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Aiming at the problem that roof deformation of cross fault roof cutting and pressure relief self-formed roadway is large and difficult to support, the mechanism of roof deformation of self-formed roadway in cross fault roof cutting and pressure-relieving roadway is studied based on the engineering background of the transport channeling of No. 11101 face in the eastern district of Qipanjing Coal Mine, and the effect of the support method of “roof cutting and pressure relief + constant resistance anchor cable” on roof deformation control of self-formed roadway in cross-fault roof cutting and pressure relieving roadway is studied. A mechanical analysis model was established to study the influence of the relevant parameters of the roof on the direct roof stress of the roadway, and the deformation process of the roof of the roadway was divided into four stages. The calculation method of each stage and the total vertical displacement of the roof of the roadway were studied and the calculation formula was given, and the relevant parameters were substituted into the formula to solve the vertical displacement of the roof of the roadway across the fault. 3DEC numerical simulation software was used to establish the numerical calculation model of self-formed roadway with cross fault roof cutting and pressure relief, and the stress-strain evolution law of roadway roof near the fault and the control effect of constant resistance anchor cable were studied. The research results show that the error between the numerical simulation and theoretical analysis data of roadway roof deformation is 1.14% and 4.04%, respectively. The constant resistance anchor cable can effectively reduce the deformation of roadway roof. Compared with the non-constant resistance anchor cable model, the vertical displacement of roof on slit side of upper wall roadway is reduced to 16.8%, and the vertical displacement of roof on slit side of lower wall roadway is reduced to 50.7%. The roof of upper and lower wall roadway will have different degree of stress concentration in the process of mining through the measurement section of roadway, and the vertical stress concentration value of upper wall roadway roof is larger than that of lower wall roadway, which is 5.72 MPa and 4.48 MPa respectively. The constant resistance anchor cable can reduce the deformation rate of roadway roof near the fault, and control the deformation of roadway roof jointly with the gravel wall after the filling is completed. By comparing the displacement monitoring data of surrounding rock along the channel of No. 11101 face transport with the calculation results of the theoretical model, the error is less than 10%, which proves that the support method of “roof cutting and pressure relief + constant resistance anchor cable” has a good control effect on the roof deformation of cross fault roadway.

Abstract Background Commencing work at an early age has been linked to various risk factors for coronary heart disease (CHD), such as shift work and intensive job strain. However, the relationship between starting work too early and CHD risk remains largely unclear. We examined the association between age at job initiation and the risk of CHD. Methods UK Biobank participants aged 38 to 70 years without cardiovascular disease who provided data on their age at job initiation were included. The primary outcome was CHD, which was ascertained using hospital and death records. The hazard ratios (HRs) and 95% confidence interval (CIs) for the association between age at job initiation and CHD were calculated using multivariable Cox regression. Results Of the 501,971 participants, 114,418 eligible participants were included in the final analysis. The median age at job initiation was 19.0 years. During the mean follow-up of 12.6 years, 6,130 (5.4%) first CHD events occurred. We observed that age at job initiation was inversely associated with CHD (HR 0.98, 95% CI 0.97–0.99), and the association was potentially J-shaped. The HRs for the

With the rapid development of industrial automation and power electronics, the requirements for electrical contact materials are increasing. However, traditional electrical contact materials encountered significant bottlenecks in terms of performance enhancement and production environmental friendliness. Therefore, this paper proposes a new material design idea that utilizes π-π interactions between graphene and compounds with conjugated structures in order to achieve uniform dispersion of graphene in the metal matrix and thus enhance the performance of composites. Based on this design idea, we used nicotinic acid, which has a conjugated structure and is safe, as the complexing agent, and successfully prepared high-quality silver-graphene (Ag-G) composite coatings with graphene uniformly dispersed in the metal matrix on copper substrates by composite electrodeposition technique. Subsequently, the mechanical properties of composite coatings were investigated by hardness test and X-ray diffractometer, and the tribological properties of the composite coatings and the comprehensive performance under the current carrying conditions were systematically evaluated by using friction and wear tester and load key life tester. The results show that the Ag-G composite coatings have significant advantages in mechanical, tribological, and current carrying conditions. This result not only verifies the feasibility of the design idea of the material, but also provides a new direction for the research and development of electrical contact materials.

