Stress Characteristics Research Articles

Exploring EEG characteristics of multi-level mental stress based on human–machine system

Objective. The understanding of cognitive states is important for the development of human–machine systems (HMSs), and one of the fundamental but challenging issues is the understanding and assessment of the operator’s mental stress state in real task scenarios. Approach. In this paper, a virtual unmanned vehicle (UAV) driving task with multi-challenge-level was created to explore the operator’s mental stress, and the human brain activity during the task was tracked in real time via electroencephalography (EEG). A mental stress analysis dataset for the virtual UAV task was then developed and used to explore the neural activation patterns associated with mental stress activity. Finally, a multiple attention-based convolutional neural network (MACN) was constructed for automatic stress assessment using the extracted stress-sensitive neural activation features. Main Results. The statistical results of EEG power spectral density (PSD) showed that frontal theta-PSD decreased with increasing task difficulty, and central beta-PSD increased with increasing task difficulty, indicating that neural patterns showed different trends under different levels of mental stress. The performance of the proposed MACN was evaluated based on the dimensional model, and results showed that average three-class classification accuracies of 89.49%/89.88% were respectively achieved for arousal/valence. Significance. The results of this paper suggest that objective assessment of mental stress in a HMS based on a virtual UAV scenario is feasible, and the proposed method provides a promising solution for cognitive computing and applications in human–machine tasks.

The Optimization of Secondary Lining Construction Time for Shield Tunnels Based on Longitudinal Mechanical Properties

In the field of shield tunnels, the occurrence of uneven longitudinal settlement in segment linings has presented persistent challenges, including heightened risks of localized damage and water leakage. While the adoption of a secondary lining has been proposed as a viable solution to these issues, the question of how to select an appropriate construction time for the secondary lining, one that enables it to fully harness its load-bearing capacity while optimizing the tunnel’s overall stress and deformation characteristics, continues to be a pressing concern. To address this issue, this study established a three-dimensional longitudinal refined numerical model of double-layer-lined shield tunnel. In addition, the deformation degree of the segment lining was used as a time indicator to define the construction time for the secondary lining. Subsequently, an analysis of the impact of the construction time of the secondary lining on the longitudinal mechanical properties of the double-layer-lined shield tunnel is conducted through an assessment of tunnel longitudinal deformation and structural stress. The research findings indicated that the construction of the secondary lining improved the longitudinal deformation resistance of shield tunnels. Simultaneously, it led to a significant increase in the longitudinal shear forces within the segment lining and a notable reduction in longitudinal bending moments. Moreover, the construction time of the secondary lining played a pivotal role in these alterations. Considering the longitudinal force situations and load-bearing characteristics of the double-layer lining structure, it was determined that the optimal construction time for the secondary lining fell within the range of 20% to 40% of the total construction duration. In this scenario, the deformation and internal forces within the segment lining remained within permissible limits. Additionally, both the segment lining and the secondary lining were able to fully utilize their load-bearing capacities, ensuring the economic and safety aspects of the tunnel.

Experimental and Numerical Study on Progressive Collapse of the Midcolumn in a Glulam Timber Frame Exposed to Fire

This paper presents experimental and numerical investigations on the progressive collapse behavior of a two-story glulam frame when the middle column is exposed to ISO834 standard fire. The stress characteristics, temperature distributions, and deformation relationship curves of the bottom middle column after a fire are obtained. The collapse resistance performance and the mechanism of the glulam structure under local fire are studied in combination with the failure mode of the frame. The experimental results show that the failure time of the middle column in fire is 16.8 min, and the time to determine the progressive collapse of the structure is 17.17 min when the rotation angle exceeds the limit. The structure can remain stable for some time after the failure of the fire column, but as the fire continues to spread, the structure will collapse further. In addition, a temperature-field analysis model with the grid element type of DC3D8 and a structural field analysis model with the grid element type of C3D8R was established by using ABAQUS software under the experimental conditions. The numerical simulation is carried out by means of thermal–mechanical sequential coupling. The numerical simulation results show that the temperature of the beam end rose to more than 300 °C in about 15 min although it was not directly exposed to fire. The temperature of the whole connector at the pillar foot in the bottom column reached more than 700 °C when the fire time reached 60 min. The numerical simulation results agree well with the experimental results. The analysis results show that, in the failure process of the fire column, the junction of beam ends begins to produce stretching force to form a catenary effect. As the fire time increases, the catenary effect eventually fails. The stretching force at the beam end rapidly decreases and withdraws from the work, causing the progressive collapse of the frame.

