Letteratura scientifica selezionata sul tema "Distance spectra"
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Articoli di riviste sul tema "Distance spectra"
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Navarro, Silvana G., Romano L. M. Corradi e Antonio Mampaso. "Distance determination to PNe using the extinction-distance method". Proceedings of the International Astronomical Union 7, S283 (luglio 2011): 460–61. http://dx.doi.org/10.1017/s1743921312011921.
Testo completoAbstract (sommario):
AbstractWe present individual distances to three PNe: NGC 6537, NGC 6781 and NGC 7027, determined by the extinction-distance method. These objects are part of a larger sample (35) of PNe that we observed at ORM. In order to apply this method, and to obtain accurate distances, we determined the spectral type of 40 to 60 stars in the line of sight of each PNe. This implied the necessity of classifying few thousands of stellar spectra with S/N ratio between 10 and 60. To solve such need we developed an ANN system to perform automatic spectral classification which could classify spectra with S/N ratio as low as 20 with an accuracy better than 2 spectral subtypes. In this poster we compare the accuracy of such distances with previous distance determinations using other methods. We conclude that it is possible to use this method to obtain the distance of a large number of PNe with better precision.
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Houston, Heidi, e Hiroo Kanamori. "Comparison of strong-motion spectra with teleseismic spectra for three magnitude 8 subduction-zone earthquakes". Bulletin of the Seismological Society of America 80, n. 4 (1 agosto 1990): 913–34. http://dx.doi.org/10.1785/bssa0800040913.
Testo completoAbstract (sommario):
Abstract We studied strong-motion spectra observed for three Mw 7.8 to 8.0 earthquakes (the 1985 Michoacán, Mexico; 1985 Valparaíso, Chile; and 1983 Akita-Oki, Japan earthquakes). We determined the decay of spectral amplitude with distance from the station, considering different measures of distance from a finite fault. We compared strong-motion spectra (Fourier acceleration spectra) observed for these three earthquakes with those estimated from the source spectrum determined from teleseismic P waves. We scaled the teleseismic source spectra to produce reference strong-motion spectra at periods from 1 to 10 sec using a simple physical model of far-field S body waves from a point source recorded at the surface of a homogeneous half-space. For all three earthquakes the reference spectral amplitudes at periods of 1 to 5 sec are about half the observed ones at distances of about 50 km. The difference increases as the distance increases. At distances of 200 to 300 km, the reference spectrum is about 1/10 of the observed one. The difference between the reference and the observed spectrum is attributed to the contribution of phases other than direct S waves and to site response. We applied corrections for the finiteness (spatial extent) of the source using a simple model of rupture propagation on a dipping two-dimensional fault. Including the source finiteness did not improve the estimate substantially at periods from 1 to 20 sec, but it modeled significant changes in the signal duration as a function of azimuth for the 1985 Michoacán earthquake. Our results can be used to establish empirical relations between the observed spectra and the half-space responses, depending on the distance and the site condition. If such empirical relations can be established, source spectra determined from teleseismic records may be used to estimate strong motions.
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Lin, Huiqiu, Dan Li e Kinkar Ch Das. "Distance between distance spectra of graphs". Linear and Multilinear Algebra 65, n. 12 (16 gennaio 2017): 2538–50. http://dx.doi.org/10.1080/03081087.2017.1278737.
Testo completo
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Cvetkovic, Dragos. "Spectral recognition of graphs". Yugoslav Journal of Operations Research 22, n. 2 (2012): 145–61. http://dx.doi.org/10.2298/yjor120925025c.
Testo completoAbstract (sommario):
At some time, in the childhood of spectral graph theory, it was conjectured that non-isomorphic graphs have different spectra, i.e. that graphs are characterized by their spectra. Very quickly this conjecture was refuted and numerous examples and families of non-isomorphic graphs with the same spectrum (cospectral graphs) were found. Still some graphs are characterized by their spectra and several mathematical papers are devoted to this topic. In applications to computer sciences, spectral graph theory is considered as very strong. The benefit of using graph spectra in treating graphs is that eigenvalues and eigenvectors of several graph matrices can be quickly computed. Spectral graph parameters contain a lot of information on the graph structure (both global and local) including some information on graph parameters that, in general, are computed by exponential algorithms. Moreover, in some applications in data mining, graph spectra are used to encode graphs themselves. The Euclidean distance between the eigenvalue sequences of two graphs on the same number of vertices is called the spectral distance of graphs. Some other spectral distances (also based on various graph matrices) have been considered as well. Two graphs are considered as similar if their spectral distance is small. If two graphs are at zero distance, they are cospectral. In this sense, cospectral graphs are similar. Other spectrally based measures of similarity between networks (not necessarily having the same number of vertices) have been used in Internet topology analysis, and in other areas. The notion of spectral distance enables the design of various meta-heuristic (e.g., tabu search, variable neighbourhood search) algorithms for constructing graphs with a given spectrum (spectral graph reconstruction). Several spectrally based pattern recognition problems appear in many areas (e.g., image segmentation in computer vision, alignment of protein-protein interaction networks in bio-informatics, recognizing hard instances for combinatorial optimization problems such as the travelling salesman problem). We give a survey of such and other graph spectral recognition techniques used in computer sciences.
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Garratt, R. C., R. W. Evans, S. S. Hasnain e P. F. Lindley. "An extended-X-ray-absorption-fine-structure investigation of diferric transferrins and their iron-binding fragments". Biochemical Journal 233, n. 2 (15 gennaio 1986): 479–84. http://dx.doi.org/10.1042/bj2330479.
Testo completoAbstract (sommario):
Iron K-edge extended-X-ray-absorption-fine-structure (e.x.a.f.s.) spectra were recorded for diferric human and rabbit serum transferrins and for diferric chicken ovotransferrin in aqueous solution; for ovotransferrin e.x.a.f.s. spectra from the N-terminal and C-terminal domain fragments were also measured. The overall spectral profiles closely resemble one another, indicating similar iron-binding sites. The simulation of the diferric ovotransferrin spectrum suggests a first co-ordination shell consisting of six low-Z ligands (nitrogen/oxygen), two ligands at a distance of approx. 0.185 nm (1.85 A) and four ligands at approx. 0.204 nm (2.04 A). The two shorter distances may correspond to Fe-O (tyrosine), whereas the longer distance is consistent with Fe-N (histidine) and Fe-O (water). Detailed analysis of the spectra of the N-terminal and C-terminal fragments indicates a difference in the short ligand distance.
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Balasubramanian, K. "Distance Spectra and Distance Polynomials of Fullerenes". Journal of Physical Chemistry 99, n. 27 (luglio 1995): 10785–96. http://dx.doi.org/10.1021/j100027a018.
Testo completo
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Paul, Somnath. "On distance and distance Laplacian spectra of corona of two graphs". Discrete Mathematics, Algorithms and Applications 08, n. 01 (26 febbraio 2016): 1650007. http://dx.doi.org/10.1142/s1793830916500075.
Testo completoAbstract (sommario):
Corona of two graphs has been defined in [F. Harary, Graph Theory (Addison-Wesley, 1969)]. In this paper, we study the distance and the distance Laplacian spectra of corona of two graphs and describe the complete distance (distance Laplacian) spectrum for some particular cases. As an application, we show that the corona operation can be used to create distance singular graphs. We also show that these results enable us to construct infinitely many pairs of distance (respectively, distance Laplacian) cospectral graphs. Last, we give a graph transformation and discuss its effect on the distance Laplacian spectral radius.
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Margolis, J. S. "Spectra at a Distance". Science 259, n. 5098 (19 febbraio 1993): 1209–10. http://dx.doi.org/10.1126/science.259.5098.1209.
Testo completo
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Wang, Chun, Yang Huang, Haibo Yuan, Huawei Zhang, Maosheng Xiang e Xiaowei Liu. "The Value-added Catalog for LAMOST DR8 Low-resolution Spectra". Astrophysical Journal Supplement Series 259, n. 2 (28 marzo 2022): 51. http://dx.doi.org/10.3847/1538-4365/ac4df7.
