Graphical tracking systems revisited: a practical approach to computer scheduling in horticulture

Graphical tracking is a technique for crop scheduling where the actual plant state is plotted against an ideal target curve which encapsulates all crop and environmental characteristics. Management decisions are made on the basis of the position of the actual crop against the ideal position. Due to the simplicity of the approach it is possible for graphical tracks to be developed on site without the requirement for controlled experimentation. Growth models and graphical tracks are discussed, and an implementation of the Richards curve for graphical tracking described. In many cases, the more intuitively desirable growth models perform sub-optimally due to problems with the specification of starting conditions, environmental factors outside the scope of the original model and the introduction of new cultivars. Accurate specification for a biological model requires detailed and usually costly study, and as such is not adaptable to a changing cultivar range and changing cultivation techniques. Fitting of a new graphical track for a new cultivar can be conducted on site and improved over subsequent seasons. Graphical tracking emphasises the current position relative to the objective, and as such does not require the time consuming or system specific input of an environmental history, although it does require detailed crop measurement. The approach is flexible and could be applied to a variety of specification metrics, with digital imaging providing a route for added value. For decision making regarding crop manipulation from the observed current state, there is a role for simple predictive modelling over the short term to indicate the short term consequences of crop manipulation.

Predicting fault inflow in iterative software development processes: an industrial evaluation

This paper addresses the need for accurate predictions on the fault inflow, i.e. the number of faults found in the consecutive project weeks, in highly iterative processes. In such processes, in contrast to waterfall-like processes, fault repair and development of new features run almost in parallel. Given accurate predictions on fault inflow, managers could dynamically re-allocate resources between these different tasks in a more adequate way. Furthermore, managers could react with process improvements when the expected fault inflow is higher than desired. This study suggests software reliability growth models (SRGMs) for predicting fault inflow. Originally developed for traditional processes, the performance of these models in highly iterative processes is investigated. Additionally, a simple linear model is developed and compared to the SRGMs. The paper provides results from applying these models on fault data from three different industrial projects. One of the key findings of this study is that some SRGMs are applicable for predicting fault inflow in highly iterative processes. Moreover, the results show that the simple linear model represents a valid alternative to the SRGMs, as it provides reasonably accurate predictions and performs better in many cases.

Participatory research approaches in the development of improved management practices in indigenous chickens production systems with smallholder farmers in Kenya

This thesis is concerned with development of improved management practices in indigenous chicken production systems in a research process that includes participatory approaches with smallholder farmers and other stakeholders in Kenya. The research process involved a wide range of activities that included on-station experiments, field surveys, stakeholder consultations in workshops, seminars and visits, and on-farm farmer participatory research to evaluate the effect of some improved management interventions on production performance of indigenous chickens. The participatory research was greatly informed from collective experiences and lessons of the previous activities. The on-station studies focused on hatching, growth and nutritional characteristics of the indigenous chickens. Four research publications from these studies are included in this thesis. Quantitative statistical analyses were applied and they involved use of growth models estimated with non-linear regressions for the growth characteristics, chi-square determinations to investigate differences among different reciprocal crosses of indigenous chickens and general linear models and covariance determination for the nutrition study. The on-station studies brought greater understanding of performance and production characteristics of indigenous chickens and the influence of management practices on these characteristics. The field surveys and stakeholder consultations helped in understanding the overarching issues affecting the productivity of the indigenous chickens systems and their place in the livelihoods of smallholder farmers. These activities created strong networking opportunities with stakeholders from a wide spectrum. The on-farm farmer participatory research involved selection of 200 farmers in five regions followed by training and introduction of interventions on improved management practices which included housing, vaccination, deworming and feed supplementation. Implementation and monitoring was mainly done by individual farmers continuously for close to one and half years. Six quarterly visits to the farms were made by the research team to monitor and provide support for on-going project activities. The data collected has been analysed for 5 consecutive 3-monthly periods. Descriptive and inferential statistics were applied to analyse the data collected involving treatment applications, production characteristics and flock demography characteristics. Out of the 200 farmers initially selected, 173 had records on treatment applications and flock demography characteristics while 127 farmers had records on production characteristics. The demographic analysis with a dissimilarity index of flock size produced 7 distinct farm groups from among the 173 farms. Two of these farm groups were represented in similar numbers in each of the five regions. The research process also involved a number of dissemination and communication strategies that have brought the process and project outcomes into the domain of accessibility by wider readership locally and globally. These include workshops, seminars, field visits and consultations, local and international conferences, electronic conferencing, publications and personal communication via emailing and conventional posting. A number of research and development proposals were also developed based on the knowledge and experiences gained from the research process. The thesis captures the research process activities and outcomes in 8 chapters which include in ascending order – introduction, theoretical concepts underpinning FPR, research methodology and process, on-station research output, FPR descriptive statistical analysis, FPR inferential statistical analysis on production characteristics, FPR demographic analysis and conclusions. Various research approaches both quantitative and qualitative have been applied in the research process indicating the possibilities and importance of combining both systems for greater understanding of issues being studied. In our case, participatory studies of the improved management of indigenous chickens indicates their potential importance as livelihood assets for poor people.

