Semi-automated detection of surface degradation on bridges based on a level set method

Due to the effect of climate factors, natural phenomena and human usage, buildings and infrastructures are subject of progressive degradation. The deterioration of these structures has to be monitored in order to avoid hazards for human beings and for the natural environment in their neighborhood. Hence, on the one hand, monitoring such infrastructures is of primarily importance. On the other hand, unfortunately, nowadays this monitoring effort is mostly done by expert and skilled personnel, which follow the overall data acquisition, analysis and result reporting process, making the whole monitoring procedure quite expensive for the public (and private, as well) agencies. This paper proposes the use of a partially user-assisted procedure in order to reduce the monitoring cost and to make the obtained result less subjective as well. The developed method relies on the use of images acquired with standard cameras by even inexperienced personnel. The deterioration on the infrastructure surface is detected by image segmentation based on a level sets method. The results of the semi-automated analysis procedure are remapped on a 3D model of the infrastructure obtained by means of a terrestrial laser scanning acquisition. The proposed method has been successfully tested on a portion of a road bridge in Perarolo di Cadore (BL), Italy

Thermal modeling of industrial-scale vanadium redox flow batteries in high-current operations

A cell-resolved model that simulates the dynamic thermal behavior of a Vanadium Redox Flow Battery during charge and discharge is presented. It takes into account, at a cell level, the reversible entropic heat of the electrochemical reactions, irreversible heat due to overpotentials, self-discharge reactions due to ion crossover, and shunt current losses. The model accounts for the heat transfer between cells and toward the environment, the pump hydraulic losses and the heat transfer of piping and tanks. It provides the electrolyte temperature in each cell, at the stack inlet and outlet, along the piping and in the tanks. Validation has been carried out against the charge/discharge measurements from a 9kW/27kWh VRFB test facility. The model has been applied to study a VRFB with the same stack but a much larger capacity, operating at \uf0b1400 A for 8 h, in order to identify critical thermal conditions which may occur in next-generation industrial VRFB stacks capable to operating at high current density. The most critical condition has been found at the end a long discharge, when temperatures above 50\ub0C appeared, possibly resulting in \u3016VO\u3017_2^+ precipitation and battery faults. These results call for heat exchangers tailored to assist high-power VRFB systems

Multiphysics Finite\u2013Element Modelling of an All\u2013Vanadium Redox Flow Battery for Stationary Energy Storage

All-Vanadium Redox Flow Batteries (VRFBs) are emerging as a novel technology for stationary energy storage. Numerical models are useful for exploring the potential performance of such devices, optimizing the structure and operating condition of cell stacks, and studying its interfacing to the electrical grid. A one-dimensional steady-state multiphysics model of a single VRFB, including mass, charge and momentum transport and conservation, and coupled to a kinetic model for electrochemical reactions, is first presented. This model is then extended, including reservoir equations, in order to simulate the VRFB charge and discharge dynamics. These multiphysics models are discretized by the finite element method in a commercial software package (COMSOL). Numerical results of both static and dynamic 1D models are compared to those from 2D models, with the same parameters, showing good agreement. This motivates the use of reduced models for a more efficient system simulation

A geodatabase for multisource data applied to cultural heritage: The case study of Villa Revedin Bolasco

In this paper we present the results of the development of a Web-based archiving and documenting system aimed to the management of multisource and multitemporal data related to cultural heritage. As case study we selected the building complex of Villa Revedin Bolasco in Castefranco Veneto (Treviso, Italy) and its park. Buildings and park were built in XIX century after several restorations of the original XIV century area. The data management system relies on a geodatabase framework, in which different kinds of datasets were stored. More specifically, the geodatabase elements consist of historical information, documents, descriptions of artistic characteristics of the building and the park, in the form of text and images. In addition, we used also floorplans, sections and views of the outer facades of the building extracted by a TLS-based 3D model of the whole Villa. In order to manage and explore these rich dataset, we developed a geodatabase using PostgreSQL and PostGIS as spatial plugin. The Web-GIS platform, based on HTML5 and PHP programming languages, implements the NASA Web World Wind virtual globe, a 3D virtual globe we used to enable the navigation and interactive exploration of the park. Furthermore, through a specific timeline function, the user can explore the historical evolution of the building complex

