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Bess, Philip K. "Spread spectrum applications in unmanned aerial vehicles." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1994. http://handle.dtic.mil/100.2/ADA281035.
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Lähetkangas, K. (Kalle). "Special applications and spectrum sharing with LSA." Doctoral thesis, Oulun yliopisto, 2019. http://urn.fi/urn:isbn:9789526223940.
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Abstract The commercial long-term evolution (LTE) networks of today offer fast and regionally wide access to the Internet and to the commercial applications and services at a reasonable price. At the same time, public safety (PS) users are still communicating with old-fashioned, second-generation voice and data services. Recently, the commercial LTE networks have been standardized to offer capabilities to mission-critical users. However, the commercial networks do not yet fully support the coverage requirements of the PS users. Moreover, the commercial infrastructure might be out of order in critical scenarios where PS actors are needed. Thus, the PS users require, for example, rapidly deployed LTE networks to support their own communication. This thesis studies the PS use of commercial operators' LTE networks and rapidly deployed closed LTE networks. The key tasks are to find out how to connect users seamlessly together between the different networks as well as finding out how the frequency planning is implemented. This thesis provides practical design solutions to guarantee network interoperability by connecting the networks as well as radio spectrum utilization solutions by licensed shared access (LSA). While the concept of LSA has been well developed, it has not been thoroughly investigated from the point of view of the PS actors, who have special requirements and should benefit from the concept. Herein, the alternatives for spectrum sharing between PS and commercial systems are discussed. Moreover, the thesis develops a specific LSA spectrum sharing system for the PS actors deploying their own network in scenarios where the commercial networks are insufficient. The solution is a robust LSA-based spectrum sharing mechanism. Note that PS actors also need to be able to utilize the spectrum when the LSA system is not available and when the commercial system has failed. Thus, this thesis proceeds on developing sensing methods for complementing LSA, where the sensing methods guarantee spectrum information for a rapidly deployed PS network. It is shown how PS actors can utilize available spectrum with a secondary spectrum licence. This is a good alternative to reserving the spectrum completely. The work assembles missing pieces of existing methods to ensure the functionality of the commercial and of the supporting rapidly deployed networks, both in terms of spectrum usage and application servicesTiivistelmä Kaupalliset long-term evolution (LTE) -verkot tarjoavat nopean, edullisen ja alueellisesti kattavan pääsyn Internettiin sekä laajaan valikoimaan sovelluksia. Samaan aikaan turvallisuustoimijat (public safety (PS) -toimijat) käyttävät vanhanaikaisia äänen sekä vaatimattoman datayhteyden tarjoavia verkkoja. LTE-verkot ovat kuitenkin äskettäin standardoitu tarjoamaan valmiudet myös toimintokriittiseen kommunikointiin. Toisaalta, kaupalliset LTE-verkot eivät vielä tarjoa esimerkiksi tarvittavaa alueellista kattavuutta PS-käyttäjille. Lisäksi, kaupalliset verkot saattavat olla epäkunnossa kriittisissä tilanteissa. Tämän vuoksi PS-toimijat tarvitsevat omia nopeasti pystytettäviä LTE-verkkoja tukemaan nykyaikaista viestintäänsä. Opinnäytetyössä tutkitaan näiden nopeasti pystytettävien LTE-verkkojen käyttöä kaupallisten LTE-verkkojen kanssa. Keskeiset tehtävät ovat eri verkkojen PS-toimijoiden saumaton yhdistäminen sekä verkkojen taajuusjaon toteuttaminen. Tämä opinnäytetyö tarjoaa käytännön ratkaisuja verkkojen yhteentoimivuuden takaamiseksi ja radiotaajuuksien jakoratkaisuja lisensoidun jaetun käyttöoikeuden licensed shared access (LSA) -metodin avulla. Vaikka LSA:n käsite on jo pitkälle kehitetty, sitä ei ole tutkittu perusteellisesti PS-toimijoiden näkökulmasta ottaen huomioon heidän erityisvaatimuksensa. Tässä työssä syvennytään näiltä osin LSA järjestelmään yhtenä vaihtoehtona taajuuksien saamiseksi nopeasti pystytettäville verkoille. Lisäksi työssä kehitetään robusti LSA-pohjainen taajuuksien jakamisjärjestelmä nopeasti pystytettäville verkoille tilanteissa, joissa kaupalliset verkot ovat riittämättömät. Huomaa, että PS-toimijoiden on pystyttävä hyödyntämään taajuuksia myös silloin, kun LSA-järjestelmän kaikki osat eivät ole käytettävissä ja kun kaupallinen LTE järjestelmä on alhaalla. Tätä varten opinnäytetyössä kehitetään LSA:ta täydentävä havainnointimenetelmä, jolla taataan taajuustiedot vapaista taajuuksista nopeasti pystytettäville verkoille, sekä näytetään, miten PS-toimijat voivat hyödyntää LSA:ta toissijaisen taajuuslisenssin avulla. Tämä on hyvä vaihtoehto radiospektrin varaamiseksi kokonaan. Työ kokoaa puuttuvia osia olemassa oleviin menetelmiin, jotta voidaan varmistaa kaupallisten verkkojen toimivuus PS-käyttäjille yhdessä niitä tukevien nopeasti pystytettävien verkkojen kanssa taajuuksien käytön ja sovelluspalvelujen osalta
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Petrini, Valeria <1984>. "Cognitive radio applications for enhanced spectrum efficiency." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2013. http://amsdottorato.unibo.it/5493/1/Petrini_Valeria_tesi.pdf.
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The aim of this thesis is the study of techniques for efficient management and use of the spectrum based on cognitive radio technology. The ability of cognitive radio technologies to adapt to the real-time conditions of its operating environment, offers the potential for more flexible use of the available spectrum. In this context, the international interest is particularly focused on the “white spaces” in the UHF band of digital terrestrial television.
Spectrum sensing and geo-location database have been considered in order to obtain information on the electromagnetic environment. Different methodologies have been considered in order to investigate spectral resources potentially available for the white space devices in the TV band. The adopted methodologies are based on the geo-location database approach used either in autonomous operation or in combination with sensing techniques.
A novel and computationally efficient methodology for the calculation of the maximum permitted white space device EIRP is then proposed. The methodology is suitable for implementation in TV white space databases.
Different Italian scenarios are analyzed in order to identify both the available spectrum and the white space device emission limits.
Finally two different applications of cognitive radio technology are considered. The first considered application is the emergency management. The attention is focused on the consideration of both cognitive and autonomic networking approaches when deploying an emergency management system. The cognitive technology is then considered in applications related to satellite systems. In particular a hybrid cognitive satellite-terrestrial is introduced and an analysis of coexistence between terrestrial and satellite networks by considering a cognitive approach is performed.
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Petrini, Valeria <1984>. "Cognitive radio applications for enhanced spectrum efficiency." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2013. http://amsdottorato.unibo.it/5493/.
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The aim of this thesis is the study of techniques for efficient management and use of the spectrum based on cognitive radio technology. The ability of cognitive radio technologies to adapt to the real-time conditions of its operating environment, offers the potential for more flexible use of the available spectrum. In this context, the international interest is particularly focused on the “white spaces” in the UHF band of digital terrestrial television.
Spectrum sensing and geo-location database have been considered in order to obtain information on the electromagnetic environment. Different methodologies have been considered in order to investigate spectral resources potentially available for the white space devices in the TV band. The adopted methodologies are based on the geo-location database approach used either in autonomous operation or in combination with sensing techniques.
A novel and computationally efficient methodology for the calculation of the maximum permitted white space device EIRP is then proposed. The methodology is suitable for implementation in TV white space databases.
Different Italian scenarios are analyzed in order to identify both the available spectrum and the white space device emission limits.
Finally two different applications of cognitive radio technology are considered. The first considered application is the emergency management. The attention is focused on the consideration of both cognitive and autonomic networking approaches when deploying an emergency management system. The cognitive technology is then considered in applications related to satellite systems. In particular a hybrid cognitive satellite-terrestrial is introduced and an analysis of coexistence between terrestrial and satellite networks by considering a cognitive approach is performed.
