1,720,963 research outputs found
Kinetic Characterization of the Residues from the Pruning of Apple Trees for their Use as Energy Vectors
No full textNumerical Simulation of the Heat Transfer in the Cryoprobe of an Innovative Apparatus for Cryosurgery
No full textCryosurgery is a rapidly developing discipline, alternative to conventional surgical techniques, used to destroy cancer cells by the action of low temperatures. Currently, the refrigeration is obtained via the adiabatic expansion of gases in probes used for surgeries, with the need of inherently dangerous pressurized vessels. The proposed innovative prototypal apparatus aims to reach the cryosurgical temperatures exploiting a closed-loop refrigeration system, avoiding the hazardous presence of pressurized vessels in the operating room. This study preliminarily examines the technical feasibility of the cryoablation with this machine focusing the attention on the cryoprobe design. Cryoprobe geometry and materials are assessed and the related heat transfer taking place during the cryoablation process is simulated with the aid of the computational fluid dynamics software ANSYS®Fluent. Parametric analyses are carried out varying the length of the collecting tubes and the inlet velocity of the cold carrier fluid in the cryoprobe. The values obtained for physical quantities such as the temperature reached in the treated tissue, the width of the obtained cold front, and the maximum pressure required for the cold carrier fluid are calculated and discussed in order to prove the effectiveness of the experimental apparatus and develop the machine further
A review on MCFC matrix: State-of-the-art, degradation mechanisms and technological improvements
No full textMolten Carbonate Fuel Cells (MCFCs) are a promising technology as sustainable power generators as well as CO2 selective concentrators for carbon capture applications. Looking at the current cell configuration, several issues, which hinders a stable long-term operation of the system, are still unsettled. According to reference studies, the ceramic matrix is one of the most critical components in view of its high impact on the cell performance since it can influence both the stability and the reaction path. Indeed, it provides the structural support and holds the molten carbonates used as electrolyte, requiring a good mechanical strength despite of a porous structure, a high specific surface area and a sufficient electrolyte wettability to avoid the electrode flooding. The matrix structure, its key-features and degradation issues are discussed starting from the state-of-the-art lithium aluminate LiAlO2 usually strengthened with Al based reinforcement agents. Since the achievable performance is strictly dependent on manufacturing, a devoted section focuses on available techniques with a view also of their environmental impacts. Considering a still insufficient performance due to the material structural and chemical instability favoured by stressful working conditions, the electric conductive ceramics are presented as alternative matrixes permitting to increase the cell performance combining oxygen and carbonate ion paths
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
CFD Simulations of a Square-Based Spouted Bed Reactor and Validation with Experimental Tests Using Rice Straw as Feedstock
No full textThe present work aims to develop a model to simulate
the fluid dynamic behavior of processes related to the
exploitation of biomass as energy source by means of
gasification. In particula
r, the attention has been
focused on a spouted bed reactor with a square base using rice straw as feedstock.
Spouted Bed reactors are attracting particular attentio
n for their use in gasificat
ion processes. In these
devices, the gas is introduced through a single nozzle at
the center of the base and, as a result, a particular
fluid dynamic pattern is followed which results in an enhanced solid circulation movement increasing therefore
the mass and energy transfer rates.
A Computational Fluid Dynamic (CFD) modeling technique was used to simulate the previously described fluid
flow. The Eulerian-Eulerian method was applied to predict t
he gas-solid flow behavior and the kinetic theory of
granular flow was incorporated within the method as
closure equation. The gas and particle dynamics were
investigated through the simulation of
different operational regimes by varying the gas flow rate at the inlet and
the amount of initial solids in
the initial bed of particles.
The obtained model was validated through experimental activities on a square based-reactor with a pyramidal
bottom. Air was used as the gas phase and the particles
were a mixture of rice straw and silica. The fluid
dynamic parameters (minimum spouting velocity, Ums and pressure drop along the bed of particles,
∆
P) of the
system were recorded for each case and compared with the values provided by the developed model.
The resulting model will be used to optimize the fluid dynamic parameters defining the process and it will lead
to an improvement of the gas-solid mass transfer and
the minimisation of the energy requirements of the
system
Feasibility Studies on the Energy Valorisation of Agricultural Residues Using Aspen Plus©
No full textA critical review of biological processes and technologies for landfill leachate treatment
No full textThe most common method to deal with the huge production of municipal wastes is still the disposal in landfills which, however, generates a leachate with high contents of organic and nitrogen pollutants. Requirements must be fixed by law to control leachate release from such landfills, and effective treatment processes and technologies must be applied to reduce its impact on the environment. Biological processes for leachate treatment are discussed in this review, in the former part of which attention is paid to leachate formation and its qualitative and quantitative features, while the latter deals with the state-of-the-art of the most effective biotechnological treatments presently employed. Processes, alternative methods, and technological improvements are compared, with special focus on novel technologies to remove nitrogen pollutants from leachate, highlighting advantages and drawbacks of each treatment
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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