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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.
61

Prediction games : machine learning in the presence of an adversary

Brückner, Michael January 2012 (has links)
In many applications one is faced with the problem of inferring some functional relation between input and output variables from given data. Consider, for instance, the task of email spam filtering where one seeks to find a model which automatically assigns new, previously unseen emails to class spam or non-spam. Building such a predictive model based on observed training inputs (e.g., emails) with corresponding outputs (e.g., spam labels) is a major goal of machine learning. Many learning methods assume that these training data are governed by the same distribution as the test data which the predictive model will be exposed to at application time. That assumption is violated when the test data are generated in response to the presence of a predictive model. This becomes apparent, for instance, in the above example of email spam filtering. Here, email service providers employ spam filters and spam senders engineer campaign templates such as to achieve a high rate of successful deliveries despite any filters. Most of the existing work casts such situations as learning robust models which are unsusceptible against small changes of the data generation process. The models are constructed under the worst-case assumption that these changes are performed such to produce the highest possible adverse effect on the performance of the predictive model. However, this approach is not capable to realistically model the true dependency between the model-building process and the process of generating future data. We therefore establish the concept of prediction games: We model the interaction between a learner, who builds the predictive model, and a data generator, who controls the process of data generation, as an one-shot game. The game-theoretic framework enables us to explicitly model the players' interests, their possible actions, their level of knowledge about each other, and the order at which they decide for an action. We model the players' interests as minimizing their own cost function which both depend on both players' actions. The learner's action is to choose the model parameters and the data generator's action is to perturbate the training data which reflects the modification of the data generation process with respect to the past data. We extensively study three instances of prediction games which differ regarding the order in which the players decide for their action. We first assume that both player choose their actions simultaneously, that is, without the knowledge of their opponent's decision. We identify conditions under which this Nash prediction game has a meaningful solution, that is, a unique Nash equilibrium, and derive algorithms that find the equilibrial prediction model. As a second case, we consider a data generator who is potentially fully informed about the move of the learner. This setting establishes a Stackelberg competition. We derive a relaxed optimization criterion to determine the solution of this game and show that this Stackelberg prediction game generalizes existing prediction models. Finally, we study the setting where the learner observes the data generator's action, that is, the (unlabeled) test data, before building the predictive model. As the test data and the training data may be governed by differing probability distributions, this scenario reduces to learning under covariate shift. We derive a new integrated as well as a two-stage method to account for this data set shift. In case studies on email spam filtering we empirically explore properties of all derived models as well as several existing baseline methods. We show that spam filters resulting from the Nash prediction game as well as the Stackelberg prediction game in the majority of cases