Aplicación del enfoque de la Teoría de las Restricciones a la gestión de inventarios de productos terminados, bajo condiciones de demanda aleatoria e inestacionaria

This work aims to determine, through a simulation experiment, if the application of Dynamic Buffer Management (DBM), under conditions of random and non-stationary demand, leads to operate with lower levels of stock, compared to a policy of periodic adaptive revision. The sensitivity of the solution to the variation of the demand prediction method that is used to adapt the parameters of the continuous review method will also be studied. A field study will be conduct to confirm the results obtained in the experimental environment. Management quality and the policies that a firm uses to handle its inventories can have a significant impact on its profitability. Different inventory management models seek to answer how often inventory position should be determined, when a replenishment order should be placed, and how much material should be ordered. These are key factors in operating at a low inventory level, maintaining a high delivery performance. Usually actual demand behaves as non-stationary, i.e. its average changes over time. The mathematical treatment of this situation is difficult and impractical for routine application. Consequently, heuristic solutions are used to adjust the control parameters, depending on the prediction of future demand. The Theory of Constraints offers a different approach to this problem. Instead of predicting demand, the method called Dynamic Buffer Management makes a single initial approximation to the inventory value and then adjusts its level according to the actual demand and the actual protection provided by this inventory. A control system was selected which, every R units of time, checks the inventory position and orders the quantity needed to return it to a fixed level S. This system, known as (R.S), was chosen for its simplicity and for its extended use. From this model, the algorithm was developed to adapt the control parameters to significant changes in demand. It is considered that the reorder period R is a predefined parameter for practical reasons, therefore, the parameter that adapts is S (maximum level of inventory). A two-level DBM procedure was selected, which implies the use of target inventory level and a security level. The implementation algorithm and a Monte Carlo simulator were developed for the DBM control model that reached the verification stage.Este trabajo tiene por objetivo determinar, mediante un experimento de simulación, si la aplicación de Dynamic Buffer Management (DBM), en condiciones de demanda aleatoria y no estacionaria, lleva a operar con menores niveles de stock, en comparación con una política de revisión periódica adaptativa. Se estudia también la sensibilidad de la solución obtenida a la variación del método de predicción de demanda que se utilice para adaptar los parámetros del método de revisión continua. Mediante un estudio de campo se busca confirmar los resultados obtenidos en ambiente experimental. La calidad de la gestión y de las políticas que una firma use para administrar sus inventarios puede tener un impacto significativo sobre su rentabilidad. Los distintos modelos de gestión de inventario buscan responder qué tan frecuentemente se debe determinar la posición de inventario, cuándo se debe colocar una orden de reabastecimiento y cuánto material se debe pedir. Estos son factores claves para lograr operar con un bajo nivel de inventario, manteniendo una alta performance de entrega. En general la demanda real se comporta como no estacionaria, es decir su promedio cambia con el tiempo. Esta situación es de difícil tratamiento matemático, poco práctico para la aplicación rutinaria. Consecuentemente, se utilizan soluciones heurísticas y se ajustan los parámetros de control, en función de la predicción de la demanda futura. La Teoría de las Restricciones ofrece un abordaje distinto de este problema. En lugar de predecir la demanda, el método denominado Dynamic Buffer Management hace una única aproximación inicial al valor de inventario y luego va ajustando su nivel según se comporta la demanda real y la protección proporcionada por este inventario. Se seleccionó un sistema de control que, cada R unidades de tiempo, verifica la posición de inventario y ordena la cantidad necesaria para devolverla a un nivel fijo S. Este sistema, conocido como (R.S), se eligió por su sencillez y lo extendido de su uso. A partir de este modelo, se desarrolló el algoritmo de adaptación de los parámetros de control a cambios significativos de la demanda. Se considera que el período de reorden R es una constante predefinida por razones prácticas, por lo tanto, el parámetro que se adapta es S (nivel máximo de inventario). Se seleccionaron procedimientos de gestión mediante DBM de dos niveles, uno de inventario objetivo y otro de seguridad, se desarrollaron los algoritmos de implementación y un simulador tipo Monte Carlo, para el modelo de control DBM que alcanzó la etapa de verificación

