Testing analog circuits is more difficult than digital circuits. The reasons for this difficulty include continuous time and amplitude signals, lack of well-accepted testing techniques and time and cost required for its realization. The traditional method for testing analog circuits involves measuring all the performance parameters and comparing the measured parameters with the limits of the data-sheet specifications. Because of the large number of data-sheet specifications, the test generation and application requires long test times and expensive test equipment. This thesis proposes an implicit functional testing technique for analog circuits that can be easily implemented in BIST circuitry. The proposed technique does not require measuring data-sheet performance parameters. To simplify the testing only time domain digital input is required. For each circuit under test (CUT) a cross-covariance signature is computed from the test input and CUT's output. The proposed method requires a training sample of the CUT to be binned to the data-sheet specifications. The binned CUT sample cross-covariance signatures are mapped with a supervised machine learning classifier. For each bin, the classifiers select unique sub-sets of the cross-covariance signature. The trained classifier is then used to bin newly manufactured copies of the CUT. The proposed technique is evaluated on synthetic data generated from the Monte Carlo simulation of the nominal circuit. Results show the machine learning classifier must be chosen to match the imbalanced bin populations common in analog circuit testing. For sample sizes of 700+ and training for individual bins, classifier test escape rates ranged from 1000 DPM to 10,000 DPM.

Federated learning (FL), a novel distributed learning paradigm, has attracted significant attention in the past few years. Federated algorithms take a client/server computation model, and provide scope to train large-scale machine learning models over an edge-based distributed computing architecture. In the paradigm of FL, models are trained collaboratively under the coordination of a central server while storing data locally on the edge/clients. This thesis addresses critical challenges in FL, focusing on supervised learning, reinforcement learning (RL), control systems, and personalized system identification. By developing robust, efficient algorithms, our research enhances FL’s applicability across diverse, real-world environments characterized by data heterogeneity and communication constraints. In the first part, we introduce an algorithm for supervised FL to address the challenges posed by heterogeneous client data, ensuring stable convergence and effective learning, even with partial client participation. In the federated reinforcement learning (FRL) part, we develop algorithms that leverage similarities across heterogeneous environments to improve sample efficiency and accelerate policy learning. Our setup involves 𝑁 agents interacting with environments that share the same state and action space but differ in their reward functions and state transition kernels. Through rigorous theoretical analysis, we show that information exchange via FL can expedite both policy evaluation and optimization in decentralized, multi-agent settings, enabling faster, more efficient, and robust learning. Extending FL into control systems, we propose the 𝙵𝚎𝚍𝙻𝚀𝚁 algorithm, which enables agents with unknown but similar dynamics to collaboratively learn stabilizing policies, addressing the unique demands of closed-loop stability in federated control. Our method overcomes numerous technical challenges, such as heterogeneity in the agents’dynamics, multiple local updates, and stability concerns. We show that our proposed algorithm 𝙵𝚎𝚍𝙻𝚀𝚁 produces a common policy that, at each iteration, is stabilizing for all agents. We provide bounds on the distance between the common policy and each agent’s local optimal policy. Furthermore, we prove that when learning each agent’s optimal policy, 𝙵𝚎𝚍𝙻𝚀𝚁 achieves a sample complexity reduction proportional to the number of agents 𝑀 in a low-heterogeneity regime, compared to the single-agent setting. In the last part, we explore techniques for personalized system identification in FL, allowing clients to obtain customized models suited to their individual environments. We consider the problem of learning linear system models by observing multiple trajectories from systems with differing dynamics. This framework encompasses a collaborative scenario where several systems seeking to estimate their dynamics are partitioned into clusters according to system similarity. Thus, the systems within the same cluster can benefit from the observations made by the others. Considering this framework, we present an algorithm where each system alternately estimates its cluster identity and performs an estimation of its dynamics. This is then aggregated to update the model of each cluster. We show that under mild assumptions, our algorithm correctly estimates the cluster identities and achieves an 𝜀-approximate solution with a sample complexity that scales inversely with the number of systems in the cluster, thus facilitating a more efficient and personalized system identification.

