The permeability of low-permeability cores is generally measured using a pulse decay method. The core of low-permeability rocks, such as shale, often has a layered structure. The applicability of pulse decay testing for layered cores is not clear. In this study, the performance of the pulse decay method on layered cores was comprehensively investigated. Numerical simulations were conducted to investigate the influence of the interlayer permeability ratio, storativity ratio, layer thickness, interlayer location, and number of layers on the pulse decay pressure and pressure derivative curves, as well as the permeability obtained from pulse decay testing. The results revealed that the pressure curves of layered cores exhibit distinct differences from those of homogeneous cores if the upstream permeability is larger than the downstream one. The pressure derivative curve shows more inclined or horizontal straight-line segments than in the homogeneous case. The shapes of the pressure and pre... [more]

The increasing use of fossil fuels has raised concerns about rising greenhouse gas emissions. Carbon capture, utilization, and storage (CCUS) is one of the most important technologies for achieving net zero carbon emissions. In oil reservoirs, fully understanding their geological characteristics, fluid characteristics, and pressure distribution and injecting CO2 in a reasonable scheme, some remaining oil can be recovered to improve oil recovery and even obtain certain economic benefits. In this paper, we investigate the effect of CCUS implementation in low-permeability reservoirs from both technical and economic aspects. First, based on the parameters of a low-permeability reservoir, a numerical simulation model of a reservoir with gas injection in a multi-stage fractured horizontal well at the top of the reservoir and oil recovery in a multi-stage fractured horizontal well at the bottom is established. Next, four cases of continuous CO2 injection, intermittent CO2 injection, CO2 injec... [more]

The application of particle image velocimetry (PIV) technology for monitoring natural gas flow is a new method of flow measurement. Since the principle of this technology was proposed, there are still some potential issues. This article investigates the influence of a manifold structure on the measurement results of a PIV flowmeter. A comparison is performed between concentric and eccentric manifold structures, using a circular straight pipe as reference, in terms of the measurement error of the PIV flowmeter and the internal flow state of the natural gas. The results demonstrate that the manifold structure significantly affects the measurement reliability of the PIV flowmeter, especially the eccentric manifold structure. Under flow conditions ranging from 100 to 600 m3/h, the maximum measurement errors caused by the concentric and eccentric manifold structures are 2.49% and 3.05%, respectively, which show a noticeable increase compared to the maximum measurement error of 2.08% observe... [more]

In today’s world, a situational awareness of sustainability is becoming increasingly important. Leaving a better world for future generations is becoming the main interest of many studies. It also puts pressure on managers to change production methods in most industries. Reducing carbon emissions in industry today is crucial to saving our planet. Theoretical research and practical industry requirements diverge, even though numerous researchers have tackled various strategies to handle carbon emission problems. Therefore, this work considers the carbon emission problem of the furniture manufacturing industry in Hosur, Tamilnadu, India. The case study company has a manufacturing system that resembles a hybrid flow shop (HFS) environment. As the HFS scheduling problems are NP-hard in nature, exact solution techniques could not be used to solve the problems. Hence, a sequential hybrid optimization algorithm (SHOA) has been developed in this paper to minimize the carbon footprint. In the SH... [more]

Utilizing syngas components CO, CO2, and H2 to produce fatty acids and alcohols offers a sustainable approach for biofuels and chemicals, reducing the global carbon footprint. The development of robust strains, especially for higher alcohol titers in C4 and C6 compounds, and the creation of cost-effective media are crucial. This study compared syngas fermentation capabilities of three novel strains (Clostridium carboxidivorans P20, C. ljungdahlii P14, and C. muellerianum P21) with existing strains (C. ragsdalei P11 and C. carboxidivorans P7) in three medium formulations. Fermentations in 250-mL bottles were conducted at 37 °C using H2:CO2:CO (30:30:40) using P11, P7, and corn steep liquor (CSL) media. Results showed that P11 and CSL media facilitated higher cell mass, alcohol titer, and gas conversion compared to the P7 medium. Strains P7, P14, and P20 formed 1.4- to 4-fold more total alcohols in the CSL medium in comparison with the P7 medium. Further, strain P21 produced more butanol... [more]

