•A fully closed water pressure exerting device for non-circular section tunnel is invented.•The deformation characteristics of different lining structures are revealed.•The ultimate bearing water ...head of different lining structures are proved.•Compression-shear failure on the inclined section at the bottom of the wall is proposed.
It's a challenging technical problem at home and abroad that it is inevitable to build tunnels in aquifer with the improvement and development of railway network, particularly under the current stringent environmentally-friendly prerequisite. Therefore, the conventional principle “drainage is dominant and combination of drainage and blockage” should be updated with “blockage is dominant and drainage is limited”. Under this background, the mechanical characteristics for tunnel lining structure in aquifer needs to be studied urgently. A series of model experiments were performed to investigate the load-bearing mechanism of the underwater tunnel lining under water pressure. To investigate the load-bearing characteristics of different types of linings, a fully closed water pressure exerting device for a non-circular section tunnel was invented. A large-scale model experiment (1:30) under combined water and soil pressures was conducted to investigate the mechanical characteristics, deformation, stress distribution, crack development process, and failure mode of the mined-tunnel lining in aquifer. The experiment results indicated that for mined-tunnel lining with large section the key sections for controlling instability of both the drainage lining and the waterproof lining were the bottom of the wall and the inverted arch under the two experiment conditions. One had only water pressure, and the other had a variable water pressure and constant soil pressure. For both types of lining structures, the bottom of the wall and the inverted arch appeared cracks and damaged in turn. Furthermore, based on unified strength theory, it was found that compression-shear failure on the inclined section will occur at the bottom of the wall under the action of water pressure, which was different from the compression bending failure at other parts. In this research, the reasonable ultimate water head of the waterproof lining (thick invert, or large invert) and the drainage lining for the high-speed railway tunnel of Class V surrounding rock with a design speed of 350 km/h was proposed which could provide reference for similar tunnel engineering.
Bivalirudin as an anticoagulant reduces bleeding after percutaneous coronary intervention (PCI), while its impact in elderly Chinese patients treated with PCI needs more evidence. This study aimed to ...compare the clinical outcomes between bivalirudin and heparin in elderly Chinese patients treated with PCI. This cohort study retrieved data of 1,286 elderly patients treated with PCI who used bivalirudin (bivalirudin group, N = 493) or heparin (heparin group, N = 793) as anticoagulants. Net adverse clinical events (NACEs) (primary endpoint), major adverse cardiac and cerebral events (MACCEs), bleeding, and major bleeding within 30 days after PCI treatment were recorded for analysis. Our study illustrated that NACEs (12.4% vs. 17.4%, P = 0.015), bleeding (6.7% vs. 12.1%, P = 0.002), and major bleeding (2.2% vs. 6.6%, P < 0.001) were fewer in bivalirudin group compared to heparin group. No difference was found in MACCEs (7.5% vs. 9.6%,P = 0.200), and incidences of all-cause mortality (P = 0.257), cardiac mortality (P = 0.504), recurrent myocardial infarction (P = 0.423), ischemia-driven revascularization (P = 0.509), and stroke (P = 0.467), between bivalirudin group and heparin group. According to univariate logistic regression analyses, bivalirudin (vs. heparin) correlated with fewer NACEs (P = 0.016), bleeding (P = 0.002), and major bleeding (P = 0.001) in elderly patients treated with PCI, but not MACCEs (P = 0.202). After adjustment, bivalirudin (vs. heparin) was an independent factor for fewer NACEs odds ratio (OR): 0.619, P = 0.009, bleeding (OR: 0.499, P = 0.003), and major bleeding (OR: 0.342, P = 0.003) in these patients. In summary, bivalirudin achieves fewer NACEs, bleeding, and major bleeding, but not MACCEs, versus heparin in elderly patients treated with PCI, which is verified in the multivariate model.
Steel fibers are widely used because they can effectively improve the tensile, compressive and flexural properties of concrete structures. The selection of steel fiber dosage and aspect ratio at high ...temperature has an important impact on the flexural toughness of concrete components post-fire. In this paper, discussions are made on the simulated fire test in compliance with the ISO 834 standard to study the steel fiber-reinforced concrete (SFRC) components post-fire. The research reveals the influence of two commonly used steel fiber aspect ratios (50, 70) and steel fiber dosages (30 kg/m3, 40 kg/m3, 45 kg/m3) on the changes of the internal temperature field, the initial crack flexural strength and the flexural toughness of the SFRC components under a single-side fire. Moreover, combined with the four-point flexural test of the SFRC components post fire, the research also describes the damage of high temperatures to the flexural toughness of SFRC components, and suggests a calculation formula for SFRC thermal conductivity by way of the numerical inversion method. The results of this study have verified that the incorporation of steel fiber into concrete helps to reduce its internal thermal stress difference and improve the crack resistance and fire resistance of the concrete. Moreover, under high temperature conditions, the concrete component added with the steel fiber in an aspect ratio of 70 and a dosage of 45 kg/m3 increased their initial crack flexural strength by 56.8%, higher than that of plain concrete components, and the loss of equivalent flexural strength and flexural toughness of SFRC post fire was only 45.2% and 13.6%, respectively. The proposed calculation formula of thermal conductivity can provide a reference for a numerical simulation study of the temperature field of SFRC components in a high temperature environment.
