893 resultados para systems of signs
Resumo:
In 1999, the Chesapeake Bay Program completed a survey of existing data on chemical contaminants and the potential for bioeffects in 38 tidal river systems of Chesapeake Bay. This review led to the identification of 20 areas for which there were insufficient data to adequately characterize the potential for contaminant bioeffects on the Bay’s living resources. The goal of the present study was to estimate the current status of ecological condition in five of these areas and thus help to complete the overall toxics inventory for the Bay. These five systems included the Chester River, Nanticoke River, Pocomoke River, Lower Mobjack Bay (Poquosin and Back Rivers) and the South and Rhode Rivers. This study utilized a Sediment Quality Triad (SQT) approach in combination with additional water-column contaminant analysis to allow for a “weight of evidence” assessment of environmental condition. A total of 60 stations distributed among the five systems, using a probabilistic stratified random design, were sampled during the summer of 2004 to allow for synoptic measures of sediment contamination, sediment toxicity, and benthic condition. Upon completion of all analyses, stations were assigned to one of four categories based on the three legs of the triad. Stations with high sediment quality had no hits on any of the three legs of the triad; those with moderate quality had one hit; those with marginal quality had two hits; and those with poor quality had hits for all three legs of the triad. The Pocomoke River had by far the largest proportion of the total area (97.5%) classified as having high sediment quality, while the Rhode/South system had the highest proportion (11.4%) classified as poor. None of the stations in the Chester River, Nanticoke River, and Lower Mobjack Bay systems were classified as poor. More than 65% of the area of each of the five systems was classified with high to moderate sediment quality. The Rhode/South system had 30.4% of total area classified with marginally to severely poor quality. The results of this study highlight the importance of using multiple indicators and a “weight of evidence” approach to characterize environmental quality and the potential bioeffects of toxic contaminants.
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Computer Aided Control Engineering involves three parallel streams: Simulation and modelling, Control system design (off-line), and Controller implementation. In industry the bottleneck problem has always been modelling, and this remains the case - that is where control (and other) engineers put most of their technical effort. Although great advances in software tools have been made, the cost of modelling remains very high - too high for some sectors. Object-oriented modelling, enabling truly re-usable models, seems to be the key enabling technology here. Software tools to support control systems design have two aspects to them: aiding and managing the work-flow in particular projects (whether of a single engineer or of a team), and provision of numerical algorithms to support control-theoretic and systems-theoretic analysis and design. The numerical problems associated with linear systems have been largely overcome, so that most problems can be tackled routinely without difficulty - though problems remain with (some) systems of extremely large dimensions. Recent emphasis on control of hybrid and/or constrained systems is leading to the emerging importance of geometric algorithms (ellipsoidal approximation, polytope projection, etc). Constantly increasing computational power is leading to renewed interest in design by optimisation, an example of which is MPC. The explosion of embedded control systems has highlighted the importance of autocode generation, directly from modelling/simulation products to target processors. This is the 'new kid on the block', and again much of the focus of commercial tools is on this part of the control engineer's job. Here the control engineer can no longer ignore computer science (at least, for the time being). © 2006 IEEE.
Resumo:
Computer Aided Control Engineering involves three parallel streams: Simulation and modelling, Control system design (off-line), and Controller implementation. In industry the bottleneck problem has always been modelling, and this remains the case - that is where control (and other) engineers put most of their technical effort. Although great advances in software tools have been made, the cost of modelling remains very high - too high for some sectors. Object-oriented modelling, enabling truly re-usable models, seems to be the key enabling technology here. Software tools to support control systems design have two aspects to them: aiding and managing the work-flow in particular projects (whether of a single engineer or of a team), and provision of numerical algorithms to support control-theoretic and systems-theoretic analysis and design. The numerical problems associated with linear systems have been largely overcome, so that most problems can be tackled routinely without difficulty - though problems remain with (some) systems of extremely large dimensions. Recent emphasis on control of hybrid and/or constrained systems is leading to the emerging importance of geometric algorithms (ellipsoidal approximation, polytope projection, etc). Constantly increasing computational power is leading to renewed interest in design by optimisation, an example of which is MPC. The explosion of embedded control systems has highlighted the importance of autocode generation, directly from modelling/simulation products to target processors. This is the 'new kid on the block', and again much of the focus of commercial tools is on this part of the control engineer's job. Here the control engineer can no longer ignore computer science (at least, for the time being). ©2006 IEEE.
