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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
331

Optimizing Capsule Networks

Shiri, Pouya 23 August 2022 (has links)
Capsule Network (CapsNet) was introduced in 2017 as the new generation of the image classifiers to perform supervised classification of images. It incorporates a new structure of neurons which is called a capsule. A capsule is basically a vector of neurons and serves as the basic computation unit in CapsNet. CapsNet has obtained state-of-the-art testing accuracy on the task of classifying the MNIST digit recognition dataset. Despite its fundamental advantages over CNNs, it has its own shortcomings as well. CapsNet provides a relatively high accuracy in classifying images with affine transforms applied to them and also classifying images containing overlapping categories, compared to CNNs. Unlike CNNs, CapsNet creates the representation based on the part to whole relationship of the features of different levels. As a result, it comes with a more robust representation of the input image. CapsNet could only get reasonable inference accuracy on small-scale datasets. Also, it only supports a limited number of categories in the classification task. Finally, CapsNet is a relatively slow network, which is mostly due to the iterative Dynamic Routing (DR) algorithm used in it. There have been several works trying to address the shortcomings of CapsNet since it was introduced. In this work, we focus on optimizing CapsNet in several aspects: the network speed i.e. training and testing times, the number of parameters in the network, the network accuracy and its generalization ability. We propose several optimizations in order to compensate for the drawbacks of CapsNet. First, we introduce the Quick-CapsNet (QCN) network with our primary focus on the network speed. QCN makes changes to the feature extractor of CapsNet and produces fewer capsules compared to the baseline network (Base-CaspsNet). It performs inference 5x faster on small-scale datasets i.e. MNIST, F-MNIST, SVHN and CIFAR-10. QCN however loses testing accuracy marginally compared to the baseline e.g. 1% for F-MNIST dataset. Our second contribution is designing a capsule-specific layer for the feature extractor of CapsNet referred to as the Convolutional Fully-Connected (CFC) layer. We employ the CFC layer into CapsNet and call this new architecture CFC-CapsNet. CFC layer is added on top of the current feature extractor to translate the feature map into capsules. This layer has two parameters: kernel size and the output dimension. We performed some experiments to explore the effect of these two parameters on the network performance. Using the CFC layer results in reducing the number of parameters, faster training and testing, and higher test accuracy. On the CIFAR-10 dataset, CFC-CapsNet gets 1.46% higher accuracy (with baseline of 71.69%) and 49% fewer number of parameters. CFC-CapsNet is 4x and 4.5x faster than Base-CapsNet on CIFAR-10 for training and testing respectively. Our third contribution includes the introduction of LE-CapsNet as a light, enhanced and resource-aware variant of CapsNet. This network contains a Primary Capsule Generator (PCG) module as well as a robust decoder. Using 3.8M weights, LE-CapsNet obtains 77.21% accuracy for the CIFAR-10 dataset while performing inference 4x faster than CapsNet. In addition, our proposed network is more robust at detecting images with affine transformations compared to CapsNet. We achieve 94.37% accuracy on the AffNIST dataset (compared to CapsNet's 90.52%). Finally, we propose a deep variant of CapsNet consisting of several capsule layers referred to as Deep Light CapsNet (DL-CasNet). In this work, we design the Capsule Summarization (CapsSum) layer to reduce the complexity of the proposed deep network by reducing the number of parameters. DL-CapsNet, while being highly accurate, employs a small number of parameters compared to the state-of-the-art CapsNet based networks. Moreover DL-CapsNet delivers faster training and inference. Using a 7-ensemble model on the CIFAR-10 dataset, we achieve a 91.29% accuracy. DL-CapsNet is among the few networks based on CapsNet that supports the CIFAR-100 dataset (68.36% test accuracy using the 7-ensemble model) and can process complex datasets with a high number of categories. / Graduate
332

