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Search Results: 1 - 10 of 152097 matches for " Jo?o Xavier;Oliveira "
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Robust Simultaneous Localization of Nodes and Targets in Sensor Networks Using Range-Only Measurements
P\inar O\uguz-Ekim,Joo Gomes,Joo Xavier,Paulo Oliveira
Mathematics , 2010,
Abstract: Simultaneous localization and tracking (SLAT) in sensor networks aims to determine the positions of sensor nodes and a moving target in a network, given incomplete and inaccurate range measurements between the target and each of the sensors. One of the established methods for achieving this is to iteratively maximize a likelihood function (ML), which requires initialization with an approximate solution to avoid convergence towards local extrema. This paper develops methods for handling both Gaussian and Laplacian noise, the latter modeling the presence of outliers in some practical ranging systems that adversely affect the performance of localization algorithms designed for Gaussian noise. A modified Euclidean Distance Matrix (EDM) completion problem is solved for a block of target range measurements to approximately set up initial sensor/target positions, and the likelihood function is then iteratively refined through Majorization-Minimization (MM). To avoid the computational burden of repeatedly solving increasingly large EDM problems in time-recursive operation an incremental scheme is exploited whereby a new target/node position is estimated from previously available node/target locations to set up the iterative ML initial point for the full spatial configuration. The above methods are first derived under Gaussian noise assumptions, and modifications for Laplacian noise are then considered. Analytically, the main challenges to be overcome in the Laplacian case stem from the non-differentiability of $\ell_1$ norms that arise in the various cost functions. Simulation results confirm that the proposed algorithms significantly outperform existing methods for SLAT in the presence of outliers, while offering comparable performance for Gaussian noise.
Approximate Maximum Likelihood Source Localization from Range Measurements Through Convex Relaxation
P?nar O?uz-Ekim,Joo Gomes,Joo Xavier,Marko Sto?i?,Paulo Oliveira
Mathematics , 2011,
Abstract: This work considers the problem of locating a single source from noisy range measurements to a set of nodes in a wireless sensor network. We propose two new techniques that we designate as Source Localization with Nuclear Norm (SLNN) and Source Localization with l1-norm (SL-l1), which extend to arbitrary real dimensions, including 3D, our prior work on 2D source localization formulated in the complex plane. Broadly, our approach is based on formulating a Maximum-Likelihood (ML) estimation problem for the source position, and then using convex relaxation techniques to obtain a semidefinite program (SDP) that can be globally and efficiently solved. SLNN directly approximates the Gaussian ML solution, and the relaxation is shown to be tighter than in other methods in the same class. We present an analysis of the convexity properties of the constraint set for the 2D complex version of SLNN (SLCP) to justify the observed tightness of the relaxation. In terms of global accuracy of localization, SLNN outperforms state-of-the-art optimization-based methods with either iterative or closed-form formulations. We propose the SL-l1 algorithm to address the Laplacian noise case, which models the presence of outliers in range measurements. We overcome the nondifferentiability of the Laplacian likelihood function by rewriting the ML problem as an exact weighted version of the Gaussian case, and compare two solution strategies. One of them is iterative, based on block coordinate descent, and uses SLNN as a subprocessing block. The other, attaining only slightly worse performance, is noniterative and based on an SDP relaxation of the weighted ML problem.