Retracted: Systematic Analysis of Tumor Microenvironment Patterns and Oxidative Stress Characteristics of Endometrial Carcinoma Mediated by 5-Methylcytosine Regulators.

[This retracts the article DOI: 10.1155/2022/6431164.].

Analysis of periodic pulsating blood flow of fractional Maxwell power-law fluid in carotid artery with elastic vessel wall

Hemodynamic analysis reveals a highly significant effect on the prevention, diagnosis, and treatment of human vascular diseases. This article goes deeply into the periodic pulsatile blood flow in the carotid artery with an elastic vessel wall. In view of blood rheological experimental data, the constitutive equation of fractional Maxwell power-law fluid with yield stress, which can describe the four characteristics of yield stress, viscoelasticity, shear thinning, and thixotropy is established. Meanwhile, drawing support from the data of pulsatile flow, the finite Fourier series of pressure gradient with a period of 1 s has been proposed. Leading into Hooke’s law can build the fluid-structure coupling boundary condition of blood flow and elastic vessel wall. The numerical solutions are got hold of finite difference method integrated with the newly developed L1-algorithm, and their convergence and stability of which are verified. The axial velocities of blood under different constitutive relationships are compared. The results throw light that other constitutive relationships underestimate the velocity of blood. Furthermore, the flow rate and wall shear stress on different fluid are calculated. It can be concluded that compared with Bingham fluid, the maximum and minimum flow rate/wall shear stress of fractional Maxwell power-law fluid with yield stress increases by 19% and 32%, respectively. The flow rate lags behind the pressure gradient and has time delay effect, on the contrary, the velocity of blood vessel wall is keeping pace with the pressure gradient. The effects of relevant physical parameters on velocity are discussed. In addition, the spatiotemporal distribution of blood flow in cerebral artery and femoral artery are analyzed.

Numerical investigation of the effect of oblique laser shock processing parameters on the residual stress and deformation characteristics of TC6 titanium alloy

Oblique laser shock processing (OLSP) can provide a new solution for improving the mechanical properties of complex structural elements. In this paper, a spatial distribution model of OLSP shock wave pressure is established and validated to study the residual stress (RS) field and surface morphology of titanium alloy TC6 treated by OLSP using the finite element method. The effects of the incident angle, overlapping rate, and scanning pattern on the RS field and surface morphology were investigated. The OLSP results indicate that the overlapping rate should be at least 50%. The RS field and surface morphology obtained with the interval scanning pattern are more uniform compared to snake and spiral. With a 50% overlapping rate and interval scanning pattern, the surface roughness was found to be 0.16, and the surface residual compressive stress fluctuation amplitude was reduced by 40.07%. The results provide a theoretical basis for complex structures of LSP.

Psychological and Physiological Effects of Low-Level Meaningful Artificial Sounds on Intellectual Tasks

AbstractThe present study aimed to investigate the psychological and physiological effects of low-level meaningful artificial sounds on intellectual tasks. The psychological factors related to the degree of disturbance, concentration, and stress, as measured by subjective evaluation, were compared with the degree of physiological stress, as measured using salivary alpha-amylase activity. The results indicated that human speech and chewing sounds caused similar levels of psychological stress while performing intellectual tasks; however, chewing sounds caused comparatively less physiological stress than did human speech sounds. These findings suggest that depending on the sound stimulus, psychological and physiological stress characteristics may not coincide.

