51,692 research outputs found
The role of high vorticity structures in development of Kolmogorov turbulent spectra in inviscid flow
No full textThis work is aimed for understanding nonlinear mechanisms at early stages of turbulence, when the flow is not yet affected by viscosity. Based on numerical simulations of the 3D incompressible Euler equations with generic large-scale initial conditions, we show that the exponential growth of vorticity developing in thin vortex sheets (pancake structures) leads to formation of Kolmogorov energy spectrum in fully inviscid flow. This direct observation yields the decoupling of the finite-time blowup problem from the Kolmogorov theory of turbulence. We demonstrate that the pancake structures have self-similar dynamics and evolve according to the scaling law W(t) ~ l(t)^(-2/3) for the local vorticity maximums W(t) and the transverse pancake scales l(t). Then, we argue that the energy spectrum requires an increasing number of such structures developing densely through the Kolmogorov range of wavenumbers, in good agreement with numerical data
An example for Kuznetsov-Shinder conjecture
No full textWe give an example for the Kuznetsov-Shinder conjecture, with infinitely many
non-isomorphic D-equivalent and L-equivalent varieties.Comment: 5 pages. This work was prepared for talk at 38th Annual Conference of
Ramanujan Mathematical Society, 202
Stability conditions on Kuznetsov components of Gushel–Mukai threefolds and Serre functor
No full textWe show that the stability conditions on the Kuznetsov component of a Gushel- Mukai threefold, constructed by Bayer, Lahoz, Macri and Stellari, are preserved by the Serre functor, up to the action of the universal cover of GL(2)(+) (III). As application, we construct stability conditions on the Kuznetsov component of special Gushel-Mukai fourfolds
Paravillersia Kuznetsov 1978
No full textGenus Paravillersia Kuznetsov, 1978 Type species: Paravillersia grata Kuznetsov, 1978, by original designation. Diagnosis. Prodorsal shield with 3 pairs of setae (vi, ve, sci). Setae sce situated on platelets separated by striae from prodorsal shield. Eyes present. Postocular bodies absent. Hysterosomal shield with 6 pairs of setae (c 1, d 1, d 2, e 1, e 2, and f 1). Lateral margins of hysterosomal shield with distinct incisions anterolaterally to setae e 2. Suranal plate dorsal or ventral, with 2 pairs of setae (h 1, h 2). Two pairs of callosities present between hysterosomal and humeral shields. Genital setae absent. Chelicerae fused medially, not forming stylophore. Number of setae on palpal segments: Tr 0, Fe 3 (d, l’, v”), Ge 2 (d, l”), Ti 3 (d, l’, l”), Ta 8 (1) (fused eupathidia ul’, ul”, sul, eupathidion acm, tactile setae ba, bp, lp, 1 solenidion ω). Subcapitulum with 4 pairs of setae (m, n, or 1, or 2); setae or 1 distinctly thickened. Leg chaetotaxy: I: Tr 1 (v’), Fe 6 (d, l’, l”, v’, v”, bv”), Ge 4 (d, l’, l”, k), Ti 5 (2) (d, l’, l”, v’, v”, φ, φp), T a 13 (1) (p’, p”, tc’, tc”, ft’, ft”, u’, u”, a’, a”, pl’, pl”, vs, ω); II: Tr 1 (v’), Fe 5 (d, l’, l”, v’, bv”), Ge 4 (d, l’, l”, k), Ti 5 (1) (d, l’, l”, v’, v”, φ), Ta 9 (1) (p’, tc’, tc”, u’, u”, a’, a”, pl’, vs, ω); III: Tr 2 (v’, l’), Fe 3 (d, l’, ev’), Ge 1 (d), Ti 5 (1) (d, l’, l”, v’, v”, φ), Ta 7 (1) (tc’, tc”, u’, u”, a’, a”, vs, ω); IV: Tr 1 (v’), Fe 2 (d, ev’), Ge 1 (d), Ti 5 (1) (d, l’, l”, v’, v”, φ), Ta 7 (1) (tc’, tc”, u’, u”, a’, a”, vs, ω). Remarks. The genus Paravillersia is very close to the genus Villersia Oudemans, 1927 by the presence of 3 pairs of setae on the prodorsal shield, lateral incisions on the hysterosomal shield, and by the location of setae sce on the separate platelets. These genera differ from each other by location of setae d 2 on the hysterosomal shield in Paravillersia. It also close to the genus Eustigmaeus Berlese, 1910 but differs by location of setae sce on separate platelets. Species included. The genus currently includes 2 species: P. grata Kuznetsov, 1978, which known from Voronezh Province of Russia, and P. jamaliensis Khaustov sp. nov. from Yamalo-Nenets Autonomous Okrug in Western Siberia.Published as part of Khaustov, Alexander A., 2014, A new species of the genus Paravillersia (Acari: Prostigmata: Stigmaeidae) from Western Siberia, with supplementary description of Paravillersia grata Kuznetsov, 1978 in Zootaxa 3873 (1), DOI: 10.11646/zootaxa.3873.1.5, http://zenodo.org/record/22878