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An attempt was made to study the input-output relationships and economics of pangas monoculture and carp-pangas polyculture in Bangladesh. By analyzing the data collected from 50 pangas farms and 55 carp-pangas farms, the study has investigated the production systems of two technologies and the effects of fingerling stocking and applications of feed and fertilizer on fisheries income. The data were collected from the fishermen of Trishal and Bhaluka of Mymensingh district, and Kahaloo and Adamdighee of Bogra district during 2001-02. For pangas monoculture, the stocking density was 31,561 per ha while it was 55,017 per ha in carp-pangas polyculture. Most of the farmers used urea, TSP and lime before stocking. Rice and wheat bran happened to be the most common feed ingredients for both types of culture in general. Other important ingredients used were mustard oil-cakes, rice polish, wheat flour, fish meal, bone meal, soybean meal and poultry litter. In terms of quantities, rice bran and wheat bran dominated the farmers list. Rice and wheat bran together constituted about 60% of all studied feeds. Feed cost constituted 59.13% of total costs for pangas monoculture and 67.44% for carp-pangas polyculture. Per ha productions of pangas and carp-pangas in a single culture cycle were 15,508 kg and 19,745 kg, respectively. Per ha gross profits were estimated to be Tk 310,311 and Tk 464,418 for pangas monoculture and carp-pangas polyculture, respectively. Net profit appeared to be Tk 264,216 per ha for pangas monoculture and Tk 416,509 per ha for carp-pangas polyculture. The BCRs calculated were 1.46 and 1.68 for monoculture and polyculture, respectively. The break-even costs per kg of fish were estimated at Tk 36.93 for pangas and Tk 30.93 for mixed species which was much lower than the prices the producers received. Break-even productions were estimated at 10,702 kg per ha for pangas monoculture and 11,784 kg per ha for carp-pangas polyculture. Fingerling and feed cost, and pond size significantly explained the variation of income from pangas monoculture. These factors have significantly influenced the income from the crop. Functional analysis shows that 1% increase in the feed cost might increase 0.51% of pangas income and 0.41% in carp-pangas income. No other inputs had shown this much of responses to increasing income from a fish.
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Spined loach, Cobitis taenia, is a predominant fish in the river systems of the southern Caspian Sea basin. Although there is evidence of the geographical divergence of this taxon, but no information is available on morphological differences within the species populations. This study was designed to evaluate some biological factors including; morphometric and meristic characters, length-weight, age-growth, condition factor, diet, reproduction, variation and differentiation, in the Babolrud, Talar and Siahrud Rivers in south of the Caspian Sea basin. Age, sex ratio, fecundity, ova diameter and gonadosomatic index were estimated. Also, regression analyses was tested the relation between fecundity and fish length, weight, gonad weight, and also age. Totally 858 fish of which 721 were matures, were collected from these rivers by electrofishing. 37 morphometric characters, 9 meristic characters and 78 truss network system characters were estimated. Resulats of DFA analysis based on data of morphometric and meristic showd that these populations are highly (94.5%) varios from each other. In discriminate function analysis, the proportion of individuals correctly classified into their original groups was 61%, 65.4% and 86.5% for upstream and downstream, respectively. Clustering based on Euclidean distances among groups of centroids using an UPGMA and also principal component analysis’ results for morphometric data indicated that these populations from these three rivers were clearly distinct from each other. Regression equations between length and weight in these three populations were significantly different from Folton factor (b=3), that showed the fish has a negative Alometric growth process. Condition factor was estimated between 0.8912 to 1.2736 and 0.8131 to 1.4489 for males and females, respectively. Sex ratio (female: male) in these populations was 1.2816:1. The difference between the number of females and males was significant and females were more than males. The female and male specimens reach maturity by Tl more than 40 and 30 mm and at the age of 2+ and 1+, respectively. The mean of ova diameter was 0.5824±0.2882. The spawning took place from May to late July, at the water temperature from 18.7 to 24.0°C. The GSI values average at the beginning of the reproduction period was about 9%, with ranged from 2 to 26% in ripe mature females. The absolute and relative fecundity were 2109±792 and 579±208 respectively. The absolute fecundity was significantly related to body weight and gonads weight. Based on the pattern of gonado-somatic index, it was concluded that this fish has prolong active reproductive period, which is a type of adaptation by short-lived small fishes to environmental conditions. The macroscopic and histological results showed that the female and male have 5 and 4 stages in their maturation process, respectively. The RLG index was about 0.4732, which showed the fish is a carnivorous species. Significant difference was observed between fishes with different length and diet. The main foods of the fish were Trichoptera, Chironomidae larvae and Ephemeroptera which were their prefered food as well, however it was estimated that the food selection and diet are affected by environmental conditions.
