641 research outputs found

    Influence of electrical potential on the crystallization and adhesion of potassium hydrogen tartrate crystals

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    Interfacial interactions between a hydroalcoholic solution of potassium hydrogen tartrate (KHT) and a stainless steel surface are studied, when an electrical potential is applied to the metal substrate. The capacitive domain of the metal–solution interface is determined by cyclic voltammetry. In order to study the influence of the potential on KHT nucleation and crystal adhesion, the solid–liquid interfacial energy is assessed from contact angle and capillary rise measurements. Experimentally, the contact angle between a NaF solution and a stainless steel vs. the potential has a parabolic behaviour. The metal topography has no apparent influence on physicochemical properties of the interface when ethanol is present in a KHT solution. The metal substrate promotes the formation of KHT crystals, which is improved by the application of an anodic potential. The adhesion of crystals becomes more effective when wires of 25 μm diameter are used in comparison with those of 250 μm

    Is scuba sampling a relevant method to study microhabitat in lakes? Examples and comparisons for three European species

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    We compared fish microhabitat use patterns in the littoral zone of a lake using a new direct method (i.e. Point Abundance Sampling by Scuba, PASS) and the widely used Point Abundance Sampling by Electrofishing technique (PASE). We collected microhabitat data for age 0+ roach (Rutilus rutilus L.), perch (Perca fluviatilis L.), and pike (Esox lucius L.). The two methods yelded different results for fish assemblage structure and microhabitat patterns. Using PASE, fish were mainly found in "shelter habitats" such as shallow waters and dense vegetation. It is likely that this behaviour is caused by the disturbance of the observer stamping around. Using PASS, fish escapement behaviour was rarely observed. Therefore, we concluded that this direct and non-destructive sampling technique is able to provide an accurate microhabitat estimation of a fish community and is assumed to be more suitable than PASE for fish habitat studies

    An Effective Semiclassical Approach to IR Spectroscopy

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    We present a novel approach to calculate molecular IR spectra based on semiclassical molecular dynamics. The main advance from a previous semiclassical method [M. Micciarelli, R. Conte, J. Suarez, M. Ceotto J. Chem. Phys. 149, 064115 (2018)] consists in the possibility to avoid state-to-state calculations making applications to systems characterized by sizable densities of vibrational states feasible. Furthermore, this new method accounts not only for positions and intensities of the several absorption bands which make up the IR spectrum, but also for their shapes. We show that accurate semiclassical IR spectra including quantum effects and anharmonicities for both frequencies and intensities can be obtained starting from semiclassical power spectra. The approach is first tested against the water molecule, and then applied to the 10-atom glycine aminoacid

    Dynamic Behaviour of a Continuous Heat Exchanger/Reactor after Flow Failure

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    The intensified technologies offer new prospects for the development of hazardous chemical syntheses in safer conditions: the idea is to reduce the reaction volume by increasing the thermal performances and preferring the continuous mode to the batch one. In particular, the Open Plate Reactor (OPR) type “reactor/ exchanger” also including a modular block structure, matches these characteristics perfectly. The aim of this paper is to study the OPR behaviour during a normal operation, that is to say, after a stoppage of the circulation of the cooling fluid. So, an experiment was carried out, taking the oxidation of sodium thiosulfate with hydrogen peroxide as an example. The results obtained, in particular with regard to the evolution of the temperature profiles of the reaction medium as a function of time along the apparatus, are compared with those predicted by a dynamic simulator of the OPR. So, the average heat transfer coefficient regarding the “utility” fluid is evaluated in conductive and natural convection modes, and then integrated in the simulator. The conclusion of this study is that, during a cooling failure, a heat transfer by natural convection would be added to the conduction, which contributes to the intrinsically safer character of the apparatus

    Evaluation of an intensified continuous heat-exchanger reactor for inherently safer characteristics

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    The present paper deals with the establishment of a new methodology in order to evaluate the inherently safer characteristics of a continuous intensified reactor in the case of an exothermic reaction. The transposition of the propionic anhydride esterification by 2-butanol into a new prototype of ‘‘heatexchanger/ reactor’’, called open plate reactor (OPR), designed by Alfa Laval Vicarb has been chosen as a case study. Previous studies have shown that this exothermic reaction is relatively simple to carry out in a homogeneous liquid phase, and a kinetic model is available. A dedicated software model is then used not only to assess the feasibility of the reaction in the ‘‘heat-exchanger/reactor’’ but also to estimate the temperature and concentration profiles during synthesis and to determine optimal operating conditions for safe control. Afterwards the reaction was performed in the reactor. Good agreement between experimental results and the simulation validates the model to describe the behavior of the process during standard runs. A hazard and operability study (HAZOP) was then applied to the intensified process in order to identify the potential hazards and to provide a number of runaway scenarios. Three of them are highlighted as the most dangerous: no utility flow, no reactant flows, both stop at the same time. The behavior of the process is simulated following the stoppage of both the process and utility fluid. The consequence on the evolution of temperature profiles is then estimated for a different hypothesis taking into account the thermal inertia of the OPR. This approach reveals an intrinsically safer behavior of the OPR

    Robot-aided cloth classification using depth information and CNNs

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    The final publication is available at link.springer.comWe present a system to deal with the problem of classifying garments from a pile of clothes. This system uses a robot arm to extract a garment and show it to a depth camera. Using only depth images of a partial view of the garment as input, a deep convolutional neural network has been trained to classify different types of garments. The robot can rotate the garment along the vertical axis in order to provide different views of the garment to enlarge the prediction confidence and avoid confusions. In addition to obtaining very high classification scores, compared to previous approaches to cloth classification that match the sensed data against a database, our system provides a fast and occlusion-robust solution to the problem.Peer ReviewedPostprint (author's final draft
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