Nanostructured Carbon Nitrides for CO2 Capture and Conversion

Carbon nitride (CN), a 2D material composed of only carbon (C) and nitrogen (N), which are linked by strong covalent bonds, has been used as a metal-devoid and visible-light-active photocatalyst owing to its magnificent optoelectronic and physicochemical properties including suitable bandgap, adjustable energy-band positions, tailor-made surface functionalities, low cost, metal-free nature, and high thermal, chemical, and mechanical stabilities. CN-based materials possess a lot of advantages over conventional metal-based inorganic photocatalysts including ease of synthesis and processing, versatile functionalization or doping, flexibility for surface engineering, low cost, sustainability, and recyclability without any leaching of toxic metals from photocorrosion. Carbon nitrides and their hybrid materials have emerged as attractive candidates for CO₂ capture and its reduction into clean and green low-carbon fuels and valuable chemical feedstock by using sustainable and intermittent renewable energy sources of sunlight and electricity through the heterogeneous photo(electro)catalysis. Here, the latest research results in this field are summarized, including implementation of novel functionalized nanostructured CNs and their hybrid heterostructures in meeting the stringent requirements to raise the efficiency of the CO₂ reduction process by using state-of-the-art photocatalysis, electrocatalysis, photoelectrocatalysis, and feedstock reactions. The research in this field is primarily focused on advancement in the synthesis of nanostructured and functionalized CN-based hybrid heterostructured materials. More importantly, the recent past has seen a surge in studies focusing significantly on exploring the mechanism of their application perspectives, which include the behavior of the materials for the absorption of light, charge separation, and pathways for the transport of CO₂ during the reduction process.     

A Statistical Approach for Error Estimation in Adaptive Finite Element Method

Abstract

In the adaptive finite element method, the purpose is to create an optimal mesh with minimum degrees of freedom while producing an error value that is lower than the aim error. For this purpose, the estimation of discretization error at different points of the domain is required. In the Zienkiewicz and Zhu error estimator, the stress values of Gauss points is improved using superconvergent patch recovery and this improved solution is compared with the FEM solution to estimate the error. The regions with higher gradients of stress field produce larger values of estimated error. But the optimal mesh usually is attained in several steps of remeshing which leads to a high computational cost. In the present study, to track the regions with high gradients of stress, the statistical distribution of the stress values at Gauss points around a node is compared with the uniform distribution function, and the difference between these two distributions is taken as the error estimator. In this technique, at points for which the stress gradient is high, the mesh is automatically refined. The efficiency of this technique is that it finds the optimal mesh quickly in fewer steps. This advantage is demonstrated by several numerical examples.     

Optimization of Corynebacterium glutamicum Glutamic Acid Production by Response Surface Methodology

Response surface methodology (RSM) was used to evaluate the effects of fermentation parameters for glutamic acid (GA) production by Corynebacterium glutamicum CECT690 in submerged fermentation using palm date waste as substrate. To attain this purpose at the first stage, inoculum size, substrate concentration, penicillin concentration, phosphate concentration, and inoculum age were optimized for GA production. The next stage, the level of air flow rate in a 5-l fermenter (batch mode) which was run in optimized conditions was determined. The first stage gave the following results for the fermentation conditions optimized using RSM in 500-ml shake flasks: inoculum size 2% (v/v), substrate concentration 25% (w/v), penicillin concentration 1 U/ml, phosphate concentration 4 g/l, and inoculum age 10 h. Moreover, the maximum GA amount predicted by the model was 39.32 mg/ml. This was in agreement with the actual experimental value (36.64 mg/ml). In the second stage of the study, the amounts of GA were 118.75, 142.25, and 95.83 mg/ml in optimized conditions with the three levels of air flow rate of 0.6, 1.2, and 1.6 vvm, respectively. The present results demonstrate the potential of date waste juice as a substrate for producing GA by cultivation of C. glutamicum.     

An energy-saving opportunity in producing lubricating oil using mixed-solventin simulated Rotary Disc Contacting (RDC) extraction tower

Industrial processes are the most energy consuming processes in the world. Modification of these processes helps us with controlling the consumption of energy and minimizing energy loss. Changing raw materials is one of the ways through which we can optimize industrial processes. In this paper, a new solvent mixture (furfural + a co-solvent) was used for the extraction of lubricating base oil from lube-oil cut. It was found that the energy consumption of the new solvent mixture for obtaining a product with the same quality was much lower than the original solvent. By using this new solvent mixture, the operating temperature of the top of tower was reduced by 30 K. This leads to a high reduction in energy consumption in extraction of aromatics from lube oil. At our new extraction process by means of using new solvent mixture, the maximum energy saving was 38% per cubic meter of produced raffinate.     