In the present study, we tried to understand the spatially distributed damage in sandstone samples under the coupled stress-freeze-thaw (SFT) conditions. Firstly, uniaxial compressive stresses (i.e. 0 MPa, 10 MPa, 20 MPa, and 25 MPa) were applied to the samples, and then freeze-thaw (FT) cycles (0, 8, 16, and 24) were performed on the uniaxially stressed samples to realize the SFT coupling. Next, real-time CT scanning was conducted to observe the induced damage. The total porosity was introduced to quantitatively evaluate the damage degree. The local porosity variation, with the distance from the center of the sandstone sample, was analyzed to understand the spatial distribution of damage. Finally, the coupling effects of SFT on the damage gradient were discussed. The results indicate that the porosity rises with FT cycles, and the applied stresses can accelerate the increase in porosity. The damage increases exponentially with the distance from the center of the sample. The damage presents a spatial gradient distribution, not the commonly used uniform distribution in various studies. The damage gradient increases with FT cycles, and the increasing rate in damage gradient decreases at uniaxial stress of 0 MPa and 10 MPa first, but the increasing rate in damage gradient increases with FT cycles then at stress increasing to 20 MPa.

Anthropogenic and extreme climate disasters cause ecological changes in natural rivers and lakes, increasing the risk of starvation in yellowcheek (Elopichthys bambusa). Therefore, the impact of starvation on the metabolism and wild population of yellowcheek should be explored. In this study, we used transcriptome sequencing technology to analyze the effects of short (8 d) and long-term (28 d) starvation on the liver transcriptome, growth, and serum indicators of yellowcheek. Our results showed that short-term starvation significantly reduced the visceral weight and viscera index of yellowcheek. Long-term starvation significantly reduced the body weight and Fulton’s condition factor, and it maintained significant reductions in visceral weight and viscera index. These results indicate that glycogen is the preferred energy source, rather than muscle protein, under starvation. Short-term starvation limited N-glycan and fatty acid biosynthesis, fatty acid elongation in the endoplasmic reticulum in the liver, and upregulated fatty acid degradation. However, long-term starvation alleviated the reduction in N-glycan and fatty acid biosynthesis caused by early starvation, and it significantly reduced fatty acid elongation in the mitochondria, as well as fatty acid degradation. These results provide important experiment information for assessing the starvation levels and nutritional status of wild yellowcheek.

In this study, we attempted to investigate the spatial gradient distributions of thermal shock-induced damage to granite with respect to associated deterioration mechanisms. First, thermal shock experiments were conducted on granite specimens by slowly preheating the specimens to high temperatures, followed by rapid cooling in tap water. Then, the spatial gradient distributions of thermal shock-induced damage were investigated by computed tomography (CT) and image analysis techniques. Finally, the influence of the preheating temperature on the spatial gradients of the damage was discussed. The results show that the thermal shock induced by rapid cooling can cause more damage to granite than that induced by slow cooling. The thermal shock induced by rapid cooling can cause spatial gradient distributions of the damage to granite. The damage near the specimen surface was at a maximum, while the damage inside the specimen was at a minimum. In addition, the preheating temperature can significantly influence the spatial gradient distributions of the thermal shock-induced damage. The spatial gradient distribution of damage increased as the preheating temperature increased and then decreased significantly over 600 °C. When the preheating temperature was sufficiently high (e.g. 800 °C), the gradient can be ignored.

In order to improve the applicability and prediction accuracy of the existing simulation test methods of vehicle tractive performance on sandy soil, the off-road tire model using the discrete element method (DEM) under each operating condition is separately established in this paper. The contact parameters of DEM model are calibrated by rubber-sand friction test and soil bin test combined with corresponding simulation test. On this basis, the tire-sand simulation model is calculated under straight and inclining driving conditions, and the variation law of drawbar pull, torque, tractive efficiency and sinkage is obtained. This paper proves the feasibility of DEM simulation in studying vehicle tractive performance, and also provides a systematic parameter calibration method for improving the accuracy of DEM simulation, which is of great significance to enrich vehicle testing methods.

Most existing path-planning algorithms are applied in either trafficable environments or non-trafficable environments. Off-road vehicles (ORVs) are often faced with a mix of trafficable and non-trafficable environments. Therefore, trafficability should be considered in path planning for ORVs. Conventional ant colony algorithms (ACAs) are prone to stagnation and often fail to reach the optimal path. To address these problems, an improved ACA that considers trafficability was proposed in this study, which improved the pheromone distribution rules and adaptively adjusted the pheromone volatility coefficient. Based on this improved ACA, a multilevel adaptive path-planning model was proposed to solve path-planning problems with various scales of area. Experiments and comparative studies revealed that the improved ACA was applicable to path-planning problems in complex environments and achieved better performance and a higher computing efficiency than conventional counterparts.

