162,047 research outputs found
Marchenko inversion in one dimension
No full textOrientadores: Maria Amélia Novais Schleicher, Joerg Dietrich Wilhelm SchleicherDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica e Instituto de GeociênciasResumo: A função de Green focada em um ponto arbitrário pode ser obtida por meio da solução da equação integral de Marchenko ou das equações acopladas de Marchenko, utlizando-se métodos iterativos. A equação integral de Marchenko é uma equação integral unidimensional que relaciona a amplitude de espalhamento e o coeficiente de reflexão que deu origem ao campo espalhado, sendo assim, um problema de espalhamento inverso. As equações acopladas de Marchenko são oriundas da relação entre o dado s??smico (função de Green) e uma solução fundamental de um problema de propagação (equação de Helmholtz homogênea com perturbação na velocidade). Este trabalho de dissertação visa reunir as deduções teóricas da equação integral de Marchenko e das equações acopladas de Marchenko, bem como apresentar o resultado da implementação dos dois esquemas iterativos e a comparação entre eles. Além disso, propõe uma aplicação para detecção de camadas utilizando as funções de Green unidirecionais redatumadasAbstract: The Green¿s function focused at an arbitrary point can be obtained from the solution of the Marchenko integral equation or the coupled Marchenko equations, by means of iterative schemes. The Marchenko integral equation is an unidimensional integral equation that relates the scattering amplitude and the reflection coefficient that created the scattered field. Therefore this equation represents an inverse scattering problem. The coupled Marchenko equations are a result from the relationship between the seismic data (Green¿s function) and the fundamental solution of a propagation problem (homogeneous Helmholtz equation with velocity perturbation). In this master thesis, we unite and compare the theoretical derivations of the Marchenko integral equations and the coupled Marchenko equations and present the implementational results of two iterative schemes for solving them and their comparison. Moreover, we present an application of the scheme for the coupled equations for layer detection using the one-way redatumed Green¿s functionMestradoReservatórios e GestãoMestra em Ciências e Engenharia de Petróle
Condición de imagen aplicada a migración por el método de Marchenko
No full textLa condición de imagen por el método de Marchenko, es una nueva técnica para la obtención de imágenes sísmicas claras en zonas geológicas estructuralmente complejas, contribuyendo a atenuar reflexiones múltiples a una profundidad especifica dentro del subsuelo. Este método estima la función de Green utilizando la respuesta por reflexión del medio en superficie y un modelo de velocidad suavizado. Por medio del teorema de reciprocidad la función de Green puede interpretarse como la respuesta de las fuentes colocadas en superficie, observadas por un receptor virtual localizado en el subsuelo. Adicionalmente, la aplicación de la ecuación de Marchenko iterativamente, permiten estimar la función de Green ascendente y descendente, como una fuente virtual en el punto de enfoque y se interpreta como un proceso de relocalización. Posteriormente, la función de Green estimada se utiliza en la condición de imagen por el método de deconvolución multidimensional para adquirir una imagen 2D o 3D de la zona de interés. Ademas, los artefactos de imagen se atenúan implícitamente en el paso de formación de la imagen. El presente trabajo aplica la metodología de condición de imagen por el método de Marchenko en datos sintéticos para un modelo simple de capas horizontales y datos reales de un modelo de velocidad del Valle Superior del Magdalena, logrando la atenuación de múltiples en la imagen sísmica relocalizada a una profundidad constante del subsuelo, en comparación con algoritmos de migración que representan incorrectamente las reflexiones múltiples y pueden inducir a error a los intérpretes la