Evolution from gas outburst to coal outburst: An analysis from the perspective of asynchronous transfer difference of gas mass and coal deformation

Considering that coal and gas outburst is a highly complex nonlinear process, the synchronous energy criterion based on the gas expansion energy and the coal deformation potential energy is often adopted to evaluate the hazard. However, the synchronous energy criterion without considering the transfer difference of gas mass and coal deformation has defects in describing the evolution characteristics of coal-rock gas dynamic disasters. Hence, it is necessary to investigate the asynchronous characteristics of the gas expansion energy and the coal deformation potential energy. In this study, the deformation characteristics of coal injected with He and CH4 were measured respectively with the aid of a self-developed device for observing the asynchronous characteristics of effective stress and adsorption-induced deformation. Besides, the differentiated propagation characteristics of gas pressure and adsorption-induced deformation were obtained, and the asynchronous propagation starting point and propagation rate difference between them were analyzed and determined. Furthermore, based on the calculation formula of gas expansion energy and coal deformation potential energy, the values and propagation differences of the two types of energy at different times were revealed. Finally, the typical outburst phenomena were explained using the energy asynchronous theory. The following research findings were yielded. The adsorption-induced expansion process lasts longer than the gas pressure reduction process, which is the reason for asynchronous propagation of gas expansion energy and coal deformation potential energy. The coal deformation potential energy can be further divided into mechanical compression strain energy and desorption shrinkage strain energy. In the initial stage of outburst, the main sources of energy are free gas expansion energy and mechanical compression strain energy. As time progresses, the effect of desorption gas expansion energy and desorption shrinkage strain energy gradually strengthens. From the perspective of energy asynchrony, outburst occurrence at a low gas concentration in deep regions and delayed outburst in cross-cut coal uncovering can be explained as the result of dynamic load instability in surrounding stopes brought about by lagging superimposed deformation disturbances after gas desorption, or the result of self-induced lagging shrinkage deformation formed under special boundary conditions. The findings of this study are helpful to guide the design and connection of the prevention and control methods of deep coal-rock gas dynamic disasters.

Stress, child-caregiver disability, and family dysfunction characteristics contributing to child abuse and maltreatment recurrence: a structural equation model

ABSTRACT Child abuse, neglect, and maltreatment (CANM) represents a significant public health threat. The study’s goal was to identify factors contributing to CANM and its high recurrence. We utilized 2019–2020 National Child Abuse data to test a structural equation model of Child/Caregiver Disability variables; Home Instability variables; and CANM recurrence. We hypothesized a six-factor model with Home Instability as a mediator. Of 1,221,176 victims, 29.9% had a prior victimization. A four-factor, mediational structural equation model showed strong fit (GFI = 0.946, NFI = 0.919) and was superior to alternative models. The study provides a framework for community leaders to reduce CANM.

Model tests on dynamic responses of surrounding rock and support structure on underground tunnel under combined dynamic and static loading

The effect of blasting vibration on the macroscopic failure characteristics of underground tunnels has been investigated, but little attention has been paid to the stress and deformation characteristics of underground tunnels under the combined action of explosion waves and in-situ stresses. Consequently, enhancing the bearing capacity of surrounding rock masses by adopting effective reinforcement measures is an urgent problem that needs to be solved. Due to high in situ stresses at great depths, it is difficult to conduct field tests on various reinforcement methods. In this study, using the deep underground tunnels as a prototype, large-scale physical model tests were adopted to examine the stress and deformation characteristics of the unlined tunnels, the rock bolt reinforced tunnels, and the lined tunnels under the coupling action of in-situ stress and blasting waves induced by different charge quantities, with the purpose of providing the necessary theoretical and technical support for the design and support of deep protective engineering.

Seizure-related stress and arousal responses mediate a relationship between anxiety trait and state in epilepsy

BackgroundEpilepsy causes substantial psychological distress and anxiety, primarily due to seizures. However, the impact of stress responses and changes in arousal and their association with anxiety patterns in patients with epilepsy (PWE) remains unclear. This study aimed to investigate the relationships among seizures, stress and arousal characteristics, and trait and state anxiety characteristics in PWE. MethodsOur sample consisted of 159 outpatients with epilepsy recruited from five institutions in Japan in 2020. Participants completed the State-Trait Anxiety Inventory-Form JYZ (STAI) and the Japanese-Stress Arousal Check List (J-SACL). We analyzed the correlations between inventory scores and clinical information. Using principal component analysis (PCA), we derived epilepsy-specific stress/arousal characteristics, which accounted for high arousal and low-stress levels, termed epilepsy-specific stress or arousal response (ESAR), from the J-SACL scores. We conducted a mediation analysis to assess the mediating role of ESAR in the relationship between traits and state anxiety. ResultsWe found significant correlations between J-SACL stress and arousal factors (r = −0.845, p < 0.001), ESAR and seizure frequency (r = −0.29, p < 0.001), ESAR and trait anxiety scores on the STAI (r = −0.77, p < 0.0001), and ESAR and state anxiety scores on the STAI (r = −0.60, p < 0.0001). Mediation analysis supported by the Monte Carlo method revealed that ESAR significantly mediated the association between trait and state anxiety. ConclusionsThese findings elucidate the epilepsy-specific stress and arousal characteristics and their roles in mediating traits and state anxiety. These results may reflect the long-term clinical course and unique emotion recognition tendencies in epilepsy.

