Air‐ground Matching: Appearance‐based GPS‐denied Urban Localization of Micro Aerial Vehicles

In this paper, we address the problem of globally localizing and tracking the pose of a camera‐equipped micro aerial vehicle (MAV) flying in urban streets at low altitudes without GPS. An image‐based global positioning system is introduced to localize the MAV with respect to the surrounding buildings. We propose a novel air‐ground image‐matching algorithm to search the airborne image of the MAV within a ground‐level, geotagged image database. Based on the detected matching image features, we infer the global position of the MAV by back‐projecting the corresponding image points onto a cadastral three‐dimensional city model. Furthermore, we describe an algorithm to track the position of the flying vehicle over several frames and to correct the accumulated drift of the visual odometry whenever a good match is detected between the airborne and the ground‐level images. The proposed approach is tested on a 2 km trajectory with a small quadrocopter flying in the streets of Zurich. Our vision‐based global localization can robustly handle extreme changes in viewpoint, illumination, perceptual aliasing, and over‐season variations, thus outperforming conventional visual place‐recognition approaches. The dataset is made publicly available to the research community. To the best of our knowledge, this is the first work that studies and demonstrates global localization and position tracking of a drone in urban streets with a single onboard camera.     

Melting of PCM in a thermal energy storage unit: Numerical investigation and effect of nanoparticle enhancement

The present paper describes the analysis of the melting process in a single vertical shell‐and‐tube latent heat thermal energy storage (LHTES), unit and it is directed at understanding the thermal performance of the system. The study is realized using a computational fluid‐dynamic (CFD) model that takes into account of the phase‐change phenomenon by means of the enthalpy method. Fluid flow is fully resolved in the liquid phase‐change material (PCM) in order to elucidate the role of natural convection. The unsteady evolution of the melting front and the velocity and temperature fields is detailed. Temperature profiles are analyzed and compared with experimental data available in the literature. Other relevant quantities are also monitored, including energy stored and heat flux exchanged between PCM and HTF. The results demonstrate that natural convection within PCM and inlet HTF temperature significantly affects the phase‐change process. Thermal enhancement through the dispersion of highly conductive nanoparticles in the base PCM is considered in the second part of the paper. Thermal behavior of the LHTES unit charged with nano‐enhanced PCM is numerically analyzed and compared with the original system configuration. Due to increase of thermal conductivity, augmented thermal performance is observed: melting time is reduced of 15% when nano‐enhanced PCM with particle volume fraction of 4% is adopted. Similar improvements of the heat transfer rate are also detected. Copyright © 2012 John Wiley & Sons, Ltd.     

Different design scenarios related to an open loop groundwater heat pump in a large building: Impact on subsurface and primary energy consumption

A multidisciplinary methodology is proposed for analyzing opportunities to use existing boreholes and an open-loop groundwater heat pump to provide summer cooling needs for large university buildings in Turin (NW Italy). The approach starts from a model of the buildings to determine the time profile of the cooling load. This curve is then coupled with a model of the off-design behaviour of the heat pump, which allows calculation of its energy performance (coefficient of performance, electricity consumption, etc.) as well as profiles of water discharge to the aquifer in terms of mass flow rate and temperature.Covering the peak energy needs of the buildings requires a variable amount of groundwater during the day. This could be provided varying the withdrawals from the aquifer but, as possible alternatives, two storage system solutions are examined: (1) chilled water storage and (2) groundwater storage. Simulations show that in both cases the use of storage systems produces environmental advantages, as the extent of the thermal plume reduces significantly. Moreover, chilled water storage presents a benefit in terms of reduced total primary energy consumption. The additional costs incurred by storage systems could necessitate public funding as well as system optimization.     

Pilot Study of Quality Function Deployment in Construction Projects

Quality function deployment (QFD) is a process that has been used for managing the development of new manufactured products. In this process, both spoken and unspoken needs of the customers are determined, prioritized, and translated to design parameters. Such design parameters are assigned specific target values and are frequently checked against customers’ needs throughout the development cycle to ensure customers’ satisfaction with the end product. This paper describes a pilot study in which QFD was implemented in a design-construction project. The project scope involved the preparation of a conceptual design for a modern large-size classroom for college students. The design was intended to become a model for the university’s future classrooms. The study proved that QFD could be successfully adopted in engineering-construction projects. However, the study identified a number of implementation challenges. In addition, more applications are necessary to take the process throughout the full project delivery cycle, as the pilot study involved only the preliminary engineering and conceptual design phase.     

Comparison of the translucency of two multishaded composite resins polymerized with direct or indirect method

The aim of this study was to measure the translucency of one indirect and direct resin composite after polymerization and to examine the effect of color parameters on this property. Tescera and Filtek Ultimate, each containing three shade groups (Enamel, Dentin and Body for Filtek Ultimate; and Incisal, Opaceous Dentin and Body for Tescera), were investigated. The translucency parameter (TP) was measured as the color difference between a specimen over a white and black background. Significant differences were observed in TP values between shade groups. Tukey’s multiple comparison test revealed TP values among the groups of Filtek Ultimate-Enamel > Tescera-Incisal > Filtek Ultimate-Body > Tescera-Body = Filtek Ultimate-Dentin > Tescera-Opaceous Dentin. In conclusion, it is concluded that the translucency of resin composite was affected by polymerization and color parameters.     

A generalized reduced fluid dynamic model for flow fields and electrodes in redox flow batteries

High-dimensional models typically require a large computational overhead for multiphysics applications, which hamper their use for broad-sweeping domain interrogation. Herein, we develop a modeling framework to capture the through-plane fluid dynamic response of electrodes and flow fields in a redox flow cell, generating a computationally inexpensive two-dimensional (2D) model. We leverage a depth-averaging approach that also accounts for variations in out-of-plane fluid motion and departures from Darcy's law that arise from averaging across three-dimensions (3D). Our resulting depth-averaged 2D model successfully predicts the fluid dynamic response of arbitrary in-plane flow field geometries, with discrepancies of <5% for both maximum velocity and pressure drop. This corresponds to reduced computational expense, as compared to 3D representations (<1% of duration and 10% of RAM usage), providing a platform to screen and optimize a diverse set of cell geometries.     

Structure-based object representation and classification in mobile robotics through a Microsoft Kinect

A new approach enabling a mobile robot to recognize and classify furniture-like objects composed of assembled parts using a Microsoft Kinect is presented. Starting from considerations about the structure of furniture-like objects, i.e., objects which can play a role in the course of a mobile robot mission, the 3D point cloud returned by the Kinect is first segmented into a set of “almost convex” clusters. Objects are then represented by means of a graph expressing mutual relationships between such clusters. Off-line, snapshots of the same object taken from different positions are processed and merged, in order to produce multiple-view models that are used to populate a database. On-line, as soon as a new object is observed, a run-time window of subsequent snapshots is used to search for a correspondence in the database.Experiments validating the approach with a set of objects (i.e., chairs, tables, but also other robots) are reported and discussed in detail.     

A fuzzy logic procedure for ventilation control in case of fire in long tunnels

Ventilation is a crucial element while managing fire events in tunnels. This paper deals with ventilation strategies to be applied in case of fire in a long tunnel. The Frejus road tunnel has been considered as an application. This is a single tube road tunnel with semi-transversal ventilation. Ordinary and emergency ventilations are operated by using dedicated supply and extraction ducts.