Soil–wheel interaction under cornering and slip conditions (SWICS) has a significant impact on the steering performance of off-road vehicles. In order to analyze the six-dimensional wheel forces in SWICS, a SWICS model based on the analytical method and the discrete element method (DEM) is developed in this paper. First, the modeling process of SWICS using the analytical method was detailed to predict the six-dimensional wheel forces in SWICS. The SWICS was then modeled using the DEM, which involved the following steps: (a) establishment of tire geometry, (b) selection of particle parameters, (c) parameter calibration, and (d) particle generation. Finally, DEM simulations were carried out for different slip angles and slip ratios under three loads, and the results were compared with those of the analytical model. The results show that the SWICS DEM model in this paper maintains a good fit with the analytical model, validating the efficiency of the DEM model and the parameter calibration method. The slip angle has a great influence on the lateral force, overturning moment, and aligning moment and a smaller impact on the normal force, drawbar pull, and rolling resistance moment. The slip ratio promotes an increase in the drawbar pull and rolling resistance moment but reduces the value of the lateral force and aligning moment. The research in this paper provides a DEM modeling approach and an analysis method for solving mechanical problems with different dimensions in SWICS, which will help improve the performance of off-road vehicles.

The regenerative hydraulic electric suspension (RHES) is a new type of energy regeneration damper system based on the principle of vibration energy harvesting. This system can recover the vibration energy of suspension dissipated in the form of thermal energy when vehicle travels on the road. In previous studies about RHES system, the vehicle suspension displacement is defined as varieties of periodic waves, such as sinusoidal and so on. The energy harvesting performance of damper system can be explained and evaluated to some extent, but the influence of the actual excitation condition of the road is not fully considered when studying the RHES. This paper builds models of road profiles, quarter car and power regeneration based on the proposed RHES system. Furthermore, the change laws of performance with the varies of road class, motor displacement, accumulator capacity and electrical load are summarized and the corresponding optimization suggestions are proposed, which realize the prediction and evaluation of RHES system performance under the excitation of different road profiles. Simulation suggests that this system can recover 100-400 W of power under road excitation. The findings of system analysis indicate that the component design can satisfy the damping characteristics and power performance required for specific application. The results also show that adjusting the electrical load and accumulator capacity is highly beneficial for controlling suspension behaviours, improving system reliability and increasing power regeneration.

Differences in stiffness constitute an extremely important aspect of the mechanical differences between cancer cells and normal cells, and atomic force microscopy (AFM) is the most commonly used tool to characterize the difference in stiffness. However, the process of mechanical characterization using AFM has been controversial and the influence of the membrane tension on AFM measurement results was often ignored. Here, a physical model involving a simultaneous consideration of the effects of the cell membrane, cytoskeleton network and cytosol was proposed. We carried out a theoretical analysis of AFM force relaxation curves, and as a result solved many of the remaining controversial issues regarding AFM-based mechanical characterization of cells, and provided a quantitative solution for the membrane tension measured using AFM indentation experiments for the first time. From the results of experiments on cells with different adherent shapes and different pairs of normal cells and cancer cells, we found additional force provided by membrane tension to be the main component of the force applied to the AFM probe, with decreased cell membrane tension being the essential reason for the greater softness of cancer cells than of normal cells. Hence, regulating membrane tension may become an important method for regulating the behavior of cancer cells.

The steering performance of off-road tires on sandy soil has a great influence on the maneuverability of the vehicle, which has long been studied by scholars. However, the discrete element method (DEM) modeling of tire steering on sand is still lacking. In this paper, an off-road tire steering model on sandy soil is established by using the discrete element method, and the parameters of the sandy soil model are calibrated based on the triaxial compression test and inclined plate experiment. Then, the parameters of the sandy soil model are verified by the reduced-scale single wheel soil bin test under a straight-driving condition. Finally, the influence of the steering radius, roll angle, roll angle, and slip rate on the tire steering process is studied. The results show that a reduction in the steering radius has a slight influence on the drawbar pull and driving torque but a greater influence on the growth of the lateral force, the aligning torque, and the reduction in sinkage. The slip rate and sideslip angle play an important role in drawbar pull, drive torque, lateral force, and torque. The roll angle has a small influence on the drawbar pull and driving torque but a greater influence on the lateral force and the aligning torque.

