Model-free Method of Reinforcement Learning for Visual Tasks

There has been success in recent years for neural networks in applications requiring high level intelligence such as categorization and assessment. In this work, we present a neural network model to learn control policies using reinforcement learning. It takes a raw pixel representation of the current state and outputs an approximation of a Q value function made with a neural network that represents the expected reward for each possible state-action pair. The action is chosen an \epsilon-greedy policy, choosing the highest expected reward with a small chance of random action. We used gradient descent to update the weights and biases of this network as it is efficient in terms of computation and convergence rate even with large scale models. To test this network, we designed a simple search task over a 4x4 grid. No assumptions were made about the control task. Given only raw inputs for state and the reward received from actions paired with that state, the agent was able to learn this task. Performance was evaluated using the number of rewards received out of 10000 opportunities. Over the course of 5 epochs, the network demonstrated significantly higher accuracy than random action alone for low dimensionality spaces. On higher dimensionality inputs, oscillation is observed leading to significantly lower accuracy and much higher variability. PCA proved to be an effective means of feature extraction reducing the dimensionality of the input, increasing precision; however, it required a dataset to be generated from initial random action

Metodologia para diagnóstico da integridade e segurança de equipamentos estáticos: foco em refinaria de petróleo

Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico. Programa de Pós-graduação em Engenharia MecânicaGrandes perdas decorrentes de falhas e acidentes têm marcado a indústria de processo, particularmente as refinarias de petróleo, tanto por ocorrências de acidentes catastróficos isolados quanto, principalmente, pelo somatório de eventos de pequena magnitude do dia-a-dia. Ocorrências indesejáveis com equipamentos estáticos representam cerca de 70% dessas perdas, sendo a manutenção responsável por quase metade. As causas fundamentais de falhas e acidentes podem ter natureza técnica, humana ou organizacional. As falhas técnicas são tratadas pelo atributo da qualidade do produto para evitar condições latentes de natureza técnica e pelo atributo da integridade física para evitar condições inseguras. As falhas humanas e organizacionais são tratadas pela cultura de segurança, partindo-se das teorias desenvolvidas nos últimos vinte e cinco anos, que distinguem as diversas as classes de erro humano envolvidas em falhas e acidentes. Para estudar as falhas organizacionais, adotou-se um modelo de formação do comportamento humano baseado na interação dos domínios psicológico, condições de trabalho e situação organizacional, inserindo-o em um modelo epidemiológico de fluxo causal de acidentes vinculados a falhas, que preconiza que decisões gerenciais e institucionais geram condições latentes que agem sobre tais domínios da organização, proporcionando a constituição de atos inseguros e a degradação das barreiras do sistema, que culminam em falhas ou mesmo acidentes. A metodologia para definir o diagnóstico da integridade e segurança de equipamentos estáticos é constituída por uma série de proposições que sustenta um processo de varredura em cada domínio para identificar as causas fundamentais de falhas e acidentes, de forma a antecipar-se à ocorrência desses eventos indesejáveis ou minimizar as suas conseqüências. Os modelos de acidentes e as classificações das falhas adotadas para compor a metodologia permitem utilizar as mesmas ferramentas de identificação de causas fundamentais para qualquer das naturezas de falha. Process industry has been marked by big losses due to failures and accidents, in special petroleum refineries, as from catastrophic accidents or mainly due to small-scale events. These occurrences with static equipments represent 70% of these losses, at which maintenance is responsible for one half of them. The underlying causes of accidents and failures can be technical, human or organizational nature. Technical failures are treated by product quality to avoid latent conditions of technical nature and by physical integrity to avoid unsafe conditions. Human and organizational failures are treated by safety culture, applying theories which classify human error and have been developed at last twenty five years to explain accidents and failures. To study organizational failures, it was adopted a model of conception of human act based on interaction of psychology, job and situational factors, at which it was introduced in a epidemiologic model of causal flux of accidents linked to failures that preconizes institutional and managerial decisions create latent conditions in components of activities of the organization that act over such factors, conducing to generation of unsafe acts and to deterioration of system barriers and safeguards, that results at failures or even accidents. The methodology to diagnostic integrity and safety of static equipments is constituted of several questions to support a scanning process to each factor to identify fundamental causes of failures and accidents, antecipating these undesirable events or minimizing their consequences. Accident models and failure classifications that were adopted to compose the methodology permit to aplly the same tools to identify root causes of technical, human and organizational nature

The chiral logs of the K -> pi pi amplitude

I calculate the leading logarithmic contributions up to two-loop order of the octet part of the K -> pi pi amplitude. This sector of the weak chiral Lagrangian is believed to be the main source of the enhancement of the I=0 relative to the I=2 K -> pi pi amplitude, the so-called Delta I = 1/2 rule. I discuss the procedure of chiral extrapolations of lattice data specific to K -> pi pi decays and study the implication of the present calculation on these numerically. The latter reinforces the fact that one has to expect a large enhancement of the I=0 part of the amplitude due to re-scattering effects between the three mesons.Comment: 20 pages, 4 figures, uses axodra