The ERP components and variations of spatial complexity or functional connectivity are two distinct dimensions of neurophysiological events in the visual Go/Nogo task. Extensive studies have been ...conducted on these two distinct dimensions; however, no study has investigated whether these two neurophysiological events are linked to each other in the visual Go/Nogo task. The relationship between spatial complexity of electroencephalographic (EEG) data, quantified by the measure omega complexity, and event-related potential (ERP) components in a visual Go/Nogo task was studied. We found that with the increase of spatial complexity level, the latencies of N1 and N2 component were shortened and the amplitudes of N1, N2, and P3 components were decreased. The anterior Go/Nogo N2 effect and the Go/Nogo P3 effect were also found to be decreased with the increase of EEG spatial complexity. In addition, the reaction times in high spatial complexity trials were significantly shorter than those of medium and low spatial complexity trials when the time interval used to estimate the EEG spatial complexity was extended to 0∼1,000 ms after stimulus onset. These results suggest that high spatial complexity may be associated with faster cognitive processing and smaller postsynaptic potentials that occur simultaneously in large numbers of cortical pyramidal cells of certain brain regions. The EEG spatial complexity is closely related with demands of certain cognitive processes and the neural processing efficiency of human brain.
The reaction times, the latencies/amplitudes of event-related potential (ERP) components, the Go/Nogo N2 effect, and the Go/Nogo P3 effect are linked to the electroencephalographic (EEG) spatial complexity level. The EEG spatial complexity is closely related to demands of certain cognitive processes and could reflect the neural processing efficiency of human brain. Obtaining the single-trial ERP features through single-trial spatial complexity may be a more efficient approach than traditional methods.
Panum's limiting case is one of the typical configurations of monocular occlusion region. The matching rule of Panum's limiting case is the key to understanding how monocular occlusion region ...produces stereopsis. There are currently two main views on the matching rule of Panum's limiting case, namely double fusion and uniqueness constraint. This paper further discusses its matching mechanism on the basis of previous studies.
In this study, fold line Panum's stimuli were used to study the matching rule of Panum's limiting case. In Experiment 1, fixation position was adopted to present the stimulus in a short time to explore the matching rules in Panum's limiting case. In Experiment 2, the effect of fixation position on Panum's limiting case matching results was further investigated.
The results of Experiment 1 show that when stimuli are presented in a short period of time, the reported result that a single feature in one eye may be matched alternately with two features in the other eye. This matching rule is called "fast alternative matching" in this article. The results of Experiment 2 results show that the position of the fixation could affect the matching result of participants.
In conclusion, the matching rule of Panum's limiting case is fast alternative matching, and the matching result is related to the attention state of the participant. These results not only provide a new perspective for matching rules in Panum's limiting case, but also show that depth perception results in stereopsis can be influenced by top-down cognitive processing. This study provides a theoretical basis for studying the formation of stereopsis in the monocular region to a certain extent. In summary, the matching rule of Panum's limiting case is fast alternative matching. In previous studies, the perceived result of double fusion may be caused by fast alternative matching. Also, the matching results are related to the participant's state of attention, which suggests that the depth perception results of stereopsis are influenced by top-down cognitive processing.
Growing evidences indicate that age plays an important role in the development of mental disorders, but few studies focus on the neuro mechanisms of generalized anxiety disorder (GAD) in different ...age groups. Therefore, this study attempts to reveal the neurodynamics of Young_GAD (patients with GAD under the age of 50) and Old_GAD (patients with GAD over 50 years old) through statistical analysis of multidimensional electroencephalogram (EEG) features and machine learning models. In this study, 10-min resting-state EEG data were collected from 45 Old_GAD and 33 Young_GAD. And multidimensional EEG features were extracted, including absolute power (AP), fuzzy entropy (FE), and phase-lag-index (PLI), on which comparison and analyses were performed later. The results showed that Old_GAD exhibited higher power spectral density (PSD) value and FE value in beta rhythm compared to theta, alpha1, and alpha2 rhythms, and functional connectivity (FC) also demonstrated significant reorganization of brain function in beta rhythm. In addition, the accuracy of machine learning classification between Old_GAD and Young_GAD was 99.67%, further proving the feasibility of classifying GAD patients by age. The above findings provide an objective basis in the field of EEG for the age-specific diagnosis and treatment of GAD.
