Comparison of multiple-input single-output single-user ultra-wideband systems with pre-distortion

This paper presents a performance analysis of a baseband multiple-input single-output ultra-wideband system over scenarios CM1 and CM3 of the IEEE 802.15.3a channel model, incorporating four different schemes of pre-distortion: time reversal, zero-forcing pre-equaliser, constrained least squares pre-equaliser, and minimum mean square error pre-equaliser. For the third case, a simple solution based on the steepest-descent (gradient) algorithm is adopted and compared with theoretical results. The channel estimations at the transmitter are assumed to be truncated and noisy. Results show that the constrained least squares algorithm has a good trade-off between intersymbol interference reduction and signal-to-noise ratio preservation, providing a performance comparable to the minimum mean square error method but with lower computational complexity. Copyright (C) 2011 John Wiley & Sons, Ltd.

Experiments on through-wall imaging using ultra wideband radar

Through-wall imaging (TWI) may provide vital information on interior environment in cases when physically entering such environment would pose danger to the person involved. The concept of ultra wideband radar (UWB radar) is an emerging technology, which offers high spatial resolution, as opposed to narrow band radars. Thus, TWI applications using UWB radar have become a growing field of research with several applications in the civil and defense areas such as rescue and surveillance. For this study, a prototype system of UWB radar to TWI has been built. Analyses and result to several kinds of experiments have been presented, that is, detection and visualization of metallic targets behind wooden board wall and concrete blocks wall. The results are encouraging and show the advantages of using UWB radar for TWI. (C) 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett, 54:339-344, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26543

SEARCH FOR POINT-LIKE SOURCES OF ULTRA-HIGH ENERGY NEUTRINOS AT THE PIERRE AUGER OBSERVATORY AND IMPROVED LIMIT ON THE DIFFUSE FLUX OF TAU NEUTRINOS

The surface detector array of the Pierre Auger Observatory can detect neutrinos with energy E-nu between 10(17) eV and 10(20) eV from point-like sources across the sky south of +55 degrees and north of -65 degrees declinations. A search has been performed for highly inclined extensive air showers produced by the interaction of neutrinos of all flavors in the atmosphere (downward-going neutrinos), and by the decay of tau leptons originating from tau neutrino interactions in Earth's crust (Earth-skimming neutrinos). No candidate neutrinos have been found in data up to 2010 May 31. This corresponds to an equivalent exposure of similar to 3.5 years of a full surface detector array for the Earth-skimming channel and similar to 2 years for the downward-going channel. An improved upper limit on the diffuse flux of tau neutrinos has been derived. Upper limits on the neutrino flux from point-like sources have been derived as a function of the source declination. Assuming a differential neutrino flux k(PS) . E-nu(-2). from a point-like source, 90% confidence level upper limits for k(PS) at the level of approximate to 5x10(-7) and 2.5x10(-6) GeV cm(-2) s(-1) have been obtained over a broad range of declinations from the searches for Earth-skimming and downward-going neutrinos, respectively.

Ultra-low friction coefficient in alumina-silicon nitride pair lubricated with water

In a ball-on-disc wear test, an alumina ceramic body sliding against a silicon nitride ceramic body in water achieved an ultra-low friction coefficient (ULFC) of 0.004. The profilometer and EDX measurements indicated that the ULFC regime in this unmated Al2O3-Si3N4 pair was achieved because of the formation of a flat and smooth interface of nanometric roughness, which favored the hydrodynamic lubrication. The triboreactions formed silicon and aluminum hydroxides which contributed to decrease roughness and shear stress at the contact interface. This behavior enables the development of low energy loss water-based tribological systems using oxide ceramics. 13 2012 Elsevier B.V. All rights reserved.

Densification and enhancement of the grain boundary conductivity of gadolinium-doped barium cerate by ultra fast flash grain welding

Doped barium cerate is a promising solid electrolyte for intermediate temperature fuel cells as a protonic conductor. However, it is difficult to sinter it to high density at a reasonable temperature. Moreover, it presents a high grain boundary resistivity at intermediate temperatures. Flash grain welding was applied to compacted samples, starting from a temperature of 910 degrees C and applying, for a short time, an ac electric polarization of 40 V, 1000 Hz. At that frequency, the resulting current flows through the grain boundaries promoting a welding via a local Joule heating. A large decrease of the grain boundary resistivity was observed by impedance spectroscopy. Scanning electron microscopy observations of polished and etched surfaces revealed highly sintered regions. Attempts were also made to combine flash grain welding with conventional sintering. (C) 2012 Elsevier Ltd. All rights reserved.

