Spatial range queries play a crucial role in spatial information retrieval. Existing Z-order curve based algorithms suffer from accessing a large number of invalid points outside the query region. To address this challenge, we design a simple yet efficient Z-order curve based learned index, ZPI. Building upon ZPI, we propose a novel spatial range query algorithm, ZPI-RQ. ZPI-RQ leverages efficient decomposition mechanism to address the invalid points issue. To avoid decomposing the query region into a large number of overly small blocks, a query region expansion strategy is further introduced to align each query border with a m-order dividing lines. Experimental results show that ZPI-RQ significantly outperforms state-of-the-art algorithms in query efficiency, achieving a 3.6× improvement over traditional Z-order curve-based algorithms while accessing only 1% invalid points.

In recent years, single-domain generalization(SDG) fault diagnosis has become a prominent research focus in intelligent fault diagnosis due to its ability to generalize to previously unseen target domains based solely on a single source domain. The primary aim of domain generalization is to identify the intrinsic invariances underlying diverse data distributions, which have been found to be closely related to causality. While most existing fault diagnosis methods based on causal inference emphasize the invariance of causal features across domains, this study considers a stronger form of stability—namely, the cross domain consistency of features’ causal contributions to fault labels. Accordingly, a novel fault diagnosis method is proposed, which integrates Multi-scale Style Enhancement (MSSE) with Causal Contribution Alignment (CCA) to achieve SDG. First, to make up for the lack of data diversity in the source domain, domain shifts are simulated and diverse pseudo-domain samples are generated using a MSSE module. Second, causal contributions of features to diagnostic labels are quantified through causal attribution. Finally, the alignment of causal contributions of features between source and pseudo domains is enforced through contrastive learning and domain adversarial training, thereby promoting stable and cross domain invariant causal representations. Comprehensive experimental evaluations on two benchmark datasets verify that the proposed method consistently outperforms existing fault diagnosis approaches.

This paper introduces HQT-TI, a novel indexing method designed to improve the efficiency of spatial keyword queries. HQT-TI consists of two main components: a Hilbert QuadTree (HQT) based spatial index and a Trie-Inverted index (TI) combined textual index. HQT integrates the Hilbert curve with a Quadtree, establishing a direct relationship between the two. TI combines a trie and inverted index to minimize the intersection cost associated with long lists, thus improving the speed of keyword queries. The HQT based Spatial Query algorithm (HQT-SQ) reduces overlap checks and limits irrelevant object retrieval by employing query drill-down and depth first search with limited breadth expansion in spatial queries. Meanwhile, the Segment List Intersection based Keyword Query algorithm (SLI-KQ), built on TI, efficiently handles segment list intersections for keyword queries. The combination of HQT-SQ and SLI-KQ results in HS-SK, a highly efficient spatial keyword query algorithm. Extensive experimental results demonstrate that HS-SKQ outperforms SFC-Quad by up to two orders of magnitude, achieving up to a 5.46× speedup over the best existing competitors, making it a promising solution for large-scale spatial keyword query processing.

Set Similarity Query (SSQ) is widely applied in various fields. The existing B+-tree-based SSQ approaches fail to fully exploit length filtering and require calculating similarity bounds in a node-wise manner, leading to low efficiency. To address these issues, we propose LeB, a novel length-enhanced B+-tree index, whose keys integrate set lengths and bucket mapping, enabling the direct pruning of sets that do not meet the length requirements. Building upon LeB, we present an efficient algorithm, LeBQ, which leverages length filtering and symmetric difference allocation to determine the key bounds for a query, enabling the key bounds computation only once for each query$Q$and avoiding costly similarity bounds computation in a node-wise manner. Efficient key filtering strategies are proposed to prune sets that cannot be similar, significantly reducing the number of candidates. Based on LeBQ, LeBQ+ further reduces the number of candidates by introducing length-independent key bounds. Experimental results on four real datasets demonstrate that LeBQ+ has a higher node access efficiency and accesses only 3.08% to 27.47% nodes compared to the existing B+-tree-based SSQ algorithm. LeBQ+is up to 99.8 × faster than the state-of-the-art algorithms.

