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Registros recuperados: 147
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A comparison between three different approaches to omplement a system dynamic model: an assessment by a multidisciplinary team. Infoteca-e
FREUA, M. C.; BARIONI, L. G.; VILAMIU, R. G. d'A.; DIAS, F. R. T..
In the last few decades, application of system dynamics models (SDM) has disseminated through the agricultural sciences. Modeling groups are now much more multidisciplinary once the models currently developed are applied to larger frameworks. The literature has been inconclusive with regard to empirical evidence of the trade-offs between different paradigms to implement SDMs. In order to gain insight on the advantages and disadvantages between the paradigms we simulated a working group environment with seven researchers coming from various educational backgrounds where they had to implement a process-based SDM and fill in a questionnaire scoring characteristics of the paradigms and implementation process. The participants were divided into three groups...
Tipo: Boletim de Pesquisa e Desenvolvimento (INFOTECA-E) Palavras-chave: Modelos agrícolas; Modelo dinâmico; Programação orientada a objetos; Agricultural models; Objected-oriented programming.; Modelo Matemático.; Mathematical models; Dynamic models..
Ano: 2014 URL: http://www.infoteca.cnptia.embrapa.br/infoteca/handle/doc/1008307
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A dynamic model of oligopoly in the coffee export market AgEcon
Karp, Larry S.; Perloff, Jeffrey M..
A linear-quadratic, dynamic feedback oligopoly model that nests various market structures is used to estimate the degree of competitiveness and the adjustment paths of the two largest coffee exporters, Brazil and Colombia. Their estimated behavior is relatively competitive. This subgame perfect dynamic model is-compared to a standard static oligopoly model and the open-loop model (the dynamic generalization of the standard static model). Both classical and Bayesian tests of open-loop and feedback dynamic models are reported.
Tipo: Working or Discussion Paper Palavras-chave: Export marketing; Mathematical models; International Relations/Trade; Crop Production/Industries.
Ano: 1990 URL: http://purl.umn.edu/47250
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A modern view of Joseph's policy: food stocks as financial assets AgEcon
Adelman, Irma; Berck, Peter.
Tipo: Working or Discussion Paper Palavras-chave: Food consumption; Mathematical models; Price stabilization; Prices; Risk; Supply and demand.
Ano: 1989 URL: http://purl.umn.edu/43666
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A re-evaluation of marine nematode productivity OMA
Vranken, G.; Herman, P.M.J.; Vincx, M.; Heip, C.H.R..
Nematodes are the most abundant multicellular animals in marine sediments but their role in the benthos has not been properly quantified yet. In nearly all energy-flow budgets of marine systems their annual production P is given as about nine times their biomass B and their part in the total energy-flow is consequently estimated as anywhere between 3 and 30% of the total (carbon) input in the benthic system. Our laboratory experiments demonstrate that nematode productivity is much higher than P/B ~ 9 per year and may reach values of over 60 for bacterial grazers. To obtain more reliable estimates for field populations we propose a regression equation relating egg-to-egg development time T<sub>min</sub> to temperature (t) and adult female weight...
Tipo: Info:eu-repo/semantics/article Palavras-chave: Biological production; Mathematical models; Meiobenthos; Nematoda [Nematodes].
Ano: 1986 URL: http://www.vliz.be/nl/open-marien-archief?module=ref&refid=3576
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A standard computable general equilibrium (CGE) model in GAMS AgEcon
Lofgren, Hans; Harris, Rebecca Lee; Robinson, Sherman.
Over the past decade, the increasing power and reliability of microcomputers and the development of sophisticated software designed specifically for use with them has led to significant changes in the way quantitative food policy analysis is conducted. These changes cover most aspects of the analysis, ranging from the collections and analysis of socioeconomic data to the conduct of model-based policy simulations. The venue of the computations has shifted from off-site mainframes dependent on highly trained operators and significant capital investment in supporting equipment, to desktop and laptop computers dependent only on the occasional availability of electricity. This means that it is now feasible to quickly transfer new techniques between IFPRI and...
Tipo: Book Palavras-chave: Agriculture; Economic aspects; Mathematical models; Food supply; Mathematical models; Equilibrium (Economics); Mathematical models; Research Methods/ Statistical Methods.
