► Support Vector Regression approach is proposed to analyze the asymmetry in car following behavior. ► Intensity difference leads to a neutral line separating the speed-space diagram into two areas. ...► The neutral line determines the tilt angle and position of the hysteresis in the speed-space diagram. ► The leading vehicle’s states affect the internal and external shapes of the hysteresis. ► Magnitudes of deviations from equilibrium for micro- and macro-hysteresis are related.
This paper presents a self-learning Support Vector Regression (SVR) approach to investigate the asymmetric characteristic in car-following and its impacts on traffic flow evolution. At the microscopic level, we find that the intensity difference between acceleration and deceleration will lead to a ‘neutral line’, which separates the speed-space diagram into acceleration and deceleration dominant areas. This property is then used to discuss the characteristics and magnitudes of microscopic hysteresis in stop-and-go traffic. At the macroscopic level, according to the distribution of neutral lines for heterogeneous drivers, different congestion propagation patterns are reproduced and found to be consistent with Newell’s car following theory. The connection between the asymmetric driving behavior and macroscopic hysteresis in the flow-density diagram is also analyzed and their magnitudes are shown to be positively related.
Studies have shown that vehicle trajectory data are effective for calibrating microsimulation models. Light Detection and Ranging (LiDAR) technology offers high-resolution 3D data, allowing for ...detailed mapping of the surrounding environment, including road geometry, roadside infrastructures, and moving objects such as vehicles, cyclists, and pedestrians. Unlike other traditional methods of trajectory data collection, LiDAR’s high-speed data processing, fine angular resolution, high measurement accuracy, and high performance in adverse weather and low-light conditions make it well suited for applications requiring real-time response, such as autonomous vehicles. This research presents a comprehensive framework for integrating LiDAR sensor data into simulation models and their accurate calibration strategies for proactive safety analysis. Vehicle trajectory data were extracted from LiDAR point clouds collected at six urban signalized intersections in Lubbock, Texas, in the USA. Each study intersection was modeled with PTV VISSIM and calibrated to replicate the observed field scenarios. The Directed Brute Force method was used to calibrate two car-following and two lane-change parameters of the Wiedemann 1999 model in VISSIM, resulting in an average accuracy of 92.7%. Rear-end conflicts extracted from the calibrated models combined with a ten-year historical crash dataset were fitted into a Negative Binomial (NB) model to estimate the model’s parameters. In all the six intersections, rear-end conflict count is a statistically significant predictor (p-value < 0.05) of observed rear-end crash frequency. The outcome of this study provides a framework for the combined use of LiDAR-based vehicle trajectory data, microsimulation, and surrogate safety assessment tools to transportation professionals. This integration allows for more accurate and proactive safety evaluations, which are essential for designing safer transportation systems, effective traffic control strategies, and predicting future congestion problems.
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•Acetone was produced from DME with 73% selectivity.•DME carbonylation and subsequent ketonization were performed over Pyridine-modified H-MOR.•The ketonization of methyl acetate is ...promoted by carbonylation.•Pyridine blocked the active acids in the 12-membered ring main channel of H-MOR.•The ketonization of methyl acetate occurred via a ketene-mediated mechanism.
Acetone is currently produced by large amount of propylene and benzene, and its synthesis from a cheap and non-petroleum material has not yet been reported. Here, we present a new method for acetone production, which involves the carbonylation of dimethyl ether (DME) to methyl acetate and its subsequent ketonization to acetone over pyridine-modified H-mordenite. This convenient approach offers an acetone selectivity of 73% (CO2 excluded) and a DME conversion of 100% at 553 K. Spectral and isotopic studies revealed that the ketonization of methyl acetate was promoted by carbonylation, while the formation of a ketene intermediate was demonstrated by the formation of CH2DCOOD and two types of pyrones. A ketene-based ketonization mechanism was also proposed based on the kinetic isotope effect of CH2=13CO, indicating that the acetyl moiety contributed to the acyl part of acetone, while the ketene moiety was responsible for the alkyl part of acetone and the generation of CO2.
Decarbonylation of carboxylic acids is an effective reaction for alkene production but suffers from the requirement of homogeneous transitional-metal-based catalyst, ligand, and stoichiometric ...additive. Herein, we report the example of heterogeneous zeolite-catalyzed decarbonylation, in which acetic acid generates methyl acetate with a selectivity close to 90%, while propionic and butanoic acid provide ethylene and propylene, respectively, both with a selectivity of about 70% over pyridine-modified H-MOR. Decarbonylation of acetic acid proceeds via the generation of methanol by the cleavage of carbonyl CO from hydrogen-bonded acetic acid and the subsequent esterification to methyl acetate. Similarly, decarbonylation of propionic and butanoic acid correspondingly result in ethanol and propanol, which dehydrate rapidly to ethylene and propylene. This finding presents additional perspectives on decarbonylation of carboxylic acids and offers an approach for production of alkenes from biomass.
