Motion Planning for Optimal Information Gathering in Opportunistic Navigation Systems

Motion planning for optimal information gathering in an opportunistic navigation (OpNav) environment is considered. An OpNav environment can be thought of as a radio frequency signal landscape within which a receiver locates itself in space and time by extracting information from ambient signals of opportunity (SOPs). The receiver is assumed to draw only pseudorange-type observations from the SOPs, and such observations are fused through an estimator to produce an estimate of the receiver’s own states. Since not all SOP states in the OpNav environment may be known a priori, the receiver must estimate the unknown SOP states of interest simultaneously with its own states. In this work, the following problem is studied. A receiver with no a priori knowledge about its own states is dropped in an unknown, yet observable, OpNav environment. Assuming that the receiver can prescribe its own trajectory, what motion planning strategy should the receiver adopt in order to build a high-fidelity map of the OpNav signal landscape, while simultaneously localizing itself within this map in space and time? To answer this question, first, the minimum conditions under which the OpNav environment is fully observable are established, and the need for receiver maneuvering to achieve full observability is highlighted. Then, motivated by the fact that not all trajectories a receiver may take in the environment are equally beneficial from an information gathering point of view, a strategy for planning the motion of the receiver is proposed. The strategy is formulated in a coupled estimation and optimal control framework of a gradually identified system, where optimality is defined through various information-theoretic measures. Simulation results are presented to illustrate the improvements gained from adopting the proposed strategy over random and pre-defined receiver trajectories.Aerospace Engineering and Engineering Mechanic

The Price of Anarchy in Active Signal Landscape Map Building

Multiple receivers with a priori knowledge about their own initial states are assumed to be dropped in an unknown environment comprising multiple signals of opportunity (SOPs) transmitters. The receivers draw pseudorange observations from the SOPs. The receivers’ objective is to build a high-fidelity signal landscape map of the environment, which would enable the receivers to navigate accurately with the aid of the SOPs. The receivers could command their own maneuvers and such commands are computed so to maximize the information gathered about the SOPs in a greedy fashion. Several information fusion and decision making architectures are possible. This paper studies the price of anarchy in building signal landscape maps to assess the degradation in the map quality should the receivers produce their own maps and make their own maneuver decisions versus a completely centralized approach. In addition, a hierarchical architecture is proposed in which the receivers build their own maps and make their own decisions, but share relevant information. Such architecture is shown to produce maps of comparable quality to the completely centralized approach.Aerospace Engineering and Engineering Mechanic

A Graphical Approach to GPS Software-Defined Receiver Implementation

Global positioning system (GPS) software-defined receivers (SDRs) offer many advantages over their hardwarebased counterparts, such as flexibility, modularity, and upgradability. A typical GPS receiver is readily expressible as a block diagram, making a graphical approach a natural choice for implementing GPS SDRs. This paper presents a real-time, graphical implementation of a GPS SDR, consisting of two modes: acquisition and tracking. The acquisition mode performs a twodimensional fast Fourier transform (FFT)-based search over code offsets and Doppler frequencies. The carrier-aided code tracking mode consists of the following main building blocks: correlators, code and carrier phase detectors, code and carrier phase filters, a code generator, and a numerically-controlled oscillator. The presented GPS SDR provides an abstraction level that enables future research endeavors.Aerospace Engineering and Engineering Mechanic

Tightly-Coupled Opportunistic Navigation for Deep Urban and Indoor Positioning

A strategy is presented for exploiting the frequency stability, transmit location, and timing information of ambient radio-frequency “signals of opportunity” for the purpose of navigating in deep urban and indoor environments. The strategy, referred to as tightly-coupled opportunistic navigation (TCON), involves a receiver continually searching for signals from which to extract navigation and timing information. The receiver begins by characterizing these signals, whether downloading characterizations from a collaborative online database or performing characterizations on-the-fly. Signal observables are subsequently combined within a central estimator to produce an optimal estimate of position and time. A simple demonstration of the TCON strategy focused on timing shows that a TCONenabled receiver can characterize and use CDMA cellular signals to correct its local clock variations, allowing it to coherently integrate GNSS signals beyond 100 seconds.Aerospace Engineering and Engineering Mechanic

