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Xiaolei Ma

Bio: Xiaolei Ma is an academic researcher from Beihang University. The author has contributed to research in topics: Artificial neural network & Deep learning. The author has an hindex of 29, co-authored 83 publications receiving 5977 citations. Previous affiliations of Xiaolei Ma include Chinese Ministry of Public Security & University of Washington.

Papers published on a yearly basis

Papers
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Journal ArticleDOI
TL;DR: A modified nonnegative matrix factorization algorithm is proposed that processes high-dimensional traffic data and provides an improved representation of the global traffic state and exhibit considerable potential for identifying and interpreting the spatiotemporal traffic patterns over the entire network and provide a systematic and efficient approach for analyzing the network-level traffic state.
Abstract: The identification and analysis of spatiotemporal traffic patterns in road networks constitute a crucial process for sophisticated traffic management and control. Traditional methods based on mathematical equations and statistical models can hardly be applicable to large-scale urban road networks, where traffic states exhibit high degrees of dynamics and complexity. Recently, advances in data collection and processing have provided new opportunities to effectively understand spatiotemporal traffic patterns in large-scale road networks using data-driven methods. However, limited efforts have been exerted to explore the essential structure of the networks when conducting a spatiotemporal analysis of traffic characteristics. To this end, this study proposes a modified nonnegative matrix factorization algorithm that processes high-dimensional traffic data and provides an improved representation of the global traffic state. After matrix factorization, cluster analysis is conducted based on the obtained low-dimensional representative matrices, which contain different traffic patterns and serve as the basis for exploring the temporal dynamics and spatial structure of network congestion. The applicability and effectiveness of the proposed approach are examined in a road network of Beijing, China. Results show that the methods exhibit considerable potential for identifying and interpreting the spatiotemporal traffic patterns over the entire network and provide a systematic and efficient approach for analyzing the network-level traffic state.

6 citations

01 Jan 2010
TL;DR: The researchers concluded that spot speed data can indicate free flow conditions, but sufficient quantities of data are probably necessary to measure congested travel.
Abstract: Global positioning systems (GPS) used for fleet management by trucking companies provide probe data that can support a truck performance-monitoring program. This paper discusses the steps taken to acquire fleet management data and then process those data so they can eventually be used for a network-based truck performance measures program. While other studies have evaluated truck travel by using GPS, they have used a limited number of project-specific and temporary devices that have collected frequent location reads, permitting a fine-grained performance analysis of specific roadway segments. In contrast, this fleet management GPS data project involved infrequent reads but a relatively large number of different trucks with ongoing data collection. The most effective approach to obtaining the fleet management data was to purchase the data directly from GPS vendors. Because a performance measures program ultimately monitors trips generated by trucks as they travel between origins and destinations, an algorithm was developed to extract trip end information from the data. The large volume of data required automated processing without manual intervention. Because performance measures require travel times and speeds, it was also necessary to evaluate whether speed data from a large number of trucks could compensate for infrequent location reads. Spot speeds recorded by the trucks’ GPS devices were compared to speed data from roadway loops. The researchers concluded that spot speed data can indicate free flow conditions, but sufficient quantities of data are probably necessary to measure congested travel.

5 citations

Posted Content
TL;DR: Wang et al. as mentioned in this paper proposed a new capsule network to extract the spatial features of traffic networks and utilize a nested LSTM (NLSTM) structure to capture the hierarchical temporal dependencies in traffic sequence data.
Abstract: Accurate and reliable traffic forecasting for complicated transportation networks is of vital importance to modern transportation management. The complicated spatial dependencies of roadway links and the dynamic temporal patterns of traffic states make it particularly challenging. To address these challenges, we propose a new capsule network (CapsNet) to extract the spatial features of traffic networks and utilize a nested LSTM (NLSTM) structure to capture the hierarchical temporal dependencies in traffic sequence data. A framework for network-level traffic forecasting is also proposed by sequentially connecting CapsNet and NLSTM. On the basis of literature review, our study is the first to adopt CapsNet and NLSTM in the field of traffic forecasting. An experiment on a Beijing transportation network with 278 links shows that the proposed framework with the capability of capturing complicated spatiotemporal traffic patterns outperforms multiple state-of-the-art traffic forecasting baseline models. The superiority and feasibility of CapsNet and NLSTM are also demonstrated, respectively, by visualizing and quantitatively evaluating the experimental results.

5 citations

Journal ArticleDOI
TL;DR: Wang et al. as discussed by the authors developed an enhanced spatial vector autoregressive (SpVAR) model to investigate relations in public transport systems in the case of sudden large passenger flow impact.
Abstract: Changes in local transit passenger flow may cause a spatial spillover effect across the involved regions and affect traffic patterns in other regions. To identify the affected areas and the traffic patterns, this study develops an enhanced spatial vector autoregressive (SpVAR) model to investigate relations in public transport systems in the case of sudden large passenger flow impact. The proposed model captures the interacted correlation within different transit models in separated regions. Three representative commuting regions in Beijing, namely, Zhongguancun, Guomao, and Huilongguan, are employed for empirical study. Results confirm the existence of spatial spillover effect in the commuter regions and reveal heterogeneous effects of multimodal transit system on regions with different distances.