Real-Time Resource Optimization for Wireless Networks

Huang, Yan 11 January 2021 (has links)
Resource allocation in modern wireless networks is constrained by increasingly stringent real-time requirements. Such real-time requirements typically come from, among others, the short coherence time on a wireless channel, the small time resolution for resource allocation in OFDM-based radio frame structure, or the low-latency requirements from delay-sensitive applications. An optimal resource allocation solution is useful only if it can be determined and applied to the network entities within its expected time. For today's wireless networks such as 5G NR, such expected time (or real-time requirement) can be as low as 1 ms or even 100 μs. Most of the existing resource optimization solutions to wireless networks do not explicitly take real-time requirement as a constraint when developing solutions. In fact, the mainstream of research works relies on the asymptotic complexity analysis for designing solution algorithms. Asymptotic complexity analysis is only concerned with the growth of its computational complexity as the input size increases (as in the big-O notation). It cannot capture the real-time requirement that is measured in wall-clock time. As a result, existing approaches such as exact or approximate optimization techniques from operations research are usually not useful in wireless networks in the field. Similarly, many problem-specific heuristic solutions with polynomial-time asymptotic complexities may suffer from a similar fate, if their complexities are not tested in actual wall-clock time. To address the limitations of existing approaches, this dissertation presents novel real- time solution designs to two types of optimization problems in wireless networks: i) problems that have closed-form mathematical models, and ii) problems that cannot be modeled in closed-form. For the first type of problems, we propose a novel approach that consists of (i) problem decomposition, which breaks an original optimization problem into a large number of small and independent sub-problems, (ii) search intensification, which identifies the most promising problem sub-space and selects a small set of sub-problems to match the available GPU processing cores, and (iii) GPU-based large-scale parallel processing, which solves the selected sub-problems in parallel and finds a near-optimal solution to the original problem. The efficacy of this approach has been illustrated by our solutions to the following two problems. • Real-Time Scheduling to Achieve Fair LTE/Wi-Fi Coexistence: We investigate a resource optimization problem for the fair coexistence between LTE and Wi-Fi in the unlicensed spectrum. The real-time requirement for finding the optimal channel division and LTE resource allocation solution is on 1 ms time scale. This problem involves the optimal division of transmission time for LTE and Wi-Fi across multi- ple unlicensed bands, and the resource allocation among LTE users within the LTE's "ON" periods. We formulate this optimization problem as a mixed-integer linear pro- gram and prove its NP-hardness. Then by exploiting the unique problem structure, we propose a real-time solution design that is based on problem decomposition and GPU-based parallel processing techniques. Results from an implementation on the NVIDIA GPU/CUDA platform demonstrate that the proposed solution can achieve near-optimal objective and meet the 1 ms timing requirement in 4G LTE. • An Ultrafast GPU-based Proportional Fair Scheduler for 5G NR: We study the popular proportional-fair (PF) scheduling problem in a 5G NR environment. The real-time requirement for determining the optimal (with respect to the PF objective) resource allocation and MCS selection solution is 125 μs (under 5G numerology 3). In this problem, we need to allocate frequency-time resource blocks on an operating channel and assign modulation and coding scheme (MCS) for each active user in the cell. We present GPF+ — a GPU based real-time PF scheduler. With GPF+, the original PF optimization problem is decomposed into a large number of small and in- dependent sub-problems. We then employ a cross-entropy based search intensification technique to identify the most promising problem sub-space and select a small set of sub-problems to fit into a GPU. After solving the selected sub-problems in parallel using GPU cores, we find the best sub-problem solution and use it as the final scheduling solution. Evaluation results show that GPF+ is able to provide near-optimal PF performance in a 5G cell while meeting the 125 μs real-time requirement. For the second type of problems, where there is no closed-form mathematical formulation, we propose to employ model-free deep learning (DL) or deep reinforcement learning (DRL) techniques along with judicious consideration of timing requirement throughout the design. Under DL/DRL, we employ deep function approximators (neural networks) to learn the unknown objective function of an optimization problem, approximate an optimal algorithm to find resource allocation solutions, or discover important mapping functions related to the resource optimization. To meet the real-time requirement, we propose to augment DL or DRL