Augmented reality applied in safety equipment inspections

The construction industry, and in particular a construction site, is a hazardous place for workers who are exposed to several risks. The dynamism and the complex interaction between the workers, machinery and the environment can lead to dangerous risks that need to be resolved. According to the European Union, the Architecture, Engineering, Construction and Operations (AECO) industry possess one of the highest accident rates among other industries, primarily due to the significant exposure to a construction site's risks compared to others. The accident rate is still relatively high despite the effort that the industry has made in terms of Occupational Risk Prevention (ORP) during the last years. The vision is to achieve the philosophy of zero accidents, which requires more effective methodologies that improve the capacity and the knowledge of the people involved in a construction site. These innovative solutions, consisting of building up risk-preventive data, training, and developing new technological tools to use on-site, are being studied and implemented by the industry. Nevertheless, there is still potential for enhancement on new methodologies that guarantees the safety of the workers

Monte Carlo Techniques in Computational Stochastic Mechanics

A state of the art on simulation methods in stochastic structural analysis is presented. The purpose of the paper is to review some of the di erent methods available for analysing the effects of randomness of models and data in structural analysis. While most of these techniques can be grouped under the general name of Monte Carlo methods, the several published algorithms are more suitable to some objectives of analysis than to others in each case. These objectives have been classiffed into the following cathegories: (1), The Statistical Description of the structural scattering, a primary analysis in which the uncertain parameters are treated as random variables; (2) The consideration of the spatial variability of the random parameters, that must then be modelled as Random Fields (Stochastic Finite Elements); (3) The advanced Monte Carlo methods for calculating the usually very low failure probabilities (Reliability Analysis) and, (4), a deterministic technique that depart from the random nature of the above methods, but which can be linked with them in some cases, known as the Response Surface Method. All of these techniques are critically examined and discussed. The concluding remarks point out some research needs in the field from the authors' point of view

The Maintenance of Male Color Polymorphism in Poecilia parae

Genetic color polymorphisms are common in nature, and a major challenge for evolutionary biologists has been to understand how they are maintained despite the effects of directional selection. Recent studies suggest that frequency-dependent selection may explain the persistence of intraspecific variation in color. However, it remains to be determined whether frequency-dependent selection is the most predominant (or perhaps the only) mechanism to maintain such genetically-based polymorphisms. Using a South American fish, Poecilia parae, my dissertation aims to elucidate the relative roles of natural and sexual selection in the maintenance of polymorphisms in natural populations. Poecilia parae males exhibit five distinct, Y-linked and co-occurring color morphs: (i) `immaculata\u27, the smallest and drab-colored males that resemble juvenile females; (ii) `parae\u27, the largest males that exhibit a striped tail and black vertical body bars that intensify during social interactions; and (iii) the blue, red, and yellow morphs that are of intermediate body size and display colorful body flanks. Field surveys indicate that the frequency of each morph remains relatively stable and consistent over multiple years. Using a combination of observational and experimental studies, accompanied by techniques that aimed to characterize the visual ecology (e.g., water light transmission, visual sensitivity) of Poecilia parae, I found that this striking color polymorphism is maintained by a complex balance between different components of natural and sexual selection. First, males of the five color morphs employ different behavioral mating strategies (hereafter alternative mating strategies, AMSs) to maximize their reproductive success. These AMSs are also accompanied by differences in morphological traits, such as testes investment and sperm morphometry that complement the specific tactic. For instance, immaculata males are often categorized as an `unattractive\u27 male by females, which is correlated to its phenotypical appearance (smaller and drab). However, this morph is relatively abundant. I found that immaculata males specialize in `sneak\u27 copulations and have adaptations (i.e., larger testes and unique sperm morphology) that possibly confer a fertilization advantage during postcopulatory events, when competing with the sperm of more attractive males. My studies also indicate that females have strong mating preferences for red and yellow males, with visual predators also favoring those males as prey. These findings suggest that the antagonistic interaction between pre-mating sexual selection favoring and predation acting against the red and yellow morphs may prevent them from eliminating other color morphs from the population. In fact, the red and yellow males were consistently found to be the rarest morphs across populations. Further, despite overall preference for red or yellow males, my analysis also detected female preferences for blue males. These results suggest that the interaction between female mating preferences and predation accompanied by variation in male reproductive strategies may allow for the maintenance of complex color polymorphism in natural populations. Males of the different morphs further vary in their levels of aggressive behaviors. In a series of controlled lab experiments, I found that parae males gain successful matings by preventing other males from accessing females and/or modifying female mating preferences after test females witness successful agonistic interactions. Finally, I found that the signaling environment of Poecilia parae in nature is variable and that this contributes to temporal and spatial variation in how males are perceived by females. Although red males were typically the most conspicuous morph, blue males were sometimes more conspicuous than red males at several sampling sites. The results also revealed that an aquatic model predator is able to discriminate the same male color morphs that resulted also conspicuous for females. However, it is possible that males and females of Poecilia parae are using parts of the background spectral that are least sensitive for predators. In conclusion, my dissertation suggests that balancing selection defined by the interaction between various episodes of selection allows for the invasion of AMSs and thus the maintenance of the male color polymorphism in Poecilia parae