Ano: 2002 URL: http://purl.umn.edu/42483
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A system for management and analysis of rice genomics data for candidate gene discovery International Rice Research Institute
Mansueto, Locedie A..
xx, 165 l. : ill. Thesis (M.S.) -- University of the Philippines Diliman
Tipo: Thesis Palavras-chave: Rice; Plant genetics; Information systems; Data analysis; Genomics; Mathematical models; Information management.
Ano: 2005 URL: http://hdl.handle.net/123456789/363
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Ability of non-linear mixed models to predict growth in laying hens R. Bras. Zootec.
Galeano-Vasco,Luis Fernando; Cerón-Muñoz,Mario Fernando; Narváez-Solarte,William.
In this study, the Von Bertalanffy, Richards, Gompertz, Brody, and Logistics non-linear mixed regression models were compared for their ability to estimate the growth curve in commercial laying hens. Data were obtained from 100 Lohmann LSL layers. The animals were identified and then weighed weekly from day 20 after hatch until they were 553 days of age. All the nonlinear models used were transformed into mixed models by the inclusion of random parameters. Accuracy of the models was determined by the Akaike and Bayesian information criteria (AIC and BIC, respectively), and the correlation values. According to AIC, BIC, and correlation values, the best fit for modeling the growth curve of the birds was obtained with Gompertz, followed by Richards, and then...
Tipo: Info:eu-repo/semantics/article Palavras-chave: Chickens; Mathematical models; Poultry; Regression analysis; Weight gain.
Ano: 2014 URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1516-35982014001100573
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ACT Now or Later: The Economics of Malaria Resistance AgEcon
Laxminarayan, Ramanan.
In the past, malaria control efforts in sub-Saharan Africa have relied on a combination of vector control and effective treatment using chloroquine. With increasing resistance to chloroquine, attention has now turned to alternative treatment strategies to replace this failing drug. Although there are strong theoretical arguments in favor of switching to more expensive artemisinin-based combination treatments (ACTs), the validity of these arguments in the face of financial constraints has not been previously analyzed. In this paper, we use a Bioeconomic model of malaria transmission and evolution of drug resistance to examine questions of optimal treatment strategy and coverage when drug resistance places an additional constraint on choices available to the...
Tipo: Working or Discussion Paper Palavras-chave: Malaria; Mathematical models; Drug resistance; Bioeconomics; Health Economics and Policy; I10; I19; C61.
Ano: 2003 URL: http://purl.umn.edu/10699
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Ajustement de modèles mathématiques de la croissance d'algues phytoplanctoniques en culture ArchiMer
Le Berre, Jerome.
Introduction: This document is the End of Second Year internship report for Rennes University 1's Senior Math and Computer Science Modelisation Professional diploma. This two month internship was completed at the Brest IFREMER center at the Coastal Ecology department. IFREMER participates, in the course of its institutional missions, in observation and coastal sea surveillance, in order to improve on the knowledge, protection methods and restoration of the marine environment. Marine phytoplankton proliferation is an important study subject because of its potential cause for nuisance, for men, consumers of sea products as well as for the ecosystem. During Spring and Summer, shellfish become invariably unsuitable for consumption due to toxins produced by...
Tipo: Text Palavras-chave: Aquaculture; Growth; Phytoplanctonic algae; Mathematical models.
Ano: 2000 URL: http://archimer.ifremer.fr/doc/2000/rapport-1770.pdf
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Alarmas en un servicio que proporciona información oportuna e interpretable a sus clientes Colegio de Postgraduados
Velázquez Castro, Gilberto David.
Para complementar los servicios de información a empresas o personas físicas, en cuanto a comunicar, no sólo cambios en sus variables de interés, sino el impacto que éstos tienen sobre las actividades de la empresa, se propone un servicio que calcula tales impactos con el uso de modelos matemáticos. Se puede generar una alarma al cliente, cuando los cambios satisfagan criterios que éste define para tal efecto. De acuerdo a la urgencia indicada, se comunicará al cliente por correo electrónico, mensaje de texto o una llamada de un empleado del servicio, alguna situación que pudiera requerir una decisión oportuna.______A service to customers was conceived in order to offer information about the impact of changes in their data, rather than just report...
Tipo: Tesis Palavras-chave: Comunicación oportuna; Interpretable; Modelos matemáticos; Alarmas; Datos del entorno empresarial; Maestría; Computo Aplicado; Timely communicaction; Interpretable; Mathematical models; Alarms; Business environment data.