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Mariani, Andrea <1984>. "Spectrum Sensing Algorithms for Cognitive Radio Applications." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2013. http://amsdottorato.unibo.it/5615/2/Mariani_Andrea_SpectrumSensingforCognitiveRadio.pdf.
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Future wireless communications systems are expected to be extremely dynamic, smart and capable to interact with the surrounding radio environment. To implement such advanced devices, cognitive radio (CR) is a promising paradigm, focusing on strategies for acquiring information and learning. The first task of a cognitive systems is spectrum sensing, that has been mainly studied in the context of opportunistic spectrum access, in which cognitive nodes must implement signal detection techniques to identify unused bands for transmission.
In the present work, we study different spectrum sensing algorithms, focusing on their statistical description and evaluation of the detection performance. Moving from traditional sensing approaches we consider the presence of practical impairments, and analyze algorithm design. Far from the ambition of cover the broad spectrum of spectrum sensing, we aim at providing contributions to the main classes of sensing techniques. In particular, in the context of energy detection we studied the practical design of the test, considering the case in which the noise power is estimated at the receiver. This analysis allows to deepen the phenomenon of the SNR wall, providing the conditions for its existence and showing that presence of the SNR wall is determined by the accuracy of the noise power estimation process. In the context of the eigenvalue based detectors, that can be adopted by multiple sensors systems, we studied the practical situation in presence of unbalances in the noise power at the receivers. Then, we shift the focus from single band detectors to wideband sensing, proposing a new approach based on information theoretic criteria. This technique is blind and, requiring no threshold setting, can be adopted even if the statistical distribution of the observed data in not known exactly. In the last part of the thesis we analyze some simple cooperative localization techniques based on weighted centroid strategies.
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Mariani, Andrea <1984>. "Spectrum Sensing Algorithms for Cognitive Radio Applications." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2013. http://amsdottorato.unibo.it/5615/.
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Future wireless communications systems are expected to be extremely dynamic, smart and capable to interact with the surrounding radio environment. To implement such advanced devices, cognitive radio (CR) is a promising paradigm, focusing on strategies for acquiring information and learning. The first task of a cognitive systems is spectrum sensing, that has been mainly studied in the context of opportunistic spectrum access, in which cognitive nodes must implement signal detection techniques to identify unused bands for transmission.
In the present work, we study different spectrum sensing algorithms, focusing on their statistical description and evaluation of the detection performance. Moving from traditional sensing approaches we consider the presence of practical impairments, and analyze algorithm design. Far from the ambition of cover the broad spectrum of spectrum sensing, we aim at providing contributions to the main classes of sensing techniques. In particular, in the context of energy detection we studied the practical design of the test, considering the case in which the noise power is estimated at the receiver. This analysis allows to deepen the phenomenon of the SNR wall, providing the conditions for its existence and showing that presence of the SNR wall is determined by the accuracy of the noise power estimation process. In the context of the eigenvalue based detectors, that can be adopted by multiple sensors systems, we studied the practical situation in presence of unbalances in the noise power at the receivers. Then, we shift the focus from single band detectors to wideband sensing, proposing a new approach based on information theoretic criteria. This technique is blind and, requiring no threshold setting, can be adopted even if the statistical distribution of the observed data in not known exactly. In the last part of the thesis we analyze some simple cooperative localization techniques based on weighted centroid strategies.
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Jiang, Chen. "Applications of frequency hopping systems." Click to view the E-thesis via HKUTO, 2001. http://sunzi.lib.hku.hk/hkuto/record/B31241852.
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江晨 and Chen Jiang. "Applications of frequency hopping systems." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2001. http://hub.hku.hk/bib/B31241852.
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Jiang, Chen. "Applications of frequency hopping systems." Hong Kong : University of Hong Kong, 1999. http://sunzi.lib.hku.hk:8888/cgi-bin/hkuto%5Ftoc%5Fpdf?B22277729.
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Papadimitriou, Panayiotis D. "Code design based on metric-spectrum and applications." Texas A&M University, 2004. http://hdl.handle.net/1969.1/1365.
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We introduced nested search methods to design (n, k) block codes for arbitrary channels by optimizing an appropriate metric spectrum in each iteration. For a given k, the methods start with a good high rate code, say k/(k + 1), and successively design lower rate codes up to rate k/2^k corresponding to a Hadamard code. Using a full search for small binary codes we found that optimal or near-optimal codes of increasing length can be obtained in a nested manner by utilizing Hadamard matrix columns. The codes can be linear if the Hadamard matrix is linear and non-linear otherwise. The design methodology was extended to the generic complex codes by utilizing columns of newly derived or existing unitary codes. The inherent nested nature of the codes make them ideal for progressive transmission.
Extensive comparisons to metric bounds and to previously designed codes show the optimality or near-optimality of the new codes, designed for the fading and the additive white Gaussian noise channel (AWGN). It was also shown that linear codes can be optimal or at least meeting the metric bounds; one example is the systematic pilot-based code of rate k/(k + 1) which was proved to meet the lower bound on the maximum cross-correlation. Further, the method was generalized such that good codes for arbitrary channels can be designed given the corresponding metric or the pairwise error probability.
In synchronous multiple-access schemes it is common to use unitary block codes to transmit the multiple users information, especially in the downlink. In this work we suggest the use of newly designed non-unitary block codes, resulting in increased throughput efficiency, while the performance is shown not to be substantially sacrificed. The non-unitary codes are again developed through suitable nested searches. In addition, new multiple-access codes are introduced that optimize certain criteria, such as the sum-rate capacity.
Finally, the introduction of the asymptotically optimum convolutional codes for a given constraint length, reduces dramatically the search size for good convolutional codes of a certain asymptotic performance, and the consequences to coded code-division multiple access (CDMA) system design are highlighted.
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Street, Andrew M. "Spread spectrum techniques for multiplexing and ranging applications." Thesis, University of Oxford, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.259828.
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Sun, Shaobo. "Applications of spectrum slicing in optical access networks." Thesis, University of Warwick, 2010. http://wrap.warwick.ac.uk/34617/.
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Spectrum-slicing (SS) is a novel attractive technique for the implementation of optical access network. Its main advantage compared to the conventional optical network is utilizing spectral slices of a broadband source for different data channels. Since the light sources employed are quite cost effective, this technology is economically attractive to the modern communication system. The major objective of this dissertation is to investigate the performance of systems employing spectrum-slicing, for implementing wavelength division multiplexing (WDM) and optical code division multiple access (OCDMA) in optical access systems. The analysis is conducted mainly through the theoretical model based on the statistics, derived from fundamental chi-square and Gaussian distribution. Firstly, the analysis of an SS-WDM system performance when employing an optical preamplifier receiver is carried out to improve understanding of the SS in a realistic situation where dispersion significantly impacts the signal in transmission. It is shown that there exists an optimum optical bandwidth which minimizes the detection sensitivity for a given error probability caused by two competing effects of inherent signal fluctuation and dispersion. The optically preamplified receiver delivers increased transmission capacity and a substantially improved power budget compared to a pin receiver. The results are obtained using the saddle point approximation and compared to the customary Gaussian approximation, which is found to be reasonably accurate in predicting the optimum bandwidth but conservative in sensitivity predictions. The second part of the work investigates the performance of an SS-OCDMA employing and proposes a supporting adaptive coding scheme developed from prime-hop codes. The concomitant higher-order dispersion, beat noise and multiple access interference in incoherent OCDMA systems become limiting factors to the bit error rate. The major thrusts of the new schemes are to alleviate the performance degradation from these impacts especially to reduce the power loss and the bit error rate (BER) degradation due to higher-order dispersion. Performance comparisons between the adaptive PHC and original PHC schemes indicate that the former is more suitable for use in the considered incoherent system in terms of accommodating more users for a given BER. The proposed adaptive method can be universally applied to mitigate dispersion effects in the similar 2-D OCDMA systems. Within the last part of the work, regular low-density parity-check (LDPC) codes are applied for the first time to a SS-WDM system. An adaptive decoding algorithm of low density parity check (LDPC) codes based on the precise SSWDM noise statistics is developed, which outperforms the decoding with conventional Gaussian model. The simulation results for various code rates show that such a forward error correction scheme provides significant coding gain for a dedicated system in terms of improving the overall transmission capacity and available power budget. The adaptive algorithm of LDPC codes can be generically applied to all the asymmetric channels.
