After the 2008 Ms 8.0 Wenchuan earthquake, a huge amount of loose debris materials were accumulated on the surface of slopes in the mountainous areas of Southwestern China. Under heavy rainfalls and ...earthquakes, these loose debris materials can flow, washed away, and subsequently enter the mountainous rivers due to landslides and debris flows. They can change the sediment supply of the river channel and result in the adjustment of riverbed. To mitigate the adverse impacts, baffles are usually installed on slopes in front of the protected areas to reduce the kinetic energy of incoming debris flows. In order to clarify the interacting mechanism between debris materials and baffles structure, the dynamics of granular transportation and deposition in a typical gully have been analyzed via the three-dimensional discrete element method (DEM). The numerical results indicate that the arrangement of baffles (e.g., spacing distance, layout row, and height) has a significant influence on the dissipation of debris energy and the final sediment deposition pattern. The kinetic energy, the velocity of granular flow, and the total mass of debris materials entering the river channel decrease with the increase of the baffles lateral spacing distance, layout row, and height. Correspondingly, the amount of debris materials retained by the baffles will increase. Thickness and volume of particle deposits in the upstream region increased with increase in lateral spacing, rows, and height of the baffles, but decreased in the downstream area. In addition, the baffle configuration can affect the particle size distribution along the channel. The results of this research can provide a theoretical basis for baffle designs and the prevention of debris flows in mountainous areas.
The impact of particles on slope bed is not only one of the main processes of eolian saltation, but also lead to the sand surface damage and provide sufficient materials for the sediment supply ...process in desert rivers. In order to reveal the mechanism of excessive sediment supply in desert rivers, it is necessary to study the grain-bed impact process, which plays an important role on the wind erosion. In this study, based on the discrete element method (DEM) and previous researches, a three-dimensional numerical simulation is carried out to study the influence of the incident angle, incident angle, and lateral incident angle on grain-bed collision under different bed surfaces. Finally, by fitting the simulation data, we give the three-dimensional splash function of ejection velocity, ejection angle, and lateral ejection angle as well as lateral ejection velocity with the change of impact velocity, impact angle, and lateral impact angle on different bed surface. This study will enhance our understanding of the processes of eolian sand movement and will provide useful information about the mechanisms that drive sediment replenishment to desert rivers.
Since the establishment of the world-class Three Gorges Dam (TGD) across the Yangtze River, China, the downstream reach has experienced a long-term adjustment with regard to the river morphology and ...hydrodynamics, imposing a profound impact on the environmental conditions of human living and aquatic ecosystem. This study presents an investigation on the river channel morphological characteristics and hydrodynamic environment of a large bifurcation-confluence complex downstream of the TGD through detailed field survey and numerical modeling. Results show that the main stem, before being bifurcated into two sub-channels (the North Channel and the South Channel), experiences a meander, leading to the severe bed scouring near the outer bank (pools) resulted from a high flow mass flux and bed shear stress. Because of being bifurcated, the river width with largely growing may result in the reduction of flow velocity and sediment deposition (riffles), and thereby two plugbars are formed near the entrance of two sub-channels. In the meantime, the velocity-reversal phenomenon (flow velocity and friction velocity) is identified when low flows are transited into high flows. The flow mass flux, however, is always larger in pool regions, which is highly related to water depth. As a result, the topographic steering of flows by riffles, bars and floodplains may have more impact on flow path under low flow conditions, while the bankline shape would become more important under high flows. Furthermore, the topographic steering could play a key role in the pattern of flow separations near the confluence. More interestingly, the confluence flow separation only occurs under low flow conditions and its occurring location shifts upwards the tributary (the North Channel), which differs from observations in previous studies. The visualized numerical results of friction velocity distribution indicate that sediment is more likely to deposit in the North Channel (entrance) with lower friction velocity, implying the potential closure of the sub-channel.
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•High-volume water power dam imposes high impacts on the downstream morphological and hydrodynamic environment.•Large river bar centers the main stem, forming a bifurcation-confluence complex.•Field investigations provide detailed morphological characteristics and typical hydrodynamic information.•Numerical modeling shows bifurcation-confluence hydrodynamics after the dam construction.•Hydrodynamics are highly inter-related to the morphological characteristics, implying the future morphological evolution.
Alzheimer ’s disease（ A D） is a progressive neurodegenerative disorder characterized by extracellular senile plaques and intracellular neurofibrillary tangles.Many microRNAs（miRs） participate in ...regulating amyloid β（Aβ） formation and the metabolism of tau protein in the process of AD,and some are up-regulated in AD patients or transgenic models of AD.However,the role of miR-98 in AD remains unclear.Here,we showed that the expression of miR-98 was negatively correlated with the insulin-like growth factor 1（IGF-1） protein level in APP/PS1 mice.MiR-98 target sites in IGF-1 were confirmed by luciferase assay in HEK293 cells.Overexpression of miR-98 in N2a/APP cells down-regulated the IGF-1 protein level and promoted Aβ production,whereas inhibition of miR-98 in N2a/APP cells up-regulated the IGF-1 protein level and suppressed Aβ production.Furthermore,overexpression of miR-98 in N2a/WT cells increased the phosphorylation of tau,whereas inhibition of miR-98 reduced it.These results suggest that miR-98 increases Aβ formation and tau phosphorylation by inhibiting the translation of IGF-1,which might provide a therapeutic strategy for AD.
碩士
中國文化大學
材料科學與奈米科技研究所
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Fabric materials that it is used to reinforce the rubber in Taiwan are usually the high strength polyester, but polyester has Hydrophobic, it will be quite technical on the ...interface. This research is study the conveyor belt fabric pretreatment by far infrared heater and adding Methylenediphenylisocyanate to RFL solution in dipping process, the purpose is raised the adhesion strength between fabric and rubber, in far infrared treatment, to change the gauge between fabric and heater, the gauge is divided to 5cm, 6cm and 7 cm, the purpose is decrease the moisture content of fiber, and raised the absorption of fabric dipping RFL solution. To analyze the break strength, fiber structure, and adhesion strength after the fabric treated by far infrared. And RFL solution adding Methylenediphenylisocyanate can be reduce the interface problem between fabric and rubber, to raise the adhesion strength. In this study, to change the RFL solution formula of 22% and 23%, and adding Methylenediphenyli
In this paper, with the aid of symbolic computation, we present a uniform method for constructing soliton solutions and periodic solutions to （2＋1）-dimensional Toda lattice equation.
Background Three randomised trials have demonstrated that combining bevacizumab with first-line chemotherapy significantly improves progression-free survival versus chemotherapy alone in ...HER2-negative locally recurrent/metastatic breast cancer （LR/mBC）. However, data from Chinese populations are limited and possible differences between ethnic and geographic populations are unknown. This study was conducted to determine whether there are differences in safety and efficacy in patients with HER2-negative LR/mRC between Chinese and Western populations after they receive first-line bevacizumab combined with taxane-based therapy.
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