methods with optimization techniques at the input or output of the deep function approximators to reduce their complexities and computational time. Under this approach, we study the following two problems: • A DRL-based Approach to Dynamic eMBB/URLLC Multiplexing in 5G NR: We study the problem of dynamic multiplexing of eMBB and URLLC on the same channel through preemptive resource puncturing. The real-time requirement for determining the optimal URLLC puncturing solution is 1 ms (under 5G numerology 0). A major challenge in solving this problem is that it cannot be modeled using closed-form mathematical expressions. To address this issue, we develop a model-free DRL approach which employs a deep neural network to learn an optimal algorithm to allocate the URLLC puncturing over the operating channel, with the objective of minimizing the adverse impact from URLLC traffic on eMBB. Our contributions include a novel learning method that exploits the intrinsic properties of the URLLC puncturing optimization problem to achieve a fast and stable learning convergence, and a mechanism to ensure feasibility of the deep neural network's output puncturing solution. Experimental results demonstrate that our DRL-based solution significantly outperforms state-of-the-art algorithms proposed in the literature and meets the 1 ms real-time requirement for dynamic multiplexing. • A DL-based Link Adaptation for eMBB/URLLC Multiplexing in 5G NR: We investigate MCS selection for eMBB traffic under the impact of URLLC preemptive puncturing. The real-time requirement for determining the optimal MCSs for all eMBB transmissions scheduled in a transmission interval is 125 μs (under 5G numerology 3). The objective is to have eMBB meet a given block-error rate (BLER) target under the adverse impact of URLLC puncturing. Since this problem cannot be mathematically modeled in closed-form, we proposed a DL-based solution design that uses a deep neural network to learn and predict the BLERs of a transmission under each MCS level. Then based on the BLER predictions, an optimal MCS can be found for each transmission that can achieve the BLER target. To meet the 5G real-time requirement, we implement this design through a hybrid CPU and GPU architecture to minimize the execution time. Extensive experimental results show that our design can select optimal MCS under the impact of preemptive puncturing and meet the 125 μs timing requirement. / Doctor of Philosophy / In modern wireless networks such as 4G LTE and 5G NR, the optimal allocation of radio resources must be performed within a real-time requirement of 1 ms or even 100 μs time scale. Such a real-time requirement comes from the physical properties of wireless channels, the short time resolution for resource allocation defined in the wireless communication standards, and the low-latency requirement from delay-sensitive applications. Real-time requirement, although necessary for wireless networks in the field, has hardly been considered as a key constraint for solution design in the research community. Existing solutions in the literature mostly consider theoretical computational complexities, rather than actual computation time as measured by wall clock. To address the limitations of existing approaches, this dissertation presents real-time solution designs to two types of optimization problems in wireless networks: i) problems that have mathematical models, and ii) problems that cannot be modeled mathematically. For the first type of problems, we propose a novel approach that consists of (i) problem decomposition, (ii) search intensification, and (iii) GPU-based large-scale parallel processing techniques. The efficacy of this approach has been illustrated by our solutions to the following two problems. • Real-Time Scheduling to Achieve Fair LTE/Wi-Fi Coexistence: We investigate a resource optimization problem for the fair coexistence between LTE and Wi-Fi users in the same (unlicensed) spectrum. The real-time requirement for finding the optimal LTE resource allocation solution is on 1 ms time scale. • An Ultrafast GPU-based Proportional Fair Scheduler for 5G NR: We study the popular proportional-fair (PF) scheduling problem in a 5G NR environment. The real-time requirement for determining the optimal resource allocation and modulation and coding scheme (MCS) for each user is 125 μs. For the second type of problems, where there is no mathematical formulation, we propose to employ model-free deep learning (DL) or deep reinforcement learning (DRL) techniques along with judicious consideration of timing requirement throughout the design. Under this approach, we study the following two problems: • A DRL-based Approach to Dynamic eMBB/URLLC Multiplexing in 5G NR: We study the problem of dynamic multiplexing of eMBB and URLLC on the same channel through preemptive resource puncturing. The real-time requirement for determining the optimal URLLC puncturing solution is 1 ms. • A DL-based Link Adaptation for eMBB/URLLC Multiplexing in 5G NR: We investigate MCS selection for eMBB traffic under the impact of URLLC preemptive puncturing. The real-time requirement for determining the optimal MCSs for all eMBB transmissions scheduled in a transmission interval is 125 μs.
333