The centrifugal force field in a hydrocyclone was affected by the concave-wall curvature radius R0, and the mechanism underlying droplet deformation was closely related to the mass transfer efficiency. Numerical simulation and experimental data were collected to reveal the deformation characteristics and mechanism of a single droplet crossing concave-wall jet. Normalized interfacial energy γ and stretching performance were provided to investigate the droplet deformation process. The results showed that the droplet was stretched along the streamwise direction and shrank along the spanwise direction in the concave-wall jet. The droplet interfacial energy and deformation were the largest when the droplet crossed the jet boundary at t = 0.20 s. The maximum γ value increased with the increase in R0 by 57.3% to 71.4%, and the distance between the droplet and concave wall increased with R0. The Q-criterion was exported to show the increase in the vortex strength with the decrease in R0 at the... [more]

Medicinal and aromatic plants (MAPs) are potential sources of natural polyphenols. Solid residues (SRs) from the essential oil (EO) industry are produced in significant volumes and may be used as natural sources of bioactive compounds. Therefore, this work was designed to examine the antioxidant and antibacterial characteristics of phenolic extracts obtained from SRs that have remained after EO distillation. SR extracts of Greek oregano, rosemary, spearmint, lemon balm, and Greek sage were assessed for their total phenolic content (TPC), antioxidant activity, and antimicrobial activity against Escherichia coli, Salmonella Typhimurium, Listeria monocytogenes, Staphylococcus aureus, Bacillus subtilis, Bacillus licheniformis, and Bacillus cereus in the concentration range of 500-3000 mg/L. The rosemary and Greek sage extracts exhibited the strongest antibacterial activities against all the Gram-positive species, while the spearmint and oregano extracts were less effective and only had an... [more]

Hydrogen energy, as a clean and green energy medium, is characterized by large capacity, extended lifespan, convenient storage, and seamless transmission. On the one hand, in the power system, hydrogen can be prepared by the electrolysis of water using the surplus power from intermittent new energy generation, such as photovoltaic and wind power, to increase the space for new energy consumption. On the other hand, it can be used to generate electricity from the chemical reaction between hydrogen and oxygen through the fuel cell and be used as a backup power source when there is a shortage of power supply. In this paper, based on the teaching practice, the conversion mechanism and coupling relationship between various forms of energy, such as photovoltaic energy, hydrogen energy, and electric energy, were deeply analyzed. Further, a hydrogen-electricity coupling digital simulation experimental system, including photovoltaic power generation, fuel cell, and electrolysis hydrogen system,... [more]

This paper presents a new grid-forming strategy for hybrid AC/DC microgrids using bidirectional virtual inertia support designed to address weak grid conditions. The stability of hybrid AC/DC microgrids heavily relies on the AC mains frequency and the DC-link voltage, and deviations in these factors can lead to undesirable outcomes such as load curtailments and power system congestions and blackouts. This paper introduces a unique approach that leverages bidirectional virtual inertia support to enhance the stability and reliability of hybrid AC/DC microgrids under weak grid conditions. The proposed strategy employs virtual inertia as a buffer to mitigate rapid changes in DC-link voltage and AC frequency, thereby enhancing system stability margins. This strategy significantly contributes to a more stable and reliable grid operation by reducing voltage and frequency fluctuations. A standard hybrid AC/DC microgrid configuration is used to implement the bidirectional virtual inertia suppor... [more]

In submerged arc welding, evaluating elemental transfer behaviors is critical for selecting and designing welding materials. Accurate assessment of O, Si, and Mn transfer behavior is essential for ensuring process quality, particularly when silicon-manganese fluxes are applied. Traditional quantification methods, however, focus only on chemical reactions in the weld pool zone, potentially overlooking the cross-zone elemental transfer behavior and leading to significant predictive inaccuracies. This study investigates the CaO-SiO2-MnO flux, a prevalent silicon-manganese flux, focusing on O, Si, and Mn, which exhibit notable transfer behaviors of O, Si, and Mn. By employing a multi-zone approach and integrating various scientific principles, the research aims to improve the accuracy of predicting elemental transfer behaviors and deepen the understanding of the metallurgical processes in submerged arc welding when silicon-manganese fluxes are employed. The study proposes strategic enhance... [more]

