scholarly journals Autonomous Reaction Network Exploration in Homogeneous and Heterogeneous Catalysis

Author(s):  
Miguel Steiner ◽  
Markus Reiher

AbstractAutonomous computations that rely on automated reaction network elucidation algorithms may pave the way to make computational catalysis on a par with experimental research in the field. Several advantages of this approach are key to catalysis: (i) automation allows one to consider orders of magnitude more structures in a systematic and open-ended fashion than what would be accessible by manual inspection. Eventually, full resolution in terms of structural varieties and conformations as well as with respect to the type and number of potentially important elementary reaction steps (including decomposition reactions that determine turnover numbers) may be achieved. (ii) Fast electronic structure methods with uncertainty quantification warrant high efficiency and reliability in order to not only deliver results quickly, but also to allow for predictive work. (iii) A high degree of autonomy reduces the amount of manual human work, processing errors, and human bias. Although being inherently unbiased, it is still steerable with respect to specific regions of an emerging network and with respect to the addition of new reactant species. This allows for a high fidelity of the formalization of some catalytic process and for surprising in silico discoveries. In this work, we first review the state of the art in computational catalysis to embed autonomous explorations into the general field from which it draws its ingredients. We then elaborate on the specific conceptual issues that arise in the context of autonomous computational procedures, some of which we discuss at an example catalytic system. Graphical Abstract

Nafta-Gaz ◽  
2020 ◽  
Vol 76 (11) ◽  
pp. 807-815
Author(s):  
Piotr Jakubowicz ◽  

Reservoir waters extracted during exploitation of crude oil and natural gas are a serious threat to the environment. The reason is high content of dissolved salts, mainly chlorides, as well as toxic components, such as: petroleum substances with aromatic hydrocarbons, and various chemicals applied during hydrocarbons production, e.g. corrosion, hydrates and paraffin inhibitors, surfactants, methanol etc. For this reason, the extracted reservoir water should be managed in a way that is least harmful to the environment. One of the methods of management that meets this requirement is injection of reservoir water into the absorptive horizon. In order to provide failure-free injection, with maximum use of the capabilities of an absorptive horizon, it is necessary to prepare the water properly by removing the components (solids, deposits and suspensions) that cause damage of the injection well. One of the most effective methods of water treatment is coagulation. Aluminum(III) sulfate(VI), commonly used in coagulation, requires a neutral pH of water. Exceeding this level results in rapid reduction in coagulation efficiency, and even in increase in the content of suspended solids in purified water. Extracted reservoir waters drastically change their properties from strongly reducing to oxidizing, due to methane removal after pressure reduction and oxygenation in contact with air. Moreover, while changing the electrochemical potential to positive, presence of iron and manganese ions in the water causes precipitation of oxides and hydroxides in the form of suspensions and the pH decreases due to their hydrolysis. Due to the dynamic course of these processes, as well as the additional acidification of water by addition of the coagulant (aluminum(III) sulfate(VI)), adjustment of the pH to the level appropriate for effective coagulation is often a serious problem. The solution could be application of properly selected modern coagulants of much greater efficiency, enabling a decrease of the agent dose as well as reduction of volume and improvement of the structure of post-coagulation sediments. Additionally, they are highly efficient in a wide range of water reactions. The article describes laboratory tests on a selected coagulant (polyaluminium chloride), which allow for determination of the range of deposit water reaction in which this agent can be used. For the tests, Flokor 1ASW was selected due to its high degree of hydrolysis and slight acidity (pH ~3.5) compared with other polyaluminium chlorides, which means low consumption of total alkalinity of purified water. The results obtained show a wide range of water reaction (pH from 8.0 to 4.0), in which the effectiveness of coagulant activity ensures the correct level of purification. In addition, the use of Flokor 1ASW with effective Stabpol K flocculant allows for production of big and quickly settled flocs. Post-coagulation sediments have much smaller volume than when using aluminum(III) sulfate(VI). The results of industrial tests, carried out in order to prepare reservoir water for injection, without pH correction, have been presented in the article. They confirmed the high efficiency of the selected chemicals.


