Precipitant Effects On Aggregates Structure Of Asphaltene And Their Implications For Groundwater Remediation

© 2020 by the authors. Asphaltenes generally aggregate, then precipitate and deposit on the surfaces of environmental media (soil, sediment, aquifer, and aquitard). Previous studies have recognized the importance of asphaltene aggregates on the wettability of aquifer systems, which has long been regarded as a limiting factor that determines the feasibility and remediation efficiency of sites contaminated by heavy oils. However, the mechanisms/factors associated with precipitant effects on asphaltene aggregates structure, and how the precipitant effects influence the wettability of surfaces remain largely unknown. Here, we observe the particle-by-particle growth of asphaltene aggregates formed at different precipitant concentrations. Our results show that aggregates for all precipitant concentrations are highly polydisperse with self-similar structures. A higher precipitant concentration leads to a more compacted aggregates structure, while precipitant concentration near to onset point results in a less compact structure. The well-known Smoluchowski model is inadequate to describe the structural evolutions of asphaltene aggregates, even for aggregation scenarios induced by a precipitant concentration at the onset point where the Smoluchowski model is expected to explain the aggregate size distribution. It is suggested that aggregates with relative high fractal dimensions observed at high precipitant concentrations can be used to explain the relatively low Stokes settling velocities observed for large asphaltene aggregates. In addition, asphaltene aggregates with high fractal dimensions are likely to have high density of nanoscale roughness which could enhance the hydrophobicity of interfaces when they deposit on the sand surface. Findings obtained from this study advance our current understandings on the fate and transport of heavy oil contaminants in the subsurface environment, which will have important implications for designing and implementing more effective and efficient remediation technologies for contaminated sites

Discriminative pruning of language models for Chinese word segmentation

This paper presents a discriminative pruning method of n-gram language model for Chinese word segmentation. To reduce the size of the language model that is used in a Chinese word segmentation system, importance of each bigram is computed in terms of discriminative pruning criterion that is related to the performance loss caused by pruning the bigram. Then we propose a step-by-step growing algorithm to build the language model of desired size. Experimental results show that the discriminative pruning method leads to a much smaller model compared with the model pruned using the state-of-the-art method. At the same Chinese word segmentation F-measure, the number of bigrams in the model can be reduced by up to 90%. Correlation between language model perplexity and word segmentation performance is also discussed.

Precipitant Effects on Aggregates Structure of Asphaltene and Their Implications for Groundwater Remediation

Asphaltenes generally aggregate, then precipitate and deposit on the surfaces of environmental media (soil, sediment, aquifer, and aquitard). Previous studies have recognized the importance of asphaltene aggregates on the wettability of aquifer systems, which has long been regarded as a limiting factor that determines the feasibility and remediation efficiency of sites contaminated by heavy oils. However, the mechanisms/factors associated with precipitant effects on asphaltene aggregates structure, and how the precipitant effects influence the wettability of surfaces remain largely unknown. Here, we observe the particle-by-particle growth of asphaltene aggregates formed at different precipitant concentrations. Our results show that aggregates for all precipitant concentrations are highly polydisperse with self-similar structures. A higher precipitant concentration leads to a more compacted aggregates structure, while precipitant concentration near to onset point results in a less compact structure. The well-known Smoluchowski model is inadequate to describe the structural evolutions of asphaltene aggregates, even for aggregation scenarios induced by a precipitant concentration at the onset point where the Smoluchowski model is expected to explain the aggregate size distribution. It is suggested that aggregates with relative high fractal dimensions observed at high precipitant concentrations can be used to explain the relatively low Stokes settling velocities observed for large asphaltene aggregates. In addition, asphaltene aggregates with high fractal dimensions are likely to have high density of nanoscale roughness which could enhance the hydrophobicity of interfaces when they deposit on the sand surface. Findings obtained from this study advance our current understandings on the fate and transport of heavy oil contaminants in the subsurface environment, which will have important implications for designing and implementing more effective and efficient remediation technologies for contaminated sites

Optimization Method for Conventional Bus Stop Placement and the Bus Line Network Based on the Voronoi Diagram

With the rapid development of the economy, the existing conventional bus transit system finds it difficult to meet people’s increasing travel needs. In addition, with the emergence and rapid development of urban rail transit, it is also necessary to integrate the existing conventional bus transit system with the rail transit system to realize the optimization of the whole public transport system. This study introduces the concept of the Voronoi diagram and uses it to divide the service area of bus stops. Taking the average walking time of regional passengers to the station as the main index, the convenience of passengers in the service area was evaluated, and a set of candidate station sites is established. Against the background of urban rail transit, a complete optimization model for a conventional bus station layout and line network was proposed. Finally, taking Wuhan East Lake High-tech Development Zone as an example, two optimization schemes for the public transport system were obtained. Compared with the status quo, the optimized scheme had obvious improvement effects on the repetition coefficient of bus lines, per capita transfer time, bus line network coverage and station service rate. This has been recognized by the local authorities, which proves the practicality and scientificity of the optimization method of this study

