Optimal circular flight of multiple UAVs for target tracking in urban areas

This work is an extension of our previous result in which a novel single-target tracking algorithm for fixed-wing UAVs (Unmanned Air Vehicles) was proposed. Our previous algorithm firstly finds the centre of a circular flight path, rc, over the interested ground target which maximises the total chance of keeping the target inside the camera field of view of UAVs, , while the UAVs fly along the circular path. All the UAVs keep their maximum allowed altitude and fly along the same circle centred at rc with the possible minimum turn radius of UAVs. As discussed in [1,4], these circular flights are highly recommended for various target tracking applications especially in urban areas, as for each UAV the maximum altitude flight ensures the maximum visibility and the minimum radius turn keeps the minimum distance to the target at the maximum altitude. Assuming a known probability distribution for the target location, one can quantify , which is incurred by the travel of a single UAV along an arbitrary circle, using line-of-sight vectors. From this observation, (the centre of) an optimal circle among numerous feasible ones can be obtained by a gradient-based search combined with random sampling, as suggested in [1]. This optimal circle is then used by the other UAVs jointly tracking the same target. As the introduction of multiple UAVs may minimise further, the optimal spacing between the UAVs can be naturally considered. In [1], a typical line search method is suggested for this optimal spacing problem. However, as one can easily expect, the computational complexity of this search method may undesirably increase as the number of UAVs increases. The present work suggests a remedy for this seemingly complex optimal spacing problem. Instead of depending on time-consuming search techniques, we develop the following algorithm, which is computationally much more efficient. Firstly, We calculate the distribution (x), where x is an element of , which is the chance of capturing the target by one camera along . Secondly, based on the distribution function, (x), find separation angles between UAVs such that the target can be always tracked by at least one UAV with a guaranteed probabilistic measure. Here, the guaranteed probabilistic measure is chosen by taking into account practical constraints, e.g. required tracking accuracy and UAVs' minimum and maximum speeds. Our proposed spacing scheme and its guaranteed performance are demonstrated via numerical simulations

Self-tuning of cosmological constant and exit from inflation

I review the recent 5D self-tuning solutions of the cosmological constant problem, and try to unify two cosmological constant problems within the framework of the self-tuning solutions. One problem, the large cosmological constant needed for inflation, is interpreted by starting with the parameters allowing only the dS vacuum, and the vanishing cosmological constant at a true vacuum is realized by changing parameters by exit from inflation at the brane such that the self-tuning solution is allowed.Comment: Latex file of 8 pages, including 2 figures. Talk presented at COSPA-03, Taipei, Taiwan, Nov. 13-15, 200

Pulsar Velocity with Three-Neutrino Oscillations in Non-adiabatic Processes

We have studied the position dependence of neutrino energy on the Kusenko-Segr\`{e} mechanism as an explanation of the proper motion of pulsars. The mechanism is also examined in three-generation mixing of neutrinos and in a non-adiabatic case. The position dependence of neutrino energy requires the higher value of magnetic field such as $B\sim 3\times 10^{15}$ Gauss in order to explain the observed proper motion of pulsars. It is shown that possible non-adiabatic processes decrease the neutrino momentum asymmetry, whereas an excess of electron neutrino flux over other flavor neutrino fluxes increases the neutrino momentum asymmetry. It is also shown that a general treatment with all three neutrinos does not modify the result of the two generation treatment if the standard neutrino mass hierarchy is assumed.Comment: 8 pages, REVTEX, no figure

The EnTrak system : supporting energy action planning via the Internet

Recent energy policy is designed to foster better energy efficiency and assist with the deployment of clean energy systems, especially those derived from renewable energy sources. To attain the envisaged targets will require action at all levels and effective collaboration between disparate groups (e.g. policy makers, developers, local authorities, energy managers, building designers, consumers etc) impacting on energy and environment. To support such actions and collaborations, an Internet-enabled energy information system called 'EnTrak' was developed. The aim was to provide decision-makers with information on energy demands, supplies and impacts by sector, time, fuel type and so on, in support of energy action plan formulation and enactment. This paper describes the system structure and capabilities of the EnTrak system

The Dialectics of Oriental Images in American Trade Cards

A late nineteenth-century trade card, or a color-printed circulating advertisement, touts Shepherd and Doyle\u27s new Celluloid waterproof collars, cuffs and shirt bosoms (Fig. 1).1 These economical, durable, and handsome clothing items require less starching and washing, and so remove the need for Chinese laundries. The text on the reverse side includes directions on how to remove yellow stains, and the image enacts a kind of literal version of this removal. The slovenly laundryshop (the clothes overflowing the basket, the linens hung up askew, the steaming basins), the mix-and-match, gender-ambiguous garments of the workers, and their thin, slouching bodies all participate in the racist stereotype of Asians as dirty, effeminate and alien others. The caption proclaims the product to be The Last Invention ; the last indicates finality, both in terms of modernity as the final stage of history and of a solution to the problem of unwanted immigrants. A group of Chinese male laundry-workers are so taken aback by this product that their pigtails stand in erect consternation. Their reaction stems both from the realization that they must return to China because their services have become unnecessary as well as from pure awe at the invention itself; in both cases, the scenario and its appeal apparently rely on these acts of recognition by the Chinese characters. Furthermore, the advertisement\u27s status as such - merely advertisement - hides the illogicality of the celluloid salesman\u27s presence in the laundry at all. The salesman, wearing a garish plaid suit and a bowler hat, appears to be one of those traveling salesmen who might peddle patent medicines, yet he bears the product eliciting such awe and consternation. Rather than selling the product to the Chinese workers, he appears simply to be taking gratuitous pleasure in introducing the workers to the agent of their impending misfortunes

The Unity of the Virtues in a Missionary Key

The thesis of the unity of the virtues—one must possess all of the virtues to possess even one of them—was upheld in different forms by Plato, Aristotle, Augustine, and Aquinas. However, contemporary moralists almost universally decry this thesis as distorting the nature of virtue as it is materialized in the lives and actions of ordinary people. Unfortunately, academic discourse regarding the unity of the virtues has tended to be either entirely theoretical or narrowly limited to particular individuals or groups as “test cases” regarding the validity of the thesis. It is both significant and reinvigorating, therefore, that in his apostolic exhortation, , Pope Francis evokes the thesis of the unity Evangelii gaudium of the virtues as pivotal to the task of evangelization. The purpose of the current essay is to reevaluate the merit and practical applicability of the unity of the virtues in light of the “missionary option” as proposed by Pope Francis

Disassortativity of random critical branching trees

Random critical branching trees (CBTs) are generated by the multiplicative branching process, where the branching number is determined stochastically, independent of the degree of their ancestor. Here we show analytically that despite this stochastic independence, there exists the degree-degree correlation (DDC) in the CBT and it is disassortative. Moreover, the skeletons of fractal networks, the maximum spanning trees formed by the edge betweenness centrality, behave similarly to the CBT in the DDC. This analytic solution and observation support the argument that the fractal scaling in complex networks originates from the disassortativity in the DDC.Comment: 3 pages, 2 figure