Dinámica de la restauración de suelos agrícolas a través de la creación de islas de fertilidad orgánica en un cultivo de Plátano (Musa AAB SIMMONDS) en el Valle del Cauca, Colombia

Actualmente gran parte de los suelos del mundo han perdido la capacidad de producir debido principalmente a inadecuadas prácticas agrícolas con múltiples consecuencias como pérdidas de carbono, compactación del suelo, salinización y pérdida de la biodiversidad del suelo, entre otras. El cultivo de plátano no ha sido ajeno a esta problemática y como consecuencia su producción ha disminuido en los últimos años. La meta indudablemente es aumentar la producción conservando los recursos naturales. Para asegurar esto se deben implementar técnicas basadas en lo orgánico para devolverle al suelo su estado natural y su capacidad productora. Adoptar sistemas que permitan restaurar los suelos degradados, mejorando las propiedades físicas, químicas y biológicas y así generar condiciones óptimas para el desarrollo de los cultivos agrícolas. En este trabajo se buscó mejorar la calidad del suelo a través de la creación de islas de fertilidad del suelo, utilizando la técnica de Fertilización Orgánica FBO, la cual ha sido desarrollada para mejorar la calidad del suelo en cultivos perennes. La técnica FBO permitió recuperar suelos degradados mejorando la calidad de este. A través del aporte de materia orgánica se estimuló la biodiversidad de la fauna del suelo, esta macrofauna produjo agregados biogénicos que favorecen procesos físicos del suelo de vital importancia como la agregación, infiltración, el drenaje y por ende favorecen los procesos de almacenamiento del agua y la disminución de la erosión. Todo esto ligado a los procesos de transformación de la materia orgánica que mejoró la fertilidad química del suelo.//Abstract: Currently, a large part of the world's soils has lost the capacity to produce, mainly due to inadequate agricultural practices with multiple consequences such as carbon losses, soil compaction, salinization and loss of soil biodiversity, among others. The banana crop has not been alien to this problem and as a result its production has decreased in recent years. The goal is undoubtedly to increase production while conserving natural resources. To ensure this, organic-based techniques must be implemented to restore soil to its natural state and productive capacity. Adopt systems that allow the restoration of degraded soils, improving the physical, chemical and biological properties and thus generate optimal conditions for the development of agricultural crops. In this work we sought to improve soil quality through the creation of islands of soil fertility, using the FBO Organic Fertilization technique, which has been developed to improve soil quality in perennial crops. The FBO technique allowed recovering degraded soils improving the quality of this. Through the contribution of organic matter, the biodiversity of the fauna of the soil was stimulated, this macrofauna produced biogenic aggregates that favor physical processes of the soil of vital importance such as aggregation, infiltration, drainage and therefore favor the processes of water storage and the erosion decrease. All this linked to the processes of transformation of organic matter improved the chemical fertility of the soil.Maestrí

Dependence of Surface Tension and Viscosity on Temperature in Multicomponent Alloys

Viscosity modeling for pure metals and alloys is widely studied, and many solutions for dependence of viscosity on temperature can be found in the literature for pure metals and alloys. Many of these depend on experimental data for pre-exponential and exponential coefficients. Two key models include: (i) Kaptay model for pure metals, which is completely independent of experimental data and depends only on general constants A and B for a large set of pure metals with few exceptions and (ii) Kaptay viscosity model for liquid alloys derived on the same principles, a temperature-dependent viscosity only as a function of thermophysical properties of the alloy components. In the case of surface tension, the main available models are divided into four groups: Butler formulation-based models, density-functional models, semi-empirical models, and thermodynamic geometric models. Considering the absence of adequate models for surface tension, in this work, two equations relating surface tension and viscosity for pure metals are analyzed as a function of temperature. Regarding the Egry surface tension-viscosity relation for pure metals, a new relation equation for multicomponent alloys is proposed. By applying the proposed equation, the surface tension is calculated and plotted as a function of temperature for ternary and quaternary aluminum alloys

Interconnection of thermal parameters, microstructure, macrosegregation and microhardness of unidirectionally solidified Zn-rich Zn–Ag peritectic alloys

In this work, the microstructural evolution of Zn–3.2 wt%Ag (hypoperitectic) and Zn–8 wt%Ag (hyperperitectic) alloys during transient unidirectional solidification is investigated. The experimental results include solidification thermal parameters such as the growth rate (VL), thermal gradient (GL) and tip cooling rate (), which are related to the microstructural interphase spacing (λ) by proposed experimental growth laws. It is shown that, the classical lamellar eutectic growth law λ2V = constant, applies to the growth of the peritectic Zn–Ag alloys examined, despite the different values of the constant associated with each alloy composition. In contrast, it is shown that identical functions of the form λ = constant (GL)−14 (VL)−1/8, and λ = constant () can be applied to both alloys examined. Positive solute macrosegregation was observed in regions close to the bottom of the castings. The dependence of microhardness (HV) on the length scale of the microstructures (including that of a single phase Zn 0.8 wt%Ag alloy: λC− cellular spacing) is examined. An experimental Hall–Petch type power law is proposed relating the resulting microhardness to λC for the single phase alloy, and despite the segregation profiles and the alloying differences of the hypoperitectic and hyperperitectic alloys, the average microhardnesses of these alloys is shown to be essentially constant and similar along the castings lengths63848855CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPNão tem2013/09267-0; 2012/08494-0; 2012/16328-

