查看更多>>摘要：With the growing scarcity of semiconducting devices stemming from volatile prices, shortened supplies, and increased demand that are attributed to the Covid-19 pandemic, manufacturers are looking for efficient ways to facilitate the production of nanoscale semiconducting devices. Thermal atomic layer etching (ALE) is a promising method that can overcome the obstacles encountered during the production of semiconducting devices via conventional approaches by delivering precise dosages of reagent to etch monolayers of substrate surface material in a cyclic operation. However, thermal ALE has not been extensively studied and characterized to become fully embraced by the semiconductor manufacturing industry. Recent work by our group has led to the development of a multiscale computational fluid dynamics modeling framework that was used to optimally design a desirable reactor configuration and operating conditions for the thermal ALE process. Despite this progress, additional research is needed to ensure that the film quality is maintained in the presence of operational disturbances. Therefore, the present work is focused on the development of a multivariable run-to-run (R~2R) control system to mitigate the impact of critical operational disturbances. It is demonstrated that the developed multivariable R~2R control system can efficiently overcome the negative effects of unknown disturbances that may impact film uniformity by regulating input variables within a minimal number of batch runs.
查看更多>>摘要：Currently, the increasingly severe pollution of organic wastewater from dyes and antibiotics has become one of the major causes for the deterioration of the water environment. In this work, nanosheets-MnxOy anchored biochar (MnxOy@BEP) obtained from the marine polluting algae Enteromorpha was synthesized by a hydrothermal method, which exhibited extraordinary adsorption performance for tetracycline (TC) and methyl blue (MB). Nanosheets-MnxOy was grown in situ on the surface of biochar by pyrolysis of KMnO4, and the MnxOy@BEP composite had a micronano hierarchical structure, a larger specific surface area (208.735 m~2 g(-1)) and more abundant active adsorption sites. Because of these characteristics, the MnxOy@BEP composite was endowed with excellent performance of organic pollutants in aqueous solution, which exhibited a high equilibrium adsorption capacity for TC (102.25 mg g(-1)) and MB (798.8 mg g(-1)), a rapid adsorption rate for MB (within 6 min) and selective adsorption properties at controllable pH. The experimental data of MB and TC was better fitted to the Langmuir isotherm model and pseudo-second-order kinetic model. Furthermore, the adsorption mechanism mainly involves electrostatic interactions, rr-rr interactions, hydrogen bonding, steric hindrance, etc. In addition, three cycles of adsorbent regeneration via 1.0 M NaOH solution displayed additional attractiveness. Therefore, the MnxOy @BEP composite material not only contributes to the management of Enteromorpha pollutants but can also be regarded as an extraordinary candidate for the removal of dye and antibiotic water.
Cesar Ramirez-MarquezAurora del Carmen Munguia-LopezMariano Martin
12页
查看更多>>摘要：The present work aims to obtain an optimal design of a multi-product solar grade silicon refinery under a systematic approach, considering different equity schemes and always seeking to maximize the profit of the facility. The proposed refinery is intensified to satisfy the demands with the use of minimum resources. Our motivation is to include a fairness approach in the design and optimization process which will help to diversify production at a lower cost and with a larger profit. Evaluation under equity approaches of intensified schemes is needed to identify how convenient it is to retain conventional schemes compared to intensified ones. Products of interest to be evaluated include solar grade silicon, tetraethoxysilane at various purities (98.5%, 99.0% and 99.5% mol), silane, di-chlorosilane, and monochlorosilane. The optimal profit allocation among these products is analyzed by evaluating different equity schemes (Social Welfare, Rawlsian Welfare and Nash approaches). Results show different income allocations under the equity schemes. These allocations are compared to the optimal design without equity schemes. Results show that the Nash scheme can provide fair trade-offs between the products (such as TEOS, SiH4, SiH2Cl2 and SiH3Cl) demanded by the market and the refinery's profit.
Antonio Garcia AStefan BerresElizabeth Mas-Hernandez
14页
查看更多>>摘要：A model for a continuous gravitational separation process of a liquid-liquid dispersion is presented, which is formulated as a population balance equation (PBE) that describes the coalescence and the hindered polydisperse sedimentation of droplets. This is important because this separation process is critical in the operation of many industries as discussed later. This study is based on previous findings by Garcia and Betancourt (2019) where a formulation for a batch process was presented. This analysis shows the improvements and differences between the model presented in this study and the formulation by Garcia and Betancourt (2019). The modeling framework comes from the Kynch's theory that has been employed to model solid particle sedimentation processes; however, in this case the principles are applied to an organic phase-aqueous phase liquid mixture. For the numerical solution of the model, the PBE is discretized in terms of droplet volume. Since the population balance model is subject to mass loss due to droplet coalescence, we propose a formula to compute the source term of the largest droplet class. Model validation used experimental data from literature for a continuous process. Numerical results explored the variation of parameters such as feed flowrate, feed oil volume fraction and the standard deviation of the initial and feed droplet volumes.
Vinay ChandrakerGanesh ParamasivanAbhilash J. Chandy
15页
查看更多>>摘要：The Sabatier micro-reactor for CO2 reduction through methanation, in manned mission applications, has gained a lot of interest due to higher yields of fuel and improved logistics. Three-dimensional (3D) computational fluid dynamics (CFD) calculations of flow, heat transfer and chemical reactions are performed here to understand and evaluate the potential of H2 and CO2 enrichment to increase the efficiency of the CO2 methanation in Sabatier microchannel reactors. The model is first validated by comparing calculations of the stoichiometrically-fueled reaction with previously conducted experiments at varying temperatures and pressures. A comprehensive set of studies at different H2 and CO2 enrichment levels, temperatures ranging from 200 to 400°C and gauge pressures of 1 bar and 5 bar is carried out. Results show that yields and conversions of almost 100% are achievable with the highest H2 enrichment levels at the highest temperature and pressure tested here, with a desirable control of CO emission.
