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Recent Submissions

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Multiple populations in Globular Clusters from multi-wavelength HST photometry
(2016) Milone, A. P.
Recent papers, based on Hubble Space Telescope (HST) multi-wavelength photometry, have dramatically changed the traditional view of the color-magnitude diagram (CMD) of globular clusters (GCs). Appropriate combination of ultraviolet, visual, and near infrared (NIR) photometry have revealed multiple stellar populations along the entire CMD, from the bottom of the main sequence (MS) up to the the sub-giant (SGB), the red-giant branch (RGB) and even along the horizontal-branch (HB). In this paper I will use NGC2808 as a prototype to illustrate the typical features of the multiple populations in GCs and to get information on their chemical composition.
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Approximating sampled-data systems with applications to digital redesign
(2002) Yamamoto, Yutaka; Anderson, Brian D.O.; Nagahara, Masaaki
Despite the existence of methods for a direct optimal design of sampled-data control systems, it is often desired to approximate sampled-data systems with discrete-time ones. This occurs frequently in the context of digital redesign, in which one retains intuition in the continuous-time context. This paper investigates and gives conditions under which such a method works. Under some conditions, we guarantee that fast-sampling approximation works well for H∞ sampled-data design, and give an estimate for such an upsampling factor. As an application, we propose a new method for obtaining an FIR controller (possibly with first-order approximation). A comparison is made with an existing method.
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Characterization of aggregate interference in arbitrarily-shaped underlay cognitive networks
(2014) Guo, Jing; Durrani, Salman; Zhou, Xiangyun
This paper characterizes the aggregate interference at the primary user (PU) due to M secondary users (SUs) in an underlay cognitive network, where appropriate SU activity protocols are employed in order to limit the interference generated by the SUs. Different from prior works, we assume that the PU can be located anywhere inside an arbitrarily-shaped convex network region. Using the moment generating function (MGF) of the interference from a random SU, we derive general expressions for the n-th moment and the n-th cumulant of the aggregate interference for guard zone and multiple-threshold SU activity protocols. Using the cumulants, we study the convergence of the distribution of the aggregate interference to a Gaussian distribution. In addition, we compare the well-known closed-form distributions in the literature to approximate the complementary cumulative distribution function (CCDF) of the aggregate interference. Our results show that care must be undertaken in approximating the aggregate interference as a Gaussian distribution, even for a large number of SUs, since the convergence is not monotonie in general. In addition, the shifted lognormal distribution provides the overall best CCDF approximation, especially in the distribution tail region, for arbitrarily-shaped network regions.
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Reconstructing Australian boriginal governance by systems design
(2009-05-01) Radoll, Peter
Information technology and systems design approach are expected to offer a solution to the storage, distribution, and retrieval of Australian Aboriginal traditional knowledge through databases and web technologies. The database needs to be administered by a single individual who is responsible for providing access to the data. The model is different from the aboriginal community governance and needs to be addressed in the system design approach. The incompatibility of aboriginal traditions and information technology need to be understood to understand the distinction between them. Information technology design needs to signify the Aboriginal communities to ensure that their culture is preserved without introducing any changes.
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Enhancement of multiphoton photoluminescence with resonant metastructures
(2022) Tonkaev, P.; Fan, Y.; Wang, Y.; Han, J.; Zalogina, A.; Tripathi, A.; Lee, H. C.; Park, H. G.; Makarov, S.; Kruk, S.; Song, Q.; Xiao, S.; Kivshar, Y.
Multiphoton photoluminescence is a fundamentally important nonlinear process applied in microfabrication, data storage, and biological imaging. In general, nonlinear processes are much weaker compared with linear ones. We have studied multiphoton photoluminescence in perovskite metasurface and single AlGaAs nanoresonator and achieved significant enhancement in the vicinity of the Mie resonances.