Testo completoAbstract (sommario):
Abstract We present a value-added catalog containing stellar parameters estimated from 7.10 million low-resolution spectra for 5.16 million unique stars with spectral signal-to-noise ratios (S/N) higher than 10 obtained by the Large Sky Area Multi-Object Fibre Spectroscopic Telescope (LAMOST) Galactic spectroscopic surveys. The catalog presents values of stellar atmospheric parameters (effective temperature T eff, surface gravity log g, metallicity [Fe/H]/[M/H]), α-element to metal abundance ratio [α/M], carbon and nitrogen to iron abundance ratios [C/Fe] and [N/Fe], and 14 bands’ absolute magnitudes deduced from LAMOST spectra using the neural network method. The spectrophotometric distances of those stars are also provided based on the distance modulus. For stars with a spectral S/N larger than 50, precisions of T eff, log g, [Fe/H], [M/H], [C/Fe], [N/Fe], and [α/M] are 85 K, 0.098 dex, 0.05 dex, 0.05 dex, 0.052 dex, 0.082 dex, and 0.027 dex, respectively. The errors of 14 band’s absolute magnitudes are 0.16–0.22 mag for stars with a spectral S/N larger than 50. The spectrophotometric distance is accurate to 8.5% for stars with a spectral S/N larger than 50 and is more accurate than the geometrical distance for stars with a distance larger than 2.0 kpc. Our estimates of [Fe/H] are reliable down to [Fe/H] ∼−3.5 dex, significantly better than previous results. The catalog provides 26,868 unique very metal-poor star candidates ([Fe/H] ≤−2.0). The catalog would be a valuable dataset to study the structure and evolution of the galaxy, especially the solar neighborhood and the outer disk.
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Abdollahi, Alireza, Shahrooz Janbaz e Mohammad Reza Oboudi. "Distance between spectra of graphs". Linear Algebra and its Applications 466 (febbraio 2015): 401–8. http://dx.doi.org/10.1016/j.laa.2014.10.020.
Testo completoTesi sul tema "Distance spectra"
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Taylor, Melinda Marie. "Analysis of Cepheid Spectra". Thesis, The University of Sydney, 1998. http://hdl.handle.net/2123/388.
Testo completoAbstract (sommario):
Using high resolution optical spectra from Mount John University Observatory, Mount Stromlo Observatory and the Anglo-Australian Observatory, new, high accuracy radial velocity curves have been obtained for the two bright southern Cepheids l carinae (HR 3884) and beta doradus (HR 1922). An indepth investigation into period variations, cycle-to-cycle and long-term variations in the velocity curves and the reliability of the combination of velocity data from different observatories is carried out. Evidence for shock waves in the atmosphere of l car and resonance in beta dor is discussed. A grid of static model atmospheres incorporating plane-parallel geometry is compared with the observational spectra of both Cepheids, using line depth ratios, to determine the variation in effective temperature, surface gravity and microturbulence with phase. This information is used to determine the phase dependence of the surface-brightness for both Cepheids. The surface brightness variation with phase was found to follow an almost linear relationship. The distance to and radius of the Cepheids are determined using both a near-infrared version of the Barnes-Evans method and the Fourier Baade-Wesselink (BW) method. The derived radii and distances agree within the limits of the errors for both methods. The Fourier BW method was found to be very sensitive to phase shifts between the photometric and spectroscopic data and the derived distance highly dependent on the assumed reddening. An investigation into line profile variations in l car and beta dor has revealed the magnitude of these phenomena increase as the pulsational period of the Cepheid increases. It is estimated that line level variations introduce an additional uncertainty into derived radii of approximately 4 per cent for beta dor and 10 per cent in lcar. The uncertainty introduced into derived distances and radii by line profile asymmetries was estimated to be of the order of 6 per cent in beta dor and 10 per cent in l car. A comparative analysis is made of the hydrogen line radial velocity curves of l car and beta dor. A trend in the properties of these radial velocity curves with period has been revealed. In longer period Cepheids, the Halpha line seems to be forming in a region that does not partake in the pulsation as a whole, probably in a chromospheric shell. A quantitative analysis of the asymmetries in these lines reveal large redward asymmetries near maximum infall velocity. The magnitude of these asymmetries and the period for which they are present are larger in l Car than in beta dor. The blueward asymmetries in the Halpha line in l Car are comparable in magnitude to the redward asymmetries while the other lines exhibit only small blueward asymmetries. A qualitative analysis of these line profiles with phase reveal no conclusive evidence for line doubling in these Cepheids. Evidence of emission is found in the Halpha and H Beta lines of beta dor and l car. The strength and duration of the emission is found to be greater in the longer period Cepheid. Although it is likely that this emission is shock-related, theoretical work is needed to determine the exact origin of the emission. A non-LTE radiative hydrodynamic model for l Car has been created. This atmosphere will be used in further work to calculate synthetic spectral line profiles which will aid the interpretation of our observational results.
2
Taylor, Melinda Marie. "Analysis of Cepheid Spectra". University of Sydney, Physics, 1998. http://hdl.handle.net/2123/388.
Testo completoAbstract (sommario):
Using high resolution optical spectra from Mount John University Observatory, Mount Stromlo Observatory and the Anglo-Australian Observatory, new, high accuracy radial velocity curves have been obtained for the two bright southern Cepheids l carinae (HR 3884) and beta doradus (HR 1922). An indepth investigation into period variations, cycle-to-cycle and long-term variations in the velocity curves and the reliability of the combination of velocity data from different observatories is carried out. Evidence for shock waves in the atmosphere of l car and resonance in beta dor is discussed. A grid of static model atmospheres incorporating plane-parallel geometry is compared with the observational spectra of both Cepheids, using line depth ratios, to determine the variation in effective temperature, surface gravity and microturbulence with phase. This information is used to determine the phase dependence of the surface-brightness for both Cepheids. The surface brightness variation with phase was found to follow an almost linear relationship. The distance to and radius of the Cepheids are determined using both a near-infrared version of the Barnes-Evans method and the Fourier Baade-Wesselink (BW) method. The derived radii and distances agree within the limits of the errors for both methods. The Fourier BW method was found to be very sensitive to phase shifts between the photometric and spectroscopic data and the derived distance highly dependent on the assumed reddening. An investigation into line profile variations in l car and beta dor has revealed the magnitude of these phenomena increase as the pulsational period of the Cepheid increases. It is estimated that line level variations introduce an additional uncertainty into derived radii of approximately 4 per cent for beta dor and 10 per cent in lcar. The uncertainty introduced into derived distances and radii by line profile asymmetries was estimated to be of the order of 6 per cent in beta dor and 10 per cent in l car. A comparative analysis is made of the hydrogen line radial velocity curves of l car and beta dor. A trend in the properties of these radial velocity curves with period has been revealed. In longer period Cepheids, the Halpha line seems to be forming in a region that does not partake in the pulsation as a whole, probably in a chromospheric shell. A quantitative analysis of the asymmetries in these lines reveal large redward asymmetries near maximum infall velocity. The magnitude of these asymmetries and the period for which they are present are larger in l Car than in beta dor. The blueward asymmetries in the Halpha line in l Car are comparable in magnitude to the redward asymmetries while the other lines exhibit only small blueward asymmetries. A qualitative analysis of these line profiles with phase reveal no conclusive evidence for line doubling in these Cepheids. Evidence of emission is found in the Halpha and H Beta lines of beta dor and l car. The strength and duration of the emission is found to be greater in the longer period Cepheid. Although it is likely that this emission is shock-related, theoretical work is needed to determine the exact origin of the emission. A non-LTE radiative hydrodynamic model for l Car has been created. This atmosphere will be used in further work to calculate synthetic spectral line profiles which will aid the interpretation of our observational results.
3
Harrell, Dameon C. (Dameon Cartíer) 1976. "Effects of microphone type and distance upon the spectra of speech sounds". Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/80067.
Testo completoAbstract (sommario):
Thesis (S.B. and M.Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1999.Includes bibliographical references (leaf 71).
by Dameon C. Harrell.
S.B.and M.Eng.
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Ellouze, Malek. "Propriétés de distance des codes polaires : théorie et applications". Electronic Thesis or Diss., Bordeaux, 2024. http://www.theses.fr/2024BORD0132.
