Spatio-temporal estimation plays a vital role in numerous scientific and engineering tasks, particularly for novel or unobserved locations lacking historical references. Many areas remain unobserved by sensors due to their non-core location or pending development status. The states of these areas can only be estimated through similar nodes in the geospace, rather than through historical data with temporal trends. Estimating these unobserved node states is crucial for city-wide spatio-temporal sensing and urban development, extending beyond simple point or block data imputation. In this study, we introduce a diffusion point process in high-frequency space to develop a robust spatio-temporal diffusion transformer for urban estimation where partial historical reference data is lacking. Our approach decomposes spatio-temporal data into high and low-frequency components through wavelet transform, and trains a diffusion model of spatial temporal data with a transformer that operates on high frequency signals. We incorporate low-frequency signals as diffusion conditions in the transformer architecture to capture overall spatio-temporal profiles and gradual trends. To enhance the learning of each step, we design an diffusion model featuring a spatio-temporal attention module that adaptively captures interdependencies between time and space. Extensive experiments across diverse domains including traffic, economics, and environment demonstrate that our method significantly outperforms state-of-the-art baselines.

Address parsing is an essential task that transforms natural language descriptions into standardized addresses, crucial for numerous urban applications. Existing methods struggle with ambiguous expressions, and even Large Language Models face challenges adapting to specialized domains with limited data. In this study, we focus on developing a robust framework to map diverse address descriptions into a unified semantic space of standardized addresses. We propose the Adaptive Weighted Learning-based Address Parsing (AWLAP) framework, which enhances parsing effectiveness through two key components: a multi-level constrained classifier that mines correlations between geographic entities across hierarchies, and an integrated discriminator that adaptively guides optimization based on parsing complexity. We evaluate the AWLAP using real data from JD Logistics and Point-of-Interest addresses. Extensive experiments comparing against state-of-the-art methods demonstrate AWLAP's effectiveness and robustness in address parsing. The proposed AWLAP framework has been successfully deployed as an address parsing service in practical applications.

Semi-supervised learning holds great promise for many real-world applications, due to its ability to leverage both unlabeled and expensive labeled data. However, most semi-supervised learning algorithms still heavily rely on the limited labeled data to infer and utilize the hidden information from unlabeled data. We note that any semi-supervised learning task under the self-training paradigm also hides an auxiliary task of discriminating label observability. Jointly solving these two tasks allows full utilization of information from both labeled and unlabeled data, thus alleviating the problem of over-reliance on labeled data. This naturally leads to a new generic and efficient learning framework without the reliance on any domain-specific information, which we call FlexSSL. The key idea of FlexSSL is to construct a semi-cooperative “game”, which forges cooperation between a main self-interested semi-supervised learning task and a companion task that infers label observability to facilitate main task training. We show with theoretical derivation of its connection to loss re-weighting on noisy labels. Through evaluations on a diverse range of tasks, we demonstrate that FlexSSL can consistently enhance the performance of semi-supervised learning algorithms.

Person re-identification (Re-ID) is a fundamental task in visual surveillance. Given a query image of the target person, conventional Re-ID focuses on the pairwise similarities between the candidate images and the query. However, conventional Re-ID does not evaluate the consistency of the retrieval results of whether the most similar images ranked in each place contain the same person, which is risky in some applications such as missing out a place where the patient passed will hinder the epidemiological investigation. In this work, we investigate a more challenging task: consistently and successfully retrieving the target person in all camera views. We define the task as continuous person Re-ID and propose a corresponding evaluation metric termed overall Rank-K accuracy. Different from the conventional Re-ID, any incorrect retrieval under an individual camera view that raises an inconsistency will fail the continuous Re-ID. Consequently, the defective cameras, in which the images are hard to be automatically associated with the images from other views, strongly degrade the performance of continuous person Re-ID. Since the camera deployment is crucial for continuous tracking across camera views, we rethink person Re-ID from the perspective of camera deployment and assess the quality of a camera network by performing continuous Re-ID. Moreover, we propose to automatically detect the defective cameras that greatly hamper the continuous Re-ID. Because brute-force search is costly when the camera network becomes complicated, we explicitly model the visual relations as well as the spatial relations among cameras and develop a relational deep Q-network to select the properly deployed cameras and the un-selected cameras are regarded as the defective cameras. Since most existing datasets do not provide topology information about the camera network, they are unsuitable for investigating the importance of spatial relations on camera selection. Thus, we collect a new dataset including 20 cameras with topology information. Compared with randomly removing cameras, the experimental results show that our method can effectively detect the defective cameras so that people could take further operations on these cameras in practice (https://www.isee-ai.cn/∼yixing/MCCPD.html).