localización de prospectos potenciales de hidrocarburos.Abstract: The Imaging condition by the Marchenko method is a new technique to obtain clear seismic images in structurally complex geological zones, attenuating multiple reflections at a specific subsurface depth. This method estimates the Green’s Function using the reflection response on the surface, and a smoothed velocity model. Through the reciprocity theorem, the Green’s function can be interpreted as the response of the sources placed on the surface, observed by a virtual receiver located in the subsurface. Also, the application Marchenko’s equation interactive, allow the estimation of the Green’s function on its upgoing and downgoing components as a virtual source at the focusing point and can be interpreted as a redatuming process. Afterwards, these wave fields are used in the imaging condition by the multidimensional deconvolution method to acquire a 2D or 3D image of the area interest with attenuated artifacts that are implicitly subtracted at the image-forming step. This work applies the imaging condition methodology by the Marchenko method to synthetic data for a simple model of horizontal layers, and to real data of a velocity model of the upper Magdalena valley, achieving the attenuation of multiples or artifacts in the seismic image redatumed to a constant depth of the subsurface, compared to migration algorithms that incorrectly represent multiple reflections and may mislead interpreters in locating potential hydrocarbon prospects.Maestrí
Variations on the Author
No full text“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Rate of convergence in probability to the Marchenko-Pastur law
No full textGötze F, Tikhomirov A. Rate of convergence in probability to the Marchenko-Pastur law. BERNOULLI. 2004;10(3):503-548.It is shown that the Kolmogorov distance between the spectral distribution function of a random covariance (1/p)XXT, where X is an nxp matrix with independent entries and the distribution function of the Marchenko-Pastur law is of order O(n(-1/2)) in probability. The bound is explicit and requires that the twelfth moment of the entries of the matrix is uniformly bounded and that p/n is separated from 1
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Marchenko-Pastur law with relaxed independence conditions
No full textWe prove the Marchenko-Pastur law for the eigenvalues of sample
covariance matrices in two new situations where the data does not have
independent coordinates. In the first scenario - the block-independent model -
the coordinates of the data are partitioned into blocks in such a way that
the entries in different blocks are independent, but the entries from the same
block may be dependent. In the second scenario - the random tensor model - the
data is the homogeneous random tensor of order , i.e. the coordinates of the
data are all different products of variables chosen from a
set of independent random variables. We show that Marchenko-Pastur law
holds for the block-independent model as long as the size of the largest block
is and for the random tensor model as long as . Our main
technical tools are new concentration inequalities for quadratic forms in
random variables with block-independent coordinates, and for random tensors
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Orthadenella coulsoni Gwiazdowicz & Marchenko & Teodorowicz 2014, sp. nov.
No full textOrthadenella coulsoni sp. nov. (Figures 1, 2, 3A–G, 4A–D, 5, 6A–D) Type material Holotype. Female, North Altai (51° 30 ′ N, 85° 02 ′ E), 700 m asl, Shebalino District, Larix sibirica forest, on the hillside, in litter, 17 August 2011, coll. I.I. Marchenko. Paratypes. Two females, the same data as holotype; 11 females, North Altai (51° 08 ′ N, 85° 34 ′ E), 1200 m asl., Shebalino District, environs of Topuchaja village, swamped forest of Picea sibirica, in litter, 10 June 1999, coll. I.I. Marchenko; five females and eight males, Central Altai (50° 12 ′ N, 88° 03 ′ E), Kurai Ridge foothills, 2000 m asl., floodplain river