32,399 research outputs found
Spatial Identification Methods and Systems for RFID Tags
DisertaÄŤnĂ práce je zaměřena na metody a systĂ©my pro měřenĂ vzdálenosti a lokalizaci RFID tagĹŻ pracujĂcĂch v pásmu UHF. Ăšvod je vÄ›nován popisu souÄŤasnĂ©ho stavu vÄ›deckĂ©ho poznánĂ v oblasti RFID prostorovĂ© identifikace a struÄŤnĂ©mu shrnutĂ problematiky modelovánĂ a návrhu prototypĹŻ tÄ›chto systĂ©mĹŻ. Po specifikaci cĂlĹŻ disertace pokraÄŤuje práce popisem teorie modelovánĂ degenerovanĂ©ho kanálu pro RFID komunikaci. DetailnÄ› jsou rozebrány metody měřenĂ vzdálenosti a odhadu smÄ›ru pĹ™Ăchodu signálu zaloĹľenĂ© na zpracovánĂ fázovĂ© informace. Pro účely lokalizace je navrĹľeno nÄ›kolik scĂ©nářů rozmĂstÄ›nĂ antĂ©n. Modely degenerovanĂ©ho kanálu jsou simulovány v systĂ©mu MATLAB. VĂ˝znamná část tĂ©to práce je vÄ›nována konceptu softwarovÄ› definovanĂ©ho rádia (SDR) a specifikĹŻm jeho adaptace na UHF RFID, která vyuĹľitĂ běžnĂ˝ch SDR systĂ©mĹŻ znaÄŤnÄ› omezujĂ. Diskutována je zejmĂ©na problematika prĹŻniku nosnĂ© vysĂlaÄŤe do pĹ™ijĂmacĂ cesty a poĹľadavky na signál lokálnĂho oscilátoru pouĹľĂvanĂ˝ pro směšovánĂ. Prezentovány jsou tĹ™i vyvinutĂ© prototypy: experimentálnĂ dotazovaÄŤ EXIN-1, měřicĂ systĂ©m zaloĹľenĂ˝ na platformÄ› Ettus USRP a antĂ©nnĂ pĹ™epĂnacĂ matice pro emulaci SIMO systĂ©mu. ZávÄ›reÄŤná část je zaměřena na testovánĂ a zhodnocenĂ popisovanĂ˝ch lokalizaÄŤnĂch technik, zaloĹľenĂ˝ch na měřenĂ komplexnĂ pĹ™enosovĂ© funkce RFID kanálu. Popisuje ĂşzkopásmovĂ©/širokopásmovĂ© měřenĂ vzdálenosti a metody odhadu smÄ›ru signálu. Oba navrĹľenĂ© scĂ©náře rozmĂstÄ›nĂ antĂ©n jsou v závÄ›ru ověřeny lokalizaÄŤnĂm měřenĂm v reálnĂ˝ch podmĂnkách.The doctoral thesis is focused on methods and systems for ranging and localization of RFID tags operating in the UHF band. It begins with a description of the state of the art in the field of RFID positioning with short extension to the area of modeling and prototyping of such systems. After a brief specification of dissertation objectives, the thesis overviews the theory of degenerate channel modeling for RFID communication. Details are given about phase-based ranging and direction of arrival finding methods. Several antenna placement scenarios are proposed for localization purposes. The degenerate channel models are simulated in MATLAB. A significant part of the thesis is devoted to software defined radio (SDR) concept and its adaptation for UHF RFID operation, as it has its specialties which make the usage of standard SDR test equipment very disputable. Transmit carrier leakage into receiver path and requirements on local oscillator signals for mixing are discussed. The development of three experimental prototypes is also presented there: experimental interrogator EXIN-1, measurement system based on Ettus USRP platform, and antenna switching matrix for an emulation of SIMO system. The final part is focused on testing and evaluation of described positioning techniques based on complex backscatter channel transfer function measurement. Both narrowband/wideband ranging and direction of arrival methods are validated. Finally, both proposed antenna placement scenarios are evaluated with real-world measurements.
Viscoelastic vibration damping identification methods. Application to laminated glass.
