Mechanical Analysis Research Articles

Analysis of influence mechanism of CO2-water coupling fracturing sandstone

The existence of hard rock layers has a serious impact on coal seam mining, in order to explore the acidification and crushing mechanism of hard sandstone rock layers, this paper adopts the self-developed CO2-water-rock coupling test device to carry out the testing of mechanical properties and internal structural characteristics of rock samples before and after the coupling action of the three sandstones, and analyzes the influencing factors of sandstone CO2 coupling crushing. The study shows that: the lower the temperature of CO2-water-rock coupling, the higher the pore pressure, the higher the volume fraction of CO2 in the coupling fracturing fluid, and the longer the coupling time, the greater the decrease in the mechanical strength of the rock samples, and the more complicated the splitting damage pattern is, and the CO2-water-rock coupling makes the pore and fracture volume fraction and fractal dimension of three kinds of sandstone samples increase to varying degrees, whereas the volume fraction of minerals and the fractal dimension decrease, and the CO2-water-rock coupling results in a decrease in the volume fraction of minerals and fractal dimension, and a decrease in the volume fraction of minerals and fractal dimension. The pore volume fraction and fractal dimension of the three sandstone samples increased to different degrees, while the mineral volume fraction and fractal dimension decreased, and the pore volume fraction and fractal dimension of the three sandstone samples decreased. The damage pattern of sandstone samples after coupling is affected by both chemical and mechanical damages. When using coupling fracturing fluid with 8 % CO2, the degree of mineral dissolution and dissolution is the largest, and the dissolution effect is larger than the precipitation effect, which has the most significant effect on the morphology type and connectivity of microscopic pore cracks, and the study in this paper has certain theoretical and practical value for the chemical softening of sandstone.

Does information content of a corporate social responsibility report matter for stock mispricing? Evidence from China

We examine the impact of the information content of a firm's corporate social responsibility (CSR) report on stock mispricing using a sample of Chinese firms from 2007 to 2021. By leveraging the recent advances in textual analysis, we apply the Word2Vec technique to detect the information content of a focal firm's CSR report. Our findings suggest that the degree of a focal firm's stock mispricing decreases with increased information content of its CSR report. The results remain robust after considering a variety of sensitivity tests. Mechanism analyses reveal that the information content of a CSR report mitigates stock mispricing by reducing information asymmetry and alleviating investor irrational behavior. Heterogeneity analysis shows that the effect is more salient when firms face higher level of uncertainty, both at the macroeconomic and industrial levels. Additionally, we document that a higher degree of information content of a CSR report contributes to a higher firm value.

Modification of ibuprofen synthesis through the mechanism analysis

Modification of ibuprofen synthesis through the mechanism analysis

Optimization design and performance improvement of ther-mal barrier coating (TBC) system

Thermal Barrier Coatings (TBC) technology has become one of the key technologies to improve the performance and prolong the service life of gas turbine and other high temperature equipment. In this study, the selection of materials, coating methods, the influence of environmental factors on the performance of TBC system and the thermal stress analysis and optimization strategy are discussed, improve the overall performance and stability of TBC system. TBC coatings were efficiently prepared by the use of Nikolay bonding layer and stabilized zirconia as top ceramic materials, combined with electron beam Physical vapor deposition (EB-PVD) and plasma spraying (APS) techniques. In addition, the thermal stress model was established by FEA, and the thermal stress distribution of TBC system under extreme operating conditions was analyzed in detail, to reduce thermal stress concentration and improve the thermal barrier effect of the coating. Finally, through the establishment of TBC system life prediction model and in-depth analysis of the failure mechanism, a series of preventive measures and performance improvement strategies are proposed, it provides theoretical basis and practical guidance for coating design of gas turbine and other high temperature equipment.

Synthesis and growth mechanism of highly crystalized multi-branched HfB2 microrods with self-toughening effect

