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This study introduces the Fast fluid dynamics (FFD) based initializer as a novel approach to accelerate steady-state flow simulations. Three modes - Coarse-Mesh Mode (CMM), Large Timestep Mode (LTM), and Hybrid Mode (HM) - are developed on the OpenFOAM platform for efficiently simulating airflow in the built environment. All three modes exhibit faster computations than standard initialization methods by enabling quicker attainment of desired flow states and reducing the required matrix iterations. These initializers demonstrate better performance in flow problems characterized by higher Reynolds numbers. The CMM initializer achieves a nearly six-fold increase in speed by mapping initial solutions from a coarse mesh to a fine mesh. The LTM initializer allows for larger timesteps during initialization, resulting in a two-fold speed improvement in fluid simulation. The HM initializer combines the advantages of both CMM and LTM. However, it does not surpass the speed-up performance of the previous two modes. Apart from the benchmark test case, the proposed initializers can be applied to other indoor and outdoor flow scenarios. Furthermore, the simulation process is further streamlined by automating the execution of the initializer using scripts, eliminating the need for manual step-by-step inputs. • FFD-based initializer reduces costs, maintains accuracy/stability in fluid simulations. • Three modes (CMM, LTM, HM) achieve high accuracy and faster computations. • Initializers excel in flow problems with higher Reynolds numbers. • Initializers applicable to various ventilation scenarios. • Streamlined simulation process through automated execution of initializer. [ABSTRACT FROM AUTHOR]

Protein glycosylation plays a key role in various biological processes and disease-related pathological progression. Mass spectrometry (MS)-based glycoproteomics is a powerful approach that provides a system-wide profiling of the glycoproteome in a high-throughput manner. There have been numerous significant technological advances in this field, including improved glycopeptide enrichment, hybrid fragmentation techniques, emerging specialized software packages, and effective quantitation strategies, as well as more dedicated workflows. With increasingly sophisticated glycoproteomics tools on hand, researchers have extensively adapted this approach to explore different biological systems both in terms of in-depth glycoproteome profiling and comparative glycoproteome analysis. Quantitative glycoproteomics enables researchers to discover novel glycosylation-based biomarkers in various diseases with potential to offer better sensitivity and specificity for disease diagnosis. In this review, we present recent methodological developments in MS-based glycoproteomics and highlight its utility and applications in answering various questions in complex biological systems. Image 1 • Improved glycopeptide enrichment methods have been developed for N-linked and O-linked glycopeptide analysis. • Hybrid fragmentation techniques enable site-specific glycopeptide characterization. • Emerging specialized software facilitate intact glycopeptide analysis and deciphering microheterogeneity of glycoforms. • Effective quantitation strategies and workflows allow comparative glycoproteome analysis and disease biomarker discovery. [ABSTRACT FROM AUTHOR]

This study compares the performance of empirically- and physically-based methods for predicting coseismic landslides around Aso caldera during the 2016 M w 7.0 Kumamoto earthquake. The physically-based method couples a regional-scale wave propagation simulation with a site-scale Newmark-type sliding analysis, while the empirically-based method predicts sliding displacements based on seismic recordings and/or ground motion prediction equations. By using the well-documented landslide inventory, the predictive capacity of each method is quantitatively assessed. The case study demonstrates that the physically-based method has the advantage of simulating complicated near-fault and topographic effects. It captures around 44% of observed landslides at the caldera rim, which is significantly better than the 20% captured from the empirically-based prediction. Both methods have similar prediction performance, capturing around 56% actual landslides at the central cone region. The empirically-based method is simple to use and provides fast landslide prediction. It can be further improved by incorporating a simple prediction model for the topographic amplification effect, which increases the percentage of captured landslides by around 8% across the caldera rim. • Empirically- and physically-based methods are used to evaluate regional coseismic landslides in the 2016 Kumamoto earthquake. • Predicted landslides are validated against the well-documented landslide inventory. • The topographic amplification of ground motions is incorporated to improve the empirically-based method for fast prediction. [ABSTRACT FROM AUTHOR]

Glycans and glycoconjugates are involved in regulating a vast array of cellular and molecular processes. Despite the importance of glycans in biology and disease, characterization of glycans remains difficult due to their structural complexity and diversity. Mass spectrometry (MS)-based techniques have emerged as the premier analytical tools for characterizing glycans. However, traditional MS-based strategies struggle to distinguish the large number of coexisting isomeric glycans that are indistinguishable by mass alone. Because of this, ion mobility spectrometry coupled to MS (IM–MS) has received considerable attention as an analytical tool for improving glycan characterization due to the capability of IM to resolve isomeric glycans before MS measurements. In this review, we present recent improvements in IM–MS instrumentation and methods for the structural characterization of isomeric glycans. In addition, we highlight recent applications of IM–MS that illustrate the enormous potential of this technology in a variety of research areas, including glycomics, glycoproteomics, and glycobiology. [ABSTRACT FROM AUTHOR]

