743 research outputs found
A hybrid algorithm for Bayesian network structure learning with application to multi-label learning
We present a novel hybrid algorithm for Bayesian network structure learning,
called H2PC. It first reconstructs the skeleton of a Bayesian network and then
performs a Bayesian-scoring greedy hill-climbing search to orient the edges.
The algorithm is based on divide-and-conquer constraint-based subroutines to
learn the local structure around a target variable. We conduct two series of
experimental comparisons of H2PC against Max-Min Hill-Climbing (MMHC), which is
currently the most powerful state-of-the-art algorithm for Bayesian network
structure learning. First, we use eight well-known Bayesian network benchmarks
with various data sizes to assess the quality of the learned structure returned
by the algorithms. Our extensive experiments show that H2PC outperforms MMHC in
terms of goodness of fit to new data and quality of the network structure with
respect to the true dependence structure of the data. Second, we investigate
H2PC's ability to solve the multi-label learning problem. We provide
theoretical results to characterize and identify graphically the so-called
minimal label powersets that appear as irreducible factors in the joint
distribution under the faithfulness condition. The multi-label learning problem
is then decomposed into a series of multi-class classification problems, where
each multi-class variable encodes a label powerset. H2PC is shown to compare
favorably to MMHC in terms of global classification accuracy over ten
multi-label data sets covering different application domains. Overall, our
experiments support the conclusions that local structural learning with H2PC in
the form of local neighborhood induction is a theoretically well-motivated and
empirically effective learning framework that is well suited to multi-label
learning. The source code (in R) of H2PC as well as all data sets used for the
empirical tests are publicly available.Comment: arXiv admin note: text overlap with arXiv:1101.5184 by other author
Multiple Action Recognition for Video Games (MARViG)
Action recognition research historically has focused on increasing accuracy on datasets in
highly controlled environments. Perfect or near perfect offline action recognition
accuracy on scripted datasets has been achieved. The aim of this thesis is to deal with the
more complex problem of online action recognition with low latency in real world
scenarios. To fulfil this aim two new multi-modal gaming datasets were captured and
three novel algorithms for online action recognition were proposed.
Two new gaming datasets, G3D and G3Di for real-time action recognition with multiple
actions and multi-modal data were captured and publicly released. Furthermore, G3Di
was captured using a novel game-sourcing method so the actions are realistic. Three novel
algorithms for online action recognition with low latency were proposed. Firstly,
Dynamic Feature Selection, which combines the discriminative power of Random Forests
for feature selection with an ensemble of AdaBoost classifiers for dynamic classification.
Secondly, Clustered Spatio-Temporal Manifolds, which modelled the dynamics of human
actions with style invariant action templates that were combined with Dynamic Time
Warping for execution rate invariance. Finally, a Hierarchical Transfer Learning
framework, comprised of a novel transfer learning algorithm to detect compound actions
in addition to hierarchical interaction detection to recognise the actions and interactions
of multiple subjects.
