Search

This paper first systematically reviews the research on shield and TBM construction ventilation technology in the tunnel (hole) and coal mine roadway engineering; then, it briefly introduces the general situation of the main and auxiliary inclined shaft project of Kekegai Coal Mine and makes a theoretical analysis on the ventilation design principle and ventilation mode selection of the project according to the general situation of the project. Based on the above analysis, a variety of designs and comparisons of construction ventilation schemes are carried out, and it is decided that the two-stage single head forced ventilation scheme with replacement fan is adopted for both inclined shafts; then the selected ventilation scheme is checked theoretically; finally, the ventilation effect is tested. The field practice shows that the ventilation effect is good.

The fracture phenomenon of fastener clips occurs frequently in the sections with serious rail corrugation of high-speed railway, which brings huge potential safety hazards to track service and driving safety. In order to prevent the vibration fatigue fracture of fastener clips in high-speed railway, a dynamic vibration absorber (DVA) for clips is proposed in this paper to suppress the primary sensitive frequency of the corresponding resonant of clips. Firstly, based on the optimal design theory of DVA, a parameters design method of ring-shaped DVA suitable for clips is proposed. Secondly, the vibration characteristics of the high-speed railway fastener system are investigated, and the main reason for the fastener clips fracture is analyzed by simulation analysis combined with filed test. Then, focusing on the primary resonant frequency of clips, the vibration reduction effect of the ring-shaped DVA is analyzed. The results show that the ring-shaped DVA can change the natural frequency of the clip system, reduce the vibration response in the range of the original resonant frequency, and avoid the resonance phenomenon. Finally, the influences of mass ratio, frequency ratio, and damping ratio on the vibration reduction effect are analyzed, and the effectiveness of the parameters design method of ring-shaped DVA proposed in this paper is further proved. The research results can provide methodological support for the anti-breakage design of high-speed railway fastener clips. [ABSTRACT FROM AUTHOR]

Defect detection of track fasteners is a prerequisite for safe and reliable railroad operation. The traditional manual visual inspection method has been unable to meet the growing demand for railroad network inspection in China. To achieve the need for accurate, fast, and intelligent detection of rail fasteners, this paper proposes a rail fastener defect detection model based on improved YOLOv5s. Firstly, the convolutional block attention module (CBAM) is added to the Neck network of the YOLOv5s model to enhance the extraction of essential features by the model and suppress the information of minor features. Secondly, a weighted bidirectional feature pyramid network (BiFPN) is introduced to realize the multi-scale feature fusion of the model. Finally, the K-means++ algorithm is used to re-cluster the dataset to obtain the anchor box suitable for the fastener dataset and improve the positioning ability of the model. The experimental results show that the improved model achieves an average mean precision (mAP) of 97.4%, a detection speed of 27.3 FPS, and a model memory occupancy of 15.5 M. Compared with the existing target detection model, the improved model has the advantages of high detection accuracy, fast detection speed, and small model memory occupation, which can provide technical support for edge deployment of rail fastener defect detection. [ABSTRACT FROM AUTHOR]

A low-floor train–turnout coupling dynamic model considering bad alignment irregularity ahead of the turnout was established on the basis of a field test in which the dynamic performances of a low-floor train passing through a no. 6 turnout in a rail transit depot in China had been measured, as well as the line alignment and wheel and rail profiles. There are two types of wheelsets in the low-floor train: integral wheelset and independent wheelset. The model fully considers the coupling effect between the vehicle and the ballast components, and the simulated results are in consistence with measured results in the field test. Based on this, the influences of train speed, the wheel–rail friction coefficient, and the track alignment optimization of the dynamic performance of low-floor trains passing switch in facing direction are analyzed. The main results indicate that eliminating alignment irregularities before the switch can effectively improve the dynamic performance of the integrated wheelset in the switch and the lateral forces of the outer wheels of these two vehicles are reduced by about 80%, the derailment coefficients are reduced by about 70%, the vertical force is reduced by about 10–20% and wheel load is reduced by approximately 30%. [ABSTRACT FROM AUTHOR]

A model based on the theory of train-track-bridge coupling dynamics is built in the article to investigate how high-speed railway bridge pier differential settlement can affect various railway performance-related criteria. The performance of the model compares favorably with that of a 3D finite element model and train-track-bridge numerical model. The analysis of the study demonstrates that all the dynamic response for a span of 24 m is slightly larger than that for a span of 32 m. The wheel unloading rate increases with pier differential settlement for all of the calculation conditions considered, and its maximum value of 0.695 is well below the allowable limit. Meanwhile, the vertical acceleration increases with pier differential settlement and train speed, respectively, and the values for a pier differential settlement of 10 mm and speed of 350 km/h exceed the maximum allowable limit stipulated in the Chinese standards. On this basis, a speed limit for the exceeding pier differential settlement is determined for comfort consideration. Fasteners that had an initial tensile force due to pier differential settlement experience both compressive and tensile forces as the train passes through and are likely to have a lower service life than those which solely experience compressive forces. [ABSTRACT FROM AUTHOR]

