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Browsing by Author "Chen, Fanglan"

Now showing 1 - 6 of 6
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    Adaptive graph convolutional imputation network for environmental sensor data recovery
    Chen, Fanglan; Wang, Dongjie; Lei, Shuo; He, Jianfeng; Fu, Yanjie; Lu, Chang-Tien (Frontiers, 2022-11)
    Environmental sensors are essential for tracking weather conditions and changing trends, thus preventing adverse effects on species and environment. Missing values are inevitable in sensor recordings due to equipment malfunctions and measurement errors. Recent representation learning methods attempt to reconstruct missing values by capturing the temporal dependencies of sensor signals as handling time series data. However, existing approaches fall short of simultaneously capturing spatio-temporal dependencies in the network and fail to explicitly model sensor relations in a data-driven manner. In this work, we propose a novel Adaptive Graph Convolutional Imputation Network for missing value imputation in environmental sensor networks. A bidirectional graph convolutional gated recurrent unit module is introduced to extract spatio-temporal features which takes full advantage of the available observations from the target sensor and its neighboring sensors to recover the missing values. In addition, we design an adaptive graph learning layer that learns a sensor network topology in an end-to-end framework, in which no prior network information is needed for capturing spatial dependencies. Extensive experiments on three real-world environmental sensor datasets (solar radiation, air quality, relative humidity) in both in-sample and out-of-sample settings demonstrate the superior performance of the proposed framework for completing missing values in the environmental sensor network, which could potentially support environmental monitoring and assessment.
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    Automated Urban Planning for Reimagining City Configuration via Adversarial Learning: Quantification, Generation, and Evaluation
    Wang, Dongjie; Fu, Yanjie; Liu, Kunpeng; Chen, Fanglan; Wang, Pengyang; Lu, Chang-Tien (ACM, 2022)
    Urban planning refers to the efforts of designing land-use configurations given a region. However, there is a time-consuming and labor-intensive process for designing effective configurations, which motivates us to ask: can AI accelerate the urban planning process, so that human planners only adjust generated configurations for specific needs? The recent advance of deep generative models inspires us to automate urban planning from an adversarial learning perspective. However, three major challenges arise: 1) how to define a quantitative land-use configuration? 2) how to automate configuration planning? 3) how to evaluate the quality of a generated configuration? In this paper, we systematically address the three challenges. Specifically, 1) We define a land-use configuration as a longitude-latitude-channel tensor. 2) We formulate the automated urban planning problem into a task of deep generative learning. The objective is to generate a configuration tensor given the surrounding contexts of a target region. In particular, we first construct spatial graphs using geographic and human mobility data to learn graph representations. We then combine each target area and its surrounding context representations as a tuple, and categorize all tuples into positive (well-planned areas) and negative samples (poorly-planned areas). Next, we develop an adversarial learning framework, in which a generator takes the surrounding context representations as input to generate a land-use configuration, and a discriminator learns to distinguish between positive and negative samples. 3) We provide quantitative evaluation metrics and conduct extensive experiments to demonstrate the effectiveness of our framework.
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    Bridging the Gap between Spatial and Spectral Domains: A Unified Framework for Graph Neural Networks
    Chen, Zhiqian; Chen, Fanglan; Zhang, Lei; Ji, Taoran; Fu, Kaiqun; Zhao, Liang; Chen, Feng; Wu, Lingfei; Aggarwal, Charu; Lu, Chang-Tien (ACM, 2023-10)
    Deep learning's performance has been extensively recognized recently. Graph neural networks (GNNs) are designed to deal with graph-structural data that classical deep learning does not easily manage. Since most GNNs were created using distinct theories, direct comparisons are impossible. Prior research has primarily concentrated on categorizing existing models, with little attention paid to their intrinsic connections. The purpose of this study is to establish a unified framework that integrates GNNs based on spectral graph and approximation theory. The framework incorporates a strong integration between spatial- and spectral-based GNNs while tightly associating approaches that exist within each respective domain.
