Anomaly detection is the identification of instances that substantially deviate from the majority of the data and do not conform to a well-defined normal behavior. Investigating time series anomalies has become increa...
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ISBN:
(数字)9798331520861
ISBN:
(纸本)9798331520878
Anomaly detection is the identification of instances that substantially deviate from the majority of the data and do not conform to a well-defined normal behavior. Investigating time series anomalies has become increasingly popular in recent years due to widely deployed IoT devices and sensors. Although most existing methods apply image anomaly detection algorithms directly on time series and commonly assume the data is IID (independent and identically distributed). However, in most realworld applications, the underlying data distribution alters over time. Changes in data over time are referred to as concept drift and can significantly degrade the efficacy of an anomaly detection model. Existing research also indicates that the majority of anomaly detection frameworks ignored concept drift, resulting in poor long-term model performance. This paper presents an ensemble-based, unsupervised anomaly detection framework that is adaptive to the concept drift in time series data. Both distribution and performance-based techniques are used to detect concept drift and update the model to ensure the framework’s longterm performance reliability. The proposed method is evaluated using a real-world univariate time series data that captures sea surface temperature data over a 2 -year period. By comparing our proposed framework to other state-of-the-art algorithms, we demonstrate our proposed method has obvious benefits in accuracy and long-term stability.
Spatially aligning two computed tomography (CT) scans of the lung using automated image registration techniques is a challenging task due to the deformable nature of the lung. However, existing deep-learning-based lun...
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ISBN:
(数字)9798350313338
ISBN:
(纸本)9798350313345
Spatially aligning two computed tomography (CT) scans of the lung using automated image registration techniques is a challenging task due to the deformable nature of the lung. However, existing deep-learning-based lung CT registration models are not trained with explicit anatomical knowledge. We propose the deformable anatomy-aware registration toolkit (DART), a masked autoencoder (MAE)-based approach, to improve the keypoint-supervised registration of lung CTs. Our method incorporates features from multiple decoders of networks trained to segment anatomical structures, including the lung, ribs, vertebrae, lobes, vessels, and airways, to ensure that the MAE learns relevant features corresponding to the anatomy of the lung. The pretrained weights of the transformer encoder and patch embeddings are then used as the initialization for the training of downstream registration. We compare DART to existing state-of-the-art registration models. Our experiments show that DART outperforms the baseline models (Voxelmorph, ViT-V-Net, and MAE-TransRNet) in terms of target registration error of both corrField-generated keypoints with 17%, 13%, and 9% relative improvement, respectively, and bounding box centers of nodules with 27%, 10%, and 4% relative improvement, respectively. Our implementation is available at https://***/yunzhengzhu/DART.
Energy production with less impact on the environment is a great challenge for third world countries like Bangladesh, due to excessive power demand and fewer access to power production technology. The current state of...
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Local electricity markets (LEMs) have recently emerged as a promising paradigm towards realizing the value of distributed energy resources (DERs), by enabling a) provision of flexibility services (FS) by the DERs to s...
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ISBN:
(数字)9798350386493
ISBN:
(纸本)9798350386509
Local electricity markets (LEMs) have recently emerged as a promising paradigm towards realizing the value of distributed energy resources (DERs), by enabling a) provision of flexibility services (FS) by the DERs to system operators, and b) local energy trading among prosumers. However, existing work has only explored these two market functions in silos and has not comprehensively considered the effect of regulated charges. The recent UK innovation project Liverpool Energy Xchange aims at addressing these gaps, by designing a LEM that enables co-optimized local energy trading and FS provision. This paper firstly outlines the market design aspects of the proposed LEM. Secondly, it presents a quantitative validation of its benefits, based on a test case involving actual UK market data and operating data from prosumer sites in Liverpool, demonstrating a 27% reduction of the yearly net electricity cost. Finally, it discusses barriers the project has identified towards the realization of LEMs.
In this paper, an analytical modelling of power loss distribution has been addressed for different traction current source inverters. After having described the topologies and modulation strategies, modelling of losse...
In this paper, an analytical modelling of power loss distribution has been addressed for different traction current source inverters. After having described the topologies and modulation strategies, modelling of losses for each semiconductor device composing the inverters is provided. Then, the theoretical study has been validated through extensive simulations performed on a 35kW permanent magnet synchronous motor drive fed by the considered current source inverter topologies. Furthermore, the power loss and overall efficiency of current source inverter-based motor drives have been compared to a traditional two-level voltage source inverter fed motor drive including an output LC filter. Results underline pros and cons of using current source inverter topologies based on wide bandgap semiconductor devices.
