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。

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.

Concept bottleneck models (CBMs) (Koh et al. 2020) are interpretable neural networks that first predict labels for human-interpretable concepts relevant to the prediction task, and then predict the final label based on the concept label predictions.We extend CBMs to interactive prediction settings where the model can query a human collaborator for the label to some concepts. We develop an interaction policy that, at prediction time, chooses which concepts to request a label for so as to maximally improve the final prediction. We demonstrate thata simple policy combining concept prediction uncertainty and influence of the concept on the final prediction achieves strong performance and outperforms a static approach proposed in Koh et al. (2020) as well as active feature acquisition methods proposed in the literature. We show that the interactiveCBM can achieve accuracy gains of 5-10% with only 5 interactions over competitive baselines on the Caltech-UCSDBirds, CheXpert and OAI datasets.

Selective classification involves identifying the subset of test samples that a model can classify with high accuracy, and is important for applications such as automated medical diagnosis. We argue that this capability of identifying uncertain samples is valuable for training classifiers as well, with the aim of building more accurate classifiers. We unify these dual roles by training a single auxiliary meta-network to output an importance weight as a function of the instance. This measure is used at train time to reweight training data, and at test-time to rank test instances for selective classification. A second, key component of our proposal is the meta-objective of minimizing dropout variance (the variance of classifier output when subjected to random weight dropout) for training the metanetwork. We train the classifier together with its metanetwork using a nested objective of minimizing classifier loss on training data and meta-loss on a separate meta-training dataset. We outperform current state-of-the-art on selective classification by substantial margins--for instance, upto 1.9% AUC and 2% accuracy on a real-world diabetic retinopathy dataset. Finally, our meta-learning framework extends naturally to unsupervised domain adaptation, given our unsupervised variance minimization meta-objective. We show cumulative absolute gains of 3.4% / 3.3% accuracy and AUC over the other baselines in domain shift settings on the Retinopathy dataset using unsupervised domain adaptation.

Many real-world learning scenarios face the challenge of slow concept drift, where data distributions change gradually over time. In this setting, we pose the problem of learning temporally sensitive importance weights for training data, in order to optimize predictive accuracy. We propose a class of temporal reweighting functions that can capture multiple timescales of change in the data, as well as instance-specific characteristics. We formulate a bi-level optimization criterion, and an associated meta-learning algorithm, by which these weights can be learned. In particular, our formulation trains an auxiliary network to output weights as a function of training instances, thereby compactly representing the instance weights. We validate our temporal reweighting scheme on a large real-world dataset of 39M images spread over a 9 year period. Our extensive experiments demonstrate the necessity of instance-based temporal reweighting in the dataset, and achieve significant improvements to classical batch-learning approaches. Further, our proposal easily generalizes to a streaming setting and shows significant gains compared to recent continual learning methods.

Twenty20板球，有时是二十20，经常缩写为T20，是板球的一小部分。在一场二十二十比赛中，两支球员组成的两支球队都有一局，最多仅限20分。这个版本的板球尤其是不可预测的，这是它最近在近期越来越受欢迎的原因之一。但是，在本文中，我们尝试了四种不同的方法来预测T20板球比赛的结果。具体来说，我们要考虑：以前的竞争团队参与者的绩效统计数据，从知名的板球统计网站获得的球员的评分，以相似的性能统计数据和基于ELO基于ELO的方法来汇率玩家。我们通过使用逻辑回归，支持向量机，贝叶斯网络，决策树，随机森林来比较每种方法的性能。

可靠的异常检测对于深度学习模型的现实应用至关重要。深层生成模型产生的可能性虽然进行了广泛的研究，但仍被认为是对异常检测的不切实际的。一方面，深层生成模型的可能性很容易被低级输入统计数据偏差。其次，许多用于纠正这些偏见的解决方案在计算上是昂贵的，或者对复杂的天然数据集的推广不佳。在这里，我们使用最先进的深度自回归模型探索离群值检测：PixelCNN ++。我们表明，PixelCNN ++的偏见主要来自基于局部依赖性的预测。我们提出了两个我们称为“震动”和“搅拌”的徒转化家族，它们可以改善低水平的偏见并隔离长期依赖性对PixelCNN ++可能性的贡献。这些转换在计算上是便宜的，并且在评估时很容易应用。我们使用五个灰度和六个自然图像数据集对我们的方法进行了广泛的评估，并表明它们达到或超过了最新的离群检测性能。总而言之，轻巧的补救措施足以在具有深层生成模型的图像上实现强大的离群检测。

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。

构建可靠的AI决策支持系统需要一组强大的数据来培训模型；在数量和多样性方面。在资源有限的设置或在部署的早期阶段中，获取此类数据集可能很困难。样本拒绝是应对这一挑战的一种方法，但是该领域的许多现有工作都不适合这种情况。本文证明了该立场并提出了一个简单的解决方案作为概念基线的证明。

本文向许多受访者调查了同时的偏好和度量学习。一组由$ d $二维功能向量和表格的配对比较``项目$ i $都比item $ j $更可取'的项目。我们的模型共同学习了一个距离指标，该指标表征了人群对项目相似性的一般度量，以及每个用户反映其个人喜好的潜在理想点。该模型具有捕获个人喜好的灵活性，同时享受在人群中摊销的度量学习样本成本。我们首先以无声的，连续的响应设置（即等于项目距离的差异）来研究这个问题，以了解学习的基本限制。接下来，我们建立了嘈杂的预测错误保证，可以从人类受访者那里收集诸如二进制测量值，并显示样品复杂性在基础度量较低时如何提高。最后，我们根据响应分布的假设建立恢复保证。我们在模拟数据和大量用户的颜色偏好判断数据集上演示了模型的性能。