Kuraika, shrub, in litter, 16 July 1964, coll. S.K. Stebaeva. Diagnosis Female (n = 19). Idiosoma oval, 400–420 µm in length and 225–240 µm in width. Dorsal. Holodorsal shield bearing 43 pairs of simple setae and among them 20 are situated on the opisthonotal posterior part. The shortest setae are given (in µm): j2 (7–8), j3 (10–11), z1 (5–7), z2 (10–12), s1 (6–7), J5 (7–10); the longest are those labelled j1 (20–22), Z5 (38–41), Z4 (25–26), S4 (25–27) and S5 (25–27). Other seta in j, z and s rows, on the podonotal part, are of a median length from 12 to 17 µm and are as follows: j4 (13–15), j5 (15–17), j6 (15–17), z3 (12–15), z4 (12–15), z5 (12–15), z6 (12–15), s2 (10–12), s3 (12–15), s4 (12–15), s5 (12–15), s6 (12–15), and slightly longer in J, Z and S rows, on the opisthonotal part, from 15 to 22 µm, consecutively: J1 (15–17), J2 (15–17), J3 (15–17), J4 (20–22), Z1 (15–17), Z2 (15–17), Z3 (15–17), S1 (17–22), S2 (17–22), S3 (17–22). All setae in the marginal row r–R are located on the shield, none on the soft membrane. They range in length in a row r from 15 to 17 µm, r2 (15–17), r4 (15–17), r5 (15–17), r6 (15–17), excepting humeral setae r3 = 21 µm, and in row R are about 17 to 20 µm as given: R1 (17–20), R2 (17–20), R3 (17–20), R4 (17–20), R (17–20). Setae r2–R5 at clearly delineated marginal strip. Holodorsal shield is more or less conspicuously covered with a reticulate ornamentation (Figure 1). Ventral. The tritosternum with base 10–11 µm wide and 14–15 µm long with laciniae 57–62 µm long (excluding base) with a fused area, free area for about 0.7 of total length (Figure 3A). Anteriorly to the sternal shield lie two pairs of small presternal platelets. Outer platelets are smaller (5–7 × 3 µm) than the inner ones (11–15 × 5 µm). Sternal shield reaches 90–92 μm in length at the midline, and 120–130 μm in width at the widest point, that is, at a level between the first and the second coxae. It bears three pairs of simple setae totally, of lengths: st1 (23–25 µm), st2 = st3 (17–20 µm). As well as pair of gland pores gst1 at the extensions between coxae I–II and two pairs of lyrifissures iv1, iv2, but the third pair of sternal lyrifissures iv3 is absent either on the sternal shield nor metasternal shields. Posteriorly to the sternal shield are small rounded metasternal shields (10 × 10 µm), with a setae st4 (19–20 µm) on it. Inner to coxae II–IV are archwise endopodal shields embracing the coxae, underlying an epigynal shield and partially fused to it. Epigynal shield broad (82–88 µm), and almost of the same length (c. 90 µm at the midline), truncate, with a pair of setae st5 (15–20 µm). Paragenital poroids iv5 are located outside the epigynal shield. Four scanty sclerites arranged in a one line are located posterior to an epigynal shield. Heart-shaped ventrianal shield 145–150 µm length and 155–165 µm width with 15 setae. The shortest are the para-anal setae (13–15 µm), noticeably longer is the postanal seta (24–25 µm) and ventral setae ranging from 18 µm to 21 µm as given (in µm): JV1 (18–21), JV2 (18–21), JV3 (18–21), JV4 (18–21), ZV2 (18–21) except shorter ZV3 (15–17). Likewise, the sternal, genital and ventrianal shields are covered with a reticulate ornamentation (Figure 2). Outside the ventrianal shield remain four pairs of simple setae (including UR3 = 17–20 µm) JV5 (28–30), ZV4 (16–20), ZV5 (20–21). Peritremes long, reaching above the coxae I, stigmatas at the level of coxae IV. Peritrematal shields narrow, connected with an exopodal strip alongside coxae IV. Peritrematal–exopodal shields fused, with poroids ip1, ip2, ip3 and pores gp2, gp3, gv 2. Posterolaterally to the coxae IV on each side arise two pairs of metapodal sclerites. Those proximal to the coxae IV are smaller (4–6 × 4–6 µm), than further ones (20–21 × 11–13 µm). Sperm access system is that of a Laelapid type, with a sacculus comprised of a thick and porous layer with a numerous thin filaments (Figure 3C). Gnathosoma. Corniculi are elongated, 26–30 μm long and 10 µm wide; seven rows of denticles are located in