In order to reduce the ground-borne vibration caused by wheel/rail interaction in the ballastless track of high speed railways, viscoelastic asphalt concrete materials are filled between the track and the subgrade to attenuate wheel/rail force. A high speed train-track-subgrade vertical coupled dynamic model is developed in the frequency domain. In this model, coupling effects between the vehicle and the track and between the track and the subgrade are considered. The full vehicle is represented by some rigid body models of one body, two bogies, and four wheelsets connected to each other with springs and dampers. The track and subgrade system is considered as a multilayer beam model in which layers are connected to each other with springs and damping elements. The vertical receptance of the rail is discussed and the receptance contribution of the wheel/rail interaction is investigated. Combined with the pseudoexcitation method, a solution of the random dynamic response is presented. The random vibration responses and transfer characteristics of the ballastless track and subgrade system are obtained under track random irregularity when a high speed vehicle runs through. The influences of asphalt concrete layer’s stiffness and vehicle speed on track and subgrade coupling vibration are analyzed. [ABSTRACT FROM AUTHOR]

Based on vehicle-track coupled dynamic theory, a three-dimensional asymmetric vehicle-track coupling vibration model is developed to investigate the effect of voided elastic two-block sleepers on vehicle and track system dynamic responses. For the vehicle system, one car body, two frames, and four wheel sets are assumed to be rigid, with 35 degrees of freedom (DOF). For the track system, the rails and the concrete two-block sleepers are the main vibration components. The rails are modelled as Timoshenko beams, and the concrete two-block sleepers are assumed to be rigid mass with vertical and lateral movement. The pads under the rails and the rubber boots under the sleepers provide greater vertical and lateral elasticity for the track. The Hertz nonlinear elastic contact theory is used to calculate the normal wheel/rail force. The wheel/rail tangent creep force is first calculated using Kalker’s linear creep theory and then modified by the Shen-Hedrick-Elkins theory. The results show that the asymmetric voided elastic two-block sleepers have greater effects on the dynamic responses for fasteners and sleepers than on the car body and the wheel/rail forces under measured geometric irregularity and random irregularity. Two or more voided sleepers will greatly affect the vehicle running safety. [ABSTRACT FROM AUTHOR]

Searching for the contact points between wheels and rails is important because these points represent the points of exerted contact forces. In order to obtain an accurate contact point and an in-depth description of the wheel/rail contact behaviours on a curved track or in a turnout, a method with improved accuracy in three dimensions is proposed to determine the contact points and the contact patches between the wheel and the rail when considering the effect of the yaw angle and the roll angle on the motion of the wheel set. The proposed method, with no need of the curve fitting of the wheel and rail profiles, can accurately, directly, and comprehensively determine the contact interface distances between the wheel and the rail. The range iteration algorithm is used to improve the computation efficiency and reduce the calculation required. The present computation method is applied for the analysis of the contact of rails of CHINA (CHN) 75 kg/m and wheel sets of wearing type tread of China's freight cars. In addition, it can be proved that the results of the proposed method are consistent with that of Kalker's program CONTACT, and the maximum deviation from the wheel/rail contact patch area of this two methods is approximately 5%. The proposed method, can also be used to investigate static wheel/rail contact. Some wheel/rail contact points and contact patch distributions are discussed and assessed, wheel and rail non-worn and worn profiles included. [ABSTRACT FROM AUTHOR]

The slab track of high speed railway has higher environmental noise emissions caused by a train running than the ballasted track. In order to predict and control wheel/rail rolling noise radiation due to roughness of wheel and rail running surface on slab track, a model is developed to calculate wheel/rail rolling noise of the slab track and analyze the influences of railway slab structure parameters on wheel/rail rolling noise. The results show that the rail noise occurs mainly in the middle and high frequency ranges of 500–2000Hz. The wheel noise is chiefly in the high frequency ranges of 1600–4000Hz, and the track slab noise radiates in the frequency ranges of 125–500Hz. Instantaneous noise pressure of the rail is first, the slab is second, the wheel is in between. The weights of the slab have more influence on emissions of the slab, but have little impact on noise emission of the wheel and rail. Below 500Hz, the greater weight of the slab is, the greater noise emission of the slab is, but above 500Hz, the result is the opposite. The CA mortar elastic modulus under the slab has little impact on noise emission of the wheel and rail, whereas has more influence on noise emissions of the slab. The greater elastic modulus of CA mortar under the slab is, the less noise emission of the slab is. The rubber pads installed under the slab have more influence on noise emissions of the slab than that of wheel and rail. All in all, the rubber pad under the slab is beneficial to wheel-rail noise reduction. [ABSTRACT FROM AUTHOR]

