Formation control of a group of micro aerial vehicles (MAVs)

Coordinated motion of Unmanned Aerial Vehicles (UAVs) has been a growing research interest in the last decade. In this paper we propose a coordination model that makes use of virtual springs and dampers to generate reference trajectories for a group of quadrotors. Virtual forces exerted on each vehicle are produced by using projected distances between the quadrotors. Several coordinated task scenarios are presented and the performance of the proposed method is verified by simulations

The nature of the artificial: augmenting Negrottian artificiality with neo-Whiteheadian naturality

In this paper, a theory of the artificial recently proposed by Negrotti (1999a, 1999b, 2001a, 2001b) is critically examined. First, a brief overview of this theory is presented. It is then argued that despite the merits of this scheme, principal of which are the self-evident simplicity of its conceptual foundations, its internal consistency (or theoretical coherence), and its possible overall correctness, it is, nonetheless, incomplete. This incompleteness is shown to arise as a direct consequence of the explicit affirmation of a number of problematic metaphysical assumptions about the nature (as essence or what-ness) of nature (as 'other' to the artificial). An attempt at resolving the problem of incompleteness by augmenting the Negrottian theory of artificiality with an alternative conception of nature (as 'other') grounded in Whiteheadian panexperientialism is made. It is shown that although panexperientialism provides an adequate framework for the conceptualisation of naturality, it does not provide a corresponding framework for artificiality, principally because it fails to adequately characterise the nature (as essence) of artifacts. In order to address this latter problem, it is argued that conventional Whiteheadian panexperientialism must be supplemented with a phenomenological account of artificing that describes the ontologically distinct manner in which artifacts come to be. An attempt at formulating such a 'neo-Whiteheadian' account grounded in the metaphysical thinking of Ladrière, Lee, and others is made. In closing, some implications of this alternative Whiteheadian conception of naturality and the attendant neo-Whiteheadian account of artifactuality for the project of "strong" artificiality (that is, the attempt to artifactually replicate natural phenomena) are briefly considered

Race: the difference that makes a difference

During the last two decades, critical enquiry into the nature of race has begun to enter the philosophical mainstream. The same period has also witnessed the emergence of an increasingly visible discourse about the nature of information within a diverse range of popular and academic settings. What is yet to emerge, however, is engagement at the interface of the two disciplines – critical race theory and the philosophy of information. In this paper, I shall attempt to contribute towards the emergence of such a field of enquiry by using a reflexive hermeneutic (or interpretative) approach to analyze the concept of race from an information-theoretical perspective, while reflexively analyzing the concept of information from a critical race-theoretical perspective. In order to facilitate a more concrete enquiry, the concept of information formulated by cyberneticist Gregory Bateson and the concept of race formulated by philosopher Charles W Mills will be placed at the centre of analysis. Crucially, both concepts can be shown to have a connection to the critical philosophy of Immanuel Kant, thereby justifying their selection as topics of examination on critical reflexive hermeneutic grounds

Decolonizing Information Narratives: Entangled Apocalyptics, Algorithmic Racism and the Myths of History

In what follows, some contemporary narratives about ‘the information society’ are interrogated from critical race theoretical and decolonial perspectives with a view to constructing a ‘counter-narrative’ purporting to demonstrate the embeddedness of coloniality—that is, the persistent operation of colonial logics—in such discourses

Transhumanism and/as Whiteness

Transhumanism is interrogated from critical race theoretical and decolonial perspectives with a view to establishing its ‘algorithmic’ relationship to historical processes of race formation (or racialization) within Euro-American historical experience. Although the Transhumanist project is overdetermined vis-à-vis its raison-d’être, it is argued that a useful way of thinking about this project is in terms of its relationship to the shifting phenomenon of ‘whiteness’. It is suggested that Transhumanism constitutes a techno-scientific response to the phenomenon of ‘White Crisis’ at least partly prompted by ‘critical’ posthumanist contestation of Eurocentrically-universal humanism

Spectral Singularities in the Surface Modes of a Spherical Gain Medium

We study the surface modes of a homogeneous spherical gain medium and provide a comprehensive analytic treatment of a special class of these modes that support spectral singularities. Because the latter have a divergent quality factor, we call them the singular gallery modes. We show that they can be excited using arbitrarily small amounts of gain, and as a result, the system lacks a lasing threshold, effectively. This shows that we can realize spectral singularities in the surface modes of extremely small spherical samples with modest amounts of gain. We also examine the possibility of exciting singular gallery modes with different wavelengths using the same amount of gain. This corresponds to the situation where the system undergoes simultaneous lasing at different wavelengths.Comment: 13 pages, 4 figures, 6 tables; to appear in Phys. Rev.

Spectral Singularities and Whispering Gallery Modes of a Cylindrical Gain Medium

Complex scattering potentials can admit scattering states that behave exactly like a zero-width resonance. Their energy is what mathematicians call a spectral singularity. This phenomenon admits optical realizations in the form of lasing at the threshold gain, and its time-reversal is responsible for antilasing. We study spectral singularities and whispering gallery modes (WGMs) of a cylindrical gain medium. In particular, we introduce a new class of WGMs that support a spectral singularity and, as a result, have a divergent quality factor. These singular gallery modes (SGMs) are excited only if the system has a positive gain coefficient, but typically the required gain is extremely small. More importantly given any amount of gain, there are SGMs requiring smaller gain than this amount. This means that, in principle, the system lacks a lasing threshold. Furthermore, the abundance of these modes allows for configurations where a particular value of the gain coefficient yields an effective excitation of two distant SGMs. This induces lasing at two different wavelengths.Comment: 12 pages, 6 figures, 3 tables; to appear in Phys. Rev.

Lasing Threshold Condition for Oblique TE and TM Modes, Spectral Singularities, and Coherent Perfect Absorption

We study spectral singularities and their application in determining the threshold gain coefficient $g^{(E/M)}$ for oblique transverse electric/magnetic (TE/TM) modes of an infinite planar slab of homogenous optically active material. We show that $g^{(E)}$ is a monotonically decreasing function of the incidence angle $\theta$ (measured with respect to the normal direction to the slab), while $g^{(M)}$ has a single maximum, $\theta_c$, where it takes an extremely large value. We identify $\theta_c$ with the Brewster's angle and show that $g^{(E)}$ and $g^{(M)}$ coincide for $\theta=0$ (normal incidence), tend to zero as $\theta\to 90^\circ$, and satisfy $g^{(E)}<g^{(M)}$ for $0<\theta<90^\circ$. We therefore conclude that lasing and coherent perfect absorption are always more difficult to achieve for the oblique TM waves and that they are virtually impossible for the TM waves with $\theta\approx\theta_c$. We also give a detailed description of the behavior of the energy density and the Poynting vector for spectrally singular oblique TE and TM waves. This provides an explicit demonstration of the parity-invariance of these waves and shows that the energy density of a spectrally singular TM wave with $\theta>\theta_c$ is smaller inside the gain region than outside it. The converse is true for the TM waves with $\theta<\theta_c$ and all TE waves.Comment: 14 pages, 3 tables, 7 figure