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Trajectory classification focuses on predicting the class or category of a moving object based on its observed movement over time. The classification of trajectory data using classical approaches can be challenging due to the arbitrary and relatively long length of some trajectories. To overcome this, trajectories are often mapped into vector representations that aim to encode their most significant features and for a fixed number of dimensions. Here we propose a novel vector representation for trajectories that combines previously employed features with new ones derived from the computation of the Kramers–Moyal coefficients (KMC). Due to KMC originating from a Taylor expansion that progressively encapsulates more information about a stochastic process, their potential to be effective in trajectory classification is a logical anticipation. We evaluated our representation using different classifiers and several benchmark datasets previously used for trajectory classification. With the addition of features extracted from KMCs, our results indicate a reliable increase in classification accuracy and F1 score of around 4% across all datasets and models used for evaluation. Moreover, we observed an increase in accuracy of up to 20% and an increase in F1 score of up to 23% in some scenarios.

In this paper, a series of novel activation functions is presented, which is derived using the improved Riemann–Liouville conformable fractional derivative (${}^{RL}$CFD). This study investigates the use of fractional activation functions in Multilayer Perceptron (MLP) models and their impact on the performance of classification tasks, verified using the IRIS, MNIST and FMNIST datasets. Fractional activation functions introduce a non-integer power exponent, allowing for improved capturing of complex patterns and representations. The experiment compares MLP models employing fractional activation functions, such as fractional sigmoid, hyperbolic tangent and rectified linear units, against traditional models using standard activation functions, their improved versions and existing fractional functions. The numerical studies have confirmed the theoretical observations mentioned in the paper. The findings highlight the potential usage of new functions as a valuable tool in deep learning in classification. The study suggests incorporating fractional activation functions in MLP architectures can lead to superior accuracy and robustness.

In the real world, the large and complex nature of text increases the difficulty of tagging and results in a limited amount of tagged text. Few-shot Named Entity Recognition(NER) only uses a small amount of annotation data to identify and classify entities. It avoids the above problems. Few-shot learning methods usually use prior knowledge to achieve good results. However, prior knowledge may become a confounding factor affecting the relation between sample features and real labels. This problem leads to bias and difficulty accurately capturing class. To solve this problem, a new model, Few-shot Named Entity Recognition via Encoder and Class Intervention, is proposed based on causality. We show that we can steer the model to manufacture interventions on encoder and class, and reduce the interference of confounding factors. Specifically, while cross-sample attention perturbation is used in the encoder layer, a practical causal relation between feature and classification label is developed in the class layer. This way is an attempt of causal methodology in the Few-shot Named Entity Recognition task, which improves the discrimination ability of the NER classifier. Experimental results demonstrate that our model outperforms baseline models in both 5-way and 10-way on two NER datasets.

Vision-Language Pre-training (VLP) models have shown promising capabilities in grounding natural language in image data, facilitating a broad range of cross-modal tasks. However, we note that there exists a significant gap between the objective forms of model pre-training and fine-tuning, resulting in a need for large amounts of labeled data to stimulate the visual grounding capability of VLP models for downstream tasks. To address the challenge, we present Color-based Prompt Tuning (CPT), a novel paradigm for tuning VLP models, which reformulates visual grounding into a fill-in-the-blank problem with color-based co-referential markers in image and text, maximally mitigating the gap. In this way, CPT enables strong few-shot and even zero-shot visual grounding capabilities of VLP models. Comprehensive experimental results show that CPT achieves state-of-the-art performance on zero/few-shot visual grounding (e.g., 75.1 zero-shot accuracy in RefCOCO evaluation), outperforming fine-tuned and other prompt-tuned models by a large margin. Moreover, CPT can also be easily extended to achieve promising zero/few-shot performance on other vision-language tasks, such as visual relation detection, visual commonsense reasoning and visual question answering. We make the data and codes publicly available at https://github.com/thunlp/CPT.

This paper presents an ecosystem for personal knowledge graphs (PKGs), commonly defined as resources of structured information about entities related to an individual, their attributes, and the relations between them. PKGs are a key enabler of secure and sophisticated personal data management and personalized services. However, there are challenges that need to be addressed before PKGs can achieve widespread adoption. One of the fundamental challenges is the very definition of what constitutes a PKG, as there are multiple interpretations of the term. We propose our own definition of a PKG, emphasizing the aspects of (1) data ownership by a single individual and (2) the delivery of personalized services as the primary purpose. We further argue that a holistic view of PKGs is needed to unlock their full potential, and propose a unified framework for PKGs, where the PKG is a part of a larger ecosystem with clear interfaces towards data services and data sources. A comprehensive survey and synthesis of existing work is conducted, with a mapping of the surveyed work into the proposed unified ecosystem. Finally, we identify open challenges and research opportunities for the ecosystem as a whole, as well as for the specific aspects of PKGs, which include population, representation and management, and utilization.

Authorship style transfer aims to modify the style of neutral text to match the unique speaking or writing style of a particular individual. While Large Language Models (LLMs) present promising solutions, their effectiveness is limited by the small number of in-context learning demonstrations, particularly for authorship styles not frequently seen during pre-training. In response, this paper proposes an inverse transfer data augmentation (ITDA) method, leveraging LLMs to create (neutral text, stylized text) pairs. This method involves removing the existing styles from stylized texts, a process made more feasible due to the prevalence of neutral texts in pre-training. We use this augmented dataset to train a compact model that is efficient for deployment and adept at replicating the targeted style. Our experimental results, conducted across four datasets with distinct authorship styles, establish the effectiveness of ITDA over traditional style transfer methods and forward transfer using GPT-3.5. For further research and application, our dataset and code are openly accessible at https://github.com/Vicky-Shao/ITDA.

Deep reinforcement learning (DRL) has been shown to have numerous potential applications in the real world. However, DRL algorithms are still extremely sensitive to noise and adversarial perturbations, hence inhibiting the deployment of RL in many real-life applications. Analyzing the robustness of DRL algorithms to adversarial attacks is an important prerequisite to enabling the widespread adoption of DRL algorithms. Common perturbations on DRL frameworks during test time include perturbations to the observation and the action channel. Compared with observation channel attacks, action channel attacks are less studied; hence, few comparisons exist that compare the effectiveness of these attacks in DRL literature. In this work, we examined the effectiveness of these two paradigms of attacks on common DRL algorithms and studied the natural robustness of DRL algorithms towards various adversarial attacks in hopes of gaining insights into the individual response of each type of algorithm under different attack conditions.