ANALYSIS OF HYDRODYNAMIC INTERACTION OF WELLS BASED ON DETERMINATION OF PRODUCTION AND INJECTION COMPENSATION BALANCE USING THE EXAMPLE OF RESERVOIR — BARREM CLINOFORM OF PRIOBSKY SEDIMENTATION BASIN

Abstract. Long-term development of oil fields using a reservoirpressure maintenance system by injecting water into the formation leadsto a number of features of well operation identified during fieldgeophysical and hydrodynamic studies. The combination and processingof parameters characterizing the field development indicators and theoperation of wells in the injection-production section make it possible toconduct a qualitative assessment of the processes occurring in the subsoil.The article describes the procedure for determining possible sources ofwater flooding of oil wells in a large multi-zone field in Western Siberia.In order to determine the compensatory balance of production andinjection taking into account the regional stress characteristic of the field,calculations were made using a geometric figure in the form of an ellipse.The drainage zone described in this way does not contradict the ratio ofthe number of injection and oil wells in the nine-point developmentsystem. The analysis of geological and field information and hydrodynamicstudies made it possible to identify a difference in the signs of increasedwater cut of the product with uncontrolled growth of a man-made fracturein the direction of regional stress and when overlying horizons, which areinterbedded with water-saturated sandy bodies formed under the Bystrinskyclay pack during the regression cycle of sedimentation, were included inthe development. From the point of view of the analysis results, one of thepossible reasons for the development of man-made fluid contacts betweenthe injected and formation water of the overlying formation is a violationof the cement support behind the production string of the injection well.And as a result, there is a top-down flow in the production wells. Theoccurrence of disturbances in the cement support is a technical reason andcan be associated with technological processes carried out on injectionwells during operation, or imperfection in adhesion during insulation andtechnical work. The methods used in the article to determine thehydrodynamic interaction of wells and the signs of formation ofinterformation fluid contacts made it possible to assess the possiblereasons for the increase in water cut in the complex, low-permeability oilreservoirs of the Goteriv-Barremian clinoform of the Priobskysedimentation basin.

Experimental study on the interrelation of multiple mechanical parameters in overburden rock caving process during coal mining in longwall panel

In order to comprehend the dynamic disaster mechanism induced by overburden rock caving during the advancement of a coal mining face, a physical simulation model is constructed basing on the geological condition of the 21221 mining face at Qianqiu coal mine in Henan Province, China. This study established, a comprehensive monitoring system to investigate the interrelations and evolutionary characteristics among multiple mechanical parameters, including mining-induced stress, displacement, temperature, and acoustic emission events during overburden rock caving. It is suggested that, despite the uniformity of the overburden rock caving interval, the main characteristic of overburden rock lies in its uneven caving strength. The mining-induced stress exhibits a reasonable interrelation with the displacement, temperature, and acoustic emission events of the rock strata. With the advancement of the coal seam, the mining-induced stress undergoes four successive stages: gentle stability, gradual accumulation, high-level mutation, and a return to stability. The variations in other mechanical parameters does not synchronize with the significant changes in mining-induced stress. Before the collapse of overburden rock occurs, rock strata temperature increment decreases and the acoustic emission ringing counts surges with the increase of rock strata displacement and mining-induced stress. Therefore, the collaborative characteristics of mining-induced stress, displacement, temperature, and acoustic emission ringing counts can be identified as the precursor information or overburden rock caving. These results are in good consistent with on-site situation in the coal mine.