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Silva, Agampodige Emmanuel Diyanth Sirimal. "Theoretical advancements and applications in singular spectrum analysis." Thesis, Bournemouth University, 2016. http://eprints.bournemouth.ac.uk/25043/.
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Singular Spectrum Analysis (SSA) is a nonparametric time series analysis and forecasting technique which has witnessed an augment in applications in the recent past. The increased application of SSA is closely associated with its superior filtering and signal extraction capabilities which also differentiates it from the classical time series methods. In brief, the SSA process consists of decomposing a time series for signal extraction and then reconstructing a less noisy series which is used for forecasting. The aim of this research is to develop theoretical advancements in SSA, supported by empirical evidence to further promote the value, effectiveness and applicability of the technique in the field of time series analysis and forecasting. To that end, this research has four main contributions. Initially, given the reliance of this research towards improving forecasting processes, it is mandatory to compare and distinguish between the predictive accuracy of forecasts for statistically significant differences. The first contribution of this research is the introduction of a complement statistical test for comparing between the predictive accuracy of two forecasts. The proposed test is based on the principles of cumulative distribution functions and stochastic dominance, and is evaluated via both a simulation study and empirical evidence. Governments, practitioners, researchers and private organizations publish a variety of forecasts each year. Such forecasts are generally computed using multivariate models and are widely used in decision making processes given the considerably high level of anticipated forecast accuracy. The classical multivariate methods consider modelling multiple information pertaining to the same time period or with a time lag into the past. Multivariate Singular Spectrum Analysis (MSSA) is a relatively new and alternative technique for generating forecasts from multiple time series. The second contribution of this research is the introduction of a novel theoretical development which seeks to exploit the information contained in published forecasts (which represent data with a time lag into the future) for generating a new and improved (comparatively more accurate) forecast by taking advantage of the MSSA technique’s capability at modelling time series with different series lengths. In brief, the proposed multivariate theoretical development seeks to exploit the forecastability of forecasts by considering not only official and professional forecasts, but also forecasts obtained via other time series models. The productive application of SSA and MSSA depends largely on the selection of SSA and MSSA parameters, i.e. the Window Length, L, and the number of eigenvalues r which are used for decomposition and reconstruction of time series. Over the years, a variety of mathematically complex, time consuming and labour intensive approaches which require detailed knowledge on the theory underlying SSA have been proposed and developed for the selection of SSA and MSSA parameters. However, the highly labour intensive and complex nature of such approaches have not only discouraged the application of this method by those not conversant with the underlying theory, but also limited SSA and MSSA to offline applications. The third and final contribution of this research proposes new, automated and optimized, SSA and MSSA algorithms for the selection of SSA parameters and thereby enables obtaining optimal SSA and MSSA forecasts (optimized by minimising a loss function). This development opens up the possibility of using SSA and MSSA for online forecasting in the future.
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Bais, Viraj Kumar. "Simulation of multistage detector for spread-spectrum applications." Master's thesis, This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-12232009-020220/.
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Walsh, Penelope Jane, and n/a. "Modelling and spectroscopy of polypyridyl and porphyrin complexes for electroluminescence and solar cell applications." University of Otago. Department of Chemistry, 2007. http://adt.otago.ac.nz./public/adt-NZDU20070927.151236.
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This thesis reports the spectroscopic and computational studies of two classes of compounds, which have applications in new optoelectronic materials technology. Substituted ligands of dipyrido-[3,2a:2�,3�c]phenazine (dppz), and their Cu(I), Re(I) and Ru(II) complexes have utility in organic electroluminescent devices. A series of Zn(II) tetraphenylporphyrins with conjugated functional groups at the β-position have been used with success in liquid heterojunction dye-sensitized solar cells. The vibrational spectra and optoelectronic properties of the two classes were investigated using Raman, resonance Raman and transient resonance Raman spectroscopy, in conjunction with density functional theory methods.
Density functional theory frequency calculations were used to aid vibrational mode assignments for the dppz compounds, and show close agreement with the experimental non-resonance Raman spectra. The enhancement of modes which are localized on differing sections of the ligand was identified. The nature of the absorbing chromophores for the dppz ligands and complexes was established using resonance Raman spectroscopy in concert with vibrational assignments from calculations. Transient resonance Raman spectra of the ligands provided spectral signatures for the triplet ligand-centred state; these features were observed in the TR� spectra of the metal complexes, along with other features attributable to MLCT states.
Electroluminescent devices were fabricated using the dppz ligands and complexes as emissive dopants, and their properties investigated. The optoelectronic behaviour of the devices was found to be influenced by the mechanism of exciton formation on the dopant. The device properties were also dependent on the dopant concentration, the concentrations of other components and the driving voltage.
The electronic structure of the porphyrin compounds was investigated using time-dependent density functional theory methods. Comparison of calculated optical transitions with experimental data shows that the calculations predict trends in the optical absorption spectra with change of functional group and with increase in conjugation chain length. The calculations suggest that the electron-withdrawing substituent decreases the configuration interaction effect by breaking the degeneracy of the two lowest unoccupied MOs, and other configuration interaction effects come into play involving other frontier MOs. Interrupting the conjugation of the functional group is shown to mitigate the breakdown of the configuration interaction.
The perturbation of the normal electronic structure of the porphyrin by the substituent was also investigated using resonance Raman spectroscopy. Vibrational analysis identified bands due to the substituent, implying coupling between the porphyrin and substituent chromophores. Changes in frequency of porphyrin core modes due to the differing substituents and different metal centres were reproduced by density functional theory calculations.
This project has allowed the spectroscopic investigation of the active optical states in a number of polypyridyl and porphyrin compounds, and determined the efficacy of DFT and TDDFT calculations to predict the properties of these compounds.
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Nelson, Paul Redfield. "Applications of analytical collisional mass spectrometry." Diss., Georgia Institute of Technology, 1987. http://hdl.handle.net/1853/27053.
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Park, Jongmin. "CMOS analog spectrum processing techniques for cognitive radio applications." Diss., Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/37230.
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The objective of the research is to develop analog spectrum processing techniques for cognitive radio (CR) applications in CMOS technology. CR systems aim to use the unoccupied spectrum allocations without any license when the primary users are not present. Therefore, the successful deployment of CR systems relies on their ability to accurately sense the spectrum usage status over a wide frequency range serving various wireless communication standards. Meanwhile, to maximize the utilization of the available spectrum segments, the bandwidth of the signal has to be highly flexible, so that even a small fraction of spectrum resources can be fully utilized by CR users. One of the key enabling technologies of variable bandwidth communication is a tunable baseband filter.
In this research, a reconfigurable CR testbed system is presented as groundwork for the researches related with CR systems. With the feasibility study on the multi-resolution spectrum sensing (MRSS) functionality, a method for determining sensing threshold for MRSS functionality is presented, and a fully integrated MRSS receiver in CMOS technology is demonstrated. On the other hand, a reconfigurable CMOS analog baseband filter which can change its bandwidth, type and order with high resolution for CR applications is presented. In sum, an analog spectrum sensing method as well as a highly flexible analog baseband filter architecture is established and implemented in CMOS technology. Both designs are targeting the utilization of the analog signal processing capability with the aid of the digital circuits.
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Linares, Irving. "Theory and applications of the estimated spectrum adaptive postfilter." Diss., Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/14962.
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Harvey, Pierre Dominique. "Applications of vibrational spectroscopy and NMR spin-lattice relaxation time measurements to organometallic and organic molecular crystals." Thesis, McGill University, 1985. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=73986.
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Adibnejad, Mohammad. "Rotors moléculaires fluorescents : synthèse, étude photophysique, applications." Vandoeuvre-les-Nancy, INPL, 1996. http://www.theses.fr/1996INPL053N.
