759 resultados para Cantor Manifold
Resumo:
Given a compact Riemannian manifold $M$ of dimension $m \geq 2$, we study the space of functions of $L^2(M)$generated by eigenfunctions ofeigenvalues less than $L \geq 1$ associated to the Laplace-Beltrami operator on $M$. On these spaces we give a characterization of the Carleson measures and the Logvinenko-Sereda sets.
Resumo:
When dealing with multi-angular image sequences, problems of reflectance changes due either to illumination and acquisition geometry, or to interactions with the atmosphere, naturally arise. These phenomena interplay with the scene and lead to a modification of the measured radiance: for example, according to the angle of acquisition, tall objects may be seen from top or from the side and different light scatterings may affect the surfaces. This results in shifts in the acquired radiance, that make the problem of multi-angular classification harder and might lead to catastrophic results, since surfaces with the same reflectance return significantly different signals. In this paper, rather than performing atmospheric or bi-directional reflection distribution function (BRDF) correction, a non-linear manifold learning approach is used to align data structures. This method maximizes the similarity between the different acquisitions by deforming their manifold, thus enhancing the transferability of classification models among the images of the sequence.
Resumo:
In this paper, we present an efficient numerical scheme for the recently introduced geodesic active fields (GAF) framework for geometric image registration. This framework considers the registration task as a weighted minimal surface problem. Hence, the data-term and the regularization-term are combined through multiplication in a single, parametrization invariant and geometric cost functional. The multiplicative coupling provides an intrinsic, spatially varying and data-dependent tuning of the regularization strength, and the parametrization invariance allows working with images of nonflat geometry, generally defined on any smoothly parametrizable manifold. The resulting energy-minimizing flow, however, has poor numerical properties. Here, we provide an efficient numerical scheme that uses a splitting approach; data and regularity terms are optimized over two distinct deformation fields that are constrained to be equal via an augmented Lagrangian approach. Our approach is more flexible than standard Gaussian regularization, since one can interpolate freely between isotropic Gaussian and anisotropic TV-like smoothing. In this paper, we compare the geodesic active fields method with the popular Demons method and three more recent state-of-the-art algorithms: NL-optical flow, MRF image registration, and landmark-enhanced large displacement optical flow. Thus, we can show the advantages of the proposed FastGAF method. It compares favorably against Demons, both in terms of registration speed and quality. Over the range of example applications, it also consistently produces results not far from more dedicated state-of-the-art methods, illustrating the flexibility of the proposed framework.
Resumo:
In this paper we will find a continuous of periodic orbits passing near infinity for a class of polynomial vector fields in R3. We consider polynomial vector fields that are invariant under a symmetry with respect to a plane and that possess a “generalized heteroclinic loop” formed by two singular points e+ and e− at infinity and their invariant manifolds � and . � is an invariant manifold of dimension 1 formed by an orbit going from e− to e+, � is contained in R3 and is transversal to . is an invariant manifold of dimension 2 at infinity. In fact, is the 2–dimensional sphere at infinity in the Poincar´e compactification minus the singular points e+ and e−. The main tool for proving the existence of such periodic orbits is the construction of a Poincar´e map along the generalized heteroclinic loop together with the symmetry with respect to .
Resumo:
Man’s never-ending search for better materials and construction methods and for techniques of analysis and design has overcome most of the early difficulties of bridge building. Scour of the stream bed, however, has remained a major cause of bridge failures ever since man learned to place piers and abutments in the stream in order to cross wide rivers. Considering the overall complexity of field conditions, it is not surprising that no generally accepted principles (not even rules of thumb) for the prediction of scour around bridge piers and abutments have evolved from field experience alone. The flow of individual streams exhibits a manifold variation, and great disparity exists among different rivers. The alignment, cross section, discharge, and slope of a stream must all be correlated with the scour phenomenon, and this in turn must be correlated with the characteristics of the bed material ranging from clays and fine silts to gravels and boulders. Finally, the effect of the shape of the obstruction itself-the pier or abutment-must be assessed. Since several of these factors are likely to vary with time to some degree, and since the scour phenomenon as well is inherently unsteady, sorting out the influence of each of the various factors is virtually impossible from field evidence alone. The experimental approach was chosen as the investigative method for this study, but with due recognition of the importance of field measurements and with the realization that the results must be interpreted so as to be compatible with the present-day theories of fluid mechanics and sediment transportation. This approach was chosen because, on the one hand, the factors affecting the scour phenomenon can be controlled in the laboratory to an extent that is not possible in the field, and, on the other hand, the model technique can be used to circumvent the present inadequate understanding of the phenomenon of the movement of sediment by flowing water. In order to obtain optimum results from the laboratory study, the program was arranged at the outset to include a related set of variables in each of several phases into which the whole problem was divided. The phases thus selected were : 1. Geometry of piers and abutments, 2. Hydraulics of the stream, 3. Characteristics of the sediment, 4. Geometry of channel shape and alignment.