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Phenotypic profiling systematically maps and analyzes observable traits (phenotypes) exhibited in cells, tissues, organisms or systems in response to various conditions, including chemical, genetic and disease perturbations. This approach seeks to comprehensively understand the functional consequences of perturbations on biological systems, thereby informing diverse research areas such as drug discovery, disease modeling, functional genomics and systems biology. Corresponding techniques should capture high-dimensional features to distinguish phenotypes affected by different conditions. Current methods mainly include fluorescence imaging, mass spectrometry and omics technologies, coupled with computational analysis, to quantify diverse features such as morphology, metabolism and gene expression in response to perturbations. Yet, they face challenges of high costs, complicated operations and strong batch effects. Vibrational imaging offers an alternative for phenotypic profiling, providing a sensitive, cost-effective and easily operated approach to capture the biochemical fingerprint of phenotypes. Among vibrational imaging techniques, infrared (IR) imaging has further advantages of high throughput, fast imaging speed and full spectrum coverage compared with Raman imaging. However, current biomedical applications of IR imaging mainly concentrate on "digital disease pathology", which uses label-free IR imaging with machine learning for tissue pathology classification and disease diagnosis. The thesis contributes as the first comprehensive study of using IR imaging for phenotypic profiling, focusing on three key areas. First, IR-active vibrational probes are systematically designed to enhance metabolic specificity, thereby enriching measured features and improving sensitivity and specificity for phenotype discrimination. Second, experimental workflows are established for phenotypic profiling using IR imaging across biological samples at various levels, including cellular, tissue and organ, in response to drug and disease perturbations. Lastly, complete data analysis pipelines are developed, including data preprocessing, statistical analysis and machine learning methods, with additional algorithmic developments for analyzing and mapping phenotypes. Chapter 1 lays the groundwork for IR imaging by delving into the theory of IR spectroscopy theory and the instrumentation of IR imaging, establishing a foundation for subsequent studies. Chapter 2 discusses the principles of popular machine learning methods applied in IR imaging, including supervised learning, unsupervised learning and deep learning, providing the algorithmic backbone for later chapters. Additionally, it provides an overview of existing biomedical applications using label-free IR imaging combined with machine learning, facilitating a deeper understanding of the current research landscape and the focal points of IR imaging for traditional biomedical studies. Chapter 3-5 focus on applying IR imaging coupled with machine learning for novel application of phenotypic profiling. Chapter 3 explores the design and development of IR-active vibrational probes for IR imaging. Three types of vibrational probes, including azide, 13C-based probes and deuterium-based probes are introduced to study dynamic metabolic activities of protein, lipids and carbohydrates in cells, small organisms and mice for the first time. The developed probes largely improve the metabolic specificity of IR imaging, enhancing the sensitivity of IR imaging towards different phenotypes. Chapter 4 studies the combination of IR imaging, heavy water labeling and unsupervised learning for tissue metabolic profiling, which provides a novel method to map metabolic tissue atlas in complex mammalian systems. In particular, cell type-, tissue- and organ-specific metabolic profiles are identified with spatial information in situ. In addition, this method further captures metabolic changes during brain development and characterized intratumor metabolic heterogeneity of glioblastoma, showing great promise for disease modeling. Chapter 5 developed Vibrational Painting (VIBRANT), a method using IR imaging, multiplexed vibrational probes and supervised learning for cellular phenotypic profiling of drug perturbations. Three IR-active vibrational probes were designed to measure distinct essential metabolic activities in human cancer cells. More than 20,000 single-cell drug responses were collected, corresponding to 23 drug treatments. Supervised learning is used to accurately predict drug mechanism of action at single-cell level with minimal batch effects. We further designed an algorithm to discover drug candidates with novel mechanisms of action and evaluate drug combinations. Overall, VIBRANT has demonstrated great potential across multiple areas of phenotypic drug screening.