Cubic fourfolds, Kuznetsov components and Chow motives
No full textWe prove that the Chow motives of two smooth cubic fourfolds whose Kuznetsov
components are Fourier-Mukai derived-equivalent are isomorphic as Frobenius
algebra objects. As a corollary, we obtain that there exists a
Galois-equivariant isomorphism between their l-adic cohomology Frobenius
algebras. We also discuss the case where the Kuznetsov component of a smooth
cubic fourfold is Fourier-Mukai derived-equivalent to a K3 surface.Comment: 22 page
The 'Blue Rose' movement and Russian symbolist painting
No full textThe object of this essay is two-fold: firstly, to present an examination of the "Blue Rose" group of artists in the context of Russian Symbolism and secondly, to indicate its importance to the evolution of modern Russian painting. It was felt that while the development of the Russian visual arts of the period 1910-1930 had been studied in some detail, especially by Western scholars over the last few years, the preceding decade was still an obscure and confused field of research: the total absence of any adequate appraisal of the "Blue Rose" movement either in Russia or in the West and my own conviction that this movement warranted particular attention as a vital link between Russian Realism and the so-called avant-garde acted as the prime motives for the completion of this work.
In order to justify this assertion I have attempted to consider the emergence of the "Blue Rose" group as part of an organic, indigenous process and to relate it to the achievements of Russian art of the late 19th century. Since the work of the "Blue Rose" group is unknown to Western observers, certain paintings of leading members -Kuznetsov, Sapunov, Sar'yan, Sudeikin--have been analysed in detail; in the case of less active members - Arapov, Peofilaktov,Utkin – a more cursory examination has been presented; since this essay is concerned with the development of easel painting above all, the output of Bromirsky and Matveev (the two sculptors of the group) has been given only marginal consideration.
Throughout the text the name, "Blue Rose " has been used to denote that group of sixteen artists who exhibited at the single exhibition of that name in March, 1907. Although the name was used for the first time only at that exhibition, I have applied it in this essay to the group and to individual artists throughout their Symbolist period, i.e. c.1904-1908. The text of this work is based largely on material studied in Moscow between 1966; and 1968. Although original "Blue Rose", paintings are very rare, some examples were found both in public and in private collections: in this respect, access to the store-rooms of the Tret'yakov Gallery, Moscow and the Russian Museum, Leningrad facilitated my task. Published material concerning the genesis and development of the "Blue Rose” group amounts to very little and, therefore, I had to rely heavily on private archives and personal reminiscences of contemporaries as well as on more general sources such as the Symbolist journals and memoirs: in this respect, of particular value were the manuscript of Arapov's autobiography, the diaries and documents of P. Kuznetsov, the unpublished guide to the reserves of the Tret'yakov Gallery and the oral collections of the late V. M. Lobanov; W. Nouvel's unpublished monograph on Diaghilev provided me with useful material in my study of the "World of Art”. In addition, relevant written material was found and consulted in the Lenin Library, Moscow, the Tret'yakov Gallery Library, Moscow, the Pushkin Museum of Fine Arts, Moscow, the Central State Archives of Literature and Art, Moscow, the Saltykov-Shchedrin Library, Leningrad, the Russian Museum Library, Leningrad; in the West extensive use was made of the facilities of the British Museum, the Victoria and Albert Museum, the Library of the School of Slavonic and East European Studies at the University of London, the Library, of Congress, the New-York Public Library and the Widener Library, Harvard.