Resumo:
Learning is predicted to affect manifold ecological and evolutionary processes, but the extent to which animals rely on learning in nature remains poorly known, especially for short-lived non-social invertebrates. This is in particular the case for Drosophila, a favourite laboratory system to study molecular mechanisms of learning. Here we tested whether Drosophila melanogaster use learned information to choose food while free-flying in a large greenhouse emulating the natural environment. In a series of experiments flies were first given an opportunity to learn which of two food odours was associated with good versus unpalatable taste; subsequently, their preference for the two odours was assessed with olfactory traps set up in the greenhouse. Flies that had experienced palatable apple-flavoured food and unpalatable orange-flavoured food were more likely to be attracted to the odour of apple than flies with the opposite experience. This was true both when the flies first learned in the laboratory and were then released and recaptured in the greenhouse, and when the learning occurred under free-flying conditions in the greenhouse. Furthermore, flies retained the memory of their experience while exploring the greenhouse overnight in the absence of focal odours, pointing to the involvement of consolidated memory. These results support the notion that even small, short lived insects which are not central-place foragers make use of learned cues in their natural environments.
Resumo:
Työn kirjallisuusosassa esitellään paperi- ja kartonkikoneiden kiertovoitelujärjestelmien rakennetta ja voitelussa käytettyjen öljyjen ominaisuuksia. Lisäksi on selvitetty voiteluöljyn kunnossapidon kannalta keskeisten epäpuhtauksien kuten veden, hiukkasten ja ilmakuplien analysointia. Suurissa voitelujärjestelmissä öljyn suuri ilmapitoisuus on usein ongelma, mihin ei ole ollut selkeää ratkaisua. Työn tavoitteena oli tutkia ilmakuplien poistamista voiteluöljystä alipainekäsittelyn avulla. Alipaineen vaikusta eri öljyille ja lämpötiloilla tutkittiin laboratoriossa standarditestillä ja määritettiin sopiva alipaine tehdaskokeisiin. Testeissä havaittiin odotutetusti viskositeetin eli käytännössä lämpötilan olevan ratkaiseva tekijä ilman poistumisnopeuteen. Tehdasmittakaavan kokeissa mitattiin rakenteeltaan yksinkertaisen ja vähän energiaa kuluttavan ilmanpoistolaitteen toimintaa. Laitteisto sijoitetaan paluuöljyputkistoon ja sen ei tarvitse olla kiertovoitelukeskuksen yhteydessä. Täysimittainen laitteisto rakennettiin kartonkikoneen ja paperikoneen kiertovoitelujärjestelmiin. Laitteen avulla voidaan käsitellä koko voitelujärjestelmän öljy. Tuloksien mukaan laite toimii odotetulla tavalla ja vähentää merkittävästi ilmapitoisuutta. Järjestelmä on heikoimmillaan tilanteessa, jossa lämpötilat on pidettävä alhaisina ja ilmakuplia on runsaasti.
Resumo:
Let $S_*$ and $S_*^\{infty}$ be the functors of continuous and differentiable singular chains on the category of differentiable manifolds. We prove that the natural transformation $i: S_*^\infty \rightarrow S_*$, which induces homology equivalences over each manifold, is not a natural homotopy equivalence.
Resumo:
Suihku/viira-nopeussuhde on perälaatikon huulisuihkun ja viiran välinen nopeusero. Se vaikuttaa suuresti paperin ja kartongin loppuominaisuuksiin, kuten formaatioon sekä kuituorientaatioon ja näin ollen paperin lujuusominaisuuksiin. Tämän johdosta on erityisen tärkeää tietää todellinen suihku/viira-nopeussuhde paperin- ja kartonginvalmistuksessa. Perinteinen suihku/viira-nopeussuhteen määritysmenetelmä perustuu perälaatikon kokonaispaineeseen. Tällä menetelmällä kuitenkin todellinen huulisuihkun nopeus saattaa usein jäädä tietämättä johtuen mahdollisesta virheellisestä painemittarin kalibroinnista sekä laskuyhtälön epätarkkuuksista. Tämän johdosta on kehitetty useita reaaliaikaisia huulisuihkun mittausmenetelmiä. Perälaatikon parametrien optimaaliset asetukset ovat mahdollista määrittää ja ylläpitää huulisuihkun nopeuden “on-line” määrityksellä. Perälaatikon parametrejä ovat mm. huulisuihku, huuliaukon korkeusprofiili, reunavirtaukset ja syöttövirtauksen tasaisuus. Huulisuihkun nopeuden on-line mittauksella paljastuu myös muita perälaatikon ongelmakohtia, kuten mekaaniset viat, joita on perinteisesti tutkittu aikaa vievillä paperin ja kartongin lopputuoteanalyyseillä.
