Search

The pavements of the Beijing Capital International Airport (BCIA), China, where a buried fault zone lies beneath, have undergone continuous severe damages since 2008, but its causes remain unclear. This study focuses on the combined effect of moving aircraft loads and a buried fault zone existence, considering the enormous number of airport operations at the BCIA and the complex conditions of the pavement structure. Hence, a series of numerical simulations conducted using the three-dimensional finite element model were performed. Two models were developed in this study. Model 1 contained a buried fault zone, whereas model 2 did not. The simulation scenarios in each model include a low-speed scenario (scenario 1), a moderate-speed scenario (scenario 2), and a high-speed scenario (scenario 3). Our results show that the most evident deflections caused by the aircraft loads were largely concentrated on the pavements built on the fault zone. The maximum vertical displacement after loading once in model 1 was determined as 0.5 ~ 0.7 mm, whereas in model 2 was 0.4 ~ 0.5 mm. The greatest vertical displacements were generated in scenario 1 rather than in scenario 3, in both models 1 and 2. Moreover, the maximum shear strains on the pavement surface in model 1 are about 2 ~ 19 times larger than in model 2. These findings suggest that aircraft moving loads in the BCIA, especially the low-speed loads, contributed a lot to the recurrent pavement faulting and demonstrate the adverse effects of the buried fault zone on pavement performance. [ABSTRACT FROM AUTHOR]

[Display omitted] • Quench cooling was experimentally studied by reciprocating moving jet. • Heat transfer mechanisms under different moving speeds was revealed. • Two-dimensional transient heat fluxes were extracted and analyzed. • The heat transfer characteristics of high temperature surface was clarified. Owing to the short time duration and violent nature of boiling regimes, the steel quench cooling on the Run Out Table is extremely complex, this challenges the prediction of the heat transfer coefficient. In this study, we first established a novel reciprocally moving nozzles platform to experimentally investigate the moving quenching process. Then the two-dimensional transient heat flux, wetting behaviors, and heat transfer mechanism that was influenced by the surface temperature, and moving speed were explored. These results revealed the heat flux reduced with the moving speed but elevated with the surface temperature. The wetted area also expanded linearly with the decrease in temperature. With the aid of the developed two-dimensional transient heat flux, the heat quantity was revealed to decrease with the surface temperature at different speeds, but the decline proportion was much lower than that of MHF (maximum heat flux). Notably, the transient heat flux and heat transfer capacity in two-dimensional favored predicting the temperature field of the steel quenching process under industrial conditions. The findings in this work provided the envision to understand the heat transfer mechanism in the moving quenching cooling and provided a flexible method to investigate cooling in a moving state. [ABSTRACT FROM AUTHOR]

• The unified model for the axially moving corrugated sandwich panel is established. • The vibration suppression study of the moving corrugated plate based on the negative capacitance PSDC is proposed. • The effects of the moving speed on the vibration suppression performance of PSDC are discussed. The sandwich plate structures with corrugated cores are extensively utilized in engineering cases, such as the panels in railway vehicles, aerospace flight vehicles and so on. These sandwich plates in service can be simplified as the axially moving panel structures in the dynamic modeling. To research the dynamic behaviors of moving corrugated sandwich (CS) panels, an equivalent model is utilized. The energy method combined with penalty factor approach is applied to deduce the energy functions of the panel structure, and the corresponding formulations are further deduced based on the Hamilton's principle. Based on the proposed model, the examples with classical and elastic edge boundaries can be considered. Several computational examples are implemented to verify the present formulations, and satisfactory consistency can be observed. Meanwhile, impacts of several structural parameters on the dynamic and stability properties of the CS panel are investigated. To suppress the vibration of CS panels, the negative capacitance piezoelectric shunt damping circuit (PSDC) is further adopted. The impacts of the velocity parameter on the optimal values of the PSDC are discussed and calculated results demonstrate that dynamic responses of moving CS panels are satisfactorily attenuated by the proposed control strategy. [ABSTRACT FROM AUTHOR]