Development of strategies to toughen HfB2 ceramic, improve their mechanical properties is the key to promote their applications in extreme thermal environments. This study explores a kind of self-toughening method of HfB2 ceramic by incorporation the highly crystalized multi-branched HfB2 microrods. The multi-branched HfB2 microrods were synthesized by sol–gel process and carbothermal reduction, exhibiting length of 6–13 μm and diameter of 0.60–1.50 μm, respectively. Detailed analysis of the formation mechanism of HfB2 microrods reveals that the HfB2 multi-branched structure is a collaborative consequence of orientation attachment mechanism and reactive templates growth, in which process monoclinic HfO2 crystals transform into crystalized HfO2 microrods at ∼1000 °C, and worked as template to induce one-dimensional HfB2 microrods. Furthermore, spark plasma sintering experiments show that the optimal mechanical properties were attained by 6 wt% addition of HfB2 microrods, comparing with HfB2 ceramics free of self-toughening agent, the hardness and fracture toughness of self-toughened HfB2 ceramic improved by 8.82 % and 81.91 % respectively, demonstrating the effectiveness of self-toughening of the microrods without sacrificing the hardness of HfB2 ceramic. Thus, it can be seen that the work has important reference value for the synthesis of HfB2 powder with different morphologies and the toughening of HfB2 ceramics.

Multi-omics analysis of the biological mechanism of the pathogenesis of non-alcoholic fatty liver disease

Multi-omics analysis of the biological mechanism of the pathogenesis of non-alcoholic fatty liver disease

A pathway to refined stress and strain distributions in aerospace-grade Ti/Al bi-metal sheets: Synergizing theoretical insights and FEM simulations

This study introduces an innovative theoretical model critical for predicting stress and strain distributions in Ti/Al bi-metal sheet production and its subsequent deep drawing process. Grounded in extensive mechanical and geometric analysis, the model facilitates manufacturing process optimization and the production of high-quality components. Finite Element Method (FEM) simulations are integrated to examine the significant effects of die geometric parameters on metal flow dynamics and susceptibility to material stress. The model’s precision is enhanced by incorporating anisotropic material properties and cohesive zone models. A rigorous experimental framework validates the model, highlighting the practical utility of optimized parameters in Ti/Al bi-metal component fabrication. Additionally, uniaxial tensile tests using the Video Image Correlation-3D (VIC-3D) system provide detailed insights into material deformation, elucidating stress distribution and metal flow in composite layers. Thus, the research presents a refined methodology for the efficient production of Ti/Al bi-metal components, offering valuable knowledge transferable to various materials and processing scenarios. The findings of this work are expected to make a significant impact on material engineering and mechanical manufacturing.

Mechanical properties and durability analysis of CS-CG stabilized soil: Towards sustainable subgrade soil enhancement

In this study, carbide slag (CS) and coal gangue (CG) powder were utilized to enhance the properties of the subgrade soil. CS-CG stabilized soil underwent lab experiments to assess its mechanical properties and durability. Tests included unconfined compressive strength (UCS), compressive resilient modulus (CRM), and California bearing ratio (CBR) at stabilizer dosages of 5 %, 10 %, and 15 %. Additional tests, such as dry-wet cycling, salt solution immersion, permeability, leaching, thermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscope (SEM) and mercury intrusion porosimetry (MIP), were conducted specifically for the 10 % dosage. The mechanical properties and durability were comprehensively analyzed, with a microscopic investigation into pore size. Furthermore, the soil-water characteristic curve (SWCC) of CS-CG stabilized soil is derived through MIP, providing insights into its impact on the material's strength. Results showcased favorable bearing capacity and durability of CS-CG stabilized soil. The optimal mixing dosage is 10 %, with the best ratio being CS: CG= 70: 30. After 6 dry-wet cycles, UCS loss rate was 18.6 %, comparable to 4 % Portland cement (PC) stabilized soil. Dry-wet cycle characteristics surpassed PC and Lime stabilized soils. Immersion in a 5 % NaCl solution for 30 days yielded a UCS of 3.8 MPa at 28-day age, while exposure to 5 % Na2SO4 solution led to an 11.6 % strength decrease compared to NaCl. Permeability coefficient indicated low permeability akin to PC and Lime stabilized soils. Heavy metal content met standards, with minimal increase during cycles. Hydration products mainly comprised C-S-H gel, Ca(OH)2 crystals, and carbonate modification. Analysis suggested capillary and transition pores predominantly, with minimal macropores presence. Dry-wet cycles induced a marginal increase in pore size, with negligible overall impact. SWCC predicted water content (θs) ranged from 30 % to 32 %, with a slight increase in matrix suction during dry-wet cycles. CS-CG stabilized soil shows favorable mechanical properties, durability, and environmental sustainability, indicating its potential as a substitute for traditional cement and lime treatments in subgrade soil reinforcement.

Astrocyte-TREM2 alleviates brain injury by regulating reactive astrocyte states following ischemic stroke.