The Asian tropopause aerosol layer (ATAL) is an enhanced aerosol concentration layer in the upper troposphere and lower stratosphere over Asia, and it has important effects on radiation balance, ...atmospheric circulation, regional climate, and atmospheric chemical processes. However, despite its importance, the specific structure and long-term variation trend of the ATAL have been rarely analyzed, which is critical for assessing the impact of ATAL on climate change and evaluating the performance of climate models. This study compared and analyzed the three-dimensional spatial distribution characteristics and temporal variability using CALIPSO, SAGEII, and MERRA-2 data and discussed the possible causes of the variation. The results showed that the ATAL began to appear in the mid-to-late 1990s and then strengthened rapidly until 2010, after which this trend was no longer observed. Moreover, significant heterogeneity existed in the distribution of aerosol concentration in the ATAL, showing north–south differences (NSDs) in both time and space. In addition, it was found that besides surface emissions, atmospheric circulation, the strength of convective transport, and stratosphere–troposphere exchange processes also contribute to this pattern. This study has important implications for quantifying the climate consequences of the ATAL.
Ni/SBA-15 catalysts that are used in ammonia decomposition to produce COx-free hydrogen were prepared by a deposition-precipitation (DP) method and investigated by N2 adsorption/desorption, XRD, TEM ...and H2-TPR techniques. The results show that not only the nano-sized nickel particles with narrow distribution could be obtained, but also the ordered mesostructures of the Ni/SBA-15 catalysts could be achieved during the preparation process. The amount of formed nickel phyllosilicate increases with prolonging the DP time, while surface areas and pore sizes of samples decrease relatively. These Ni/SBA-15 catalysts exhibit higher performance than other Ni-based catalysts and even some supported Ru catalysts. Ammonia conversion is more than 96% at 873K with GHSVNH3 of 46,000ml/hg-cat. Additionally, the Ni/SBA-15 catalyst is very stable during catalytic evaluation operation due to the strong interactions between nickel grains and SBA-15 support.
Pedestrians are vulnerable road users that need proactive protection. While both autonomous and connected vehicle technologies aim to deliver greater safety benefits, current designs heavily rely on ...vehicle-based or on-board sensors and lack strategic real-time interactions with pedestrians who do not have any communication means. As pedestrians are passively protected by the system, they might be put into hazardous situations when vehicle-mounted sensors fail to detect their presence. This paper is part of ongoing research that uses roadside light detection and ranging (LiDAR) sensors to develop a human-in-the-loop system that brings pedestrians into the connected environment. To proactively protect pedestrians, accurate prediction of their intention for crossings at locations, such as unsignalized intersections and street mid-blocks is critical, and this paper presents a modified Naïve Bayes approach for this purpose. It features a probabilistic approach to overcoming the common deficiencies in deterministic methods and provides valuable comparisons between feature-based data processing methods, such as artificial neural network (ANN) and model-based Naïve Bayes approach. A case study was conducted by using a low-cost 16-line LiDAR sensor installed at the roadside. Pedestrians' crossing intention was predicted at a range of 0.5-3 s before actual crossings. The results satisfactorily demonstrated the properties of the modified Naïve Bayes model, as well as its higher flexibility, compared with the ANN approaches in practice.
Isoforms of a gene may contribute to diverse biological functions. In the cochlea, the repertoire of alternative isoforms remains unexplored. We integrated single-cell short-read and long-read RNA ...sequencing techniques and identified 236,012 transcripts, 126,612 of which were unannotated in the GENCODE database. Then we analyzed and verified the unannotated transcripts using RNA-seq, RT-PCR, Sanger sequencing, and MS-based proteomics approaches. To illustrate the importance of identifying spliced isoforms, we investigated otoferlin, a key protein involved in synaptic transmission in inner hair cells (IHCs). Upon deletion of the canonical otoferlin isoform, the identified short isoform is able to support normal hearing thresholds but with reduced sustained exocytosis of IHCs, and further revealed otoferlin functions in endocytic membrane retrieval that was not well-addressed previously. Furthermore, we found that otoferlin isoforms are associated with IHC functions and auditory phenotypes. This work expands our mechanistic understanding of auditory functions at the level of isoform resolution.
α‐Tthalassemia mental retardation X‐linked (ATRX) is a chromatin remodeler frequently mutated in many cancers. Despite the binding pattern of ATRX in heterochromatin, ATRX‐mediated epigenomic changes ...in cancer cells have not been profiled, especially for the heterochromatin regions. Here, we profiled genome‐wide maps of chromatin accessibility in ATRX‐intact and ATRX‐null human cancer cells. We found extensive changes in chromatin accessibility in both repetitive DNA regions and non‐repetitive regulatory regions following ATRX loss. These changes are highly correlated with changes in transcription, which lead to alterations in cancer‐related signalling pathways, such as upregulation of the TGF‐β pathway and downregulation of the cadherin family of proteins. These findings indicate that ATRX deficiency induces epigenomic changes and promotes tumorigenesis through both genome instability and shifts in transcription.
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