State of the Art of Ground and Aerial Laser Scanning Technologies for High-Resolution Topography of the Earth Surface

AbstractLaser scanners have increased their efficiency exponentially when compared to state of the art ten years ago. More data can be acquired—and higher accuracy can be achieved—over longer ranges thanks to advancements in sensor technology. The goal of this review is to present state of the art of terrestrial and aerial laser scanner surveys with a critical discussion over quality, which is a very important aspect for high-resolution topography

GENERATION OF INDOOR POINT CLOUDS EXPLOITING GEOMETRIC SYMMETRIES AND REGULARITIES

Abstract. 3D building modeling is becoming an important support in civil engineering, architecture and cultural heritage applications. Despite static laser scanning can be considered as the state-of-the-art in such kind of applications, mobile mapping techniques can be considered as a suitable alternative to quickly gather geospatial information. Outdoor mobile mapping can be considered as a mature technique, which takes into advantage of the Global Navigation Satellite System (GNSS)-laser scanning information fusion. Instead, indoor mobile mapping is typically more challenging: the unavailability of GNSS makes the mapping system rely either just on the inertial navigation system, or on some control points. A drift in the navigation solution, and consequently in the 3D reconstruction, is typically visible after a while in the former case, whereas the use of other surveying instruments is required in the latter.This work aims at exploiting geometric characteristics of the buildings, such as symmetries and regularities, to reduce the drift effect in indoor mobile mapping, in particular when dealing with affordable systems. The proposed approach is based on the segmentation of the point clouds acquired with a time of flight camera (ToF), detecting in particular vertical planar surfaces. It is well known that aligning planar surfaces can be a viable way for reducing the drift in this kind of applications. Nevertheless, this paper aims also at investigating the use of geometric symmetries to such aim.The proposed approach is tested on a case study, a building of the University of Padova, whose reconstruction was produced by an ad hoc affordable mobile mapping system, integrating low cost inertial sensors, RGB and ToF camera

Automatic coarse co-registration of point clouds from diverse scan geometries: a test of detectors and descriptors

Point clouds are collected nowadays from a plethora of sensors, some having higher accuracies and higher costs, some having lower accuracies but also lower costs. Not only there is a large choice for different sensors, but also these can be transported by different platforms, which can provide different scan geometries. In this work we test the extraction of four different keypoint detectors and three feature descriptors. We benchmark performance in terms of calculation time and we assess their performance in terms of accuracy in their ability in coarse automatic co-registration of two clouds that are collected with different sensors, platforms and scan geometries. One, which we define as having the higher accuracy, and thus will be used as reference, was surveyed via a UAV flight with a Riegl MiniVUX-3, the other on a bicycle with a Livox Horizon over a walking path with un-even ground.The novelty in this work consists in comparing several strategies for fast alignment of point clouds from very different surveying geometries, as the drone has a bird's eye view and the bicycle a ground-based view. An added challenge is related to the lower cost of the bicycle sensor ensemble that, together with the rough terrain, reasonably results in lower accuracy of the survey. The main idea is to use range images to capture a simplified version of the geometry of the surveyed area and then find the best features to match keypoints. Results show that NARF features detected more keypoints and resulted in a faster co-registration procedure in this scenariowhereas the accuracy of the co-registration is similar to all the combinations of keypoint detectors and features