This study delineates the heat transfer through multilayer fire retardant fabrics exposed to different levels of a purely radiant heat source with an air gap between fabric and skin. This numerical model critically focuses on different distances (longitudinal, transverse, and angular) of the firefighters from the heat source. This investigation considers the effect of dynamic change of longitudinal, transverse, and angular distance from the heat source through the motion of the firefighters and also considers the reflectivity of the outer layer of the multilayer fabric to predict the safe time and distance of the firefighters from the radiant heat source to avoid serious thermal damage. Finally, the study explains the effect of reflectivity of the fabric, multi directional motion of the firefighters, and different levels of radiant heat fluxes to assess the safe zone for the firemen to restrict their motion in order to obliterate the second and third degree thermal injury. [ABSTRACT FROM AUTHOR]

Tunnel fires create dense black smoke that covers ceiling lights and darkens tunnel spaces. The present study investigates experimentally the evacuation speed in a full-scale tunnel filled with smoke and clarifies the relation between the extinction coefficient (up to 1.6 m −1 ) and normal walking speed. In this study, participants were exposed to smoke in a full-scale experimental tunnel that was darkened by turning off the ceiling lights, and the extinction coefficient was varied from 0.18 to 1.6 m −1 . The maximum, minimum, and mean normal walking speeds were almost constant up to 1.0 m −1 but decreased slightly at higher extinction coefficients. At 0.30 m −1 , the maximum emergency-evacuation speed through the dark tunnel is less than that when the ceiling lights are on and corresponds to 2.6 m/s, thereby indicating a fast walking speed even at small extinction coefficients. However, the maximum emergency-evacuation speeds at coefficients exceeding 0.48 m −1 for light and dark conditions are almost identical. The minimum and mean emergency-evacuation speeds decrease at extinction coefficients of approximately 1.0 m −1 . Additionally, normal walking speed and emergency-evacuation curves are calculated from the current experimental results to compare the effect of ceiling lights with that of a darkened space. The results indicate that the normal walking speed and emergency-evacuation speed are influenced by the darkened space. [ABSTRACT FROM AUTHOR]

Storm surges are among the most devastating natural hazards occurring in coastal regions of Zhejiang Province. A nested tidal model is built to simulate the storm surge generated by typhoons with varied velocities. Two typhoons with extreme moving speeds (Mary and Kai-tak, with low and high moving speeds, respectively) between 1949 and 2020 are simulated and analyzed. To investigate the changes of storm surge and the influence of M 2 tide caused by the moving speed, three different moving speeds (2.0, 1.0 and 0.5 times) are studied based on Chan-hom. The results show that: The landing intensity of the low moving speed typhoon is weaker than that of the high moving speed typhoon, but the former has a longer-lasting impact on the storm surge. When the moving speed is slower, the wind points towards the shore for a longer time, which increases the average water level in the area from the west of the Zhoushan sea area to the Qiantang River. With the decrease of typhoon moving speed, the amplitude of the tide decreases, while the change of lag angle varies in different water areas. • 218 typhoon tracks of Zhejiang Province from 1949 to 2020 were drawn according to the typhoon intensity. • Storm surge process under typical moving typhoon was simulated. • Characteristics of wind speed and influence of storm surge process under different typhoon moving speeds were studied. • Spatial distribution of storm surge at different moving speeds and influence of moving speed on M 2 tidal component were discussed. [ABSTRACT FROM AUTHOR]

Prediction of subsoil deformation under traffic loading requires honoring the dynamic nature of moving wheel loads and representing the stress path caused by such loads. A practical method in the framework of the layerwise summation procedure is proposed here for predicting the settlement of road overlaid on soft subsoil caused by traffic loading. The proposed method consists of a simplified approach for calculating the wheel load-induced stress and an empirical model for describing the accumulation of residual strain. Two amplification coefficients are introduced to account for the effect of moving speed on deviator stress and horizontal shear stress, respectively. The analytical solutions of the two amplification coefficients, which can be evaluated numerically, are deduced, and numerical results are presented in charts. Hence, the wheel load-induced stress in subsoil at different moving speeds can be calculated by multiplying the stress from a commonly used pseudostatic method with the values of the two amplification coefficients read from the charts. In addition, an empirical model is proposed for calculating the accumulation of residual strain in the subsoil under repeated heart-shaped stress cycles induced by traffic loading. The model is calibrated by simulating cyclic torsional shear tests of different clays. Providing the induced accumulated strain of the subsoil, the settlement of a road that results from traffic loading can be predicted by following the layerwise summation procedure. The performance of the proposed method is demonstrated by simulating the traffic loading-induced settlement of Saga Airport Road as an example. [ABSTRACT FROM AUTHOR]

