26,258 research outputs found

    Coupling of phonons and spin waves in triangular antiferromagnet

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    We investigate the influence of the spin-phonon coupling in the triangular antiferromagnet where the coupling is of the exchange-striction type. The magnon dispersion is shown to be modified significantly at wave vector (2pi,0) and its symmetry-related points, exhibiting a roton-like minimum and an eventual instability in the dispersion. Various correlation functions such as equal-time phonon correlation, spin-spin correlation, and local magnetization are calculated in the presence of the coupling.Comment: 6 pages, 5 figures; references added, minor text revisions, submitted to PR

    Recognition of partially occluded threat objects using the annealed Hopefield network

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    Recognition of partially occluded objects has been an important issue to airport security because occlusion causes significant problems in identifying and locating objects during baggage inspection. The neural network approach is suitable for the problems in the sense that the inherent parallelism of neural networks pursues many hypotheses in parallel resulting in high computation rates. Moreover, they provide a greater degree of robustness or fault tolerance than conventional computers. The annealed Hopfield network which is derived from the mean field annealing (MFA) has been developed to find global solutions of a nonlinear system. In the study, it has been proven that the system temperature of MFA is equivalent to the gain of the sigmoid function of a Hopfield network. In our early work, we developed the hybrid Hopfield network (HHN) for fast and reliable matching. However, HHN doesn't guarantee global solutions and yields false matching under heavily occluded conditions because HHN is dependent on initial states by its nature. In this paper, we present the annealed Hopfield network (AHN) for occluded object matching problems. In AHN, the mean field theory is applied to the hybird Hopfield network in order to improve computational complexity of the annealed Hopfield network and provide reliable matching under heavily occluded conditions. AHN is slower than HHN. However, AHN provides near global solutions without initial restrictions and provides less false matching than HHN. In conclusion, a new algorithm based upon a neural network approach was developed to demonstrate the feasibility of the automated inspection of threat objects from x-ray images. The robustness of the algorithm is proved by identifying occluded target objects with large tolerance of their features

    The Global Turn in Nationalism: The USA as a Battleground for Hinduism and Hindu Nationalism

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    Hindu nationalism operates on a global scale today. Evinced by the transnational networks of the Sangh Parivar and the replication of strategies such as amending textbooks and patriotic rewriting of history, politics and discourse of Hindu nationalism are not solely contained to the territorial boundary of the nation. In this globalized battle for and against Hindu nationalism, the United States of America serves as an important site. In light of this, this article puts together existing scholarship on diasporic Hindu nationalism with late nineteenth-and early twentieth-century deterritorial history of Indian nationalism to present a broader framework for historicizing Indian activism in the US. It argues that while long-distance Hindu nationalism in the US cannot be traced before the 1970s, examining the early experiences of Indian activists in the US offers useful insights with which to evaluate the ongoing battles of Hindu nationalism in the US and opens another field of enquiry: Hindutva’s counterpublic

    Flight simulator for hypersonic vehicle and a study of NASP handling qualities

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    The research goal of the Human-Machine Systems Engineering Group was to study the existing handling quality studies in aircraft with sonic to supersonic speeds and power in order to understand information requirements needed for a hypersonic vehicle flight simulator. This goal falls within the NASA task statements: (1) develop flight simulator for hypersonic vehicle; (2) study NASP handling qualities; and (3) study effects of flexibility on handling qualities and on control system performance. Following the above statement of work, the group has developed three research strategies. These are: (1) to study existing handling quality studies and the associated aircraft and develop flight simulation data characterization; (2) to develop a profile for flight simulation data acquisition based on objective statement no. 1 above; and (3) to develop a simulator and an embedded expert system platform which can be used in handling quality experiments for hypersonic aircraft/flight simulation training
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