CO2, Er: YAG and Nd:YAG lasers in endodontic surgery
Pozza, Daniel Humberto;Fregapani, Patrícia Wehmeyer;Xavier, Cristina Braga;Weber, Joo Batista Blessmann;Oliveira, Marília Gerhardt de;
Journal of Applied Oral Science , 2009, DOI: 10.1590/S1678-77572009000600011
Abstract: objectives: co2, er:yag and nd:yag lasers have been used in endodontic surgery. this in vitro study evaluated 1% rhodamine b dye penetration using computer-assisted morphometry (imagetool software?) of 108 endodontically treated human permanent canines. material and methods: teeth were divided into 9 groups according to the technique used: a: 90-degree apicoectomy with bur, root-end cavity preparation with ultrasound and filled with mta; b: 90-degree apicoectomy with bur, root-end cavity prepared with ultrasound and filled with mta, and treatment of apical surface with co2 laser (1 w, cw/cw); c: 90-degree apicoectomy with bur, and treatment of apical surface with nd:yag laser (150 mj, 10 hz); d: 90-degree apicoectomy with bur, and treatment of apical surface with co2 laser,(1 w, cw/cw); e: apicoectomy with er:yag laser (400 mj, 10 hz), root-end cavity prepared with ultrasound and filled with mta; f: apicoectomy with er:yag laser (400 mj, 10 hz) and treatment of apical surface with nd:yag laser (150 mj, 10hz); g: apicoectomy with co2 laser (5w, cw/sp), root-end cavity prepared with ultrasound and filled with mta; h: irradiation of apical end with co2 laser (1 w, cw/cw); i: irradiation of apical end with nd:yag laser (150 mj, 10 hz). results: dye penetration was found in all specimens at different rates, the lowest penetration occurring in groups c (16.20%), b (17.24%) and f (17.84%). conclusions: groups b, c and f represent the best technical sequences to perform endodontic surgery.
Fígado: vasculariza??o colateral após isquemia induzida por clampeamento da aorta torácica
OLIVEIRA, Joo César Dias;RAISER, Alceu Gaspar;GUIMAR?ES, Luciana Dambrósio;FARIA, Renato Xavier;HIPPLER, Ricardo Alexandre;
Brazilian Journal of Veterinary Research and Animal Science , 1999, DOI: 10.1590/S1413-95961999000500001
Abstract: the visual observation and identification of the vessels that irrigate the corporal tissues is greatly facilitated by using special staining dyes and vessel distenders, or by using a positive vascular contrast solution. in this research, lateral intercostal thoracotomy was performed on the eighth intercostal space in the left side of 22 dogs followed by clamping of thoracic aorta ± 1 cm cranial to the diaphragm. ten dogs were then injected with the gelatin/aniline mixture, and the other 12 dogs were given a positive vascular contrast solution. in summary, following clamping of the thoracic aorta, arteries that irrigate the diaphragm, but not the liver, were identified.
Anestesia tópica associada à seda??o para facoemulsifica??o: experiência com 312 pacientes
Bertrand, Romero Henrique Carvalho;Garcia, Joo Batista Santos;Oliveira, Caio Márcio Barros de;Bertrand, Adriana Leite Xavier;
Revista Brasileira de Anestesiologia , 2008, DOI: 10.1590/S0034-70942008000100004
Abstract: background and objectives: the use of topical anesthesia in cataract surgeries has been increasing, especially after the development of phacoemulsification. the objective of this study was to evaluate the efficacy of topical anesthesia associated with sedation for cataract extraction by phacoemulsification. methods: a prospective study was conducted with 312 patients, asa i and ii, ages 41 to 89 years. phacoemulsification was performed under topical anesthesia (5 minutes before surgery, by dripping 0.5% proximetacaine) associated with sedation (intravenous midazolam, 1 mg, administered 15 minutes before the surgery). intravenous bolus of alfentanil, 125 μg, were administered under demand. parameters, such as intraoperative pain, consumption of alfentanil, side effects, recovery time, and level of patient satisfaction were analyzed. results: in the intraoperative period, 8 (2.6%) cases of bradycardia, 4 (1.3%) of epithelial edema, 2 (0.65%) of nausea, and 2 (0.65%) ruptures of the posterior capsule were observed. in the postoperative period, 15 (4.8%) cases of nausea, 6 (1.9%) cases of dizziness, 2 (0.65%) of vomiting, and 1 (0.32%) case of bradycardia were observed. the mean time of postoperative recovery was 21.77 minutes. consumption of alfentanil varied from 125 μg to 1250 μg, with a mean consumption of 537 μg. tree hundred (96.2%) patients classified the technique as good and 12 (3.8%), as regular. forty-two patients complained of pain sometime during surgery, and 4 (1.3%) patients said that if they needed another phacoemulsification, they would not like to undergo the same anesthetic technique. conclusions: in this study, topical anesthesia with sedation of patients undergoing cataract removal by phacoemulsification demonstrated to be effective, easy to apply, and had a very low incidence of complications.