outperform other existing baseline methods. / Eine der Aufgabenstellungen des Maschinellen Lernens ist die Konstruktion von Vorhersagemodellen basierend auf gegebenen Trainingsdaten. Ein solches Modell beschreibt den Zusammenhang zwischen einem Eingabedatum, wie beispielsweise einer E-Mail, und einer Zielgröße; zum Beispiel, ob die E-Mail durch den Empfänger als erwünscht oder unerwünscht empfunden wird. Dabei ist entscheidend, dass ein gelerntes Vorhersagemodell auch die Zielgrößen zuvor unbeobachteter Testdaten korrekt vorhersagt. Die Mehrzahl existierender Lernverfahren wurde unter der Annahme entwickelt, dass Trainings- und Testdaten derselben Wahrscheinlichkeitsverteilung unterliegen. Insbesondere in Fällen in welchen zukünftige Daten von der Wahl des Vorhersagemodells abhängen, ist diese Annahme jedoch verletzt. Ein Beispiel hierfür ist das automatische Filtern von Spam-E-Mails durch E-Mail-Anbieter. Diese konstruieren Spam-Filter basierend auf zuvor empfangenen E-Mails. Die Spam-Sender verändern daraufhin den Inhalt und die Gestaltung der zukünftigen Spam-E-Mails mit dem Ziel, dass diese durch die Filter möglichst nicht erkannt werden. Bisherige Arbeiten zu diesem Thema beschränken sich auf das Lernen robuster Vorhersagemodelle welche unempfindlich gegenüber geringen Veränderungen des datengenerierenden Prozesses sind. Die Modelle werden dabei unter der Worst-Case-Annahme konstruiert, dass diese Veränderungen einen maximal negativen Effekt auf die Vorhersagequalität des Modells haben. Diese Modellierung beschreibt die tatsächliche Wechselwirkung zwischen der Modellbildung und der Generierung zukünftiger Daten nur ungenügend. Aus diesem Grund führen wir in dieser Arbeit das Konzept der Prädiktionsspiele ein. Die Modellbildung wird dabei als mathematisches Spiel zwischen einer lernenden und einer datengenerierenden Instanz beschrieben. Die spieltheoretische Modellierung ermöglicht es uns, die Interaktion der beiden Parteien exakt zu beschreiben. Dies umfasst die jeweils verfolgten Ziele, ihre Handlungsmöglichkeiten, ihr Wissen übereinander und die zeitliche Reihenfolge, in der sie agieren. Insbesondere die Reihenfolge der Spielzüge hat einen entscheidenden Einfluss auf die spieltheoretisch optimale Lösung. Wir betrachten zunächst den Fall gleichzeitig agierender Spieler, in welchem sowohl der Lerner als auch der Datengenerierer keine Kenntnis über die Aktion des jeweils anderen Spielers haben. Wir leiten hinreichende Bedingungen her, unter welchen dieses Spiel eine Lösung in Form eines eindeutigen Nash-Gleichgewichts besitzt. Im Anschluss diskutieren wir zwei verschiedene Verfahren zur effizienten Berechnung dieses Gleichgewichts. Als zweites betrachten wir den Fall eines Stackelberg-Duopols. In diesem Prädiktionsspiel wählt der Lerner zunächst das Vorhersagemodell, woraufhin der Datengenerierer in voller Kenntnis des Modells reagiert. Wir leiten ein relaxiertes Optimierungsproblem zur Bestimmung des Stackelberg-Gleichgewichts her und stellen ein mögliches Lösungsverfahren vor. Darüber hinaus diskutieren wir, inwieweit das Stackelberg-Modell bestehende robuste Lernverfahren verallgemeinert. Abschließend untersuchen wir einen Lerner, der auf die Aktion des Datengenerierers, d.h. der Wahl der Testdaten, reagiert. In diesem Fall sind die Testdaten dem Lerner zum Zeitpunkt der Modellbildung bekannt und können in den Lernprozess einfließen. Allerdings unterliegen die Trainings- und Testdaten nicht notwendigerweise der gleichen Verteilung. Wir leiten daher ein neues integriertes sowie ein zweistufiges Lernverfahren her, welche diese Verteilungsverschiebung bei der Modellbildung berücksichtigen. In mehreren Fallstudien zur Klassifikation von Spam-E-Mails untersuchen wir alle hergeleiteten, sowie existierende Verfahren empirisch. Wir zeigen, dass die hergeleiteten spieltheoretisch-motivierten Lernverfahren in Summe signifikant bessere Spam-Filter erzeugen als alle betrachteten Referenzverfahren.
62