Phase-field simulation of microsegregation and dendritic growth during solidification of hypoeutectic al-cu alloys

Prediction of microstructure evolution and microsegregation is one of the most important problems in materials science. The dendritic growth and microsegregation provide a challenging simulation goal for computational models of solidification, in addition to being an important technological feature of many casting processes. The phase-field model offers the prospect of being able to perform realistic simulation experiments on dendrite growth in metallic systems. In this paper, the microsegregation and dendritic growth of hypoeutectic Al-Cu alloys under constant cooling rate was simulated using a phase-field model. The main new feature of the present model is based on the fact that the effect of the growth rate is incorporated via an effective partition coefficient that has been experimentally determined for a range of growth rates. It is shown that both models (Phase-field model and Scheil) have significant deviations from the experimental data when the equilibrium partition coefficient is considered in the calculations. Since the predicted results using the models yielded discrepancies from the experimental data, an experimental equation is adopted for calculating the effective partition coefficient from experimental data. The experimental equation is then adopted in the calculations of phase-field model and Scheil's equation, showing a good agreement with the experimental data20242342

Modelagem numérica da formação de microporosidade na liga Al-8,1%Cu em condições de solidificação unidirecional

O objetivo do trabalho é desenvolver e validar uma solução numérica que descreva a formação e evolução de microporosidade durante o processo de solidificação unidirecional vertical ascendente de uma liga Al-8,1% Cu. A partir da modelagem matemática do processo de solidificação unidirecional foi desenvolvido um modelo numérico que considera o acoplamento das equações de transporte térmico e de massa, e conseqüente potencialidade de nucleação e desenvolvimento de microporosidade. Paralelamente, foi construído um aparato experimental que viabilizou a verificação experimental dos resultados fornecidos pelo modelo. São realizadas simulações numéricas que são comparadas com experimentos a fim de validar o modelo, a partir de perfis térmicos, de concentração de soluto e de distribuição deporosidade

The influence of macrosegregation and dendritic arm spacings variation on corrosion resistance of the Al-4.5wt%Cu alloy

The purpose of this work was to evaluate the electrochemical behavior of an Al-4.5wt%Cu alloy solidified under unsteady-state heat flow conditions. This evaluation was carried out through the analysis of both potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS) tests in a 0.5 M NaCl solution at 25ºC. The experimental segregation profile obtained in the solidification experiment was characterized by positive and negative copper content regions at the bottom and the top of the casting, respectively. Likewise, in conventional foundry practice, in a same casting both positive and negative copper segregation regions may occur. Such casting can exhibit different corrosion responses at different locations. The influences of solute redistribution during solidification, the magnitude of dendritic spacing and hence of the Al-rich phase and of Al2Cu particles distribution along the casting on the corrosion resistance, were examined in samples collected along the casting length. The corrosion rate and impedance parameters (obtained from an equivalent circuit analysis) are also discussed.O objetivo deste trabalho foi avaliar o comportamento eletroquímico da liga Al-4,5%Cu solidificada em condições de fluxo de calor transitório. Esta evolução foi realizada através de análises de curvas de polarização e testes de espectroscopia de impedância eletroquímica (EIE), em solução de 0,5M de NaCl à 25°C. O perfil de segregação obtido no experimento de solidificação foi caracterizado por segregação positiva e negativa de cobre, respectivamente, na base e no topo da amostra. Igualmente, na prática de fundição convencional, em um mesmo lingote podem ocorrer regiões de segregação de cobre positiva e negativa. O lingote pode apresentar diferentes respostas à corrosão em diferentes partes, como função do arranjo microestrutural. As influências na resistência à corrosão da redistribuição do soluto durante a solidificação, a magnitude dos espaçamentos dendríticos e a distribuição das partículas da fase rica em Al e Al2Cu ao longo do lingote, foram examinadas com coleta de amostras ao longo do lingote. A taxa de corrosão e parâmetros de impedância (obtidos de uma análise de circuito equivalente) são também discutidos.542552Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

On the Determination of Molar Heat Capacity of Transition Elements: From the Absolute Zero to the Melting Point

Molar specific heat is one of the most important thermophysical properties to determine the sensible heat, heat of transformation, enthalpy, entropy, thermal conductivity, and many other physical properties present in several fields of physics, chemistry, materials science, metallurgy, and engineering. Recently, a model was proposed to calculate the Density of State by limiting the total number of modes by solid–liquid and solid–solid phase nucleation and by the entropy associated with phase transition. In this model, the new formulation of Debye’s equation encompasses the phonic, electronic, and rotational energies contributions to the molar heat capacity of the solids. Anomalies observed in the molar specific heat capacity, such as thermal, magnetic, configurational transitions, and electronic, can be treated by their transitional entropies. Model predictions are compared with experimental scatter for transitional elements