Testo completoAbstract (sommario):
Les codes correcteurs d'erreurs sont essentiels pour garantir des transmissions de données fiables, surtout dans des contextes où diverses interférences peuvent compromettre l'intégrité des informations.Les codes polaires sont l'une des familles de codes correcteurs d'erreurs les plus compétitives. Ils peuvent atteindre la capacité du canal de Shannon grâce à un encodage et un décodage efficaces pour de très grandes tailles de codes. Pour ces raisons, les codes polaires ont été inclus dans le standard 5G. De plus, ils sont l'objet de plusieurs recherches pour le futur standard 6G.Cependant, les codes polaires tels que initialement construits pour un décodage à annulations successives (SC) atteignent des performances limitées pour une taille modérée de codes. Cela est lié d’une part à leurs faibles propriétés de distance et d'autre part à la nature du décodage à décision dure. Cependant grâce à l'utilisation d'un décodage par listes principalement ainsi que plusieurs autres améliorations, notamment la pré-transformation, les codes polaires sont désormais compétitifs par rapport aux codes LDPC et aux turbo-codes.Dans ce contexte, cette thèse a pour objet l'étude et l’analyse des codes polaires en se concentrant sur deux aspects fondamentaux qui influencent ces performances : leurs propriétés de distance et leurs performances pour un décodage par listes.Après une revue approfondie de la définition des codes polaires, des différentes variantes, des algorithmes de décodage et des concepts liés à leur spectre de distances, une première contribution est permet de caractériser une partie des propriétés de distance des codes polaires classiques et pré-transformés. Cette méthode présente l'avantage d'être totalement indépendante de la construction code. C'est pourquoi, elle peut être appliquée à différentes configurations. De plus, l'approche proposée se distingue par une complexité de calcul moins élevée que les méthodes présentes dans la littérature.Les techniques de poinçonnage et de raccourcissement des codes polaires sont introduites comme des variantes permettant d’obtenir des codes polaires dont les tailles ne sont pas nécessairement des puissance de deux. Une deuxième contribution consiste à généraliser l’approche développée dans le cadre de la thèse aux codes polaires poinçonnés et raccourcis. Il est à souligner que cette dernière peut être appliquée quelque soit la technique de poinçonnage et/ou de raccourcissement..Finalement, la question de la taille de liste nécessaire pour un décodage liste (SCL) afin d’atteindre les performances de maximum de vraisemblance est traitée. Celle-ci étant dépendante de la construction du code, un algorithme est proposé afin d’estimer la taille moyenne de liste nécessaire pour atteindre les meilleurs performances de décodage. Cela constitue une contribution très utile pour la construction de codes qui offrent un compromis entre les propriétés de distance et un décodage par liste ayant une complexité calculatoire maîtriséeError-correcting codes are essential for ensuring reliable data transmission, especially in contexts where various interferences may compromise data integrity. Polar codes are one of the most competitive families of error-correcting codes. They can achieve Shannon channel capacity through efficient encoding and decoding for very large code lengths. For these reasons, polar codes have been included in the 5G standard. Additionally, they are the subject of several research efforts for the future 6G standard.However, polar codes, as originally designed for successive cancellation (SC) decoding, exhibit limited performance for moderate code lengths. This is in part due to their weak distance properties and partly to the nature of hard decision decoding. However, with the use of mainly list decoding and several other enhancements, including pre-transformation, polar codes are now competitive with LDPC and turbo codes.In this context, this thesis aims to study and analyze polar codes focusing on two fundamental aspects that influence their performance: their distance properties and their performance for list decoding.After a comprehensive review of polar code definition, various variants, decoding algorithms, and concepts related to their distance spectrum, a first contribution characterizes some distance properties of classical and pre-transformed polar codes. This method has the advantage of being entirely independent of code construction, making it applicable to different configurations. Moreover, the proposed approach distinguishes itself by having lower computational complexity than methods in the existing literature.Polar code puncturing and shortening techniques are introduced as variants to obtain polar codes whose sizes are not necessarily powers of two. A second contribution involves generalizing the developed approach within the thesis to punctured and shortened polar codes. It is noteworthy that this approach can be applied regardless of the puncturing and/or shortening technique used.Finally, the question of the list size necessary for list decoding (SCL) to achieve maximum likelihood performance is addressed. Since this depends on code construction, an algorithm is proposed to estimate the average list size required to achieve the best decoding performance. This constitutes a very useful contribution for constructing codes that offer a compromise between distance properties and list decoding with controlled computational complexity
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Chen, Brenden Chong. "Robust image hash functions using higher order spectra". Thesis, Queensland University of Technology, 2012. https://eprints.qut.edu.au/61087/1/Brenden_Chen_Thesis.pdf.
Testo completoAbstract (sommario):
Robust hashing is an emerging field that can be used to hash certain data types in applications unsuitable for traditional cryptographic hashing methods. Traditional hashing functions have been used extensively for data/message integrity, data/message authentication, efficient file identification and password verification.
These applications are possible because the hashing process is compressive, allowing for efficient comparisons in the hash domain but non-invertible meaning hashes can be used without revealing the original data. These techniques were developed with deterministic (non-changing) inputs such as files and passwords.
For such data types a 1-bit or one character change can be significant, as a result the hashing process is sensitive to any change in the input. Unfortunately, there are certain applications where input data are not perfectly deterministic and minor changes cannot be avoided. Digital images and biometric features are two types of data where such changes exist but do not alter the meaning or appearance of the input. For such data types cryptographic hash functions cannot be usefully applied.
In light of this, robust hashing has been developed as an alternative to cryptographic hashing and is designed to be robust to minor changes in the input.
Although similar in name, robust hashing is fundamentally different from cryptographic hashing. Current robust hashing techniques are not based on cryptographic methods, but instead on pattern recognition techniques. Modern robust hashing algorithms consist of feature extraction followed by a randomization stage that introduces non-invertibility and compression, followed by quantization and binary encoding to produce a binary hash output. In order to preserve robustness of the extracted features, most randomization methods are linear and this is detrimental to the security aspects required of hash functions. Furthermore, the quantization and encoding stages used to binarize real-valued features requires the learning of appropriate quantization thresholds. How these thresholds are learnt has an important effect on hashing accuracy and the mere presence of such thresholds are a source of information leakage that can reduce hashing security.
This dissertation outlines a systematic investigation of the quantization and encoding stages of robust hash functions. While existing literature has focused on the importance of quantization scheme, this research is the first to emphasise the importance of the quantizer training on both hashing accuracy and hashing security. The quantizer training process is presented in a statistical framework which allows a theoretical analysis of the effects of quantizer training on hashing performance. This is experimentally verified using a number of baseline robust image hashing algorithms over a large database of real world images.
This dissertation also proposes a new randomization method for robust image hashing based on Higher Order Spectra (HOS) and Radon projections. The method is non-linear and this is an essential requirement for non-invertibility.
The method is also designed to produce features more suited for quantization and encoding. The system can operate without the need for quantizer training, is more easily encoded and displays improved hashing performance when compared to existing robust image hashing algorithms. The dissertation also shows how the HOS method can be adapted to work with biometric features obtained from 2D and 3D face images.
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Entesar, Abdullah Ali. "Statistical analysis of truck loading on Swedish highways". Thesis, KTH, Transportvetenskap, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-45980.
Testo completoAbstract (sommario):
Vehicle over loading, or single axle over loading, is one of the major causes of pavement deterioration. Trafik Verket (TV), the Swedish Transport Administration, recognized that the current process for estimating traffic volume should be reevaluated, and if possible improved. This degree project uses data from the Bridge Weigh in Motion (BWIM) system to study the actual loads applied to Swedish highways. The axle load spectrum is plotted with the conventional frequency distribution plots, and with a new cumulative distribution approach. The paper introduces the maximum allowable potential vehicle weight MAPVW concept, and uses this visual technique to identify overloads for different vehicle geometries. The paper concludes that for 5 and 6 axle trucks the triple axle is frequently overloaded, while for longer trucks one of the dual axles is often over loaded. The highest over loads tend to be on the driving axle, suggesting incorrect loading procedures.
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Nader, Rafic. "A study concerning the positive semi-definite property for similarity matrices and for doubly stochastic matrices with some applications". Thesis, Normandie, 2019. http://www.theses.fr/2019NORMC210.