Incremental Learning of Deep Convolutional Neural Networks for Tumour Classification in Pathology Images

Johansson, Philip January 2019 (has links)
Medical doctors understaffing is becoming a compelling problem in many healthcare systems. This problem can be alleviated by utilising Computer-Aided Diagnosis (CAD) systems to substitute doctors in different tasks, for instance, histopa-thological image classification. The recent surge of deep learning has allowed CAD systems to perform this task at a very competitive performance. However, a major challenge with this task is the need to periodically update the models with new data and/or new classes or diseases. These periodical updates will result in catastrophic forgetting, as Convolutional Neural Networks typically requires the entire data set beforehand and tend to lose knowledge about old data when trained on new data. Incremental learning methods were proposed to alleviate this problem with deep learning. In this thesis, two incremental learning methods, Learning without Forgetting (LwF) and a generative rehearsal-based method, are investigated. They are evaluated on two criteria: The first, capability of incrementally adding new classes to a pre-trained model, and the second is the ability to update the current model with an new unbalanced data set. Experiments shows that LwF does not retain knowledge properly for the two cases. Further experiments are needed to draw any definite conclusions, for instance using another training approach for the classes and try different combinations of losses. On the other hand, the generative rehearsal-based method tends to work for one class, showing a good potential to work if better quality images were generated. Additional experiments are also required in order to investigating new architectures and approaches for a more stable training.
63

Generative adversarial networks for single image super resolution in microscopy images

Gawande, Saurabh January 2018 (has links)
Image Super resolution is a widely-studied problem in computer vision, where the objective is to convert a lowresolution image to a high resolution image. Conventional methods for achieving super-resolution such as image priors, interpolation, sparse coding require a lot of pre/post processing and optimization. Recently, deep learning methods such as convolutional neural networks and generative adversarial networks are being used to perform super-resolution with results competitive to the state of the art but none of them have been used on microscopy images. In this thesis, a generative adversarial network, mSRGAN, is proposed for super resolution with a perceptual loss function consisting of a adversarial loss, mean squared error and content loss. The objective of our implementation is to learn an end to end mapping between the low / high resolution images and optimize the upscaled image for quantitative metrics as well as perceptual quality. We then compare our results with the current state of the art methods in super resolution, conduct a proof of concept segmentation study to show that super resolved images can be used as a effective pre processing step before segmentation and validate the findings statistically. / Image Super-resolution är ett allmänt studerad problem i datasyn, där målet är att konvertera en lågupplösningsbild till en högupplöst bild. Konventionella metoder för att uppnå superupplösning som image priors, interpolation, sparse coding behöver mycket föroch efterbehandling och optimering.Nyligen djupa inlärningsmetoder som convolutional neurala nätverk och generativa adversariella nätverk är användas för att utföra superupplösning med resultat som är konkurrenskraftiga mot toppmoderna teknik, men ingen av dem har använts på mikroskopibilder. I denna avhandling, ett generativ kontradiktorisktsnätverk, mSRGAN, är föreslås för superupplösning med en perceptuell förlustfunktion bestående av en motsatt förlust, medelkvadratfel och innehållförlust.Mål med vår implementering är att lära oss ett slut på att slut kartläggning mellan bilder med låg / hög upplösning och optimera den uppskalade bilden för kvantitativa metriks såväl som perceptuell kvalitet. Vi jämför sedan våra resultat med de nuvarande toppmoderna metoderna i superupplösning, och uppträdande ett bevis på konceptsegmenteringsstudie för att visa att superlösa bilder kan användas som ett effektivt förbehandling steg före segmentering och validera fynden statistiskt.
64

Deep Learning-based Regularizers for Cone Beam Computed Tomography Reconstruction / Djupinlärningsbaserade regulariserare för rekonstruktion inom volymtomografi