Ultra-structural mapping of sugarcane bagasse after oxalic acid fiber expansion (OAFEX) and ethanol production by Candida shehatae and Saccharomyces cerevisiae

Background Diminishing supplies of fossil fuels and oil spills are rousing to explore the alternative sources of energy that can be produced from non-food/feed-based substrates. Due to its abundance, sugarcane bagasse (SB) could be a model substrate for the second-generation biofuel cellulosic ethanol. However, the efficient bioconversion of SB remains a challenge for the commercial production of cellulosic ethanol. We hypothesized that oxalic-acid-mediated thermochemical pretreatment (OAFEX) would overcome the native recalcitrance of SB by enhancing the cellulase amenability toward the embedded cellulosic microfibrils. Results OAFEX treatment revealed the solubilization of hemicellulose releasing sugars (12.56 g/l xylose and 1.85 g/l glucose), leaving cellulignin in an accessible form for enzymatic hydrolysis. The highest hydrolytic efficiency (66.51%) of cellulignin was achieved by enzymatic hydrolysis (Celluclast 1.5 L and Novozym 188). The ultrastructure characterization of SB using scanning electron microscopy (SEM), atomic force microscopy (AFM), Raman spectroscopy, Fourier transform–near infrared spectroscopy (FT-NIR), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD) revealed structural differences before and after OAFEX treatment with enzymatic hydrolysis. Furthermore, fermentation mediated by C. shehatae UFMG HM52.2 and S. cerevisiae 174 showed fuel ethanol production from detoxified acid (3.2 g/l, yield 0.353 g/g; 0.52 g/l, yield, 0.246 g/g) and enzymatic hydrolysates (4.83 g/l, yield, 0.28 g/g; 6.6 g/l, yield 0.46 g/g). Conclusions OAFEX treatment revealed marked hemicellulose degradation, improving the cellulases’ ability to access the cellulignin and release fermentable sugars from the pretreated substrate. The ultrastructure of SB after OAFEX and enzymatic hydrolysis of cellulignin established thorough insights at the molecular level.

Prodromal Questionnaire: translation, adaptation to Portuguese and preliminary results in ultra-high risk individuals and first episode psychosis

OBJECTIVE: The Prodromal Questionnaire (PQ) is a 92-item self-report screening tool for individuals at ultra-high risk (UHR) to develop psychosis. This study aims to present the translation to Portuguese and preliminary results in UHR and first episode (FE) psychosis in a Portuguese sample. METHODS: The PQ was translated from English to Portuguese by two bilingual researchers from the research program on early psychosis of the Instituto de Psiquiatria HCFMUSP, São Paulo, Brazil (ASAS - "Evaluation and Follow up of Adolescents and Young Adults in São Paulo") and back translated by two other researchers. The study participants (n = 11-) were evaluated through the Portuguese version of the Prodromal Questionnaire (PQ) and SIPS. RESULTS: The individuals at UHR (n = 7) presented a lower score than first episode patients (n = 4). The UHR mean scores and standard deviation on Portuguese version of the PQ were: 13.0 ± 10.0 points on positive symptoms subscale, and FE patients: 33.0 ± 10.0. CONCLUSION: The UHR and FE patients' of this study presented PQ scores similar to the ones found in the literature; what suggests that it is possible to use the PQ in Brazilian help-seeking individuals as a screening tool.

Bounds on the density of sources of ultra-high energy cosmic rays from the Pierre Auger Observatory

We derive lower bounds on the density of sources of ultra-high energy cosmic rays from the lack of significant clustering in the arrival directions of the highest energy events detected at the Pierre Auger Observatory. The density of uniformly distributed sources of equal intrinsic intensity was found to be larger than ~(0.06 - 5) × '10 POT. -4' 'Mpc POT. -3' at 95% CL, depending on the magnitude of the magnetic deflections. Similar bounds, in the range (0.2 - 7) × '10 POT. -4' 'Mpc POT. -3', were obtained for sources following the local matter distribution.