TECHNICAL CHALLENGES, IMPACTS AND PERSPECTIVES FOR ELECTRIC VEHICLES (EVS)

Preventing environmental issues and growing concerns about global energy crises are driving the need for new opportunities and technologies that can meet significantly greater demand for cleaner generation and products, zero-carbon, and sustainable energy systems. This requires developing more efficient transport and energy generation. Changing the transport model to electric is a promising approach for ecological systems and for reducing the problems of climate change. This article inspects the current status, latest deployment, and challenging issues when installing an electric vehicle charging and infrastructure (EVs) system in conjunction with various international standards and charging codes. The article further analyzes the impacts of (EVs) and perspectives on society. A complete assessment of charging systems for (EVs) with battery charging techniques. Besides, the beneficial and harmful impacts of (EVs) are categorized and carefully reviewed. Corrective measures for harmful impacts are presented and the benefits obtained from them are highlighted. Bidirectional charging offers the vehicle's key feature for smart grid technology. In this article, the current challenging issues due to the massive deployment of (EVs) and future research trends are also presented.Preventing environmental issues and growing concerns about global energy crises are driving the need for new opportunities and technologies that can meet significantly greater demand for cleaner generation and products, zero-carbon, and sustainable energy systems. This requires developing more efficient transport and energy generation. Changing the transport model to electric is a promising approach for ecological systems and for reducing the problems of climate change. This article inspects the current status, latest deployment, and challenging issues when installing an electric vehicle charging and infrastructure (EVs) system in conjunction with various international standards and charging codes. The article further analyzes the impacts of (EVs) and perspectives on society. A complete assessment of charging systems for (EVs) with battery charging techniques. Besides, the beneficial and harmful impacts of (EVs) are categorized and carefully reviewed. Corrective measures for harmful impacts are presented and the benefits obtained from them are highlighted. Bidirectional charging offers the vehicle's key feature for smart grid technology. In this article, the current challenging issues due to the massive deployment of (EVs) and future research trends are also presented

Produção de Biodiesel de óleo cru refinado e óleo de fritura de soja

A busca pela redução na pegada ambiental que deixamos em nosso planeta depende fortemente da descarbonificação dos processos de geração de energia. Este artigo teve como objetivo avaliar questões energéticas do biodiesel proveniente de óleo de soja. Para tal, óleo cru refinado e óleo utilizado no processo de fritura de alimentos foram utilizados para produção de biodiesel e, consequentemente, glicerina. O processo  de produção do biodiesel adotado foi o de transesterificação, utilizando utilizando metanol e hidróxido de potássio (KOH). Os ensaios e análises foram  realizadas no Núcleo de Inovações Tecnológicas – NIT, Universidade Estadual do Oeste do Paraná – Unioeste. Foram realizadas três fabricações de biodiesel para cada tipo de óleo, as análises foram realizadas em duplicata para cada biodiesel totalizando seis resultados de cada analise para os dois tipos de óleo, os resultados apresentados são as médias aritméticas das análises. O rendimento na produção do biodiesel de óleo cru de soja foi 5,7% superior ao rendimento quando comparado ao óleo de fritura, 92,80% e 87,10% respectivamente. Análises realizadas com os produtos resultantes, biodiesel e glicerina, indicaram que ambos os produtos se enquadraram a normas regulamentadoras apresentadas pela ANP. Portanto, a utilização de  óleo de soja residual do processo de fritura de alimentos é uma alternativa tecnicamente adequada para produção de biodiesel

Modelagem física do sistema de alimentação do processo Twin Roll para lingotamento contínuo de tiras de aço inoxidável

It can be understood by process modeling the development of a quantitative or qualitative representation of the physical phenomena associated to the process. Important factors in the design of a metal feeding system for thin strip casting of steels are size and shape of tundish, type and location of flow control devices. In this article, simulations concerning the Twin Roll continuous caster of steels process at IPT (Technologic Research Institute) are performed. In order to optimize steel flow a 1:1 water model was designed and constructed with components made of acrylic, water as the simulation fluid and potassium permanganate as a pigment. The use of an appropriate arrangement of turbulence inhibiting dams and weirs can provide an output fluid flow pattern suitable for input to a thin strip caster. The simulator has contributed to improve the productivity and cleanliness of the strip casting of steel.Entende-se, por modelagem de processo, o desenvolvimento de uma representação quantitativa ou qualitativa dos fenômenos físicos associados ao processo. O tipo e a forma do distribuidor, o controle do fluxo e o posicionamento de obstáculos são importantes fatores no projeto do sistema de alimentação de metal líquido para o lingotamento contínuo de tiras de aço. Nesse trabalho, são realizadas simulações do processo Twin Roll de lingotamento contínuo de tiras de aços, utilizando, como referência tecnológica, o equipamento-piloto instalado nas dependências do Instituto de Pesquisas Tecnológicas do Estado de São Paulo (IPT). Foi construído um simulador a frio do distribuidor do equipamento (em escala 1:1), com componentes feitos de acrílico, com água como fluido de simulação e com permanganato de potássio como corante. O simulador contribuiu para melhorias de produtividade e para a limpeza do produto.179184Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP