South America
Linear Convergence of ISTA and FISTA
Li, Bowen, Shi, Bin, Yuan, Ya-xiang
In this paper, we revisit the class of iterative shrinkage-thresholding algorithms (ISTA) for solving the linear inverse problem with sparse representation, which arises in signal and image processing. It is shown in the numerical experiment to deblur an image that the convergence behavior in the logarithmic-scale ordinate tends to be linear instead of logarithmic, approximating to be flat. Making meticulous observations, we find that the previous assumption for the smooth part to be convex weakens the least-square model. Specifically, assuming the smooth part to be strongly convex is more reasonable for the least-square model, even though the image matrix is probably ill-conditioned. Furthermore, we improve the pivotal inequality tighter for composite optimization with the smooth part to be strongly convex instead of general convex, which is first found in [Li et al., 2022]. Based on this pivotal inequality, we generalize the linear convergence to composite optimization in both the objective value and the squared proximal subgradient norm. Meanwhile, we set a simple ill-conditioned matrix which is easy to compute the singular values instead of the original blur matrix. The new numerical experiment shows the proximal generalization of Nesterov's accelerated gradient descent (NAG) for the strongly convex function has a faster linear convergence rate than ISTA. Based on the tighter pivotal inequality, we also generalize the faster linear convergence rate to composite optimization, in both the objective value and the squared proximal subgradient norm, by taking advantage of the well-constructed Lyapunov function with a slight modification and the phase-space representation based on the high-resolution differential equation framework from the implicit-velocity scheme.
Deep learning-based approaches for human motion decoding in smart walkers for rehabilitation
Gonรงalves, Carolina, Lopes, Joรฃo M., Moccia, Sara, Berardini, Daniele, Migliorelli, Lucia, Santos, Cristina P.
Gait disabilities are among the most frequent worldwide. Their treatment relies on rehabilitation therapies, in which smart walkers are being introduced to empower the user's recovery and autonomy, while reducing the clinicians effort. For that, these should be able to decode human motion and needs, as early as possible. Current walkers decode motion intention using information of wearable or embedded sensors, namely inertial units, force and hall sensors, and lasers, whose main limitations imply an expensive solution or hinder the perception of human movement. Smart walkers commonly lack a seamless human-robot interaction, which intuitively understands human motions. A contactless approach is proposed in this work, addressing human motion decoding as an early action recognition/detection problematic, using RGB-D cameras. We studied different deep learning-based algorithms, organised in three different approaches, to process lower body RGB-D video sequences, recorded from an embedded camera of a smart walker, and classify them into 4 classes (stop, walk, turn right/left). A custom dataset involving 15 healthy participants walking with the device was acquired and prepared, resulting in 28800 balanced RGB-D frames, to train and evaluate the deep networks. The best results were attained by a convolutional neural network with a channel attention mechanism, reaching accuracy values of 99.61% and above 93%, for offline early detection/recognition and trial simulations, respectively. Following the hypothesis that human lower body features encode prominent information, fostering a more robust prediction towards real-time applications, the algorithm focus was also evaluated using Dice metric, leading to values slightly higher than 30%. Promising results were attained for early action detection as a human motion decoding strategy, with enhancements in the focus of the proposed architectures.
Computational Pathology for Brain Disorders
Jimenez, Gabriel, Racoceanu, Daniel
Non-invasive brain imaging techniques allow understanding the behavior and macro changes in the brain to determine the progress of a disease. However, computational pathology provides a deeper understanding of brain disorders at cellular level, able to consolidate a diagnosis and make the bridge between the medical image and the omics analysis. In traditional histopathology, histology slides are visually inspected, under the microscope, by trained pathologists. This process is time-consuming and labor-intensive; therefore, the emergence of Computational Pathology has triggered great hope to ease this tedious task and make it more robust. This chapter focuses on understanding the state-of-the-art machine learning techniques used to analyze whole slide images within the context of brain disorders. We present a selective set of remarkable machine learning algorithms providing discriminative approaches and quality results on brain disorders. These methodologies are applied to different tasks, such as monitoring mechanisms contributing to disease progression and patient survival rates, analyzing morphological phenotypes for classification and quantitative assessment of disease, improving clinical care, diagnosing tumor specimens, and intraoperative interpretation. Thanks to the recent progress in machine learning algorithms for high-content image processing, computational pathology marks the rise of a new generation of medical discoveries and clinical protocols, including in brain disorders.
A Case Study in Engineering a Conversational Programming Assistant's Persona
Ross, Steven I., Muller, Michael, Martinez, Fernando, Houde, Stephanie, Weisz, Justin D.
One particularly interesting aspect of these models is that their behavior can be configured by a prompt, the initial text provided to the model, which establishes a pattern that the model attempts to continue. General purpose Large Language models can be fine-tuned on specific corpora to provide expertise in a particular domain. One such model is the OpenAI Codex model [3], a 12 billion parameter version of GPT-3 [2, 11], fine-tuned on code samples from 54 million public software repositories on GitHub. This model powers Github Co-Pilot [5], which primarily provides code-completion services within an Integrated Development Environment. We wondered whether such a model could power a conversational programming assistant and perhaps approach the vision laid out by Rich and Waters for their Programmer's Apprentice [15]. We developed the Programmer's Assistant prototype to explore this possibility, and to test whether potential users would find this sort of system useful and desirable [16]. In this paper we will review the steps taken to engineer the prompt for the Programmer's Assistant that used the Codex model to power an interactive conversational assistant, and how we evolved the prompt to establish the desired persona and behavior.