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This study summarises the high level drivers on ecological systems of the BOBLME. The ecological characterisation resulted in the identification of 29 subsystems. The report recommends the development of fully integrated approaches that considers human needs and the ecological system, involving stakeholders in a transparent way.
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We consider the general problem of constructing nonparametric Bayesian models on infinite-dimensional random objects, such as functions, infinite graphs or infinite permutations. The problem has generated much interest in machine learning, where it is treated heuristically, but has not been studied in full generality in non-parametric Bayesian statistics, which tends to focus on models over probability distributions. Our approach applies a standard tool of stochastic process theory, the construction of stochastic processes from their finite-dimensional marginal distributions. The main contribution of the paper is a generalization of the classic Kolmogorov extension theorem to conditional probabilities. This extension allows a rigorous construction of nonparametric Bayesian models from systems of finite-dimensional, parametric Bayes equations. Using this approach, we show (i) how existence of a conjugate posterior for the nonparametric model can be guaranteed by choosing conjugate finite-dimensional models in the construction, (ii) how the mapping to the posterior parameters of the nonparametric model can be explicitly determined, and (iii) that the construction of conjugate models in essence requires the finite-dimensional models to be in the exponential family. As an application of our constructive framework, we derive a model on infinite permutations, the nonparametric Bayesian analogue of a model recently proposed for the analysis of rank data.
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In the multi-site manufacturing domain, systems-of-systems (SoS) are rarely called so. However, there exist a number of collaborative manufacturing paradigms which closely relate to system-of-system principles. These include distributed manufacturing, dispersed network manufacturing, virtual enterprises and cloud manufacturing/manufacturing-as-a-service. This paper provides an overview of these terms and paradigms, exploring their characteristics, overlaps and differences. These manufacturing paradigms are then considered in relation to five key system-of-systems characteristics: autonomy, belonging, connectivity, diversity and emergence. Data collected from two surveys of academic and industry experts is presented and discussed, with key challenges and barriers to multi-site manufacturing SoS identified.
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Dynamic centrifuge modelling has been carried out at Cambridge since the late 1970s. Over this period, three different mechanical earthquake actuators were developed. In this paper the development of a new servo-hydraulic earthquake actuator is described. The basic design principles are explained along with the need to carry out these designs to match the existing services and systems of the 35 year old Turner beam centrifuge at Cambridge. In addition, some of the features of the Turner beam centrifuge are exploited in the design of this new earthquake actuator. The paper also explains the mechanical fabrication of the actuator and the control systems that were developed in order to generate real earthquake motions. Finally, the performance of this new servo-hydraulic earthquake actuator is presented and assessed based on a wide range of earthquake input motions.
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This paper employs dissipativity theory for the global analysis of limit cycles in particular dynamical systems of possibly high dimension. Oscillators are regarded as open systems that satisfy a particular dissipation inequality. It is shown that this characterization has implications for the global stability analysis of limit cycle oscillations: i) in isolated oscillators, ii) in interconnections of oscillators, and iii) for the global synchrony analysis in interconnections of identical oscillators. © 2007 IEEE.
Resumo:
Multidisciplinary Design Optimization (MDO) is a methodology for optimizing large coupled systems. Over the years, a number of different MDO decomposition strategies, known as architectures, have been developed, and various pieces of analytical work have been done on MDO and its architectures. However, MDO lacks an overarching paradigm which would unify the field and promote cumulative research. In this paper, we propose a differential geometry framework as such a paradigm: Differential geometry comes with its own set of analysis tools and a long history of use in theoretical physics. We begin by outlining some of the mathematics behind differential geometry and then translate MDO into that framework. This initial work gives new tools and techniques for studying MDO and its architectures while producing a naturally arising measure of design coupling. The framework also suggests several new areas for exploration into and analysis of MDO systems. At this point, analogies with particle dynamics and systems of differential equations look particularly promising for both the wealth of extant background theory that they have and the potential predictive and evaluative power that they hold. © 2012 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.