Syed, Sabina, Stenberg, Josefin January 2023 (has links)
Cone Beam Computed Tomography is a technology to visualize the 3D interior anatomy of a patient. It is important for image-guided radiation therapy in cancer treatment. During a scan, iterative methods are often used for the image reconstruction step. A key challenge is the ill-posedness of the resulting inversion problem, causing the images to become noisy. To combat this, regularizers can be introduced, which help stabilize the problem. This thesis focuses on Adversarial Convex Regularization that with deep learning regularize the scans according to a target image quality. It can be interpreted in a Bayesian setting by letting the regularizer be the prior, approximating the likelihood with the measurement error, and obtaining the patient image through the maximum-a-posteriori estimate. Adversarial Convex Regularization has previously shown promising results in regular Computed Tomography, and this study aims to investigate its potential in Cone Beam Computed Tomography.  Three different learned regularization methods have been developed, all based on Convolutional Neural Network architectures. One model is based on three-dimensional convolutional layers, while the remaining two rely on 2D layers. These two are in a later stage crafted to be applicable to 3D reconstruction by either stacking a 2D model or by averaging 2D models trained in three orthogonal planes. All neural networks are trained on simulated male pelvis data provided by Elekta. The 3D convolutional neural network model has proven to be heavily memory-consuming, while not performing better than current reconstruction methods with respect to image quality. The two architectures based on merging multiple 2D neural network gradients for 3D reconstruction are novel contributions that avoid memory issues. These two models outperform current methods in terms of multiple image quality metrics, such as Peak Signal-to-Noise Ratio and Structural Similarity Index Measure, and they also generalize well for real Cone Beam Computed Tomography data. Additionally, the architecture based on a weighted average of 2D neural networks is able to capture spatial interactions to a larger extent and is adjustable to favor the plane that best shows the field of interest, a possibly desirable feature in medical practice. / Volymtomografi kan användas inom cancerbehandling för att skapa bilder av patientens inre anatomi i 3D som sedan används vid stråldosplanering. Under den rekonstruerande fasen i en skanning används ofta iterativa metoder. En utmaning är att det resulterande inversionsproblemet är illa ställt, vilket leder till att bilderna blir brusiga. För att motverka detta kan regularisering introduceras som bidrar till att stabilisera problemet. Fokus för denna uppsats är Adversarial Convex Regularization som baserat på djupinlärning regulariserar bilderna enligt en målbildskvalitet. Detta kan även tolkas ur ett Bayesianskt perspektiv genom att betrakta regulariseraren som apriorifördelningen, approximera likelihoodfördelningen med mätfelet samt erhålla patientbilden genom maximum-a-posteriori-skattningen. Adversarial Convex Regularization har tidigare visat lovande resultat för data från Datortomografi och syftet med denna uppsats är att undersöka dess potential för Volymtomografi.  Tre olika inlärda regulariseringsmetoder har utvecklats med hjälp av faltningsnätverk. En av modellerna bygger på faltning av tredimensionella lager, medan de återstående två är baserade på 2D-lager. Dessa två sammanförs i ett senare skede för att kunna appliceras vid 3D-rekonstruktion, antingen genom att stapla 2D modeller eller genom att beräkna ett viktat medelvärde av tre 2D-modeller som tränats i tre ortogonala plan. Samtliga modeller är tränade på simulerad manlig bäckendata från Elekta. 3D-faltningsnätverket har visat sig vara minneskrävande samtidigt som det inte presterar bättre än nuvarande rekonstruktionsmetoder med avseende på bildkvalitet. De andra två metoderna som bygger på att stapla flera gradienter av 2D-nätverk vid 3D-rekonstruktion är ett nytt vetenskapligt bidrag och undviker minnesproblemen. Dessa två modeller överträffar nuvarande metoder gällande flera bildkvalitetsmått och generaliserar även väl för data från verklig Volymtomografi. Dessutom lyckas modellen som bygger på ett viktat medelvärde av 2D-nätverk i större utsträckning fånga spatiala interaktioner. Den kan även anpassas till att gynna det plan som bäst visar intresseområdet i kroppen, vilket möjligtvis är en önskvärd egenskap i medicinska sammanhang.
65

SELF-SUPERVISED ONE-SHOT LEARNING FOR AUTOMATIC SEGMENTATION OF GAN-GENERATED IMAGES

Ankit V Manerikar (16523988) 11 July 2023 (has links)
<p>Generative Adversarial Networks (GANs) have consistently defined the state-of-the-art in the generative modelling of high-quality images in several applications.  The images generated using GANs, however, do not lend themselves to being directly used in supervised learning tasks without first being curated through annotations.  This dissertation investigates how to carry out automatic on-the-fly segmentation of GAN-generated images and how this can be applied to the problem of producing high-quality simulated data for X-ray based security screening.  The research exploits the hidden layer properties of GAN models in a self-supervised learning framework for the automatic one-shot segmentation of images created by a style-based GAN.  The framework consists of a novel contrastive learner that is based on a Sinkhorn distance-based clustering algorithm and that learns a compact feature space for per-pixel classification of the GAN-generated images.  This facilitates faster learning of the feature vectors for one-shot segmentation and allows on-the-fly automatic annotation of the GAN images.  We have tested our framework on a number of standard benchmarks (CelebA, PASCAL, LSUN) to yield a segmentation performance that not only exceeds the semi-supervised baselines by an average wIoU margin of 1.02 % but also improves the inference speeds by a factor of 4.5.  This dissertation also presents BagGAN, an extension of our framework to the problem domain of X-ray based baggage screening.  BagGAN produces annotated synthetic baggage X-ray scans to train machine-learning algorithms for the detection of prohibited items during security screening.  We have compared the images generated by BagGAN with those created by deterministic ray-tracing models for X-ray simulation and have observed that our GAN-based baggage simulator yields a significantly improved performance in terms of image fidelity and diversity.  The BagGAN framework is also tested on the PIDRay and other baggage screening benchmarks to produce segmentation results comparable to their respective baseline segmenters based on manual annotations.</p>
66

Time-series Generative Adversarial Networks for Telecommunications Data Augmentation

Dimyati, Hamid January 2021 (has links)
Time- series Generative Adversarial Networks (TimeGAN) is proposed to overcome the GAN model’s insufficiency in producing synthetic samples that inherit the predictive ability of the original timeseries data. TimeGAN combines the unsupervised adversarial loss in the GAN framework with a supervised loss adopted from an autoregressive model. However, TimeGAN is like another GANbased model that only learns from the set of smaller sequences extracted from the original time-series. This behavior yields a severe consequence when encountering data augmentation for time-series with multiple seasonal patterns, as found in the mobile telecommunication network data. This study examined the effectiveness of the TimeGAN model with the help of Dynamic Time Warping (DTW) and different types of RNN as its architecture to produce synthetic mobile telecommunication network data, which can be utilized to improve the forecasting performance of the statistical and deep learning models relative to the baseline models trained only on the original data. The experiment results indicate that DTW helps TimeGAN maintaining the multiple seasonal attributes. In addition, either LSTM or Bidirectional LSTM as TimeGAN architecture ensures the model is robust to mode collapse problem and creates synthetic data that are diversified and indistinguishable from the original time-series. Finally, merging both original and synthetic time-series becomes a compelling way to significantly improve the deep learning model’s forecasting performance but fails to do so for the statistical model. / Time-series Generative Adversarial Networks (TimeGAN) föreslås för att övervinna GAN-modellens brist att kunna producera syntetisk data som ärver de prediktiva förmåga från den ursprungliga tidsseriedatan. TimeGAN kombinerar den icke-vägledande förlusten i GAN-ramverket tillsammans med den vägledande förlusten från en autoregressiv modell. TimeGAN liknar en vanlig GAN-baserad modell, men behöver bara en mindre uppsättning sekvenser från den ursprungliga tidsserien för att lära sig. Denna egenskap kan dock leda till allvarliga konsekvenser när man stöter på dataförstoring för tidsserier med flera säsongsmönster, vilket återfinns i mobilnätverksdata. Denna studie har undersökt effektiviteten av TimeGAN-modellen med hjälp av Dynamic Time Warping (DTW) och olika typer av RNN som dess arkitektur för att producera syntetisk mobilnätverksdata. Detta kan användas för att förbättra statistiska och djupinlärningsmodellers prognostisering relativt till modeller som bara har tränat på orginaldata. De experimentella resultaten indikerar att DTW hjälper TimeGAN att bibehålla de olika säsongsattributen. Dessutom, TimeGAN med antingen LSTM eller Bidirectional LSTM som arkitektur säkerställer att modellen är robust för lägesfallsproblem och skapar syntetisk data som är diversifierade och inte kan urskiljas från den ursprungliga tidsserien. Slutligen, en sammanslagning av både ursprungliga och syntetiska tidsserier blir ett övertygande sätt att avsevärt förbättra djupinlärningsmodellens prestanda men misslyckas med detta för den statistiska modellen.
67