Reformas ecônomicas, mudanças institucionais e crescimento na América Latina

As reformas econômicas implementadas pelos países da América Latina a partir da segunda metade dos anos 1980 mudaram em definitivo o panorama da região. Os principais objetivos dessas medidas foram promover a recuperação econômica e gerar condições para o crescimento sustentado. De maneira a avaliar os efeitos das reformas sobre o desempenho econômico dos países e, principalmente, sobre a taxa de crescimento, muitos trabalhos recentes se dedicaram ao tema. Esta dissertação se enquadra nessa linha de pesquisa acerca dos efeitos das reformas sobre o crescimento das economias latino-americanas. O foco, entretanto, não fica restrito à avaliação do impacto sobre o produto per capita desses países. Os determinantes fundamentais do produto são igualmente considerados: produtividade total e parcial de fatores e acumulação de capital. De forma a empreender tal investigação, partiu-se de uma base teórica de modelos neoclássicos de crescimento. O caráter institucional das reformas permitiu complementar esse arcabouço conceitual com elementos de modelos que incluem variáveis de natureza institucional no rol dos determinantes do produto per capita. Assim, a abordagem empregada na dissertação possibilitou testar de que forma essas medidas, vistas como mudanças institucionais, afetaram as variáveis de interesse, algo que não havia sido tratado de forma satisfatória pela literatura. A análise econométrica desenvolvida com base em um painel de 17 países latino americanos no período entre 1970 e 1995, considerados subperíodos de cinco anos, revelou que as cinco áreas de reforma consideradas - abertura comercial, liberalização da conta de capital, privatização e reformas financeira e tributária - tiveram um impacto positivo sobre o produto per capita. Além disso, a investigação empírica indicou ter sido o efeito positivo sobre a produtividade do capital físico o principal canal pelo qual as reformas promoveram o crescimento dessas economias. Há evidências de que o efeito sobre a acumulação de capital também se constituiu em um canal importante.

Modelos de crescimento e a teoria do desenvolvimento econômico

A teoria econômica recoloca, na atualidade, o tema do crescimento econômico após um longo período dedicado aos problemas de estabilização e equilíbrio fiscal. Na falta de um novo sistema conceitual, os modelos de crescimento estão buscando as categorias centrais de análise nos modelos teóricos do passado, particularmente na teoria do desenvolvimento econômico. Nesse sentido, são retomados conceitos como rendimentos crescentes, big push, economias de escala, que foram desenvolvidos por autores como Allyn Young, P. Rosenstein-Rodan, Ragnar Nurkse e outros expoentes da teoria do desenvolvimento dos anos 50. Nesta pesquisa, pretendo reconstituir os principais modelos de crescimento arquitetados por esses autores, analisar sua influência sobre o Modelo Brasileiro de Desenvolvimento e verificar de que forma essas categorias econômicas estão sendo recuperadas pelos novos modelos de crescimento da atualidade.

Technical change and factor shares

The implications of technical change that directly alters factor shares are examined. Such change can lower the income of some factors of production even when it raises total output, thus offering a possible explanation for episodes of social conflict such as the Luddite uprisings in 19th century England and the recent divergence in the U. S. between wages for skilled and unskilled labor. An explanation also why underdeveloped countries do not adopt the latest technology but continue to use outmoded production methods. Total factor productivity is shown to be a misleading measure of technical progress. Share-altering technical change brings into question the plausibility of a wide class of endogenous growth models.

