Investigating the Heat Generation Efficiency of Electrically-Conductive Asphalt Mastic Using Infrared Thermal Imaging

One of the emerging technologies for producing sustainable ice-and snow-free pavements is the use of electrically-conductive surface courses, e.g., electrically-conductive asphalt concrete (ECAC) that can melt ice and snow through resistive heating. Modifying the mastic in asphalt concrete with electrically-conductive materials is a promising approach for producing high-quality ECAC. The objective of this study is to evaluate electrical conductivity and heat generation efficiency of electrically-conductive asphalt mastic (ECAM) specimens at a below-freezing temperature—simulating the harsh weather conditions in North America during the wintertime. To this end, asphalt mastic was electrically modified with carbon fiber (CF) at varying volume contents. The ECAM specimens were then powered by 60V AC during a time window of 10 minutes so that their heat generation capacity could be characterized through infrared thermography (IRT). Based on the resistivity measurements and thermal data analysis, the most reasonable CF content enabling rapid heat-generating ECAM was identified; this has future implications with respect to achieving efficient highway, bridge, and airport pavement operations during wintertime

Dynamic structure selection and instabilities of driven Josephson lattice in high-temperature superconductors

We investigate the dynamics of the Josephson vortex lattice in layered high-T$_{c}$ superconductors at high magnetic fields. Starting from coupled equations for superconducting phases and magnetic field we derive equations for the relative displacements [phase shifts] between the planar Josephson arrays in the layers. These equations reveal two families of steady-state solutions: lattices with constant phase shifts between neighboring layers, starting from zero for a rectangular configuration to $\pi$ for a triangular configuration, and double-periodic lattices. We find that the excess Josephson current is resonantly enhanced when the Josephson frequency matches the frequency of the plasma mode at the wave vector selected by the lattice structure. The regular lattices exhibit several kinds of instabilities. We find stability regions of the moving lattice in the plane lattice structure - Josephson frequency. A specific lattice structure at given velocity is selected uniquely by boundary conditions, which are determined by the reflection properties of electromagnetic waves generated by the moving lattice. With increase of velocity the moving configuration experiences several qualitative transformations. At small velocities the regular lattice is stable and the phase shift between neighboring layers smoothly decreases with increase of velocity, starting from $\pi$ for a static lattice. At the critical velocity the lattice becomes unstable. At even higher velocity a regular lattice is restored again with the phase shift smaller than $\pi/2$. With increase of velocity, the structure evolves towards a rectangular configuration.Comment: 28 pages, 12 figures, submitted to Phys. Rev.

Energy absorption in lattice structures in dynamics: Experiments

Lattice structures offer the potential to relatively easily engineer specific (meso-scale properties (cell level)), to produce desirable macro-scale material properties for a wide variety of engineering applications including wave filters, blast and impact protection systems, thermal insulation, structural aircraft and vehicle components, and body implants. The work presented here focuses on characterising the quasi-static and, in particular, the dynamic load-deformation behaviour of lattice samples. First, cubic, diamond and re-entrant cube lattice structures were tested under quasi-static conditions to investigate failure process and stress–strain response of such materials. Following the quasi-static tests, Hopkinson pressure bar (HPB) tests were carried out to evaluate the impact response of these materials under high deformation rates. The HPB tests show that the lattice structures are able to spread impact loading in time and to reduce the peak impact stress. A significant rate dependency of load-deformation characteristics was identified. This is believed to be the first published results of experimental load-deformation studies of additively manufactured lattice structures. The cubic and diamond lattices are, by a small margin, the most effective of those lattices investigated to achieve this

Privaros: A Framework for Privacy-Compliant Delivery Drones

We present Privaros, a framework to enforce privacy policies on drones. Privaros is designed for commercial delivery drones, such as the ones that will likely be used by Amazon Prime Air. Such drones visit a number of host airspaces, each of which may have different privacy requirements. Privaros provides an information flow control framework to enforce the policies of these hosts on the guest delivery drones. The mechanisms in Privaros are built on top of ROS, a middleware popular in many drone platforms. This paper presents the design and implementation of these mechanisms, describes how policies are specified, and shows that Privaros's policy specification can be integrated with India's Digital Sky portal. Our evaluation shows that a drone running Privaros can robustly enforce various privacy policies specified by hosts, and that its core mechanisms only marginally increase communication latency and power consumption

A design approach on the use of lightweight filling materials for construction of an aircraft deicing station at a critical soil site: A case study

Deicing and anti-icing operations are frequently carried out on aircrafts at their current parking stand after completion of ground operations. Use of individual stands can be often challenging as this may also considerably affect operations, especially in highly-trafficked airports at winter-critical areas. Hence, a lack of or an incorrect location of these stations may have tremendous economic and operational impact. This research reports a multi-stage design method for construction of a 29,000 m2 deicing station in a critical soil site. The main aim of the project is to identify sustainable interventions in order to avoid short- A nd long-term economic, environmental, and operational issues. An assessment based on the use of fundamental geotechnical parameters is first implemented to create thematic maps of the identified construction area, followed by a comparative analysis of potential intervention scenarios. A combination of lightweight filling and advanced materials has been proposed to ensure homogeneity and suitable bearing capacity of the laying ground

Evaluating the Impact of Uncertainty on Airport Surface Operations

Flights spend significantly more time taxiing on the airport surface during periods when the departure demand exceeds airport capacity, resulting in excessive fuel burn. Departure metering by holding aircraft at the gate during periods of congestion has been shown to yield benefits by lowering the taxi-out time. However, an important aspect of this problem that has not been understood well is the impact of uncertainty in departure demand. Recently, some airlines are beginning to publish an expected time that the flights are ready to pushback, which is referred to as Earliest Off-Block Time (EOBT). Tactical decisions for departure metering need to be made with the EOBT information. However, the EOBT published by airlines is often found to deviate from the actual gate out time without departure metering, which represents an error in the EOBT estimate. Hence, it is important to consider errors in EOBT information while analyzing benefits from departure metering. In this paper, we present a queuing network model to predict aircraft taxi-times on the airport surface. The predictions from the queue model are used for departure metering with NASA’s ATD-2 logic that is being used in field trials at Charlotte airport. The framework allows us to quantify the reduction in departure metering benefits due to errors in EOBT information. The analysis reveals that the benefits reduce significantly due to EOBT uncertainty which has important implications for future departure metering applications, such as through the Terminal Flight Data Manager (TFDM) platform.United States. Federal Aviation Administration (Air Force Contract No. FA8721-05-C-0002)United States. Federal Aviation Administration (Air Force Contract No. FA8702-15-D-0001