Valuable Theoretical Guidance Research Articles

On understanding the mechanical properties and damage behavior of Cf/SiC composites by indentation method

Carbon fiber reinforced silicon carbide ceramic matrix (Cf/SiC) composites have the advantages of high temperature resistance, wear resistance, low density, high hardness as well as specific strength. They have been applied extensively in hot-end components of aerospace and braking systems of trains. Nevertheless, grappling with the anisotropy, non-homogeneity, and weak interlayer bonding of Cf/SiC composites presents a major challenge for achieving efficient and low-damage processing. This paper is primarily intended to investigate comprehensively the mechanical properties and damage behavior of Cf/SiC composites by nanoindentation and Vickers indentation tests. The behaviors of indentation damage on the longitudinal section of fiber (LSF), the cross-section of fiber (CSF) and matrix under different loads and the deflection mechanism of matrix crack were analyzed. The findings reveal a pronounced anisotropy between the radial and axial orientations of the fiber, and plastic deformation exists in the matrix. Furthermore, the matrix has the largest hardness and elastic modulus, while the LSF displays the lowest values among the composites. The main forms of indentation damage on the LSF are fiber crack, fiber peel off, fiber cocked up and squamous crack. The main manifestations of indentation damage on CSF are fiber crushing and fiber debonding, with the total surface damage area being comparatively limited. The fiber orientation and interface are influential factors in the crack propagation path of matrix. Notably, the fibers effectively inhibit the crack propagation of the matrix. This investigation provides valuable theoretical guidance for the formation mechanism and suppression strategy of machining damage in Cf/SiC composites.

Imbibition behavior of water on coal surface and the impact of surfactant

Coal seam water injection is vital in mitigating dust pollution in coal mining operations. To investigate water imbibition and adsorption behavior on the coal surface following injection into coal seams, as well as the impact of surfactants, coal particles with sizes of 6–8 mm, 3–5 mm, and 0.4–0.85 mm were selected from the Dongtan Coal Mine in Shandong Province, China. Coal particle imbibition experiments were designed for coal particles at varying surfactant concentrations and temperatures, and molecular simulation was employed to examine the micro adsorption behavior of water within coal rock pores. The findings indicate that smaller coal particles exhibit significantly higher water absorption capacity compared to larger particles when ample water supply is present. This suggests that coal pore water absorption is inherently limited. Moreover, elevated formation temperatures hinder the wetting process of water injection. Importantly, introducing surfactants leads to the blockage of coal fractures, constriction of fracture channels, and restriction of the effective wetting range of coal seam water. Furthermore, the influence of sodium dodecyl sulfate is greater than that of cetyltrimethylammonium bromide. In low-temperature environments, surfactants exert a more prominent inhibitory effect on water injection wetting. These research findings provide valuable theoretical guidance for coal seam dust prevention efforts and water injection technology.

Theoretical Study on the Influence of the Anharmonic Effect on the Ionic Conductivity and Thermal Stability of 8 mol% Yttria-Stabilized Zirconia Solid Electrolyte Material.

YSZ is a promising material for resistive memory devices due to its high concentration of oxygen vacancies, which provide the high anion migration rates crucial for the manifestation of resistance switching in metal oxides. Therefore, investigating the ionic conductivity of YSZ is an important issue. The ionic conductivity and thermal stability of 8 mol% YSZ were studied using the theories and methods of solid-state physics and physical chemistry. The impact of anomalous atomic vibrations on the material was also explored, and the variation in the ion vibration frequency, electrical conductivity, and thermal stability coefficient of electrical conductivity with temperature was obtained. The results show that the ion conductivity of an 8 mol% YSZ solid electrolyte increases nonlinearly with temperature, with a smaller increase at lower temperatures and a larger increase at higher temperatures. Considering the anharmonic effect of ion vibrations, the electrolyte conductivity is higher than the result of the harmonic approximation, and the anharmonic effect becomes more significant at higher temperatures. Our research fills the gap in the current literature regarding the theoretical non-harmonic exploration of the ion conductivity and thermal stability factor of YSZ solid electrolytes. These results provide valuable theoretical guidance for the development and application of high-performance YSZ resistive memory devices in high-temperature environments.