Testo completoAbstract (sommario):
La théorie des matrices s'est développée rapidement au cours des dernières décennies en raison de son large éventail d'applications et de ses nombreux liens avec différents domaines des mathématiques, de l'économie, de l'apprentissage automatique et du traitement du signal. Cette thèse concerne trois axes principaux liés à deux objets d'étude fondamentaux de la théorie des matrices et apparaissant naturellement dans de nombreuses applications, à savoir les matrices semi-définies positives et les matrices doublement stochastiques.Un concept qui découle naturellement du domaine de l'apprentissage automatique et qui est lié à la propriété semi-définie positive est celui des matrices de similarité. En fait, les matrices de similarité qui sont semi-définies positives revêtent une importance particulière en raison de leur capacité à définir des distances métriques. Cette thèse explorera la propriété semi-définie positive pour une liste de matrices de similarité trouvées dans la littérature. De plus, nous présentons de nouveaux résultats concernant les propriétés définie positive et semi-définie trois-positive de certains matrices de similarité. Une discussion détaillée des nombreuses applications de tous ces propriétés dans divers domaines est également établie.D'autre part, un problème récent de l'analyse matricielle implique l'étude des racines des matrices stochastiques, ce qui s'avère important dans les modèles de chaîne de Markov en finance. Nous étendons l'analyse de ce problème aux matrices doublement stochastiques semi-définies positives. Nous montrons d'abord certaines propriétés géométriques de l'ensemble de toutes les matrices semi-définies positives doublement stochastiques d'ordre n ayant la p-ième racine doublement stochastique pour un entier donné p . En utilisant la théorie des M-matrices et le problème inverse des valeurs propres des matrices symétriques doublement stochastiques (SDIEP), nous présentons également quelques méthodes pour trouver des classes de matrices semi-définies positives doublement stochastiques ayant des p-ièmes racines doublement stochastiques pour tout entier p.Dans le contexte du SDIEP, qui est le problème de caractériser ces listes de nombres réels qui puissent constituer le spectre d’une matrice symétrique doublement stochastique, nous présentons quelques nouveaux résultats le long de cette ligne. En particulier, nous proposons d’utiliser une méthode récursive de construction de matrices doublement stochastiques afin d'obtenir de nouvelles conditions suffisantes indépendantes pour SDIEP. Enfin, nous concentrons notre attention sur les spectres normalisés de Suleimanova, qui constituent un cas particulier des spectres introduits par Suleimanova. En particulier, nous prouvons que de tels spectres ne sont pas toujours réalisables et nous construisons trois familles de conditions suffisantes qui affinent les conditions suffisantes précédemment connues pour SDIEP dans le cas particulier des spectres normalisés de SuleimanovaMatrix theory has shown its importance by its wide range of applications in different fields such as statistics, machine learning, economics and signal processing. This thesis concerns three main axis related to two fundamental objects of study in matrix theory and that arise naturally in many applications, that are positive semi-definite matrices and doubly stochastic matrices.One concept which stems naturally from machine learning area and is related to the positive semi-definite property, is the one of similarity matrices. In fact, similarity matrices that are positive semi-definite are of particular importance because of their ability to define metric distances. This thesis will explore the latter desirable structure for a list of similarity matrices found in the literature. Moreover, we present new results concerning the strictly positive definite and the three positive semi-definite properties of particular similarity matrices. A detailed discussion of the many applications of all these properties in various fields is also established.On the other hand, an interesting research field in matrix analysis involves the study of roots of stochastic matrices which is important in Markov chain models in finance and healthcare. We extend the analysis of this problem to positive semi-definite doubly stochastic matrices.Our contributions include some geometrical properties of the set of all positive semi-definite doubly stochastic matrices of order n with nonnegative pth roots for a given integer p. We also present methods for finding classes of positive semi-definite doubly stochastic matrices that have doubly stochastic pth roots for all p, by making use of the theory of M-Matrices and the symmetric doubly stochastic inverse eigenvalue problem (SDIEP), which is also of independent interest.In the context of the SDIEP, which is the problem of characterising those lists of real numbers which are realisable as the spectrum of some symmetric doubly stochastic matrix, we present some new results along this line. In particular, we propose to use a recursive method on constructing doubly stochastic matrices from smaller size matrices with known spectra to obtain new independent sufficient conditions for SDIEP. Finally, we focus our attention on the realizability by a symmetric doubly stochastic matrix of normalised Suleimanova spectra which is a normalized variant of the spectra introduced by Suleimanova. In particular, we prove that such spectra is not always realizable for odd orders and we construct three families of sufficient conditions that make a refinement for previously known sufficient conditions for SDIEP in the particular case of normalized Suleimanova spectra
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Godbout, Martin. "Mesures de distances et de spectres résolus en distance en utilisant les battements hétérodynes entre peignes de fréquences". Thesis, Université Laval, 2010. http://www.theses.ulaval.ca/2010/27451/27451.pdf.
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Bertrand, Jérôme. "Pincement spectral en courbure positive". Paris 11, 2003. https://tel.archives-ouvertes.fr/tel-00008705.
Testo completoAbstract (sommario):
Sur l'ensemble des variétés Riemanniennes compactes à courbure de Ricci positive (on normalise par Ric ≥ (n -1)g), la première valeur propre du Laplacien agissant sur les fonctions atteint son minimum uniquement pour la sphère canonique. Dans cette thèse, nous caractérisons, à l'aide de la distance de Gromov-Hausdorff, les variétés Riemanniennes à courbure positive dont les premières valeurs propres du Laplacien sont proches de celles de la sphère canonique. Cette propriété de minimimalité du spectre de la sphère s'étend par un procédé de symétrisation, au spectre de Dirichlet des boules géodésiques de la sphère parmi les domaines de variétés à courbure de Ricci positive. Nous étudions les domaines de variétés à courbure de Ricci positive dont la première valeur propre de Dirichlet est presque minimale. En particulier, nous montrons qu'un domaine dont la première valeur propre de Dirichlet est proche de celle d'un hémisphère est Gromov-Hausdorff proche d'un hémisphère d'un sinus produit torduOn the set of compact Riemannian manifolds with positive Ricci curvature (normalized by Ric ≥ (n-1)g), the first eigenvalue of the Laplacian acting on functions reaches its minimum only for the round sphere. In this thesis, we characterize, using the Gromov-Hausdorff distance, Riemannian manifolds with positive Ricci curvature whose first eigenvalues are close to those of the round sphere. This property of minimality of the spectrum of the round sphere has been extended by a symmetrization principle, to the Dirichlet spectrum of the geodesic balls of the round sphere among the domains of Riemannian manifolds with positive curvature. We study the domains of Riemannian manifolds with positive Ricci curvature whose first Dirichlet eigenvalue is almost minimal. In particular, we show that a domain whose first Dirichlet eigenvalue is close to the one of a hemisphere is Gromov-Hausdorff close to a hemisphere of a sine warped product
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Deborah, Hilda. "Towards spectral mathematical morphology". Thesis, Poitiers, 2016. http://www.theses.fr/2016POIT2328/document.