Stage level measurement of information and communication technology in organizations

Na moderna Economia do Conhecimento, na Era do Big Data, entender corretamente o uso e a gestão da Tecnologia de Informação e Comunicação (TIC) tendo como base o campo acadêmico de estudos de Sistemas de Informação (SI), torna-se cada vez mais relevante e estratégico para as organizações que pretendem: permanecer em atividade, estar aptas para atender novas demandas (internas e externas) e enfrentar as complexas mudanças na competição de mercado. Esta pesquisa utiliza a teoria dos estágios de crescimento, fundamentada pelos estudos de Richard L. Nolan nos anos 70. A literatura acadêmica relacionada com modelos de estágios de crescimento e o contexto do campo de estudo de SI, fornecem as bases conceituais deste estudo. A pesquisa identifica um modelo com seus construtos relacionados aos estágios de crescimento das iniciativas da TIC/SI organizacional, partindo das variáveis de benchmark de segundo nível de Nolan, e propõe sua operacionalização com a criação e desenvolvimento de uma escala. De caráter exploratório e descritivo, a pesquisa traz contribuição teórica ao paradigma da teoria dos estágios de crescimento, adicionando um novo processo de crescimento em sua estrutura conceitual. Como resultado, é disponibilizado além de um instrumento de escala bilíngue (português e inglês), recomendações e regras para aplicação de um instrumento de pesquisa do tipo survey, na continuidade deste estudo. Como implicação geral desta pesquisa, é esperado que seu uso e aplicação ao mensurar a avaliação do nível de estágio da TIC/SI em organizações, possam auxiliar dois perfis de indivíduos: acadêmicos que estudam essa temática, assim como, profissionais que buscam respostas de suas ações práticas nas organizações onde trabalham.

The spenders-hoarders theory of capital accumulations, wealth distribution and fiscal policy

This paper proposes a simple OLG model which is consistent with the essential facts about consumer behavior, capital accumulation and wealth distribution, and yields some new and surprising conclusions about fiscal policy. By considering a society in which individuais are distinguished according to two characteristics, altruism and wealth preference, we show that those who in the long run hold the bulk of private capital are not so rnuch motivated by dynastic altruism as by preference for wealth. Two types of social segmentation can result with different wcalth distribution. To a large extcnt our results seem to fit reality better than those obtained with standard optimal growth models in which dynastic altruism ( or r ate o f impatience) is the only source of heterogeneity: overaccumulation can appear, public debt and unfunded pensions are not neutra!, estate taxation can improve the welfare of the top wealthy.

Desenvolvimento nacional, desenvolvimento regional e moeda: notas teóricas à luz da economia política do desenvolvimento

This work analyses the ability of National States and regions have to formulations development strategies. Redeeming the initial development concept as a conflictual process, the hypothesis is that it presents internal and external constraints, as the latter have a higher preponderance, revealed the role played by money. In this case, one can point to as sub-hypothesis that the growth models with external constraint, mainly through the balance of payments, may illustrate the fact that countries are subject to international economic interactions that limit the possibility of bringing acylating strategies well successful in overcoming backwardness. For the specific case of regions, indicates that the external constraint remains an element of embarrassment for regional development, but redeems itself the center-periphery relations in this context to discuss the role of monetary and financial system as an explanation for the disparities regional income. On the domestic front, we highlight the importance of social structures of accumulation as an element of internal cohesion necessary to achieve successful development trajectories. It points also to the importance of the State in the process rescuing some of the main theoretical contributions of the political economy of development, incorporating the concept of globalization on theoretical frameworks presented. This construction where development depends on the actions of external and internal conditions, where money plays a key role as a guideline for reflections on regional development. The attempt was to transplant our considerations on the general development to address the case of regions. Finally, we conclude by greater confidence in the hypothesis and sub-hypotheses of departure, which led to propositions of economic policies

Crescimento econômico e restrição externa: evidências empíricas na economia brasileira (1991-2010)