Federated learning (FL) enables distributed devices to train a shared machine learning (ML) model collaboratively while protecting their data privacy. However, the resource-limited mobile devices suffer from intensive...
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A fundamental challenge in multi-agent reinforcement learning (MARL) is to learn the joint policy in an extremely large search space, which grows exponentially with the number of agents. Moreover, fully decentralized ...
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Numerous studies suggest that learning related but different tasks prior to a new task makes it easier, possibly because of our brain's neural pattern alignment mechanism. Specifically, the neural patterns in the ...
Numerous studies suggest that learning related but different tasks prior to a new task makes it easier, possibly because of our brain's neural pattern alignment mechanism. Specifically, the neural patterns in the new task align with those in the learned task, enabling the reuse of knowledge from the previous task to aid learning in the new task. Brain-machine interface (BMI) is an excellent tool for analyzing the dynamics of neural population patterns during new task learning by directly recording neural signals from the brain. If we can repeat the process of aligning neural pattern using a point registration algorithm with the recorded neural signals, it would provide a computational tool to help us understand the brain mechanism during task learning. Additionally, the pre-trained decoder parameters from the old task can be reused to expedite learning in the new task. However, the existing Iterative Closest Point (ICP) method easily fails as it is sensitive to neural data distribution. This paper proposes a pair-wise Kullback Leibler (KL) divergence optimizing framework for stable neural pattern alignment. The KL divergence measures the difference between the data distribution of the previous task and the aligned new task. The alignment process is formulated as an optimization problem by minimizing the KL divergence. The proposed algorithm is tested in a simulated experiment where a rat learns a two-lever discrimination task from a one-lever pressing task. Three scenarios are designed to test the feasibility of our algorithm, including non-Gaussian neural pattern shapes, noisy neural data, and different alignment angles. The results demonstrate that the proposed method is more robust than ICP, indicating its potential to discover the brain's alignment mechanism more accurately.
In the era of high-performance computing, the integration of Cellular Automata (CA) principles into low-power hardware is a challenging but intriguing endeavor. At the same time, memristors have gained attention due t...
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ISBN:
(数字)9798350330991
ISBN:
(纸本)9798350331004
In the era of high-performance computing, the integration of Cellular Automata (CA) principles into low-power hardware is a challenging but intriguing endeavor. At the same time, memristors have gained attention due to their potential in in-memory neuromorphic computing. As such, the concept of Wave Cellular Automata (WCA) is presented a novel computing paradigm that leverages CA principles and memristive devices for in-memory computing. However, memristive devices are subject to variability effects, which can impact their performance and, in the case of WCAs, the generation of oscillations crucial for computation. This paper explores the variability tolerance analysis of WCA both in CBRAM device level, but also in its oscillatory behavior. The analysis reveals that WCA operation remains robust even in the presence of variability, with the impact on oscillation amplitude being minor. All in all, proper circuit design and element selection play a significant role in mitigating the effects of variability.
Reinforcement Learning (RL) has been widely used to create generalizable autonomous vehicles. However, they rely on fixed reward functions that struggle to balance values like safety and efficiency. How can autonomous...
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ISBN:
(数字)9798350384574
ISBN:
(纸本)9798350384581
Reinforcement Learning (RL) has been widely used to create generalizable autonomous vehicles. However, they rely on fixed reward functions that struggle to balance values like safety and efficiency. How can autonomous vehicles balance different driving objectives and human values in a constantly changing environment? To bridge this gap, we propose an adaptive reward function that utilizes visual attention maps to detect pedestrians in the driving scene and dynamically switch between prioritizing safety or efficiency depending on the current observation. The visual attention map is used to provide spatial attention to the RL agent to boost the training efficiency of the pipeline. We evaluate the pipeline against variants of an occluded pedestrian crossing scenario in the CARLA Urban Driving simulator. Specifically, the proposed pipeline is compared against a modular setup that combines the well-established object detection model, YOLO, with a Proximal Policy Optimization (PPO) agent. The results indicate that the proposed approach can compete with the modular setup while yielding greater training efficiency. The trajectories collected with the approach confirm the effectiveness of the proposed adaptive reward function.
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