The paper describes full-scale fire-fighting tests performed in an underground mine. A total of six different methods to fight a full scale fire in a mine tunnel were tested. The methods involved different fire-fighting equipment but were comparable regarding fundamental conditions such as length of response-route, fire-fighting set-up, and smoke and fire size. The aim was to compare different equipment and methods to reach and eventually extinguish the fire. Fire fighters using breathing apparatus (BA) were monitored regarding air consumption, movement speed and local actions and decisions. The results are presented and analyzed in respect to fire-fighting efficiency, front BA operations including moving speed and performed actions, as well as the time to successfully put out the fire. Measurements of heat release rates, temperatures and moving speeds are given in order to quantify the efficiency of the operation. Results indicate that a timespan of 15-30 min is needed for the firefighters to reach the fire source and achieve the extinguishing criteria in five of the tests. The standard equipment and nozzles shows good performance in the tests. A limiting factor on the firefighter's endurance is the amount of air that is available. As a result from these findings the endurance of BA-teams could improve if focus is put on team organization, lightweight equipment and air supply. [ABSTRACT FROM AUTHOR]

The Tibetan Plateau Vortex (TPV) is mainly divided into east moving (E-TPV), northeast moving (NE-TPV) and so on according to its moving path after moving off the Tibetan Plateau (TP). Based on the database of TPV from 1979 to 2018, this paper mainly makes statistical analysis on the NE-TPV in summer. According to its moving-off position, NE-TPV is subdivided into westward vortex (denoted as NE I -TPV) and eastward vortex (denoted as NE II -TPV). In terms of source, structure, circulation, moving speed, life history and influence on precipitation, the characteristics of two types of NE-TPVs were analyzed and compared with E-TPV to reveal the activity characteristics of the NE-TPVs and the similarities and differences between them. The results show that: (1) The NE I -TPV is mainly generated in the northwest of the TP, while the NE II -TPV and E-TPV are generated in the whole TP. There are mainly three centers of vortex sources: west, middle and east. The eastern sources of TPV with different paths differ greatly in north-south location and concentration. The eastern source of NE I -TPV is northward and concentrated, while the E-TPV is southward and dispersed, and NE II -TPV is between the former two. (2) The intensity of NE II -TPV is stronger than that of NE I -TPV before moving off, and the ascending motion of these two is located near the vortex center. After moving off, the relative vorticity and vertical velocity of both of them weakened significantly, and the maximum upward movement of NE I -TPV moved to the northeast of the vortex, while the NE II -TPV is similar to E-TPV, and its rising region is located in the southeast of the vortex. (3) The moving direction before moving off and moving-off position of TPV is mainly affected by the 200 hPa westerly fluctuations, while after moving off, the moving direction is mainly affected by 500 hPa troughs and ridges. Among them, the Hetao High-Pressure Ridge is particularly important in blocking NE-TPV. (4) Besides the influence of altitude difference, the moving speed of TPV is closely related to its moving direction, so the TPV moving eastward move faster. (5) NE II -TPV and E-TPV have longer mean life history than NE I -TPV, meanwhile, they often result in a wider range of precipitation and a higher proportion of rainstorms. The precipitation of NE I -TPV is mainly located in the Hexi Corridor. While the precipitation of NE II -TPV is mainly located in the eastern part of Northwest China. • According to its moving-off position, the northeast moving Tibetan Plateau Vortex (NE-TPV) is subdivided into westward vortex (denoted as NE I -TPV) and eastward vortex (denoted as NE II -TPV). • It is found that TPV mainly has three sources, which are located in the west, the middle and the east of the TP. The eastern source of TPVs with different paths is quite different. • After moving off the TP, the maximum ascending motion of NE I -TPV is located in the northeast side of the vortex, while that of NE II -TPV is located in the southeast side of the vortex, just like the E-TPV. • On the one hand, the moving speed of TPV is affected by the altitude difference. On the other hand, it is also related to the moving direction. [ABSTRACT FROM AUTHOR]

