1,720,971 research outputs found
Mathematical modeling of crosslinked polyacrylic acid based hydrogels: physical properties and drug delivery
Full text linkRecently, hydrogels have gained significant importance in different applications, such as tissue engineering and drug delivery. They are 3D structures of hydrophilic polymers held together through physical or chemical crosslinking. Important is their ability to swell in presence of solvents, forming elastic gels able to maintain their original shape. Furthermore, these scaffolds slowly degrade in the physiological environment, leading the growing tissue to replace the former filled site. In this work, hydrogels have been synthetized using branched polyacrylic acid (carbomer) cross-linked with an aliphatic polyetherdiamine (elastamine). In particular, we focused on the description of their equilibrium conditions in swollen state and the dynamic simulation of the swelling process. These hydrogels exhibited a peculiar swelling behaviour characterized by an overshoot of the volume increase before reaching the equilibrium. Notably, such behaviour was found at different pH values. In this manuscript, the swelling behaviour was studied by mathematical modelling. Moreover, the ability of these devices to release drugs was also examined through a literature model to understand the different operating transport mechanisms
The use of digital twins to overcome low-redundancy problems in process data reconciliation
No full textIn the digital era, data mining, analysis, and interpretation are of primary interest for industry 4.0. Processes provide a huge amount of dataset, which should be processed in the shortest possible time. Reliable process monitoring in real-time is of primary concern in the chemical industry due to its effect on the production costs as well as on decision making and performance, emissions, and safety monitoring. This can be achieved by exploiting the potential of simulations and digital twins to support data reconciliation (DR), gross error (GE) detection, and Dynamic Data Reconciliation (DDR). Data reconciliation is a numerical procedure used to correct measurements to fulfill material (i.e., mass flow rates and/or compositions) and energy balances, obtaining a coherent picture of the plant operating conditions. This chapter introduces a hardware and software platform for digital twin-aided data reconciliation and validation on a carbon capture industrial plant section
In Silico Study of Polymer Sheet Drying Process
No full textAbstract
In the last decades polymer sheets have been developed and used for various purposes, for example with electronic devices or solar cells. After polymer processing, they present a high residue of polymer solvent that should be reduced. Indeed, a high presence of solvent could affect their electrical properties or cause high levels of pollution. In addition, uncontrolled drying process can cause bubble formation with consequent film breakage. The aim of this work is to simplify the phenomena involved in the drying process in order to develop a mathematical model able to predict the time evolution of the composition and the mass of the polymer sheet. The model proposed here, therefore, is aimed at stimulating the industrial process and the results were verified against experimental data collected with cellulose acetate-based polymeric sheets. In addition, thanks to its simplicity and to the very low system requirements and central processing unit (CPU) time, our model gives immediate views of the system behavior.</jats:p
Process modeling and apparatus simulation for syngas production
No full textSyngas is a versatile mixture containing H2, CO, and CO2. It is at the base of the industrial production of bulk chemicals such as ammonia, urea, methanol, synthetic fuel, and their derivatives. Syngas production still exploits natural gas, coal, and fossil fuels; however, alternatives are appearing for the next future. For instance, biomasses, solid fuels such as plastics and solid urban wastes are becoming more and more appealing. For industrial purposes, it is fundamental to properly model both reforming and gasification/pyrolysis processes so that to reliably predict the syngas mixture composition and quality. To do this, modeling and process simulation play a key role. In this chapter, the importance of the adopted mathematical tool will be proven showing that an appropriate selection is needed. For instance, ad-hoc numerical tools are developed to properly model both kinetic reactions and transport phenomena (i.e., mass and heat transfer) involved in gasification/pyrolysis processes. While, concerning the natural gas reforming, authors provide some hints in the mathematical modeling for the reforming furnace providing both complex models and simplified ones. The last part of the present chapter is devoted to the process simulation. Some examples are proposed and details on the implementation are provided. Finally, the authors report the digital twin (i.e., dynamic simulation) of a steam reforming furnace for biogas reforming proving the importance of a robust control loop and providing a reliable start-up procedure for the furnace unit
Analogies between SARS-CoV-2 infection dynamics and batch chemical reactor behavior
Full text linkThe pandemic infection of SARS-CoV-2 presents analogies with the behavior of chemical reactors. Susceptible population (A), active infected population (B), recovered cases (C) and deaths (D) can be assumed to be molecules of chemical compounds and their dynamics seem well aligned with those of composition and conversions in chemical syntheses. Thanks to these analogies, it is possible to generate pandemic predictive models based on chemical and physical considerations and regress their kinetic parameters, either globally or locally, to predict the peak time, entity and end of the infection with certain reliability. These predictions can strongly support the emergency plans decision making process. The model predictions have been validated with data from Chinese provinces that already underwent complete infection dynamics. For all the other countries, the evolution is re-regressed and re-predicted every day, updating a pandemic prediction database on Politecnico di Milano's webpage based on the real-time available data
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
Impact of Kinetic Models on Methanol Synthesis Reactor Predictions: In Silico Assessment and Comparison with Industrial Data
Full text linkThe reactor is one of the most important equipment to be designed for optimal process operations. An appropriate reactor modeling leads to an efficient and optimal process conceptual design, simulation, and eventually construction. The key for success in this step is mainly related to kinetics. The present work is centered toward process simulation and aims at comparing three different kinetic models for methanol synthesis. The comparison shows how the refitted Graaf model, presented in a previous study, effectively predicts the performance of modern methanol synthesis loops. To pursue this objective, we simulated in Aspen HYSYS three methanol synthesis technologies (the most popular technologies in modern plants) and compared the results with industrial data. The proposed case study demonstrates that the refitted Graaf model is more accurate in output prediction than the well-established original Graaf and Vanden Bussche-Froment models, which are currently considered the industrial benchmark, thus showing how the refitted Graaf model is a potential candidate for future industrial applications
Implementing robust thermodynamic model for reliable bubble/dew problem solution in cryogenic distillation of air separation units
Full text linkHigh accuracy in Equations of State (EoSs) is becoming a more and more critical aspect for design and operational purposes in different areas of chemical and process engineering. It is well-known that improper predictions of mixture properties provide large deviations in process simulations, process control actions, estimation of operative conditions, assessment of performance indexes and optimal unit/process design. These deviations are strongly emphasized when typical operating conditions appear rather severe. One of the most challenging application sectors is represented by cryogenic separations and especially in case their nominal operating conditions approach the critical point. Air Separation Units (ASUs) are the ideal application field to demonstrate these criticisms. In addition, dedicated EoSs sometimes lacks in implementation details and thermodynamic parameters, making the reliability target impossible to be achieved. The present paper is aimed at bridging the current gaps in the implementation of Bender EoS for the reliable prediction of air mixture properties as well as the reliable simulation of ASU plants. The implementation requires the description of robust and efficient algorithms. At last, a quantitative comparison between the proposed approach and the existing solutions is provided
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
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