Efeitos da Prostaglandina E1 na gênese de capilares sanguíneos em músculo esquelético isquêmico de ratos: estudo histológico e ultra-estrutural

Objetivo: o objetivo deste trabalho foi estudar os aspectos morfológicos e ultra-estruturais na gênese de capilares sanguíneos em músculo esquelético do membro caudal de ratos submetidos à isquemia sob a ação da Prostaglandina E1 (PGE1), administrada por via intramuscular ou endovenosa. Métodos: foram utilizados 60 ratos (Rattus norvegicus albinus), linhagem Wistar-UEM, distribuídos aleatoriamente em três grupos de 20, redistribuídos igualmente em dois subgrupos, observados no 7o e 14o dias, sendo um grupo controle onde apenas foi provocada a isquemia no membro, outro com a isquemia e a injeção da PGE1 via intramuscular (IM), e outro com a isquemia e a injeção da PGE1 endovenosa (EV). Para análise dos resultados, foram realizadas a coloração com hematoxilina & eosina (HE), a imuno-histoquímica e a microscopia eletrônica de transmissão (MET). Resultados: constatou-se um aumento estatisticamente significante no número de capilares nos subgrupos com o uso da PGE1 IM e EV, através da contagem nos cortes corados com HE. Houve marcação de capilares e vasos de maior calibre nestes mesmos subgrupos, porém, esta reação não foi eficiente para a quantificação dos capilares. Na MET encontraram-se evidências de formação de novos capilares. Conclusões: a PGE1, administrada por via IM ou EV, promoveu, após 14 dias de observação, um aumento no número de capilares no músculo esquelético de ratos submetido à isquemia, identificáveis histologicamente com a coloração em HE. Na análise ultra-estrutural encontraram-se alterações que sugerem, nos animais sob a ação da PGE1, que a neoformação vascular possa ter ocorrido por angiogênese e vasculogênese. A imuno-coloração, apesar da marcação de capilares e vasos maiores, não permitiu estabelecer uma correlação com o aumento de vasos encontrados na coloração com HE.

Diseño de un Amplificador de Bajo Ruido de Ultra Banda Ancha para un Receptor de UWB en CMOS 0.35 μm

Presentación del Proyecto Fin de Carrera titulado "Diseño de un Amplificador de Bajo Ruido de Ultra Banda Ancha para un Receptor de UWB en CMOS 0.35 μm"

Diseño de un amplificador distribuido para ultra wide band basado en HBT de la tecnología SIGE 0.35 μm de AMS

Memoria y presentación del Proyecto Fin de Carrera titulado "DISEÑO DE UN AMPLIFICADOR DISTRIBUIDO PARA ULTRA WIDE BAND BASADO EN HBT DE LA TECNOLOGÍA SIGE 0.35 μm DE AMS"

Design of radio frequency integrated circuits for ultra wide band communications

Programa de doctorado: Tecnologías de Telecomunicación Avanzadas

Determinación de quince compuestos hormonales en aguas depuradas usando extracción en fase sólida combinada con cromatografía líquida de ultra resolución con detección de espectrometría de masas (SPE-UHPLC-MS/MS)

Universidad de Las Palmas de Gran Canaria, Facultad de Ciencias del Mar, Doctorado en Gestión Costera

Spectrum shaping and its application: spread-spectrum clock generator and circuits for ultra wide band

Electromagnetic spectrum can be identified as a resource for the designer, as well as for the manufacturer, from two complementary points of view: first, because it is a good in great demand by many different kind of applications; second, because despite its scarce availability, it may be advantageous to use more spectrum than necessary. This is the case of Spread-Spectrum Systems, those systems in which the transmitted signal is spread over a wide frequency band, much wider, in fact, than the minimum bandwidth required to transmit the information being sent. Part I of this dissertation deals with Spread-Spectrum Clock Generators (SSCG) aiming at reducing Electro Magnetic Interference (EMI) of clock signals in integrated circuits (IC) design. In particular, the modulation of the clock and the consequent spreading of its spectrum are obtained through a random modulating signal outputted by a chaotic map, i.e. a discrete-time dynamical system showing chaotic behavior. The advantages offered by this kind of modulation are highlighted. Three different prototypes of chaos-based SSCG are presented in all their aspects: design, simulation, and post-fabrication measurements. The third one, operating at a frequency equal to 3GHz, aims at being applied to Serial ATA, standard de facto for fast data transmission to and from Hard Disk Drives. The most extreme example of spread-spectrum signalling is the emerging ultra-wideband (UWB) technology, which proposes the use of large sections of the radio spectrum at low amplitudes to transmit high-bandwidth digital data. In part II of the dissertation, two UWB applications are presented, both dealing with the advantages as well as with the challenges of a wide-band system, namely: a chaos-based sequence generation method for reducing Multiple Access Interference (MAI) in Direct Sequence UWB Wireless-Sensor-Networks (WSNs), and design and simulations of a Low-Noise Amplifier (LNA) for impulse radio UWB. This latter topic was studied during a study-abroad period in collaboration with Delft University of Technology, Delft, Netherlands.