Collaborative Opportunistic Navigation

Aerospace Engineering and Engineering Mechanic

LoggerMan, a comprehensive logging and visualisation tool to capture computer usage

As we become increasingly dependent on our computers and spending a major part of our day interacting with these machines, it is becoming important for lifeloggers and human-computer interaction (HCI) researchers to capture this aspect of our life. In this paper, we present LoggerMan, a comprehensive logging tool to capture many aspects of our computer usage. It also comes with reporting capabilities to give insights to the data owner about his/her computer usage. By this work, we aim to fill the current lack of logging software in this domain, which would help us and other researchers as well to build data sets for HCI experiments and also to better understand computer usage patterns. Our tool is published online (loggerman.org) to be used freely by the community

Content & Watkins's account of natural axiomatizations

This paper briefly recounts the importance of the notion of natural axiomatizations for explicating hypothetico-deductivism, empirical significance, theoretical reduction, and organic fertility. Problems for the account of natural axiomatizations developed by John Watkins in Science and Scepticism and the revised account developed by Elie Zahar are demonstrated. It is then shown that Watkins's account can be salvaged from various counter-examples in a principled way by adding the demand that every axiom of a natural axiomatization should be part of the content of the theory being axiomatized. The crucial point here is that content cannot simply be identified with the set of logical consequences of a theory, but must be restricted to a proper subset of the consequence set. It is concluded that the revised Watkins account has certain advantages over the account of natural axiomatizations offered in Gemes (1993)

Extracción con disolventes del aceite de jojoba a partir de harina prensada de jojoba

The solvent extraction process of jojoba oil from the meal cake obtained after the mechanical pressing of jojoba seeds was studied. Commercial hexane and petroleum ether were used as solvents and the extraction was carried out at temperatures ranging from 30 to 55 °C using solvent-to-solid ratios, R between 2 and 15 L/kg. The equilibrium compositions of the solvent and solid phases were determined. Based on the equilibrium data, the partition coefficient or distribution ratio, D of the oil between both phases was estimated. Also, the number of extraction stages necessary to achieve a certain degree of oil recovery has been determined using different hexane-to-meal ratios. Jojoba oil was also tested for its physical and chemical properties including chemical composition, percentage fatty acid, peroxide value, flash point, fire point, pour point, refractive index, saponification and iodine values. The stability of jojoba oil during storage at room temperature and during heat treatment was also studied.Se ha estudiado el proceso de extracción con disolventes del aceite contenido en la harina residual del prensado mecánico de las semillas de jojoba. Como disolventes se han utilizado hexano técnico y éter de petróleo, habiéndose efectuado extracciones a temperaturas comprendidas entre 30 ºC y 55 ºC , con relaciones de disolvente a sólido, R, de entre 12 y 15 L/kg. Se han determinado las composiciones del extracto y del residuo sólido en el equilibrio y a partir de los datos de equilibrio, se ha estimado el coeficiente de partición o cociente de distribución, D, del aceite entre ambas fases. Asimismo, se ha determinado el número de etapas de extracción necesarias para conseguir un cierto grado de recuperación del aceite, utilizando diferentes relaciones entre hexano y harina. También se han determinado las propiedades físicas y químicas del aceite de jojoba, incluyendo la composición química, el porcentaje de ácidos grasos, el índice de peróxidos, el punto de inflamación, el punto de ignición, el punto de deslizamiento, el índice de refracción y los índices de saponificación y de yodo. Se ha estudiado asimismo la estabilidad del aceite durante su almacenamiento a temperatura ambiente y durante el calentamiento