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    CLUR: Uncertainty Estimation for Few-Shot Text Classification with Contrastive Learning
    He, Jianfeng; Zhang, Xuchao; Lei, Shuo; Alhamadani, Abdulaziz; Chen, Fanglan; Xiao, Bei; Lu, Chang-Tien (ACM, 2023-08-06)
    Few-shot text classification has extensive application where the sample collection is expensive or complicated. When the penalty for classification errors is high, such as early threat event detection with scarce data, we expect to know “whether we should trust the classification results or reexamine them.” This paper investigates the Uncertainty Estimation for Few-shot Text Classification (UEFTC), an unexplored research area. Given limited samples, a UEFTC model predicts an uncertainty score for a classification result, which is the likelihood that the classification result is false. However, many traditional uncertainty estimation models in text classification are unsuitable for implementing a UEFTC model. These models require numerous training samples, whereas the few-shot setting in UEFTC only provides a few or just one support sample for each class in an episode. We propose Contrastive Learning from Uncertainty Relations (CLUR) to address UEFTC. CLUR can be trained with only one support sample for each class with the help of pseudo uncertainty scores. Unlike previous works that manually set the pseudo uncertainty scores, CLUR self-adaptively learns them using our proposed uncertainty relations. Specifically, we explore four model structures in CLUR to investigate the performance of three common-used contrastive learning components in UEFTC and find that two of the components are effective. Experiment results prove that CLUR outperforms six baselines on four datasets, including an improvement of 4.52% AUPR on an RCV1 dataset in a 5-way 1-shot setting. Our code and data split for UEFTC are in https: //github.com/he159ok/CLUR_UncertaintyEst_FewShot_TextCls.
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    Detecting anomalous traffic behaviors with seasonal deep Kalman filter graph convolutional neural networks
    Sun, Yanshen; Lu, Yen-Cheng; Fu, Kaiqun; Chen, Fanglan; Lu, Chang-Tien (Elsevier, 2022-09)
    Anomaly detection over traffic data is crucial for transportation management and abnormal behavior identification. An anomaly in real-world scenarios usually causes abnormal observations for multiple detectors in an extended period. However, existing anomaly detection methods overly leverage the single or isolated feature interdependent contextual information in anomalies, inevitably dropping the detec-tion performance. In this paper, we propose S-DKFN (Seasonal Deep Kalman Filter Network), to identify abnormal patterns with a long duration and wide coverage. S-DKFN models traffic data with a graph and simultaneously investigates the spatial and temporal features to hunt abnormal behaviors. Specifically, a dilation temporal convolutional network (TCN) is used to merge the multi-granular seasonal features and a graph convolution network (GCN) to extract spatial features. The outputs of TCN and GCN are then fed to long-short term models (LSTM) and merged by Kalman filters for denoising. An encoder-decoder mod-ule is introduced to predict traffic attributes with seasonal features. The mean squared errors (MSE) of the predictions are considered the anomaly scores. Experimental results on two real-world datasets show that our proposed S-DKFN framework outperforms the state-of-the-art baseline methods in detecting anomalies with long-duration and wide-coverage, especially its ability to detect accidents.(c) 2022 The Authors. Published by Elsevier B.V. on behalf of King Saud University. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
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    Memetic algorithms for Spatial Partitioning problems
    Biswas, Subhodip; Chen, Fanglan; Chen, Zhiqian; Lu, Chang-Tien; Ramakrishnan, Naren (ACM)
    Spatial optimization problems (SOPs) are characterized by spatial relationships governing the decision variables, objectives, and/or constraint functions. In this article, we focus on a specific type of SOP called spatial partitioning, which is a combinatorial problem due to the presence of discrete spatial units. Exact optimization methods do not scale with the size of the problem, especially within practicable time limits. This motivated us to develop population-based metaheuristics for solving such SOPs. However, the search operators employed by these population-based methods are mostly designed for real-parameter continuous optimization problems. For adapting these methods to SOPs, we apply domain knowledge in designing spatially-aware search operators for efficiently searching through the discrete search space while preserving the spatial constraints. To this end, we put forward a simple yet effective algorithm called SPATIAL and test it on the school (re)districting problem. Detailed experimental investigations are performed on real-world datasets to evaluate the performance of SPATIAL. Besides, ablation studies are performed to understand the role of the individual components of SPATIAL. Additionally, we discuss how SPATIAL is helpful in the real-life planning process, its applicability to different scenarios, and motivate future research directions.