This study aims to investigate the influence of the balance of payments constrained on economic growth in Brazil from 1991 to 2010. With this order, are shown some of the Keynesian balance of payments constrained growth models, inspired by Thirlwall (1979) and Kaldor (1970), which are supported by important points in common, such as adherence to the principle of effective demand. Given that within this theoretical perspective, there is no consensus about the best model to explain the growth rate allowed by the balance of payments constraint, the results are presented by the representative of the empirical literature that addresses the topic, which are necessary for understand the Brazilian case. From the estimation of the income elasticity of imports (0.85) via autoregressive vectors with error correction (VEC), it was calculated five growth rates of income, as predicted by the models of Thirlwall (1979), Thirlwall and Hussain (1982), Moreno-Brid (1998, 2003) and Lourenço et al. (2011) and compared with the actual growth rate. The empirical analysis has shown that: it can not reject the presence of external constraint in the Brazilian economy, there is a strong similarity in growth rates provided by different modeling suggest that growth with external constraint. In addition, when using data in quarterly for the period after 1990 there are no factors that could cause instability in the parameters of the import function (income elasticity and price elasticity of imports) within the period, which indicates that the structural break widely associated with the year 1994 was not confirmed by this study

Modelagem e estimação de parâmetros genéticos e fenotípicos para pesos do nascimento à seleção (378 dias) de machos Nelore

Genetic parameters for weights (17, 942 records), obtained in intervals of 60 days, from the birth to selection (378 days of age), of 2,582 males of the Nellore breed was estimated in univariate analyses by the Maximum Restricted Likelihood method. The models of analysis models included the fixed effects of contemporary groups, month of birth, mother age and age when the weights were collected as covariate. Three models differing in random effects were tested: the model 1 (M1) was adjusted for the direct and maternal addictive genetic effects and maternal permanent environment; in model 2 (M2) the maternal genetic effect was excluded; and the model 3 (M3) was only adjusted for the direct addictive genetic effect. The test of likelihood (LRT) detected significant differences, for all the ages, of M2 and M1 in relation to the simple model (M3), evidencing the importance of the maternal effects. Except for the birth weight (0.40), low values (0.05 to 0.12) of h(2) were found for M1 and M2 until 8 months of age and, after this period, reasonable increase could be observed, reaching 0.28 until 13 months of age. The estimates of the total variance fraction, due to the effect of maternal permanent environment, were high and practically became unaffected between the models 1 and 2. Maternal effects, not necessarily decomposed (in genetic addictive and permanent environment), affected the Nellore males growth. Models that contemplate maternal effects, besides the genetic addictive direct effects, are more realistic to describe the trajectory of the variances in the initial phases of growth of Nelore male calves.

Modelos matemáticos utilizados para descrever curvas de crescimento em aves aplicados ao melhoramento genético animal

A utilização de funções matemáticas para descrever o crescimento animal é antiga. Elas permitem resumir informações em alguns pontos estratégicos do desenvolvimento ponderal e descrever a evolução do peso em função da idade do animal. Também é possível comparar taxas de crescimento de diferentes indivíduos em estados fisiológicos equivalentes. Os modelos de curvas de crescimento mais utilizados na avicultura são os derivados da função Richards, pois apresentam parâmetros que possibilitam interpretação biológica e portanto podem fornecer subsídios para seleção de uma determinada forma da curva de crescimento em aves. Também pode-se utilizar polinômios segmentados para descrever as mudanças de tendência da curva de crescimento animal. Entretanto, existem importantes fatores de variação para os parâmetros das curvas, como a espécie, o sistema de criação, o sexo e suas interações. A adequação dos modelos pode ser verificada pelos valores do coeficiente de determinação (R2), do quadrado médio do resíduo (QM res), do erro de predição médio (EPm), da facilidade de convergência dos dados e pela possibilidade de interpretação biológica dos parâmetros. Estudos envolvendo modelagem e descrição da curva de crescimento e seus componentes são amplamente discutidos na literatura. Porém, programas de seleção que visem a progressos genéticos para a forma da curva não são mencionados. A importância da avaliação dos parâmetros dos modelos de curvas de crescimento é ainda mais relevante já que os maiores ganhos genéticos para peso estão relacionados com seleção para pesos em idades próximas ao ponto de inflexão. A seleção para precocidade pode ser auxiliada com base nos parâmetros do modelo associados à variáveis que descrevem esta característica genética dos animais. Esses parâmetros estão relacionados a importantes características produtivas e reprodutivas e apresentam magnitudes diferentes, de acordo com a espécie, o sexo e o modelo utilizados na avaliação. Outra metodologia utilizada são os modelos de regressão aleatória, permitindo mudanças graduais nas covariâncias entre idades ao longo do tempo e predizendo variâncias e covariâncias em pontos contidos ao longo da trajetória estudada. A utilização de modelos de regressões aleatórias traz como vantagem a separação da variação da curva de crescimento fenotípica em seus diferentes efeitos genético aditivo e de ambiente permanente individual, mediante a determinação dos coeficientes de regressão aleatórios para esses diferentes efeitos. Além disto, não há necessidade de utilizar fatores de ajuste para a idade. Esta revisão teve por objetivos levantar os principais modelos matemáticos frequentistas utilizados no estudo de curvas de crescimento de aves, com maior ênfase nos empregados com a finalidade de estimar parâmetros genéticos e fenotípicos.