Ano: 2009 URL: http://hdl.handle.net/10521/1505
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Analise de desempenho da irrigacao. Infoteca-e
SILVA, E. M. da; AZEVEDO, J. A. de; LIMA, J. E. F. W..
bitstream/CPAC-2009/24826/1/doc_70.pdf
Tipo: Documentos (INFOTECA-E) Palavras-chave: Avaliacao; Evaluation; Losses.; Água; Análise Quantitativa; Desperdício; Irrigação por Pivô Central; Irrigação por Aspersão; Irrigação; Modelo Matemático; Performance.; Irrigation; Mathematical models; Quantitative analysis; Sprinkler irrigation; Water..
Ano: 2002 URL: http://www.infoteca.cnptia.embrapa.br/infoteca/handle/doc/559635
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Análisis de la utilización de la captura por unidad de esfuerzo de pescadilla de red (Cynoscion guatucupa) como índice de abundancia anual. Período 1992-2004 OceanDocs
Perrotta, R.G.; Ruarte, C.O..
The stripped weakfish (Cynoscion guatucupa) caught in Brazil, Uruguay and Argentina (SW Atlantic) has a wide latitudinal distribution (22° S-43° S). In Argentina there are two main fishing areas, the Argentine-Uruguayan Common Fishing Zone and 'El Rincón', southern zone of the Buenos Aires littoral. The importance of the species makes it necessary to define an annual abundance index that would allow to diagnose the state of the stock. The model adjusted to calculate the index is the General Linear Model. The factors used were Year, Quarter, Length, Stratum (4 categories) and sub-areas (5 categories), all statistically significant. The problem generated by the presence in the model of first order interactions that include the Year factor is discussed. The...
Tipo: Journal Contribution Palavras-chave: Catch/effort; Mathematical models; Coastal fisheries; Marine environment; Marine environment; Mathematical models; Coastal fisheries; Http://aims.fao.org/aos/agrovoc/c_4610; Http://aims.fao.org/aos/agrovoc/c_24199; Http://aims.fao.org/aos/agrovoc/c_1696.
Ano: 2009 URL: http://hdl.handle.net/1834/3461
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Aplicación del método de máxima verosimilitud a la estimación de parámetros y comparación de curvas de crecimiento de von Bertalanffy. OceanDocs
Aubone, A.; Wöhler, O.C..
With the purpose of easening its application, the theory of parameter estimation by the maximum likelihood method is presented. The theory is general and useful for linear and nonlinear models. The method is applied to the von Bertalanffy´s growth model for individual data and for mean values of length-at-age. Statistical tests to compare parameters from different population groups are presented. Problems caused by lack of verification of assumptions are discussed. An example of its application is given and results of nonlinear least squares estimations are compared to those obtained with Allen´s method. An example of application implemented on a calculus spreadsheet is attached.
Tipo: Journal Contribution Palavras-chave: Growth curves; Mathematical models; Mathematical models; Http://aims.fao.org/aos/agrovoc/c_24199.
Ano: 2000 URL: http://hdl.handle.net/1834/2541
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Application of Geographic Information System in rice suitability assessment International Rice Research Institute
Magnaye, Amable Jose Pelito.
77 l. : ill. Thesis (M.S.) -- University of the Philippines at Los Baños
Tipo: Thesis Palavras-chave: Rice; Soil; Soil survey; Soil suitability; Mathematical models; Soil classification; Computer software; Geographic Information systems.
Ano: 1991 URL: http://hdl.handle.net/123456789/942
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Application of mathematical models for the prediction of adsorption isotherms in solid mixture for mango powder refreshment Ciênc. Tecnol. Aliment.
Clemente,Edmar; Afonso,Marcos Rodrigues Amorim; Souza,Ana Paula; Correia,José Maria; Pires,Raquel Gomes; Maia,Geraldo Arraes.
Solid mixtures for refreshment are already totally integrated to the Brazilian consumers' daily routine, because of their quick preparation method, yield and reasonable price - quite lower if compared to 'ready-to-drink' products or products for prompt consumption, what makes them economically more accessible to low-income populations. Within such a context, the aim of this work was to evaluate the physicochemical and mineral composition, as well as the hygroscopic behavior of four different brands of solid mixture for mango refreshment. The BET, GAB, Oswim and Henderson mathematical models were built through the adjustment of experimental data to the isotherms of adsorption. Results from the physiochemical evaluation showed that the solid mixtures for...
Tipo: Info:eu-repo/semantics/article Palavras-chave: Adsorption; Isotherms; Mathematical models; Nutritious powders; Refreshment; Mango.
