L. Delgado

Requirements, Issues, and Challenges for Sense and Avoid in Unmanned Aircraft Systems

The sense and avoid capability is one of the greatest challenges that has to be addressed to safely integrate unmanned aircraft systems into civil and nonsegregated airspace. This paper gives a review of existing regulations, recommended practices, and standards in sense and avoid for unmanned aircraft systems. Gaps and issues are identified, as are the different factors that are likely to affect actual sense and avoid requirements. It is found that the operational environment (flight altitude, meteorological conditions, and class of airspace) plays an important role when determining the type of flying hazards that the unmanned aircraft system might encounter. In addition, the automation level and the data-link architecture of the unmanned aircraft system are key factors that will definitely determine the sense and avoid system requirements. Tactical unmanned aircraft, performing similar missions to general aviation, are found to be the most challenging systems from an sense and avoid point of view, and further research and development efforts are still needed before their seamless integration into nonsegregated airspace

En Route Speed Reduction Concept for Absorbing Air Traffic Flow Management Delays

This paper proposes an en route speed reduction to complement current ground delay practices in air traffic flow management. Given a nominal cruise speed, there exists a bounded range of speeds that allows aircraft to fly slower with the same or lower fuel consumption than the nominal flight. Therefore, flight times are increased and delay can be partially performed in the air, at no extra fuel cost for the operator. This concept has been analyzed in an initial feasibility study, computing the maximum amount of delay that can be performed in the air in some representative flights. The impact on fuel consumption has been analyzed, and two scenarios are proposed: the flight fuel remains the same as in the nominal flight, and some extra fuel allowance is permitted in order to face uncertainties. Results show significant values of airborne delay that may be useful in many situations, with the exception of short hauls where airborne delay may be too short. If cruise altitude is changed, the amount of airborne delay increases, since changes in cruise speed modify the optimal flight altitudes. From the analyzed flights, a linear dependency is found relating the airborne delay with the amount of extra fuel allowance.

Silver deposition on titanium surface by electrochemical anodizing process reduces bacterial adhesion of Streptococcus sanguinis and Lactobacillus salivarius

OBJECTIVES The aim of this study was to determine the antibacterial properties of silver-doped titanium surfaces prepared with a novel electrochemical anodizing process. MATERIAL AND METHODS Titanium samples were anodized with a pulsed process in a solution of silver nitrate and sodium thiosulphate at room temperature with stirring. Samples were processed with different electrolyte concentrations and treatment cycles to improve silver deposition. Physicochemical properties were determined by X-ray photoelectron spectroscopy, contact angle measurements, white-light interferometry, and scanning electron microscopy. Cellular cytotoxicity in human fibroblasts was studied with lactate dehydrogenase assays. The in vitro effect of treated surfaces on two oral bacteria strains (Streptococcus sanguinis and Lactobacillus salivarius) was studied with viable bacterial adhesion measurements and growth curve assays. Nonparametric statistical Kruskal-Wallis and Mann-Whitney U-tests were used for multiple and paired comparisons, respectively. Post hoc Spearmans correlation tests were calculated to check the dependence between bacteria adhesion and surface properties. RESULTS X-ray photoelectron spectroscopy results confirmed the presence of silver on treated samples and showed that treatments with higher silver nitrate concentration and more cycles increased the silver deposition on titanium surface. No negative effects in fibroblast cell viability were detected and a significant reduction on bacterial adhesion in vitro was achieved in silver-treated samples compared with control titanium. CONCLUSIONS Silver deposition on titanium with a novel electrochemical anodizing process produced surfaces with significant antibacterial properties in vitro without negative effects on cell viability.

Analysis of the misfit of dental implant-supported prostheses made with three manufacturing processes.

STATEMENT OF PROBLEM The microgap between implant components has been associated with complications such as screw loosening or adverse biologic responses. PURPOSE The purpose of this study was to quantify the microroughness of the mating surfaces of implant components manufactured with different processes, to quantify the microgap between implant components, and to determine whether a correlation exists between microroughness and the microgap. MATERIAL AND METHODS Nine dental implants with a standard external connection were paired with 3 milled, 3 cast, and 3 sintered compatible cobalt-chromium alloy abutments. The abutment surface was examined, and the roughness parameter Sz was measured by using a white-light interferometric microscope at ×10 to ×100 magnification. The abutment surface and the microgap of the implant-abutment connection were observed with scanning electron microscopy, and the microgap width was quantified from micrographs made of each implant-abutment pair. The mean and standard deviation of roughness and microgap were evaluated. A 1-way ANOVA (α=.05) was used to assess the influence of the manufacturing process on roughness and microgap. The Pearson correlation was used to check dependence between roughness and microgap. RESULTS The milled abutments possessed a connection geometry with defined edges and a mean roughness of 29 μm, sintered abutments showed a blurred but functional connection with a roughness of 115 μm, and cast abutments showed a connection with a loss of axial symmetry and a roughness of 98 μm. A strong correlation was found between the roughness values on the mating surfaces and the microgap width. CONCLUSIONS The milled components were smoother than the cast or sintered components. A correlation was found between surface roughness and microgap width.

