51 research outputs found

    Using Artificial Neural Networks to Determine Ontologies Most Relevant to Scientific Texts

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    This paper provides an insight into the possibility of how to find ontologies most relevant to scientific texts using artificial neural networks. The basic idea of the presented approach is to select a representative paragraph from a source text file, embed it to a vector space by a pre-trained fine-tuned transformer, and classify the embedded vector according to its relevance to a target ontology. We have considered different classifiers to categorize the output from the transformer, in particular random forest, support vector machine, multilayer perceptron, k-nearest neighbors, and Gaussian process classifiers. Their suitability has been evaluated in a use case with ontologies and scientific texts concerning catalysis research. From results we can say the worst results have random forest. The best results in this task brought support vector machine classifier

    MIXING AND HEAT TRANSFER IN HELICAL CAPILLARY FLOW REACTORS WITH ALTERNATING BENDS

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    ABSTRACT Capillary flow is often occurring in natural and technical systems. Due to small diameter channels, laminar flow is established, while heat transfer is high from large specific surface area. For chemical reactions, good mixing and a narrow residence time distribution are important for high selectivity and yield. To improve mixing and residence time distribution, several measures of bend flow, helical arrangements and curved capillaries are proposed in literature. This contribution describes the flow, residence time distribution, and its influence on chemical reactions in short helical, alternating reactor capillaries (SHARC). The influence of the number of bends between alternating coils on the residence time distribution is described for different capillary and coil diameter, coil length and flow rate in laminar regime. The residence time distribution is a good measure for axial mixing and dispersion, while the heat transfer is mainly affected by the flow rate. The SHARC device was built from polymer capillaries of fluorinated ethylene propylene (FEP, inner diameter of 0.38 and 0.75 mm) with high mechanical flexibility for bending and good chemical resistance. Despite of low heat conductivity of the wall material, volumetric heat transfer coefficients of more than 5 MW/m 3 K were measured in a water bath. A highly exothermic reaction with adiabatic temperature increase of more than 100 K could be operated without detecting reaction runaway

    From Lab to Pilot Scale: Commissioning of an Integrated Device for the Generation of Crystals

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    Fast time-to-market, increased efficiency, and flexibility of production processes are major motivators for the development of integrated, continuous apparatuses with short changeover times. Following this trend, the modular belt crystallizer was developed and characterized in lab scale with the model system sucrose-water. Based on the promising results, the plant concept was upscaled and commissioned in industrial environment. The results are presented within the scope of this work. Starting from small seed crystals in solution, it was possible to grow, separate, and dry product particles. Further, the conducted experiments demonstrated that it is feasible to transfer the results from laboratory to pilot scale, which in turn enables accelerated process design as well as development

    A Unified Research Data Infrastructure for Catalysis Research – Challenges and Concepts

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    Modern research methods produce large amounts of scientifically valuable data. Tools to process and analyze such data have advanced rapidly. Yet, access to large amounts of high‐quality data remains limited in many fields, including catalysis research. Implementing the concept of FAIR data (Findable, Accessible, Interoperable, Reusable) in the catalysis community would improve this situation dramatically. The German NFDI initiative (National Research Data Infrastructure) aims to create a unique research data infrastructure covering all scientific disciplines. One of the consortia, NFDI4Cat, proposes a concept that serves all aspects and fields of catalysis research. We present a perspective on the challenging path ahead. Starting out from the current state, research needs are identified. A vision for a integrating all research data along the catalysis value chain, from molecule to chemical process, is developed. Respective core development topics are discussed, including ontologies, metadata, required infrastructure, IP, and the embedding into research community. This Concept paper aims to inspire not only researchers in the catalysis field, but to spark similar efforts also in other disciplines and on an international level.DFG, 441926934, NFDI4Cat – NFDI für Wissenschaften mit Bezug zur Katalys

    Absorption and Chemisorption of Small Levitated Single Bubbles in Aqueous Solutions