We have investigated structural properties of Eu doped gallium oxide (Ga 2 O 3 ) films grown by pulsed laser deposition at different substrate temperature. X-ray rocking curve and Raman spectroscopy measurements prove that the films grown at the substrate temperature above 400 °C are of monoclinic β -Ga 2 O 3 structure and the crystalline quality of the films depends on the substrate temperature. X-ray absorption near edge structure measurements indicate that the valence of Eu ions in the Eu doped Ga 2 O 3 films varies from mixture of bivalent and trivalent to only trivalent with increasing substrate temperature. Extended X-ray absorption fine structure analysis reveal that the Eu atoms doped in Ga 2 O 3 matrix are incorporated on Ga sites in Ga 2 O 3 matrix even for the films with amorphous structure grown at low substrate temperature. [ABSTRACT FROM AUTHOR]

In this study, the aerodynamic performance of two trains that intersect inside a tunnel under ambient wind conditions is investigated. A full-scale test is conducted to verify the computational method and mesh, and then a series of numerical simulations are performed to investigate the pressure variation and the aerodynamic force coefficient by comparing with the condition of no ambient air. The difference between the results with/without ambient wind in a tunnel is analysed. The results indicate that if Train A travels downwind, the positive pressure of train surface increases and the negative pressure decreases as the wind velocity increases, and the arrival time of the maximum positive pressure lags on average 0.024 s and 0.058 s for wind velocities of 20 m/s and 40 m/s, respectively. For the tunnel wall measuring points, the maximum positive pressure increases as the wind velocity increases. The maximum drag coefficient of downwind Train A decreases by 4.7% and 10.1% for wind velocities of 20 m/s and 40 m/s, respectively, whereas that of upwind Train B increases by 5.7% and 15.8%, respectively. The maximum positive side force coefficient of downwind Train A increases by 20.8% for an ambient wind velocity of 40 m/s, whereas the same coefficient decreases by 16.7% for upwind Train B. [ABSTRACT FROM AUTHOR]

• A bearing heat-fluid–solid multi-field coupling model is established. • The micro stress and the micro motion law of bearing was solved. • The law of fatigue crack initiation was found. The working environment of aviation bearings is harsh and require high reliability. The bearing service performance is not only affected by the complex working conditions of the bearing, but also by the microstructure of bearing steel smelting. The key to achieving personalized design of high-performance bearings is to combine the complex working conditions of the bearing with the microstructure of the bearing steel to reveal the failure mechanism of the bearing. In this paper, a bearing thermal-solid coupling model is established by Python scripts, and the fluid characteristics is calculated based on the CFD method. At the same time, the multifield coupling conditions of the bearing and the bearing microstructure are combined to establish a bearing macro–micro coupling model, according to the bearing's EBSD and SEM measurement results. The stress distribution characteristics of the bearing microstructure is calculated by the sub-model method. On this basis, the microscopic failure evolution process of the bearing under the multifield coupling action is calculated and revealed by the crystal plastic finite element method. The results show that during the bearing service, some bearing inclusions will have a large difference in stress components, the surrounding grains will move significantly and the stress will accumulate, which will eventually lead to the initiation of the bearing fatigue failure. [ABSTRACT FROM AUTHOR]

(AlGa) 2 O 3 thin films were deposited on (0001) sapphire substrates by pulsed laser deposition at different substrate temperatures. The influence of substrate temperature on surface morphology, optical properties, and crystal quality has been systematically investigated by atomic force microscope, transmission spectra, X-ray diffraction, and Raman spectroscopy. The results reveal that all the (AlGa) 2 O 3 films have smooth surface and high transmittance. The (AlGa) 2 O 3 film with the good crystal quality can be obtained at a substrate temperature of 400 °C. Our results provide an experimental basis for realizing the Ga 2 O 3 -based quantum well. [ABSTRACT FROM AUTHOR]

The rapid growth in nanotechnology and biotechnology offers a wealth of opportunities for the combination of natural enzymes with different kinds of nanomaterial. Here, we highlight recent advances in constructing nanomaterial-incorporated enzymes that integrate the specific recognition and biocatalytic properties of enzymes with the attractive electronic, optical, magnetic, and catalytic properties of nanomaterials. These composite materials have some extra features that are not possessed by the enzymes themselves, such as electron transfer mediated by nanoparticles, enzyme delivery, remote activation and/or deactivation of enzymatic activity, and fabrication of catalytic entities with complementary functions. Additionally, we describe briefly the current challenges and future development of unique enzyme–nanomaterial hybrid systems. We hope that this review will help to accelerate further progress in this promising field. [ABSTRACT FROM AUTHOR]