2016 ◽  
Vol 7 (1) ◽  
pp. 10-19 ◽  
Author(s):  
B. Scheuchl

Polarimetric SAR data provide information about the scattering of the area observed. The availability of data stacks allows the identification of stable targets and subsequent scattering analysis with a high degree of confidence at full resolution. A novel approach to find and evaluate polarimetric persistent target is presented, that is an extension of well-established analysis methods for single scenes. The use of the Cloude-Pottier distributed target decomposition analysis applied on the temporal averages (as opposed to spatial averaging), combined with a Cameron point target analysis applied on each layer separately to select pixels only, provides an efficient scattering classification of polarimetric persistent point targets in the stack. This method can also be used to analyze targets identified through other means, albeit at a lower degree of confidence. The approach retains the full resolution of the data set, though temporal changes between acquisitions add additional complexity. Result interpretation is therefore performed under consideration of a set of boundary conditions. Results from the analysis of two polarimetric data stacks acquired by RADARSAT-2 are shown.


2020 ◽  
Author(s):  
Fatma Ben Salem

The chapter is devoted to the DTC and DTC-SVM position control approaches of induction motor (IM) allowing the movement of a photovoltaic panel according to the maximum sunshine position to extract a high efficiency of the system. The DTC is selected to full the application requirements, especially a maximum torque at standstill. This feature is necessary in order to guarantee a high degree of robustness of the maximum sunshine position tracking system against the high and sudden load torque variations characterized by the gusts of wind. The first step is devoted to a comparison study between three DTC strategies, dedicated to position control, such that: the basic DTC strategy, the DTC strategy with a look-up table including only active voltage vectors, and the DTC-SVM strategy with hysteresis controllers. Furthermore, the synthesis and the implementation of DTC-SVM approaches based on position control are treated. Within this context, the final part of the chapter proposes a comparison between three DTC-SVM approaches: (i) a DTC-SVM approach using PI controllers, (ii) a DTC-SVM approach using PI controllers with a nonlinear compensator, and (iii) a DTC-SVM approach using sliding mode controllers. In that case, an adaptation approach of parameter estimators are implemented in order to eliminate the effects of parameter variations and load disturbances. Simulations results show that the SM DTC-SVM approach gives the best results.


2021 ◽  
Vol 18 (3) ◽  
pp. 415-421
Author(s):  
A. A. Kasyanov

In a number of complex refractive cases, the achievement of an accurate refractive result cannot be guaranteed. Simultaneous implantation of a toric or multifocal IOL for the correction of complex ametropias may be accompanied by a significant deviation from the target refraction. The tactics of two-stage implantation with the usage of an additional Sulcoflex IOL for the final correction of astigmatism and possible residual spherical ametropia allows achieving emmetropia. In our study, this method was used in 15 patients with difficult refractive cases. Toric, multifocal, and multifocal toric Sulcoflex IOL were used. Implantation of all Sulcoflex modifications was performed through a 2.4 mm temporal incision using wound assisted technology. In cases of high degree hypermetropia, preventive iridectomy was performed using a 23G vitrectome. The target refraction was achieved in the entire observation group. In the postoperative period, no significant level of ophthalmic hypertension was registered. No cases of introlens opacification, iridocyclitis, or rotational instability were registered either.The method of two-stage IOL implantation allows achieving the target refraction in difficult refractive situations with almost guaranteed accuracy. The calculation method provides good predictability of the refractive result. This technology significantly expands the indications for intraocular correction using toric and multifocal IOL, as well as the limits of correction of high degree astigmatism. Our Sulcoflex IOL implantation experience has shown their high efficiency and safety.


Author(s):  
R. Mejri ◽  
Y. S. Peregudov ◽  
E. M. Gorbunova

Expediency of using natural glauconite material as a basis for the production of an environmentally friendly sorbent with hydrophobic and magnetic properties for liquidating oil and oil products spills mechanically and using a magnetic field has been substantiated and experimentally proved. Fractional, elemental and oxide compositions of the original mineral have been studied. The structure of glauconite fraction 0.045-0.1 mm has been investigated by transmission electron microscopy. It was found that the surface of the sample particles is heterogeneous with a large number of pores and cracks. Based on the experimental data, the optimal conditions for the production and use of powder and granular sorbents based on glauconite with specified properties were determined, at which a high degree of recovery (more than 90%) of oil with water and hard surfaces. The optimum temperature for obtaining a magnetic oil sorbent is 400 °C. The doses of stearic acid and iron (III) oxide were established at 5 wt. %, which provide hydrophobicity and magnetic properties to the synthesized sorbent. A high degree of oil (97%) and oil (98%) recovery when using a sorbent is achieved at a ratio of 1: 10 to sorbate. To eliminate oil and oil product spills, it is proposed to use granular ferromagnetic sorbents obtained by introducing carboxymethyl cellulose into the modified glauconite composition. oil and oil products granular sorbent increases in comparison with the original mineral by 1.2–2.2 times. Technological schemes for obtaining ferromagnetic hydrophobic and granular sorbents based on glauconite for collecting oil and oil products from water and solid surfaces have been developed. The synthesized sorbents are characterized by high efficiency, low cost, and environmental friendliness.