Fouling mechanism and effective cleaning strategies for vacuum membrane distillation in brackish water treatment

Membrane scaling is an enormous challenge in the desalination of hypersaline water using membrane distillation (MD). In this study, vacuum membrane distillation (VMD) was employed for brackish water treatment, with an emphasis on scaling mechanisms and mitigation strategies. Four methods, including deionized water, hydrochloric acid, and acetic acid, ultrasonication, were utilized for membrane cleaning. The cleaning efficiency was assessed through a comprehensive analysis of residual foulant layers. It was determined that mineral scaling constituted the primary fouling mechanism, and a minor amount of organic fouling was present at the interface between scaling-scaling and scale-membrane. Calcium and magnesium carbonate were the primary scaling components observed in brackish water desalination, appearing as needle-like and block crystals. Notably, CaCO3 predominantly existed as the aragonite crystal structure. Ultrasonication and deionized water demonstrated limited effectiveness due to the alkaline nature of the scaling. Conversely, the application of dynamic hydrochloric acid and acetic acid treatments resulted in a significant reduction in scaling, with acetic acid demonstrating superior efficacy in removing carbonate scaling. The results presented in this study can provide valuable theoretical guidance for the treatment of brackish water using membrane desalination techniques.

CiteSpace-Based Visualization Analysis on the Trombe Wall in Solar Buildings

The Trombe Wall is the main solar collector component in solar buildings, and it has attracted much attention due to its ability to maximize solar energy utilization and reduce buildings’ energy consumption. Numerous research studies have been conducted. Bibliometrics and CiteSpace visual analysis software are used in this paper to summarize and find that the research process for the Trombe Wall can be divided into three periods: the preliminary development period, the ice-breaking period, and the comprehensive development period. Then, we visually analyze information, such as countries, institutions, authors, journals, references, and keywords, from 537 selected articles in the Web of Science (WOS) database during the period 1991–2023. The results show that current research in this area primarily focuses on “thermal comfort”, “BLC”, “PCM-Trombe Wall”, “PV-Trombe Wall”, and “BIPV system”. On this basis, potential development trends in this field and some future research issues that need to be addressed are proposed. Furthermore, the study identifies potential development trends in this area. By providing a comprehensive understanding of the current research status, research frontiers, research hotspots, and research trends in this area, this study provides valuable theoretical guidance for subsequent research.

Water Vapor Adsorption on Desiccant Materials for Rotary Desiccant Air Conditioning Systems

In order to determine the water vapor adsorption performance of a rotary desiccant-based air conditioning system, the behavior of water adsorption on cylindrical pores of different sizes was studied by using classical density functional theory (CDFT) based on perturbated chain statistical associating fluid theory (PC-SAFT). Firstly, the structural parameters of the desiccant material were characterized by scanning electron microscopy (SEM), X-ray Energy Dispersive Spectrum (EDS), and N2 adsorption/desorption isotherms, as well as adsorption equilibrium measurements of water vapor at temperature range 293–308 K. Secondly, the potential energy equation of water molecules in cylindrical pores was determined, and contribution of various terms of PC-SAFT for simulating fluid in cylindrical pores were established. Finally, the pore size distribution (PSD) of the desiccant materials is determined by the PC-SAFT kernel. Moreover, water vapor condensation was investigated with the PC-SAFT model in micropores. The results indicate that the rotary desiccant materials have a large number of micropores with a volume of 0.3669 cm3/g and the amount of water adsorption is about 0.285 g/g. The condensation pressure and the pore width corresponding to the saturated pressure P0 grow with an increase in the temperature, signifying that adjusting the PSD of the material has a significant effect on improving the dehumidification performance. The research concludes that the PSD range of the oxide cylindrical pore between 1.09 and 1.53 nm is particularly beneficial for dehumidification. This study provides valuable theoretical guidance for optimizing dehumidification materials.

Epidemic monitoring in real-time based on dynamic grid search and Monte Carlo numerical simulation algorithm.

