and the result of eight years of TB management. Measures implemented for disease control included the control of the local wild boar population through culling and stamping out of a sympatric infected cattle herd. Post-mortem inspection for detection of tuberculosis-like lesions as well as cultures from selected head and cervical lymph nodes was done in 745 wild boar, 355 Iberian ibexes and five cattle between 2004 and 2012. The seasonal prevalence of TB reached 70% amongst adult wild boar and ten different spoligotypes and 13 MIRU-VNTR profiles were detected, although more than half of the isolates were included in the same clonal complex. Only 11% of infected boars had generalized lesions. None of the ibexes were affected, supporting their irrelevance in the epidemiology of TB. An infected cattle herd grazed the zone where 168 of the 197 infected boars were harvested. Cattle removal and wild boar culling together contributed to a decrease in TB prevalence. The need for holistic, sustained over time, intensive and adapted TB control strategies taking into account the multi-host nature of the disease is highlighted. The potential risk for tuberculosis emergence in wildlife scenarios where the risk is assumed to be low should be addressed.

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A complainant alleged the Department of Revenue violated the South Carolina Procurement Code. This paper examines that complaint.

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Fish communities of the Ria Formosa coastal lagoon (south Portugal) were sampled on a monthly basis with a beach seine at 4 sites, during two different time periods: 1980-1986 and 2001-2002. Community indices, species ranking and multivariate analysis were used in order to identify changes in the fish community between the two time periods. A total of 153,511 fish representing 57 taxa were recorded. Although species composition was very similar for both sampling periods, multivariate analysis performed on annual species abundance in number and weight revealed differences in fish community structure between the two periods. Structural changes in fish community were related mostly to a sharp decrease in the abundance of Mugilidae from 1980-1986 to 2001-2002. These changes were probably associated to a decrease in organic matter contents and nutrients concentrations due to improvements in sewage treatment and better water circulation inside the lagoon. The changes in fish community structure are more evident in the inner areas of the lagoon than near the inlet. The association between changes in sewage patterns and changes in the ichthyofaunal community structure reinforces the importance of fish communities as a biological indicator of human induced changes in marine systems. (c) 2007 Elsevier Ltd. All rights reserved.

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The idea of spacecraft formations, flying in tight configurations with maximum baselines of a few hundred meters in low-Earth orbits, has generated widespread interest over the last several years. Nevertheless, controlling the movement of spacecraft in formation poses difficulties, such as in-orbit high-computing demand and collision avoidance capabilities, which escalate as the number of units in the formation is increased and complicated nonlinear effects are imposed to the dynamics, together with uncertainty which may arise from the lack of knowledge of system parameters. These requirements have led to the need of reliable linear and nonlinear controllers in terms of relative and absolute dynamics. The objective of this thesis is, therefore, to introduce new control methods to allow spacecraft in formation, with circular/elliptical reference orbits, to efficiently execute safe autonomous manoeuvres. These controllers distinguish from the bulk of literature in that they merge guidance laws never applied before to spacecraft formation flying and collision avoidance capacities into a single control strategy. For this purpose, three control schemes are presented: linear optimal regulation, linear optimal estimation and adaptive nonlinear control. In general terms, the proposed control approaches command the dynamical performance of one or several followers with respect to a leader to asymptotically track a time-varying nominal trajectory (TVNT), while the threat of collision between the followers is reduced by repelling accelerations obtained from the collision avoidance scheme during the periods of closest proximity. Linear optimal regulation is achieved through a Riccati-based tracking controller. Within this control strategy, the controller provides guidance and tracking toward a desired TVNT, optimizing fuel consumption by Riccati procedure using a non-infinite cost function defined in terms of the desired TVNT, while repelling accelerations generated from the CAS will ensure evasive actions between the elements of the formation. The relative dynamics model, suitable for circular and eccentric low-Earth reference orbits, is based on the Tschauner and Hempel equations, and includes a control input and a nonlinear term corresponding to the CAS repelling accelerations. Linear optimal estimation is built on the forward-in-time separation principle. This controller encompasses two stages: regulation and estimation. The first stage requires the design of a full state feedback controller using the state vector reconstructed by means of the estimator. The second stage requires the design of an additional dynamical system, the estimator, to obtain the states which cannot be measured in order to approximately reconstruct the full state vector. Then, the separation principle states that an observer built for a known input can also be used to estimate the state of the system and to generate the control input. This allows the design of the observer and the feedback independently, by exploiting the advantages of linear quadratic regulator theory, in order to estimate the states of a dynamical system with model and sensor uncertainty. The relative dynamics is described with the linear system used in the previous controller, with a control input and nonlinearities entering via the repelling accelerations from the CAS during collision avoidance events. Moreover, sensor uncertainty is added to the control process by considering carrier-phase differential GPS (CDGPS) velocity measurement error. An adaptive control law capable of delivering superior closed-loop performance when compared to the certainty-equivalence (CE) adaptive controllers is finally presented. A novel noncertainty-equivalence controller based on the Immersion and Invariance paradigm for close-manoeuvring spacecraft formation flying in both circular and elliptical low-Earth reference orbits is introduced. The proposed control scheme achieves stabilization by immersing the plant dynamics into a target dynamical system (or manifold) that captures the desired dynamical behaviour. They key feature of this methodology is the addition of a new term to the classical certainty-equivalence control approach that, in conjunction with the parameter update law, is designed to achieve adaptive stabilization. This parameter has the ultimate task of shaping the manifold into which the adaptive system is immersed. The performance of the controller is proven stable via a Lyapunov-based analysis and Barbalat’s lemma. In order to evaluate the design of the controllers, test cases based on the physical and orbital features of the Prototype Research Instruments and Space Mission Technology Advancement (PRISMA) are implemented, extending the number of elements in the formation into scenarios with reconfigurations and on-orbit position switching in elliptical low-Earth reference orbits. An extensive analysis and comparison of the performance of the controllers in terms of total Δv and fuel consumption, with and without the effects of the CAS, is presented. These results show that the three proposed controllers allow the followers to asymptotically track the desired nominal trajectory and, additionally, those simulations including CAS show an effective decrease of collision risk during the performance of the manoeuvre.