Europium (Eu) doped Ga 2 O 3 films were deposited on sapphire substrates by pulsed laser deposition (PLD) with varying Eu contents at substrate temperature as low as 500 °C. Energy dispersive spectroscopy results show that films with different Eu contents can be obtained by changing the Eu composition in the targets. X-ray diffraction and Raman spectra analysis indicate that all films have the monoclinic structure with a preferable (−201) orientation. The films exhibited high transmittance more than 90% in the visible region and 80% in the UV region. Intense red emissions at 613 nm due to the transitions from 5 D 0 to 7 F 2 levels in Eu were clearly observed for the Eu doped Ga 2 O 3 films, suggesting PLD is a promising method for obtaining high quality Eu doped Ga 2 O 3 films at low growth temperature. [ABSTRACT FROM AUTHOR]

• A bearing heat-fluid–solid multi-field coupling model is established. • The micro stress of bearing was solved. • A multivariate random parameter evaluation method is proposed. • The influence of inclusions on the bearing microscopic stress is quantitatively evaluated. The micro-stress distribution of the bearing in actual work directly affects its service performance. This paper attempts to unify the bearing multi-field coupling service conditions with the micro-inhomogeneity of the internal material of the bearing steel, establish a micro-stress sensitivity analysis method for aviation bearings. The bearing motion parameters are solved based on the pseudo-dynamics method. The bearing fluid lubrication model was then established to calculate the lubricant state based on the CFD method. A bearing heat-fluid–solid multi-field coupling model is established based on the grid mapping method. According to EBSD, SEM and nanoindentation experiment, the microstructure model of bearing was established, and the micro stress of bearing was solved based on sub model method. A response surface model is established by the BOX-Behnen Design method. A multivariate random parameter evaluation method is proposed based on the SPEA coefficient. And the influence of inclusions on the bearing microscopic stress is quantitatively evaluated. The calculation results show that the inclusions' size and the inclusions' position significantly influence the degree of stress concentration. The degree of influence is divided into 0.478 and 0.650. The difference in stress components is mainly affected by the location of inclusions. The degree of influence exceeds 0.9. The overall effect of inclusion morphology is the smallest. [ABSTRACT FROM AUTHOR]

Based on unsteady simulations and decomposed sliding mesh technology, train aerodynamic and dynamic behaviors near an elongated hillock beside a windbreak under a crosswind were analyzed. First, the sudden deterioration of the aerodynamic performance was explained. Then, a mitigation measure was proposed to reduce the impact of the elongated hillock on the train. Finally, the dynamic responses for the original elongated hillock and mitigation measure were compared. The results showed that two symmetric vortices along the railway were generated by the elongated hillock, and in the position between these two vortices, a strong wind speed occurred, which resulted in a sudden impact on the train, and the aerodynamic impacts were the largest on the head car. A certain distance from the elongated hillock to the windbreak could make a mitigation effect. For the original elongated hillock, there was a severe yawing phenomenon of more than 83 mm/3° from the centerline of the car body for the head car. For the mitigation measure, the safety index and vibration displacement of the head car and tail car decreased effectively. • The train aerodynamic performance and flow deterioration mechanism were studied under the sudden elongated hillock area. • Based on the causes of the deterioration of the flow field, effective mitigation measures were proposed and investigated. • The system dynamic behaviors of the train under the original and the mitigation scheme were analyzed and compared. [ABSTRACT FROM AUTHOR]

• The pressure integral method 15–4 is for the head car and tail car. • The pressure integral method 14–4 is for the middle car. • The error of M x of head car is less than 10% at different yaw angles. • The error of M x of tail car is less than 15% at different yaw angles. The present work studies the aerodynamic loads of a train for different yaw angles from 5.87° to 30° by using the detached-eddy simulation (DES) method. Furthermore, based on the pressure integral method, a reasonable layout of the pressure taps on the train under a crosswind is studied to obtain the aerodynamic forces and moments that are used for a comparison with the results of the wind tunnel test. Considering the lower errors of the pressure integral results and fewer number of pressure taps comprehensively, the pressure integral method in the case of 15–4 (15 represents the tap quantity along the length direction, 4 represents the tap quantity along the height/width direction) on the head car and tail car, the case of 14–4 on the middle car are relatively good among the nine cases discussed in this paper. Compared to the results of the wind tunnel test, for the head car, the maximum error of the side force coefficient (C y), rolling moment coefficient (M x), and yawing moment coefficient (M z) is all less than 10% for yaw angles from 5.87° to 90°, and the maximum errors of lift force coefficient (C z) is less than 20% for yaw angles from 10.2° to 90°; for the middle car, the maximum error of C y is less than 20% for yaw angles from 5.87° to 90°, and the maximum error of C z , M x and M z is all less than 15% for yaw angles from 5.87° to 90°; for the tail car, the maximum error of C y , C z , M x and M z is all less than 15% for yaw angles from 10.2° to 90°. [ABSTRACT FROM AUTHOR]