Triggering receptor expressed on myeloid cells 2 (TREM2) has been shown to confer strong neuroprotective effects in acute ischemic stroke (AIS). However, as the vast majority of research findings to date are based on its functions in microglia, the precise role of TREM2 in astrocytes after AIS is unknown. Here, both loss- and gain-of-function experiments were employed to investigate how astrocytic TREM2 influences the pathogenesis of AIS in vivo and in vitro. Our results demonstrated that cerebral ischemia triggered induction of TREM2 expression on reactive astrocytes following AIS. In addition, astrocyte-specific TREM2 knockout mice exhibited much greater brain injury than TREM2 flox/flox controls following AIS, as evidenced by increased cerebral infarct volume, neuronal apoptosis and neurological deficit, which was associated with an increased expression of pro-inflammatory molecule complement component 3 (C3) on reactive astrocytes and activation of microglia/macrophages but decreased expression of S100 calcium binding protein A10 (S100A10) and arginase1 (Arg1) on reactive astrocytes. Mechanistic analyses revealed that astrocytic TREM2 alleviated brain injury by inhibiting detrimental actions of reactive astrocytes but promoting their neuro- and glioprotective actions via the kruppel-like transcription factor-4-nuclear factor-κB axis. Together, this study provides novel evidence for a critical protective role of astrocyte-derived TREM2 in AIS and highlights a potential therapeutic target for the treatment of AIS.

Revealing the Ground Deformation and Its Mechanism in the Heihe River Basin by Interferometric Synthetic Aperture Radar and Optical Images

The Heihe River Basin (HRB), located on the northeast margin of the Qilian Mountains, is China’s second largest inland river basin. It is a typical oasis-type agricultural area in northwest China’s arid and semiarid areas. It is important to monitor and investigate the spatiotemporal distribution characteristics and mechanisms of surface deformation in HRB for the ecology of inland river basins. In recent years, research on HRB has mainly focused on hydrology, meteorology, geology, or biology. Few studies have conducted wide-area monitoring and mechanism analysis of the surface stability of HRB. In this study, an improved interferometric point target analysis InSAR (IPTA-InSAR) technique is used to process 101 Sentinel-1 SAR images from two adjacent track frames covering the HRB from 2019 to 2020. The wide-area deformation of the HRB is obtained first for this period. The results show that most of the surface around the HRB is relatively stable. There are six areas with an extensive deformation range and magnitude in the plain oasis area. The maximum deformation rate is more than 50 mm/year. The maximum seasonal subsidence and uplift along the satellites’ line-of-sight (LOS) direction can be up to −70 mm and 60 mm, respectively. Moreover, we use the Google Earth Engine platform to process the multisource optical images and analyze the deformation areas. The remote sensing indicators of the deformation areas, such as the normalized difference vegetation index (NDVI), soil moisture (SMMI), and precipitation, are obtained during the InSAR monitoring period. We combine these integrated remote sensing results with soil type and precipitation to analyze the surface deformations of the HRB. The spatiotemporal relationships between soil moisture, vegetation cover, and surface deformation of the HRB are revealed. The results will provide data support and reference for the healthy and sustainable development of the inland river basin economic zone.

Suppression effects of different extinguishing agents on vent gases fires from lithium-ion batteries after thermal runaway: A comprehensive experimental and numerical study

During the thermal runaway process of lithium-ion batteries, the release of vaporized electrolyte and combustible gases can lead to the formation of a jet flame, posing a significant fire or explosion risk. In order to deal with the threat of lithium-ion battery vent gas fires to the safety of energy storage power stations, it's crucial to identify effective fire extinguishing agents for lithium-ion battery systems. This study employs a combination of experimental and numerical simulation methods to assess the suppression capabilities of CO2, N2, and HFC-227ea on vent gas/air premixed flames originating from lithium-ion batteries with various cathode materials. Laminar flame speed of vent gas/air/extinguishing agent premixed flames at specific equivalence ratios were measured using a Bunsen burner device under ambient temperature and atmospheric pressure conditions. Additionally, numerical calculations of laminar flame speed and adiabatic flame temperature were conducted using CHEMKIN-Pro, accompanied by an analysis of the chemical inhibition mechanism of HFC-227ea. The findings reveal that although HFC-227ea may slightly elevate the adiabatic flame temperature at lower equivalence ratios, its overall fire extinguishing efficacy surpasses that of CO2 and N2. These results offer valuable insights for selecting appropriate fire extinguishing agents for energy storage power stations, thereby enhancing the safety standards of energy storage systems.