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L’objectif de l'étude développée est d'élargir les potentialités de la fluorescence comme méthode d'investigation de la structure de milieux complexes et microhétérogènes (systèmes moléculaires organisés, polymères, milieux biologiques, etc. ), en utilisant plus particulièrement des rotors moléculaires comme sondes fluorescentes. Le travail effectué concerne trois aspects qui sont: 1) la synthèse chimique de nouveaux rotors moléculaires fluorescents, dont des rotors comportant des motifs glucidiques, qui leur confèrent des propriétés amphiphiles et orientent spécifiquement leur site de fixation dans des milieux hétérogènes (membranes biologiques modèles), 2) l'étude photophysique des rotors moléculaires fluorescents dans des solvants, pour déterminer leurs caractéristiques d'absorption UV-visible et d'émission de fluorescence (excitation continue et pulsée), en étudiant d'une part l'influence de la structure du rotor (nature des substituants, présence de conjugaison) et d'autre part l'influence de divers paramètres d'environnement (nature du solvant, polarité, viscosité), 3) les applications des rotors fluorescents en considérant cinq domaines: (i) les micelles: détecter l'agrégation de tensioactifs (CMC, polarité, cohésion) ; (ii) les liposomes: détecter la phase de transition de lipides ; (iii) les composés intervenant dans la coagulation sanguine: suivre le processus de la fibrinoformation ; (iv) les polymères à caractère amphiphile: détecter la formation de microdomaines hydrophobes ; (v) les composés intervenant dans la polymérisation: suivre la polymérisation en masse du MMA en PMMA et déterminer des paramètres cinétiques. Dans plusieurs études, le pyrène comme sonde fluorescente a aussi été utilisé, soit pour valider les informations relatives aux rotors, soit pour compléter ces informations
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Moalusi, Matlhodi Salamina. "Selected applications of sequential injection analysis." Pretoria : [s.n.], 2006. http://upetd.up.ac.za/thesis/available/etd-08212007-155923.
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Blaquière-Nowlan, Anne J. "MV-spectrum-based applications for vibration analysis of magnetic bearings." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ29972.pdf.
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Aly, Omar Abdel-Gaber Mohamed. "Enhancing the performance of spread spectrum techniques in different applications." [S.l.] : [s.n.], 2006. http://diglib.uni-magdeburg.de/Dissertationen/2006/omaaly.htm.
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Russo, Juan Manuel. "Holographic Grating-over-Lens Dispersive Spectrum Splitting for Photovoltaic Applications." Diss., The University of Arizona, 2014. http://hdl.handle.net/10150/347092.
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During the past few years there has been a significant interest in spectrum splitting systems to increase the overall efficiency of photovoltaic solar energy systems. However, methods for comparing the performance of spectrum splitting systems and the effects of optical spectral filter design on system performance are not well developed. This dissertation first establishes a method to analyze and compare spectrum splitting systems with different filters, PV cells types and geometries. The method examines the system conversion efficiency in detail and the role of optical spectral filters. A new metric termed the Improvement over Best Bandgap is defined which expresses the efficiency gain of the spectrum splitting system with respect to a similar system that contains the highest constituent single bandgap photovoltaic cell. Also, this work expands the analysis on dispersive spectrum splitting systems. The dispersive effects of transmission type filters are evaluated using a cross-correlation analysis. Lastly, this work presents a grating-over-lens design for dispersive spectrum splitting. In this geometry, a transmission grating is placed at the entrance of a lens. Part of the incident solar spectrum is diffracted off-axis from normal incidence to the lens. The diffracted spectral range comes to a focus at an off-axis point and the undiffracted spectrum comes to a focus at the paraxial focus of the lens. Since the diffracted wave is planar and off-axis, the off-axis focal points suffer from aberrations that increase system loss. In this work, a novel aberration compensation technique is presented using non-planar transmission gratings recorded using a conjugate object beam to modify the off-axis wavefront. Diverging sources are used as conjugate object and reference beams. The spherical waves are incident at the lens and the grating is recorded at the entrance aperture of the solar concentrator. The on-axis source is adjusted to produce an on-axis planar wavefront at the hologram plane. The off-axis source is approximated to a diffraction limited spot producing a non-planar off-axis wavefront on the hologram plane. Illumination with a planar AM1.5 spectrum reproduces an off-axis diffraction-limited spot on the focal plane. Models and experimental data are presented to quantify the reduction in losses achieved with aberration correction.
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Xing, Jie, and 邢杰. "Applications of FT-Raman spectroscopy in starch analysis." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2002. http://hub.hku.hk/bib/B31243824.
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Xing, Jie. "Applications of FT-Raman spectroscopy in starch analysis /." Hong Kong : University of Hong Kong, 2002. http://sunzi.lib.hku.hk/hkuto/record.jsp?B24534341.
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Perkins, Jonathan Hale. "Some applications of linear algebra to quantitative spectroscopy /." Thesis, Connect to this title online; UW restricted, 1988. http://hdl.handle.net/1773/11534.
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Lin, Huang-De Hennessy. "Parametric projection pursuits for dimensionality reduction of hyperspectral signals in target recognition applications." Master's thesis, Mississippi State : Mississippi State University, 2004. http://library.msstate.edu/etd/show.asp?etd=etd-12162003-202048.
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Rittenhouse, Michelle L. "Properties and Recent Applications in Spectral Graph Theory." VCU Scholars Compass, 2008. http://scholarscompass.vcu.edu/etd/1126.
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There are numerous applications of mathematics, specifically spectral graph theory, within the sciences and many other fields. This paper is an exploration of recent applications of spectral graph theory, including the fields of chemistry, biology, and graph coloring. Topics such as the isomers of alkanes, the importance of eigenvalues in protein structures, and the aid that the spectra of a graph provides when coloring a graph are covered, as well as others.The key definitions and properties of graph theory are introduced. Important aspects of graphs, such as the walks and the adjacency matrix are explored. In addition, bipartite graphs are discussed along with properties that apply strictly to bipartite graphs. The main focus is on the characteristic polynomial and the eigenvalues that it produces, because most of the applications involve specific eigenvalues. For example, if isomers are organized according to their eigenvalues, a pattern comes to light. There is a parallel between the size of the eigenvalue (in comparison to the other eigenvalues) and the maximum degree of the graph. The maximum degree of the graph tells us the most carbon atoms attached to any given carbon atom within the structure. The Laplacian matrix and many of its properties are discussed at length, including the classical Matrix Tree Theorem and Cayley's Tree Theorem. Also, an alternative approach to defining the Laplacian is explored and compared to the traditional Laplacian.
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Donelan, Helen Margaret. "The Properties and Applications of Structured Codes to Spread Spectrum Communication Systems." Thesis, University of Leeds, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.486157.
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Lee, Bong-Woon. "Applications of signal processing techniques in direct-sequence spread spectrum communication systems." Ohio : Ohio University, 1990. http://www.ohiolink.edu/etd/view.cgi?ohiou1173208101.
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Lohmiller, Peter [Verfasser]. "Spectrum Sensing RF Front-End Module for Cognitive Radio Applications / Peter Lohmiller." Berlin : epubli, 2017. http://d-nb.info/1123330557/34.
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Ibrahim, Ibrahim Ismail. "Design and performance of multiple access, spread spectrum systems for telemetry applications." Thesis, Queen's University Belfast, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.329617.
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Jaffke, Patrick John. "Corrections to and Applications of the Antineutrino Spectrum Generated by Nuclear Reactors." Diss., Virginia Tech, 2015. http://hdl.handle.net/10919/80031.
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In this work, the antineutrino spectrum as specifically generated by nuclear reactors is studied. The topics covered include corrections and higher-order effects in reactor antineutrino experiments, one of which is covered in Ref. [1] and another contributes to Ref. [2]. In addition, a practical application, antineutrino safeguards for nuclear reactors, as summarized in Ref. [3,4] and Ref. [5], is explored to determine its viability and limits. The work will focus heavily on theory, simulation, and statistical analyses to explain the corrections, their origins, and their sizes, as well as the applications of the antineutrino signal from nuclear reactors.