Because of the complete absence of Russian exhibition catalogues of the Symbolist period in the West, and of their rarity in Russia, detailed listings have been made where relevant to the text. In the case of the “Crimson Rose" and "Blue Rose" exhibitions the participators and their contributions are listed in full in Appendices I and III; this is because only one copy of the former is known to exist (in the library of the Leningrad Academy of Fine Arts) and only two copies of the latter have been located. In these instances and in those of the "Golden Fleece" exhibitions the original Russian has been retained in order to avoid that constant confusion which translation and retranslation of picture titles has caused in the West. The illustrations are from pictures in Russian public and private collections and, in some cases, where the original has been lost or has not been traced—from reproductions in contemporaneous books and journals. The system of transliteration is that used by the journal, Soviet Studies (published by the Institute of Soviet and East European Studies, Glasgow), although where a variant has been established already this has been used, e. g. Diaghilev (not Dyagilev), Jawlensky (not Yavlensky)
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
Deep Learning Based Image Steganalysis
No full textVarious cryptographic and steganographic techniques are used to hide digital information during its processing, storage, and transmission. While cryptography hides the information content of digital data (by converting them into a meaningless set of noise-like sequences), steganography hides the very existence of information messages. In other words, steganographic techniques hide digital messages by embedding them in so-called. containers. Containers are other digital data or physical objects. To do this, containers (covers, media) must be highly redundant data. Revealing the fact of steganographic hiding and detecting an embedded message is usually extremely difficult. In fact, hidden messages are some noise added to the container, and we must, based on the study of this noise, decide on the presence or absence of an embedded message. In this article, we consider deep learning methods for steganoanalysis of digital cover images. We have considered several deep learning models and conduct numerous tests on various datasets. Our experiments show that deep learning does indeed make it possible to design effective stego-detectors, but this requires fine-tuning of model hyperparameters and optimization of the neural network architecture
Deep Learning Based Fuzzy Extractor for Generating Strong Keys from Biometric Face Images
No full textBiometric techniques have traditionally been used in various cybersecurity applications. For instance, some user authentication systems use biometric facial images, fingerprints, iris images, vein patterns, and much more. Most of these applications store biometric features copies (or data derived from these features). Authentication is carried out based on the results of comparing the presented biometric images with the reference ones. However, if the storage is compromised, biometric personal data will be lost and this significantly limits the scope of biometric techniques. Fuzzy extractors solve this problem. Instead of reference biometric data, fuzzy extractors extract cryptographically strong keys (secret bit strings, passwords) that are used to authenticate users. In addition, the extracted keys can be used as a source of entropy for various cryptographic mechanisms (encryption, electronic signature, etc.). In this paper, we propose a fuzzy extractor for generating cryptographically strong keys from biometric images of a human face. Our extractor uses biometric image preprocessing using deep learning methods, as well as code-based cryptosystems that provide a post-quantum (quantum-resistant) level of security
Stability conditions and moduli spaces for Kuznetsov components of Gushel-Mukai varieties
No full textWe prove the existence of Bridgeland stability conditions on the Kuznetsov
components of Gushel-Mukai varieties, and describe the structure of moduli
spaces of Bridgeland semistable objects in these categories in the
even-dimensional case. As applications, we construct a new infinite series of
unirational locally complete families of polarized hyperk\"{a}hler varieties of
K3 type, and characterize Hodge-theoretically when the Kuznetsov component of
an even-dimensional Gushel-Mukai variety is equivalent to the derived category
of a K3 surface.Comment: 47 pages, minor updates, final versio
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