Deep Reinforcement Learning for Temperature Control in Buildings and Adversarial Attacks

Ammouri, Kevin January 2021 (has links)
Heating, Ventilation and Air Conditioning (HVAC) systems in buildings are energy consuming and traditional methods used for building control results in energy losses. The methods cannot account for non-linear dependencies in the thermal behaviour. Deep Reinforcement Learning (DRL) is a powerful method for reaching optimal control in many different control environments. DRL utilizes neural networks to approximate the optimal actions to take given that the system is in a given state. Therefore, DRL is a promising method for building control and this fact is highlighted by several studies. However, neural network polices are known to be vulnerable to adversarial attacks, which are small, indistinguishable changes to the input, which make the network choose a sub-optimal action. Two of the main approaches to attack DRL policies are: (1) the Fast Gradient Sign Method, which uses the gradients of the control agent’s network to conduct the attack; (2) to train a a DRL-agent with the goal to minimize performance of control agents. The aim of this thesis is to investigate different strategies for solving the building control problem with DRL using the building simulator IDA ICE. This thesis is also going to use the concept of adversarial machine learning by applying the attacks on the agents controlling the temperature inside the building. We first built a DRL architecture to learn how to efficiently control temperature in a building. Experiments demonstrate that exploration of the agent plays a crucial role in the training of the building control agent, and one needs to fine-tune the exploration strategy in order to achieve satisfactory performance. Finally, we tested the susceptibility of the trained DRL controllers to adversarial attacks. These tests showed, on average, that attacks trained using DRL methods have a larger impact on building control than those using FGSM, while random perturbation have almost null impact. / Ventilationssystem i byggnader är energiförbrukande och traditionella metoder som används för byggnadskontroll resulterar i förlust av energisparande. Dessa metoder kan inte ta hänsyn till icke-linjära beroenden i termisk beteenden. Djup förstärkande inlärning (DRL) är en kraftfull metod för att uppnå optimal kontroll i många kontrollmiljöer. DRL använder sig av neurala nätverk för att approximera optimala val som kan tas givet att systemet befinner sig i en viss stadie. Därför är DRL en lovande metod för byggnadskontroll och detta faktumet är markerat av flera studier. Likväl, neurala nätverk i allmänhet är kända för att vara svaga mot adversarial attacker, vilket är små ändringar i inmatningen, som gör att neurala nätverket väljer en åtgärd som är suboptimal. Syftet med denna anvhandling är att undersöka olika strategier för att lösa byggnadskontroll-problemet med DRL genom att använda sig av byggnadssimulatorn IDA ICE. Denna avhandling kommer också att använda konceptet av adversarial machine learning för att attackera agenterna som kontrollerar temperaturen i byggnaden. Det finns två olika sätt att attackera neurala nätverk: (1) Fast Gradient Sign Method, som använder gradienterna av kontrollagentens nätverk för att utföra sin attack; (2) träna en inlärningsagent med DRL med målet att minimera kontrollagenternas prestanda. Först byggde vi en DRL-arkitektur som lärde sig kontrollera temperaturen i en byggad. Experimenten visar att utforskning av agenten är en grundläggande faktor för träningen av kontrollagenten och man måste finjustera utforskningen av agenten för att nå tillfredsställande prestanda. Slutligen testade vi känsligheten av de tränade DRL-agenterna till adversarial attacker. Dessa test visade att i genomsnitt har det större påverkan på kontrollagenterna att använda DRL metoder än att använda sig av FGSM medans att attackera helt slumpmässigt har nästan ingen påverkan.
68