Thulium (Tm) doped Ga 2 O 3 films were deposited on sapphire substrates by pulsed laser deposition (PLD) with changing Tm compositions in the targets. Energy dispersive spectroscopy results reveal that films with different Tm compositions can be tailored by changing the Tm composition in the targets. X-ray diffraction and Raman spectra analysis indicate that all films have the monoclinic structure. Photoluminescence measurements demonstrate that the emission peaks at 460, 650 and 800 nm are observed from the Tm 3 + 4 f intrashell transitions from 1 G 4 excited states to the 3 H 6 , 3 F 4 , and 3 H 5 states, respectively. The results suggest that PLD is a promising method for obtaining high quality Tm doped Ga 2 O 3 films, which paves the way for the fabrication of optoelectronic devices based on Ga 2 O 3 films. [ABSTRACT FROM AUTHOR]

With increasing train speeds, the wind environment along routes has become complex, variable, and extreme. Constructing windbreak facilities is an effective strategy to enhance train operational safety in windy zones. Various windbreak designs exhibit notable differences in improving train dynamic performance, and economic considerations are also crucial. Utilizing the non-constant compressible Reynolds time-averaged equation URANS (Unsteady Reynold-averaged Navier–Stokes) alongside the shear-stress transport (SST) k-ω turbulence model, this study simulates the non-constant aerodynamic characteristics of a 350 km/h high-speed train traversing through different forms of windbreak corridors in a 30 m/s wind zone. The train's dynamic response was captured using a combined CFD–MBD (Computational Fluid Dynamics and Multi-Body Dynamics) offline time-domain simulation, the accuracy of which was verified experimentally. Results indicate that vortices of various positions and shapes form in the flow field along the windbreak corridor depending on the size of the openings. Using the no-windbreak corridor (Case 1) and the fully enclosed corridor (Case 4) as control groups, it was observed that smaller openings lead to more stable airflow, enhancing peak damping and fluctuation effects, albeit with varying stages of aerodynamic load fluctuation. The 1/3-opening windbreak corridor (Case 3) effectively mitigated the sudden aerodynamic load changes at the wind zone transition of the 2/3-opening windbreak corridor (Case 2), with the primary fluctuation area in Case 3 being the wind section. Dynamic analyses revealed that Case 2 exhibited insufficient lateral aerodynamic performance, raising derailment concerns. In contrast, Case 3 ensured travel safety and comfort effectively, while Case 4 offered excessive protective capacity. This study's findings serve as a valuable reference for designing windbreak corridors and ensuring the safe operation of trains in windy regions. • The internal flow field varies with the opening size of windbreak corridors. • Peak and fluctuating aerodynamic loads depend on opening size of windbreak corridors. • The abrupt change of wind load is the largest in the transition area of windbreak corridor. • The aerodynamic load impact of the head car is the largest. • Lateral aerodynamic performance of maximum opening windbreak corridor is insufficient. [ABSTRACT FROM AUTHOR]

Abstract: The lateral organization of membrane proteins and lipids domains has a direct impact on many cellular processes, but generally these domains are too small to be resolved by diffraction-limited resolution of fluorescence microscopy. Here, we use quantum dot (QD) labeling based on near-field optical imaging, to study the nanoscale organization of hyaluronan receptor CD44 molecules of fixed mesenchymal stem cells (MSCs) in air, with a optical resolution down to 50nm. The photostability and high luminance of QD evidently improve the signal-to-noise ratio and reproducibility of near-field optical data. Importantly, the blinking-intensity analysis was proposed to identify single QD, providing a calibration to relate intensity to numbers of antibody for the first time. Additionally, the fluorescence-topographic imaging enables us to investigate the topographic location pattern. Our results demonstrate that CD44 molecules on MSCs are enriched into nanosized domain and they predominantly locate on the peak of the membrane protrusions, which may contribute to clarify the underlying mechanism of functions ascribed to these molecules. [Copyright &y& Elsevier]

