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Full hydraulic steering system adopted by mine electric-wheel dump truck is powered by steering hydraulic accumulator and steering hydraulic pump. Its actual steering response ability affected by road surface condition, steering oil pressure and flow, thus, it is a typical large inertia and time-varying execution system. Time-varying characteristics of the steering speed put forward time-varying coordination requirements for the lateral and longitudinal motion which indirectly restricted lateral motion ability of the unmanned mine truck. Speed planning and control without considering steering speed characteristics will result in poor coordination of lateral and longitudinal motion, which will lead to ineffective vehicle tracking. Firstly, this paper analyzes the key factors of time-varying response characteristics of the full hydraulic steering system based on its system principle. Secondly, the constraint of steering speed on the coordination of lateral and longitudinal motion is determined based on the deformation derivation of the truck kinematics model. Finally, combined with the pressure information of the steering accumulator, evaluation model of steering response capability and speed adjustment method in accordance with lateral and longitudinal cooperative constraints are established. Actual test results show that the designed speed adjustment method can achieve good tracking of the mine truck on the continuous limit curve path, with an average lateral error of 0.2 m, and ensure the continuous tracking ability of the mine electric-wheel dump truck on the complex curvature path.

Recycled steel fiber comes from the waste produced by machining. Adding recycled steel fiber into concrete can significantly enhance the toughness of concrete. In order to study the impact toughness of recycled steel fiber-reinforced concrete, the drop weight repeated impact experiment method was used to study the performance of recycled steel fiber-reinforced concrete under repeated impact load. Four kinds of recycled steel fiber-reinforced concrete samples with different volume contents were designed and made, and the loading impact experiments under five working conditions were carried out. Taking the drop weight and drop height as changing parameters, the corresponding blow counts of the first crack and sample failure under the impact of the drop hammer are recorded, and the ductility coefficients of different samples are calculated. The results show that the impact resistance of the sample decreases significantly with the increase of the drop weight and drop height. With the increase of recycled steel fiber content, the impact toughness of the sample increases obviously. The impact toughness of recycled steel fiber-reinforced concrete under standard loading conditions is the best.

Recycled rubber particles can be produced by using waste tires. Adding recycled rubber particles to concrete can form rubber concrete (RC). RC can not only reduce the amount of natural sand and reduce the cost of concrete but also improve the static compressive toughness of concrete. Adding steel fiber into RC can improve the strength of concrete. In order to study the compressive toughness of steel fiber rubber concrete (SFRC), rubber particles washed with NaOH are added to steel fiber reinforced concrete. This can enhance the bonding performance between the recycled rubber particles and concrete. The volume ratio of recycled rubber is 5, 10, and 15%. Prismatic and cubic test blocks were prepared and their compressive tests were carried out. The results show that the stress interaction between the rubber particles and steel fiber in concrete significantly improves the compressive strength, elastic modulus, and stress–strain relationship of concrete. The compressive toughness and ductility of concrete are improved. When the content of rubber particles is 15–20%, the compressive toughness of SFRC is improved most obviously. Through experiments, the toughness index and specific toughness of rubber steel fiber reinforced concrete are calculated, which explores a new way and method for studying the compressive toughness of similar recycled material concrete.

Recycled steel fiber (RSF)-reinforced concrete is not only an innovative research trend in the field of civil engineering materials, but also a new type of civil engineering composites under the trend of low-carbon development. This article deals with the experimental study of applying waste steel fibers to form recycled steel fiber concrete (RSFC). The main materials in this study are RSF, coarse and fine aggregate, fly ash, silica fume, and water reducer agent formed by machining surplus materials as the main materials. Three types of concrete were prepared. They were normal concrete, primary steel fiber concrete (PSFC), and RSFC with six different volume contents. The slump and air content of the three types of concrete are compared and analyzed. Then, the effects of the volume content of RSF on the cube compressive strength, splitting tensile strength, flexural strength, and axial compressive strength of RSFC are studied. Finally, the toughness of RSFC is discussed. The test results show that with the increase in the volume content of RSF, the slump of RSFC is significantly reduced, the compressive strength, tensile strength, and flexural strength are enhanced, the increase in tensile strength and flexural strength is significantly higher than the cube compressive strength, and the RSF has an obvious inhibitory effect on the development of concrete cracks which can obviously enhance the ductility and toughness of the concrete.