Trojan Attacks and Defenses on Deep Neural Networks

Yingqi Liu (13943811) 13 October 2022 (has links)
<p>With the fast spread of machine learning techniques, sharing and adopting public deep neural networks become very popular. As deep neural networks are not intuitive for human to understand, malicious behaviors can be injected into deep neural networks undetected. We call it trojan attack or backdoor attack on neural networks. Trojaned models operate normally when regular inputs are provided, and misclassify to a specific output label when the input is stamped with some special pattern called trojan trigger. Deploying trojaned models can cause various severe consequences including endangering human lives (in applications like autonomous driving). Trojan attacks on deep neural networks introduce two challenges. From the attacker's perspective, since the training data or training process is usually not accessible to the attacker, the attacker needs to find a way to carry out the trojan attack without access to training data. From the user's perspective, the user needs to quickly scan the online public deep neural networks and detect trojaned models.</p> <p>We try to address these challenges in this dissertation. For trojan attack without access to training data, We propose to invert the neural network to generate a general trojan trigger, and then retrain the model with reverse-engineered training data to inject malicious behaviors to the model. The malicious behaviors are only activated by inputs stamped with the trojan trigger. To scan and detect trojaned models, we develop a novel technique that analyzes inner neuron behaviors by determining how output activation change when we introduce different levels of stimulation to a neuron. A trojan trigger is then reverse-engineered through an optimization procedure using the stimulation analysis results, to confirm that a neuron is truly compromised. Furthermore, for complex trojan attacks, we propose a novel complex trigger detection method. It leverages a novel symmetric feature differencing method to distinguish features of injected complex triggers from natural features. For trojan attacks on NLP models, we propose a novel backdoor scanning technique. It transforms a subject model to an equivalent but differentiable form. It then inverts a distribution of words denoting their likelihood in the trigger and applies a novel word discriminativity analysis to determine if the subject model is particularly discriminative for the presence of likely trigger words.</p>
69

Kooperativní hledání cest s protivníkem / Kooperativní hledání cest s protivníkem

Ivanová, Marika January 2014 (has links)
Presented master thesis defines and investigates Adversarial Cooperative Path-finding problem (ACPF), a generalization of standard Cooperative Path-finding. In addition to the Cooperative path- finding where non-colliding paths for multiple agents connecting their initial positions and destinations are searched, consideration of agents controlled by the adversary is included in ACPF. This work is focused on both theoretical properties and practical solving techniques of the considered problem. ACPF is introduced formally using terms from graph theory. We study computational complexity of the problem where we show that the problem is PSPACE-hard and belongs to EXPTIME complexity class. We introduce and discuss possible methods suitable for practical solving of the problem. Considered solving approaches include greedy algorithms, minimax methods, Monte Carlo Tree Search and adaptation of algorithm for the cooperative version of the problem. Surprisingly frequent success rate of greedy methods and rather weaker results of Monte Carlo Tree Search are indicated by the conducted experimental evaluation. Powered by TCPDF (www.tcpdf.org)
70

Zásada kontradiktornosti a její uplatnění v trestním řízení / The principle of Contradictority and Its Application in Criminal Proceedings

Zukalová, Jana January 2016 (has links)
The purpose of my thesis is to provide an analysis of the principle of contradictority and its application in criminal proceedings. I have decided to use the term "contradictory proceedings" even though The European Court of Human Rights that developed the concept usually uses the term "adversarial proceedings". The reason consists in the difference between adversarial proceedings as a special kind of criminal proceedings which is typical for countries within the Anglo-American legal culture and adversarial/contradictory proceedings as a wider concept of proceedings which is based on a respect for the rights of people charged with criminal offences and which can be (and actually is) used both within the Anglo-American legal system and the legal system of the countries in the continental Europe. In this sense, the correct translation into Czech language is "kontradiktorní řízení". The thesis is composed of six basic chapters. Chapters One and Two provide introduction, presenting some theoretical approaches to what contradictory proceedings could or should be. Chapter Three is subdivided into three subchapters. First two of them examine the evolution of adversarial and inquisitorial models of criminal proceedings, dealing with their similarities and differences. The third one summarizes why both of...

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