Chapter [1] serves as an introduction to neutrinos. Their origin is briefly covered, along with neutrino properties and some experimental highlights. The next chapter, Chapter [2], will specifically cover antineutrinos as generated in nuclear reactors. In this chapter, the production and detection methods of reactor neutrinos are introduced as well as a discussion of the theories behind determining the antineutrino spectrum. The mathematical formulation of neutrino oscillation will also be introduced and explained.
The first half of this work focuses on two corrections to the reactor antineutrino spectrum. These corrections are generated from two specific sources and are thus named the spent nuclear fuel contribution and the non-linear correction for their respective sources. Chapter [3] contains a discussion of the spent fuel contribution. This correction arises from spent nuclear fuel near the reactor site and involves a detailed application of spent fuel to current reactor antineutrino experiments. Chapter [4] will focus on the non-linear correction, which is caused by neutron-captures within the nuclear reactor environment. Its quantification and impact on future antineutrino experiments are discussed.
The research projects presented in the second half, Chapter [5], focus on neutrino applications, specifically reactor monitoring. Chapter [5] is a comprehensive examination of the use of antineutrinos as a reactor safeguards mechanism. This chapter will include the theory behind safeguards, the statistical derivation of power and plutonium measurements, the details of reactor simulations, and the future outlook for non-proliferation through antineutrino monitoring.Ph. D.
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Letzelter, Corinne. "Spectroscopie et photodissociation de la molecule de co : applications astrophysiques." Paris 6, 1987. http://www.theses.fr/1987PA066182.
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Etude des spectres d'absorption et d'emission de la molecule de co et de ses isotopes dans le domaine 88. 5 nm-125 nm. Les sections efficaces d'absorption des bandes de co entre 88. 5 nm et 115 nm ont ete mesurees en utilisant le rayonnement synchrotron comme source lumineuse. La fluorescence a ete observee dans tout le domaine uv et visible et les rendements de flourescence ont ete determines. La section efficace de photodissociation corespondante est calculee en tenant compte d'un eventuel continuum de dissociation pour lequel une limite de la section efficace d'absorption a ete donnee. Presentation des consequences de ces nouvelles donnees sur la modelisation des nuages interstellaires
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Vallina-Rodriguez, Narseo. "The hidden costs of mobile applications : a cross-layer analysis of energy and spectrum waste of mobile applications." Thesis, University of Cambridge, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.648525.
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Cerocchi, Filippo. "Dynamical and Spectral applications of Gromov-Hausdorff Theory." Thesis, Grenoble, 2013. http://www.theses.fr/2013GRENM077/document.
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Cette thèse est divisée en deux parties. La première est consacrée à la méthode du barycentre, introduite en 1995 par G. Besson, G. Courtois et S. Gallot pour résoudre la conjecture de l'Entropie Minimale. Dans le Chapitre 1 nous décrivons ses développements les plus récents, notamment l'extension de cette méthode au cadre des variétés dont la courbure sectionnelle est de signe quelconque (voir les énoncés 1.2.1 et 1.4.1). Dans le Chapitre 2 et 3 nous présentons des résultats dans lesquels la méthode du barycentre joue un rôle important. Le problème “deux variétés dont les flots géodésiques sont conjugués sont-elles isométriques ?” (problème de la rigidité par conjugaison des flots) est le thème du Chapitre 2. Après avoir montré que deux telles variétés ont la même géométrie à grande échelle, on montre comment on peut utiliser ce résultat et la méthode du barycentre pour donner une nouvelle preuve de la rigidité (par conjugaison des flots) des variétés plates. Dans le Chapitre 3 nous utilisons la méthode du barycentre (en courbure de signe quelconque) et des inégalités de Sobolev itérées pour démontrer un théorème de comparaison entre les spectres de deux variétés riemanniennes (Y , g) et (X , g') de volumes proches, sachant qu'il existe une approximation de Gromov-Hausdorff de degré non nul entre ces deux variétés. Il s'agit d'un résultat d'approximation avec majoration de l'erreur d'approximation (et pas seulement d'un résultat de convergence). Remarquons qu'il n'est fait aucune autre hypothèse géométrique (et en particulier aucune hypothèse de courbure) sur la variété (Y , g), ce qui autorise un grand nombre de contre-exemples prouvant que le résultat est optimal. Dans la deuxième partie de la thèse (chapitre 4), on démontre un Lemme de Margulis sans hypothèse sur la courbure, qui s'applique aux variétés dont les groupes fondamentaux sont des produits libres (et qui ne possèdent pas d'élément de torsion d'ordre 2). Nous donnons également une borne inférieure de la systole des variétés dont le diamètre et l'entropie volumique sont majorés et dont le groupe fondamental est isomorphe à un produit libre sans torsion. Comme conséquences de ce dernier résultat nous obtenons des résultats de précompacité et de finitude topologique ou différentiable pour les variétés riemanniennes et une minoration de leur volume, tout ceci sans faire d'hypothèse de courbureThis Ph.D. Thesis is divided into two parts. In the first part we present the barycenter method, a technique which has been introduced by G. Besson, G. Courtois and S. Gallot in 1995, in order to solve the Minimal Entropy conjecture. In Chapter 1 we are interested in the more recent developments of this method, more precisely in the recent extension of the method to the case of manifolds having sectional curvature of variable sign. In Chapters 2 and 3 we shall present some new results whose proofs make use of the barycenter method. The Conjugacy Rigidity problem is the theme of Chapter 2. First we show a general result which provide a comparison between the large scale geometry of the Riemannian universal coverings of two compact manifolds whose geodesic flows are conjugates. Then we shall show how we can apply the latter result and the barycenter method in curvature of variable sign in order to give a new proof of the conjugacy rigidity of flat manifolds. In Chapter 3 we shall give a proof of a spectra comparison theorem for a compact Riemannian manifold which admits a Gromov-Hausdorff-approximation of non zero absolute degree on a fixed compact manifold (X,g') and which has volume almost smaller than the one of the reference manifold. The proof relies on the barycenter method in curvature of variable sign and on iterated Sobolev inequalities. We underline that it is an approximation result (and not just a convergence result) and that no curvature assumptions are made or inferred on (Y,g). The second part of the Thesis consists of a single chapter. In this chapter we prove a Margulis Lemma without curvature assumptions for Riemannian manifolds having decomposable 2-torsionless fundamental group. We shall give also a proof of a universal lower bound for the homotopy systole of compact Riemannian manifolds having bounded volume entropy and diameter, and decomposable torsionless fundamental group. As a consequence of the latter result we shall deduce a Precompactness and Finiteness theorem and a Volume estimate without curvature assumptions
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Rohatgi, Anil. "Implementation and Applications of an Anti-Collision Differential-Offset Spread Spectrum RFID System." Thesis, Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/13946.
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This report documents the design, construction, and implementation of a differential-offset spread spectrum RFID system, to avoid the problem of anti-collision interference from multiple RFID tags. Currently in industry, this problem is handled by establishing a two way communication link between the tags and the interrogator. The proposed system eliminates the need for the excessive hardware use to create this link, and therefore drastically reduces the cost of each tag. Not only is this system cheaper to implement but it is faster, requires less power, and by the nature of the design contains an inherent encryption scheme for the data being transmitted.
Specialized RFID tags were designed and fabricated in order to produce a pseudo random code unique to each tag. The design presented in this document allowed simultaneous interrogation of up to 255 tags within one sensing environment. Once queried, the tags then modulate the incoming signal from the interrogator with their own sequence, and reflect the signal back to the interrogator. What the interrogator then receives is a combination of backscatter from all of the tags within the sensing environment. Specialized software written in Matlab and LabView uses these unique sequences to isolate the data from a desired tag away from the sea of information being transmitted from every tag. Using this system, numerous applications for experiments and measurements can be devised.
One such application this thesis focuses on is the use of this system to simultaneously measure signal strengths from multiple diversity antennas in order to optimize their position and orientation. Currently, the majority of antenna diversity measurements are taken by measuring the signal strength of a given configuration one antenna at a time. By using the anti-collision RFID system proposed above, the signal strength produced by both antennas can be measured and recorded simultaneously to provide a true representation of their combined performance. This measurement can be used to find the optimal configuration for multiple antennas.