Abstract A discretization is applied to the continuous field-based pedestrian model to derive a discrete version. The concept of walk period is introduced so that pedestrians’ varied walking velocities can be studied without introducing any modification to the underlying logic. This further allows the discrete model to analyze a flow of randomly mixed population. Next, starting from the discrete model, a high performance GPU model targeting at the OpenCL heterogeneous parallel framework is developed. Advanced techniques are developed to allow efficient access to stored field strength, avoid atomic operations, and so on. Numerical experiments disclose that the GPU model can bring a as high as 30.8x performance improvement, with contrast to the previously developed CPU model. Thus, when equipped with proper functional modules such as a macroscopic/mesoscopic route selection and so on, the GPU model can act as a core engine for simulation of a large/very-large population. [ABSTRACT FROM AUTHOR]

Polyphenols are important bioactive substances in apple. To explore the profiles of the nine representative polyphenols in this fruit, a high-performance liquid chromatography method has been established and validated. The validated method was successfully applied for the simultaneous characterization and quantification of these nine apple polyphenols in 11 apple extracts, which were obtained from six cultivars from Shaanxi Province, China. The results showed that only abscission of the Fuji apple sample was rich in the nine apple polyphenols, and the polyphenol contents of other samples varied. Although all the samples were collected in the same region, the contents of nine polyphenols were different. The proposed method could serve as a prerequisite for quality control of Malus products., (Copyright © 2015. Published by Elsevier B.V.)

Objective: To investigate the condition of microwave radiation pollution from mobile phone base station built in populated area., Methods: Random selected 18 residential districts where had base station and 10 residential districts where had no base stations. A TES-92 electromagnetic radiation monitor were used to measure the intensity of microwave radiation in external and internal living environment., Results: The intensities of microwave radiation in the exposure residential districts were more higher than those of the control residential districts (p < 0.05). There was a intensity peak at about 10 m from the station, it would gradually weaken with the increase of the distance. The level of microwave radiation in antenna main lobe region is not certainly more higher than the side lobe direction, and the side lobe direction also is not more lower. At the same district, where there were two base stations, the electromagnetic field nestification would take place in someplace. The intensities of microwave radiation outside the exposure windows in the resident room not only changed with distance but also with the height of the floor. The intensities of microwave radiation inside the aluminum alloys security net were more lower than those of outside the aluminum alloys security net (p < 0.05), but the inside or outside of glass-window appears almost no change (p > 0.05)., Conclusions: Although all the measure dates on the ground around the base station could be below the primary standard in "environment electromagnetic wave hygienic standard" (GB9175-88), there were still a minorities of windows which exposed to the base station were higher, and the outside or inside of a few window was even higher beyond the primary safe level defined standard. The aluminum alloys security net can partly shield the microwave radiation from the mobile phone base station.

Rheumatoid arthritis synovial fibroblasts (RASFs) contribute to arthritic cartilage degradation. Although RASFs are normally resistant to apoptosis, Apo2L/tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-based gene therapy has been successfully used in a mouse model of arthritis. We investigated this further by treating human RASFs with nontoxic doses of the proteasome inhibitor lactacystin. Treatment induced cytosolic accumulation of p53 and enhanced the susceptibility of RASFs to apoptosis mediated by TRAIL-R2 (DR5) but not Fas. A specific role for p53 in TRAIL-R2-mediated apoptosis was indicated by the ability of p53 siRNA to significantly reduce RASF apoptosis and by the reduced apoptosis of RASFs bearing p53 mutations on treatment with anti-DR5 antibody or anti-DR5 antibody plus lactacystin. p53 immunoprecipitation followed by mass spectrometry identified a vimentin-p53 complex, an interaction that was confirmed by reciprocal vimentin-p53 immunoprecipitation and by co-immunofluorescence. Interestingly, human caspase-4 cleaved human vimentin, and blockade of caspase-4 with a chemical inhibitor or with specific siRNA significantly inhibited TRAIL-R2-mediated apoptosis of RASFs. Furthermore, blockade of caspase-4 was paralleled by persistence of a cytosolic pattern of p53 and absence of p53 translocation to the nucleus. Taken together, our findings suggest a unique role for caspase-4 in cleaving vimentin and releasing cytosolic p53 for nuclear translocation, events that may regulate the sensitivity of RASFs to receptor-mediated apoptosis.