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This study evaluates the effects of betaine supplementation (1 g kg−1 for 20 weeks) on the regulation of genes involved in lipid and cholesterol metabolism of Longissimus lumborum and Biceps femoris from obese Alentejano pigs. Betaine supplementation led to an increase in total cholesterol in both muscles, complementing results previously published indicating a significant increase on the intramuscular lipid content. The expression of twelve genes involved in lipogenesis, lipolysis/FA oxidation, FA transport, and cholesterol metabolism, as well as two transcription factors were also evaluated. Genes related to lipid and cholesterol synthesis plus FA transport were consistently up-regulated in both muscles of betaine fed pigs. On the other hand, genes related to lipolysis/FA oxidation were not affected or down-regulated by betaine supplementation. Our data suggest that the underlying mechanism regulating IMF and cholesterol accumulation in Alentejano pigs supplemented with betaine is associated with the up-regulation of genes involved in lipid synthesis, FA transport, and cholesterol synthesis.

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The apple is attacked by a significant number of insect pests in Brazilian commercial orchards, including Bonagota salubricola and Grapholita molesta (Lepidoptera: Tortricidae). Sexual disruption of B. salubricola and G. molesta was evaluated in apple orchard using the flowable pheromone formulations, SPLAT Grafo+Bona (SG+B), SPLAT Attract and Kill Grafo+Bona (SAKG+B), and compared with the standard insecticides used for management in the Integrated Apple Production (IAP) system. Both formulations were applied at a rate of 1kg/ha on October 10, 2005 and December 13, 2005 using 300 and 1000 point sources/ha of SG+B and SAKG+B, respectively in experimental units of 7 ha. Adult male captures of B. salubricola and G. molesta were evaluated weekly in Delta traps with specific synthetic sex pheromone from October 10, 2005 to February 14, 2006. Damage to fruits was evaluated on November 21 and December 21, 2005, and January 25 and February 14, 2006. In the SPLAT treated experimental units a significant reduction was observed in the number of B. salubricola and G. molesta males caught in Delta traps compared to the experimental unit IAP. Damage by B. salubricola at harvest ranged from 1.63 to 4.75% with no differences between treatments, while damage by G. molesta was near zero in all experimental units. Mating disruption using SG+B and SAKG+B was sufficient to control B. salubricola and G. molesta with results equivalent to IAP guidelines. This technology is promising for management of both pests in Brazilian apple orchards with immediate reduction of 43% in the number of insecticide applications.

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Three anaerobic ponds used to store and treat piggery wastes were fully covered with permeable materials manufactured from polypropylene geofabric, polyethylene shade cloth and supported straw. The covers were assessed in terms of efficacy in reducing odour emission rates over a 40-month period. Odour samples were collected from the surface of the covers, the surface of the exposed liquor and from the surface of an uncovered (control) pond at one of the piggeries. Relative to the emission rate of the exposed liquor at each pond, the polypropylene, shade cloth and straw covers reduced average emission rates by 76%, 69% and 66% respectively. At the piggery with an uncovered control pond, the polypropylene covers reduced average odour emission rates by 50% and 41% respectively. A plausible hypothesis, consistent with likely mechanisms for the odour reduction and the olfactometric method used to quantifying the efficacy of the covers, is offered.