Testo completoAbstract (sommario):
En fournissant en plus de l'information spatiale une mesure spectrale en fonction des longueurs d'ondes, l'imagerie hyperspectrale s'enorgueillie d'atteindre une précision bien plus importante que l'imagerie couleur. Grâce à cela, elle a été utilisée en contrôle qualité, inspection de matériaux,… Cependant, pour exploiter pleinement ce potentiel, il est important de traiter la donnée spectrale comme une mesure, d'où la nécessité de la métrologie, pour laquelle exactitude, incertitude et biais doivent être maitrisés à tous les niveaux de traitement.Face à cet objectif, nous avons choisi de développer une approche non-linéaire, basée sur la morphologie mathématique et de l'étendre au domaine spectral par le biais d'une relation d'ordre spectral basée sur les fonctions de distance. Une nouvelle fonction de distance spectrale et une nouvelle relation d'ordonnancement sont ainsi proposées. De plus, un nouvel outil d'analyse du basé sur les histogrammes de différences spectrales a été développé.Afin d'assurer la validité des opérateurs, une validation théorique rigoureuse et une évaluation métrologique ont été mises en œuvre à chaque étage de développement. Des protocoles d'évaluation de la qualité des traitements morphologiques sont proposés, exploitant des jeux de données artificielles pour la validation théorique, des ensembles de données dont certaines caractéristiques sont connues pour évaluer la robustesse et la stabilité et des jeux de données de cas réel pour prouver l'intérêt des approches en contexte applicatif. Les applications sont développées dans le contexte du patrimoine culturel pour l'analyse de peintures et pigmentsProviding not only spatial information but also spectral measure as a function of wavelength, hyperspectral imaging boasts a much greater gain in accuracy than the traditional color imaging. And for this capability, hyperspectral imaging has been employed for quality control, inspection of materials in various fields. However, to fully exploit this potential, it is important to process the spectral data as a measure. This induces the need of metrology where accuracy, uncertainty, and bias are managed at every level of processing.Aiming at developing a metrological image processing framework for spectral data, we select to develop a nonlinear approach using the mathematical morphology framework and extended it to the spectral domain by means of a distance-based ordering relation. A novel spectral distance function and spectral ordering relation are proposed, in addition of a new analysis tools based on spectral differences. To ensure the validity of the spectral mathematical morphology framework, rigorous theoretical validation and metrological assessment are carried out at each development stages. So, protocols for quality assessment of spectral image processing tools are developed. These protocols consist of artificial datasets to validate completely the theoretical requirements, datasets with known characteristics to assess the robustness and stability, and datasets from real cases to proof the usefulness of the framework on applicative context. The application tasks themselves are within the cultural heritage domain, where the target images come from pigments and paintings
Hyperspektral avbildning muliggjør mye mer nøyaktige målinger enn tradisjonelle gråskala og fargebilder, gjennom både høy romlig og spektral oppløsning (funksjon av bølgelengde). På grunn av dette har hyperspektral avbildning blitt anvendt i økende grad ulike applikasjoner som kvalitetskontroll og inspeksjon av materialer. Men for å fullt ut utnytte sitt potensiale, er det viktig å være i stand til å behandle spektrale bildedata som målinger på en gyldig måte. Dette induserer behovet for metrologi, der nøyaktighet, usikkerhet og skjevhet blir adressert og kontrollert på alle nivå av bildebehandlingen.Med sikte på å utvikle et metrologisk rammeverk for spektral bildebehandling valgte vi en ikke-lineær metodikk basert på det etablerte matematisk morfologi-rammeverket. Vi har utvidet dette rammeverket til det spektrale domenet ved hjelp av en avstandsbasert sorteringsrelasjon. En ny spektral avstandsfunksjon og nye spektrale sorteringsrelasjoner ble foreslått, samt nye verktøy for spektral bildeanalyse basert på histogrammer av spektrale forskjeller.For å sikre gyldigheten av det nye spektrale rammeverket for matematisk morfologi, har vi utført en grundig teoretisk validering og metrologisk vurde-ring på hvert trinn i utviklingen. Dermed er og-så nye protokoller for kvalitetsvurdering av spektrale bildebehandlingsverktøy utviklet. Disse protokollene består av kunstige datasett for å validere de teoretiske måletekniske kravene, bildedatasett med kjente egenskaper for å vurdere robustheten og stabiliteten, og datasett fra reelle anvendelser for å bevise nytten av rammeverket i en anvendt sammenheng. De valgte anvendelsene er innenfor kulturminnefeltet, hvor de analyserte bildene er av pigmenter og malerier
Libri sul tema "Distance spectra"
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Elliott, James L. New mysteries at Chiron: Final technical report. [Washington, DC: National Aeronautics and Space Administration, 1998.
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Patanè, Giuseppe. An Introduction to Laplacian Spectral Distances and Kernels. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-031-02593-8.
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J, Maddox S., e Aragón-Salamanca A, a cura di. Wide field spectroscopy and the distant universe: The 35th Herstmonceux Conference, Cambridge, United Kingdom, July 4-8, 1994. Singapore: World Scientific, 1995.
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Edmunds, D. E., e W. D. Evans. Essential Spectra of General Second-Order Differential Operators. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198812050.003.0010.
Testo completoAbstract (sommario):
In this chapter, the operators considered are those m-sectorial operators discussed in Chapter VII, and the essential spectra are the sets defined in Chapter IX that remain invariant under compact perturbation. A generalization of a result of Persson is used to determine the least point of the essential spectrum. Davies’ mean distance function is introduced and consequences investigated.
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Mumenthaler, Christian. Self-correcting distance geometry for the automatic assignment of NMR NOESY spectra and the prediction of protein tertiary structures. 1996.
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Eland, John H. D., e Raimund Feifel. Mainly aliphatic molecules. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198788980.003.0007.
Testo completoAbstract (sommario):
Double photoionisation spectra of homologous iodides and alcohols, acetonitrile, methyl mercaptan, acetaldehyde, acetone, norbornane, cyclooctatetraene, and TMMD are presented. Effects on the spectra of these molecules from electronic state congestion and geometry changes on ionisation mean that only the lowest dication states can be identified. As little detailed analysis of the individual spectra is possible, this chapter presents the molecules in groups rather than individually. In this chapter, molecules are ordered more thematically than strictly by size. The chapter starts with four homologous iodides and three homologous alcohols. Then this chapter takes some individual molecules with different substituent groups and proceed to a few larger molecules. The chapter demonstrates the dominant effect of the distance to which charges can separate in the dication on the double ionisation threshold.
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Greyser, Naomi. “Spectres of Liberty” and the Archive. Oxford University Press, 2017. http://dx.doi.org/10.1093/oso/9780190460983.003.0007.
Testo completoAbstract (sommario):
This epilogue considers the legacy of nineteenth-century sentimentalism, turning to contemporary civic statuary that memorializes nineteenth-century sentimentalists. Juxtaposing this statuary with the hauntingly ephemeral installation The Ghost of Liberty Street Church, the chapter offers postpresentist inquiry as a method that regards the archive as an urgent and poignantly incomplete political project. Where historicist approaches emphasize distance and difference from history through periodization, and charges of presentism name historians’ overidentification with the past, postpresentism holds in view intimacy and distance between past and the present. The epilogue lays out postpresentist readings of sculptures of Harriet E. Wilson in Milford, New Hampshire; Winnemucca Hopkins and Sojourner Truth in the United States Capitol Rotunda; and Elizabeth Cady Stanton, Amelia Bloomer, and Susan B. Anthony in Seneca Falls, New York. These statues’ site-specific installations bring into relief the raced, gendered, and colonial legacies of the grounds beneath their podia and feet.
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Patane, Giuseppe. Introduction to Laplacian Spectral Distances and Kernels: Theory, Computation, and Applications. Morgan & Claypool Publishers, 2017.
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Patanè, Giuseppe. Introduction to Laplacian Spectral Distances and Kernels: Theory, Computation, and Applications. Springer International Publishing AG, 2017.
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Patanè, Giuseppe, e Brian A. Barsky. Introduction to Laplacian Spectral Distances and Kernels: Theory, Computation, and Applications. Morgan & Claypool Publishers, 2017.
Cerca il testo completoCapitoli di libri sul tema "Distance spectra"
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Sun, Rui, e Wanwan Qi. "Quantitative Evaluation of Four Kinds of Site Seismic Response Analysis Methods Using DTW". In Lecture Notes in Civil Engineering, 495–502. Singapore: Springer Nature Singapore, 2023. http://dx.doi.org/10.1007/978-981-99-1748-8_43.
Testo completoAbstract (sommario):
AbstractIn order to quantitatively evaluate the one-dimensional site seismic response analysis methods, this article selected 2418 ground motion records of Japan KiK-net strong-motion seismograph network and 2418 groups of acceleration response spectra calculated by DEEPSOIL, SHAKE2000, SOILQUAKE and SOILRESPONSE, and then` used the dynamic time warping (DTW) algorithm to calculate the DTW distance between the measured acceleration response spectrum and the calculated acceleration response spectrum. The average DTW distance and change trend in different PGA ranges were compared and analyzed. The average DTW distance of the four methods in weak ground motion were similar, and in the strong ground motion, the average DTW distance of SOILRESPONSE was smaller than the other three methods. The DTW distance of the four methods increased with the increase of PGA, the growth rate of SOILRESPONSE was significantly lower than the other three methods. DTW distance can accurately and effectively reflect the difference between response spectrum, which provides a new method for quantitative evaluation of one-dimensional site seismic response analysis method.
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Hustedt, Eric J., e Albert H. Beth. "Structural Information from CW-EPR Spectra of Dipolar Coupled Nitroxide Spin Labels". In Distance Measurements in Biological Systems by EPR, 155–84. Boston, MA: Springer US, 2002. http://dx.doi.org/10.1007/0-306-47109-4_3.
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Cornean, Horia D., e Radu Purice. "On the Regularity of the Hausdorff Distance Between Spectra of Perturbed Magnetic Hamiltonians". In Spectral Analysis of Quantum Hamiltonians, 55–66. Basel: Springer Basel, 2012. http://dx.doi.org/10.1007/978-3-0348-0414-1_4.
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Reames, Donald V. "High Energies and Radiation Effects". In Solar Energetic Particles, 135–49. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-66402-2_6.