Gelation of siloxane-poly(oxypropylene) composites

The viscoelastic properties of siloxane-poly(oxypropylene) (PPO) nanocomposites prepared by the sol-gel process has been analyzed during gelation by dynamic rheological measurements. The changes of storage and loss moduli, complex viscosity and phase angle has been measured as a function of time showing the newtonian viscosity of the sol in the initial step of gelation, and its progressive transformation to a viscoelastic gel. The rheologic properties have been correlated to mass fractal, nearly linear growth models and percolation theory. This study, completed by quasi-elastic light scattering and Si-29 solid state nuclear magnetic resonance measurements, shows that the mechanisms of gelation of siloxane-PPO hybrids depend on the molecular weight of the polymer and on the pH of the hybrid sol. For hybrids prepared in acid medium, a polymerization involving silicon reactive species located at the extremity of the polymer chains and presenting a functionality f = 2 occurs, forming a fractal structure during the first stage of sol-gel transition. For samples prepared under neutral pH, the fractal growth is only observed for hybrids containing short polymer chains (M-w similar to 130 gmol(-1)). The fractal dimensionality determined from the change in the rheological properties, indicates that the fractal growth mechanism changes from reaction-limited to diffusion-limited aggregation when the molecular weight of the PPO increases from 130 to 4000 gmol(-1) and as catalyst conditions change from acidic to neutral. Near the gel point, these hybrid gels have the typical scaling behavior expected from percolation theory. (C) 2002 Elsevier B.V. B.V. All rights reserved.

Rheological study of the thermoreversible sol-gel transition of sulfate modified zirconyl chloride aqueous sol

The sols prepared by mixing a ZrOCl2 acidified solution to a hot H2SO4 aqueous solutions were studied in order to clarify the mechanism of thermoreversible sol-gel transition observed in this system. The viscoelastic properties of these suspensions were analyzed during the sol-gel transition by dynamic rheological measurements and quasi-elastic light scattering. The rheological properties were correlated to mass fractal and nearly linear growth models, and percolation theory. The results evidence that the thermoreversible sol-gel transition in this system is due to the formation of a network of physically linked aggregates having fractal structure. The decrease of the SO42- contents in the initial solution leads to the decrease of the fractal dimensionality from 2.3 to 1.8, indicating a change of the kinetic mechanism of aggregate growth. Near the gel point these samples have the typical scaling expected from percolation theory. (C) 2004 Elsevier B.V. All rights reserved.

Sol-gel transition in SnO2 colloidal suspensions: viscoelastic properties

This paper describes particle aggregation process during gelation of SnO2 hydrosols. The effect of the concentration of SnO2 colloidal particles on the kinetics of gelation of hydrosols containing PVA (poly(vinyl alcohol)) was analysed by dynamic rheological measurements. The complex viscosity and the storage and loss moduli have been measured during the sol-gel transition and the results correlated to mass fractal growth, nearly linear growth models, and scalar percolation theory. The analysis of the experimental results shows that a linear aggregation occurs in the initial step of the gelation followed by a fractal growth to form a three-dimensional network. Near the gel point this physical gel exhibits the typical scaling expected from an electrical percolation analogy. (C) 1999 Elsevier B.V. B.V. All rights reserved.