This thesis will fully explore the theories and procedures behind creating this system, and will provide the results and analysis of its performance.
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Yoon, Seungil. "Cross-layer dynamic spectrum management framework for the coexistence of white space applications." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/44787.
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The objective of this dissertation is to propose the cross-layer spectrum management architecture for white space applications that improves the performance the main functions of the spectrum management. In the proposed cross-layer architecture, white space network devices such as white space devices and the spectrum map server cooperate to support the extended spectrum map, the inter-cell transmit power adaptation (ITPA), and the frequency-domain coexistence beacon (FCB). Upon the cross-layer architecture, firstly, white space devices (WSDs) achieve a faster search and higher accuracy in spectrum sensing with the extended spectrum map, the extended DHCP (Dynamic Host Configuration Protocol), and the FCB. Secondly, WSDs achieve the precise selection of their operating channel in spectrum decision with the extended spectrum map and the ITPA. In spectrum sharing, thirdly, the collaboration- based spectrum sharing with the ITPA achieve more accommodation of WSDs by increasing the number of channels shared between WSDs. Finally, WSDs with the FCB and the extended spectrum achieve effective spectrum mobility by obtaining the occupancy-status of channels precisely.
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Andrews, Derek Sayre. "Novel applications of surface based morphometry and pattern classification in autism spectrum disorders." Thesis, King's College London (University of London), 2018. https://kclpure.kcl.ac.uk/portal/en/theses/novel-applications-of-surface-based-morphometry-and-pattern-classification-in-autism-spectrum-disorders(e4ce8d68-12ee-42a6-928c-d6393c9489bd).html.
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Autism spectrum disorder (ASD) is a lifelong, behaviorally defined neurodevelopmental condition that is characterized by deficits in social communication, interaction, and repetitive behaviors. These behavioral symptoms are associated with atypical brain structure, function, and connectivity. The studies that comprise this thesis employed structural magnetic resonance imaging (MRI) to address aims in three areas of ASD research. First, we examined a novel neuroimaging feature based on signal intensity contrast between grey and white matter to quantify atypical microstructure at the greywhite matter boundary in ASD. We found reduced tissue contrast at the grey-white matter boundary among adults with ASD when compared typically developing (TD) controls. This result indicates that measures of tissue contrast may serve as an in vivo proxy measure of atypical cortical microstructure that has previously been reported in histological studies. Second, we trained multivariate pattern recognition models to identify individuals with ASD based on measures of cortical morphometry, and examined the predictive value of these models in a representative clinical sample. We demonstrated that these models have modest ability to distinguish cases from controls in the research setting. Only one model that was based on measures of grey-white matter tissue contrast identified individuals with and without ASD diagnoses at high overall accuracy (81%) in the clinical setting. However, this model did not provide significant accuracies above chance in the research setting, and therefore these results should be considered as preliminary and suggestive only. Third, we established normative models of phenotypic diversity in brain structure associated with biological sex in a sample of TD males and females which was subsequently applied to males and females with ASD. Across different morphometric features, females with ASD displayed a significant shift towards a more male-typical presentation of the brain. Sample probabilities for ASD also increased with predicted probabilities for male-typical brain phenotypes across both sexes. These studies highlight advances in the field of structural neuroimaging research in areas of feature development, clinical translation, and efforts to understand the modulating role of biological sex on the prevalence of ASD. Taken together, the work presented within this thesis thus constitutes an important step toward establishing translational imaging tools for ASD that may one day be applied in the clinical setting.
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Andrenacci, Stefano. "De Bruijn sequences in spread spectrum systems: problems and performance in vehicular applications." Doctoral thesis, Università Politecnica delle Marche, 2012. http://hdl.handle.net/11566/242316.
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Questa tesi affronta l’analisi circa il possibile utilizzo di un particolare set
di sequenze, le cosiddette sequenze de Bruijn, in un sistema radar veicolare di
tipo Direct Sequence Spread Spectrum (DSSS). Rispetto ad altri codici di espansione
adottati nei sistemi DSSS, maggiore è la lunghezza delle sequenze del
set, più la numerosità delle sequenze di de Bruijn aumenta in modo esponenziale
e permette teoricamente di assegnare ad ogni radar una diversa sequenza
generata, che funge da specifica chiave personale. In questo modo è possibile
sviluppare un sistema radar autoconsistente in grado di lavorare senza
alcuna infrastruttura necessaria all’assegnazione delle sequenze, come accade
per i convenzionali codici di espansione tipo i codici Gold o i codici di Kasami.
Grazie alle loro favorevoli proprietà di auto- e cross-correlazione, sono particolarmente
indicati per sistemi automotive dove è molto importante rilevare con
precisione un bersaglio in un contesto di radar multi-utente. Considerando le
loro buone proprietà di correlazione e la loro elevata numerosità, le sequenze
di de Bruijn possono essere utilizzate non solo nei sistemi radar veicolari ma
anche in altri scenari di tipo Spread Spectrum, come il canale di downlink
e uplink di sistemi DS-CDMA. Infatti, le sequenze di de Bruijn, nella versione
standard, se selezionate accuratamente hanno proprietà di ortogonalità
e quindi particolarmente vantaggioso è il loro utilizzo nel canale di downlink
di un sistema DS-CDMA. Inoltre, dal set di sequenze di de Bruijn è possibile
derivare un altro particolare insieme di sequenze, le cosiddette sequenze di de
Bruijn modificate. Queste sequenze mostrano prestazioni migliori in termini di
cross-correlazione e potrebbero essere utilizzate nel canale uplink di un sistema
DS-CDMA. Al fine di verificare le prestazioni in un vero e proprio banco di
prova, è stata sviluppata anche una preliminare implementazione di un radar
DSSS su Software Defined Radio. Infine è stato sviluppato un simulatore per
sistemi radar veicolari DSSS su scenari multi-utente. L’analisi effettuata ed
i risultati sulle prestazioni ottenuti suggeriscono di evolvere questa soluzione
verso le recenti tecniche di radar cognitivo tramite l’ausiliodi tecniche di visione
computazionale.This thesis deals with the analysis about a possible utilization of a particular set of sequences, the so-called de Bruijn sequences, in a Direct Sequence Spread Spectrum (DSSS) vehicular radar system. Compared with other spreading codes adopted in DSSS systems, the greater the span of the set is, the more the number of de Bruijn sequences exponentially increases and theoretically permits to assign each radar a different generated sequence, as a specific key. By this way it is possible to develop a self-consistent radar system, which is able to work without any infrastructure required to assign sequences, as it happens in the case conventional spreading codes, like Gold codes or Kasami codes, are adopted. Due to their both favourable auto- and cross-correlation properties they are particularly indicated for automotive systems in which there are the needs of detecting accurately a target and performing in a multi-user radar environment. Considering their good correlation properties and their huge number, de Bruijn sequences could be used not only in vehicular radar systems but also in other Spread Spectrum and so, they are evaluated in various scenarios like downlink and uplink channel of DS-CDMA systems. In fact, in standard version de Bruijn sequences, if accurately selected, have the property of orthogonality and so they are tested in a downlink channel of a DS-CDMA system. In addition, from de Bruijn sequences another particular set of sequences, the so-called modified de Bruijn sequences, can be derived. These sequences show better performance in terms of cross-correlation properties and could be used in uplink channel of DS-CDMA system. In order to verify the performance in a real test-bed, a preliminary implementation on Software Defined Radios is also developed. Finally they are adopted and compared in simulated multiuser DSSS radar scenarios. The analysis done and the performance results obtained suggest to evolve this radar solution to a cognitive radar approach using computer vision systems as external aid sensor which can outperform actual solutions.
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Li, He. "Privacy and Authentication in Emerging Network Applications." Diss., Virginia Tech, 2021. http://hdl.handle.net/10919/101786.