Asymmetry Learning for Out-of-distribution Tasks

Chandra Mouli Sekar (18437814) 02 May 2024 (has links)
<p dir="ltr">Despite their astonishing capacity to fit data, neural networks have difficulties extrapolating beyond training data distribution. When the out-of-distribution prediction task is formalized as a counterfactual query on a causal model, the reason for their extrapolation failure is clear: neural networks learn spurious correlations in the training data rather than features that are causally related to the target label. This thesis proposes to perform a causal search over a known family of causal models to learn robust (maximally invariant) predictors for single- and multiple-environment extrapolation tasks.</p><p dir="ltr">First, I formalize the out-of-distribution task as a counterfactual query over a structural causal model. For single-environment extrapolation, I argue that symmetries of the input data are valuable for training neural networks that can extrapolate. I introduce Asymmetry learning, a new learning paradigm that is guided by the hypothesis that all (known) symmetries are mandatory even without evidence in training, unless the learner deems it inconsistent with the training data. Asymmetry learning performs a causal model search to find the simplest causal model defining a causal connection between the target labels and the symmetry transformations that affect the label. My experiments on a variety of out-of-distribution tasks on images and sequences show that proposed methods extrapolate much better than the standard neural networks.</p><p dir="ltr">Then, I consider multiple-environment out-of-distribution tasks in dynamical system forecasting that arise due to shifts in initial conditions or parameters of the dynamical system. I identify key OOD challenges in the existing deep learning and physics-informed machine learning (PIML) methods for these tasks. To mitigate these drawbacks, I combine meta-learning and causal structure discovery over a family of given structural causal models to learn the underlying dynamical system. In three simulated forecasting tasks, I show that the proposed approach is 2x to 28x more robust than the baselines.</p>
334

Size-Adaptive Convolutional Neural Network with Parameterized-Swish Activation for Enhanced Object Detection

Yashwanth Raj Venkata Krishnan (18322572) 03 June 2024 (has links)
<p> In computer vision, accurately detecting objects of varying sizes is essential for various applications, such as autonomous vehicle navigation and medical imaging diagnostics. Addressing the variance in object sizes presents a significant challenge requiring advanced computational solutions for reliable object recognition and processing. This research introduces a size-adaptive Convolutional Neural Network (CNN) framework to enhance detection performance across different object sizes. By dynamically adjusting the CNN’s configuration based on the observed distribution of object sizes, the framework employs statistical analysis and algorithmic decision-making to improve detection capabilities. Further innovation is presented through the Parameterized-Swish activation function. Distinguished by its dynamic parameters, this function is designed to better adapt to varying input patterns. It exceeds the performance of traditional activation functions by enabling faster model convergence and increasing detection accuracy, showcasing the effectiveness of adaptive activation functions in enhancing object detection systems. The implementation of this model has led to notable performance improvements: a 11.4% increase in mean Average Precision (mAP) and a 40.63% increase in frames per second (FPS) for small objects, demonstrating enhanced detection speed and accuracy. The model has achieved a 48.42% reduction in training time for medium-sized objects while still improving mAP, indicating significant efficiency gains without compromising precision. Large objects have seen a 16.9% reduction in training time and a 76.04% increase in inference speed, showcasing the model’s ability to expedite processing times substantially. Collectively, these advancements contribute to a more than 12% increase in detection efficiency and accuracy across various scenarios, highlighting the model’s robustness and adaptability in addressing the critical challenge of size variance in object detection. </p>
335