the hypostomatal groove (2–6 denticles per row); hypostomatal setae are simple of variable length: h1 –20–21 μm, h2 –21–22 μm, h3 –14–16 μm, h4 – 22–24 μm (Figure 3B). Internal malae as long as corniculi, with a fringed laterobasal margins. Epistome with anterior margin irregularly convex, finely denticulate (Figure 3D). Cheliceral fixed digit 38–40 µm long with a stout pilus dentilis; masticatory surface with a row of 12 teeth and two subapical teeth in addition to apical tooth. Cheliceral movable digit (37–39) tridentate in addition to apical hook; with a transverse-diagonal groove, which appears on the basal one-third of ventral side of chelicera. Dorsal cheliceral seta, dorsal and lateral (antiaxial) lyrifissure distinct (Figure 3E). Palps 126–128 μm long (Figure 3F, G). Legs. Variable in length: I – 320–340 μm, II – 250–260 μm, III – 240–250 μm, IV – 315–325 μm. Chaetotaxy of legs is peculiar for genus Orthadenella: leg I: coxa, trochanter, femur, genu, tibia (2, 6, 12, 13, 13), leg II (2, 5, 11, 11, 10), leg III (2, 5, 7, 9, 8), leg IV (1, 4, 6, 9, 9) (Figure 4A, B, C, D). Male (n = 8) Idiosoma oval, 330–355 µm in length and 212–222 µm in width. Dorsal. Holodorsal shield bearing 43 pairs of simple setae, including 23 podonotal pairs (j1-j6, z1-z6, s1-s6, r2-r6) and 20 opisthonotal pairs (J1-J5, Z1-Z5, S1-S5, R1- R5). Dorsal shield lightly reticulate. Measurements of podonotal setae precisely (in µm): j1 (12–15), j2 (15–17), j3 (12–15), j4 (12–15), j5 (12–15), j6 (12–15), z1 (8–10), z2 (15–17), z3 (12–15), z4 (12–15), z5 (12–15), z6 (12–15), s1 (12–15), s2 (15–17), s3 (12– 15), s4 (15–17), s5 (12–15), s6 (12–15), r2-r6 (12–15). Measurements of opisthonotal setae as follows (in µm): J1 (10–12), J2 (10–12), J3 (12–15), J4 (15–17), J5 (5–6), Z1 (12–15), Z2 (12–15), Z3 (12–15), Z4 (17–20), Z5 (28–30), S1 (12–15), S2 (12–15), S3 (12–15), S4 (15–17), S5 (17–20), R1-R5 (12–15). Setae r2–R5 at clearly delineated marginal strip, likewise for female. Ventral. Tritosternum with base 7–10 µm wide and 12–15 µm long with laciniae 42– 47 µm long (excluding base) with a fused area, free area for about 0.7 of total length (Figure 6A). Presternal area with a pair platelets. Peritrematal shields and peritremes as in female (poroids ip1, ip2, ip3 and pores gp2, gp3, gv 2 are present). Sternitigenital shield 137–145 µm long and 100–113 µm wide at level between coxae II–III; finely ornamented anteriorly between setae st1 and st3, posteriorly between st4 and st5, and lineate along lateral margins. Sternal shield with a pair of gland pores gst1 at extensions between coxae I–II and with two pairs of lyrifissures iv1, iv2. Shields with five pairs of setae. Measurements of sternal setae as given (in µm): st1 (20–21), st2 (18–20), st3 (16–18), st4 (15–16), st5 (14–15). Ventrianal shield ornamented, midlength (130–145 µm), greatest at midlateral width (155–170 µm) at the level of seta JV1, with a regularly convex lateral margins, bearing five opisthogastric setae JV1 (14–15), JV2 (15–17), JV3 (14–15), JV4 (14–15 µm), ZV2 (14–15), pair of circumanal setae (14–15) and post-anal seta 20 µm; bearing two pairs of poroids and pair of pores gv3; soft opisthogastric cuticle stays with three pairs of setae JV5 (20), ZV4 (13–14), ZV5 (14–15). Opisthogastric setae ZV3 and UR3 are absent contrary to female (Figure 5). Gnathosoma. Deutosternum with seven rows of denticles; margins of deutosternal groove delineated laterally except posteriormost row. Number of denticles in each row varies individually in specimens: the first posteriormost row (5–9 denticles), the second row (8–12), the third row (5–6), the fourth row (4–5), 5–7 rows (2–4 in each row). Subcapitulum with a hypostomatic setae h1 (20–22), h2 (15–17), h3 (20–22), h4 (20–22); with three pockmarked delineated areas between h2-h3 and palpcoxal seta h4. Form of corniculi as in female, 22 µm long and 7–8 µm width; internal malae longer than corniculi, with fringed lateral margins basally (Figure 6B). Cheliceral fixed digit 30–32 µm long with a stout pilus