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In this dissertation, we studied and addressed the privacy-preserving and authentication
techniques for some network applications, where existing internet security solutions cannot
address them straightforwardly due to different trust and attack models and possibly constrained
resources. For example, in a centralized dynamic spectrum access (DSA) system,
the spectrum resource licensees called incumbent users (IUs), have strong operational privacy
requirements for the DSA service provider called spectrum access system (SAS), and
hence SAS is required to perform spectrum computation without knowing IUs' operational
information. This means SAS can at most be considered as a semi-trusted party which is
honest but curious, and common anonymization and end-to-end encryption cannot address
this issue, and dedicated solutions are required. Another example is that in an intra-vehicle
Controller Area Network (CAN), the transmitter can only embed 64 bits of message and
its authentication tag into on message frame, which makes it difficult to achieve message
authentication in real-time with sufficient cryptographic strength. The focus of this dissertation
is to fill the gap of existing solutions with stronger security notion and practicability.
On the topic of privacy-preserving DSA systems, we firstly explored existing solutions and
proposed a comparative study. We additionally proposed a new metric for evaluation and
showed the advantages and disadvantages of existing solutions. We secondly studied the IU
location privacy in 3.5GHz band ESC-based DSA system and proposed a novel scheme called
PriDSA. PriDSA addresses malicious colluding SAS attack model through leveraging different
and relatively lightweight cryptography primitive with novel design, granting stronger security notion and improved efficiency as well. We thirdly studied the operational privacy of
both IU and secondary users (SUs) in a general centralized SAS based DSA system and proposed
a novel framework called PeDSS. Through our novel design that integrates differential
privacy with secure multi-party computation protocol, PeDSS exhibits great communication
and computation overhead compared to existing solutions.
On the topic of lightweight message authentication in resource-constrained networks, we
firstly explored message authentication schemes with high cryptographic strength and low
communication-overhead and proposed a novel scheme called CuMAC. CuMAC provides
a flexible trade-off between authentication delay and cryptographic strength, through the embodiment of a novel concept that we refer to as accumulation of cryptographic strength.
We secondly explored the possibility of achieving both high cryptographic strength and low
authentication delay and proposed a variant of CuMAC called CuMAC/S. By employing the
novel idea of message speculation, CuMAC/S achieves enables the accumulation of cryptographic strength while incurring minimal delay when the message speculation accuracy is
high.Doctor of Philosophy
The privacy-preserving and message authentication issues of some network applications are distinctive from common internet security due to different attack models and possibly constrained resources, and these security and privacy concerns cannot be addressed by applying existing internet security solutions straightforwardly. For example, in a centralized dynamic spectrum access (DSA) system, the spectrum resource licensees called incumbent users (IUs), have strong operational privacy requirements for the DSA service provider called spectrum access system (SAS), and hence SAS is required to perform spectrum computation without knowing IUs' operational information. This means SAS can at most be considered as a semi-trusted party which is honest but curious, and common anonymization and end-to-end encryption cannot address this issue, and dedicated solutions are required. Another example is that in an intra-vehicle Controller Area Network (CAN), the transmitter can only embed 64 bits of message and its authentication tag into on message frame, which makes it difficult to achieve message authentication in real-time with sufficient cryptographic strength. We addressed the privacy issue of DSA systems by proposing novel schemes incorporating efficient cryptographic primitives and various privacy-preserving techniques, achieving a greatly higher efficiency or stronger privacy-preserving level. We addressed the lightweight authentication issue of resource-constrained networks by employing the novel concept of security accumulation and message speculation, achieving high cryptographic strength, low communication overhead, and probable low latency.
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Bhatnagar, Mohit. "Multiplexing of interferometric fiber optic sensors for smart structure applications using spread spectrum techniques." Thesis, This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-12052009-020246/.
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Sharakhov, Nikita Igorevich. "Web-Based Data Visualization with 3D Portrayals for Communications Applications." Thesis, Virginia Tech, 2014. http://hdl.handle.net/10919/50420.
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The modern web has evolved into a highly capable software platform, which enables near-native performance, while offering installation-free cross-platform applications with a uniform user base and rapid update deployment. SVG, WebGL, and HTML5 Canvas, along with various higher-level JavaScript frameworks allow web applications to drive both 2D and 3D visualization. These technologies allow developing novel visualization applications, which can be applied in the communication domain to geospatially map service quality, and to provide tools research and education in wireless communication. We present two such web applications GeoSpy and CORNET3D.
GeoSpy provides 2D and 3D visualization of geospatial data on the web. The application is primarily focused on leveraging 3D portrayals to increase the number of broadband Quality of Service (QoS) metrics, which can be attached to a single point on a map. Additionally, GeoSpy has proven to be a flexible visualization platform by giving the user a high level of customization over HTTP API data. This allows GeoSpy to venture beyond broadband mapping, and provide 3D portrayals of any well-formatted geospatial JSON API.
Research of Software Defined Radio (SDR) and Dynamic Spectrum Access (DSA) can be used to significantly improve the wireless QoS. CORNET3D provides a 3D view of the Virginia Tech CORNET SDR testbed with information on which nodes and radios are operational. The application can also display 2D and 3D plots of the spectrum, which is sensed by the radios in real time. The data is sent to the client over a WebSocket connection to enable low latency, compared to conventional HTTP. CORNET3D can teach students about strategies for optimal use of spectrum resources through a game---"by providing them with real-time scoring based on their choices for radio transmission parameters. CORNET3D has demonstrated that the not only can web applications provide rich portrayals of real-time sensor data, but can also serve as a 3D "serious game" platform.Master of Science
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Sephus, Nashlie H. "A framework for exploiting modulation spectral features in music data mining and other applications." Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/52243.
Full textAbstract:
When a signal is decomposed into frequency bands, demodulated into modulator and carrier pairs, and portrayed in a carrier frequency-versus modulator frequency domain, significant information may be automatically observed about the signal. We refer to this domain as the modulation spectral domain. The modulation spectrum is referred to as a windowed Fourier transform across time that produces an acoustic frequency versus modulation frequency representation of a signal. Previously, frameworks incorporating the discrete short-time modulation transform (DSTMT) and modulation spectrum have been designed mostly for filtering of speech signals. This modulation spectral domain is rarely, if ever, discussed in typical signal processing courses today, and we believe its current associated tools and applications are somewhat limited. We seek to revisit this domain to uncover more intuition, develop new concepts to extend its capabilities, and increase its applications, especially in the area of music data mining.
A recent interest has risen in using modulation spectral features, which are features in the modulation spectral domain, for music data mining. The field of music data mining, also known as music information retrieval (MIR), has been rapidly developing over the past decade or so. One reason for this development is the aim to develop frameworks leveraging the particular characteristics of music signals instead of simply copying methods previously applied to its speech-centered predecessors, such as speech recognition, speech synthesis, and speaker identification. This research seeks to broaden the perspective and use of an existing modulation filterbank framework by exploiting modulation features well suited for music signals.
The objective of this thesis is to develop a framework for extracting modulation spectral features from music and other signals. The purpose of extracting features from these signals is to perform data mining tasks, such as unsupervised source identification, unsupervised source separation, and audio synthesis. More specifically, this research emphasizes the following: the usefulness of the DSTMT and the modulation spectrum for music data mining tasks; a new approach to unsupervised source identification using modulation spectral features; a new approach to unsupervised source separation; a newly introduced analysis of FM features in an AM-dominated modulation spectra; and other applications.
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Shan, Peijun. "Time-Varying Autoregressive Model Based Signal Processing with Applications to Interference Rejection in Spread Spectrum Communications." Diss., Virginia Tech, 1999. http://hdl.handle.net/10919/39006.
Full textAbstract:
The objective of this research is to develop time-varying signal processing methods for rapidly varying non-stationary signals based on time-varying autoregressive (TVAR) modeling, and to apply such methods to frequency-modulated (FM) interference rejection in direct-sequence spread spectrum (DSSS) communications.
