With the research directions described in this thesis, we seek to address the critical challenges in designing recommender systems that can understand the dynamics of continuous-time event sequences. We follow a ground-up approach, i.e., first, we address the problems that may arise due to the poor quality of CTES data being fed into a recommender system. Later, we handle the task of designing accurate recommender systems. To improve the quality of the CTES data, we address a fundamental problem of overcoming missing events in temporal sequences. Moreover, to provide accurate sequence modeling frameworks, we design solutions for points-of-interest recommendation, i.e., models that can handle spatial mobility data of users to various POI check-ins and recommend candidate locations for the next check-in. Lastly, we highlight that the capabilities of the proposed models can have applications beyond recommender systems, and we extend their abilities to design solutions for large-scale CTES retrieval and human activity prediction. A significant part of this thesis uses the idea of modeling the underlying distribution of CTES via neural marked temporal point processes (MTPP). Traditional MTPP models are stochastic processes that utilize a fixed formulation to capture the generative mechanism of a sequence of discrete events localized in continuous time. In contrast, neural MTPP combine the underlying ideas from the point process literature with modern deep learning architectures. The ability of deep-learning models as accurate function approximators has led to a significant gain in the predictive prowess of neural MTPP models. In this thesis, we utilize and present several neural network-based enhancements for the current MTPP frameworks for the aforementioned real-world applications.

当前的利益点方法（POI）建议通过标准空间特征（例如POI坐标，社交网络等）来了解用户的偏好。这些模型忽略了空间移动性的关键方面 - 每个用户都承载他们的偏好无论他们走到哪里，智能手机。此外，随着隐私问题的越来越多，用户避免分享其确切的地理坐标及其社交媒体活动。在本文中，我们提出了Revamp，这是一种顺序POI推荐方法，该方法利用智能手机应用程序（或应用程序）上的用户活动来识别其移动性偏好。这项工作与最近对在线城市用户的心理学研究保持一致，这表明其空间行动行为在很大程度上受其智能手机应用程序的活动影响。此外，我们对粗粒智能手机数据的建议是指以隐私意识的方式收集的数据日志，即仅由（a）类别的智能手机应用程序和（b）类别的签到位置组成。因此，改装并不愿意精确地坐标，社交网络或要访问的特定应用程序。在自我注意模型的疗效的推动下，我们使用两种形式的位置编码（绝对和相对）学习了用户的POI偏好，每种位置编码是从A的签入动力学中提取的，在A的入住序列中提取用户。来自中国的两个大规模数据集进行的广泛实验表明，改革的预测能力及其预测应用程序和POI类别的能力。

通过人类活动（例如在线购买，健康记录，空间流动性等）生成的大量数据可以在连续时间内表示为一系列事件。在这些连续的时间事件序列上学习深度学习模型是一项非平凡的任务，因为它涉及建模不断增加的事件时间戳，活动间时间差距，事件类型以及不同序列内部和跨不同序列之间的不同事件之间的影响。近年来，对标记的时间点过程（MTPP）的神经增强功能已成为一种强大的框架，以模拟连续时间内定位的异步事件的基本生成机制。但是，MTPP框架中的大多数现有模型和推理方法仅考虑完整的观察方案，即所建模的事件序列是完全观察到的，没有丢失的事件 - 理想的设置很少适用于现实世界应用程序。最近考虑的事件的最新工作是在培训MTPP时采用监督的学习技术，这些技术需要以序列的方式了解每个事件的丢失或观察标签，这进一步限制了其实用性，因为在几种情况下，缺失事件的细节是不知道的apriori 。在这项工作中，我们提供了一种新颖的无监督模型和推理方法，用于在存在事件序列的情况下学习MTPP。具体而言，我们首先使用两个MTPP模拟观察到的事件和缺失事件的生成过程，其中缺少事件表示为潜在的随机变量。然后，我们设计了一种无监督的训练方法，该方法通过变异推断共同学习MTPP。这样的公式可以有效地将丢失的数据归为观察到的事件，并可以在序列中确定缺失事件的最佳位置。

在手术视频中自动识别外科手术阶段是手术工作流程分析中的一项基本任务。在本报告中，我们提出了一种基于变压器的方法，该方法利用了2阶段推理管道的校准置信度得分，该方法根据校准的置信度水平动态切换基线模型和单独训练的过渡模型。我们的方法的表现优于Cholec80数据集上的基线模型，并且可以应用于各种动作分割方法。

任何人类活动都可以表示为实现某个目标的行动的时间顺序。与机器制造的时间序列不同，这些动作序列是高度分散的，因为在不同的人之间完成类似动作的时间可能会有所不同。因此，了解这些序列的动力学对于许多下游任务，例如活动长度预测，目标预测等都是必不可少的。对活动序列建模的现有神经方法要么仅限于视觉数据，要么是特定于任务的神经方法，即仅限于下一个动作或目标预测。在本文中，我们提出了积极主动的，是一个神经标记的时间点过程（MTPP）框架，用于建模活动序列中的动作连续时间分布，同时解决三个高影响力问题 - 下一步动作预测，序列 - 目标预测，序列预测，和端到端序列生成。具体而言，我们利用具有时间归一化流量的自我发项模块来模拟序列中的动作之间的影响和到达时间间的时间。此外，对于时间敏感的预测，我们通过基于边缘的优化程序进行了序列目标的早期检测。这种往返允许积极主动使用有限数量的动作来预测序列目标。从三个活动识别数据集得出的序列进行的广泛实验表明，在动作和目标预测方面，主动的准确性提升了，并且是有史以来第一次应用端到端动作序列生成的实验。