Since its discovery in 1995 resting state functional connectivity derived from functional MRI data has become a popular neuroimaging method for study psychiatric disorders. Current methods for analyzing resting state functional connectivity in disease involve thousands of univariate tests, and the specification of regions of interests to employ in the analysis. There are several drawbacks to these methods. First the mass univariate tests employed are insensitive to the information present in distributed networks of functional connectivity. Second, the null hypothesis testing employed to select functional connectivity dierences between groups does not evaluate the predictive power of identified functional connectivities. Third, the specification of regions of interests is confounded by experimentor bias in terms of which regions should be modeled and experimental error in terms of the size and location of these regions of interests. The objective of this dissertation is to improve the methods for functional connectivity analysis using multivariate predictive modeling, feature selection, and whole brain parcellation. A method of applying Support vector classification (SVC) to resting state functional connectivity data was developed in the context of a neuroimaging study of depression. The interpretability of the obtained classifier was optimized using feature selection techniques that incorporate reliability information. The problem of selecting regions of interests for whole brain functional connectivity analysis was addressed by clustering whole brain functional connectivity data to parcellate the brain into contiguous functionally homogenous regions. This newly developed famework was applied to derive a classifier capable of correctly seperating the functional connectivity patterns of patients with depression from those of healthy controls 90% of the time. The features most relevant to the obtain classifier match those previously identified in previous studies, but also include several regions not previously implicated in the functional networks underlying depression.

Speech communication encompasses diverse types of information, including phonetics, affective state, voice quality, and speaker identity. From a speech production standpoint, the acoustic speech signal can be mainly divided into glottal source and vocal tract components, which play distinct roles in rendering the various types of information it contains. Most deployed speech analysis systems, however, do not explicitly represent these two components as distinct entities, as their joint estimation from the acoustic speech signal becomes an ill-defined blind deconvolution problem. Nevertheless, because of the desire to understand glottal behavior and how it relates to perceived voice quality, there has been continued interest in explicitly estimating the glottal component of the speech signal. To this end, several inverse filtering (IF) algorithms have been proposed, but they are unreliable in practice because of the blind formulation of the separation problem. In an effort to develop a method that can bypass the challenging IF process, this thesis proposes a new glottal source information extraction method that relies on supervised machine learning to transform smoothed spectral representations of speech, which are already used in some of the most widely deployed and successful speech analysis applications, into a set of glottal source features. A transformation method based on Gaussian mixture regression (GMR) is presented and compared to current IF methods in terms of feature similarity, reliability, and speaker discrimination capability on a large speech corpus, and potential representations of the spectral envelope of speech are investigated for their ability represent glottal source variation in a predictable manner. The proposed system was found to produce glottal source features that reasonably matched their IF counterparts in many cases, while being less susceptible to spurious errors. The development of the proposed method entailed a study into the aspects of glottal source information that are already contained within the spectral features commonly used in speech analysis, yielding an objective assessment regarding the expected advantages of explicitly using glottal information extracted from the speech signal via currently available IF methods, versus the alternative of relying on the glottal source information that is implicitly contained in spectral envelope representations.

This dissertation presents the development of a semi-supervised incremental learning framework with a multi-view perspective for image concept modeling. For reliable image concept characterization, having a large number of labeled images is crucial. However, the size of the training set is often limited due to the cost required for generating concept labels associated with objects in a large quantity of images. To address this issue, in this research, we propose to incrementally incorporate unlabeled samples into a learning process to enhance concept models originally learned with a small number of labeled samples. To tackle the sub-optimality problem of conventional techniques, the proposed incremental learning framework selects unlabeled samples based on an expected error reduction function that measures contributions of the unlabeled samples based on their ability to increase the modeling accuracy. To improve the convergence property of the proposed incremental learning framework, we further propose a multi-view learning approach that makes use of multiple features such as color, texture, etc., of images when including unlabeled samples. For robustness to mismatches between training and testing conditions, a discriminative learning algorithm, namely a kernelized maximal- figure-of-merit (kMFoM) learning approach is also developed. Combining individual techniques, we conduct a set of experiments on various image concept modeling problems, such as handwritten digit recognition, object recognition, and image spam detection to highlight the effectiveness of the proposed framework.