Building upon the foundational principles of the grid search algorithm and Monte Carlo numerical simulation, this article introduces an innovative epidemic monitoring and prevention plan. The plan offers the capability to accurately identify the sources of infectious diseases and predict the final scale and duration of the epidemic. The proposed plan is implemented in schools and society, utilizing computer simulation analysis. Through this analysis, the plan enables precise localization of infection sources for various demographic groups, with an error rate of less than 3%. Additionally, the plan allows for the estimation of the epidemic cycle duration, which typically spans around 14 days. Notably, higher population density enhances fault tolerance and prediction accuracy, resulting in smaller errors and more reliable simulation outcomes. Overall, this study provides highly valuable theoretical guidance for effective epidemic prevention and control efforts.

The Influence of High-Pressure Water Jet Cutting Parameters on the Relief of Pressure around the Coal Slot

This research aims to investigate the impact of high-pressure water jet cutting parameters on pressure alleviation around the coal slot. A numerical model of high-pressure water jet cutting coal was developed using FLAC3D software, allowing for a detailed study of how each cutting parameter affects the pressure relief effect of the slot. The key findings are as follows: as the water jet pressure increases, the plastic area of the coal body around the kerf expands, although the rate of increase diminishes, with the optimal water jet pressure being 30 Mpa. The results suggest that hydraulic slotting measures are particularly beneficial for outburst prevention in high in situ stress coal seams. The pressure relief range exponentially grows with an increase in the kerf depth, signifying that enhancing the kerf depth has a notable effect on improving the hydraulic kerf pressure relief. As the slit width increases, the volume of the slit enlarges, leading to a significant rise in the pressure relief range of the surrounding coal body. Given that an increase in the slit width necessitates an increase in the nozzle outlet diameter and slotting time, the optimal slit width is determined to be 0.2 m. The research concludes that the optimal hydraulic slit spacing is 3 m. This study offers valuable theoretical guidance for high-pressure water jet slotting.

Effect of R-SO2-R′ ligands on the gold-based catalysts for acetylene hydrochlorination: A DFT study

Gold-based mercury-free catalysts have great potential in the industrial production of vinyl chloride. In order to further understand the factors affecting the catalytic activity, the catalytic reaction mechanisms of five kinds of sulfur-containing ligand gold-based catalysts are studied by DFT calculation at the PBE0/def2-TZVP level, and dispersion-corrected DFT-D3 is performed. The results show that the rate control step in the reaction path is the transfer of proton hydrogen. With the increase of Mulliken charges of Au and S atoms in the catalyst, the energy barrier of acetylene hydrochlorination decreases. The catalyst formed by methanesulfonic acid and AuCl3 has the lowest energy barrier of acetylene hydrochlorination (23.18 kcal/mol). Compared to AuCl3 catalyst, adding ligands can significantly reduce the products desorption energy. When the ligand has an electron-withdrawing group, the corresponding acetylene self-polymerization barrier is lower. These results provide valuable theoretical guidance for preparation of efficient sulfur-containing ligand gold-based catalysts in future.

Pulse effects on proppant transport and dune shape in vertical fracture applied in coalbed methane mining engineering during the pulse hydraulic fracturing

Proppant transport plays a very important role in the pulse hydraulic fracturing (PHF). However, it is unclear that the pulse effect mechanism and regularity on the proppant migration in fracture. This study combined PHF and proppant migration for the first time to reveal the pulse effects on the migration and distribution of proppant. This work was conducted based on the Eulerian-Eulerian two-phase model and computational fluid dynamics method. Firstly, the simulations were validated by two typical experiments. Then, the pulse injections of slurry were carried out in a vertical fracture. Last, the influences of pulse shape, amplitude and period were discussed in detail. The results show that the square pulse can decrease the dune deposition height in the near region of fracture, and the decrease has a positive correlation with the pulse period, where the maximum decrease is up to 22.6%. It's found that the square pulse can increase the dune deposition height in the middle and far regions of fracture, and the increments have positive correlation with the pulse period, where the maximum increments are 47.7% and 61.5%, respectively. The present results indicate that the square pulse injection can extend the migration range of proppant. The extended-range effect has a positive association with the pulse period. Besides, results show that the extended-range effect is apparent only when the pulse amplitude is larger than 0.3 m/s. Compared to the sine pulse injection, the square pulse injection provides better extended-range effect. The present findings can provide valuable theoretical guidance for the PHF design and efficient exploitation of coalbed methane.