ENHANCING PRECISION OF OBJECT DETECTORS: BRIDGING CLASSIFICATION AND LOCALIZATION GAPS FOR 2D AND 3D MODELS

NIRANJAN RAVI (7013471) 03 June 2024 (has links)
<p dir="ltr">Artificial Intelligence (AI) has revolutionized and accelerated significant advancements in various fields such as healthcare, finance, education, agriculture and the development of autonomous vehicles. We are rapidly approaching Level 5 Autonomy due to recent developments in autonomous technology, including self-driving cars, robot navigation, smart traffic monitoring systems, and dynamic routing. This success has been made possible due to Deep Learning technologies and advanced Computer Vision (CV) algorithms. With the help of perception sensors such as Camera, LiDAR and RADAR, CV algorithms enable a self-driving vehicle to interact with the environment and make intelligent decisions. Object detection lays the foundations for various applications, such as collision and obstacle avoidance, lane detection, pedestrian and vehicular safety, and object tracking. Object detection has two significant components: image classification and object localization. In recent years, enhancing the performance of 2D and 3D object detectors has spiked interest in the research community. This research aims to resolve the drawbacks associated with localization loss estimation of 2D and 3D object detectors by addressing the bounding box regression problem, addressing the class imbalance issue affecting the confidence loss estimation, and finally proposing a dynamic cross-model 3D hybrid object detector with enhanced localization and confidence loss estimation.</p><p dir="ltr">This research aims to address challenges in object detectors through four key contributions. In the first part, we aim to address the problems associated with the image classification component of 2D object detectors. Class imbalance is a common problem associated with supervised training. Common causes are noisy data, a scene with a tiny object surrounded by background pixels, or a dense scene with too many objects. These scenarios can produce many negative samples compared to positive ones, affecting the network learning and reducing the overall performance. We examined these drawbacks and proposed an Enhanced Hard Negative Mining (EHNM) approach, which utilizes anchor boxes with 20% to 50% overlap and positive and negative samples to boost performance. The efficiency of the proposed EHNM was evaluated using Single Shot Multibox Detector (SSD) architecture on the PASCAL VOC dataset, indicating that the detection accuracy of tiny objects increased by 3.9% and 4% and the overall accuracy improved by 0.9%. </p><p dir="ltr">To address localization loss, our second approach investigates drawbacks associated with existing bounding box regression problems, such as poor convergence and incorrect regression. We analyzed various cases, such as when objects are inclusive of one another, two objects with the same centres, two objects with the same centres and similar aspect ratios. During our analysis, we observed existing intersections over Union (IoU) loss and its variant’s failure to address them. We proposed two new loss functions, Improved Intersection Over Union (IIoU) and Balanced Intersection Over Union (BIoU), to enhance performance and minimize computational efforts. Two variants of the YOLOv5 model, YOLOv5n6 and YOLOv5s, were utilized to demonstrate the superior performance of IIoU on PASCAL VOC and CGMU datasets. With help of ROS and NVIDIA’s devices, inference speed was observed in real-time. Extensive experiments were performed to evaluate the performance of BIoU on object detectors. The evaluation results indicated MASK_RCNN network trained on the COCO dataset, YOLOv5n6 network trained on SKU-110K and YOLOv5x trained on the custom e-scooter dataset demonstrated 3.70% increase on small objects, 6.20% on 55% overlap and 9.03% on 80% overlap.</p><p dir="ltr">In the earlier parts, we primarily focused on 2D object detectors. Owing to its success, we extended the scope of our research to 3D object detectors in the later parts. The third portion of our research aims to solve bounding box problems associated with 3D rotated objects. Existing axis-aligned loss functions suffer a performance gap if the objects are rotated. We enhanced the earlier proposed IIoU loss by considering two additional parameters: the objects’ Z-axis and rotation angle. These two parameters aid in localizing the object in 3D space. Evaluation was performed on LiDAR and Fusion methods on 3D KITTI and nuScenes datasets.</p><p dir="ltr">Once we addressed the drawbacks associated with confidence and localization loss, we further explored ways to increase the performance of cross-model 3D object detectors. We discovered from previous studies that perception sensors are volatile to harsh environmental conditions, sunlight, and blurry motion. In the final portion of our research, we propose a hybrid 3D cross-model detection network (MAEGNN) equipped with MaskedAuto Encoders 14 (MAE) and Graph Neural Networks (GNN) along with earlier proposed IIoU and ENHM. The performance evaluation on MAEGNN on the KITTI validation dataset and KITTI test set yielded a detection accuracy of 69.15%, 63.99%, 58.46% and 40.85%, 37.37% on 3D pedestrians with overlap of 50%. This developed hybrid detector overcomes the challenges of localization error and confidence estimation and outperforms many state-of-art 3D object detectors for autonomous platforms.</p>
336

Emosjonelt arbeid i offentlighetens tjeneste : En kvalitativ studie av politiets emosjonelle arbeid / Emotional Labor in Public Service : A qualitative study of the police’s emotional labor