Propagation of limited-diffraction X-waves in dissipative media

Diffractionless solutions of the wave equation in the form of X-waves have previously been obtained based on the inviscid form of the wave equation. A new general solution to the cylindrically symmetric wave equation for a medium with classical viscous losses is obtained. Particular solutions called dissipative Arcsin X-waves have been derived from this general solution. The properties of these waves are discussed for both infinite and finite size transducers and for different viscous liquids. To calculate the field produced by a finite transducer diameter, we have derived a dissipative form of the Rayleigh integral     

Comparison between the effects of cavitation induced by two different pressure-time shock waveform pulses

Acoustic cavitation generates very large localized pressures and temperatures, and thus provides a mechanism whereby physical and biological effects are produced in a high-intensity acoustic field. In this work, we studied the influence of the temporal form of a pressure pulse waveform on the destructive effects of transient cavitation. Two different shock pressure-time waveforms with nearly the same acoustic energy content were used. The first pressure waveform starts with a tensile wave followed by a compressive one, and the second pressure waveform starts with a compressive wave followed by a tensile one. These two pressure waveforms are called direct and inverse-mode pulses respectively. Based on the measurements presented in this work, we can state that, between the two types of shock pressure pulses studied, the direct-mode pulse amplifies systematically tile cavitation effect. This conclusion was achieved from a series of several quantitative and qualitative experiments: cavitation bubble collapse time, disintegration efficacy of plaster balls (a kidney stone-mimicking material), macroscopic study of lesions in agar gel and in vitro isolated rabbit liver tissue destruction. Considering these results and those obtained by other research groups, we can express that the temporal form of a shock pressure pulse has a major role on the cavitation effects.     

Electrochemical sensing platform based on modified graphite screen-printed electrode to determine isoproterenol in the presence of theophylline and acetaminophen

Journal of Materials Science: Materials in Electronics - This paper produced a novel and sensitive electrochemical sensor based on the MoS2 nanosheets modified graphite screen-printed electrode...     

Ultrasound-induced tissue ablation: studies on isolated, perfused porcine liver

Minimally invasive methods for the treatment of cancers, such as high-intensity focused ultrasound (HIFU) and high-energy shock waves (SW), have been proposed recently. Their feasibility for treatment of human cancer needs to be confirmed. A simplified model of isolated perfused pig liver that is close to the human liver in vivo has been proposed. The objective was to study the feasibility of deep focused tissue ablation with HIFU and SW in large organs approaching the size of the human liver. The model was demonstrated to be physiologically valid during the first 2 h of anoxic perfusion with a composite saline solution; arterial and portal pressure, enzymes, urea levels and bile secretion remained stable. It can simulate the major effects of perfusion and physical phenomena that occur in vivo during treatment. Histological analysis revealed no major changes. Previous results obtained in vivo in animal models at a depth of 2-3 cm were successfully reproduced and deeper lesion arrays at 4, 6, 8 and 9 cm from the surface were produced using the same principles. The depth of 9 cm from the liver surface is consistent with an extracorporeal treatment of most of the liver segments in man. Other applications of the model are proposed, particularly for the study of the role of interferences such as ribs and intestinal gas, blood perfusion and respiratory movements.     

Analysis of Natural Convection in Horizontal Concentric Annuli of Varying Inner Shape

An investigation is presented of free convection in horizontal concentric annuli of varying with inner shape where the inner and outer surfaces are kept at a constant temperature. The simulation is categorized into four groups based on the shape of the inner entity, which is either cylindrical, elliptical, square, or triangular. Flow and thermal fields are exhibited by means of streamlines and isotherms. Overall heat transfer correlations incorporating thermal radiation are established and presented in terms of the Nusselt number. It is observed that the surface radiation and presence of corners and larger top space enhances the heat transfer rate. As the reference temperature increases, surface radiation plays a more prominent role in the overall heat transfer performance.     

The Validation of Methods to Calculate Gas-Oil Relative Permeability Using Capillary Pressure Data from South Pars Reservoir

Abstract

Gas-oil relative permeability is the most important parameter in the simulation of fluid flow in the gas condensate reservoirs. Experimental measurements of relative permeability need core samples with regular shape, which is costly and time consuming. On the other hand, experimental data of relative permeability may also have significant error and uncertainty in many cases. One source of uncertainty is that the input to numerical simulator is uncertain and inaccurate; it may be reduced if the number of input parameters is decreased, especially if the parameters with the greatest uncertainty are avoided. It is possible to impose only capillary pressure data, because relative permeability can be predicted consistently using specific models. The present methods, which are based on capillary pressure, considered the porous media as a bundle of capillary tubes; they indeed are mercury flow paths that are filled during the mercury injection capillary pressure test at the certain value of capillary pressure. The authors applied the existing capillary models for relative permeability calculations to a gas condensate reservoir. The tested samples have a wide range of liquid permeability from less than 1 to 18 md. The results of this study show that the Purcell model has the best fit with experimental data for wetting phase (oil), and the differences between measured and model data were almost negligible. The predictions of nonwetting phase (gas) relative permeability were a good agreement with experimental data except for Purcell model. Results reveal that the relative permeability could be computed by using accurate capillary pressure data.