FMS for Unmanned Aerial Systems: HMI Issues and New Interface Solutions

To integrate UASs in the NAS, an improvement in navigation, planning, communication and 4D trajectory control capabilities is mandatory. A way to obtain this enhance is to adopt a Flight Management System. A FMS for an UAS has some differences with respect to one for a manned aircraft, in terms of architecture and performed functions. In particular, from HMI point of view, the specific UAS human factor issues shall be added to the current manned FMS interface lacks. Starting from these considerations, a new FMS HMI for the Alenia Aeronautica TCS has been developed, using as data entry devices two touch screens.     

Web accessibility guideline aggregation for older users and its validation

Web site-evaluation methodologies and validation engines take the view that all accessibility guidelines must be met to gain compliance. Problems exist in this regard, as contradictions within the rule set may arise, and the type of impairment or its severity is not isolated. The Barrier Walkthrough (BW) method goes someway to addressing these issues, by enabling barrier types derived from guidelines to be applied to different user categories such as motor or visual impairment, etc. However, the problem remains of combinatorial explosion of possibilities when one has to consider users with multiple disabilities. In this paper, a simple set theory operation is used to create a validation scheme for older users by aggregating barrier types specific to motor impaired and low-vision users, thereby creating a new “older users” category from the results of this set union. To evaluate the feasibility and validity of this aggregation approach, two BW experiments were conducted. The first experiment evaluated the aggregated results by focusing on quality attributes and showed that aggregation generates data whose quality is comparable to the original one. However, this first experiment could not test for validity, as the older users category was not included. To remedy this deficiency, another BW experiment was conducted with expert judges who evaluated a web page in the context of older users. In this second experiment, it was found that there is no significant difference between the aggregated and the manually evaluated (by experts) barrier scores, and that the same barriers are identified using experts and aggregation, even though there are differences in how severity scores are distributed. From these results, it is concluded that the aggregation of barriers is a viable alternative to expert evaluation, when the target of that aggregation could not be evaluated manually or it would not be feasible to do so. It is also argued that aggregation is a technique that can be used in combination with other evaluation methods, like user testing or subjective assessments.     

A Survey of Airworthiness and Certification for UAS

The Italian SMAT project is a civilian program supported by Piemonte Region developed for the territorial monitoring and surveillance and for the prevention of natural hazards. In a different way from the previous surveillance programs, the SMAT project is based on the use of several unmanned platforms that are able to cooperate through ground coordination and control station. The flight in non-segregated airspace, needed in order to accomplish the territorial monitoring mission, is a main issue to be investigated and defined, because of the current lack of a common consensus and agreement on the regulations of UAS. The present work outlines the international initiatives that deal with the development of the regulatory framework on airworthiness and certification of UAS and their potential impact on the SMAT project.     

A graph-based approach for extracting terminological properties from information sources with heterogeneous formats

The problem of handling both the integration and the cooperation of a large number of information sources characterised by heterogeneous representation formats is a challenging issue. In this context, a central role can be played by the knowledge about the semantic relationships holding between concepts belonging to different information sources (intersource properties). In this paper, we propose a semiautomatic approach for extracting two kinds of intersource properties, namely synonymies and homonymies, from heterogeneous information sources. In order to carry out the extraction task, we introduce both a conceptual model, for representing involved sources, and a metrics, for measuring the strength of the semantic relationships holding among concepts represented within the same source.     

Minority Games, Local Interactions, and Endogenous Networks

We study a local version of the Minority Game, where agents are placed on the nodes of a directed graph. Agents care about being in the minority of the group of agents they are currently linked to and employ myopic best-reply rules to choose their next-period state. We show that, in this benchmark case, the smaller the size of local networks, the larger long-run population-average payoffs. We then explore the collective behavior of the system when agents can: (i) assign weights to each link they hold and modify them over time in response to payoff signals; (ii) delete badly performing links (i.e., opponents) and replace them with randomly chosen ones. Simulations suggest that, when agents are allowed to weigh links but cannot delete/replace them, the system self-organizes into networked clusters that attain very high payoff values. These clustered configurations are not stable and can easily be disrupted, generating huge subsequent payoff drops. If, however, agents can (and are sufficiently willing to) discard badly performing connections, the system quickly converges to stable states where all agents get the highest payoff, independently of the size of the networks initially in place.JEL Classification:s C72, C73.     