Testo completoAbstract (sommario):
AbstractIn this chapter we characterize the high-energy spectra of protons that can penetrate shielding and determine the radiation dose to humans and equipment in space. High-energy spectral breaks or “knees”, seen in all large SEP events, determine the contribution of highly penetrating protons. The streaming limit, discussed earlier, places an upper bound on particle fluences early in events and the radial variation of intensities is important for near-solar and deep-space missions. The streaming limit is a strong function of radial distance from the Sun. We also consider requirements for a radiation storm shelter for deep space, a mission to Mars, suitability of exoplanets for life, and radiation-induced chemistry of the upper atmosphere of Earth.
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Kveder, Vitaly, Valeri I. Orlov, M. Khorosheva e Michael Seibt. "Influence of the Dislocation Travel Distance on the DLTS Spectra of Dislocations in Cz-Si". In Solid State Phenomena, 175–82. Stafa: Trans Tech Publications Ltd., 2007. http://dx.doi.org/10.4028/3-908451-43-4.175.
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Buendia-Aviles, Sonia, Margarita Cunill-Rodríguez, José A. Delgado-Atencio, José L. Arce-Diego e Félix Fanjul-Vélez. "Influence of Tilt Angle and Probe-Sample Distance on Tissue Diagnosis by Diffuse Reflection Spectra". In IFMBE Proceedings, 447–52. Cham: Springer Nature Switzerland, 2024. http://dx.doi.org/10.1007/978-3-031-49068-2_46.
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Patanè, Giuseppe. "Discrete Spectral Distances". In An Introduction to Laplacian Spectral Distances and Kernels, 53–69. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-031-02593-8_4.
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Zou, Qiang, Hui Fang, Fei Liu, Wenwen Kong e Yong He. "Comparative Study of Distance Discriminant Analysis and Bp Neural Network for Identification of Rapeseed Cultivars Using Visible/Near Infrared Spectra". In Computer and Computing Technologies in Agriculture IV, 124–33. Berlin, Heidelberg: Springer Berlin Heidelberg, 2011. http://dx.doi.org/10.1007/978-3-642-18369-0_15.
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Liu, Rong, Hao Zhang e Oliver van Kaick. "Spectral Sequencing Based on Graph Distance". In Geometric Modeling and Processing - GMP 2006, 630–36. Berlin, Heidelberg: Springer Berlin Heidelberg, 2006. http://dx.doi.org/10.1007/11802914_50.
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Wang, Nian, Jun Tang, Jiang Zhang, Yi-Zheng Fan e Dong Liang. "Spectral Edit Distance Method for Image Clustering". In Advances in Data and Web Management, 350–57. Berlin, Heidelberg: Springer Berlin Heidelberg, 2007. http://dx.doi.org/10.1007/978-3-540-72524-4_37.
Testo completoAtti di convegni sul tema "Distance spectra"
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Robles-Kelly e Hancock. "Edit distance from graph spectra". In ICCV 2003: 9th International Conference on Computer Vision. IEEE, 2003. http://dx.doi.org/10.1109/iccv.2003.1238347.
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Xie, Kai, e Jing Li. "Evaluating Distance Spectra for Turbo Codes". In IEEE GLOBECOM 2007-2007 IEEE Global Telecommunications Conference. IEEE, 2007. http://dx.doi.org/10.1109/glocom.2007.583.
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Chbat, M. W., P. R. Prucnal, M. N. Islam, C. E. Soccolich e J. P. Gordon. "Spectral interference effects in long-distance soliton propagation". In OSA Annual Meeting. Washington, D.C.: Optica Publishing Group, 1992. http://dx.doi.org/10.1364/oam.1992.thss3.
Testo completoAbstract (sommario):
We have observed experimentally, and modelled both analytically and numerically, the appearance of oscillations in the output spectrum after a reshaped optical soliton has propagated over a few tens of soliton periods in an optical fiber. An optical pulse with sufficient intensity will reshape into a fundamental soliton after propagating a few soliton periods by stripping off the non-soliton part of its energy, which will propagate radiatively in the fiber. This radiative field has a spectrum that is overlapped with the output soliton spectrum, and the phase difference between the two spectra is both frequency and distance dependent. Thus the interference between the two fields will cause a modulation of the output field spectrum, with peaks at discrete frequencies that depend on the distance of propagation. An analytical study, based on the analysis in Ref. 1, gives results in good agreement with the observed spectra. This study, carried for hyperbolic secant-shaped input pulses for which the soliton part of the asymptotic solution of the nonlinear Schrödinger equation is exactly known,2 allows the calculation of the non-soliton field after several soliton periods of propagation, and therefore the spectrum of the total output field. In addition, numerical results obtained by a split-step Fourier transform technique show good agreement with the analytical results.
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Euán, Carolina, Joaquín Ortega e Pedro C. Alvarez-Esteban. "Detecting Stationary Intervals for Random Waves Using Time Series Clustering". In ASME 2014 33rd International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/omae2014-24269.
Testo completoAbstract (sommario):
The problem of detecting changes in the state of the sea is very important for the analysis and determination of wave climate in a given location. Wave measurements are frequently statistically analyzed as a time series, and segmentation algorithms developed in this context are used to determine change-points. However, most methods found in the literature consider the case of instantaneous changes in the time series, which is not usually the case for sea waves, where changes take a certain time interval to occur. We propose a new segmentation method that allows for the presence of transition intervals between successive stationary periods, and is based on the analysis of distances of normalized spectra to detect clusters in the time series. The series is divided into 30-minutes intervals and the spectral density is estimated for each one. The normalized spectra are compared using the Total Variation distance and a hierarchical clustering method is applied to the distance matrix. The information obtained from the clustering algorithm is used to classify the intervals as belonging to a stationary or a transition period We present simulation studies to validate the method and examples of applications to real data.
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Schaefer, Bradley E. "Distance to gamma ray bursts from their soft x-ray spectra". In Gamma-ray bursts: Second workshop. AIP, 1994. http://dx.doi.org/10.1063/1.45892.
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Dykman, M. I., R. Mannella, P. V. E. McClintock e N. G. Stocks. "Super-Narrow Spectral Peaks: New Critical Phenomena in Optically Bistable Systems". In Nonlinear Dynamics in Optical Systems. Washington, D.C.: Optica Publishing Group, 1990. http://dx.doi.org/10.1364/nldos.1990.ob266.
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Fluctuation-induced transitions between coexisting attractors in a periodically driven nonlinear system have been investigated theoretically and with an analogue electronic circuit model. Calculations and measurements of power spectral densities of fluctuations have revealed superimposed twin-peaked partial spectra and a super-narrow spectral peak whose intensity depends critically on the distance from the phase transition.
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Wang, Dong, Bin He e Quanhu Zhang. "Application of Genetic Algorithm in Neutron Spectrum Unfolding". In 18th International Conference on Nuclear Engineering. ASMEDC, 2010. http://dx.doi.org/10.1115/icone18-29184.
Testo completoAbstract (sommario):
Bonner Spheres neutron spectrometer has been widely applied as neutron dosimeter, however the derivation of neutron energy spectrum from its measurement data is still a significantly difficult task. This unfolding problem is proved to be ill-posed, under-determined and have no exact solution. Two major require of the unfolding methods are accuracy and stability. Most unfolding methods try to search the solution that best fit the measurement data and the response function. As a universal optimization tool Genetic Algorithm shows its potential to solve this kind of problem. Through gene operation of every generation, GA could find the global optimal among the searching space. A new fitness function which contains a distance part and a penalty part was constructed in this research. The distance part is the square distance between the individual and the measurement data. The penalty part which is a function associated with the continuity of individual is used to avoid intensively change of unfolded data. Five classical neutron spectra were chosen as benchmark input spectra. The product of the benchmark spectra and the response function played as input measurement data of the unfolding program. The unfolded results showed good agreement with the real ones. The measurement data could be well reproduced by the unfolded results though the results had some difference with the real spectra.
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Arena, Felice, e C. Guedes Soares. "On Sequence of High Waves in Nonlinear Groups". In ASME 2008 27th International Conference on Offshore Mechanics and Arctic Engineering. ASMEDC, 2008. http://dx.doi.org/10.1115/omae2008-57889.