Efeitos do meio de cultura e da rela??o BAP/ANA na multiplica??o in vitro de clones de Eucalyptus grandis x E. urophylla em biorreator de imers?o temporária
Oliveira, Mila Liparize de;Xavier, Aloisio;Penchel Filho, Ricardo Miguel;Otoni, Wagner Campos;Teixeira, Joo Batista;
Revista árvore , 2011, DOI: 10.1590/S0100-67622011000700007
Abstract: three individual experiments were conducted in order to test different culture media and bap/naa combinations on the multiplication of eucalyptus grandis x e. urophylla clones using the temporary immersion bioreactor rita?. the ms medium and the frequency of immersion every two hours promoted the highest fresh weight and number of shoots per explant. however, cultures growth were different between the two clones evaluated. the combination of 1.0 μm bap and 0.5 μm naa promoted the greatest means in relation to fresh weight and number of shoots. the cultures presented high percentages of hyperhydricity and this physiological disorder was a limiting factor in the condition of this study eucalyptus cultivation in bioreactors.
Likely Rainfall for Alegre-ES by the Gamma Probability Distribution
Joo Paulo Bestete de Oliveira,Roberto Avelino Cecílio,Alexandre Candido Xavier,Andrea Pinheiro dos Santos Jasper
Engenharia Ambiental : Pesquisa e Tecnologia , 2010,
Abstract: The objective of this study was to estimate rainfall expected for Alegre-ES by the gamma distribution. We used rainfall data covering the period from 1940 to 2007. The parameters α and β of the gamma distribution were obtained by the method of maximum likelihood. Probable rainfall were obtained by the inverse function. We used the test of Kolmogorov-Smirnov test to check the fit of estimated to observed data. The results indicated that the gamma distribution provided a good fit to the data of rain to Alegre-ES can therefore be used to estimate the likely monthly rainfall.
Chemical and structural characterization of soil humic substances under agroforestry and conventional systems
Moraes, Gislane M. de;Xavier, Francisco Alisson da Silva;Mendon?a, Eduardo de Sá;Araújo Filho, Joo Ambrósio de;Oliveira, Teógenes Senna de;
Revista Brasileira de Ciência do Solo , 2011, DOI: 10.1590/S0100-06832011000500014
Abstract: studies have proven that the agroforestry systems in the semi-arid region of the state of ceará, brazil, induce an increase in soil organic c levels. notwithstanding, there is no information if this increase also results in qualitative changes in different pools of soil organic matter. the objective of this study was to verify the possible chemical and structural alterations in fulvic and humic acids of a luvisol in areas adopting agroforestry, traditional intensive cultivation and native forest in a long-term experiment conducted in the semi-arid region of ceará state, brazil. the study was conducted in an experimental area of the national goat research center (embrapa) in sobral, ce. the following treatments were evaluated: agrosilvopasture (agp), silvopasture (silv), intensive cultivation under fallow (icf), and areas with native forest (nf). soil fulvic and humic acids fractions were extracted from the 0-6 and 6-12 cm layers and characterized by elemental composition, thermogravimetry and infrared spectroscopy analyses. the elemental composition analysis of humic acids confirmed the data found for fulvic acids, showing reduction in the c, h and n levels, followed by an increase in o contents in the agp and icf treatments over silv and nf. in all treatments, except to silv in the 0-6 cm layer, the percentage of mass loss was highest (300-600 °c) for humic acids in the thermally most stable region. despite the similarity between infrared spectra, soil fulvic acids in the silv treatment extracted from 6-12 cm depth decrease the absorption bands at 1708 and 1408 cm-1 followed by an increase in the absorption band at 1608 cm-1 attributed to aromatic c=c groups. this behavior suggests an increase in the aromatic character of the structure. the agp and icf treatments, which increase the soil tilling, favored the maintenance of humic substances with a more aromatic character in the soil than silv and nf. the less aromatic humic substances in the silv treatment resulted