Local Differential Privacy (LDP) has garnered considerable attention in recent years because it does not rely on trusted third parties and has low interactivity and high operational efficiency. However, current LDP frequency estimation mechanisms aggregate data using different privacy budgets within the same domain of attribute values, overlooking the aggregation requirements across different domains of attribute values. This limits the potential for enhancing the data utility under fixed privacy budgets and meeting user preferences in multiple domains of attribute values and privacy budgets. To address this issue, we define a Multi-Domains Personalized Local Differential Privacy (MDPLDP) model that allows users to freely choose domains of attribute values and privacy budgets according to their privacy preferences. Furthermore, based on the MDPLDP model, two new frequency estimation mechanisms are proposed: MDPLDP-Generalized Randomized Response and MDPLDP-basic Randomized Aggregatable Privacy-Preserving Ordinal Response. These mechanisms support cross-domains data aggregation and optimize data utility by adjusting the domains of attribute values and increasing privacy budgets. Theoretical analysis reveals that these new mechanisms have lower estimation errors than the traditional LDP mechanisms. Experiments on real and synthetic datasets demonstrate that the proposed mechanisms effectively reduce estimation errors and enhance the utility of data-frequency estimation.

Abstract Currently, it is a challenging problem to make clustering algorithms suitable for arbitrary distributions of data. In this paper, we propose a Micro-cluster Structure Clustering algorithm based on the Weight-constrained Minimum Spanning Tree, called MSC-WMST. Firstly, the original data is standardized and rescaled, where each feature dimension is partitioned into several intervals by a unit length. Specified regions are separated within these intervals based on a given threshold, and data is sampled in these regions. Secondly, an improved weighted-constrained minimum spanning tree is proposed to search for initial micro-clusters from the sampled data. Thirdly, the merging indicator is jointly defined by the local density of micro-clusters and the distance between micro-clusters, and the pairs of micro-clusters that satisfy the maximum merging indicator will be iteratively merged in a bottom-up hierarchical manner to obtain the final cluster structure. In addition, noisy data can be identified by analyzing the characteristics of the minimum spanning tree. Finally, the remaining samples are assigned to the cluster nearest to them. Extensive experiments were conducted on twenty-four datasets, we compared the MSC-WMST algorithm with the state-of-the-art algorithms. The experimental results demonstrate that MSC-WMST exhibits excellent performance in three evaluation metrics.

Airfare price prediction is one of the core facilities of the decision support system in civil aviation, which includes departure time, days of purchase in advance and flight airline. The traditional airfare price prediction system is limited by the nonlinear interrelationship of multiple factors and fails to deal with the impact of different time steps, resulting in low prediction accuracy. To address these challenges, this paper proposes a novel civil airline fare prediction system with a Multi-Attribute Dual-stage Attention (MADA) mechanism integrating different types of data extracted from the same dimension. In this method, the Seq2Seq model is used to add attention mechanisms to both the encoder and the decoder. The encoder attention mechanism extracts multi-attribute data from time series, which are optimized and filtered by the temporal attention mechanism in the decoder to capture the complex time dependence of the ticket price sequence. Extensive experiments with actual civil aviation data sets were performed, and the results suggested that MADA outperforms airfare prediction models based on the Auto-Regressive Integrated Moving Average (ARIMA), random forest, or deep learning models in MSE, RMSE, and MAE indicators. And from the results of a large amount of experimental data, it is proven that the prediction results of the MADA model proposed in this paper on different routes are at least 2.3% better than the other compared models.

Frequent Itemset Mining (FIM) from large-scale databases has emerged as an important problem in the data mining and knowledge discovery research community. However, FIM suffers from three important limitations with the rapidly expanding of big data in all domains. First, it assumes that all items have the same importance. Second, it ignores the fact that data collected in a real-life environment is often inaccurate. Third, it is also a data-intensive and computation-intensive process which makes the FIM algorithm very time-consuming over large datasets. To address these issues, we propose a Parallel uncertain frequent itemset mining algorithm with spark (Pufim). Pufim firstly expresses item uncertainty by considering both the probability and weight, and calculates the maximum probability weight value of 1-items. Next, a distributed Pufim-tree structure is designed inspiring by FP-Tree for reducing the times of scanning the databases. Each node of Pufim-tree stores an item and its maximum probability weight value. Finally, experiments on publicly available UCI datasets demonstrate that Pufim achieves more prominent results than other related approaches across various metrics. In addition, the empirical study also shows Pufim has a good scalability.

Big data applications store data sets through sharing data center under the Cloud computing environment, but the need of data set in big data applications is dynamic change over time. In face of multiple data centers, such applications meet new challenges in data migration which mainly include how to how to reduce the number of network access, how to reduce the overall time consumption, and how to improve the efficiency by the time of balancing the global load in the migration process. Facing these challenges, we first build the problem model and descript the dynamic migration method, then solve the global time consumption of data migration, the number of network access and global load balancing these three parameters. Finally, do the cloud computing simulation experiment under the Cloudsim experiment platform. The result shows that the proposed method makes the task completion time reduced by 10% and the data transmission time accounts for the roportion of the total time is reduced. When the amount of data sets is increase, the proportion can reduces to 50% or less. Network access number lower than Zipf and reached stable, in global load, the variance of the node's store space closed to zero.