Testo completoAbstract (sommario):
The structure of wave groups in time domain depends upon the spectrum. For narrow-band spectra, if a wave with a very large height H occurs, the waves that precede and follow the highest one have height (H′ and H″ respectively) very close to H. For real spectra, the difference between H and either H′ or H″ depends on the bandwidth of the spectrum: it increases as larger is the spectrum. For bimodal spectra, the authors have shown [1] that the wave groups are strongly modified and they are function of the energy associated to the swell and to the wind wave components, as well as of the distance between the two peaks. This paper analyzes the structure of the succession of three waves, given by the high waves and the two that come before and after the highest one, in time domain. The results are analyzed, up to the second-order, for wind wave unimodal and for bimodal spectra, by comparing the height H with H′ and H″.
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Wang, Yu, Sufen Li, Yonggang Huo, Jianqing Yang e Quanhu Zhang. "Explainable Neural Network Algorithm for Rapid Radionuclide Identification Under Low Count Gamma-Ray Spectrum Data". In 2022 29th International Conference on Nuclear Engineering. American Society of Mechanical Engineers, 2022. http://dx.doi.org/10.1115/icone29-92829.
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Abstract Real-time and automatic radioisotope identification using gamma spectrum is an important issue in the field of nuclear safety. It is widely used in vehicle mounted radioisotope monitoring, Marine radioisotope monitoring and nuclear decommissioning verification scenarios. At present, the focus of radionuclide identification is fast and stable recognition under low count conditions. In this paper, a radionuclide recognition method based explainable artificial neural network is proposed, and a synthetic gamma spectrum data set is created. The data set contains gamma-ray spectra of 12 different types of radionuclides, which were obtained by Geant4 Monte Carlo simulation software and gaussian broadening of the detector. Data Augmentation was achieved by simulating gamma spectra at different measuring times, different measuring distances and different ambient temperatures. The training results of the neural network optimized by hyperparameter show that it has a high accuracy on the test set with shorter measurement time, longer measurement distance and larger energy spectrum drift range, which provides a method for rapid identification of nuclides in the case of low count. Using t-SNE dimension reduction technology, the twelve dimensions data output by the neural network is reduced to two dimensions for feature visualization, which vividly explains and verifies the recognition results of neural network.
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Bocharova, Irina E., Boris D. Kudryashov e Vitaly Skachek. "Euclidean Distance Spectra of Irregular NB LDPC Coded QAM Signals with Optimized Mappings". In 2021 IEEE International Symposium on Information Theory (ISIT). IEEE, 2021. http://dx.doi.org/10.1109/isit45174.2021.9518126.
Testo completoRapporti di organizzazioni sul tema "Distance spectra"
1
Alchanatis, Victor, Stephen W. Searcy, Moshe Meron, W. Lee, G. Y. Li e A. Ben Porath. Prediction of Nitrogen Stress Using Reflectance Techniques. United States Department of Agriculture, novembre 2001. http://dx.doi.org/10.32747/2001.7580664.bard.
Testo completoAbstract (sommario):
Commercial agriculture has come under increasing pressure to reduce nitrogen fertilizer inputs in order to minimize potential nonpoint source pollution of ground and surface waters. This has resulted in increased interest in site specific fertilizer management. One way to solve pollution problems would be to determine crop nutrient needs in real time, using remote detection, and regulating fertilizer dispensed by an applicator. By detecting actual plant needs, only the additional nitrogen necessary to optimize production would be supplied. This research aimed to develop techniques for real time assessment of nitrogen status of corn using a mobile sensor with the potential to regulate nitrogen application based on data from that sensor. Specifically, the research first attempted to determine the system parameters necessary to optimize reflectance spectra of corn plants as a function of growth stage, chlorophyll and nitrogen status. In addition to that, an adaptable, multispectral sensor and the signal processing algorithm to provide real time, in-field assessment of corn nitrogen status was developed. Spectral characteristics of corn leaves reflectance were investigated in order to estimate the nitrogen status of the plants, using a commercial laboratory spectrometer. Statistical models relating leaf N and reflectance spectra were developed for both greenhouse and field plots. A basis was established for assessing nitrogen status using spectral reflectance from plant canopies. The combined effect of variety and N treatment was studied by measuring the reflectance of three varieties of different leaf characteristic color and five different N treatments. The variety effect on the reflectance at 552 nm was not significant (a = 0.01), while canonical discriminant analysis showed promising results for distinguishing different variety and N treatment, using spectral reflectance. Ambient illumination was found inappropriate for reliable, one-beam spectral reflectance measurement of the plants canopy due to the strong spectral lines of sunlight. Therefore, artificial light was consequently used. For in-field N status measurement, a dark chamber was constructed, to include the sensor, along with artificial illumination. Two different approaches were tested (i) use of spatially scattered artificial light, and (ii) use of collimated artificial light beam. It was found that the collimated beam along with a proper design of the sensor-beam geometry yielded the best results in terms of reducing the noise due to variable background, and maintaining the same distance from the sensor to the sample point of the canopy. A multispectral sensor assembly, based on a linear variable filter was designed, constructed and tested. The sensor assembly combined two sensors to cover the range of 400 to 1100 nm, a mounting frame, and a field data acquisition system. Using the mobile dark chamber and the developed sensor, as well as an off-the-shelf sensor, in- field nitrogen status of the plants canopy was measured. Statistical analysis of the acquired in-field data showed that the nitrogen status of the com leaves can be predicted with a SEP (Standard Error of Prediction) of 0.27%. The stage of maturity of the crop affected the relationship between the reflectance spectrum and the nitrogen status of the leaves. Specifically, the best prediction results were obtained when a separate model was used for each maturity stage. In-field assessment of the nitrogen status of corn leaves was successfully carried out by non contact measurement of the reflectance spectrum. This technology is now mature to be incorporated in field implements for on-line control of fertilizer application.
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Jay. L51710 Active Noise Silencing. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), gennaio 1994. http://dx.doi.org/10.55274/r0010333.
Testo completoAbstract (sommario):
Many natural gas compressor stations which were previously located away from residential areas are now being encroached upon by surrounding building developments. Furthermore, an increased awareness of community noise issues has proved to be the impetus for investigating and developing more effective noise control methods and treatments for natural gas compressor facilities. This project investigates the feasibility of applying Active Noise Cancellation (ANC) to the exhaust of a large, internal-combustion reciprocating type engine. Large reciprocating internal combustion engines pose significant challenges for the noise control engineer. In the case of the engines employed at Tennessee Gas Pipeline Company Compressor Station 229, these engines radiate extremely low frequency exhaust noise into the surrounding environs. These engines produce discrete frequencies in the exhaust spectra with a particularly strong component at 26.5 Hz, which corresponds to the fundamental firing frequency (the 5.0 rotational order) of the engine; significant attenuation of the raw exhaust noise can be particularly difficult due to the sound power and spectral content. Traditional methods would necessitate a very large silencer in order to realize improved attenuation of the exhaust noise, relative to the existing silencer. Measurements were conducted at the error microphone location, at 1.0 meter from the exhaust outlet and at the property line. At a distance of 1.0 meter the WNCT integrated active / passive silencer yielded 84.5 dBA (92.3 dBL) while the original equipment silencer yielded 92.7 dBA (98.8 dBL). Band-limited (DC - 200 Hz) measurements were taken at the error microphone location; control off (WNCT passive - only): 109.8 dBL overall, 107.7 dBL 26.5 Hz component. With control on (WNCT active + passive) at the same position overall noise was 99.7 dBL with the 26.5 Hz component reading 89.1 dBL. Far-field A-weighted reductions were inconclusive due to the presence of other contributing noise sources possessing similar noise characteristics. Flow resistance measurements indicated that back pressure had been reduced by 95% relative to the original equipment silencer through the use of the integrated WNCT active / passive silencer.
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Chapman, Martin C., G. A. Bollinger e Matthew S. Sibol. Modeling Delay-Fired Explosion Spectra and Source Function Deconvolution at Regional Distances. Fort Belvoir, VA: Defense Technical Information Center, settembre 1992. http://dx.doi.org/10.21236/ada260232.
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White, H. P., W. Chen e S G Leblanc. Satellite observations for detection of dust from mining activities in a caribou habitat, Northwest Territories and Nunavut. Natural Resources Canada/CMSS/Information Management, 2022. http://dx.doi.org/10.4095/330548.