Dynamic simulation of a motor longitudinally mounted on a centralized electric drive systems for pure electric vehicles under torque ripple and transmission error excitations.

The dynamic characteristics of electric drive systems are crucial in electric vehicles. Based on the dynamic finite element method and previous studies, this study proposes and analyzes a new mathematical model for a motor longitudinally mounted on a centralized electric drive system of a pure electric vehicle. First, we analyze the largest torque ripple of a fractional slot concentrated winding inner-mounted permanent magnet synchronous motor designed for commercial electric vehicles. This torque ripple is identified as one of the excitations influencing the dynamic performance of the electric drive system. Second, a new dynamic mathematical model for the electric drive system is established. Third, we investigate the linear vibration responses of the system subject to torque ripple and transmission error. Finally, the relationships between critical motor parameters and dynamic mesh force are revealed. The results demonstrate that the proposed theoretical method can effectively determine the dynamic characteristics of the electric drive system, thereby providing valuable theoretical guidance for the design and optimization of the motor and electric drive system.

A nonlinear rheological shear constitutive model of bolted joints considering initial damage and damage evolution

Understanding the shear mechanics mechanism of bolted joints is of great significance for predicting and preventing geological disasters. Most current studies seldom consider the rheological effects of bolted joints. In this paper, a comprehensive rheological constitutive model is proposed, accounting for initial damage and damage evolution across different rheological stages and bolt characteristics. The model incorporates an elastoplastic Hooke body for instantaneous deformation, parametric nonlinear Kelvin and viscous models for attenuation and steady creep stages, and a visco-plastic model based on time-dependent shear strength for accelerated creep stage. Additionally, a bolt-rock cooperative deformation model is introduced, considering the evolution of the bolt's elastic modulus. The resulting elasto-viscoplastic constitutive model effectively describes the shear rheological behavior of bolted joints, with its validity and superiority demonstrated through comparisons with shear creep tests and the Maxwell model. This research aims to provide valuable theoretical guidance for the construction and reinforcement of rock mass engineering projects.

A study on the effects of college students' knowledge-sharing behavior on group performance and individual social status.

Universities, as typical knowledge-based organizations, engage in various knowledge management activities, including knowledge acquisition, storage, application, and innovation. This research focuses on applying organizational knowledge management principles to college student groups in universities, aiming to explore the current state of knowledge-sharing behaviors within these groups and investigate the relationship between group performance, individual social status, and knowledge-sharing behaviors. A sample of 497 college students from six universities in China was randomly selected, and an econometric analysis using structural equation modeling was conducted with SPSS21.0 and AMOS21.0 to examine their knowledge-sharing behaviors, individual social status, and group performance. The findings reveal that individual knowledge-sharing behavior significantly influences the knowledge sharing behavior of others and the recognition received by the sharer. Moreover, the knowledge-sharing behavior of others positively contributes to group performance, while recognition from others enhances the social status of the sharer. Furthermore, the knowledge-sharing behaviors of others mediate the relationship between individual knowledge-sharing behaviors and group performance, while others' recognition of the sharer mediates the relationship between individual knowledge-sharing behaviors and the sharer's social status. This study provides valuable theoretical guidance for organizational knowledge management and the development of college students' learning abilities, establishing a crucial foundation for comprehensive, scientific, and standardized student management. Overall, this research contributes to understanding the dynamics of knowledge sharing among college students and highlights the importance of incorporating knowledge management principles in educational settings. The findings underscore the positive impact of knowledge sharing on group performance and individual social status, emphasizing the need for effective knowledge sharing practices to enhance student management in higher education institutions.

A novel arc-cantilevers F-P filter with low stress applicated in infrared spectral integrated photodetector chip