Double-unit trains composed of the same type of high-speed trains (HSTs) are relatively common. The connection of different types of trains, however, has been rarely studied. Therefore, we adopted an improved delayed detached-eddy simulation (IDDES) method to investigate the aerodynamic characteristics on double-unit trains formed by different types of HSTs. Two standardized HSTs—Train A and Train B at present in China—are used to form four different cases (A-A, A-B, B-A, and B-B). We conducted algorithm validation and grid independence to ensure the reliability of numerical results. The results showed the drag of case B-B was smaller when the same HST units were connected, whereas the drag of case A-B was smaller when the different HST units were connected. Downstream the coupling region, the structures of vortex shedding presented obvious differences for each case, which further led to different fluctuation intensities in wake vortices. The order of the height of the wake vortices was as follows: h 1(A-A) > h 3(B-A) > h 2(A-B) > h 4(B-B). The tail of the upstream vehicle had a dominant influence on the slipstream peak in the coupling region. • The minimum drag of double-unit train formations with different combinations is obtained. • The discontinuous coupling region has an obvious influence on the downstream vortices. • The tail of the upstream vehicle has a dominant influence on the slipstream peak in the coupling region. [ABSTRACT FROM AUTHOR]

With the continuous improvement of train speeds, aerodynamic braking is a good choice to effectively reduce the braking distance. In this study, unsteady aerodynamic characteristics of vehicles with braking plates inside and outside the tunnel were evaluated by CFD using an improved delayed detached eddy simulation (IDDES). Mesh convergence studies were also performed, and results were compared with two wind tunnel tests to verify the numerical method. By comparing and analyzing the effect of plates on the force, braking distance, and flow field around vehicles inside and outside the tunnel, it is found that the aerodynamic braking force of vehicles inside and outside the tunnel increases nearly 1.5 times and 2.2 times due to the opened plates, respectively. The positive lift force of vehicles is also increased, especially inside the tunnel, which reduces the friction between the wheels and rail tracks. The opened plates also cause the formation of many vortices with excessive energy, which may aggravate the vehicle vibration and noise, especially inside the tunnel. By comparing the impact of the operating environment (inside or outside the tunnel) on the aerodynamic characteristics of each vehicle, it is also found that the closer the vehicle to the downstream, the more sensitive it is to the tunnel. The findings of this study can help to design the braking plate and guide the operation of rail vehicles. • Aerodynamic characteristics of one-fifth scaled uniform vehicle models were studied. • Effect of aerodynamic braking plates on rail vehicles was investigated. • Numerical results were verified by wind tunnel test and grid resolution analysis. • Aerodynamic braking force of vehicles in the open air and tunnel increased. • Downstream vehicles are relatively more sensitive to the tunnel. [ABSTRACT FROM AUTHOR]

Crosswind stability of trains is significantly affected by running safety and pantograph–catenary interaction, which are dependent on the depths of railway cuttings. Under crosswind with wind speed of 30 m/s and yaw angle of 30°, the aerodynamic loads and surrounding flow of the train and pantograph in the cuttings with different depths (0, 3, 6, 9, and 12 m) were investigated using numerical simulations. A dynamic model of the pantograph–catenary interaction was established and employed to analyze the contact force. The head car was the most critical even after accounting for the pantograph under crosswind. The head car was better protected against crosswind as the cutting became deeper. The pantograph–catenary interaction was optimal in the cutting with a depth of 6 m. The time-averaged contact force was excessively large in the shallow cutting, whereas the contact loss occurred in the deep cutting. The depth of the cutting had a different effect on running safety and pantograph–catenary interaction. Hence, a balance between the running safety and pantograph–catenary interaction should be considered in the cutting. According to the fitting results, the appropriate range of cutting depth is 4.6–6.5 m. Overall, these conclusions provide insight into the effect of cutting depths on the crosswind stability of trains and indicate the importance of the pantograph–catenary interaction in the design of railway cuttings. • The effect of railway cutting depths on crosswind stability of trains was studied. • The crosswind stability of the train was assessed by numerical simulations. • The running safety improved with the increase in the depth of the cutting. • A medium depth of the cutting was beneficial for the pantograph-catenary contact. [ABSTRACT FROM AUTHOR]