The term “Google” has become a verb for most of us. Search engines, however, have certain limitations. For example ask it for the impact of the current global financial crisis in different parts of the world, and you can expect to sift through thousands of results for the answer. This motivates the research in complex question answering where the purpose is to create summaries of large volumes of information as answers to complex questions, rather than simply offering a listing of sources. Unlike simple questions, complex questions cannot be answered easily as they often require inferencing and synthesizing information from multiple documents. Hence, this task is accomplished by the query-focused multidocument summarization systems. In this thesis we apply different supervised learning techniques to confront the complex question answering problem. To run our experiments, we consider the DUC-2007 main task. A huge amount of labeled data is a prerequisite for supervised training. It is expensive and time consuming when humans perform the labeling task manually. Automatic labeling can be a good remedy to this problem. We employ five different automatic annotation techniques to build extracts from human abstracts using ROUGE, Basic Element (BE) overlap, syntactic similarity measure, semantic similarity measure and Extended String Subsequence Kernel (ESSK). The representative supervised methods we use are Support Vector Machines (SVM), Conditional Random Fields (CRF), Hidden Markov Models (HMM) and Maximum Entropy (MaxEnt). We annotate DUC-2006 data and use them to train our systems, whereas 25 topics of DUC-2007 data set are used as test data. The evaluation results reveal the impact of automatic labeling methods on the performance of the supervised approaches to complex question answering. We also experiment with two ensemble-based approaches that show promising results for this problem domain. / x, 108 leaves : ill. ; 29 cm

Orientador: José Mario De Martino / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação / Made available in DSpace on 2018-08-20T14:28:14Z (GMT). No. of bitstreams: 1 Leite_TatianeSilvia_M.pdf: 77678050 bytes, checksum: 402062baa2ae89224527d82c64355abd (MD5) Previous issue date: 2012 / Resumo: O rosto desempenha um papel importante na comunicação e expressão de emoções. Por ser o cartão de visitas individual e caracterizar a primeira impressão de cada um, sua aparência e seu formato tornam-se alvo de diversos estudos. Um rosto mais atraente é capaz de capturar com maior facilidade não apenas a atenção de quem o observa, como também sua empatia. Nesta linha, o presente trabalho tem como objetivo o desenvolvimento de uma metodologia para manipulação e transformação de imagens fotográficas de faces com a finalidade de aumentar a atratividade destes rostos. Para isso, foram abordados dois aspectos de modificação da face: o geométrico e o de textura da pele do rosto. No contexto deste trabalho, foi construída uma base de imagens de faces. Nas imagens desta base foram identificados pontos de interesse e calculadas distâncias entre eles para a caracterização das proporções da face. Adicionalmente, foi atribuído um grau de atratividade para cada face, a partir de avaliação realizada por um grupo de 40 voluntários. As medidas de proporção e atratividade foram utilizadas, no processo de melhoria geométrica da face, como conjunto de treinamento para os algoritmos de aprendizado de máquina. Como resultado do processamento são geradas novas medidas para o rosto que se deseja tornar mais atraente. Utilizando a técnica de warping, a imagem do rosto de entrada é modificada para as novas medidas encontradas. A imagem resultante deste processo serve como imagem de entrada para o processo de modificação da textura. Neste processamento é gerada uma nova imagem com a cor dos pixels da região de pele do rosto alterada. A principal contribuição deste trabalho consiste em unir o processo de modificação geométrica do rosto à modificação de textura da pele. Esta união resultou em um ganho de atratividade maior do que se estas técnicas fossem utilizadas separadamente. Este ganho foi comprovado com testes de pós-avaliação realizados com voluntários analisando os resultados finais nas imagens / Abstract: The face plays an important role in communication and expression of emotions. Face characterizes the first impression of each person; thus, its appearance and shape became the target of several studies. An attractive face is capable of capturing more easily