Testo completoAbstract (sommario):
Diamond mining via open pit mining has been ongoing within the Tlicho region of the Northwest Territories for several decades, which includes the habitat range of the Bathurst Caribou Herd. This has led to the importance of quantitative characterization of the Zone Of Influence (ZOI), where resource development activities may be influencing the natural behaviour of the caribou herd in the tundra environment. As part of better defining and understanding the ZOI in this region, an initiative to evaluate the potential of detecting and mapping mine waste rock dust in the surrounding environment is explored. This dust has been shown to coat foliage near roads, influencing the acidity levels of the surficial soil layer and impacting the foliage distribution. To this end, field spectrometry was acquired at various distances from road ways. Satellite imagery from the Proba-1 CHRIS hyperspectral sensor and the multi-spectral Sentinel-2a system were also acquired of the region. This presentation presents the initial spectral analysis pursued to evaluate the potential to remotely spectrally detect waste rock dust material used in road construction in the surrounding tundra vegetation. Initial analysis of the Proba-1 CHRIS hyperspectral imagery shows spectral indicators of fugitive dust and waste rock easily detects the road and suggests detectable dust concentration above ambient up to a distance of under 1km from the road.
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Zilberman, Mark. Shouldn’t Doppler 'De-boosting' be accounted for in calculations of intrinsic luminosity of Standard Candles? Intellectual Archive, settembre 2021. http://dx.doi.org/10.32370/iaj.2569.
Testo completoAbstract (sommario):
"Doppler boosting / de-boosting" is a well-known relativistic effect that alters the apparent luminosity of approaching/receding radiation sources. "Doppler boosting" alters the apparent luminosity of approaching light sources to appear brighter, while "Doppler de-boosting" alters the apparent luminosity of receding light sources to appear fainter. While "Doppler boosting / de-boosting" has been successfully accounted for and observed in relativistic jets of AGN, double white dwarfs, in search of exoplanets and stars in binary systems it was ignored in the establishment of Standard Candles for cosmological distances. A Standard Candle adjustment appears necessary for "Doppler de-boosting" for high Z, otherwise we would incorrectly assume that Standard Candles appear dimmer, not because of "Doppler de-boosting" but because of the excessive distance, which would affect the entire Standard Candles ladder at cosmological distances. The ratio between apparent (L) and intrinsic (Lo) luminosities as a function of redshift Z and spectral index α is given by the formula ℳ(Z) = L/Lo=(Z+1)^(α-3) and for Type Ia supernova as ℳ(Z) = L/Lo=(Z+1)^(-2). These formulas are obtained within the framework of Special Relativity and may require adjustments within the General Relativity framework.
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Si, Hongjun, Saburoh Midorikawa e Tadahiro Kishida. Development of NGA-Sub Ground-Motion Model of 5%-Damped Pseudo-Spectral Acceleration Based on Database for Subduction Earthquakes in Japan. Pacific Earthquake Engineering Research Center, University of California, Berkeley, CA, dicembre 2020. http://dx.doi.org/10.55461/lien3652.
Testo completoAbstract (sommario):
Presented within is an empirical ground-motion model (GMM) for subduction-zone earthquakesin Japan. The model is based on the extensive and comprehensive subduction database of Japanese earthquakes by the Pacific Engineering Research Center (PEER). It considers RotD50 horizontal components of peak ground acceleration (PGA), peak ground velocity (PGV), and 5%-damped elastic pseudo-absolute acceleration response spectral ordinates (PSA) at the selected periods ranging from 0.01 to 10 sec. The model includes terms and predictor variables considering tectonic setting (i.e., interplate and intraslab), hypocentral depths (D), magnitude scaling, distance attenuation, and site response. The magnitude scaling derived in this study is well constrained by the data observed during the large-magnitude interface events in Japan (i.e., the 2003 Tokachi-Oki and 2011 Tohoku earthquakes) for different periods. The developed ground-motion prediction equation (GMPE) covers subduction-zone earthquakes that have occurred in Japan for magnitudes ranging from 5.5 to as large as 9.1, with distances less than 300 km from the source.
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Zilberman, Mark. “Doppler de-boosting” and the observation of “Standard candles” in cosmology. Intellectual Archive, luglio 2021. http://dx.doi.org/10.32370/iaj.2549.
Testo completoAbstract (sommario):
“Doppler boosting” is a well-known relativistic effect that alters the apparent luminosity of approaching radiation sources. “Doppler de-boosting” is the name of relativistic effect observed for receding light sources (e.g. relativistic jets of active galactic nuclei and gamma-ray bursts). “Doppler boosting” changes the apparent luminosity of approaching light sources to appear brighter, while “Doppler de-boosting” causes the apparent luminosity of receding light sources to appear fainter. While “Doppler de-boosting” has been successfully accounted for and observed in relativistic jets of AGN, it was ignored in the establishment of Standard candles for cosmological distances. A Standard candle adjustment of an Z>0.1 is necessary for “Doppler de-boosting”, otherwise we would incorrectly assume that Standard Candles appear dimmer not because of “Doppler de-boosting” but because of the excessive distance, which would affect the entire Standard Candles ladder at cosmological distances. The ratio between apparent (L) and intrinsic (Lo) luminosities as a function of the redshift Z and spectral index α is given by the formula ℳ(Z) = L/Lo=(Z+1)α -3 and for Type Ia supernova appears as ℳ(Z) = L/Lo=(Z+1)-2. “Doppler de-boosting” may also explain the anomalously low luminosity of objects with a high Z without the introduction of an accelerated expansion of the Universe and Dark Energy.
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Zilberman, Mark. PREPRINT. “Doppler de-boosting” and the observation of “Standard candles” in cosmology. Intellectual Archive, giugno 2021. http://dx.doi.org/10.32370/ia_2021_06_23.
Testo completoAbstract (sommario):
PREPRINT. “Doppler boosting” is a well-known relativistic effect that alters the apparent luminosity of approaching radiation sources. “Doppler de-boosting” is the term of the same relativistic effect observed for receding light sources (e.g.relativistic jets of active galactic nuclei and gamma-ray bursts). “Doppler boosting” alters the apparent luminosity of approaching light sources to appear brighter, while “Doppler de-boosting” alters the apparent luminosity of receding light sources to appear fainter. While “Doppler de-boosting” has been successfully accounted for and observed in relativistic jets of AGN, it was ignored in the establishment of Standard candles for cosmological distances. A Standard candle adjustment of Z>0.1 is necessary for “Doppler de-boosting”, otherwise we would incorrectly assume that Standard Candles appear dimmer, not because of “Doppler de-boosting” but because of the excessive distance, which would affect the entire Standard Candles ladder at cosmological distances. The ratio between apparent (L) and intrinsic (Lo) luminosities as a function of the redshift Z and spectral index α is given by the formula ℳ(Z) =L/Lo=(Z+1)^(α-3) and for Type Ia supernova appears as ℳ(Z)=L/Lo=(Z+1)^(-2). “Doppler de-boosting” may also explain the anomalously low luminosity of objects with a high Z without the introduction of an accelerated expansion of the Universe and Dark Energy.
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Zilberman, Mark. "Doppler De-boosting" and the Observation of "Standard Candles" in Cosmology. Intellectual Archive, luglio 2021. http://dx.doi.org/10.32370/iaj.2552.
Testo completoAbstract (sommario):
“Doppler boosting” is a well-known relativistic effect that alters the apparent luminosity of approaching radiation sources. “Doppler de-boosting” is the same relativistic effect observed but for receding light sources (e.g. relativistic jets of AGN and GRB). “Doppler boosting” alters the apparent luminosity of approaching light sources to appear brighter, while “Doppler de-boosting” alters the apparent luminosity of receding light sources to appear fainter. While “Doppler de-boosting” has been successfully accounted for and observed in relativistic jets of AGN, it was ignored in the establishment of Standard candles for cosmological distances. A Standard Candle adjustment of Z>0.1 is necessary for “Doppler de-boosting”, otherwise we would incorrectly assume that Standard Candles appear dimmer, not because of “Doppler de-boosting” but because of the excessive distance, which would affect the entire Standard Candles ladder at cosmological distances. The ratio between apparent (L) and intrinsic (Lo) luminosities as a function of the redshift Z and spectral index α is given by the formula ℳ(Z) = L/Lo=(Z+1)α -3 and for Type Ia supernova appears as ℳ(Z) = L/Lo=(Z+1)-2. “Doppler de-boosting” may also explain the anomalously low luminosity of objects with a high Z without the introduction of an accelerated expansion of the Universe and Dark Energy.
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Keahava, N. Distance Metrics and Band Selection in Hyperspectral Processing with Applications to Material Identification and Spectral Libraries. Fort Belvoir, VA: Defense Technical Information Center, dicembre 2002. http://dx.doi.org/10.21236/ada409023.
Testo completo