Battery voltage is a pivotal parameter for evaluating battery health and safety. The precise prediction of battery voltage and the implementation of anomaly detection are imperative for ensuring the secure and dependable operation of battery systems. Nevertheless, during the actual operation of electric vehicles, battery performance is subject to the influence of the vehicle's operational state and battery characteristic parameters, introducing challenges to safety alerts. In order to address these challenges and achieve precise battery voltage prediction, this paper comprehensively considers the battery characteristics and driving behavior of electric vehicles in both charging and operational states. Mathematical processing, including averaging and variance calculation, is applied to the battery characteristic parameter data and driving behavior data. By integrating historical voltage data and employing a modified gradient boosting decision tree algorithm (GBDT), a fast and accurate o... [more]

Melanoidins, as macromolecular heterogeneous organic polymers, are produced from the Maillard reaction between amino and carbonyl groups during the thermal hydrolysis pretreatment (THP) of sludge. The brown color and recalcitrance of melanoidins pose a serious threat to wastewater treatment systems, such as invalidating UV disinfection and decreasing the efficiency of anaerobic digestion; thus, they have gradually received much concern in recent years. However, currently the study on THP-origin melanoidins is limited by a lack of reliable extraction and quantification methods. This paper presents a comprehensive review of the physical, chemical, and biological properties of melanoidins from different sources to fill the research gap on THP-origin melanoidins. The adverse effects of melanoidins on the management of wastewater and sludge are discussed, and for the first time, special attention is paid to the potential environmental hazards of THP-origin melanoidins to natural ecosystems.... [more]

A depressant is essential to the effective flotation-based separation of ilmenite and forsterite, based on their comparable physicochemical characteristics. In this work, dextran sodium sulfate (DSS) was initially introduced as a depressant, to aid in the separation of ilmenite and forsterite. Comparing the DSS to conventional natural starch, the results indicate that the forsterite exerts a greater depression over the ilmenite. The difference in recovery of ilmenite and forsterite was 75.44% at 10 mg/L of DSS dosage. The DSS was chemisorbed strongly onto the forsterite surface via Mg active sites, whereas its interaction with the ilmenite surface via physisorption was weak, based on the XPS and molecular-dynamics-simulation analyses. The results of the AFM and QCM-D investigations showed that the DSS adsorption layer on the forsterite surface was larger than those on the ilmenite surface. Consequently, DSS may function as a depressant, to effectively separate forsterite from ilmenite... [more]

Lactic acid bacteria (LAB) constitute the microbial group most used as probiotics; however, many strains reduce their viability during their transit through the body. The objective of this study was to evaluate the effect of two microencapsulation techniques, as well as the incorporation of lactulose as a prebiotic and the use of chitosan coating on the microcapsules, on the viability of the Lactobacillus sp. strain FM4.C1.2. LAB were microencapsulated by extrusion or emulsion, using 2% sodium alginate as encapsulating matrix and lactulose (2 or 4%) as the prebiotic. The encapsulation efficiency was evaluated, and the capsules were measured for moisture and size. The encapsulation efficiency ranged between 80.64 and 99.32% for both techniques, with capsule sizes between 140.64 and 1465.65 µm and moisture contents from 88.23 to 98.04%. The microcapsules of some selected treatments (five) were later coated with chitosan and LAB survival was evaluated both in coated and uncoated microcaps... [more]

Reactivating oil and gas wells, increasing oil and gas production, and improving recovery provide more opportunities for energy supply especially in the extraction of unconventional oil and gas reservoirs. Due to changes caused by well completion and production in pore pressure around oil and gas wells, subsequently leading to changes in ground stress, and the presence of natural and induced fractures in the reservoir, the process of refracturing is highly complex. This complexity is particularly pronounced in shale oil reservoirs with developed weak layer structures. Through true triaxial hydraulic fracturing experiments on Jimsar shale and utilizing micro-CT to characterize fractures, this study investigates the mechanisms and patterns of refracturing. The research indicates: (1) natural fractures and the stress states in the rock are the primary influencing factors in the fracture propagation. Because natural fractures are widely developed in Jimsar shale, natural fractures are the... [more]