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    The absorption and chemisorption of small bubbles with N2 or CO2 were investigated experimentally in aqueous and alkaline solutions. Different bubble sizes were studied ranging from 0.1 to 2.5 mm in alkaline concentrations of 0.1 mM to 1 M NaOH. The experiments were conducted in a device consisting of a converging microchannel with a down flowing liquid. Levitation positions of single bubbles were optically characterized. A correlation was developed for the drag force coefficient, CD, including wall effects based on the force equilibrium. A linear decrease of bubble diameters was identified with and without chemical reaction, which is referred to as a rigid bubble surface area. Measured Sherwood numbers agree well with the literature values for the investigated Reynolds number range

    Micro-computed tomography for the investigation of stationary liquid/liquid and liquid/gas interfaces in capillaries

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    For better understanding and optimization of multiphase flow in miniaturized devices, micro‐computed tomography (μCT) is a promising visualization tool, as it is nondestructive, three‐dimensional, and offers a high spatial resolution. Today, computed tomography (CT) is a standard imaging technique. However, using CT in microfluidics is still challenging, since X‐ray related artifacts, low phase contrast, and limited spatial resolution complicate the exact localization of interfaces. We apply μCT for the characterization of stationary interfaces in thin capillaries. The entire workflow for imaging stationary interfaces in capillaries, from image acquisition to the analysis of interfaces, is presented. Special emphasis is given to an in‐house developed segmentation routine. For demonstration purposes, contact angles of water, liquid polydimethylsiloxane, and air in FEP, glass, and PMMA are determined and the influence of gravity on interface formation is discussed. This work comprises the first steps for a systematic 3D investigation of multiphase flows in capillaries using μCT

    Cooling Crystallization with Complex Temperature Profiles on a Quasi-Continuous and Modular Plant

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    Volatile markets and increasing demands for quality and fast availability of specialty chemical products have motivated the rise of small-scale, integrated, and modular continuous processing plants. As a significant unit operation used for product isolation and purification, cooling crystallization is part of this trend. Here, the small-scale and integrated quasi-continuous filter belt crystallizer (QCFBC) combines cooling crystallization, solid-liquid separation, and drying on a single apparatus. This contribution shows the general working principle, different operation modes, and possibilities of temperature control with the modular setup. For precise temperature control in cooling crystallization, Peltier elements show promising results in a systematic study of different operation parameters. Sucrose/water was used as a model substance system. The results confirm that seed crystal properties are the most important parameter in crystallization processes. Additionally, an oscillating temperature profile has a narrowing effect on the crystal size distribution (CSD). The integrated, small-scale, and modular setup of the QCFBC offers high degrees of flexibility, process control, and adaptability to cope with future market demands

    Energy Optimization of Gas–Liquid Dispersion in Micronozzles Assisted by Design of Experiment

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    In recent years gas–liquid flow in microchannels has drawn much attention in the research fields of analytics and applications, such as in oxidations or hydrogenations. Since surface forces are increasingly important on the small scale, bubble coalescence is detrimental and leads to Taylor bubble flow in microchannels with low surface-to-volume ratio. To overcome this limitation, we have investigated the gas–liquid flow through micronozzles and, specifically, the bubble breakup behind the nozzle. Two different regimes of bubble breakup are identified, laminar and turbulent. Turbulent bubble breakup is characterized by small daughter bubbles and narrow daughter bubble size distribution. Thus, high interfacial area is generated for increased mass and heat transfer. However, turbulent breakup mechanism is observed at high flow rates and increased pressure drops; hence, large energy input into the system is essential. In this work Design of Experiment assisted evaluation of turbulent bubbly flow redispersion is carried out to investigate the effect and significance of the nozzle’s geometrical parameters regarding bubble breakup and pressure drop. Here, the hydraulic diameter and length of the nozzle show the largest impacts. Finally, factor optimization leads to an optimized nozzle geometry for bubble redispersion via a micronozzle regarding energy efficacy to attain a high interfacial area and surface-to-volume ratio with rather low energy input
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