The harvesting of wind energy from the slipstream generated when a train passes through a tunnel is a new way to produce renewable energy. From the perspective of CFD (Computed fluid dynamics), a three-dimensional URANS (unsteady Reynolds-averaged Navier–Stokes) model was used to study the energy harvesting performance of wind turbines with different design parameters inside the tunnel during the entire process of a train passing through a tunnel. A higher value of offset distance of blades could promote the power efficiency of the wind turbine inside the wind tunnel. The maximum power efficiency with regard to overlap distance was found when an overlap distance is 0 m. The turbine with a negative twist angle yielded a better performance than the turbine with a positive twist angle. The optimal wind turbine can generate up to 157.9 W power when a train passes at 350 km/h. Given the tunnel distribution in China, 4.8 × 1012 J energy will be recovered each day by this way, which is sufficient to supply the emergency power for railway lighting. It can also effectively ease the pressure of daily lighting power in railway tunnels. • Harvesting wind energy from railway tunnels is considered feasible. • DFBI (dynamic fluid body interaction) was used to simulate the response of the turbine. • The power efficiency of turbines with various design parameters was quantitatively evaluated. • The optimal wind turbine can generate up to 157.9 W power when a train passes at 350 km/h. [ABSTRACT FROM AUTHOR]

The present work mainly focuses on the evolution of the airflow passing embankments of different heights, with and without trains. Using the delayed detached-eddy simulation (DDES) method, the effects on the velocity and acceleration of the airflow caused by the embankments' upstream slope were studied using a set of embankments with different heights. The aerodynamic loads experienced by each car of the train, on both the windward and leeward rails, were calculated and the effects of different embankments examined. To distinguish how the geometry of embankments affected the flow patterns, distributions of streamline, velocity and the vortices formed around the head car and embankment are shown. The differences in pressure distribution on central loops of each car caused by the different embankment heights were analyzed at a yaw angle of 19.8°. Using the wind speed at 4 ​m above the actual rails and the reference at 10 ​m above the ground, the effect of wind speed on the aerodynamic forces and moments of the train, independent of the embankments' height, can be obtained. This method has the potential to simplify the calculations needed to evaluate the safety of trains running on different embankment heights in strong wind environments. • Evolutions of the airflow passing embankments of different heights were compared and analyzed. • Variations in the form of the growth laws for different cars above these embankments were found. • A relationship was established between the wind speeds in two different measuring points. [ABSTRACT FROM AUTHOR]

The train-induced airflow in a tunnel has great significance for tunnel ventilation, fire rescue, and equipment installations. In particular, the aerodynamic effects induced by two trains passing each other in a tunnel are fiercer and complicated than those of a single train. In this research, a comparative CFD study of the three-dimensional slipstreams induced by a single train and two trains passing by in a tunnel was conducted using the unsteady Reynolds-Averaged Navier–Stokes (URANS) method. Three-dimensional computational models of a high-speed train and a tunnel are developed based on the sliding mesh technique and validated through experiments. The characteristics of the components of the slipstream were fully reported in three directions at different spatial positions. The results demonstrated that the impact of the tunnel pressure waves on the local airflow was independent of the spatial locations for the same cross-section. The variations of the longitudinal component (u) and the resultant slipstream (U R) were generally consistent with each other, demonstrating that the slipstreams inside the tunnel were mainly longitudinal flow. In addition, the piston effect was more pronounced when the space was constrained by another train for the crossing-trains case. The largest discrepancy of the maximum peak value at different positions for the crossing-trains case was 34% larger than that of the single-train case. • The time and spatial evolution of the slipstreams when two trains meeting in a tunnel were numerically investigated. • The distribution of the slipstreams with longitudinal, vertical and lateral distance were comparatively presented. • The relationship between the pressure waves and slipstreams was fully analyzed. [ABSTRACT FROM AUTHOR]

The geometries of bogies have a significant influence on the aerodynamic performances of high-speed trains (HSTs) in crosswinds, especially for wind tunnel tests. The delayed detached-eddy simulation (DDES) method was used to calculate the aerodynamic characteristics of 1/8th scaled HST models with differently simplified bogies under crosswinds. The numerical results were verified by wind tunnel tests using a same model. It was proven that the complexity of bogies has a significant influence on the HST models' aerodynamic drag and rolling moment at various yaw angles. The flow field of the HST models under a 30° crosswind was then employed to study the effects of the bogies. With the simplification of the bogie structure, the positive and negative pressure in bogie cabins increased while that on the top surface seldom changed. Various flow patterns were found on the windward side and top surface of bogie cabins. The differences of the flow fields underneath the train models were quantitatively analyzed using the vertical velocity profiles near each bogie. • Aerodynamic drag and rolling moment caused by various bogies under crosswinds. • Pressure distribution on bottom and top central line of train bodies. • Differences on flow patterns on boards of bogie cabins. • The underbody flow in term of velocity profiles vary due to bogie complexity. [ABSTRACT FROM AUTHOR]

