Equações Diferenciais Aplicadas à Dinâmica Populacional do Município de Santa Rosa/RS1 / Differential Equations Applied to Population Dynamics of the Municipality of Santa Rosa/RS

Equações Diferenciais têm configurado um importante ramo de estudo na construção e no aprimoramento de modelos matemáticos que retratam dinâmicas populacionais. Visando sua exploração para prever a variação do número de habitantes do município de Santa Rosa/RS para as próximas cinco décadas, a presente pesquisa buscou analisar como tem ocorrido o comportamento desta relação no passado e identificar as variantes que a interferem ou possam intervir no futuro, baseando-se na utilização dos modelos matemáticos de Malthus, Verhulst e Gompertz. Trata-se, portanto, de uma pesquisa que alia a abordagem qualitativa à quantitativa, de cunho documental e bibliográfico, ancorada na exploração dos respectivos modelos matemáticos, mediante o reconhecimento histórico de sua construção e da conseguinte simulação de prováveis cenários populacionais santa-rosenses em um futuro próximo. Os resultados evidenciaram maior proximidade da variação populacional do município com o Modelo de Gompertz, induzindo a crer na existência de uma taxa de inibição da variável de estado proporcional ao respectivo logaritmo. Embora a taxa de crescimento da população santa-rosense tenha sido considerável em um passado recente, a previsão é que ela continue sendo positiva, porém em taxas menores, tendendo à estabilidade de um determinado limite sustentável. 

Estudo do comportamento econômico de Santa Rosa/RS baseado em um modelo matemático de dinâmica populacional / The study of Santa Rosa’s economic behavior based on a population dynamic’s mathematical model

O estado econômico de uma região é influenciado por diversos fatores como a compra e venda de bens produzidos naquele território, mas principalmente pelo avanço populacional do mesmo. A dinâmica populacional de uma região tem impacto significativo nos processos econômicos nelas desenvolvidos, tornando necessário a reflexão conjunta desses indicadores. Nesse contexto, a modelagem matemática e as Equações Diferenciais se tornam importantes instrumentos de análise do comportamento de tais características sociais, oferecendo subsídios para planejamentos regionais futuros. Buscando refletir e comparar o crescimento populacional juntamente com o crescimento econômico do município de Santa Rosa/RS, a presente pesquisa baseou-se no modelo de dinâmica populacional de Malthus para demonstrar a importância do estudo econômico em conjunto com a projeção populacional de um território. Trata-se de uma pesquisa reflexiva sobre a influência do crescimento populacional no Produto Interno Bruto de um município, possibilitando futuros planejamentos para constante melhoria da sociedade.

Feasibility of silicomanganese slag as cementitious material and as aggregate for concrete

The need to reduce environmental impact inevitably leads to research on new, more sustainable construction materials. In recent times, the use of the main slags from the steel industry has been vigorously investigated; however, the use of other industrial by-products should also be considered. This study aims to analyze the viability of the use of value-added silicomanganese slag (siderurgical aggregates from ferroalloy industries) in two ways. On the one hand, the potential of ground silicomanganese siderurgical aggregates as a binder or supplementary cementitious material (SCM) due to their high content of silica and alumina. On the other hand, the use of silicomanganese siderurgical aggregates for the manufacture of concrete. The hydraulicity of the ground material has been determined by designing mortars with 20 % replacement of cement and comparing the mechanical performance with Portland cement and fly ash at different ages. Its application as a granulometric skeleton of concrete has been analyzed by comparing the physical-mechanical performance and docility in the fresh state with a conventional limestone aggregate concrete. The results obtained guarantee the pozzolanicity of the material, obtaining resistances similar to Portland cement mortar at 90 days. Furthermore, the material as an aggregate meets the geometric, mechanical and leaching requirements imposed by current regulations, although its use with almost total replacement leads to mechanical losses of 25-30 %. For this reason, its use is only recommended in small replacement proportions or in concrete for non-structural use.This research was financed by COBASA Grupo Logístico S.L. The research was possible thanks to the collaboration of the company FERROATLANTICA, the department LADICIM (University of Cantabria) and the company ROCACERO

Siderurgical aggregate cement-treated bases and concrete using foundry sand

ABSTRACT: Cement-treated bases are soils, gravels or manufactured aggregates mixed with certain quantities of cement and water in order to improve the characteristics of a base or sub-base layer. Due to the exploitation of natural aggregates, it is a matter of importance to avoid shortage of natural resources, which is why the use of recycled aggregates is a practical solution. In this paper we studied the feasibility of the use of untreated electric arc furnace slags and foundry sand in the development of cement-treated bases and slag aggregate concrete with a lower quantity of cement. We analyzed the physical, mechanical and durability characteristics of the aggregates, followed by the design of mixes to fabricate test specimens. With cement-treated bases, results showed an optimal moisture content of 5% and a dry density of 2.47 g/cm3. Cement-treated bases made with untreated slag aggregate, foundry sand and 4% of cement content showed an unconfined compression strength at seven days of 3.73 MPa. For siderurgical aggregate concrete mixes, compressive strength, modulus of elasticity and flexural strength tests were made. The results showed that the mixes had good mechanical properties but durability properties could be an issue

Modelagem matemática que descreve o comportamento da demanda de energia elétrica de uma cooperativa de eletrificação da cidade de Santa Rosa / Mathematical modeling that describes the behavior of the electricity demand of an electrification cooperative in the city of Santa Rosa