Infrared spectral detector technology represents a novel detection strategy that combines spatial information with infrared spectral data, expanding the traditional light-intensity image detection in the spatial dimensions (x, y) to include the spectral dimension (x, y, λ). Conventional spectral detection methods often involve system integration grating on the spectrometer, which suffers from drawbacks such as large size and high-power consumption. To overcome these limitations and enable miniaturization application, it is necessary to investigate the development of spectral integrated infrared detector chips, which include a crucial component known as a tunable filter. Our previous experimental work identified an issue with the Fabry-Perot (F-P) filter based on the conventional cantilever beam structure, where excessive surface stress caused tilting of the bridge deck, adversely affecting the filtering quality. In this study, a new tunable F-P cavity filter structure with low surface stress by arc cantilevers was proposed. The Von Mises stress distribution of the bridge surface was analyzed, revealing a 50% reduction in surface stress compared to the traditional right-angle structure. The newly proposed structure demonstrates excellent performance in terms of tunable infrared transmission filtering spectrum. The tunable wavelength range covers 3-5 μm, and the structure achieves a transmission value of 70%. This work establishes valuable theoretical guidance for the fabrication of cantilever microbridge filters in experimental work and their potential future applications in spectrally integrated detector chips.

Characterizing thermo-hydraulic behaviors of seasonally frozen loess via a combined opto-electronic sensing system: Field monitoring and assessment

Frost damage in mid-latitude loess regions is mainly caused by the coupled soil water and heat transfer during freezing-thawing (FT) processes. In this paper, to better understand the thermo-hydraulic (TH) behaviors of seasonally frozen loess, field monitoring and assessment were performed on the Loess Plateau, China with a quasi-distributed opto-electronic sensing system. This system successfully captured the spatiotemporal variations in multivariables of seasonally frozen soil in near real-time, including in-situ soil temperature, unfrozen water content, and ice content. The monitoring datasets collected during the 2020/2021 winter offer unique insight into the TH behaviors of freezing point (FP) depression, in-situ soil-freezing characteristic curve (SFCC), and cryosuction. The findings highlight the importance of acquiring SFCCs under natural boundary conditions and confirm the applicability of laboratory-obtained FP in determining in-situ soil freezing depth. Furthermore, the study reveals that soil matric suction, considering the presence of ice, is the primary driving force of water migration during FT. Finally, errors in field monitoring are discussed, which arise from two aspects: the special features of loess and imperfections in monitoring schemes. This assessment of the coupled TH responses to climate changes in loess offers valuable theoretical guidance for optimizing engineering construction schemes and mitigating geohazards in mid-latitude loess regions.

A Systematic Review of the Organizational Inertia Literature and Future Outlook

This paper aims to provide a comprehensive review of organizational inertia, including its influencing factors, practical implications, future trends, and development directions. A systematic literature review is employed to analyze and synthesize the existing body of knowledge on organizational inertia. The review highlights the complexity and multifaceted nature of organizational inertia, its impact on change and adaptation, and potential strategies for overcoming it. This study offers a holistic perspective on organizational inertia by integrating findings from various disciplines and addressing limitations in the current literature. Current research on organizational inertia faces limitations in research methods, content, application scenarios, and conceptual scope, necessitating future exploration in these areas. The findings of this review provide valuable theoretical and practical guidance for organizational reform and development, aiding organizations in overcoming inertia and fostering innovation.

Theoretical Investigation of Ru(II) Complexes with Long Lifetime and a Large Two-Photon Absorption Cross-Section in Photodynamic Therapy.

Two-photon photodynamic therapy (TP-PDT), as a new method for cancer, has shown unique advantages in tumors. A low two-photon absorption cross-section (δ) in the biologic spectral window and a short triplet state lifetime are the important issues faced by the current photosensitizers (PSs) in TP-PDT. In this paper, the photophysical properties of a series of Ru(II) complexes were studied by density functional theory and time-dependent density functional theory methods. The electronic structure, one- and two-photon absorption properties, type I/II mechanisms, triplet state lifetime, and solvation free energy were calculated. The results showed that the substitution of methoxyls by pyrene groups greatly improved the lifetime of the complex. Furthermore, the addition of acetylenyl groups subtly enhanced δ. Overall, complex 3b possess a large δ(1376 GM), a long lifetime (136 μs), and better solvation free energy. It is hoped that it can provide valuable theoretical guidance for the design and synthesis of efficient two-photon PSs in the experiment.