dentilis and usually with six teeth in addition to apical tooth: two large basal teeth and two smaller medium-sized teeth at a masticatory surface and two subapical teeth. Cheliceral fixed digit of one sample (eighth examined sample) with nine teeth: three large basal teeth, four medium-sized teeth at masticatory surface and two subapical teeth in addition to apical tooth. Movable digit (28–30 µm) with one tooth in addition to an apical tooth. Spermatodactyl 43–45 µm long with a hyaline ridge above internal canal along its entire length (Figure 6C). Dorsal cheliceral seta, dorsal and lateral (antiaxial) lyrifissure distinct. Epistome with an anterior margin irregularly convex, finely denticulate (Figure 6D). Legs. Variable in length: I – 260–290 µm, II – 215–225 µm, III – 200–210 µm, IV – 260–290 µm. Leg structure and setation as in female. Etymology The species is dedicated to our friend, a scientist exploring the invertebrate fauna of the High Arctic, Prof. Dr Stephen J. Coulson from University Centre in Svalbard. Longyearbyen, Norway. Differential diagnosis The morphometric analysis of O. coulsoni shows many different diagnostic characters from the other two species of Orthadenella. Even a simple analysis of setae measurements gives both similarities (the same lengths of setae Z4, Z5, and setae J1, J2, J3, J4, Z1, Z2 longer by 6–7 μm, and vertical j1 shorter by 4 μm) and dissimilarities when compared to O. tennesseensis. A shared character between O. coulsoni and O. lawrencei is a marked dorsal reticulated patterning covering almost the whole shield, while in O. tennesseensis, this is reticulated only on the posterior and anterior border. Moreover, O. coulsoni and O. lawrencei have a humeral seta r3 conspicuously longer than the remaining setae in the marginal row r–R, which O. tennesseensis does not. This character is repeated in the S4, S5 and Z5 pairs of setae. However, O. lawrencei setae Z4 are identical to the Z1–Z3 setae, whereas in O. coulsoni these setae are dissimilar. In addition, the location of pore iv5 is a further diagnostic character. This pore lies outside the genital shield of both O. coulsoni and O. tenessensis but, as is more common, on the shield in O. lawrencei. A very fine character separating the species is the appearance of a ventrianal shield. This has a characteristic concave anterior boarder at the level between the genital and metapodal sclerites for the entire genus, but differs in shape among species. That of O. coulsoni is wider than long, contrary to the other species. Likewise, the difference in the number of setae located on the ventrianal shield, excluding a circum-anal setae, is another significant character, differentiating O. tennesseensis, with five pairs, from the two remaining species, each bearing six pairs. The metapodal shields in the opistogastric region clearly distinguish O. lawrencei which possesses only a single pair, while O. coulsoni has two pairs composed of the larger sclerite with a smaller abutting. The epistome of O. tennesseensis and O. lawrencei is a trispinate, median process broadly triangular and extending beyond the apex of the lateral processes, contrary to O. coulsoni, which has convex epistome with homogenous denticles arranged parallel to each other. The spermatheca of O. lawrencei is composed of a sacculus permeated with numerous pores and cylinders, while the spermatheca of O. coulsoni is permeated with numerous pores and thin filaments. Key to the females of genus Orthadenella Information concerning O. lawrencei and O. tennesseensis was obtained from published descriptions and illustrations (Evans 1958; De Leon 1963; McGraw and Farrier 1969; Moraza and Lindquist 2011). 1. Only one metapodal plate on each side of the body behind coxae IV........................................................................................................ O. lawrencei (Evans 1958) – Metapodal plates divided into two small plates................................................. 