Improved stochastic linearization method using mixed distributions

A new procedure for the random vibration analysis of hysteretic structures using stochastic equivalent linearization is reported. Its aim is to improve the prediction of the response obtained by conventional Gaussian linearization technique. To this purpose, mixed discrete-continuous Gaussian distributions are used taking into account the bounded nature of the non-linear restoring force. The simple but important property of the mixed distribution is its linearity, which allows the use of the previous results obtained by the Gaussian hypothesis, avoiding the need of employing non-Gaussian continuous distributions or other time-consuming techniques such as local Monte Carlo simulations. Closed-form expressions of the new linearization coefficients for the Bouc-Wen-Baber model are then provided. The relative weights of the discrete and Gaussian distributions are calculated in dependence of the degree of non-linearity in each time step. The comparison of the results with previously published ones obtained by simulation shows a good agreement, providing a substantial improvement of the method with respect to the conventional Gaussian technique with the same calculation effort

Equivalent linearization of the Bouc–Wen hysteretic model

The smooth endochronic hysteretic Bouc–Wen model is studied from the point of view of random vibration. The sources of the errors of the method of equivalent linearization applied to this model using the hypothesis of joint Gaussian behaviour are examined. The method of linearization for softening hysteretic models proposed by the authors, which is based on a combination of Dirac and Gauss densities, is developed and applied to the Bouc–Wen model under a variety of conditions. It is shown that the method gives excellent estimations of the response statistics without increasing the computational effort required by the conventional technique

Diseño de un sistema de protección electrónica para el sistema lubricación de un motor

En este proyecto se realizó la implementación de un sistema de protección al sistema de lubricación de un motor de combustión interna, esto con el fin de darle una alternativa al usuario que tiene un vehículo de gama baja y que no tiene como observar los datos de su sistema de lubricación: exponiéndolo a posibles fallas mecánicas y sobrecostos en las reparaciones, que pueden ser prevenidas por un sistema que transmita en un intervalo de tiempo los datos de la presión del aceite a una pantalla táctil que pueda ver el usuario

On k-Convex Polygons

We introduce a notion of $k$-convexity and explore polygons in the plane that have this property. Polygons which are \mbox{$k$-convex} can be triangulated with fast yet simple algorithms. However, recognizing them in general is a 3SUM-hard problem. We give a characterization of \mbox{$2$-convex} polygons, a particularly interesting class, and show how to recognize them in \mbox{$O(n \log n)$} time. A description of their shape is given as well, which leads to Erd\H{o}s-Szekeres type results regarding subconfigurations of their vertex sets. Finally, we introduce the concept of generalized geometric permutations, and show that their number can be exponential in the number of \mbox{$2$-convex} objects considered.Comment: 23 pages, 19 figure

Explicaciones de los estudiantes de grado quinto al resolver problemas relacionados con progresiones aritméticas

En la práctica pedagógica se adelanta una investigación en la cual se analizan las explicaciones escritas o verbales en estudiantes de grado quinto al resolver problemas relacionados con progresiones aritméticas. La investigación tiene como antecedentes las observaciones de clases, el rastreo de textos escolares colombianos y pruebas saber; adicionalmente las lecturas de: los Lineamientos Curriculares de Matemáticas (1998), los Estándares Básicos de Competencias (2003), y algunas investigaciones relacionadas con el estudio de patrones y regularidades a nivel nacional e internacional. (Merino, 2012; Castro, E, Cañadas, M. C. & Molina, M., 2010) Se emplea una metodología cualitativa, considerando los casos particulares en su contexto natural. Es por esto que se aplican los instrumentos para analizar la información y proponer conclusiones

The energy input spectrum scaling laws and synthetic compatible records

A method for predicting the seismic energy input spectrum is presented. The method is based on the analytical relationship linking this spectrum and other measures of earthquake energy such as power spectrum and Arias intensity, and the results of the statistical analysis made on 120 strong motion records. Upon the same relationships, a method for simulating artificial accelerograms compatible with a prescribed energy input spectrum is also developed. This procedure is used for the calculation of damage indexes for reinforced concrete single-degree-of freedom-systems, corresponding to types of energy input spectra and different ground motion durations. &nbsp

Relación de la escala de intensidad de Mercalli y la información instrumental como una tarea de clasificación de patrones

A pesar de los progresos ocurridos en la instrumentación sísmica, la valoración de vulnerabilidad sísmica y el daño con índices cualitativos, tal como los proporcionados por Intensidad de Mercalli Modificada (IMM), siguen siendo altamente favorables y útiles para los propósitos prácticos. Para vincular las medidas cualitativas de acción del terremoto y sus efectos, es habitualmente aplicada la regresión estadística. En este artículo, se adopta un planteamiento diferente, el cual consiste en expresar la Intensidad de Mercalli, como una clase en vez de un valor numérico. Una herramienta de clasificación estadística moderna, conocida como máquina de vectores de soporte, se usa para clasificar la información instrumental con el fin de evaluar la intensidad de Mercalli correspondiente. Se muestra que el método da resultados satisfactorios con respecto a las altas incertidumbres y a la medida del daño sísmico cualitativo