For fast varying non-stationary signal processing, such as the task to reject an FM interference that could chirp over the entire DSSS bandwidth in a symbol interval, an explicit description of the variation is necessary to form a time-varying filter. This is realized using the TVAR model, which is an autoregressive model whose coefficients are time-varying with the variation modeled as a linear combination of a set of known functions of time. In DSSS communications, when the strength of an interference - which could be a hostile jammer or overlaid communication signal - possibly exceeds the inherent spread spectrum processing gain, interference rejection is necessary to secure a usable bit-error-rate.
The contributions of this research include: a) revealed the advantageous performance of TVAR model based instantaneous frequency estimation (TVAR-IF), which is expected to change the prevailing opinion that regards TVAR-IF as a poor estimator; b) proposed a time-varying Prony method to improve TVAR-IF at low SNR; c) proposed to use TVAR-IF for time-varying FIR notch filter based FM jammer suppression in DSSS communications; d) developed TVAR model based time-varying optimum filters, including the TVAR based Kalman filter (TVAR-KF) and the TVAR based Wiener filter (TVAR-WF); e) developed a TVAR-WF based formulation of FM interference soft-cancellation in DSSS communications; and f) proposed a TVAR based linear prediction error (TVAR-LPE) filter for soft-cancellation of FM interference in DSSS communications.
For the interference rejection problem, our TVAR-IF controlled notch filter yields high processing gain close to that using the known IF and much higher than that using the WVD based IF estimate. Furthermore, unlike the IF based notch filter approaches, the proposed soft-cancellation methods utilize the full spectral information captured by the TVAR model. Our soft-cancellation approaches, including TVAR-WF and TVAR-LPE, maintain at least the DSSS system performance expected when no filtering is used, even under estimated conditions. The latter is in contrast to the notch filter based approaches, which may cause deterioration of overall system performance at low jammer-to-signal ratios.Ph. D.
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Craymer, Michael R. "The least squares spectrum, its inverse transform and autocorrelation function, theory and some applications in geodesy." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0025/NQ33898.pdf.
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Gerstein, Rachel. "THE LONG-TERM COURSE OF BIPOLAR SPECTRUM DISORDER: APPLICATIONS OF THE BEHAVIORAL APPROACH SYSTEM (BAS) MODEL." Diss., Temple University Libraries, 2011. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/73971.
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PsychologyPh.D.
In this study, I tested predictions of the Behavioral Approach System (BAS) model as applied to the course of bipolar spectrum disorders. In this model, when a vulnerable individual experiences a BAS activation-relevant event, the weak regulatory strength of the BAS interacts with pre-event BAS state and is likely to lead to hypomania/mania. In contrast, when a vulnerable individual experiences a BAS deactivation-relevant event, the weak regulatory strength of the BAS interacts with pre- event BAS state and is likely to lead to depression. A secondary goal of this study involved comparing the BAS model to the cognitive-vulnerability stress model of bipolar disorder. Toward this end, data from a sample of 217 individuals (112 individuals with a diagnosis in the bipolar spectrum and 105 demographically similar, normal controls) participating in the Longitudinal Investigation of Bipolar Spectrum Disorders (LIBS) Project, a two-site prospective examination of the role of BAS, cognitive styles, and life events in the course of bipolar disorders among college students, were analyzed. The results of this study suggest that there is some support for both the BAS model and the cognitive-vulnerability stress model. Specifically, BAS-relevant cognitive styles, in interaction with congruent positive life events, predicted hypomanic episodes. There was less support for either model in the prediction of depression. There was some support for BAS sensitivity and BAS-relevant events each predicting the course of bipolar disorder. However, there was no support for the interaction of BAS sensitivity and BAS-relevant events predicting the type and number of mood episodes. As such, this study found more support for a BAS-related cognitive vulnerability-stress model, as compared to the "pure" BAS model, as applied to bipolar spectrum disorders. Following a review of the results, strengths and limitations, as well as clinical implications and potential future research directions are discussed.
Temple University--Theses
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Mukherjee, Sayak. "Applications of Field Theory to Reaction Diffusion Models and Driven Diffusive Systems." Diss., Virginia Tech, 2009. http://hdl.handle.net/10919/39293.
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In this thesis, we focus on the steady state properties of two systems which are genuinely out of equilibrium. The first project is an application of dynamic field theory to a specific non equilibrium critical phenomenon, while the second project involves both simulations and analytical calculations. The methods of field theory are used on both these projects. In the first part of this thesis, we investigate a generalization of the well-known field theory for directed percolation (DP). The DP theory is known to describe an evolving population, near extinction. We have coupled this evolving population to an environment with its own nontrivial spatio-temporal dynamics. Here, we consider the special case where the environment follows a simple relaxational (model A) dynamics. We find two marginal couplings with upper critical dimension of four, which couple the two theories in a nontrivial way. While the Wilson-Fisher fixed point remains completely unaffected, a mismatch of time scales destabilizes the usual DP fixed point. Some open questions and future work remain.
In the second project, we focus on a simple particle transport model far from equilibrium, namely, the totally asymmetric simple exclusion process (TASEP). While its stationary properties are well studied, many of its dynamic features remain unexplored. Here, we focus on the power spectrum of the total particle occupancy in the system. This quantity exhibits unexpected oscillations in the low density phase. Using standard Monte Carlo simulations and analytic calculations, we probe the dependence of these oscillations on boundary effects, the system size, and the overall particle density. Our simulations are fitted to the predictions of a linearized theory for the fluctuation of the particle density. Two of the fit parameters, namely the diffusion constant and the noise strength, deviate from their naive bare values [6]. In particular, the former increases significantly with the system size. Since this behavior can only be caused by nonlinear effects, we calculate the lowest order corrections in perturbation theory. Several open questions and future work are discussed.Ph. D.
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Alkanjo, Hasan. "Spectre étendu des opérateurs et applications." Thesis, Lyon 1, 2014. http://www.theses.fr/2014LYO10271/document.
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Cette thèse s'articule autour d'une notion spectrale assez récente, appelée le spectre étendu des opérateurs. Dans la première partie nous fournissons des propriétés générales du spectre étendu d'un opérateur dans certains cas particuliers, tels que le cas de dimension finie et celui des opérateurs inversibles. Nous nous intéressons dans la deuxième partie à l'étude du spectre étendu de l'opérateur shift tronqué Su. En particulier, nous donnons une description complète des vecteurs propres étendus associes à chaque valeur propre étendue de Sb, ou b est un produit de Blaschke quelconque. Dans la troisième partie nous décrirons complètement le spectre étendu et les sous espaces propres étendus d'une classe d'opérateurs très importante : celle des opérateurs normaux. Nous commençons d'abord par la classe des opérateurs qui sont produits d'un opérateur positif par un autoadjoint. Ensuite, nous utilisons le théorème de Fuglede-Putnam pour déduire une description complète des valeurs et des vecteurs propres étendus des opérateurs normaux, en fonction de leur mesure spectrale. Dans la dernière partie, nous appliquons nos résultats des trois premières parties sur des exemples concrets. En particulier, nous traitons= le problème des sous espaces propres étendus des opérateurs définis dans un espace de dimension finie. Ensuite, nous montrons l'existence d'un opérateur compact quasinilpotent dont le spectre étendu est réduit au singleton {1}. Enfin, nous traitons deux opérateurs de Cesaro très importants dans les applicationsThis thesis is based on a relatively new spectral notion, called extended spectrum of operators. In the first part, we provide general properties of extended spectrum of an operator in some special cases, such as the case of finite dimension and the case of invertible operator. We focused in the second part on characterizing the extended spectrum of truncated shift operator Su. In particular, we give a complete description of the extended eigenvectors associated to each extended eigenvalue of Sb, where b is a Blaschke product. In the third part, we describe the extended spectrum and the extended eigenvectors of a very important class of operators , that is the normal operators. We first start by describing these last sets for the product of a positive and a self-adjoint operator which are both injective. After, we use the Fuglede-Putnam theorem to describe the same sets for normal operators, in terms of their spectral measure. In the last part, we apply our results from the last three parts on concrete examples. In particular, we address the problem of extended eigenvectors of operators defined in a finite dimension space. Next, we show the existence of a quasinilpotent compact operator whose extended spectrum is reduced to {1}. Finally, we study two Cesaro operators which are very important in applications