Shaking table testing and numerical modeling of continuous welded ballast track on bridges under longitudinal seismic loading

In order to confirm the validity of the ideal elasto-plastic resistance model applied to the ballast track under seismic loading, this paper studies the seismic response of continuous welded ballast track on bridges through the shaking table test and presents a process of updating the model based on the test results. The results indicate that the track constraint can improve the low order natural frequency of bridges significantly, and reduce the displacement response of the bridge. When ballast beds are effectively in a dynamic reciprocating state while under seismic loading, a structural change between the granules will occur, wherein some will flow and redistribute. The dynamic hysteretic change of the ballast longitudinal resistance is complex and quite different from that of the ideal elasto-plastic hysteretic route, and the ballast longitudinal resistance performance degenerates. If ballast longitudinal resistance is assumed to be ideal elastic-plastic resistance, the actual beam displacement response will be underestimated and the calculated rail seismic force will be greater than the test result. Moreover, the equivalent stiffness coefficient Ke and damping coefficient Ce of the ballast dynamic resistance characteristics could be obtained by model updating, and the simulation results coincide well with the test results

A Hybrid Wavelet de-noising and Rank-Set Pair Analysis approach for forecasting hydro-meteorological time series

Accurate, fast forecasting of hydro-meteorological time series is presently a major challenge in drought and flood mitigation. This paper proposes a hybrid approach, wavelet de-noising (WD) and Rank-Set Pair Analysis (RSPA), that takes full advantage of a combination of the two approaches to improve forecasts of hydro-meteorological time series. WD allows decomposition and reconstruction of a time series by the wavelet transform, and hence separation of the noise from the original series. RSPA, a more reliable and efficient version of Set Pair Analysis, is integrated with WD to form the hybrid WD-RSPA approach. Two types of hydro-meteorological data sets with different characteristics and different levels of human influences at some representative stations are used to illustrate the WD-RSPA approach. The approach is also compared to three other generic methods: the conventional Auto Regressive Integrated Moving Average (ARIMA) method, Artificial Neural Networks (ANNs) (BP-error Back Propagation, MLP-Multilayer Perceptron and RBF-Radial Basis Function), and RSPA alone. Nine error metrics are used to evaluate the model performance. Compared to three other generic methods, the results generated by WD-REPA model presented invariably smaller error measures which means the forecasting capability of the WD-REPA model is better than other models. The results show that WD-RSPA is accurate, feasible, and effective. In particular, WD-RSPA is found to be the best among the various generic methods compared in this paper, even when the extreme events are included within a time series

Role of thioredoxin nitration in bleomycin (BLM)-induced pulmonary fibrosis in rats

Oxidant stimulation has been suggested to play an important role in the pathogenesis of idiopathic pulmonary fibrosis (IPF). Our study aimed to investigate the role and mechanisms of thioredoxin (Trx) nitration during the development of IPF. Rat IPF model was established by intratracheal instillation of bleomycin (BLM). Male Wistar rats were randomly divided into control group and BLM-treated group in which rats were intratracheally instilled with a single dose of BLM (5.0 mg/kg body weight in 1.0 ml phosphate buffered saline). At 7 or 28 days after instillation, rats were euthanized. Histopathologic and biochemical exams were performed. The activity and protein level of thioredoxin were assessed. The thioredoxin nitration level was determined using immunoprecipitation (IP) and immunoblotting (IB) techniques. Our results demonstrated that protein tyrosine nitration increased in BLM group compared with control group. Trx activity decreased in BLM group compared with control group, while its expression and nitration level increased dramatically in BLM group compared with control group. Our results indicated that Trx nitration might be involved in the pathogenesis of IPF.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Longitudinal Seismic Response of Continuously Welded Track on Railway Arch Bridges

The seismic response of continuously welded track on bridges is seeing increased interest. Taking the railway deck arch bridge as an example, a track–bridge spatial coupling finite element model was established, and the effects of arch rib temperature difference and bridge span layout on rail seismic force were analyzed. The results show that the peak rail seismic force is larger than the maximum expansion force, and thus track constraints should be taken into consideration in railway arch bridge seismic design. The area enclosed by the hysteresis curve of track resistance increases gradually with an increase in dynamic displacement, and under seismic loading the track constraints can be considered to be in a relatively stable state of energy dissipation. The rail seismic forces under different waves varied greatly, so a wave whose spectrum characteristics fit the bridge site well should be used. The beam temperature difference can affect the structural seismic response, but this effect can be ignored when only considering the maximum rail seismic force. With the application of a series of three continuous beams on the arch and the reasonable arrangement of fixed bearings and speed locks, the track longitudinal stress deformation during an earthquake outperforms that of supported beams

New Intrinsic Ecological Mechanisms of Leaf Nutrient Resorption in Temperate Deciduous Trees

Leaf nutrient resorption is a critical process in plant nutrient conservation during leaf senescence. However, the ecological mechanisms underlying the large variability in nitrogen (NRE) and phosphorous (PRE) resorption efficiencies among trees remain poorly understood. We conducted a comprehensive study on NRE and PRE variability using 61 tree individuals of 10 temperate broad-leaved tree species. Three potentially interrelated intrinsic ecological mechanisms (i.e., leaf senescence phenology, leaf pigments, and energy residual) were verified. We found that a delayed leaf senescence date, increased degradation of chlorophylls and carotenoids, biosynthesis of anthocyanins, and reduced nonstructural carbohydrates were all positively correlated with NRE and PRE at the individual tree level. The intrinsic factors affecting resorption efficiency were ranked in decreasing order of importance: leaf pigments > energy residual > senescence phenology. These factors explained more variability in NRE than in PRE. Our findings highlight the significance of these three ecological mechanisms in leaf nutrient resorption and have important implications for understanding how nutrient resorption responds to climate change