The Excitation of Guided-waves by Underground Point Source: an Investigation with Theoretical Seismograms

AbstractNear-Source scattering of Rg into S appears to be the primary contributor to the low-frequency Lg. The authors further suggest that the prominent low-frequency spectral null in Lg is due to Rg from a compensated linear vector dipole (CLVD) source, and the low-frequency null in Rg excitation is due to a zero-crossing of the horizontal displacement eigenfunctions. In this study, the mechanism of the excitation of Lg from explosions in layered earth structures are analyzed with theoretical seismograms. Our result shows that the CLVD source generates prominent Lg waves,and the null in the Lg spectra showing remarkably good agreement with those expected from Rg due to a CLVD source. We conclude that the derivative of displacement eigenfunction also takes a key role in the excitation of the null, only zero-crossing of the horizantall displacement eigenfunction can not fully explain it

Use of Structural Equation Modelling and Neural Network to Analyse Shared Parking Choice Behaviour

The shared parking mode represents a feasible solution to the persistent problem of parking scarcity in urban areas. This paper aims to examine the shared parking choice behaviours using a combination of structural equation modelling (SEM) and neural network, taking into account both the parking location characteristics and the travellers’ characteristics. Data were collected from a commercial district in Nanjing, China, through an online questionnaire survey covering 11 factors affecting shared parking choice. The method involved two steps: firstly, SEM was applied to examine the influence of these factors on shared parking choice. Following this, the seven factors with the strongest correlation to shared parking choice were used to train a neural network model for shared parking prediction. This SEM-informed model was found to outperform a neural network model trained on all eleven factors across precision, recall, accuracy, F1 and AUC metrics. The research concluded that the selected factors significantly influence shared parking choice, reinforcing the hypothesis regarding the importance of parking location and traveller characteristics. These findings provide valuable insights to support the effective implementation and promotion of shared parking

Impacts of snow accumulation on air temperature measured by automatic weather stations on the Antarctic ice sheet

The heights of automatic weather station (AWS) sensors over the Antarctic ice sheet are nominal and change with snow accumulation or ablation. Therefore, the measured data may not be used directly. In this study, we analyzed the impact of snow accumulation on AWS observations using continuous measurements from three AWS that were deployed on the traverse route from the Zhongshan Station to Dome A over East Antarctica. We then corrected the measured air temperature to account for changes in the sensor height relative to the snow surface to improve the authenticity and representativeness of the observation data from the AWS. The results show that (i) the annual mean snow accumulations at Dome A, Eagle and LGB69 were approximately 0.11 m, 0.30 m and 0.49 m, respectively, and the corresponding annual mean air temperature differences between the corrected and measured values at 1 m in height were 0.34℃, 0.29℃ and 0.35℃; (ii) the impact on air temperature from accumulation decreases with height from the surface; (iii) the air temperature difference between the corrected and measured values was not directly proportional to the snow accumulation but was related to the seasonal air temperature variations and the intensity of the local surface inversion; and (iv) the averaged corrected air temperature was higher than the measured values except during the summer when there were days without temperature inversion. The magnitude of the temperature difference between the corrected and measured was mainly determined by snow accumulation and the intensity of the local surface inversion

Successive-Stage Speed Limit on Exit Ramp Upstream of Direct-Type Freeway in China

The first objective of this study is to analyze a successive-stage speed limit model developed for vehicles along the exit upstream ramp of direct-type freeway in China. This paper 1 explains the necessity to implement speed limit to the exit ramp upstream, 2 analyzes whether speed limit is related to the length of the deceleration lane, vehicle type, saturation, and turning ratio and 3 proposes a speed prediction model and calibrates speed-limit sign validity model and establishes successive-stage speed limit model. The results. Δν 85 ≥ 10 illustrates the necessity of the using speed limit on the exit ramp. Speed-deceleration lane length curve presents two trends bounded by 200 m, so the speed limit should be in accordance with the deceleration length. Speed-small vehicle curve closing to speed-large vehicle curve presents that the vehicle type is not the factor of the speed limit. After curve fitting and polynomial regression, saturation is considered to be the most influential factor of speed. Speed-saturation prediction model and calibrated speed-limit sign validity model are built through linearization. According to the above results, successivestage speed limit model is established. An exit ramp was implemented to verify the feasibility and validity of the model

Experimental Study on Kaiser Effect of Reinforced Concrete Simply-Supported Beams

With the progress of transportation, an increasing number of bridges are put into operation, and the assessment of bridge bearing capacity is considered a significant measure to ensure bridge safety. As a critical approach for structural monitoring, acoustic emission is widely used in engineering projects. Since the Kaiser effect is an important phenomenon in acoustic emission, it is necessary to explore the Kaiser effect of reinforced concrete structures and the determination method of the Kaiser point. In this thesis, four reinforced concrete simply supported beams were utilized for the graded loading experiment under bending loads. After accumulating acoustic emission parameters, Kaiser point was selected for preliminary evaluation. Taking Kaiser point as the midpoint, the appropriate interval was determined. According to the continuity criterion of acoustic emission signals and the quadratic fitting curve based on experimental data, the Kaiser point was corrected by following the average growth rate of acoustic emission parameters. These simply supported beams were classified into two groups. One group was used to explore the acoustic emission characteristics when the load was less than the historical maximum, while the other group was used to analyze changes in the Kaiser effect with increasing load. Finally, based on the results of the specimen inspection, the influence of initial damage on the Kaiser effect was analyzed. The research results alleviated the influence of human factors on the determination of the Kaiser point and can serve as the theoretical basis for damage monitoring based on the Kaiser effect and bearing capacity evaluation of reinforced concrete structures