2 2. Interscutal setae JV4 outside ventrianal shield, length and width of ventrianal shield similar...................................................... O. tennesseensis (De Leon 1963) – Interscutal setae JV4 on ventrianal shield, ventrianal shield wider than long........................................................................................................... O. coulsoni n. sp. Funding This study and field work of one of us (I.I. Marchenko) was supported by The Federal Fundamental Scientific Research Programme for 2013–2020 [VI.51.1.7. 30.4].Published as part of Gwiazdowicz, Dariusz J., Marchenko, Irina I. & Teodorowicz, Ewa, 2014, Description of Orthadenella coulsoni sp. nov. (Acari: Mesostigmata: Melicharidae) from Siberia with a key to the females of Orthadenella, pp. 1659-1671 in Journal of Natural History 49 (27) on pages 1661-1670, DOI: 10.1080/00222933.2014.974706, http://zenodo.org/record/400637
Larry O. Spencer, Conference Author Presentation
No full textGen. Larry O. Spencer, USAF (Ret.), author of Dark Horse: A Journey from the Horseshoe to the Pentago
On Local Borg–Marchenko Uniqueness Results
No full textWe provide a new short proof of the following fact, first proved by one of us in 1998: If two Weyl–Titchmarsh m-functions, m_j(z), of two Schrödinger operators, H_j = -d^2/dx^2 + q_j, j = 1,2 in L^2((O,R)), O < R ≤ ∞, are exponentially close, that is, |m_1(z) - m_2(z)|_|z|→∞ = O(e^(-2 IM(z^1/2)a), O < ɑ <R, then q_1 = q_2 a.e. on [O,ɑ]. The result applies to any boundary conditions at x = O and x = R and should be considered a local version of the celebrated Borg–Marchenko uniqueness result (which is quickly recovered as a corollary to our proof). Moreover, we extend the local uniqueness result to matrix-valued Schrödinger operators
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Relaxing Independence in the Marchenko-Pastur Law for Random Matrices and the Application to Approximate Embeddings
No full textThis dissertation adds to the collection of works studying the Marchenko-Pastur law in two ways. First it considers two new models of random column vectors that have weaker independence hypotheses than the well-known i.i.d. hypothesis and shows that random matrices, formed by concatenating random column vectors of a model, still follow the Marchenko-Pastur law. The two models of random column vectors are block columns and vectorized tensor columns. The block column vectors will be made up of n blocks each of length d, with d=o(n). If the entries are mean zero, variance one, have uniformly bounded fourth moments, entries within a block are uncorrelated, and entries in different blocks are independent, then the Marchenko-Pastur theorem holds as n tends to infinity. Furthermore, if additionally an exchangeability criteria is satisfied, then the theorem holds without requiring d=o(n). The vectorized tensor columns will be made up of a vectorized t-tensor of an i.i.d. vector of length n which has entries that are mean zero, variance one, uniformly bounded fourth moments, and t^3=o(n), and again the Marchenko-Pastur theorem holds as n tends to infinity. The second contribution of this dissertation is in studying a particular type of an approximate embedding of vectors. For any collection of vectors, a general lower bound for the least dimension required for an approximate embedding is given. For vectors which are column vectors of a matrix that follows the Marchenko-Pastur law, an asymptotic formula for the exact value of the least dimension required is given. Numerical results show this asymptotic formula holds quite well, even for relatively small dimensions. Because this works so well for small dimensions, this gives an easy numerical test that provides evidence for answering the question, "Does a specific covariance structure have a limiting spectral distribution or not?" We consider a particular covariance structure which relates to the number of terms needed in the Karhunen-Loeve expansion to approximate a random field within a specified tolerance
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