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Gao-Yan Li, Xu-Zhen Wang, Ya-Hui Zhao, Jie Zhang, Chun-Guang Zhang, and Shun-Ping He (2009) Speciation and phylogeography of Opsariichthys bidens (Pisces: Cypriniformes: Cyprinidae) in China: analysis of the cytochrome b gene of mtDNA from diverse populations. Zoological Studies 48(4): 569-583. The cyprinid fish Opsariichthys bidens Gunther is distributed in all major river systems of continental East Asia, and represents an attractive model for phylogeographic studies among cyprinid species or within a given species. In this study, we investigated the phylogeographic and demographic history of this species, using partial sequences of the cytochrome (cyt) b gene in mitochondrial (mt)DNA. Fish samples were collected from almost all major river systems where O. bidens is distributed in China. Sequence analysis showed remarkably high polymorphism, with 125 haplotypes in the 234 specimens examined, and with 89.8% of haplotypes occurring in only 1 specimen. A neutrality test indicated that some groups were not at mutation-drift equilibrium, suggesting a past population expansion. These results were supported by a mismatch distribution analysis. Based on our analysis, O. bidens consists of 4 groups belonging to 2 clades. The divergence time of the 2 clades was estimated to be 11.06-8.04 my. This value corresponds to the time of the 2nd uplift of the Qinghai-Tibet Plateau, the emergence of the East Asian monsoon, and the Epoch-6 Event. A two species scheme is proposed. http://zoolstud.sinica.edu.tw/Journals/48.4/569.pdf
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Alterations in hematological indices such as decreases in blood cell counts (RBC), hematocrit (Ht) and hemoglobin (Hb) concentrations are key symptoms of anemia. However, few experiments were conducted to examine changes in hematological indices of fish exposed to microcystins that are believed to be fatal to circulatory systems of vertebrates. An acute toxicological experiment was designed to study hematological changes of crucian carp injected intraperitoneally (i.p.) with extracted microcystins at two doses, 50 and 200 mu g MC-LReqkg(-1) body weight. After being i.p. injected with microcystins, the fish exhibited behavioral abnormity. There were significant decreases in RBC in the high-dose group, and in Ht and Hb concentrations in both dose groups, while erythrocte sedimentation rate (ESR) significantly increased, indicating the appearance of normocytic anemia. There were no prominent changes in the three red cell indices, mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH,), and mean corpuscular hemoglobin concentration (MCHC). Increases in blood urea nitrogen (BUN) and creatinine (CR) in both dose groups suggest the occurrence of kidney impairment. Alteration in blood indices was reversible at the low dose group. Conclusively, anemia induced by kidney impairment was a key factor to cause abnormity of swimming behaviors and high mortality of crucian carp. (c) 2007 Elsevier Ltd. All rights reserved.
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We present the Unified Form Language (UFL), which is a domain-specific language for representing weak formulations of partial differential equations with a view to numerical approximation. Features of UFL include support for variational forms and functionals, automatic differentiation of forms and expressions, arbitrary function space hierarchies formultifield problems, general differential operators and flexible tensor algebra. With these features, UFL has been used to effortlessly express finite element methods for complex systems of partial differential equations in near-mathematical notation, resulting in compact, intuitive and readable programs. We present in this work the language and its construction. An implementation of UFL is freely available as an open-source software library. The library generates abstract syntax tree representations of variational problems, which are used by other software libraries to generate concrete low-level implementations. Some application examples are presented and libraries that support UFL are highlighted. © 2014 ACM.
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The family Sisoridae is one of the largest and most diverse Asiatic catfish families, most species occurring in the water systems of the Qinhai-Tibetan Plateau and East Himalayas. To date published morphological and molecular phylogenetics hypotheses of sisorid catfishes are part congruent, and there are some areas of significant disagreement with respect to intergeneric relationships. We used mitochondrial cytochrome b and 16S rRNA gene sequences to clarify existing gaps in phylogenetics and to test conflicting vicariant and dispersal biogeographical hypotheses of Chinese sisorids using dispersal-vicariance analysis and weighted ancestral area analysis in combination with palaeogeographical data as well as molecular clock calibration. Our results suggest that: (1) Chinese sisorid catfishes form a monophyletic group with two distinct clades, one represented by (Gagata (Bagarius, Glyptothorax)) and the other by (glyptosternoids, Pseudecheneis); (2) the glyptosternoid is a monophyletic group and Glyptosternum, Glaridoglanis, and Exostoma are three basal species having a primitive position among it; (3) a hypothesis referring to Pseudecheneis as the sister group of the glyptosternoids, based on morphological evidence, is supported; (4) the genus Pareuchiloglanis, as presently defined, is not monophyletic; (5) congruent with previous hypotheses, the uplift of Qinghai-Tibetan Plateau played a primary role in the speciation and radiation of the Chinese sisorids; and (6) an evolutionary scenario combining aspects of both vicariance and dispersal theory is necessary to explain the distribution pattern of the glyptosternoids. In addition, using a cytochrome b substitution rate of 0.91% per million years and 0.23% for 16S rRNA, we tentatively date that the glyptosternoids most possibly originated in Oligocene-Miocene boundary (19-24Myr), and radiated from Miocene to Pleistocene, along with a center of origin in the Irrawaddy-Tsangpo drainages and several rapid speciation in a relatively short time. (c) 2005 Elsevier Inc. All rights reserved.