The proposed algorithms run in real-time with low latency ensuring they are suitable for
a wide range of natural user interface applications including gaming. State-of-the art
results were achieved for online action recognition. Experimental results indicate higher
complexity of the G3Di dataset in comparison to the existing gaming datasets,
highlighting the importance of this dataset for designing algorithms suitable for realistic
interactive applications. This thesis has advanced the study of realistic action recognition
and is expected to serve as a basis for further study within the research community
Review of Non-Technical Losses Identification Techniques
Illegally consumption of electric power, termed as non-technical losses for the distribution companies is one of the dominant factors all over the world for many years. Although there are some conventional methods to identify these irregularities, such as physical inspection of meters at the consumer premises etc, but it requires large number of manpower and time; then also it does not seem to be adequate. Now a days there are various methods and algorithms have been developed that are proposed in different research papers, to detect non-technical losses. In this paper these methods are reviewed, their important features are highlighted and also the limitations are identified. Finally, the qualitative comparison of various non-technical losses identification algorithms is presented based on their performance, costs, data handling, quality control and execution times. It can be concluded that the graph-based classifier, Optimum-Path Forest algorithm that have both supervised and unsupervised variants, yields the most accurate result to detect non-technical losses
From Intrusion Detection to Attacker Attribution: A Comprehensive Survey of Unsupervised Methods
Over the last five years there has been an increase in the frequency and diversity of network attacks. This holds true, as more and more organisations admit compromises on a daily basis. Many misuse and anomaly based Intrusion Detection Systems (IDSs) that rely on either signatures, supervised or statistical methods have been proposed in the literature, but their trustworthiness is debatable. Moreover, as this work uncovers, the current IDSs are based on obsolete attack classes that do not reflect the current attack trends. For these reasons, this paper provides a comprehensive overview of unsupervised and hybrid methods for intrusion detection, discussing their potential in the domain. We also present and highlight the importance of feature engineering techniques that have been proposed for intrusion detection. Furthermore, we discuss that current IDSs should evolve from simple detection to correlation and attribution. We descant how IDS data could be used to reconstruct and correlate attacks to identify attackers, with the use of advanced data analytics techniques. Finally, we argue how the present IDS attack classes can be extended to match the modern attacks and propose three new classes regarding the outgoing network communicatio
Performance Evaluation of Network Anomaly Detection Systems
Nowadays, there is a huge and growing concern about security in information and communication
technology (ICT) among the scientific community because any attack or anomaly in
the network can greatly affect many domains such as national security, private data storage,
social welfare, economic issues, and so on. Therefore, the anomaly detection domain is a broad
research area, and many different techniques and approaches for this purpose have emerged
through the years.
Attacks, problems, and internal failures when not detected early may badly harm an
entire Network system. Thus, this thesis presents an autonomous profile-based anomaly detection
system based on the statistical method Principal Component Analysis (PCADS-AD). This
approach creates a network profile called Digital Signature of Network Segment using Flow Analysis
(DSNSF) that denotes the predicted normal behavior of a network traffic activity through
historical data analysis. That digital signature is used as a threshold for volume anomaly detection
to detect disparities in the normal traffic trend. The proposed system uses seven traffic flow
attributes: Bits, Packets and Number of Flows to detect problems, and Source and Destination IP
addresses and Ports, to provides the network administrator necessary information to solve them.
Via evaluation techniques, addition of a different anomaly detection approach, and
comparisons to other methods performed in this thesis using real network traffic data, results
showed good traffic prediction by the DSNSF and encouraging false alarm generation and detection
accuracy on the detection schema.
The observed results seek to contribute to the advance of the state of the art in methods
and strategies for anomaly detection that aim to surpass some challenges that emerge from
the constant growth in complexity, speed and size of today’s large scale networks, also providing
high-value results for a better detection in real time.Atualmente, existe uma enorme e crescente preocupação com segurança em tecnologia
da informação e comunicação (TIC) entre a comunidade cientÃfica. Isto porque qualquer
ataque ou anomalia na rede pode afetar a qualidade, interoperabilidade, disponibilidade, e integridade
em muitos domÃnios, como segurança nacional, armazenamento de dados privados,
bem-estar social, questões econômicas, e assim por diante. Portanto, a deteção de anomalias
é uma ampla área de pesquisa, e muitas técnicas e abordagens diferentes para esse propósito
surgiram ao longo dos anos.
Ataques, problemas e falhas internas quando não detetados precocemente podem prejudicar
gravemente todo um sistema de rede. Assim, esta Tese apresenta um sistema autônomo
de deteção de anomalias baseado em perfil utilizando o método estatÃstico Análise de Componentes
Principais (PCADS-AD). Essa abordagem cria um perfil de rede chamado Assinatura Digital
do Segmento de Rede usando Análise de Fluxos (DSNSF) que denota o comportamento normal
previsto de uma atividade de tráfego de rede por meio da análise de dados históricos. Essa
assinatura digital é utilizada como um limiar para deteção de anomalia de volume e identificar
disparidades na tendência de tráfego normal. O sistema proposto utiliza sete atributos de fluxo
de tráfego: bits, pacotes e número de fluxos para detetar problemas, além de endereços IP e
portas de origem e destino para fornecer ao administrador de rede as informações necessárias
para resolvê-los.