Pattern of Influence of the Mining Direction of the Protective Seam on the Stress of the Surrounding Rock

The maximum principal stress of the original rock has obvious directionality, and the pressure relief effect is different when the protective seam is mined along different directions. In this paper, the Fast Lagrangian Analysis of Continua (FLAC3D 6.0) numerical simulation software was used to establish a numerical calculation model according to the actual stratum conditions of the Pingdingshan No. 8 Coal Mine. The distribution and evolutionary characteristics of three-dimensional stress and three-dimensional displacement of the stope are studied under the condition that the mining direction of the protective seam is parallel to or vertical to the maximum principal stress direction of the original rock; the pattern of influence of the mining direction on the pressure relief and outburst prevention effect of the protective seam mining is analyzed. For the protective seam, the maximum principal stress in the coal in front of the protective seam cut–hole is significantly reduced, and the outburst potential is reduced in parallel mining. However, in vertical mining, the maximum principal stress in the coal in front of the protective seam cut–hole increases significantly, and the outburst potential increases. For the protective seam and surrounding rock, parallel mining can more fully reduce the maximum principal stress of the protective seam, reduce the difference in the three-dimensional stress, and effectively reduce the outburst potential of the protective seam. Therefore, parallel mining can not only improve the safety of the protective seam but also improve the pressure relief and outburst prevention effect of the protective seam. This conclusion is verified by the outburst prevention effect of the parallel mining of the remote upper protective seam in the Pingdingshan No. 8 Coal Mine. The research results are helpful for optimizing mine outburst potential prevention and control work from the aspect of mining layout. Through parallel mining, the outburst potential of the mine can be effectively reduced overall.

Study on Failure Mechanism and Zoning Control of Weakly Cemented Roadway Adjacent Chambers

The strength of weakly cemented surrounding rock is low, and the bonding ability is weak. The rock forming roadway is affected by the stress disturbance after the excavation and support of adjacent chambers, which can lead to problems such as large deformation of the surrounding rock and significant differences in deformation areas. Through comprehensive theoretical analysis, on-site measurement, and numerical simulation, the distribution and evolution characteristics of stress in the surrounding rock adjacent chambers were studied. The results of this study indicated that, the surrounding rock stress crosses the adjacent chambers and forms a concentrated area near the weakly cemented roadway, and that the stress increase ratio of surrounding rock within the stress concentration range can reach 50%. A longer distance of the chambers from the weakly cemented roadway corresponds to a smaller surrounding rock stress concentration area. When the distance exceeds approximately 12 times the average height of the chambers, the surrounding rock stress concentration tends to disappear. According to the support concept of “allowable deformation” + “released pressure” + “restricted shape”, control countermeasures for surrounding rock at different levels are given, which are dominated by U-shaped steel + flexible material and are effective for controlling roadway deformation.

Ultra-lightweight low-carbon LC3 cement composites: Uniaxial mechanical behaviour and constitutive models

The present study aims to characterize the constitutive models of a novel ultra-lightweight low-carbon LC3 cement composite (ULCC-LC3) under monotonic uniaxial compression and tension tests. The compressive stress–strain curves of ULCC-LC3 were obtained based on axial compressive tests. The curve characteristics were analyzed and the data was fitted with the existing concrete compression constitutive model. Modified axial compression constitutive model for ULCC-LC3 was proposed and verified using the independent test data and related data of ULCC in other literatures. The characteristics of tensile stress–strain curves of ULCC-LC3 were also analyzed and studied. Based on existing experimental data, the applicability of the Tetsushi et. al.’s model to this composite was verified. The experimental results show that use of PE fibers can improve the ductility of ULCC-LC3. As compared with normal concrete, ULCC-LC3 exhibits a higher compressive peak strain (over 0.3% for fiber reinforced specimens and over 0.5% for non-fiber reinforced specimens). These findings contribute to the understanding of the mechanical behavior of ULCC-LC3 and provide constitutive models that can be used in numerical simulations and engineering applications to promote the use of this novel ultra-lightweight low-carbon material.