Advancing effective energy transition: The effects and mechanisms of China's dual-pilot energy policies

Quantifying energy transition (ET) and evaluating energy policies are crucial for global sustainable development. This study measures the energy transition index (ET−CCD) at the prefecture-level city level in China and evaluates the synergistic effects of the dual-pilot energy policy of New Energy Demonstration City (NEDC) and Low Carbon City Pilot (LCCP) based on the energy trilemma (ETR) of coordinated development in terms of security (ES), justice (EJ) and sustainability (ESU). The results show that the overall ET−CCD is increasing, with the eastern and central regions leading, the western region growing significantly, and the northeast fluctuating upward, indicating regional disparities. Compared to single policies, the dual-pilot energy policies have a more significant promoting effect on energy transition, especially in eastern, western, non-central cities, resource-based cities, and cities with high carbon emission reduction potential. Mechanism analysis reveals that the dual-pilot energy policies significantly promote ES and EJ , but have a negative impact on ESU in the short-term. Improvements in ES, EJ and ESU all significantly promote energy transition, with ES serving as a complete mediator, while EJ and ESU serving as partial mediators. Additionally, the findings remain stable in robustness tests and provide data support for a flexible mix of policy instruments to facilitate energy transition.

How digital inclusive finance affects the health of the migrant population –evidence from China migrants dynamic survey

ABSTRACT Digital inclusive finance plays a pivotal role in enhancing the welfare of the migrant population. This paper adopts data from the 2017–2018 China Migrants Dynamic Survey to analyse the effect of digital inclusive finance on migrants’ health and the underlying mechanisms. The results show that digital inclusive finance significantly improves migrants’ health, which remains robust after taking full consideration of endogeneity. The mechanism analysis suggests that digital inclusive finance alleviates environmental pollution and enhances the accessibility of healthcare services, which in turn improves the health of migrants. Furthermore, the heterogeneity analysis reveals that compared with other migrants, digital inclusive finance has a greater health-enhancing effect on the middle-aged and those without higher education or with public health education.

Prediction of Welding Deformation Using the Thermal Elastic–Plastic Finite Element Method by Considering Welding Interpass Temperature

In this study, we propose a method for predicting welding deformation caused by multi-pass welding using the thermal elastic–plastic finite element method (TEP-FEM) by considering the interpass temperature. This method increases the interpass temperature, which has not been considered in the existing TEP-FEM, from 200 °C to 1000 °C, and simultaneously performs thermal and mechanical analyses. In addition, this method can also evaluate temperature history and the time it takes to weld. By predicting the welding deformation using this method, angular distortion prediction was reduced from 16.75 mm to 10.9 mm compared to the case where the interpass temperature was cooled to room temperature. Additionally, the deformation error was significantly reduced from 6.14% to 2.92% compared to that of the strain as directed boundary method used in a previous study. Additionally, our research demonstrated that interpass temperatures above 800 °C can result in increased deformation errors. In conclusion, it is essential to select an appropriate temperature to minimize deformation error.

Numerical analysis of fissure development and self-healing mechanism on surface due to longwall mining

Numerical analysis of fissure development and self-healing mechanism on surface due to longwall mining

Can non-subsidised policies for new energy vehicles improve the quality of enterprise innovation? evidence from China

ABSTRACT Through an investigation of listed new energy vehicle (NEV) enterprises in China from 2012 to 2021, we examined the impact of three NEV non-subsidised policies on enterprise innovation quality from both production and market ends, using the PVAR model. Our study yielded several key findings. First, non-subsidised policies have an overall positive effect, with the production-market-end policy represented by the dual-credit performing the best, followed by the single production-end policy (access catalog), and the market-end policy (government procurement) having the lowest impact. This difference is more pronounced in the two-stage sample (subsidy era, 2012-2016; post-subsidy era, 2017-2021). Second, the analysis of policy mechanisms shows that non-subsidised policies have an R&D investment effect and a product scale effect, but each emphasises specific policy-innovation paths. Third, the market competition pressure has a positive moderating effect on the impact of the dual-credit and access catalog policies, while the moderating effect on government procurement is not significant. Moreover, the external regional innovation atmosphere also has a heterogeneous impact on the incentive effect of non-subsidised policies. These results have important implications for adjusting NEV industry policy in the post-subsidy era and for the discussion of the relationship between non-subsidised policies and technological innovation.