The nature of the bonds in the iron silicide, FeSi, and related crystals

The iron silicide FeSi has been reinvestigated by X-ray photography of single crystals, and the reported structure for the substance has been verified. The space group is T^4-P2_13, with a_0 = 4.489 ± 0.005 A. Four iron atoms and four silicon atoms are in positions (x, x, x; x + 1/2, 1/2} - x, x[bar]; undefined), with x_(Fe) = 0.1370 ± 0.0020 and x_(Si) = 0.842 ± 0.004. A detailed discussion of the structure and the values of the interatomic distances has been given, by application of the resonating-valence-bond theory, and it has been shown that the interatomic distances are compatible with those found for elementary iron and elementary silicon

Nonlocal Yang-Mills

We present a very simple and explicit procedure for nonlocalizing the action of any theory which can be formulated perturbatively. When the resulting nonlocal field theory is quantized using the functional formalism --- with unit measure factor --- its Green's functions are finite to all orders. The construction also ensures perturbative unitarity to all orders for scalars with nonderivative interactions, however, decoupling is lost at one loop when vector and tensor quanta are present. Decoupling can be restored (again, to all orders) if a suitable measure factor exists. We compute the required measure factor for pure Yang-Mills at order $g^2$ and then use it to evaluate the vacuum polarization at one loop. A peculiar feature of our regularization scheme is that the on-shell tree amplitudes are completely unaffected. This implies that the nonlocal field theory can be viewed as a highly noncanonical quantization of the original, local field equations.Comment: 38 pages, figures available upon request. No macro neede

Standard Model Higgs boson searches with the ATLAS detector at the Large Hadron Collider

The investigation of the mechanism responsible for electroweak symmetry breaking is one of the most important tasks of the scientific program of the Large Hadron Collider. The experimental results on the search of the Standard Model Higgs boson with 1 to 2 fb^-1 of proton proton collision data at sqrt s=7 TeV recorded by the ATLAS detector are presented and discussed. No significant excess of events is found with respect to the expectations from Standard Model processes, and the production of a Higgs boson is excluded at 95% Confidence Level for the mass regions 144-232, 256-282 and 296-466 GeV.Comment: Proceedings of the Lepton Photon 2011 Conference, to appear in "Pramana - journal of phsyics". 11 pages, 13 figure

Walking Technicolor and Electroweak Radiative Corrections

We examine the effect of walking technicolor dynamics on the electroweak $S$ parameter and contrast it with the effect of QCD-like technicolor dynamics. Our main tools are the operator product expansion for the high-momentum behavior of the electroweak gauge boson vacuum polarizations and the analyticity of these polarizations which relate their low and high momentum behaviors. We show that whereas in large QCD-like technicolor models $S$ is large and positive, in walking technicolor models a negative contribution is emphasized, related to the large anomalous dimension of the technifermion condensate. Thus in walking technicolor $S$ is determined by a large cancellation of two competing effects. This may result in much smaller values of $S$ than in QCD-like technicolor, although considerable uncertainties are involved. We conclude that it is impossible to rule out walking technicolor based on the present experimental limits on $S$ and the present theoretical technology.Comment: 22 pages (4 figures, available upon request

String Balls at the LHC and Beyond

In string theory, black holes have a minimum mass below which they transition into highly excited long and jagged strings --- ``string balls''. These are the stringy progenitors of black holes; because they are lighter, in theories of TeV-gravity, they may be more accessible to the LHC or the VLHC. They share some of the characteristics of black holes, such as large production cross sections. Furthermore, they evaporate thermally at the Hagedorn temperature and give rise to high-multiplicity events containing hard primary photons and charged leptons, which have negligible standard-model background.Comment: 7 page

Electroweak Corrections in Technicolor Reconsidered

Radiative corrections to electroweak parameters in technicolor theories may be evaluated by one of two techniques: either one estimates spectral function integrals using scaled QCD data, or one uses naive dimensional analysis with a chiral Lagrangian. The former yields corrections to electroweak parameters proportional to the number of flavors and the number of colors, while the latter is proportional to the number of flavors squared and is independent of the number of colors. We attempt to resolve this apparent contradiction by showing that the spectrum of technicolor one obtains by scaling QCD data to high energies is unlikely to resemble that of an actual technicolor theory. The resonances are likely to be much lighter than naively supposed and the radiative corrections to electroweak parameters may by much larger. We also argue that much less is known about the spectrum and the radiative corrections in technicolor than was previously believed.Comment: 17 pages (which incl 3 figures), BUHEP-92-25 HUTP-92/A033, text uses harvmac, figures use picte

Unitarity of Compactified Five Dimensional Yang-Mills Theory

Compactified five dimensional Yang-Mills theory results in an effective four-dimensional theory with a Kaluza-Klein (KK) tower of massive vector bosons. We explicitly demonstrate that the scattering of the massive vector bosons is unitary at tree-level for low energies, and analyze the relationship between the unitarity violation scale in the KK theory and the nonrenormalizability scale in the five dimensional gauge theory. In the compactified theory, low-energy unitarity is ensured through an interlacing cancellation among contributions from the relevant KK levels. Such cancellations can be understood using a Kaluza-Klein equivalence theorem which results from the geometric ``Higgs'' mechanism of compactification. In these theories, the unitarity violation is delayed to energy scales higher than the customary limit through the introduction of additional vector bosons rather than Higgs scalars.Comment: 10 pages, 1 eps figure, discussion of deconstruction expanded, version accepted for publication in PL