2013 ◽  
Vol 288 ◽  
pp. 84-87
Author(s):  
Dong Hai Su ◽  
Xiao Dong Tang

According to the needs of the electrohydraulic servo valve dynamic and static performance testing, designed an automated test system for the test of the static characteristics and dynamic characteristics test combinations together. Its advantage includes a stable system, a high degree of automation, simple operation, and high efficiency, full-featured.


2017 ◽  
Vol 38 (2) ◽  
pp. 249-264 ◽  
Author(s):  
Janusz A. Szpaczyński ◽  
Jeffrey A. White ◽  
Caroline L. Côté

AbstractThese studies examined the concept of concentration and purification of several types of wastewater by freezing and thawing. The experiments demonstrated that freezing of contaminated liquid contributed to concentration of contaminants in solution as well as significant concentration and agglomeration of solid particles. A high degree of purification was achieved for many parameters. The results of comparative laboratory tests for single and multiple freezing are presented. It was found that there was a higher degree of concentration of pollutants in wastewater frozen as man-made snow than in bulk ice. Furthermore, the hypothesis that long storage time of liquid as snow and sufficient temperature gradient metamorphism allows for high efficiency of the concentration process was confirmed. It was reported that the first 30% of the melted liquid volume contained over 90% of all impurities. It gives great opportunities to use this method to concentrate pollutants. The results revealed that the application of this process in full scale is possible. Significant agglomeration of solid particles was also noted. Tests with clay slurry showed that repeated freezing and thawing processes significantly improve the characteristics of slurry for sedimentation and filtration.


Nanophotonics ◽  
2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Shuo Du ◽  
Zhe Liu ◽  
Chi Sun ◽  
Wei Zhu ◽  
Guangzhou Geng ◽  
...  

Abstract As an inherent characteristic of light, polarization plays important roles in information storage, display and even encryption. Metasurfaces, composed of specifically designed subwavelength units in a two-dimensional plane, offer a great convenience for polarization manipulation, yet improving their integrability and broadband fidelity remain significant challenges. Here, based on the combination of various subwavelength cross-nanofins (CNs), a new type of metasurface for multichannel hybrid polarization distribution in near-field is proposed. Sub-wavelength CN units with various waveplate (WP) functionalities, such as frequency-division multiplexing WP, half-WP and quarter-WP are implemented with high efficiency in broadband. High-resolution grayscale image encryption, multi-image storage and rapid polarization detection are demonstrated by encoding the WP pixels into single, double and four channels, respectively. All these applications possess good fidelity in an ultrabroad wavelength band from 1.2 to 1.9 µm, and the high degree of integrability, easy fabrication and multifunction make the CN-shaped WP pixels a promising candidate in optical device miniaturization, quantum applications and imaging technologies.


Author(s):  
Yaroslav Ivanchuk

The high efficiency of the technological process of surface soil compaction using vibration and vibro-impact treatment hasbeen determined. High degree intensification of the soil compaction process is achieved by using original inertial vibratoryrammers with a hydro-pulse drive. A new mathematical model has been developed for the surface soil compaction processesstudy by the inertial vibratory rammers. Using numerical modeling, work dependencies are obtained to determine the mainoperating characteristics for the technological process of surface soil compaction by inertial vibratory rammers based on ahydro-impulse drive.


2015 ◽  
pp. 74-78 ◽  
Author(s):  
I. F. Khafizov ◽  
F. Sh. Khafizov ◽  
A. S. Kilinbaeva ◽  
O. D. Khalikova

Of the corrosion inhibitors currently used of greatest interest are imidazoline derivatives due to their high efficiency and processability. It is shown that the composition based on nitrogen containing organic compounds such as alkylimidazolines, isotrate, nonionic surfactants and solvent exhibits a high inhibiting properties in the reservoir water containing hydrogen sulfide and carbon dioxide. However, mineralized reservoir water with a low content of hydrogen sulfide or in its entire absence possesses a high degree of aggressiveness. The studies have shown that the compound obtained is ineffective as a corrosion inhibitor in this environment.


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