The construction and development of energy storage are crucial areas in the reform of China’s power system. However, one of the key issues hindering energy storage investments is the ambiguity of revenue sources and the inaccurate estimation of returns. In order to facilitate investors’ understanding of revenue sources and returns on investment of energy storage in the existing electricity market, this study has established multiple relevant revenue quantification models. The research methodology employed in this paper consists of three main components: Firstly, we established a revenue model and a cost model for energy storage participation in the electricity market. These models focus on arbitrage revenue, subsidy revenue, auxiliary services revenue, investment cost, operational and maintenance cost, and auxiliary service cost of energy storage. Subsequently, we utilized an enhanced Grey Wolf Optimizer algorithm to solve the optimization problem and maximize revenue, thus obtaining t... [more]

In this work, the internal flow behaviour and characteristic pressure fluctuations of an axial pump with varying water conditions are analysed. The impact of tip vortex flow on the pattern of turbulent flow is simulated numerically by the application of the CFD technique and experimentally using an acoustics analysis method. The numerical CFD data are verified with an experimental test model for accuracy and reliability. Based on the results, the difference in pressure in the internal flow and at the surfaces of the blade can be impacted through tip leakage vortex regions, which leads to changes in internal flow. Subsequently, the flow in the clearance and tip leakage vortex regions is changed. Moreover, the results reveal that the suction wall upstream is more unsteady near the surface due to more mixing, secondary flow, and tip leakage vortices. Pressure fluctuation occurs near the tip of the blade, caused by the increasing vortex flow velocity and hence raising the turbulent kinetic... [more]

Microcapsules have received considerable attention owing to their excellent self-healing properties, and many researchers have attempted to modify their microcapsules’ characteristics to meet the requirements of various applications. Owing to their excellent physical and chemical properties, nanomaterial-modified (nanomodified) microcapsules can be used to protect surface coatings and internal structures of cement-based materials. This paper summarizes the progress in theoretical research and practical application of nanomodified microcapsules in coatings and cement-based materials, focusing on preparation processes and performance enhancements. The advantages and necessity of using nanomaterials are highlighted by clarifying the effects of nanomodified microcapsules on the performances of coatings and cement-based materials. In addition, the bottlenecks in the application of nanomodified microcapsules to coatings and cement-based materials are comprehensively examined, and the challen... [more]

Liquid nitrogen (LN2) fracturing is a potential stimulation method in unconventional hydrocarbon recovery, showing its merits in being water free, creating low formation damage and being environmentally friendly. The microstructure evolution of rocks subjected to LN2 cooling is a fundamental concern for the engineering application of LN2 fracturing. In this paper, pore-scale imaging and characterization were performed on two rocks, i.e., tight sandstone and coal specimens subjected to LN2 cooling using computed tomography scanning. The digital core technique was employed to reconstruct the microstructures of rocks and give a quantitative analysis of the pore structure evolution of both dry and water-saturated rocks. The results indicate that LN2 cooling has a great effect on the pores’ morphology and their spatial distribution, leading to a great improvement in pore diameter and aspect ratio. When compared to the sandstone, coal is more sensitive to LN2 cooling and thermal stresses, ha... [more]

The aim of this study was to optimize parameters of microwave-assisted extraction (MAE) and accelerated solvent extraction (ASE) in terms of extraction temperature and time, microwave power and cycle numbers on the phenolic content of sea buckthorn leaves and berries, using 70% ethanol (v/v) as an extraction solvent. The characterization of phenolic composition in leaf and berry extracts obtained at optimal MAE and ASE conditions was performed with UPLC/ESI-MS2, while antioxidant activity was determined using the ORAC method. The optimal extraction conditions for MAE were 60 °C, 500 W and 15 min for leaves and 60 °C, 300 W, and 10 min for berries. The optimal extraction conditions for ASE from both leaves and berries were 120 °C, 15 min, and 3 cycles. Total phenolic content (TPC) in MAE and ASE extracts from leaves was similar to the TPC determined in extracts obtained by conventional extraction (60 °C/30 min); however, ASE contributed to the higher TPC of the berry extracts. The flavo... [more]