An analytical model for stress estimation at the soil-tire interface using the dynamic contact length

The interaction between soil and tire is a complex phenomenon influenced by various factors, such as soil properties, vertical load on the wheel, and tire characteristics. However, estimating stress at the tire-soil interface is a challenging task due to the unpredictable nature of soil. Existing models for investigating the wheel-soil interaction are based on soil mechanical parameters, which are highly variable and require significant time and resources to measure accurately. In contrast, the amount of wheel sinkage into the soil can be measured in real-time and is derived from the mechanical properties of the soil. Therefore, there is a need to establish a relationship between stress and wheel characteristics such as dynamic contact length and tire sinkage in soil. To address this issue, this study introduces an analytical method to estimate the dynamic contact surface between the tire and soil. A mathematical model is then proposed to estimate stress, assuming the contact surface and variable pressure at the interface between the soil and tire. The stress model is validated through experimental tests conducted at three different vertical load levels and four different wheel traffic levels in the soil bin, repeated three times.

Evaluation index and improvement method for interlayer bonding property of ballastless track

Inadequate bonding can bring detrimental interlayer separation problems in high-speed slab ballastless tracks. Thus, it is imperative to elucidate the stress characteristics of the interlayer in high-speed railway ballastless track when subjected to the combined influence of train and environmental factors. The present study employs finite elements to elucidate the change pattern, with the CRTS III slab ballastless track serving as an illustrative case. The findings indicated that interlayer separation of ballastless track under coupling effect of temperature gradient and train load was primarily attributed to shear stress. An evaluation index of “shear bond strength ≥2.50 MPa” was proposed and used to assess interlayer bonding performance of ballastless track in high-speed railway. Additionally, based on polymer modification technology, a method of using phenylpropylene and styrene-butadiene emulsions has been developed to improve the interlayer bonding behaviour of high-speed railway ballastless track. This work is expected to provide theoretical and technical support for a prolonged service life of high-speed railway ballastless track.

Prediction of fracture evolution in the TiN/Al thin films based on a full-field modelling approach

The classical approach to fracture simulation in a thin film for bioengineering applications neglects the underlying complex morphology of the deposited layer, leading to inaccurate numerical predictions. That may carry high risks during product development and its further exploitation, especially in biomedical applications. Therefore, here, we demonstrate the new approach to numerical investigation of the fracture evolution in pulsed laser-deposited (PLD) titanium nitride (TiN) thin films under loading conditions based on the full-field model of layer columnar morphology. We use the TiN film deposited on the aluminium (Al) substrate as a case study. Based on the nanoindentation test, we first determine the flow stress characteristics of the Al substrate and TiN/Al structure. An inverse analysis technique allowed us to precisely recalculate measured load–displacement values into the required stress–strain curve. Then, we developed a full-field model based on the digital material representation (DMR) concept for further investigation. The DMR was generated to replicate major morphological features of the deposited thin film identified under transmission electron microscop (TEM). Finally, we incorporated the TiN/Al full-field model into the finite element analysis with a cohesive zone approach for local analysis of fracture behaviour. Inverse analysis based on the developed direct model and experimental measurements allowed us to identify the parameters of the fracture model. As a result, we proved that the full-field model based on the digital material representation concept could be used for reliable predictions of local fracture development along the morphological features of the deposited thin film.

A theoretical model for evaluating the deterioration of mechanical properties of rockfill materials

The mechanical properties of rockfill materials deteriorate when subjected to different environmental factors. Accurately evaluating the deterioration effect on mechanical properties of rockfill materials is crucial for the lifecycle safety assessment of rockfill dams. In this study, we propose a theoretical model that can analyze the deterioration effect on stress and deformation characteristics of rockfill materials caused by weathering. Specifically, based on assumptions of geometric and breakage similarity, the stress and strain tensors of rockfill assemblies before and after deterioration can be derived from granular matter mechanics by introducing a deterioration coefficient. The deterioration coefficient defines the ratio between the grain crushing strength of deteriorated and undeteriorated rock grains, and can be obtained by single grain crushing tests. The deterioration coefficient is introduced into the Duncan-Chang EB model to quantitatively evaluate the deterioration effect on stress and deformation characteristics of rockfill materials. The triaxial test results of deteriorated and undeteriorated rockfill materials are used to verify the model. The results indicate a good agreement between the model predicted results and experimental results. Besides, the deteriorated stress and deformation characteristics of rockfill materials after cyclic wetting-drying are predicted by the theoretical model.