Por meio da utilização de métricas de avaliação, do acrescimento de uma abordagem
de deteção distinta da proposta principal e comparações com outros métodos realizados nesta
tese usando dados reais de tráfego de rede, os resultados mostraram boas previsões de tráfego
pelo DSNSF e resultados encorajadores quanto a geração de alarmes falsos e precisão de deteção.
Com os resultados observados nesta tese, este trabalho de doutoramento busca contribuir
para o avanço do estado da arte em métodos e estratégias de deteção de anomalias,
visando superar alguns desafios que emergem do constante crescimento em complexidade, velocidade
e tamanho das redes de grande porte da atualidade, proporcionando também alta
performance. Ainda, a baixa complexidade e agilidade do sistema proposto contribuem para
que possa ser aplicado a deteção em tempo real
Advances in Deep Learning Towards Fire Emergency Application : Novel Architectures, Techniques and Applications of Neural Networks
Paper IV is not published yet.With respect to copyright paper IV and paper VI was excluded from the dissertation.Deep Learning has been successfully used in various applications, and recently, there has been an increasing interest in applying deep learning in emergency management. However, there are still many significant challenges that limit the use of deep learning in the latter application domain. In this thesis, we address some of these challenges and propose novel deep learning methods and architectures.
The challenges we address fall in these three areas of emergency management: Detection of the emergency (fire), Analysis of the situation without human intervention and finally Evacuation Planning. In this thesis, we have used computer vision tasks of image classification and semantic segmentation, as well as sound recognition, for detection and analysis. For evacuation planning, we have used deep reinforcement learning.publishedVersio
Search and optimization with randomness in computational economics: equilibria, pricing, and decisions
In this thesis we study search and optimization problems from computational economics with primarily stochastic inputs. The results are grouped into two categories: First, we address the smoothed analysis of Nash equilibrium computation. Second, we address two pricing problems in mechanism design, and solve two economically motivated stochastic optimization problems.
Computing Nash equilibria is a central question in the game-theoretic study of economic systems of agent interactions. The worst-case analysis of this problem has been studied in depth, but little was known beyond the worst case. We study this problem in the framework of smoothed analysis, where adversarial inputs are randomly perturbed. We show that computing Nash equilibria is hard for 2-player games even when input perturbations are large. This is despite the existence of approximation algorithms in a similar regime. In doing so, our result disproves a conjecture relating approximation schemes to smoothed analysis. Despite the hardness results in general, we also present a special case of co-operative games, where we show that the natural greedy algorithm for finding equilibria has polynomial smoothed complexity. We also develop reductions which preserve smoothed analysis.
In the second part of the thesis, we consider optimization problems which are motivated by economic applications. We address two stochastic optimization problems. We begin by developing optimal methods to determine the best among binary classifiers, when the objective function is known only through pairwise comparisons, e.g. when the objective function is the subjective opinion of a client. Finally, we extend known algorithms in the Pandora's box problem --- a classic optimal search problem --- to an order-constrained setting which allows for richer modelling.
The remaining chapters address two pricing problems from mechanism design. First, we provide an approximately revenue-optimal pricing scheme for the problem of selling time on a server to jobs whose parameters are sampled i.i.d. from an unknown distribution. We then tackle the problem of fairly dividing chores among a collection of economic agents via a competitive equilibrium, which balances assigned tasks with payouts. We give efficient algorithms to compute such an equilibrium
Gaining Insight into Determinants of Physical Activity using Bayesian Network Learning
Contains fulltext :
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