Research on Traffic Design of Urban Vital Streets

As an important part of urban public spaces, the urban street is an important place for people’s lives, communication, and activities. Its vitality directly affects the vitality of the whole city. It is of great practical significance to examine the current situation and theoretical development of urban streets in China and reconstruct the vitality of streets from the perspective of the traffic users. Based on the “people-oriented” design concept of street traffic, this study took street sections and intersections as the main research object, proposed an overall layout of traffic, space, and facilities. A complete set of humanized and green traffic design methods was constructed to enhance the street vitality. First, through the analysis of the concept of road and street, the traffic connotations of the vital street was determined, the characteristics of the vital street was investigated, and the constituent elements of the vital street was summarized. Then, with a focus on people’s needs, the vital street traffic design methods were mainly divided into two parts: vital street section traffic design and vital street intersection design. Finally, Zhongshan Avenue in Wuhan City was chosen for empirical analysis. Through a field questionnaire survey, the traffic characteristics and traffic demands of residents on Zhongshan Avenue were analyzed, and the traffic design of Zhongshan Avenue was carried out in combination with the traffic design method proposed in this study. The results showed that people’s satisfaction with the renovated Zhongshan Avenue reached 90%. Buses, subways, bicycles, and walkways have become the four major green transportation modes for people to arrive at and leave Zhongshan Avenue, and the renovated Zhongshan Avenue has become a vibrant living street

Optimization Method for Conventional Bus Stop Placement and the Bus Line Network Based on the Voronoi Diagram

With the rapid development of the economy, the existing conventional bus transit system finds it difficult to meet people’s increasing travel needs. In addition, with the emergence and rapid development of urban rail transit, it is also necessary to integrate the existing conventional bus transit system with the rail transit system to realize the optimization of the whole public transport system. This study introduces the concept of the Voronoi diagram and uses it to divide the service area of bus stops. Taking the average walking time of regional passengers to the station as the main index, the convenience of passengers in the service area was evaluated, and a set of candidate station sites is established. Against the background of urban rail transit, a complete optimization model for a conventional bus station layout and line network was proposed. Finally, taking Wuhan East Lake High-tech Development Zone as an example, two optimization schemes for the public transport system were obtained. Compared with the status quo, the optimized scheme had obvious improvement effects on the repetition coefficient of bus lines, per capita transfer time, bus line network coverage and station service rate. This has been recognized by the local authorities, which proves the practicality and scientificity of the optimization method of this study

Effects of Visual Active Deceleration Devices on Controlling Vehicle Speeds in a Long Downhill Tunnel of an Expressway

Because the inside of a road tunnel is a closed strip, the driving environment changes suddenly at the tunnel entrance and exit, which is why accidents occur more frequently in tunnels than elsewhere. Based on visual psychology, reverse-perspective-illusion deceleration lines (RPIDLs) and visual-intervention deceleration devices (VIDDs) were designed to control vehicle speeds near the entrance and in the middle of a tunnel, respectively. Then, to assess the speed-controlling performance of the RPIDLs and VIDDs for vehicles in a long downhill tunnel, laser velocimeters were used to measure the vehicle speeds at different observation points in the tunnel before and after implementing the RPIDLs and VIDDs. The results show that the RPIDLs and VIDDs decreased the average vehicle speed and controlled its dispersion effectively. The 60 m RPIDLs improved the traffic safety in the tunnel without lessening the passing ability therein. The slash-line VIDD had no obvious effect on the maximum vehicle speeds in the middle of the tunnel. Both the 90° fold-line VIDD and the four-yellow–four-white VIDD decreased the maximum vehicle speeds significantly. The 60 m RPIDLs and the 90° fold-line VIDD gave the best deceleration effect on vehicles near the entrance and in the middle of the tunnel, respectively, and controlled the average speed and its dispersion effectively

Momordica Charantia Polysaccharides Attenuates MPP+-Induced Injury in Parkinson’s Disease Mice and Cell Models by Regulating TLR4/MyD88/NF-κB Pathway

Objective. To investigate the potential role of Momordica charantia polysaccharides (MCPs) in Parkinson’s disease (PD) and reveal the molecular mechanism of its function. Method. 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and 1-methyl-4-phenylpyridinium (1-methyl-4-phenylpyridinium, MPP+) were used to establish PD mice and cell models. The mice and cells were divided into 4 groups: Control group, Control+MCPs group, PD group, and PD+MCPs group. Pole climbing experiment and Rotarod experiment were used to observe the coordination ability of mice. High-performance liquid chromatography and enzyme-linked immunosorbent assay (ELISA) were used to determine neurotransmitters and metabolites, inflammatory factors TNF-α and IL-1β, oxidative stress-related markers SOD, MDA, and GSH in striatum tissues. Western blot was used to determine the protein levels of tyrosine hydroxylase (TH), oxidative stress-related protein Cytochrome C (Cytochrome C), and apoptosis-related proteins Bcl-2, Bax, and cleaved Caspase-3 in tissues and cells. Moreover, flow cytometry, PI staining, and fluorescence were used to observe cell apoptosis. Finally, the activation effect of MCPs on TLR4/MyD88/NF-κB signaling pathway was observed and verified. Results. Compared with the Control group, MPTP treatment can induce brain damage in mice (all P<0.05), change the metabolic state of neurotransmitters (all P<0.05), induce inflammation (all P<0.05), and induce apoptosis and the occurrence of oxidation reaction (all P<0.05); however, MCPs treatment can significantly reverse the above changes (all P<0.05). In cell models, studies have found that MCPs can play a protective role by regulating the activation state of TLR4/MyD88/NF-κB pathway. Conclusion. This study found that the application of MCPs therapy can play anti-inflammatory, antioxidative stress, and antiapoptotic effects in PD by regulating the activation of the TLR4/MyD88/NF-κB pathway