Bru, Linn Sunniva, Nilsson, Therese January 2011 (has links)
A police officer may be subject to anumber of complex situationsand stresses intheir everyday work in which different emotionsmay occur, and whereemotional labour is necessary.  Our intent of the study isto increase understanding of the emotional partof the police work. How the police areexperiencing an emotional preparation for work,experiencing the feelings that occur in work,and how emotions are processed. Wewill also see howthe police handlethe transmutation from their private feelings anddeal with the waythey express the emotional expressions that the colleagues and thepublic expect to see in different situations. We will see how theyhandle the transmutation from public feelings toprivate feelings again.The intention of the study is also to see if thereare organizational conditions that cansimplify the emotional labour of a police,and identify the conditions. We haveconducted seven qualitativeinterviews. By means of thecollected empirical and the theoretical basewe will analyze the emotional labour of a police, and analyze the factors that may affect the emotionallabour.The analysis describes the presence of individual factors, social support and organizational factorsthat can affectthe emotional workof a police. We illustratethe emotional workof a police with thehelp of a model that shows the relationship between different the factors. / Politietkan bli utsatt for en rekke komplekse og påkjennende situasjoner i sinarbeidshverdag hvor ulike følelser kan oppstå, og der et emosjonelt arbeid blirnødvendig. Vårt formål med studiet er å øke forståelsen for denemosjonelle delen i politiets arbeid. Hvordan politiet opplever forberedelsentil et emosjonelt arbeid, opplever følelsene som oppstår i arbeidet, samthvordan følelsene bearbeides. Vi vil også se hvordan politiet handtererovergangen fra sine private følelser, og handterer de slik at de viser defølelsesutrykk som kollegaer og allmennheten forventer seg å se i ulikesituasjoner. Vi vil også se hvordan overgangen handteres fra de offentligefølelsene til private igjen. Studiets formål er å se om det finnesorganisatoriske forutsetninger som kan forenkle det emosjonelle arbeidet til politiet,og hvordan disse ser ut. Vi har gjennomført syv kvalitative intervjuer. Med hjelp av den innsamledeempirien og studiets teoretiske utgangspunkt analyserer vi politietsemosjonelle arbeid, og faktorer som kan påvirke det emosjonelle arbeidet. Analysen beskriver at det finnesindividuelle faktorer, sosial støtte og organisatoriske faktorer som kanpåvirke det emosjonelle arbeidet til politiet. Vi illustrerer det emosjonellearbeidet til politiet med hjelp av en egen modell som viser sammenhengen mellomde ulike faktorene.
337

External strengthening of reinforced concrete pier caps

Bechtel, Andrew Joseph 17 October 2011 (has links)
The shear capacity of reinforced concrete pier caps in existing bridge support systems can be a factor which limits the capacity of an existing bridge. In their usual configuration, pier caps behave as deep beams and have the ability to carry load through tied arch action after the formation of diagonal cracks. Externally bonded fiber reinforced polymer (FRP) reinforcement has been shown to increase the shear capacity of reinforced concrete members which carry load through beam action. However, there is an insufficient amount of research to make it a viable strengthening system for beams which carry load through arch action, such as pier caps. Accordingly, this research was aimed at investigating the behavior of reinforced concrete pier caps through a coordinated experimental and analytical program and to recommend an external strengthening method for pier caps with perceived deficiencies in shear strength. The experimental study was performed on laboratory specimens based on an existing bridge in Georgia. A number of factors were examined, including size, percentage longitudinal reinforcement and crack control reinforcement. The results showed that increasing the longitudinal tension reinforcement increased the beam capacity by changing the shape of the tied arch. In contrast, the presence of crack control reinforcement did not change the point at which diagonal cracking occurred, but it did increase the ultimate capacity by reinforcing the concrete against splitting. The results of the experimental study were used in conjunction with a larger database to examine different analytical methods for estimating the ultimate capacity of deep beams, and a new method was developed for the design of external strengthening. Two specimens were tested with externally bonded FRP reinforcement applied longitudinally to increase the strength of the tension tie. The test results correlated well with the proposed method of analysis and showed that increasing the strength of the longitudinal tension tie is an effective way to increase the strength of a reinforced concrete deep beam.
338

Simulated Fixed-Wing Aircraft Attitude Control using Reinforcement Learning Methods

David Jona Richter (11820452) 20 December 2021 (has links)
<div>Autonomous transportation is a research field that has gained huge interest in recent years, with autonomous electric or hydrogen cars coming ever closer to seeing everyday use. Not just cars are subject to autonomous research though, the field of aviation is also being explored for fully autonomous flight. One very important aspect for making autonomous flight a reality is attitude control, the control of roll, pitch, and sometimes yaw. Traditional approaches for automated attitude control use PID (proportional-integral-derivative) controllers, which use hand-tuned parameters to fulfill the task. In this work, however, the use of Reinforcement Learning algorithms for attitude control will be explored. With the surge of more and more powerful artificial neural networks, which have proven to be universally usable function approximators, Deep Reinforcement Learning also becomes an intriguing option. </div><div>A software toolkit will be developed and used to allow for the use of multiple flight simulators to train agents with Reinforcement Learning as well as Deep Reinforcement Learning. Experiments will be run using different hyperparamters, algorithms, state representations, and reward functions to explore possible options for autonomous attitude control using Reinforcement Learning.</div>
339