not only the attention of the beholder, as well as his/her empathy. In this vein, this study aims to develop a methodology for handling and processing of images of faces in order to increase the attractiveness of these faces. It was addressed two aspects of modification of the face: the geometric and texture (considering only the skin of the face). In this work, a large database of face images was built. All these faces were marked with feature points and from them it was taken measures considered interesting to analyze the dimensions and proportions of the faces. Besides that, they were also evaluated according to their degree of attraction by a group of volunteers. This information was used in the enhancement of the face geometry, using machine learning algorithms. At this stage new measures were generated for the input face which is considered in the beautification process. Using the technique of warping, the input face image is warped to fit the new measures found by the algorithms. The resulting image from this process serves as the input image to the process of texture modification. At this stage it is generated a new image with the color of pixels in the region of skin of the face changed. The main contribution of this work is to join the process of face geometry modification with the process of face skin texture modification. The result of this union generates image faces which have greater enhancement of attractiveness than if the processes were used separately. This gain was confirmed by post-evaluation tests conducted with volunteers that analyzed the final results / Mestrado / Engenharia de Computação / Mestre em Engenharia Elétrica

Data-efficient learning is crucial for building language models that can adapt to a wide variety of tasks with minimal annotations of labeled examples. Recently, the advent of large language models (LLMs) has given rise to a new ability called in-context learning (ICL), where LLMs can learn and perform a new task via inference on a prompt that consists of a few input-output pairs, all while keeping their parameters frozen. While ICL excels on academic benchmarks, it faces several challenges in real-world deployment, including sensitivity to prompt artifacts, poor calibration of model confidence, and inefficiency due to large model sizes. We conduct a systematic study of ICL sensitivity and find a negative correlation between ICL sensitivity and accuracy. To improve ICL calibration, we propose a sensitivity-based method that assigns the negative value of sensitivity as a confidence score, and demonstrate that our approach outperforms baselines in selective prediction tasks. Additionally, we propose to enhancing the efficiency of ICL through a new method called in-context tuning, which involves fine-tuning small language models on ICL prompts. We further augment the ICL capabilities of small LMs by incorporating distillation from larger LLMs into the in-context tuning process. Besides proposing new strategies to improve the reliability, accuracy, and efficiency of ICL, we also present a study on understanding how ICL emerges. The emergence of ICL is mysterious, as ICL prompts consisting of input-output concatenations are rare in natural text, yet pre-training on natural text alone is sufficient for ICL to emerge. We identify a structure called parallel structures, which capture pairs of phrases sampled from the same distribution, and verify through ablation experiments that these structures are a major source of ICL. Finally, we investigate the effectiveness of LLMs in explaining themselves when prompted with ICL demonstration examples. We propose a new metric called counterfactual simulatability, which measures whether humans can use LLM-generated explanations to construct precise and generalized mental models of the LLMs. Our results demonstrate that LLMs’ capacity to provide faithful explanations is significantly lower than that of humans, even with ICL examples. To address this, we propose explanation-precision fine-tuning, which uses data augmentation to generate synthetic fine-tuning data with explanations that are consistent with answers on relevant inputs. Our contributions advance the accuracy, reliability, efficiency and understanding of ICL of LLMs, offering methods to mitigate sensitivity, improve calibration, enhance efficiency, and strengthen the self-explaining power of LLMs. This work paves the way for more data-efficient, reliable and explainable language models for diverse real-world applications.