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Search Results: 1 - 10 of 693 matches for " Erasmo Cadena "
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Flexible Co-Combustion of High Ratios of Sustainable Biomass with Coal in Oxy-CFB Boiler for CO2 Capture  [PDF]
Jose A. Gutiérrez Bravo, Raquel Garcia, Erasmo Cadena
Journal of Power and Energy Engineering (JPEE) , 2018, DOI: 10.4236/jpee.2018.611002
Abstract: Coal-fired plants are under pressure to reduce their carbon-intensity. Available options include co-firing CO2-neutral biomass, oxy-fuel-combustion as part of a carbon capture process or a combination of both to give a “CO2-negative” power plant. BioCCS, the combination of CO2 Capture and Storage (CCS) with sustainable biomass conversion, is the only large-scale technology that can achieve net negative emissions. Combining, developing and demonstrating the oxy-combustion of high ratios of sustainable biomass with coal in flexible circulating fluidized bed (CFB) boiler will bring significant advances in the reduction of greenhouse gases (GHG) emissions. Areas addressed include possibilities for: biomass characterization; handling and feeding; co-firing ratios definition; CFB oxy-co-combustion studies; combustion performance; boiler flexibility in fuel and load; main emissions analysis; slaging, fouling and agglomeration; corrosion and erosion; and implications on plant operation and associated costs. The article will detail a comprehensive understanding on sustainable biomass supply, co-firing ratios and how direct biomass co-combustion under oxy-fuel conditions can be implemented. It seeks to push biomass co-combustion in future large-scale oxy-fuel CFB power stations to high thermal shares while enhancing the power plants’ operational flexibility, economic competitiveness and give operational procedures. There will be a need to consider the public acceptance of power production from coal and coal sustainability, by its combination with renewable sources of energy (biomass).
Novel Simplified Method for Coalbed Methane Feasibility Evaluation  [PDF]
Jose A. Gutiérrez, Raquel García, Erasmo Cadena
International Journal of Clean Coal and Energy (IJCCE) , 2018, DOI: 10.4236/ijcce.2018.74004
Abstract: Coal during its carbonization process produces a gas. This gas, mainly formed by methane, can be used. This gas, coalbed methane (CBM), is usually mainly formed by methane and can be considered similar to natural gas as energy source. The evaluation of the techno-economic feasibility of the extraction of this gas depends on a large number of complex different factors. The work carried out covers the different aspects to simplify the first approach for CBM feasibility quantification considering a short number of indicators. A theoretical review and a state of the art description have been carried out, taking into account all the factors that can influence in the development of a CBM project. After that, technical feasibility has been used to evaluate total amount of gas that can be recovered. The last step was to evaluate economic feasibility to know how much gas could be economically profitable. Conclusions got have been used to develop a simple method for evaluating CBM economic feasibility considering just four easy known parameters of coal beds. These are: the rank, the thickness, the gas concentration, and the permeability.
Coalbed Methane Potential in the Basin Guardo-Barruelo (North Spain)  [PDF]
Jose A. Gutierrez Bravo, Raquel Garcia, Erasmo Cadena
Journal of Power and Energy Engineering (JPEE) , 2019, DOI: 10.4236/jpee.2019.71001
Abstract: Coal during its carbonization process produces a gas, which, mainly formed by methane, can be used. The use of CBM (Coal bed methane) as an energetic resource is not much known in Spain. This work is the first step to enhance the development of this resource in Castilla y León Guardo-Barruelo basin. A review of the state of the art is introduced, taking into account all the factors that can influence in the development of a CBM project. Then CBM resources have been quantified for Guardo-Barruelo basin accurately for every coal bed. After that, technical feasibility has been used to evaluate total amount of gas that can be recovered.