Compaction is one of the restricting factors in desirable seed germination and root growth. As a sign for soil compaction can be a criterion for optimal seed germination. Seeds require some compression of the surrounding soil at planting for optimum growth, which it is made by pressure wheels in planters. Travel speed and working depth affect the soil cone index. A field experiments were conducted to evaluate the effects of the speed and working depth in the beginning of the autumn season. Experiments were performed in the form of factorial split-plot based on a randomized complete block design with two factors, the travel speed (3, 4, and 6 km/h) and working depth (3, 6, 9, 12 and 15 cm) in three replication. Digital cone Penetrometer was used for measuring soil cone index of sandy-loamy soil at the depths ranging from 1 to 20 cm. The results showed that the cone index reduced by the increasing of average speed, also the cone index Increased with the increasing depth. [ABSTRACT FROM AUTHOR]

This paper develops the solution for the generalized thermoelastic vibration of an axially moving microbeam resonator induced by sinusoidal pulse heating. The system of governing equations is reduced to a novel six-order thermoelastic differential equation in terms of either deflection or temperature. The Laplace transformation method is used to determine the deflection, temperature, axial displacement, and bending moment of the microbeam. The effects of phase-lag and width of the sinusoidal pulse are studied and represented graphically. The effect of the moving speed on the microbeam resonator is also investigated. [ABSTRACT FROM AUTHOR]

Bridges play an increasingly more important role in modern transportation, which is why many sensors are mounted on it in order to provide safety. However, supplying reliable power to these sensors has always been a great challenge. Scavenging energy from bridge vibration to power the wireless sensors has attracted more attention in recent years. Moreover, it has been proved that the linear energy harvester cannot always work efficiently since the vibration energy of the bridge distributes over a broad frequency band. In this paper, a nonlinear energy harvester is proposed to enhance the performance of harvesting bridge vibration energy. Analyses on potential energy, restoring force, and stiffness were carried out. By adjusting the separation distance between magnets, the harvester could own a low and flat potential energy, which could help the harvester oscillate on a high-energy orbit and generate high output. For validation, corresponding experiments were carried out. The results show that the output of the optimal configuration outperforms that of the linear one. Moreover, with the increase in vehicle speed, a component of extremely low frequency is gradually enhanced, which corresponds to the motion on the high-energy orbit. This study may give an effective method of harvesting energy from bridge vibration excited by moving vehicles with different moving speeds. [ABSTRACT FROM AUTHOR]

Abstract: Using an updated high-temperature superconductor (HTS) maglev measurement system, electromagnetic forces between a YBaCuO bulk superconductor and a permanent magnet (PM) have been measured under different cooling height (CH) and different lateral moving speed of the PM. It is found that the influence of the moving speed on both the levitation and lateral force is substantial and as such the results shown in this work are a benefit to the understanding of levitation systems. [Copyright &y& Elsevier]

Abstract: An experimental observation is presented a crossing in the force–displacement hysteretic curve of a melt processed high-temperature superconductor (HTS) with high critical current density. The causes of the crossing were listed and discussed. In addition, the influence of the speed of the permanent magnet (PM) on the maximum levitation force was measured in this work. It was found that both with and without the crossing in the hysteretic curve, with the increase of the moving speed of the PM, the maximum levitation force of the HTS with high critical current density decreases gradually. We interpret these results by analyzing the power dissipation in the HTS when the PM moved above the superconductor. [Copyright &y& Elsevier]

Abstract: Two single-domain YBCO bulks with different grain orientations were used to investigate the effect of relative moving speed between the magnet and YBCO bulk, on their interaction force at LN2 temperature under zero field cooling (ZFC) state. It is found that the levitation force of the sample S1 with c-axis perpendicular to the top surface is higher than that of the sample S2 with c-axis parallel to the top surface; the maximum levitation force (F ML) is increasing with the increase of relative moving speed (V RMS) between the magnet and the samples at first and reaches a peak value for sample S1 and a peak zone values for sample S2, then the F ML decreases with the increase of V RMS; the stiffness between the samples and the magnet is decreasing with the increase of the V RMS. This result is useful for the application of superconducting levitation. [Copyright &y& Elsevier]