This research paper systematically investigates the combined influence of fly ash, cementitious capillary crystalline waterproofing (CCCW) materials, and polypropylene fibers on the mechanical ...properties and impermeability of concrete through comprehensive orthogonal tests. Microscopic morphological changes in the concrete induced by different composite materials are examined via scanning electron microscopy (SEM) and X-ray diffraction (XRD) testing. The objective is to facilitate a beneficial synergetic interaction among these materials to develop highly permeable, crack-resistant concrete. Key findings of this study are: (1) The study unveils the impact of the concentration of three additive materials on the concrete’s compressive strength, tensile strength, and penetration height, thereby outlining their significant influence on the mechanical properties and impermeability of the concrete; (2) An integrated scoring method determined the optimal composite dosage of three materials: 15% fly ash, 2% CCCW, and polypropylene fibers at 1.5 kg/m3. This combination increased the concrete’s compressive strength by 12.5%, tensile strength by 48.4%, and decreased the average permeability height by 63.6%; (3) The collective introduction of these three materials notably augments the hydration reaction of the cement, resulting in denser concrete microstructure, enhanced bonding between fibers and matrix, and improved concrete strength and durability.
As a new type of pre-reinforcement material for tunnel faces, glass fiber-reinforced polymer (GFRP) bolts can effectively and safely improve the stability of tunnel faces in soft surrounding rocks ...and speed up excavation. Therefore, in this paper, systematic research is carried out on the bond strength of GFRP bolts in tunnel faces and their relative pre-reinforcement parameters. Firstly, the effects of rebar diameter, anchorage length, and mortar strength on the bonding properties of GFRP bars were studied by indoor pull-out tests. The bond strength-slip curves under different working conditions were obtained, and the curves showed that the ultimate bond strength between GFRP bars and mortar was negatively correlated with the diameter of GFRP bars but positively correlated with the strength of the mortar. In addition, the increase in anchorage length led to a reduction in bonding strength. Secondly, inverse analysis was used to analyse the mechanical parameters of the bond performance of the anchor bars by the finite difference software FLAC3D, and the results indicated that 1/5 of the compressive strength of the GFRP bar grouting body can be taken as the ultimate bond strength to calculate the cohesive strength of the grout. Additionally, the formula of GFRP bar grouting body stiffness was revised. Finally, based on the results of laboratory tests and the inverse analysis, the numerical simulation analysis results showed that the optimal reinforcement configuration for a shallow buried tunnel face surrounded by weak rock is to use GFRP bars with a length of 17 m arranged in the center circle of the tunnel face with a reasonable reinforcement density of 1.0 bolt/m
. The calculation formula of the stiffness and cohesion strength of the GFRP bar grouting body and the reinforcement scheme proposed in this paper can provide a reference for the construction of shallowly buried rock tunnels in soft surrounding rock.
In this study, the relationship between four expansion indices and the expansion potential of gypsum rock was studied; on this basis, a criterion for judging expansion potential is established for ...gypsum rock. The results show that the free expansion rate is unsuitable for grading gypsum rocks’ expansion potential. Setting the gypsum rock in the Wuzhishan tunnel as the research subject, the ultimate expansion rate is 24.28% on the 7th day and 34.08% on the 30th day; the ultimate expansion rate on the 7th day of the indoor rock sample can be estimated by the fitting formula on the 30th day, the ultimate expansion force is 304.51 kPa, and the BET-specific surface area is 6.31 m2/g. The ultimate expansion ratio and BET-specific surface area have an excellent linear relationship with the ultimate expansion force. Setting the ultimate expansion force, ultimate expansion ratio and BET-specific surface area as the standard, the criterion for judging the expansion potential of gypsum rock is determined, which is more convenient and accurate than existing standards. The standard in this paper can predict the potential disasters that may occur in underground engineering.
Driving fatigue is the main cause of traffic accidents, which seriously affects people's life and property safety. Many researchers have applied electroencephalogram (EEG) signals for driving fatigue ...detection to reduce negative effects. The main challenges are the practicality and accuracy of the EEG-based driving fatigue detection method when it is applied on the real road. In our previous study, we attempted to improve the practicality of fatigue detection based on the proposed non-hair-bearing (NHB) montage with fewer EEG channels, but the recognition accuracy was only 76.47% with the random forest (RF) model. In order to improve the accuracy with NHB montage, this study proposed an improved transformer architecture for one-dimensional feature vector classification based on introducing the Gated Linear Unit (GLU) in the Attention sub-block and Feed-Forward Networks (FFN) sub-block of a transformer, called GLU-Oneformer. Moreover, we constructed an NHB-EEG-based feature set, including the same EEG features (power ratio, approximate entropy, and mutual information (MI)) in our previous study, and the lateralization features of the power ratio and approximate entropy based on the strategy of brain lateralization. The results indicated that our GLU-Oneformer method significantly improved the recognition performance and achieved an accuracy of 86.97%. Our framework demonstrated that the combination of the NHB montage and the proposed GLU-Oneformer model could well support driving fatigue detection.
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