Effects of Solar UV Radiation on Materials Used in Agricultural Industry in Salta, Argentina: Study and Characterization  [PDF]
Carlos Cadena, Delicia Acosta
Journal of Materials Science and Chemical Engineering (MSCE) , 2014, DOI: 10.4236/msce.2014.24001
Abstract: The current study presents the characterization of three types of materials after exposure to solar UV radiation. The selection of the materials is related to socio-economic aspects and rural activities in the northwest of Argentina (a.k.a. NOA). The objective was to establish a time parameter that allows estimating the durability of the materials according to their use. One of the materials is used as a protective cover (polyethylene film) of greenhouses, which are used for crop cultivation in the area. Another material is used in photovoltaic modules (PVMs), which are used to supply energy in isolated areas and the third material is sunscreen used by people that are exposed to UV radiation during rural activities. Degradation or deterioration of the materials was monitored using different spectroscopic assays: infrared was used to detect any structural changes in the material, X-rays were used for possible changes in the crystalline structure of the material, and spectral transmittance as this property is likely to be affected by changes in the structure of the material. The results showed that degradation of polyethylene seems to be related to the diminution in transparency and the loss of mechanical resistance with increasing exposure time. The decrease in transparency of one of the layers of a PVM caused a considerable decrease in the energy generated, whereas the sunscreens with a low sun protection factor (SPF) rapidly lost their protective properties and changed their photostability properties. Our results revealed a relationship between relative transmittance loss and exposure timse, which allows estimating the stability of different materials.
Revisiting extensions of regularly varying functions
Meitner Cadena
Mathematics , 2015,
Abstract: Relationships among the classes ${\cal M}$, ${\cal M}_\infty$, and ${\cal M}_{-\infty}$ and the class of \emph{O}-regularly varying functions are shown. These results are based on two characterizations of ${\cal M}$, ${\cal M}_\infty$, and ${\cal M}_{-\infty}$ provided by Cadena and Kratz in [7] and a new one given in this note.
A note on Tauberian Theorems of Exponential Type
Meitner Cadena
Mathematics , 2015,
Abstract: Tauberian Theorems of exponential type provided by Kohlbecker, de Bruijn, and Kasahara are proved in only one Tauberian theorem. To this aim, the structure of those classical tauberian theorems is identified and, using a relationship recently proved by Cadena and Kratz, the relationships among its components are given.
A simple estimator for the $\mathcal{M}$-index of functions in $\mathcal{M}$
Meitner Cadena
Statistics , 2015,
Abstract: An estimator for the $\M$-index of functions of $\mathcal{M}$, a larger class than the class of regularly varying (RV) functions, is proposed. This index is the tail index of RV functions and this estimator is thus a new one on the class of RV functions. This estimator satisfies, assuming suitable conditions, strong consistency. Asymptotic normality of this estimator is proved for a large class of RV functions, showing a better performance than some well-known estimators. Illustrations with simulated and real life datasets are provided.
Mortality Models based on the Transform $\log(-\log x)$
Meitner Cadena
Statistics , 2015,
Abstract: A new stochastic method for describing mortality is proposed and explored. It is based on differences of observed times series of the transform $\log(-\log x)$ of survival probabilities which seem to follow simple patterns over the years. These common structures are gathered by a representation based on age-constants and time-stochastic processes. From the projection of the time-processes the mortality forecasting is straigthforward. Comparisons of the new model with the well-known Lee-Carter and Cairns-Blake-Dowd models employing sex-based mortality data of some countries are provided. Some in-sample and out-of-sample goodness-of-fit criteria show that in some situations the new model performs better than the ones mentioned above. Assessments of the performance of these models using rates of mortality improvement are discussed.
A note on the best attainable rates of convergence for estimates of the shape parameter of regular variation
Meitner Cadena
Statistics , 2015,
Abstract: Hall and Welsh gave in 1984 the lowest bound so far to rates of convergence for estimates of the shape parameter of regular variation. We show that this bound can be improved.
Hadron-hadron scattering at high energies
Ferreira, Erasmo;
Brazilian Journal of Physics , 2000, DOI: 10.1590/S0103-97332000000200009
Abstract: we review the role of the qcd vacuum structure in the determination of the properties of states and processes occurring in the confinement regime of qcd. the vacuum correlation model of non-perturbative qcd is mentioned as a bridge between the fundamental theory and the description of the experiments. the model of the stochastic vacuum provides the framework in which a simple and effective description of the high-energy pp and p data can be given, leading to a determination of relevant parameters of non-perturbative qcd and to a good description of the data. a slow increase of the hadronic radii with the energy accounts for the energy dependence of all observables.
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