Assessing the potential of SeaWiFS and MODIS for estimating chlorophyll concentration in turbid productive waters using red and near-infrared bands

Bio-optical algorithms for remote estimation of chlorophyll-a concentration (Chl) in case-1 waters exploit the upwelling radiation in the blue and green spectral regions. In turbid productive waters other constituents, that vary independently of Chl, absorb and scatter light in these spectral regions. As a consequence, the accurate estimation of Chl in turbid productive waters has so far not been feasible from satellite sensors. The main purpose of this study was to evaluate the extent to which near-infrared (NIR) to red reflectance ratios could be applied to the Sea Wide Field-of-View Sensor (SeaWiFS) and the Moderate Imaging Spectrometer (MODIS) to estimate Chl in productive turbid waters. To achieve this objective, remote-sensing reflectance spectra and relevant water constituents were collected in 251 stations over lakes and reservoirs with a wide variability in optical parameters (i.e. 4 ≤ Chl ≤ 240 mg m^− 3; 18 ≤ Secchi disk depth ≤ 308 cm). SeaWiFS and MODIS NIR and red reflectances were simulated by using the in-situ hyperspectral data. The proposed algorithms predicted Chl with a relative random uncertainty of approximately 28% (average bias between − 1% and − 4%). The effects of reflectance uncertainties on the predicted Chl were also analyzed. It was found that, for realistic ranges of R_rs uncertainties, Chl could be estimated with a precision better than 40% and an accuracy better than ± 35%. These findings imply that, provided that an atmospheric correction scheme specific for the red-NIR spectral region is available, the extensive database of SeaWiFS and MODIS images could be used to quantitatively monitor Chl in turbid productive waters.     

Rate Monotonic vs. EDF: Judgment Day

Since the first results published in 1973 by Liu and Layland on the Rate Monotonic (RM) and Earliest Deadline First (EDF) algorithms, a lot of progress has been made in the schedulability analysis of periodic task sets. Unfortunately, many misconceptions still exist about the properties of these two scheduling methods, which usually tend to favor RM more than EDF. Typical wrong statements often heard in technical conferences and even in research papers claim that RM is easier to analyze than EDF, it introduces less runtime overhead, it is more predictable in overload conditions, and causes less jitter in task execution.Since the above statements are either wrong, or not precise, it is time to clarify these issues in a systematic fashion, because the use of EDF allows a better exploitation of the available resources and significantly improves system's performance.This paper compares RM against EDF under several aspects, using existing theoretical results, specific simulation experiments, or simple counterexamples to show that many common beliefs are either false or only restricted to specific situations.     

On the design of efficient ATM routing schemes

In this paper we deal with the problem of designing virtual path layouts in ATM networks when the hop-count is given and the load has to be minimized. We first prove a lower bound for networks with arbitrary topology and arbitrary set of connection requests. This result is then applied to derive lower bounds for the following settings: (i) one-to-all (one node has to be connected to all other nodes of the network) in arbitrary networks; (ii) all-to-all (each node has to be connected to all other nodes in the network) in several classes of networks, including planar and k-separable networks and networks of bounded genus. We finally study the all-to-all setting on two-dimensional meshes and we design a virtual path layout for this problem. When the hop-count and the network degree are bounded by constants, our results show that the upper bounds proposed in this paper for the one-to-all problem in arbitrary networks and for the all-to-all problem in two-dimensional mesh networks are asymptotically optimal. Moreover, the general lower bound shows that the algorithm proposed in Gerstel (Ph.D. Thesis, Technion-Haifa, Israel, 1995) for the all-to-all problem in k-separable networks is also asymptotically optimal. The upper bound for mesh networks also shows that the lower bound presented in this paper for the all-to-all problem in planar networks is asymptotically tight.     

A design flow for supporting component-based software development in multiprocessor real-time systems

Component-based software development established as an effective technique to cope with the increasing complexity of modern computing systems. In the context of real-time systems, the M-BROE framework has been recently proposed to efficiently support component-based development of real-time applications on multiprocessor platforms in the presence of shared resources. The framework relies on a two-stage approach where software components are first partitioned upon a virtual multiprocessor platform and are later integrated upon the physical platform by means of component interfaces that abstract from the internal details of the applications. This work presents a complete design flow for the M-BROE framework. Starting from a model of software components, a first method is proposed to partition applications to virtual processors and perform a synthesis of multiple component interfaces. Then, a second method is proposed to support the integration of the components by allocating virtual processors to physical processors. Both methods take resource sharing into account. Experimental results are also presented to evaluate the proposed methodology.