Resumo:
Several questions about the story of Gen 2-3 remain unresolved in current scholarship. For instance, the implications and manifold consequences of the transgression act - the consumption of the forbidden fruit - are much debated. Interpreters generally agree that the story is connected to several "J" / "non-P" narratives of the primeval history. Besides the use of the tetragrammaton as the designation for God, a common characteristic of these stories is the strong opposition between Yhwh as a harsh deity on one hand and disobedient and transgressing humankind on the other. This paper reconsiders several open questions as well as the aforementioned consensus. The analysis of important motifs in Gen 2-3 leads to the conclusion that this story differs in theologically important ways from the postulated "J"-narrative in Genesis. This indicates that it was not composed as an integral part of that narrative. There are, in Gen 2-3, ideological features and linguistic elements typical of the "J" stratum, but they are all found in the sections that present Yhwh God's investigation and punishment of the couple (3,8-19.24). Since these verses are in tension with or even contradict their immediate context, it should be assigned to a redactional ("J") layer. According to this analysis, the transgression in Gen 2-3 should not be considered a sin. Rather, it is an important step in human evolution towards a self-conscious and autonomous being. The plot has a structure similar to some episodes in ancient Near Eastern myths. 'Initiation' functions as a central theme. Finally, the article discusses the literary milieu of the story. Because of several linguistic and thematic similarities with Gen 1, with P-texts in general, and with the book of Ezekiel, the relationship of Gen 2-3 to these literary entities needs to be reconsidered.
Resumo:
A simple laboratory technique is described for the synthesis of cyclopentadienylthallium and methylcyclopentadienylthallium and their use in the preparation of air sensitive metallocenes in solution. It does not use manifold, drybox or any other special glassware and was applied to the synthesis of cobaltocene, nickelocene and their methyl substituted analogs.
Resumo:
Didactic experiments are proposed in order to demonstrate the characteristics of flow injection analysis and to extend the applications of FIA to the determination of physical chemistry parameters in undergraduate labs. All experiments can be performed with the same flow manifold by employing usual FIA devices. Analytical characteristics are presented by means of the determination of iron in river water, employing 1,10-phenantroline as chromogenic reagent. Physical chemistry applications were the determination of reaction stoichiometries by continuous variation and mole-ratio methods and the evaluation of the pH and ionic strength effects on the kinetic of the reduction of hexacianoferrate(III) by ascorbic acid.
Resumo:
A spectrophotometric flow injection analysis (FIA) procedure employing natural urease enzyme source for the determination of urea in animal blood plasma was developed. Among leguminous plants used in the Brazilian agriculture, the Cajanus cajan specie was selected as urease source considering its efficiency and availability. A minicolumn was filled with leguminous fragments and coupled to the FIA manifold, where urea was on-line converted to ammonium ions and subsequently it was quantified by spectrophotometry. The system was employed to determine urea in animal plasma samples without any prior treatment. Accuracy was assessed by comparison results with those obtained employing the official procedure and no significant difference at 90 % confidence level was observed. Other profitable features such as an analytical throughput of 30 determinations per hour, a reagent consumption of 19.2 mg sodium salicylate, 0.5 mg sodium hipochloride and a relative standard deviation of 1.4 % (n= 12) were also obtained.
Resumo:
This paper presents an automatic procedure employing a reagent in the form of a slurry in a flow-injection system. The feasibility of the proposal is demonstrated by sulphate determination in water using the Barium Chloranilate method, which is based on the precipitation of barium sulphate. The release of a stoichiometric amount of highly colored chloranilic ions is monitored at 528 nm. The reaction is carried out in alcoholic medium in order to reduce the solubility of the reagent. A considerable improvement in the sensitivity is attained by adding ferric ions to the released chloranilic ions. An on-line filtration step to separate the excess reagent from the released chloranilic ions was necessary. In addition, a column containing a cation exchange resin was included in the manifold to remove potentially interfering ions. The proposed procedure is suitable for 30 determinations per hour and the relative standard deviation is less than 2%. The analytical curve is linear between 0.0 and 40 mg L-1 and the determination limit is about 2.0 mg L-1SO4(2-). Accuracy was confirmed by running several samples already analysed by a standard turbidimetric procedure.
Resumo:
An automatic flow injection procedure for spectrophotometric aluminium determination in purified water and solutions containing high salts concentrations used for hemodyalisis treatment was developed. The method was base on reaction of Al3+ with cianine eriochrome R (ECR) after preconcentration using the AG50W-X8 cationic-exchange resin. Elution was carried out using a 1 % (m/v) calcium chloride solution. The manifold comprised an automatic proporcional injector controlled by a computer equipped with an eletronic interface and software written in QuicBASIC 4.5 with facilities to control the injector and perform data acquisition. Samples with concentration ranging from 4.96 to 19.90 µg L-1 Al were analyzed and recoveries between 88 and 113% were obtained by using the standard addition method. Other profitable analytical characteristics such as a relative standard deviation 1.3 % (n = 10) for a typical sample 14.5 µg L-1 Al, a linear response ranging up to 60.0 µg L-1Al, and a sampling throughput of 10 determinations per hour were achieved. A detection limit of 4.2 µg L-1 Al was estimated as suggested by IUPAC.