On the feasibility of attacking Thai LPR systems with adversarial examples
Jiamsuchon, Chissanupong, Suaboot, Jakapan, Rattanavipanon, Norrathep
Recent advances in deep neural networks (DNNs) have significantly enhanced the capabilities of optical character recognition (OCR) technology, enabling its adoption to a wide range of real-world applications. Despite this success, DNN-based OCR is shown to be vulnerable to adversarial attacks, in which the adversary can influence the DNN model's prediction by carefully manipulating input to the model. Prior work has demonstrated the security impacts of adversarial attacks on various OCR languages. However, to date, no studies have been conducted and evaluated on an OCR system tailored specifically for the Thai language. To bridge this gap, this work presents a feasibility study of performing adversarial attacks on a specific Thai OCR application -- Thai License Plate Recognition (LPR). Moreover, we propose a new type of adversarial attack based on the \emph{semi-targeted} scenario and show that this scenario is highly realistic in LPR applications. Our experimental results show the feasibility of our attacks as they can be performed on a commodity computer desktop with over 90% attack success rate.
Post-COVID Changes Accelerate Automation in Brazil
More companies in Brazil are adopting intelligent automation solutions and services as part of a wave of digital transformation that began during the COVID-19 pandemic and continues to accelerate, according to a new research report published today by Information Services Group (ISG) (Nasdaq: III), a leading global technology research and advisory firm. "Leading service providers are helping organizations integrate these tools, along with governance frameworks and change management processes." The 2022 ISG Provider Lens Intelligent Automation -- Services and Solutions report for Brazil finds several types of automation are gaining traction in the country, which is one of the largest automation markets in South America. Companies are acting to increase efficiency, better understand their processes and solve IT problems before they disrupt operations. "The challenges that companies in Brazil have faced since the pandemic call for comprehensive, modern automation solutions," said Chip Wagner, CEO of ISG Automation.
Neural Spline Search for Quantile Probabilistic Modeling
Sun, Ruoxi, Li, Chun-Liang, Arik, Sercan O., Dusenberry, Michael W., Lee, Chen-Yu, Pfister, Tomas
Accurate estimation of output quantiles is crucial in many use cases, where it is desired to model the range of possibility. Modeling target distribution at arbitrary quantile levels and at arbitrary input attribute levels are important to offer a comprehensive picture of the data, and requires the quantile function to be expressive enough. The quantile function describing the target distribution using quantile levels is critical for quantile regression. Although various parametric forms for the distributions (that the quantile function specifies) can be adopted, an everlasting problem is selecting the most appropriate one that can properly approximate the data distributions. In this paper, we propose a non-parametric and data-driven approach, Neural Spline Search (NSS), to represent the observed data distribution without parametric assumptions. NSS is flexible and expressive for modeling data distributions by transforming the inputs with a series of monotonic spline regressions guided by symbolic operators. We demonstrate that NSS outperforms previous methods on synthetic, real-world regression and time-series forecasting tasks.
SlideVQA: A Dataset for Document Visual Question Answering on Multiple Images
Tanaka, Ryota, Nishida, Kyosuke, Nishida, Kosuke, Hasegawa, Taku, Saito, Itsumi, Saito, Kuniko
Visual question answering on document images that contain textual, visual, and layout information, called document VQA, has received much attention recently. Although many datasets have been proposed for developing document VQA systems, most of the existing datasets focus on understanding the content relationships within a single image and not across multiple images. In this study, we propose a new multi-image document VQA dataset, SlideVQA, containing 2.6k+ slide decks composed of 52k+ slide images and 14.5k questions about a slide deck. SlideVQA requires complex reasoning, including single-hop, multi-hop, and numerical reasoning, and also provides annotated arithmetic expressions of numerical answers for enhancing the ability of numerical reasoning. Moreover, we developed a new end-to-end document VQA model that treats evidence selection and question answering in a unified sequence-to-sequence format. Experiments on SlideVQA show that our model outperformed existing state-of-the-art QA models, but that it still has a large gap behind human performance. We believe that our dataset will facilitate research on document VQA.
Understanding Difficulty-based Sample Weighting with a Universal Difficulty Measure
Zhou, Xiaoling, Wu, Ou, Zhu, Weiyao, Liang, Ziyang
Sample weighting is widely used in deep learning. A large number of weighting methods essentially utilize the learning difficulty of training samples to calculate their weights. In this study, this scheme is called difficulty-based weighting. Two important issues arise when explaining this scheme. First, a unified difficulty measure that can be theoretically guaranteed for training samples does not exist. The learning difficulties of the samples are determined by multiple factors including noise level, imbalance degree, margin, and uncertainty. Nevertheless, existing measures only consider a single factor or in part, but not in their entirety. Second, a comprehensive theoretical explanation is lacking with respect to demonstrating why difficulty-based weighting schemes are effective in deep learning. In this study, we theoretically prove that the generalization error of a sample can be used as a universal difficulty measure. Furthermore, we provide formal theoretical justifications on the role of difficulty-based weighting for deep learning, consequently revealing its positive influences on both the optimization dynamics and generalization performance of deep models, which is instructive to existing weighting schemes.