Laminatedglass is composed of two glass layers and a thin intermediate PVB layer, strongly influencing PVB's viscoelastic behaviour its dynamic response. While natural frequencies are relatively easily identified even with simplified FE models, damping ratios are not identified with such an ease. In order to determine to what extent external factors influence dampingidentification, different tests have been carried out. The external factors considered, apart from temperature, are accelerometers, connection cables and the effect of the glass layers. To analyse the influence of the accelerometers and their connection cables a laser measuring device was employed considering three possibilities: sample without instrumentation, sample with the accelerometers fixed and sample completely instrumented. When the sample is completely instrumented, accelerometer readings are also analysed. To take into consideration the effect of the glass layers, tests were realised both for laminatedglass and monolithic samples. This paper presents in depth data analysis of the different configurations and establishes criteria for data acquisition when testing laminatedglass
Structure identification methods for atomistic simulations of crystalline materials
We discuss existing and new computational analysis techniques to classify
local atomic arrangements in large-scale atomistic computer simulations of
crystalline solids. This article includes a performance comparison of typical
analysis algorithms such as Common Neighbor Analysis, Centrosymmetry Analysis,
Bond Angle Analysis, Bond Order Analysis, and Voronoi Analysis. In addition we
propose a simple extension to the Common Neighbor Analysis method that makes it
suitable for multi-phase systems. Finally, we introduce a new structure
identification algorithm, the Neighbor Distance Analysis, that is designed to
identify atomic structure units in grain boundaries
Analytic performance evaluation of cumulant-based arma system identification methods
The authors perform an analytic study of some cumulant-based methods for estimating the AR parameters of ARMA processes. The analysis includes new AR identifiability results for pure AR process and the analytic performance evaluation of system identification methods based on cumulants. The authors present examples of pure AR processes that are not identifiable via the normal equations based on the diagonal third-order cumulant slice. The results of the performance evaluation are illustrated graphically with plots of the variance of the estimates as a function of the parameters of the process.Peer ReviewedPostprint (published version
The unseen world: environmental microbial sequencing and identification methods for ecologists
Archaea, bacteria, microeukaryotes, and the viruses that infect them (collectively “microorganisms”) are foundational components of all ecosystems, inhabiting almost every imaginable environment and comprising the majority of the planet’s organismal and evolutionary diversity. Microorganisms play integral roles in ecosystem functioning; are important in the biogeochemical cycling of carbon (C), nitrogen (N), sulfur (S), phosphorus (P), and various metals (eg Barnard et al. 2005); and may be vital to ecosystem responses to large-scale climatic change (Mackelprang et al. 2011). Rarely found alone, microorganisms often form complex communities that are dynamic in space and time (Martiny et al. 2006). For these and other reasons, ecologists and environmental scientists have become increasingly interested in understanding microbial dynamics in ecosystems. Ecological studies of microbes in the environment generally focus on determining which organisms are present and what functional roles they are playing or could play. Rapid advances in molecular and bioinformatic approaches over the past decade have dramatically reduced the difficulty and cost of addressing such questions (Figure 1; WebTable 1). Yet the range of methodologies currently in use and the rapid pace of their ongoing development can be daunting for researchers unaccustomed to these technologies
Comparison of several system identification methods for flexible structures
In the last few years various methods of identifying structural dynamics models from modal testing data have appeared. A comparison is presented of four of these algorithms: the Eigensystem Realization Algorithm (ERA), the modified version ERA/DC where DC indicated that it makes use of data correlation, the Q-Markov Cover algorithm, and an algorithm due to Moonen, DeMoor, Vandenberghe, and Vandewalle. The comparison is made using a five mode computer module of the 20 meter Mini-Mast truss structure at NASA Langley Research Center, and various noise levels are superimposed to produced simulated data. The results show that for the example considered ERA/DC generally gives the best results; that ERA/DC is always at least as good as ERA which is shown to be a special case of ERA/DC; that Q-Markov requires the use of significantly more data than ERA/DC to produce comparable results; and that is some situations Q-Markov cannot produce comparable results
Regional Identification Methods and Extratropical Dynamical Linkages to Surge Events in the North American Monsoon System
Transient behavior of the North American monsoon allows for episodic northward pulses of atmospheric moisture into the southwestern US. These surge events pose a difficult forecasting issue due to a lack of an accepted means to qualify their occurrence and the ill-defined influence of tropical and extratropical features that enable and drive them. Surge events have often been misidentified because of biases in ground observation site data related to localized influences not associated with surges. In this study, a novel method for the classification of surges is proposed based on their regional, rather than local, signature. This method is shown to be more accurate in detecting surge events related to widespread summertime precipitation events across the Desert Southwest of the US than previously established methods.
To further the understanding of mechanisms responsible for surge initiation, this study explored the influence that midlatitude troughs have on surges. Midlatitude troughs were shown to initiate surges that result in widespread precipitation across the southwestern US. Interactions where midlatitude troughs and tropical easterly waves jointly produce surge events were observed to dramatically increase the northward momentum and moisture flux and drive precipitation further north than typically occurs with the North American monsoon system
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