Objective: Studies have shown that chemokines can stimulate the migration and activation of microglia to cause chronic post-surgical pain (CPSP). However, the involvement of C-X-C motif chemokine receptor 2 (CXCR2) as a new chemotactic factor in regulating CPSP and its underlying mechanism remains unclear. This study is to investigate the role of CXCR2 in the development of CPSP and reveal the underlying mechanism. Material and Methods: A rat model of skin/muscle incision and retraction was established, and treated with or without SB225002 (a selective inhibitor of CXCR2). In addition, the primary microglia cells induced by lipopolysaccharide were applied as an in vitro model for CPSP and treated individually with si-negative control (NC), si-CXCR2, si-CXCR2+Interleukin (IL)-6 (an agonist of the janus kinase (JAK)/signal transducers and activators of transcription (STAT)3 signaling pathway), si-CXCR2+IL-6+si-NC, or si-CXCR2+IL-6+si-exchange protein 1 directly activated by cAMP (EPAC1). Results: Results from the database analysis showed that CXCR2 and JAK/STAT3 signaling pathway-related genes, including JAK1, STAT3, and EPAC1, were mainly involved in the development of CPSP. Inhibition of CXCR2 expression not only inhibited the reduction of foot pain threshold in CPSP models but also led to a decreased expression of CXCR2 and the phosphorylation levels of JAK and STAT3 in both animal and cell models. Furthermore, inhibition of EPAC1 expression can hinder the regulatory function of CXCR2. Conclusion: This study indicated that the high expression of CXCR2 activates the JAK1/STAT3 signaling pathway, enhances EPAC1 activation in microglial cells, and exacerbates CPSP. [ABSTRACT FROM AUTHOR]

To explore the axial compressive mechanical properties of steel tube recycled steel fiber reinforced concrete short columns (STRSFRCSCs), axial compression tests were conducted on ten STRSFRCSCs and two steel tube reinforced concrete short columns (STRCSCs), mainly analyzing the effects of recycled steel fiber (RSF) content, steel content, and concrete strength grade on their mechanical properties. The results showed that different RSF contents had no significant effect on the failure mode of the specimens, while the concrete strength grade and steel content had a significant effect on the failure mode. When the steel content was 2.84%, the specimens experienced shear failure, while when the steel content was 4.24%, they experienced waist drum failure. As the RSF content increased, the peak strain during the loading process of the specimens decreased, and the transverse deformation coefficient at the peak decreased. The addition of RSF significantly improved the ductility performance of the specimens. When the volume fraction of RSF was 2%, the bearing capacity of the specimens increased the most, reaching 13.4%, and the ductility coefficient gradually increased. The axial compressive bearing capacity and combined elastic modulus of the specimens increased with the increase in concrete strength grade, RSF content, and steel content. [ABSTRACT FROM AUTHOR]

Purpose: We assessed the effects of tracheostomy timing (early vs. late) on outcomes among adult patients receiving mechanical ventilation. Methods: PubMed, Embase, Web of Science and Cochrane Library were searched to identify relevant RCTs of tracheotomy timing on patients receiving mechanical ventilation. Two reviewers independently screened the literature, extracted data. Outcomes in patients with early tracheostomy and late tracheostomy groups were compared and analyzed. Meta-analysis was performed using Stata14.0 and RevMan 5.4 software. This study is registered with PROSPERO (CRD42022360319). Results: Twenty-one RCTs were included in this Meta-analysis. The Meta-analysis indicated that early tracheotomy could significantly shorten the duration of mechanical ventilation (MD: -2.77; 95% CI -5.10~ -0.44; P = 0.02) and the length of ICU stay (MD: -6.36; 95% CI -9.84~ -2.88; P = 0.0003), but it did not significantly alter the all-cause mortality (RR 0.86; 95% CI 0.73~1.00; P = 0.06), the incidence of pneumonia (RR 0.86; 95% CI 0.74~1.01; P = 0.06), and length of hospital stay (MD: -3.24; 95% CI -7.99~ 1.52; P = 0.18). Conclusion: In patients requiring mechanical ventilation, the tracheostomy performed at an earlier stage may shorten the duration of mechanical ventilation and the length of ICU stay but cannot significantly decrease the all-cause mortality and incidence of pneumonia. [ABSTRACT FROM AUTHOR]