5 citations

Journal ArticleDOI
Chen Xi, Yinhai Wang1, Jinjun Tang, Zhuang Dai, Xiaolei Ma 
TL;DR: This study proposes a comprehensive methodology framework to uncover regional travel patterns and regularities and shows how this framework can support several applications that are beneficial for urban transportation planning.
Abstract: Understanding human travel patterns with relation to land uses and other land characteristics is a crucial topic in urban studies and offers guidance to better design, plan and manage diverse transportation systems and infrastructures. However, previous studies on such patterns still have some limitations. First, current studies mainly focus on mobility pattern analysis on stop and route levels. Rare studies have investigated user mobility on region levels to exhibit a macroscopic perspective on human activities. Second, the works usually examine one specific transportation mode and fail to compare regional mobility among multiple modes. This study proposes a comprehensive methodology framework to uncover regional travel patterns and regularities. Regional travel patterns are analysed using the non-negative matrix factorisation method. The travel regularity is examined using the Lempel–Ziv algorithm. A case study of Chengdu, China, is conducted to validate the proposed framework. Results can support several applications that are beneficial for urban transportation planning.

5 citations


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Journal ArticleDOI
TL;DR: A comparison with different topologies of dynamic neural networks as well as other prevailing parametric and nonparametric algorithms suggests that LSTM NN can achieve the best prediction performance in terms of both accuracy and stability.
Abstract: Neural networks have been extensively applied to short-term traffic prediction in the past years. This study proposes a novel architecture of neural networks, Long Short-Term Neural Network (LSTM NN), to capture nonlinear traffic dynamic in an effective manner. The LSTM NN can overcome the issue of back-propagated error decay through memory blocks, and thus exhibits the superior capability for time series prediction with long temporal dependency. In addition, the LSTM NN can automatically determine the optimal time lags. To validate the effectiveness of LSTM NN, travel speed data from traffic microwave detectors in Beijing are used for model training and testing. A comparison with different topologies of dynamic neural networks as well as other prevailing parametric and nonparametric algorithms suggests that LSTM NN can achieve the best prediction performance in terms of both accuracy and stability.

1,521 citations

Journal ArticleDOI
Zheng Zhao1, Weihai Chen1, Xingming Wu1, Peter C. Y. Chen, Jingmeng Liu1 
TL;DR: A novel traffic forecast model based on long short-term memory (LSTM) network is proposed, which considers temporal-spatial correlation in traffic system via a two-dimensional network which is composed of many memory units.
Abstract: Short-term traffic forecast is one of the essential issues in intelligent transportation system. Accurate forecast result enables commuters make appropriate travel modes, travel routes, and departure time, which is meaningful in traffic management. To promote the forecast accuracy, a feasible way is to develop a more effective approach for traffic data analysis. The availability of abundant traffic data and computation power emerge in recent years, which motivates us to improve the accuracy of short-term traffic forecast via deep learning approaches. A novel traffic forecast model based on long short-term memory (LSTM) network is proposed. Different from conventional forecast models, the proposed LSTM network considers temporal-spatial correlation in traffic system via a two-dimensional network which is composed of many memory units. A comparison with other representative forecast models validates that the proposed LSTM network can achieve a better performance.

1,204 citations

Journal ArticleDOI
TL;DR: In this article, a novel neural network-based traffic forecasting method, the temporal graph convolutional network (T-GCN) model, which is combined with the graph convolutionsal network and the gated recurrent unit (GRU), is proposed.
Abstract: Accurate and real-time traffic forecasting plays an important role in the intelligent traffic system and is of great significance for urban traffic planning, traffic management, and traffic control. However, traffic forecasting has always been considered an “open” scientific issue, owing to the constraints of urban road network topological structure and the law of dynamic change with time. To capture the spatial and temporal dependences simultaneously, we propose a novel neural network-based traffic forecasting method, the temporal graph convolutional network (T-GCN) model, which is combined with the graph convolutional network (GCN) and the gated recurrent unit (GRU). Specifically, the GCN is used to learn complex topological structures for capturing spatial dependence and the gated recurrent unit is used to learn dynamic changes of traffic data for capturing temporal dependence. Then, the T-GCN model is employed to traffic forecasting based on the urban road network. Experiments demonstrate that our T-GCN model can obtain the spatio-temporal correlation from traffic data and the predictions outperform state-of-art baselines on real-world traffic datasets. Our tensorflow implementation of the T-GCN is available at https://www.github.com/lehaifeng/T-GCN .

1,188 citations

Journal ArticleDOI
TL;DR: In this article, the authors provide a thorough overview on using a class of advanced machine learning techniques, namely deep learning (DL), to facilitate the analytics and learning in the IoT domain.
Abstract: In the era of the Internet of Things (IoT), an enormous amount of sensing devices collect and/or generate various sensory data over time for a wide range of fields and applications. Based on the nature of the application, these devices will result in big or fast/real-time data streams. Applying analytics over such data streams to discover new information, predict future insights, and make control decisions is a crucial process that makes IoT a worthy paradigm for businesses and a quality-of-life improving technology. In this paper, we provide a thorough overview on using a class of advanced machine learning techniques, namely deep learning (DL), to facilitate the analytics and learning in the IoT domain. We start by articulating IoT data characteristics and identifying two major treatments for IoT data from a machine learning perspective, namely IoT big data analytics and IoT streaming data analytics. We also discuss why DL is a promising approach to achieve the desired analytics in these types of data and applications. The potential of using emerging DL techniques for IoT data analytics are then discussed, and its promises and challenges are introduced. We present a comprehensive background on different DL architectures and algorithms. We also analyze and summarize major reported research attempts that leveraged DL in the IoT domain. The smart IoT devices that have incorporated DL in their intelligence background are also discussed. DL implementation approaches on the fog and cloud centers in support of IoT applications are also surveyed. Finally, we shed light on some challenges and potential directions for future research. At the end of each section, we highlight the lessons learned based on our experiments and review of the recent literature.

903 citations