Monitoreo y control estadístico de atributos en procesos con alta tasa de producción y bajo número de defectos: aplicación a un caso real de planta

Los procesos de alta calidad se basan en una baja tasa de productos no conformes. Tradicionalmente el monitoreo de los procesos se realiza a través de los gráficos tradicionales de Shewhart (3-sigma), basados en la aproximación normal. Pero este tipo de gráfico no es exacto cuando la tasa de defectos p es muy pequeña. En la presente tesis se realiza una comparación entre los gráficos tradicionales de Shewhart con otros tipos basados en la corrección de los límites de control y con otros basados en la suma acumulada de conformidades que se miden en partes por millón (ppm). Estos gráficos para procesos de alta calidad tienen la ventaja de ser más sensibles ante la tasa de defectos de baja.Fil: Fürth, Patricia Alejandra Carolina von. Universidad Católica de Córdoba. Facultad de Ciencias Químicas; Argentin

Monitoreo y control estadístico de atributos en procesos con alta tasa de producción y bajo número de defectos: aplicación a un caso real de planta

Los procesos de alta calidad se basan en una baja tasa de productos no conformes. Tradicionalmente el monitoreo de los procesos se realiza a través de los gráficos tradicionales de Shewhart (3-sigma), basados en la aproximación normal. Pero este tipo de gráfico no es exacto cuando la tasa de defectos p es muy pequeña. En la presente tesis se realiza una comparación entre los gráficos tradicionales de Shewhart con otros tipos basados en la corrección de los límites de control y con otros basados en la suma acumulada de conformidades que se miden en partes por millón (ppm). Estos gráficos para procesos de alta calidad tienen la ventaja de ser más sensibles ante la tasa de defectos de baja.Fil: Fürth, Patricia Alejandra Carolina von. Universidad Católica de Córdoba. Facultad de Ciencias Químicas; Argentin

Active Brownian Particles. From Individual to Collective Stochastic Dynamics

We review theoretical models of individual motility as well as collective dynamics and pattern formation of active particles. We focus on simple models of active dynamics with a particular emphasis on nonlinear and stochastic dynamics of such self-propelled entities in the framework of statistical mechanics. Examples of such active units in complex physico-chemical and biological systems are chemically powered nano-rods, localized patterns in reaction-diffusion system, motile cells or macroscopic animals. Based on the description of individual motion of point-like active particles by stochastic differential equations, we discuss different velocity-dependent friction functions, the impact of various types of fluctuations and calculate characteristic observables such as stationary velocity distributions or diffusion coefficients. Finally, we consider not only the free and confined individual active dynamics but also different types of interaction between active particles. The resulting collective dynamical behavior of large assemblies and aggregates of active units is discussed and an overview over some recent results on spatiotemporal pattern formation in such systems is given.Comment: 161 pages, Review, Eur Phys J Special-Topics, accepte

Natural History of Tuberculosis: Duration and Fatality of Untreated Pulmonary Tuberculosis in HIV Negative Patients: A Systematic Review

Background The prognosis, specifically the case fatality and duration, of untreated tuberculosis is important as many patients are not correctly diagnosed and therefore receive inadequate or no treatment. Furthermore, duration and case fatality of tuberculosis are key parameters in interpreting epidemiological data. Methodology and Principal Findings To estimate the duration and case fatality of untreated pulmonary tuberculosis in HIV negative patients we reviewed studies from the pre-chemotherapy era. Untreated smear-positive tuberculosis among HIV negative individuals has a 10-year case fatality variously reported between 53% and 86%, with a weighted mean of 70%. Ten-year case fatality of culture-positive smear-negative tuberculosis was nowhere reported directly but can be indirectly estimated to be approximately 20%. The duration of tuberculosis from onset to cure or death is approximately 3 years and appears to be similar for smear-positive and smear-negative tuberculosis. Conclusions Current models of untreated tuberculosis that assume a total duration of 2 years until self-cure or death underestimate the duration of disease by about one year, but their case fatality estimates of 70% for smear-positive and 20% for culture-positive smear-negative tuberculosis appear to be satisfactory

Relativistic Brownian Motion

Stimulated by experimental progress in high energy physics and astrophysics, the unification of relativistic and stochastic concepts has re-attracted considerable interest during the past decade. Focusing on the framework of special relativity, we review, here, recent progress in the phenomenological description of relativistic diffusion processes. After a brief historical overview, we will summarize basic concepts from the Langevin theory of nonrelativistic Brownian motions and discuss relevant aspects of relativistic equilibrium thermostatistics. The introductory parts are followed by a detailed discussion of relativistic Langevin equations in phase space. We address the choice of time parameters, discretization rules, relativistic fluctuation-dissipation theorems, and Lorentz transformations of stochastic differential equations. The general theory is illustrated through analytical and numerical results for the diffusion of free relativistic Brownian particles. Subsequently, we discuss how Langevin-type equations can be obtained as approximations to microscopic models. The final part of the article is dedicated to relativistic diffusion processes in Minkowski spacetime. Due to the finiteness of velocities in relativity, nontrivial relativistic Markov processes in spacetime do not exist; i.e., relativistic generalizations of the nonrelativistic diffusion equation and its Gaussian solutions must necessarily be non-Markovian. We compare different proposals that were made in the literature and discuss their respective benefits and drawbacks. The review concludes with a summary of open questions, which may serve as a starting point for future investigations and extensions of the theory.Comment: review article, 159 pages, references updated, misprints corrected, App. A.4. correcte