The soil ground with low moisture content has the mechanical properties of low viscosity and high friction, which have a great influence on the traveling of a tracked vehicle. In this paper, a movement model of the rigid track on low moisture soil is established based on the discrete element method (DEM) simulation. The soil simulation model was verified by the triaxial compression test. The traction simulation of the track under different vertical stress was carried out, and the traction performance of the track was analyzed by combining with the results of the soil bin test. The analysis shows that the tractive effort increases with the increase in vertical stress. The tractive effort distribution of the track is basically the same as the shape of the bottom of the track, and the tractive effort on both sides of the track cannot be ignored. The average error of tractive effort in simulation is 3.94%. DEM simulation can reproduce the mechanical properties and the discontinuous nature of low moisture soil particles under dynamic load, which is suitable for the numerical study of the interaction between the track and soil.

This study investigated the effects of freezing temperature under freeze-thaw cycling conditions on the mechanical behavior of sandstone. First, the sandstone specimens were subjected to 10-time freeze-thaw cycling treatments at different freezing temperatures (−20, −40, −50, and −60 °C). Subsequently, a series of density, ultrasonic wave, and static and dynamic mechanical behavior tests were carried out. Finally, the effects of freezing temperature on the density, P-wave velocity, stress–strain curves, static and dynamic uniaxial compressive strength, static elastic modulus, and dynamic energy absorption of sandstone were discussed. The results show that the density slightly decreases as temperature decreases, approximately by 1.0% at −60 °C compared with that at 20 °C. The P-wave velocity, static and dynamic uniaxial compressive strength, static elastic modulus, and dynamic energy absorption obviously decrease. As freezing temperature decreases from 20 to −60 °C, the static uniaxial compressive strength, static elastic modulus, dynamic strength, and dynamic energy absorption of sandstone decrease by 16.8%, 21.2%, 30.8%, and 30.7%, respectively. The dynamic mechanical behavior is more sensitive to the freezing temperature during freeze-thawing cycling compared with the static mechanical behavior. In addition, a higher strain rate can induce a higher dynamic strength and energy absorption.

Abstract Background Wharton’s jelly-derived mesenchymal stem cells (WJ-MSCs) are a novel and promising strategy for tissue engineering because of their ability to differentiate into many cell types. We characterized the differentiation of WJ-MSCs into endometrial epithelial cell (EEC)-like and endometrial stromal cell (ESC)-like cells and assessed the effect of 17β-estradiol and 8-Br-cAMP on the differentiation system. Methods WJ-MSCs were treated in two ways to differentiate into EEC-like and ESC-like cells respectively: cocultured with ESCs in control/differentiation medium (17β-estradiol, growth factors); and cultured in control/differentiation medium (8-Br-cAMP alone or 8-Br-cAMP plus 17β-estrogen and growth factors). Three signaling pathway inhibitors (SB203580, PD98059, H89) were used to investigate the mechanism of WJ-MSC differentiation into ESC-like cells. Immunofluorescence, western blot and flow cytometry analyses were used to analyze expression of epithelial markers and stromal cell markers. Enzyme-linked immunosorbent assays were used to test the production of secretory proteins associated with the differentiation of ESC-like cells. Results 17β-estradiol at 1 μM downregulated vimentin and CD13 and upregulated cytokeratin and CD9 proteins, promoting the differentiation of WJ-MSCs into EEC-like cells in the coculture system. 8-Br-cAMP at 0.5 mM upregulated vimentin and CD13 and downregulated CK and CD9, promoting the differentiation of WJ-MSCs into ESC-like cells. Prolactin (PRL) and insulin-like growth factor-binding protein 1 (IGFBP1) were upregulated and the protein kinase A (PKA) signaling pathway was activated, whereas extracellular signal-regulated (ERK)1/2 and p38 mitogen-activated protein kinase (MAPK) were not affected. Conclusions 17β-estradiol at 1 μM is a good inducer for facilitating the differentiation of WJ-MSCs into EEC-like cells. 8-Br-cAMP plus estrogen and growth factors can induce the differentiation of WJ-MSCs into ESC-like cells. During the differentiation of WJ-MSCs into ESC-like cells, PRL and IGFBP1 were upregulated by the treatment and the PKA signaling pathway was activated, whereas ERK1/2 and p38 MAPK were not affected. These findings suggest a promising approach to the treatment of endometrial damage and other endometrial diseases and suggest new applications for WJ-MSCs in clinical practice.