An Assessment for UAS depart and approach operations

Unmanned Aerial Systems (UAS) have great potential to be used in a wide variety of civil applications such as environmental applications, emergency situations, surveillance tasks and more. The development of Flight Control Systems (FCS) coupled with the availability of other Commercial Off-The Shelf (COTS) components is enabling the introduction of UAS into the civil market. The sophistication of existing FCS is also making these systems accessible to end users with little aeronautics expertise. However, much work remains to be done to deliver systems that can be properly integrated in standard aeronautical procedures used by manned aviation. In previous research advances have been proposed in the flight plan capabilities by offering semantically much richer constructs than those present in most current UAS autopilots. The introduced flight plan is organized as a set of stages, each one corresponding to a different flight phase. Each stage contains a structured collection of legs inspired by current practices in Area Navigation (RNAV). However, the most critical parts of any flight, the depart and approach operations in an integrated airspace remain mostly unexplored. This paper introduces an assessment of both operations for UAS operating in VFR and IFR modes. Problems and potential solutions are proposed, as well as an automating strategy that should greatly reduce pilot workload. Although the

Departure and Approach procedures for Unammed Aircraft Systems in a Visual-Flight-Rule Environment

This paper assesses the departure and approach operations of unmanned aircraft systems in one of the most challenging scenarios: flying under visual flight rules. Inspired by some existing procedures for (manned) general aviation, some automatic and predefined procedures for unmanned aircraft systems are proposed. Hence, standardized paths to specific waypoints close to the airport are defined for departure operations, just before starting the navigation phase. Conversely, and for the approach maneuvers, a first integration into a holding pattern near the landing runway (ideally, above it) is foreseen, followed by a standard visual-flight-rule airfield traffic pattern. This paper discuses the advantages of these operations, which aim to minimize possible conflicts with other existing aircraft while reducing the pilot-in-command workload. Finally, some preliminary simulations are shown in which these procedures have been successfully tested with simulated surrounding traffic.

Differential neuronal and glial behavior on flat and micro patterned chitosan films

Chitosan is a biodegradable natural polysaccharide that has been widely studied for regenerative purposes in the central nervous system. In this study we assessed the in vitro glial and neuronal cells response to chitosan either flat or patterned with grooves in the micrometric range. Chitosan demonstrated to be a good substrate for the attachment and growth of both neurons and glial cells. Chitosan micropatterns promoted glial cell maturation, suggesting astroglial activation. Nevertheless, those mature/reactive glial cells were permissive for axonal growth. Axons aligned and organized along the patterned grooves and the size of the linear topographic patterns is also affecting neurite and cell response. Patterns with 10μm width induced fasciculation of axons, which can be useful for CNS tissue engineering substrates when precise orientation of the axonal outgrowth is desired.

UAS pilot support for departure, approach and airfield operations

Unmanned Aerial Systems (UAS) have great potential to be used in a wide variety of civil applications such as environmental applications, emergency situations, surveillance tasks and more. The development of Flight Control Systems (FCS) coupled with the availability of other Commercial Off-The Shelf (COTS) components is enabling the introduction of UAS into the civil market. The sophistication of existing FCS is also making these systems accessible to end users with little aeronautics expertise. However, much work remains to be done to deliver systems that can be properly integrated in standard aeronautical procedures used by manned aviation.

En-route Speed Reduction for the Mangement of ATFM Delays

In this paper a new concept aimed at better dealing with delays caused by regulations is presented. Inspired in future 4D trajectories, where a time constraint can be applied at each way-point, it is proposed to spread the total delay imposed by a regulation over the trajectory that goes from the departing airport to the regulated airspace. Given a nominal cruise speed, there exist a set of possible lower speeds that allow a longer flight (and then, a cumulative flight delay) with the same or less fuel consumption if compared with the nominal situation. In this way, the aircraft that has been delayed can consider to take-off on time and loose this time by flying slower and requiring the same or less fuel than initially planed. Besides the positive environmental impact, the airliner can bet that finally the regulation at the congested airspace may be not applied and being the departure on time, the delay can be absorbed more easily in flight with a minimal or null fuel consumption increase. Finally, this concept is applied to some example flights.

Agent Based Model for Hub Operations Cost Reduction

Hub operations are complex as not only flight delay but also passengers’ connections need to be managed to minimise airlines’ operating costs. When facing delayed aircraft, the aircraft operator can speed up incoming flights to the hub to reduce the delay and/or actively delay outbound flights to wait for passengers that would miss their connection, these outbound flights can be speeded up on their turn. This optimisation cannot be carried out in isolation as the system has limited resources that need to be allocated in concurrence with other flights. For this reason, a negotiation process is required. In this context, the use of agent based modelling techniques allows us to describe the behaviour of the different stakeholders in a smooth manner and to analyse complex interactions and the impact of local decisions at network level.