Neste artigo foi desenvolvido um modelo matemático usando o método de Malthus, aplicado na análise do comportamento da demanda e do consumo da energia elétrica residencial no município de Santa Rosa/RS, os dados foram fornecidos pela Cooperativa de Eletrificação COOPERLUZ, foi feita a análise dos períodos de consumo elétrico, considerando as estações do ano, e sua taxa de crescimento com base no seu histórico de consumo. Foi aplicado a metodologia de pesquisa de modelagem matemática, mais especificamente o Modelo de Malthus, que auxiliou na determinação da função através dos dados com uma margem de erro baixa, comprovada com a correlação de Pearson. Apresenta-se alguns destes resultados e sua análise. Essa determinação permite analisar o comportamento de consumo de forma que poderá auxiliar as empresas geradoras de energia futuramente nas decisões necessárias para o melhoramento de seu atendimento

Modelagem matemática da incidência de casos de câncer na cidade de Santa Rosa – RS / Mathematical modeling of the incidence of cancer cases in the city of Santa Rosa – RS

Neste artigo apresenta-se a construção de modelos matemáticos que descrevem o comportamento dos casos de câncer de próstata diagnóstico C61 e mama diagnóstico C50 no município de Santa Rosa – RS no período de 2013 a 2021. Utilizando o Modelo de Malthus, Interpolação polinomial de Lagrange e de Regressão Linear, foram desenvolvidas funções que descrevem o comportamento do número de casos de câncer de próstata e mama. Para obter os dados reais sobre os casos de câncer durante os anos de 2013 até 2021 foi o utilizado o DataSUS, o serviço de informações do Sistema Único de Saúde (SUS). Comparando os dados obtidos através dos cálculos e os valores reais foi encontrado um modelo de função, que melhor se adaptou para cada tipo de câncer

Influence of Partial and Total Replacement of Used Foundry Sand in Self-Compacting Concrete

ABSTRACT: In this work, the feasibility of partially and totally replacing natural sand with used foundry sand in self-compacting concrete was studied. Natural sand was replaced in 50% and 100% vol. by used foundry sand. The fresh state properties parameters analyzed in this study were slump flow, t500, V-funnel, Japanese ring and L-box following EFNARC guidelines. Results indicated an improvement in the fresh state properties when used foundry sand was utilized for partial and total replacement. The mechanical properties compressive strength and splitting tensile strength were obtained and analyzed at 7 and 28 days. Regarding the compressive strength, used foundry sand enhanced compressive strength by up to 67% compared to control concrete. For splitting tensile strength, the self-compacting concrete with 50% vol. of used foundry sand displayed a slight decrease (2.8%) compared with the control concrete. SEM images showed that the concretes with used foundry sand had a less porous and more compacted matrix than the control concrete. It was concluded that the incorporation of used foundry sand in large volumes can be utilized as a sustainable alternative natural fine aggregate

Fatigue Behaviour of Concrete Using Siderurgical Aggregates

The use of concrete with aggregates with reduced environmental impact, as is the case of concrete with siderurgical aggregates (recovered slags), will inevitably increase in the future, as a result of policies promoting development of more sustainable construction materials. These concretes offer an excellent response to static loads, but their behaviour under dynamic loads has not yet been studied. The aim of this study is to characterize the fatigue behaviour, in terms of fatigue limit, of a concrete with siderurgical aggregates by comparing it with an analogous conventional limestone concrete. This characterization was carried out using the Locati method, which stands out for its convenience, speed and low cost, with the feature of being carried out at a high frequency corresponding to the resonance frequency. Performing high-frequency tests has drastically reduced test times and thus costs. Likewise, the results obtained show that, using various criteria found in the literature, concrete with siderurgical aggregates has a higher fatigue limit in absolute terms (MPa), but a lower one in relative terms (% fc).This research was co-financed by the European Regional Development Fund (ERDF) and the Ministry of Economy, Industry, and Competitiveness (MINECO) within the framework of the project RTC-2016-5637-3

Recycled polyethylene fibres for structural concrete

Modern society demands more sustainable and economical construction elements. One of the available options for manufacturing this type of element is the valorisation of end-of-life waste, such as, for example, the recycling of polymers used in industry. The valorisation of these wastes reduces costs and avoids the pollution generated by their landfill disposal. With the aim of helping to obtain this type of material, this work describes a methodology for recycling polyethylene for the manufacture of fibres that will later be used as reinforcement for structural concrete. These fibres are manufactured using an injection moulding machine. Subsequently, their physical and mechanical properties are measured and compared with those of the material before it is crushed and injected. The aim of this comparison is to evaluate the recycling process and analyse the reduction of the physical-mechanical properties of the recycled polyethylene in the process. Finally, to determine the properties of the fibre concrete, three types of concrete were produced: a control concrete, a reinforced concrete with 2 kg/m³ of fibres, and a reinforced concrete with 4 kg/m³ of fibres. The results show an enhancement of mechanical properties when the fibres are incorporated, particularly the tensile strength; and they also show excellent performance controlling cracking in concrete.This research was funded by the LADICIM (Laboratory of Materials Science and Engineering), Universidad de Cantabria. E.T.S. de Ingenieros de Caminos, Canales y Puertos, Av./Los Castros 44, 39005 Santander, Spain