Abstract A series of clinical trials have confirmed the correlation between vascular calcification (VC) and cardiovascular events and mortality. However, current treatments have little effects on the regression of VC. Potent and illustrative mechanisms have been proven to exist in both bone metabolism and VC, indicating that these two processes share similarities in onset and progression. Multiple osteoblast-like cells and signaling pathways are involved in the process of VC. In this review, we summarized the roles of different osteoblast-like cells and we emphasized on how they communicated and interacted with each other using different signaling pathways. Further studies are needed to uncover the underlying mechanisms and to provide novel therapies for VC.

As a semi-active control device, the magnetorheological (MR) damper has received much praise for its great controllability, quick response, and lower input power. However, the problem of liquid leakage arises after its long-term service, severely affecting its performance and service life. To solve this problem, this paper proposes fully vulcanizing and consolidating viscoelastic material, the cylinder barrel and the piston rod, which replaces the traditional dynamic seal with a static seal, and developing a new leak-proof MR damper. Considering that viscoelastic material has a certain energy dissipation and fluid-structure interaction with MR fluid, the correction factor of the pressure gradient is introduced to establish the mechanical model of the leak-proof MR damper which is to be tested. The testing result shows that warpage deformation of viscoelastic material weakens the damping force of the MR damper and the weakening effect increases with current intensity. Given the influence of current intensity on the correction factor, the complete mechanical model of the leak-proof MR damper is obtained on the basis of the verified model. Through the comparison between the theoretical calculation curve and the test curve, the revised mechanical model is found to well reflect the mechanical properties of the leak-proof MR damper.

With the increasingly prominent energy issues, regenerative shock absorber has attracted intensive attention in last two decades for the development of structure design. However, the researchers sometimes concentrate on conceptual designs without considering optimal parameter refinements. This paper proposes a regenerative shock absorber called the “hydraulic electric regenerative shock absorber (HERSA)” which includes an analytical regeneration performance parameters optimisation approach to promote the regeneration efficiency and regenerated power. The developed HERSA model is able to convert oscillatory motion into unidirectional rotary motion through the alteration of hydraulic flow while recovering power by a generator. The proposed model is also capable of obtaining the optimal parameters at certain condition, as well as providing the flexibility of different component combinations to match specific system need. The results demonstrate that the proposed model can effectively decide the optimal parameters in the system, and also the recoverable power can achieve average power of 331 W at 1 Hz-25 mm sinusoidal excitation in the system, which is approximately 65% efficiency. This study can be further used to guide prototype design in future study.

The tire tread pattern affects driving significantly on icy roads, and different kinds of rubber pattern mean different friction coefficients when moving on the ice surface. Based on the latest friction test rig, a simulation method of such tests was created. Therefore, the continuous sampling at low slip velocity was proposed. During the sampling, the typical pattern of the rubber specimen was employed. The friction test of the tire tread specimen on the ice surface was implemented with different slip velocities and pressure, and the results were fitted and analyzed. To research the effect of tire tread on the friction coefficient, the rubber ratio parameter (the ratio of the rubber contact area to the total contact area) was given for proper evaluation. It is found that rubber as the major component of the tire possesses a special friction property, which is against Coulomb’s law. In addition to that, the friction coefficient of rubber is influenced by the contact state to a great extent, especially in some extreme conditions. The experiment of rubber friction on ice can serve as an important reference for the study on tire mechanical properties.

Flow and shock train development in a hypersonic inlet isolator at various wall surface temperatures, Tw, and freestream static temperatures, T8, were studied through numerical simulations. A non-dimensional parameter, Tw/T8, is used to characterize flow behaviors in hypersonic isolator. With the increase of Tw/T8, boundary-layer thickness increases and boundary-layer momentum thickness decreases at the entrance of isolator. Inside the isolator without the presence of backpressure, skin friction decreases with the increase of Tw/T8. The main cause is a lower velocity gradient near the wall at high temperature. A lower skin friction on high wall temperature results in a stronger separation with shock impingement. Under backpressure conditions, with the increase of Tw/T8, an upstream movement of the starting position of the shock train inside the isolator, an increase in the length of the shock train, and an increase in pressure coefficient on the wall surface are observed. [ABSTRACT FROM AUTHOR]