The present work focused on the aerodynamic performance of double unit trains (DUT) and traditional single unit trains (SUT) under crosswinds. The aerodynamic coefficient as well as the characteristics of the time-averaged and instantaneous flow of the SUT and DUT were calculated using the improved delayed detached eddy simulation (IDDES) method for 1/8th scale models. The numerical results were verified by wind tunnel tests. The time-averaged flow pattern on different cross-sections and horizontal planes were compared for the SUT and DUT. The pressure coefficients on the loops of different cars were also analyzed quantitatively. The vortices around the SUT and DUT were visualized, and the frequency characteristics of each car of the SUT and DUT were computed. The coupling region changed the forces on the train and increased the overall drag of the train. Faster vortex development was found on the last three cars of the DUT. Furthermore, a higher velocity belt was generated by the gap of the coupling region. The coupling region gave a significant influence of the power spectrum densities (PSD) on the last four cars and a relatively slight impact on the first two cars. • The aerodynamic forces of double unit trains under crosswind. • Leeward time-averaged flow patterns projected on different y-z planes. • Velocity distribution on horizontal planes of at different heights. • Ringed Pressure coefficients on train surface along the train length. • Different instantaneous characteristics between the SUT and DUT. [ABSTRACT FROM AUTHOR]

The train/tunnel aerodynamic effects still remain a major concern during high-speed railway construction. At present, different sizes of tunnels with constant cross-section are generally adopted based on train speed and blockage ratio. However, for tunnels with constant cross-section, narrower cross-section leads to worse aerodynamic effects while larger cross-section results in sharply increasing costs. Focusing on this problem, this paper proposes a new type of high-speed railway tunnel to mitigate the aerodynamic effects by enlarging the cross-section at both ends and reducing the cross-section in the middle portion of the tunnel. A three-dimensional, unsteady, compressible and RNG k-ε turbulence model is utilized to simulate the pressure waves induced by a high-speed train passing through such a tunnel. Three cases with different enlarged portal lengths are simulated. The pressure variations on the tunnel wall and train surface are compared with previous moving model tests to validate the numerical algorithm. The results show that the train-tunnel-entry induced pressure transients are greatly reduced compared with that of constant cross-section tunnel. In addition, the pressure gradient and micro-pressure wave (MPW) emitted from the tunnel exit are also considerably decreased. Due to the enlarged portal of the tunnel, pressure waves are repeatedly reflected, and a new compression wave is developed at the junction where the tunnel cross-section abruptly changes. As a result, the wave energy is dissipated, and its strength is reduced. However, it is revealed that the length of the enlarged portal has less influence on the maximum pressure gradient and the MPW. • A new type of high-speed railway tunnel with cross-section expansion is proposed. • The propagation characteristics of the pressure waves are fully analysed. • Influence of the enlarged portal length on pressure variations is numerically investigated. • Pressure distributions on tunnel wall and train surface are performed. [ABSTRACT FROM AUTHOR]

• In this paper, the effects of water–binder ratios and curing ages on the axial tensile stress–strain curves of mortar, new–old mortar interface and RAC were investigated experimentally. • Based on the experimental results and the random aggregate model, the manuscript explores the tensile damage development of RAC and analyzes the law and mechanism of the influence of the properties of old mortar on the axial tensile stress–strain curves of RAC. • In this paper, the tensile constitutive relationship of RAC is proposed based on the tensile constitutive relationship of ordinary concrete, combined with experimental results and numerical analysis results. The tensile constitutive relationship is essential for determining the ductility and restoring force characteristics of seismic-resistant concrete structures and studying the mechanisms causing damage and fracture to concrete structures. This study investigates the axial tensile stress–strain curves of mortar, the interface between new and old mortar, and recycled aggregate concrete (RAC) with different water-binder ratios and ages. First, the tensile constitutive relationships of mortar and new-old mortar interface were established. Then, based on the experimental results and the random aggregate model, a double-interface numerical model of RAC was established to investigate the development of tensile damage in RAC and the influence law and mechanism of the old mortar strength, thickness and curing age on the curve of the tensile stress–strain of RAC. The results are a comparison of the peak tensile strengths at the same age and water-binder ratio for the above three mortar types, where new mortar > RAC > new-old mortar interface. Under the same thickness of old mortar, the peak stress, elastic modulus and peak cutline modulus of RAC increased with the increase of old mortar strength, and the amplitude of change increased with the increase of mortar thickness. Based on the tensile constitutive relationship of ordinary concrete, the tensile constitutive relationship of recycled coarse aggregate concrete is proposed by combining the experimental results and numerical analysis results. [ABSTRACT FROM AUTHOR]