CEO activism is not equal to CEO activism: a typology of executives' political statements

PurposeWhen CEOs are publicly weighing in on sociopolitical debates, this is known as CEO activism. The steadily growing number of such statements made in recent years has been subject to a flourishing academic debate. This field offers first profound findings from observational studies. However, the discussion of CEO activism lacks a thorough theoretical grounding, such as a shared concept accounting for the heterogeneity of sociopolitical incidents. Thus, the aim of this paper is to provide an archetypal framework for CEO activism.Design/methodology/approachThe authors used a multiple case study approach on 145 activism cases stated by CEOs and found seven distinct statement archetypes.FindingsThe study identifies four main structural design elements accounting for the heterogeneity of activism, i.e. the addressed meta-category of the statement, the targeted outcome, the used tonality and the orientation of the CEOs’ positions. Further, the authors found seven distinguishable archetypes of CEO activism statements: “Climate Alerts”, “Economy Visions”, “Political Comments”, “Self-reflections and Social Concerns”, “Tech Designs”, “Unclouded Evaluations” and “Descriptive Explanations”.Research limitations/implicationsThis typology classifies the heterogeneity of CEO activism. It will enable the analysis of interrelationships, mechanisms and motivations on a differentiated level and raise the comprehensibility of research-results.Practical implicationsThe framework supports executives in understanding the heterogeneity of CEO activism and to analyse personality-fits.Originality/valueTo the authors’ knowledge, this marks the first conceptualisation of activism developed cross-thematically. The work supports further theory-building on CEO activism.

Molecular aspects of the exercise response and training adaptation in skeletal muscle

Skeletal muscle plasticity enables an enormous potential to adapt to various internal and external stimuli and perturbations. Most notably, changes in contractile activity evoke a massive remodeling of biochemical, metabolic and force-generating properties. In recent years, a large number of signals, sensors, regulators and effectors have been implicated in these adaptive processes. Nevertheless, our understanding of the molecular underpinnings of training adaptation remains rudimentary. Specifically, the mechanisms that underlie signal integration, output coordination, functional redundancy and other complex traits of muscle adaptation are unknown. In fact, it is even unclear how stimulus-dependent specification is brought about in endurance or resistance exercise. In this review, we will provide an overview on the events that describe the acute perturbations in single endurance and resistance exercise bouts. Furthermore, we will provide insights into the molecular principles of long-term training adaptation. Finally, current gaps in knowledge will be identified, and strategies for a multi-omic and –cellular analyses of the molecular mechanisms of skeletal muscle plasticity that are engaged in individual, acute exercise bouts and chronic training adaptation discussed.

Mechanical performance and anisotropic analysis of rubberised 3D-printed concrete incorporating PP fibre.

The research investigates the effects of substituting sand with rubber particles derived from waste tyres-up to 40% by volume-and the inclusion of polypropylene (PP) fibres. Unlike steel fibres, which can cause operational challenges and surface irregularities in the printing process, PP fibres' flexibility integrates well within the concrete matrix. This integration ensures smooth extrusion and a high-quality surface finish, enhancing the printability of the concrete. The study's findings reveal that including rubber particles and PP fibres impacts the concrete's properties, showing a general decline in compressive and flexural strengths as the rubber content increases. Nevertheless, the PP fibre-enhanced mixtures maintain sufficient structural strength, demonstrating an anisotropic compressive strength above 30MPa and a flexural strength of 4MPa. These results underscore the feasibility of using rubberised 3D-printed concrete with PP fibres in sustainable construction practices, aligning with standards (ACI 318:2018) and contributing to eco-friendly and innovative construction methodologies.

Design and mechanical properties analysis of bionic tube based on cattle horn structure

Composite tubes are widely adopted in engineering protections owning to desirable passive energy absorption. With the aim of enhancing energy absorption and making full use of structural materials, a novel tube inspired by the structure of cattle horn has been designed. It consisted of a shell composed of nested tubes and a core composed of evenly distributed tubes, which are connected by beams. The energy absorption properties of bionic tube, six-cell tube, four-cell tube and circular tube were compared by numerical models verified by axial compression. The factors affecting mechanical responses and energy absorption capacities of bionic tube were analysed. Compared to the six-cell tube, the bionic tube exhibited a 104.91% increase in peak load, a 239.51% increase in mean load and an 83.39% increase in specific energy absorption. Under the premise of ensuring the energy absorption, mean load and crushing force efficiency, the mass and peak load can be controlled by limiting the wall thickness and height of core. The proposed bionic tube had the potential to be applied in the automobile and aerospace industry.