In this work, we consider the cross-scene person trajectory anomaly detection problem, which detects the anomalous trajectories across multiple nonoverlapping scenes. This problem is highly significant for public security, but it is still underexplored. Since the trajectory is not continuous across nonoverlapping camera views, we take use of person reidentification (re-ID) to associate the same pedestrian in different scenes while mitigating its inaccuracy by a directional probabilistic graph. To better distinguishing normal samples from anomalies, We formulate a maximized margin graph autoencoder (MMGAE) model, and the reconstruction error of the MMGAE is regarded as an anomaly indicator for the sample. To verify the effectiveness of our approach, we collected and labeled a new dataset. we also explore the impact of the re-ID performance on the anomaly detection problem and the effect of an inaccurately constructed graph on the MMGAE.

Accurate network-wide traffic state estimation is vital to many transportation operations and urban applications. However, existing methods often suffer from the scalability issue when performing real-time inference at the city-level, or not robust enough under limited data. Currently, GPS trajectory data from probe vehicles has become a popular data source for many transportation applications. GPS trajectory data has large coverage area, which is ideal for network-wide applications, but also has the disadvantage of being sparse and highly heterogeneous among different time and locations. In this study, we focus on developing a robust and interpretable network-wide traffic state imputation framework using partially observed traffic information. We introduce a new learning strategy, called self-interested coalitional learning (SCL), which forges cooperation between a main self-interested semi-supervised learning task and a discriminator as a critic to facilitate main task training while providing interpretability on the results. In our detailed model, we use a temporal graph convolutional variational autoencoder (TG-VAE) as the reconstructor, which models the complex spatio-temporal pattern in data and solves the main traffic state imputation task. A discriminator is introduced to output interpretable imputation confidence on the estimated results and also help to enhance the performance of the reconstructor. The framework is evaluated using a large GPS trajectory dataset from taxis in Jinan, China. Extensive experiments against the state-of-the-art baselines demonstrate the effectiveness and robustness of the proposed method for network-wide traffic state estimation.

In this work, we study the person search problem, which incorporates both person detection and person re-identification. The high time consumption of person search system obstructs the development of this field in practice. For the purpose of real-time person search, we analyze the bottleneck of the person search task and therefore develop a more efficient method called the Fast Person Search Pipeline (FPSP), consisting of a multi-scale person detector as well as a part-based person re-identification descriptor. Extensive experiments show that our proposed method FPSP can accomplish the person search task approximately FIVE times faster than the state-of-the-art methods while achieving a competitive accuracy.

The increasing use of smartphones as personal computing platforms to access personal information has stressed the demand for secure and usable authentication techniques, and for constantly protecting privacy. Smartphone sensors can measure users' unique behavioral characteristics when they interact with smartphones, based on different habits, gestures, and angle preferences of touch actions. This paper investigates the reliability and applicability of using motion-sensor behavior for active and continuous smartphone authentication across various operational scenarios, and presents a systematic evaluation of the distinctiveness and permanence properties of the behavior. For each sample of sensor behavior, kinematic information sequences are extracted and analyzed, which are characterized by statistic-, frequency-, and wavelet-domain features, to provide accurate and fine-grained characterization of users' touch actions. A Markov-based decision procedure, using one-class learning techniques, is developed and applied to the feature space for performing authentication. Analyses are conducted using the sensor data of 520 200 touch actions from 102 subjects across various operational scenarios. Extensive experiments show that motion-sensor behavior exhibits sufficient discriminability and stability for active and continuous authentication, and can achieve a false-rejection rate of 5.03% and a false-acceptance rate of 3.98%. Additional experiments on usability to operation length, sensitivity to application scenario, scalability to user size, contribution to different sensors, and response to behavior change are provided to further explore the effectiveness and applicability. We also implement an authentication system into the Android system that can react to the presence of the legitimate user.