Ano: 2011 URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0101-20612011000300010
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Approche experimentale du comportement d'une plaque composite sous effet d'un choc perforant ArchiMer
Paris, P; Genin, D; Hamelin, P.
Our purpose in this paper is to study the behaviour of composite materials reinforced by glass satin weave 8 fabric under the impact of a projectile. The first part of this paper deals with experimental tests carried out using a servo-hydraulic machine. The hydraulic ram can be programmed to impact the specimen at any desired velocity between a few tenths of a millimetre per minute and 20 m/s. In the second part, these experimental results are compared with the numerical results of bidimensional finite difference code AUTODYN. This program allows the numerical simulation of the penetration of composite plates by projectiles.
Tipo: Text Palavras-chave: Ship technology; Collisions; Materials testing; Simulation; Mathematical models; Numerical analysis; Composite materials; Essai de choc; Réponse dynamique; Simulation numérique; Plaque composite; Impact.
Ano: 1992 URL: http://archimer.ifremer.fr/doc/1992/acte-1045.pdf
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Biomass and carbon stock from Pinus caribaea var. hondurensis under homogenous stands in southwest Bahia, Brazil Ciência Rural
Lima,Máida Cynthia Duca de; Barreto-Garcia,Patrícia Anjos Bittencourt; Sanquetta,Carlos Roberto; Novaes,Adalberto Brito de; Melo,Lara Clímaco de.
ABSTRACT: There is a large number of studies evaluating methods to quantify biomass for the genus Pinus in different regions of Brazil. However, knowledge about this subject in the Northeast region of Brazil is still incipient. The objective of the present study was to assess the biomass and carbon stocks and select mathematical models to estimate these variables in Pinus caribaea var. hondurensis , which is established in homogenous stands in the Southwest region of the state of Bahia (Brazil). The biomass was quantified using the destructive method. Samples of needles, bole, bark, and branches were analyzed to determine their carbon contents. Ten models were tested, and the best of them were chosen based on the following statistical indicators: adjusted...
Tipo: Info:eu-repo/semantics/article Palavras-chave: Exotic forest species; Mathematical models; Biomass.
Ano: 2016 URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-84782016000600957
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Carbon Accumulation in Pinus taeda Estimated by X-rays Densitometry and Trunk Analysis PFB - Pesquisa Florestal Brasileira
Bellote, Antonio Francisco Jurado; Dedecek, Renato Antonio; Lavoranti, Osmir José; Tomazello Filho, Mario de Castro; Andrade, Guilherme de Castro.
The objective of this work was to evaluate Pinus aeda growth and based on X-ray methods of  densitometry and bole analyses to develop mathematical models to estimate carbon amount accumulated on trees of different ages varying on DBH. Five P. taeda plantations were selected on sites of different soils, thinning intensity and growing rate. On each site dominant trees were selected and discs cuts from different heights were collected and submitted to X-ray densitometry for trunk analyses. Mathematical models were developed, to generated equations to compare by testing their statistical identity and equality and to validate by bootstrap methods. The results showed that P. taeda productivity was influenced by soil and silvicultural practices; X-ray...
Tipo: Info:eu-repo/semantics/article Palavras-chave: Productivity; Mathematical models; Carbon sequestration; Thinning; Forestry sites. Produtividade; Modelos matemáticos; Seqüestro de carbono; Desbaste; Sítios florestais..
Ano: 2011 URL: http://pfb.cnpf.embrapa.br/pfb/index.php/pfb/article/view/208
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Challenges, project strategy and major accomplishments International Rice Research Institute
Rotter, R.P.; Hoanh, C.T.; Aggarwal, P.K.; Keulen, H. van.
In: Synthesis of methodology development and case studies, ed. by R. P. Roetter, et al., p. 3-10, ill. (Sysnet Res. Pap. Ser.; No.3 (2000)
Tipo: Article Palavras-chave: Land use; Mathematical models; Soil; Asia; LUPAS.
Ano: 2000 URL: http://hdl.handle.net/10269/13
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Changing consumption patterns and demand for cereal grains in Asia International Rice Research Institute
Huang, Jikun.
182 l. : ill. Thesis (Ph.D.) -- University of the Philippines at Los Baños
Tipo: Thesis Palavras-chave: Rice; Small grains; Food consumption; Demand; Economic analysis; Mathematical models; Asia.
Ano: 1990 URL: http://hdl.handle.net/123456789/1032
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