1,720,959 research outputs found
Dynamic modeling and validation of a precombustion CO2 capture plant for control design
Full text linkInterfacing Models for Thermal Separation Processes with Fluid Property Data from External Sources
Full text linkSo far, when modelling processes that demand for multi-phase and multi-component fluid property data, the user has to implement the required media models in the Modelica language as these types of fluids are not supported by Modelica.Media. This paper presents
a first approach on how to implement fluid property data in process models of an existing library from external sources and highlights which problems have to be overcome. Furthermore, it provides recommendations for the design of an efficient and user-friendly interface to external media packages
Use of External Fluid Property Code in Modelica for Modelling of a Pre-combustion CO2 Capture Process Involving Multi-Component, Two-Phase Fluids
Full text linkDynamic modelling and validation of pre-combustion CO2 absorption based on a pilot plant at the Buggenum IGCC power station
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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
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
Dynamic modeling and validation of a conditioning and recovery unit for a CO2 capture power plant
No full textLAUREA SPECIALISTICAI cambiamenti climatici e le loro conseguenze non possono più essere ignorati. Al giorno d'oggi la maggior parte della produzione di energia avviene con emissione di gas serra, che secondo studi ormai accettati dalla maggior parte della comunità scientifica, causano un innalzamento della temperatura media sulla Terra.
Il carbone è una delle fonti energetiche più usate per la produzione di energia. Pertanto, numerosi studi e progetti sono in corso con l'obiettivo di sviluppare una tecnologia più pulita, che andrà a ridurre le emissioni di gas serra.
Una delle soluzioni proposte per diminuire l'impatto ambientale del carbone consiste nelle centrali di produzione IGCC (Integrated Gasification Combined Cycle), che possono essere sensibilmente più efficienti delle centrali a carbone tradizionali, e si prestano alla possibilità di implementare impianti di cattura e sequestro di anidride carbonica.
La compagnia energetica svedese Vattenfal ha avviato la costruzione una centrale IGCC di 120 MW, con impianti di cattura e sequestro di anidride carbonica. La progettazione di questo impianto si avvale degli studi effettuati in collaborazione con l'Università tecnologica di Delft.
Questa tesi si pone nell'ambito di questo progetto, con l'obiettivo i sviluppare una libreria per la simulazione dinamica di componenti con fluidi bifase e multicomponenti. Il presente lavoro può essere suddiviso in tre parti. Nella prima parte sono stati sviluppati componenti base, come connettori, valvole, sensori, e un modello di fluido che scorre in un tubo. Successivamente sono stati sviluppati due componenti più complessi, un air cooler e un condenser, presenti nella sezione di recovery dell'impianto. Questi due componenti sono stati poi validati in anello aperto e in anello chiuso. Nella terza e ultima parte, si è visto il controllo della conditioning section, valutando lo schema di controllo esistente e proponendo due alternativa, una il retroazione e una in feed-forward.
I modelli dei componenti sono stati creati utilizzando il linguaggio di programmazione object-oriented Modelica, e il tool di simulazione Dymola. Le proprietà termodinamiche dei fluidi sono state calcolate tramite FluidProp, una libreria di proprietà termofisiche dei fluidi sviluppato dall'Università di Delft.
I risultati sono stati qualitativamente soddisfacenti, ma il tempo di computazione necessario per effettuare le simulazioni è risultato eccessivo, e pertanto rappresenta un problema che rende ardua la simulazione di ampie sezioni dell'impianto.Climate change and its consequences can no longer be ignored. Most of the energy being generated today results in greenhouse gas emissions that, according to many scientific studies, cause an increase in the average earth surface temperature.
Coal is one of the resources most commonly used for the production of energy. Therefore, there are numerous studies and projects aimed at developing clean coal technologies, which will in consequence result in a reduction of greenhouse gas emissions. One of the proposed solutions to mitigate the environmental footprint of the energy industry comes in the form of Integrated Gasification Combined Cycle (IGCC) power plants, which can be significantly more efficient than conventional power plants and would allow to easily incorporate carbon capture and sequestration.
The Swedish energy company Vattenfall is investigating in cooperation with the Delft University of Technology the operation of IGCC power plants with CO2 capture units.
It is under the framework of this project that this thesis was written with the specific goal of developing a dynamic modelling library for components with two-phase multi-component fluids. Three parts can be distinguished in the body of this work. First, basic components were designed, including valves, pumps, sensors, and models of pipe flows. Then, an air-cooler and a condenser that are present in the recovery section of the CO2 capture plant were developed and validated in an open and closed loop. The final part included a proposal for a different control schemes for the conditioning section.
The Modelica language was used to model the components and the simulation tool employed was Dymola. Fluid properties were calculated using FluidProp, a library for thermophysical fluid properties developed at the Delft University of Technology.
The results were satisfactory in terms of quality, but the high computational times experienced presented a noteworthy problem that poses constrains when performing simulations of large sections of the plant
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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