DFT+U study on the magnetic properties of 3d transition metal doped β borophene

Two-dimensional materials with strong magnetism have attracted extensive attention for their potential application in spintronics. Recently, thess β 12 borophene with stable structure has been successfully synthesized experimentally. However, the β 12 borophene with non-magnetism limits its application in spintronics. The structural, electronic and magnetic properties of pristine and 3d transition metal (TM)-doped β 12 borophene monolayers are studied by means of first-principles calculations based on the GGA + U approach. Our results indicate that the doping of the Ti-, V-, Cr-, Mn-, Fe-, Co- and Ni atoms can induce magnetism in β 12 borophene and comparatively large magnetism can be obtained in Cr-, Mn-, Fe- and Co-doped systems. The Cr-, Mn- and Co-doped β 12 borophene exhibit antiferromagnetic ground states, while ferromagnetic ground state occurs in the Fe-doped system. Particularly, the spin density distribution of the Cr- and Mn-doped β 12 borophene is highly localized, which have a promise for application in magnetic storage devices. Our work provides a valuable theoretical guidance for the further experimental study and application of borophene materials in spintronics. • The doping of the Ti-, V-, Cr-, Mn-, Fe-, Co- and Ni atoms can induce magnetism in β 12 borophene and comparatively large magnetism can be obtained in Cr-, Mn-, Fe- and Co-doped systems. • The Cr-, Mn- and Co-doped β 12 borophene systems exhibit antiferromagnetic ground states, while ferromagnetic ground state occurs in the Fe-doped system. • The spin density distribution of the Cr- and Mn-doped β 12 borophene is highly localized, which have a promise for application in magnetic storage systems.

Experimental investigation of starting-up, energy-saving, and emission-reducing performances of hybrid supercapacitor energy storage systems for automobiles

Improvements in engine starting-up performance, such as reducing fuel consumption and exhaust emission pollution during the startup process, are very vital to achieve the national development goal of carbon peaking and carbon neutrality. Hybrid supercapacitor (HSC) energy storage systems containing batteries and supercapacitors (SCs) are considered promising energy storage strategies to compensate for the disadvantages of a single energy storage technology. In this paper, two kinds of novel 12 V/50 Ah and 12 V/70 Ah module-level energy storage systems composed of cell-level 3.6 V/2200 F HSCs were first designed. Analysis on their fundamental electrochemical properties under room temperature conditions was also performed. Four different types of energy storage systems composed of 12 V/70 Ah lithium iron phosphate (LFP) batteries, 12 V/70 Ah valve-regulated lead-acid (VRLA) batteries, and the aforementioned HSCs were then employed to compare their starting energy, energy-saving, and emission-reduction characteristics. Additionally, the 12 V/70 Ah HSC module saved 7.82 %, 3.18 %, and 1.65 % of fuel as compared to the 12 V/70 Ah VRLA, 12 V/70 Ah LFP, and 12 V/50 Ah HSC modules, respectively, demonstrating its superior fuel economy property. Simultaneously, the volume concentration of HC and CO emission in the startup process are 12.7 % and 13.2 % lower than that average of the other three modules, respectively, which shows a good exhaust emission reduction effect. The proposed energy storage system will provide systematic experimental data support and valuable theoretical guidance for the industrialization and application of HSCs.

Molecular dynamics simulation insight into topological structure dependence of self-healing polymer nanocomposites.

Polymer nanocomposites (PNCs), which exhibit excellent mechanical properties through the incorporation of fillers into polymers, have been extensively studied to achieve enhanced self-healing capability for their next-generation development. However, there is still a lack of investigation into the influence of the topological structures of nanoparticles (NPs) on the self-healing capability of PNCs. In this study, we utilized coarse-grained molecular dynamics simulations (CGMDs) to construct a series of PNC systems composed of NPs with different topological structures, including Linear, Ring, and Cross topologies. We employed non-bonding interaction potentials to examine the interactions between the polymer and NPs, and varied the parameters to simulate different functional groups. Our results indicate that the stress-strain curves and the rate of performance loss validate that the Linear structure is the optimal topology for mechanical reinforcement and self-healing properties. By analyzing the stress heat map during stretching, we observed that the Linear structure NPs experience significant stress, allowing the matrix chains to dominate in small recoverable deformations during stretching. It can be speculated that NPs oriented in the direction of extrusion are more effective than others in enhancing performance. Overall, this work provides valuable theoretical guidance and a novel strategy for designing and manipulating high-performance, self-healing PNCs.