Mohammad A. AbdelkareemBassel SoudanMohamed S. Mahmoud
21页
查看更多>>摘要：The demand for green energy is expanding, and it seems that hydrogen is the best option that can be produced and stored in large quantities. Hydrogen is a promising energy carrier that has various advantages compared to other energy sources. Accordingly, hydrogen is gaining significant attention as a green alternative for transportation, energy sector, and energy storage. The hydrogen-based energy system consists of four major stages: production, storage, safety, and utilization. Artificial neural networks (ANN) is effectively used in predicting optimal operational parameters for hydrogen production from different methods. This review summarizes the different hydrogen production methods. Then it discusses the progress done in the application of ANNs in hydrogen production technologies to maximize the hydrogen productivity and decreasing its cost. The coefficient of determination (R~2) and mean squared error (MSE) are used as performance criteria to evaluate the performance of the ANN applied in the different production methods. Future research recommendations and hot research topics are introduced as well.
查看更多>>摘要：Thermal-hydraulic performance investigation in a solar receiver channel equipped with a vortex flow generator, namely, flapped V-shaped baffle (FVB) on the absorber has been experimentally carried out. The purpose of using the square flaps on the V-baffle was to decline the pressure drag by directing the impact air to the absorber surface. The working fluid was air flowing into the uniform heat-fluxed channel at Reynolds number (Re) between 5300 and 23,600. The FVBs with 45°attack angle (a) were placed periodically on the absorber with the upstream V-apex arrangement. The FVB characteristics included three relative baffle-pitches (RP) and four flap angles (β)at one relative baffle height (RB=0.5) and flap length (b1/b = 0.4) were examined to obtain the optimum RP and β values. The present investigation has revealed that the FVB gives a considerable decrease in friction loss when compared with the solid V-baffle (β= 0) while the heat transfer rate reduces a little. The FVB with β = 45°, RP = 1.5 yields the greatest thermal performance around 2.5 as a result of the injecting air flows from the flap opening aside from the reduced friction loss. For the current experimental data, the Nusselt number and friction factor correlations were determined in the form of a function of the geometric FVB parameters and Re.
查看更多>>摘要：In the present work, hydrodynamics characteristics such as dispersed phase holdup (), Sauter mean diameter (d_(32)), drop size distribution (DSD), and continuous phase axial mixing was investigated in an asymmetric rotating impeller column (ARIC). Water - heavy normal paraffin (HNP) liquid system was used in ARIC to carry out the experiments. The effect of operating parameters such as impeller speed (N), superficial velocity of the continuous phase (Vc) was investigated. Experiments were performed at several dispersed to continuous phase (0/A) ratios. Volume displacement method and an image analysis technique were utilized to investigate the εD and d_(32), respectively. The pulse tracer technique was used to study the axial mixing in the continuous phase. The εD and d_(32) were strongly influenced by the impeller speed. More than 50% increase in εD was noticed when impeller speed increases from 100 to 350 rpm. The increase in dispersion coefficients (Dc) is observed with impeller speed. Whereas, it was noticed that O/A has a significant impact on Dc. About 80% decrease in Dc was observed when O/A increases from 5 to 25. The generalize equations have been developed for the prediction εD, d_(32), and Pec.
查看更多>>摘要：The surface modification of titanium-di-oxide semiconductor was done by adding V2O5 for enhanced visible light activity for generation of hydrogen. Hence, the main goal of the present work is to achieve the visible light activity using the synthesized photocatalyst for hydrogen production through water splitting. Hydrogen exists in nature and benefits the ecosystem by reducing the carbon emissions in the environment. Therefore, it is a self-motivated choice of researchers to produce hydrogen in large scale to save the environment from severe pollution hazards. Meanwhile, photocatalytic activity proves to be the excellent source for hydrogen generation. In this connection, the nanocomposite TiO2-V2O5 was synthesized by blending both sol-gel and thermal decomposition methods. The structural and morphological properties, surface area determination, absorption and band gap studies were carried out via various sophisticated instruments. The TiO2-V2O5 composite system exhibits lower band gap that favored the photocatalytic activity in promoting hydrogen production.
查看更多>>摘要：A novel catalyst was synthesized via excess solution impregnation (ESI) of Ru and Fe3O4 nanoparticles (NPs) on ceria-loaded mesoporous SiO2 and mesoporous SiO2 was synthesized using sol-gel method. Degradation of phenol and effluent containing phenol from resin industry was performed over Ru-Fe3O4/CeOx-SiO2 (Ce~(3+)/Ce~(4+), x = 1.64) catalyst in an autoclave reactor at 423 K and 14 bar oxygen pressure. Effective phenol degradation of 95% for the model aqueous solution of phenol and 92% for industrial effluent containing phenol were achieved when the both ruthenium and iron loadings were 0.25 wt% under optimized reaction conditions. The close contact between ruthenium and Fe3O4 nanoparticles facilitated the oxidation of phenol at very low temperature, whereas ceria NPs act as a promoter for oxidation reaction. The kinetics insights of oxidation reaction were studied and the catalysts were characterized thoroughly using BET, TPD, XRD, SEM, HR-TEM, ICP-AES, XPS and CO chemisorptions techniques. High surface area and large me-sopores of silica facilitated the fine dispersion of the active catalytic sites and oxygen vacancy as supported by the DFT study for catalytic activity. Optimal process conditions could render much higher phenol degradation efficacy in comparison with previous scientific investigations.
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