Deep Active Learning for Image Classification using Different Sampling Strategies

Saleh, Shahin January 2021 (has links)
Convolutional Neural Networks (CNNs) have been proved to deliver great results in the area of computer vision, however, one fundamental bottleneck with CNNs is the fact that it is heavily dependant on the ground truth, that is, labeled training data. A labeled dataset is a group of samples that have been tagged with one or more labels. In this degree project, we mitigate the data greedy behavior of CNNs by applying deep active learning with various kinds of sampling strategies. The main focus will be on the sampling strategies random sampling, least confidence sampling, margin sampling, entropy sampling, and K- means sampling. We choose to study the random sampling strategy since it will work as a baseline to the other sampling strategies. Moreover, the least confidence sampling, margin sampling, and entropy sampling strategies are uncertainty based sampling strategies, hence, it is interesting to study how they perform in comparison with the geometrical based K- means sampling strategy. These sampling strategies will help to find the most informative/representative samples amongst all unlabeled samples, thus, allowing us to label fewer samples. Furthermore, the benchmark datasets MNIST and CIFAR10 will be used to verify the performance of the various sampling strategies. The performance will be measured in terms of accuracy and less data needed. Lastly, we concluded that by using least confidence sampling and margin sampling we reduced the number of labeled samples by 79.25% in comparison with the random sampling strategy for the MNIST dataset. Moreover, by using entropy sampling we reduced the number of labeled samples by 67.92% for the CIFAR10 dataset. / Faltningsnätverk har visat sig leverera bra resultat inom området datorseende, men en fundamental flaskhals med Faltningsnätverk är det faktum att den är starkt beroende av klassificerade datapunkter. I det här examensarbetet hanterar vi Faltningsnätverkens giriga beteende av klassificerade datapunkter genom att använda deep active learning med olika typer av urvalsstrategier. Huvudfokus kommer ligga på urvalsstrategierna slumpmässigt urval, minst tillförlitlig urval, marginal baserad urval, entropi baserad urval och K- means urval. Vi väljer att studera den slumpmässiga urvalsstrategin eftersom att den kommer användas för att mäta prestandan hos de andra urvalsstrategierna. Dessutom valde vi urvalsstrategierna minst tillförlitlig urval, marginal baserad urval, entropi baserad urval eftersom att dessa är osäkerhetsbaserade strategier som är intressanta att jämföra med den geometribaserade strategin K- means. Dessa urvalsstrategier hjälper till att hitta de mest informativa/representativa datapunkter bland alla oklassificerade datapunkter, vilket gör att vi behöver klassificera färre datapunkter. Vidare kommer standard dastaseten MNIST och CIFAR10 att användas för att verifiera prestandan för de olika urvalsstrategierna. Slutligen drog vi slutsatsen att genom att använda minst tillförlitlig urval och marginal baserad urval minskade vi mängden klassificerade datapunkter med 79, 25%, i jämförelse med den slumpmässiga urvalsstrategin, för MNIST- datasetet. Dessutom minskade vi mängden klassificerade datapunkter med 67, 92% med hjälp av entropi baserad urval för CIFAR10datasetet.
340

Experimental and analytical investigation of reinforced concrete bridge pier caps with an externally bonded stainless steel system

Kim, Sung Hu 07 January 2016 (has links)
This research is aimed at examining experimentally and analytically the behavior of reinforced concrete bridge pier caps strengthened with externally bonded reinforcement. In the experimental study, nine full-scale reinforced concrete bridge pier caps were built, externally strengthened with stainless steel reinforcement, and ten tested to failure. Load, deflection, and strain measurements were collected and two potential failure mechanisms were identified. In the analytical part of this work, mechanics-based equations were developed for calculating the shear strength of these types of structural elements when a diagonal shear crack is formed under loading. In addition, a combined strut-and-tie/truss model is proposed for determining the strength of reinforced concrete bridge caps with externally bonded reinforcement. Results from both experimental and analytical studies were compared and design recommendations are made for future adoption in bridge and building codes and specifications.

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