• Changepoints and piecewise linearities of pressure on trains were evaluated. • A strategy of discretization based on Lagrange rectangular elements was suggested. • A strategy of discrete integration was presented to measure aerodynamic loads. • The strategies can be used in full-scale tests and model tests. • The strategies can accurately obtain means and fluctuations of aerodynamic loads. Discrete integration occupies an important place in train aerodynamic tests in crosswinds. Improved delayed detached eddy simulations based on shear stress transport k - ω turbulence models were carried out to calculate the side force, lift, rolling moment around the lee rail, and surface pressure on bluff and streamlined vehicles. The changepoints and piecewise linearities of the pressure coefficients were evaluated, and the maximum coefficient of determination in the elements was 0.9973. A realizable strategy of the discretization based on the Lagrange rectangular elements was suggested, including the largest lengths and numbers of the elements. From this, a strategy of the discrete integration was presented to measure the aerodynamic loads, considering the real orientation of the elements. The maximum errors of the mean aerodynamic load coefficients of the bluff and streamlined vehicles were 4.1% and 2.2% (except the mean lift coefficient of the bluff vehicle), respectively. The errors were less than those in the previous studies, especially for the streamlined vehicle, which reduced by up to 8.7%. The unsteady aerodynamic loads with no delay obtained by the strategies were near to natural ones in the frequency range that people would be concerned about in crosswinds (at the Strouhal number of less than 0.4). Some suggestions were made for using the strategies in the full-scale tests and model tests, which provided a foundation for further studies of the running safety in natural crosswinds. [ABSTRACT FROM AUTHOR]

Determining the dynamic airtightness coefficient (τ d y n ) of train carriages using a high-accuracy and high-efficiency method is essential regarding the study of the dynamic airtightness performance of high-speed trains (HSTs) traveling through tunnels. This study set out to provide a systematic elaboration and investigation of the whole process of establishing the calculation methodology of τ d y n of HST carriages. Moreover, the applicability of three different typical optimization algorithms in the calculation of τ d y n was explored and compared. These were the traversal algorithm (TRAA), the trichotomy algorithm (TRIA), and the genetic algorithm (GA). Using the established calculation method, the values of τ d y n of different HST carriages for tunnels with different lengths were calculated based on field test data of pressure outside and inside HST carriages. Results revealed that the selection of optimization algorithms had significant effects on the calculation process of τ d y n because of their different optimization mechanisms. These three optimization algorithms were proven to be feasible for establishing the calculation method of τ d y n and gave the same calculation result of τ d y n for the calculation example within the expected accuracy. The elapsed time of the TRAA and GA were approximately 100 and 80 times that of the TRIA regarding the calculation example. The TRIA was the preferable choice for the calculation of τ d y n among the three algorithms because of its uncomplicated implementation logic and high efficiency. Within the tunnel-length range involved, the tunnel length itself had no significant effect on τ d y n of HST carriages. A significant increasing trend in τ d y n of HST carriages was found along the train length. Compared to the head car, the increasing ratio of τ d y n of the second car was varying from 0.2 to 0.5, while the increasing ratio of the seventh car was ranging from 0.8 to 1.7 considering different tunnel lengths. These findings provide a reference basis for the design of the calculation method of τ d y n of HST carriages and also enhance understanding of τ d y n of HST carriages under different operating circumstances. • The whole process of establishing the calculation method of the dynamic airtightness coefficient of trains was elaborated. • Different calculation methods of dynamic airtightness coefficient were established based on three optimization algorithms. • The effect of tunnel lengths on the dynamic airtightness coefficient of high-speed train carriages was investigated. • Differences in dynamic airtightness coefficient among different train carriages were discussed. [ABSTRACT FROM AUTHOR]

Hidden bruising is considered as one of the difficulties during loquat quality control, which has made an impact on postharvest quality and storability. Optical coherence tomography (OCT) is used as a non-destructive method that acquires 2D images of the sub-surface structure of the loquat. After OCT image processing, the attenuation coefficients ( μ t ) of the regions of interests are fitted to quantitatively analyze the characteristics of loquat tissue through using a confocal signal scattering model from OCT A-scan signals. In this experiment, a total of 60 loquat samples are investigated, with the non-bruised tissue having a large μ t with a mean value of 1910 m −1 (std: ±160). However, bruised groups without any storage time and after storage for 12 h showed lower μ t with a mean value of 1190 m −1 (std: ±230) and 1020 m −1 (std: ±190) respectively. The μ t value is sensitive to chemical and structural changes in loquat tissue and can also be used in hidden bruise discrimination of loquat. [ABSTRACT FROM AUTHOR]