Fra??es de nitrogênio em Luvissolo sob sistemas agroflorestais e convencional no semi-árido cearense
Maia, Stoécio Malta Ferreira;Xavier, Francisco Alisson da Silva;Oliveira, Teógenes Senna de;Mendon?a, Eduardo de Sá;Araújo Filho, Joo Ambrósio;
Revista Brasileira de Ciência do Solo , 2008, DOI: 10.1590/S0100-06832008000100036
Abstract: the agroforestry systems have been widely promoted as one sustainable agricultural system, mainly for developing areas, where the external use of resources are not feasible. the aim of this study was to evaluate the impact of one conventional and four agroforestry systems on the contents of total soil nitrogen, mineral nitrogen and different organic nitrogen fractions after five years of experimental cultivation on a luvisol (alfisol). the study area was in the semi-arid zone at the national caprine research center (cnpc) of embrapa, ceará, brazil. the following treatments were tested: agrosilvopasture (agp), silvopasture (silv), traditional agroforestry in 1998 and 1999 (tr98), traditional agroforestry in 2002 (tr02), conventional cropping (cc), and seasonally dry native vegetation ("caatinga") (ca). total-n, n-nh4+, n-no3-, microbial-n, light organic matter n (free and occluded) and n in the humic substances were evaluated. results indicated high nitrate-n (no3-) content in all treatments, accounting for 10.3 to 23.5 % of the total n. the cc treatment reduced the total n and n in humic substances by 38 and 44 %, respectively. the agp and tr98 agroforestry treatments significantly reduced n in the light organic matter and in humic substances. on the other hand, the silv system preserved, and in some cases, improved the concentration of the soil. this system can therefore be recommended as a sustainable alternative for soil management in the semi-arid region of ceará state.
Impactos de sistemas agroflorestais e convencional sobre a qualidade do solo no semi-árido cearense
Maia, Stoécio Malta Ferreira;Xavier, Francisco Alisson da Silva;Oliveira, Teógenes Senna de;Mendon?a, Eduardo de Sá;Araújo Filho, Joo Ambrósio de;
Revista árvore , 2006, DOI: 10.1590/S0100-67622006000500018
Abstract: the environmental benefits of agroforestry system are well documented in many regions of the globe. however, works documenting the advantage of this kind of soil management system on soil quality in the cearense semi-arid region are very scarce. the aim of this work was to evaluate the impact of agroforestry and conventional systems on the physical and chemical soil characteristics, after five years of experimentation in the semi-arid region, ceará, brazil. the experiment consisted of seven treatments: agrosilvopasture (agp), silvopasture (silv), traditionally cultivated in 1998 and 1999 (tr98), traditionally cultivated in 2002 (tr02), intensive cropping (ci), and two native forests (mn-1 and mn-2). soil samples were collected at four depths: 0-6, 6-12, 12-20 and 20-40cm. soil quality was evaluated by the following physical and chemical characteristics analyzed: granulometry, clay dispersion, aggregate stability, exchangeable elements, soil ph and total organic carbon (cot). the treatments agp, tr98 and ci reduced the cot content due to intensive soil management. chemical characteristics, such as exchangeable cations, cec, and ph varied as a function of clay content in silv and mn-2, whereas in ci and tr98, there was reduction in these characteristics due to the intensive soil management. the agp treatment seems to improve the nutrient cycle, however, the intensive soil management, and the consequent reduction in cot content also originated reduction in aggregate stability. results allowed to recommend the silv treatment in order to maintain soil quality and food production in the cearense semi-arid region.
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