A meta‐analysis research was implemented to appraise the effect of topical antibiotics (TAs) on the prevention and management of wound infections (WIs). Inclusive literature research was performed until April 2023, and 765 interconnected researches were reviewed. The 11 selected researches included 6500 persons with uncomplicated wounds at the starting point of the research: 2724 of them were utilising TAs, 3318 were utilising placebo and 458 were utilising antiseptics. Odds ratio (OR) and 95% confidence intervals (CIs) were utilised to appraise the consequence of TAs on the prevention and management of WIs by the dichotomous approach and a fixed or random model. TAs had significantly lower WI compared with placebo (OR, 0.59; 95% CI, 0.38–0.92, p = 0.02) and compared with antiseptics (OR, 0.52; 95% CI, 0.31–0.88, p = 0.01) in persons with uncomplicated wounds (UWs). TAs had significantly lower WIs compared with placebo and antiseptics in persons with UWs. However, caution needs to be taken when interacting with their values because of the low sample size of some of the chosen researches and low number of researches found for the comparisons in the meta‐analysis. [ABSTRACT FROM AUTHOR]

When large deformation of the tunnel occurred in the swelling rock, the large deformation treatment will not only greatly delay the construction time, but also lead to instability or even collapse of the tunnel. Selecting the reasonable timing for large deformation initial support replacement can solve this problem effectively. Based on the LiRang tunnel, the deformation and stress of the tunnel in anhydrite were analysed by FLAC software after excavation. Then replace the deformed first liner at different vault settlement value. The displacement and stress of surrounding rock were analysed when the model reaches equilibrium state again. The results showed that stress concentration at the arch wall and arch foot of the tunnel, and the stress release at the vault and invert is very large after excavation. If the large deformation was treatment when the crown settlement of the tunnel reaches 90% ~95% of the final predicted settlement value, the tunnel deformation and the final stress state could be in a small value. This study can provide a reference for the treatment of large deformation in the swelling rock tunnel.

Rockburst is a type of dynamic instability failure phenomenon and frequently brings huge losses to underground engineering projects such as mines and tunnels. In order to explore rockburst mechanisms and predict rockbursts better, relying on the background of Wulaofeng deep-buried highway tunnel, in situ stress measurement was performed using new wireless devices, and mechanics tests of surrounding rock samples taken from different burial depths were carried out. The rockburst mechanism was explored from the microscopic perspective based on the analysis of scanning electron microscopy (SEM). Rockburst tendency was judged comprehensively by a tendency analysis, grade prediction and numerical simulation. The result showed that the mechanical parameters of granite rocks in the deep-buried section were larger than those in the entrance section, and the fractured morphology mainly comprised sheet and monolithic block, corresponding to transgranular fracture and intergranular fracture. Rocks with few types of mineral cementation, good crystallization and small particle size differences had better energy storage and release characteristics. There was little difference in the rockburst tendency of rocks with different buried depths, but there were obvious differences in the rockburst grade. In the deep-buried section of the tunnel, the rockburst grade was of a moderate–heavy level and the rockburst risk at the vault and right spandrel of the cross section was more severe, which was basically consistent with the situation at the tunnel site. This study can provide a theoretical basis for the prevention and control of rockbursts in Wulaofeng tunnel and other similar engineering projects. [ABSTRACT FROM AUTHOR]