人类活动产生的大量数据如在线购物，健康记录，空间移动性等。在连续时间内被存储为一系列事件。在这些序列中学习深度学习方法是一种非琐碎的任务，因为它涉及建模不断增加的活动时间戳，事件帧间时间间隙，事件类型以及事件之间的影响 - 在不同序列内和跨越不同序列之间的影响。这种情况进一​​步加剧了与数据收集相关的约束。有限的数据，不完整的序列，隐私限制等随着这项工作中描述的研究方向，我们的目的是研究连续时间事件序列（CTES）的性质和设计稳健但可扩展的基于神经网络的模型，以克服上述问题。在这项工作中，我们使用标记的时间点流程（MTPP）来解决事件的基础生成分发，以解决广泛的现实问题。此外，我们突出了拟议方法对最先进的基线，后来报告了正在进行的研究问题的疗效。

Existing federated classification algorithms typically assume the local annotations at every client cover the same set of classes. In this paper, we aim to lift such an assumption and focus on a more general yet practical non-IID setting where every client can work on non-identical and even disjoint sets of classes (i.e., client-exclusive classes), and the clients have a common goal which is to build a global classification model to identify the union of these classes. Such heterogeneity in client class sets poses a new challenge: how to ensure different clients are operating in the same latent space so as to avoid the drift after aggregation? We observe that the classes can be described in natural languages (i.e., class names) and these names are typically safe to share with all parties. Thus, we formulate the classification problem as a matching process between data representations and class representations and break the classification model into a data encoder and a label encoder. We leverage the natural-language class names as the common ground to anchor the class representations in the label encoder. In each iteration, the label encoder updates the class representations and regulates the data representations through matching. We further use the updated class representations at each round to annotate data samples for locally-unaware classes according to similarity and distill knowledge to local models. Extensive experiments on four real-world datasets show that the proposed method can outperform various classical and state-of-the-art federated learning methods designed for learning with non-IID data.

The rise in data has led to the need for dimension reduction techniques, especially in the area of non-scalar variables, including time series, natural language processing, and computer vision. In this paper, we specifically investigate dimension reduction for time series through functional data analysis. Current methods for dimension reduction in functional data are functional principal component analysis and functional autoencoders, which are limited to linear mappings or scalar representations for the time series, which is inefficient. In real data applications, the nature of the data is much more complex. We propose a non-linear function-on-function approach, which consists of a functional encoder and a functional decoder, that uses continuous hidden layers consisting of continuous neurons to learn the structure inherent in functional data, which addresses the aforementioned concerns in the existing approaches. Our approach gives a low dimension latent representation by reducing the number of functional features as well as the timepoints at which the functions are observed. The effectiveness of the proposed model is demonstrated through multiple simulations and real data examples.

Landing an unmanned aerial vehicle unmanned aerial vehicle (UAV) on top of an unmanned surface vehicle (USV) in harsh open waters is a challenging problem, owing to forces that can damage the UAV due to a severe roll and/or pitch angle of the USV during touchdown. To tackle this, we propose a novel model predictive control (MPC) approach enabling a UAV to land autonomously on a USV in these harsh conditions. The MPC employs a novel objective function and an online decomposition of the oscillatory motion of the vessel to predict, attempt, and accomplish the landing during near-zero tilt of the landing platform. The nonlinear prediction of the motion of the vessel is performed using visual data from an onboard camera. Therefore, the system does not require any communication with the USV or a control station. The proposed method was analyzed in numerous robotics simulations in harsh and extreme conditions and further validated in various real-world scenarios.

Multiple studies have focused on predicting the prospective popularity of an online document as a whole, without paying attention to the contributions of its individual parts. We introduce the task of proactively forecasting popularities of sentences within online news documents solely utilizing their natural language content. We model sentence-specific popularity forecasting as a sequence regression task. For training our models, we curate InfoPop, the first dataset containing popularity labels for over 1.7 million sentences from over 50,000 online news documents. To the best of our knowledge, this is the first dataset automatically created using streams of incoming search engine queries to generate sentence-level popularity annotations. We propose a novel transfer learning approach involving sentence salience prediction as an auxiliary task. Our proposed technique coupled with a BERT-based neural model exceeds nDCG values of 0.8 for proactive sentence-specific popularity forecasting. Notably, our study presents a non-trivial takeaway: though popularity and salience are different concepts, transfer learning from salience prediction enhances popularity forecasting. We release InfoPop and make our code publicly available: https://github.com/sayarghoshroy/InfoPopularity