Superhydrophobic surfaces find extensive applications in various fields, including self-cleaning, liquid manipulation, anti-icing, and water harvesting. To achieve superhydrophobicity, the surfaces are designed with hierarchical nano- and/or microscale protrusions. These structures result in a static contact angle above 150° and a sliding/rolling-off angle below 10° when water droplets deposit on the surface. The combination of hierarchical structures and low-surface energy materials contributes to this unique liquid-repellent property. In addition to liquid repellency, the durability of these surfaces is crucial for practical applications, which has prompted the exploration of stretchable superhydrophobic surfaces as a viable solution. The flexibility of these surfaces means that they are effectively safeguarded against mechanical damage and can withstand daily wear and tear. Over the last decade, considerable research has been dedicated to developing stretchable superhydrophobic surf... [more]

The bottomhole pressure is one of the key parameters for oilfield development and decision-making. However, due to factors such as cost and equipment failure, bottomhole pressure data is often lacking. In this paper, we established a GA-XGBoost model to predict the bottomhole pressure in carbonate reservoirs. Firstly, a total of 413 datasets, including daily oil production, daily water production, daily gas production, daily liquid production, daily gas injection rate, gas−oil ratio, and bottomhole pressure, were collected from 14 wells through numerical simulation. The production data were then subjected to standardized preprocessing and dimensionality reduction using a principal component analysis. The data were then split into training, testing, and validation sets with a ratio of 7:2:1. A prediction model for the bottomhole pressure in carbonate reservoirs based on XGBoost was developed. The model parameters were optimized using a genetic algorithm, and the average adjusted R-squar... [more]

The thermal storage performance of shell and tube phase change heat storage units is greatly influenced by the thermophysical parameters of the phase change material (PCM). Therefore, we use numerical simulations to examine how the thermal storage capability of shell and tube phase change heat storage units is affected by thermophysical parameters such as specific heat capacity, thermal conductivity, and latent heat of phase change. The findings indicate that while the rate of temperature increase and the rate of the PCM melting both slow down as specific heat capacity increases, the overall heat storage increases. Within the specified range of parameters, the average rate of heat storage increases by approximately 4% for every 50% increase in specific heat capacity. The PCM’s rate of temperature rise slows down and its overall heat storage capacity rises throughout the middle stage of the phase change heat storage process as the latent heat of phase change grows. The average heat stor... [more]

Optimizing the structure of micromixers to improve the mixing efficiency is of great significance for chemical engineering and biology fields. In this study, an optimization of the microchannel in two liquids mixing is carried out based on computational fluid dynamics (CFD) and response surface methodology. Firstly, CFD simulations were performed to investigate the mixing flow field and mixing efficiency in the microchannel by considering different process and structure parameters (e.g., feed pressure p, microchannel width w). The response surface methodology was adopted to construct a fitting surface by CFD discrete working conditions. Then, an optimized microchannel width w was searched using the parallel particle swarm optimization (PPSO) algorithm from the response surface. Lastly, the searched optimum was validated by CFD simulation again, and the final result showed that the predicted mixing efficiency from the response surface model is well confirmed by CFD simulation. On averag... [more]

Previous studies have mainly focused on the source rocks of the 7th Member of Yanchang Formation (Chang 7 Member) in the Ordos Basin, with very few studies focusing on the extracts from the source rocks. These extracts have important guiding significance for studying the in situ conversion process of shale oil. Taking the shale source rock of the Chang 7 Member as an example, this paper selected the extract of shale source rock (i.e., retained oil), which has been less studied previously, as the sample to carry out the hydrocarbon-generating pyrolysis simulation experiment of a semi-open−semi-closed system. Seven groups of parallel simulation experiments were designed with a pressure of 20 MPa. The generated oil and gas were collected and quantified, and their geochemical characteristics were researched. In addition, the generated oil and gas were investigated from aspects of cumulative yield and net increased yield, and the chromatographic and mass spectral characteristics of the gene... [more]