Relevant bibliographies by topics / Spectra

Academic literature on the topic 'Spectra'

Author: Grafiati
Published: 4 June 2021
Last updated: 1 August 2024

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Journal articles on the topic "Spectra"

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Ibrahim, Amr, Adriana Predoi-Cross, and Chad Povey. "Handling techniques for channel spectra in synchrotron-based Fourier transform spectra." Canadian Journal of Physics 91, no. 11 (November 2013): 910–23. http://dx.doi.org/10.1139/cjp-2013-0050.

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Recently, the high radiance of synchrotron sources has been used to enhance FTIR spectrometer performance. However, excessive channel spectra when synchrotron sources are used degrade the quality of retrieved spectral parameters. We have investigated seven different techniques for handling channel spectra. These techniques were used to reduce channel spectra for a test group of seven samples of CO2 mixed with air recorded using the synchrotron source at the Canadian Light Source. The increases in signal to noise ratio (SNR) of spectra handled with each technique were calculated. SNR results showed that transmission spectra, produced using synthetic background spectra with simulated channel spectra, achieved the highest SNR improvement. However, when the spectra groups were fitted using a nonlinear least square fit algorithm, the technique using channel spectra fitting produced the smallest fitting residual. Moreover, the retrieved intensities and air broadening coefficients of 21 spectral lines showed that the spectral fitting technique produced the most accurate values as compared to the HITRAN 2008 database (Rothman et al. J. Quant. Spectrosc. Radiat. Transfer, 110, 533 (2009)). Although the spectral fitting technique was accurate in retrieving spectral line parameters, applying the technique at wider spectral ranges reduced this accuracy.
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Chauhan, H., and B. Krishna Mohan. "Effectiveness of Spectral Similarity Measures to Develop Precise Crop Spectra for Hyperspectral Data Analysis." ISPRS Annals of Photogrammetry, Remote Sensing and Spatial Information Sciences II-8 (November 27, 2014): 83–90. http://dx.doi.org/10.5194/isprsannals-ii-8-83-2014.

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The present study was undertaken with the objective to check effectiveness of spectral similarity measures to develop precise crop spectra from the collected hyperspectral field spectra. In Multispectral and Hyperspectral remote sensing, classification of pixels is obtained by statistical comparison (by means of spectral similarity) of known field or library spectra to unknown image spectra. Though these algorithms are readily used, little emphasis has been placed on use of various spectral similarity measures to select precise crop spectra from the set of field spectra. Conventionally crop spectra are developed after rejecting outliers based only on broad-spectrum analysis. Here a successful attempt has been made to develop precise crop spectra based on spectral similarity. As unevaluated data usage leads to uncertainty in the image classification, it is very crucial to evaluate the data. Hence, notwithstanding the conventional method, the data precision has been performed effectively to serve the purpose of the present research work. The effectiveness of developed precise field spectra was evaluated by spectral discrimination measures and found higher discrimination values compared to spectra developed conventionally. Overall classification accuracy for the image classified by field spectra selected conventionally is 51.89% and 75.47% for the image classified by field spectra selected precisely based on spectral similarity. KHAT values are 0.37, 0.62 and Z values are 2.77, 9.59 for image classified using conventional and precise field spectra respectively. Reasonable higher classification accuracy, KHAT and Z values shows the possibility of a new approach for field spectra selection based on spectral similarity measure.
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Ivanov, Valentin D., Lodovico Coccato, Mark J. Neeser, Fernando Selman, Alessandro Pizzella, Elena Dalla Bontà, Enrico M. Corsini, and Lorenzo Morelli. "MUSE library of stellar spectra." Astronomy & Astrophysics 629 (September 2019): A100. http://dx.doi.org/10.1051/0004-6361/201936178.

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Context. Empirical stellar spectral libraries have applications in both extragalactic and stellar studies, and they confer an advantage over theoretical libraries because they naturally include all relevant chemical species and physical processes. In recent years we have seen a stream of new sets of high-quality spectra, but increasing the spectral resolution and widening the wavelength coverage means resorting to multi-order echelle spectrographs. Assembling the spectra from many pieces results in lower fidelity of their shapes. Aims. We aim to offer the community a library of high-signal-to-noise spectra with reliable continuum shapes. Furthermore, the use of an integral field unit (IFU) alleviates the issue of slit losses. Methods. Our library was built with the MUSE (Multi-Unit Spectroscopic Explorer) IFU instrument. We obtained spectra over nearly the entire visual band (λ ∼ 4800–9300 Å). Results. We assembled a library of 35 high-quality MUSE spectra for a subset of the stars from the X-shooter Spectral Library. We verified the continuum shape of these spectra with synthetic broadband colors derived from the spectra. We also report some spectral indices from the Lick system, derived from the new observations. Conclusions. We offer a high-fidelity set of stellar spectra covering the Hertzsprung-Russell diagram. These can be used for both extragalactic and stellar studies and demonstrate that the IFUs are excellent tools for building reliable spectral libraries.
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Zhou, Qian, Zhiyong Zou, and Lin Han. "Deep Learning-Based Spectrum Reconstruction Method for Raman Spectroscopy." Coatings 12, no. 8 (August 22, 2022): 1229. http://dx.doi.org/10.3390/coatings12081229.

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Raman spectroscopy, measured by a Raman spectrometer, is usually disturbed by the instrument response function and noise, which leads to certain measurement error and further affects the accuracy of substance identification. In this paper, we propose a spectral reconstruction method which combines the existing maximum a posteriori (MAP) method and deep learning (DL) to recover the degraded Raman spectrum. The proposed method first employs the MAP method to reconstruct the measured Raman spectra, so as to obtain preliminary estimated Raman spectra. Then, a convolutional neural network (CNN) is trained by using the preliminary estimated Raman spectra and the real Raman spectra to learn the mapping from the preliminary estimated Raman spectra to the real Raman spectra, so as to achieve a better spectral reconstruction effect than merely using the MAP method or a CNN. To prove the effectiveness of the proposed spectral reconstruction method, we employed the proposed method and some traditional spectral reconstruction methods to reconstruct the simulated and measured Raman spectra, respectively. The experimental results show that compared with traditional methods, the estimated Raman spectra reconstructed by the proposed method are closer to the real Raman spectra.
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Chen, Li, Wee Chew, and Marc Garland. "Spectral Pattern Recognition of in Situ FT-IR Spectroscopic Reaction Data Using Minimization of Entropy and Spectral Similarity (MESS): Application to the Homogeneous Rhodium Catalyzed Hydroformylation of Isoprene." Applied Spectroscopy 57, no. 5 (May 2003): 491–98. http://dx.doi.org/10.1366/000370203321666489.

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An improved algorithm using minimization of entropy and spectral similarity (MESS) was tested to recover pure component spectra from in situ experimental Fourier transform infrared (FT-IR) reaction spectral data, which were collected from a homogeneous rhodium catalyzed hydroformylation of isoprene. The experimental spectra are complicated and highly overlapping because of the presence of multiple intermediate products in this reaction system. The traditional entropy minimization method fails to resolve real reaction mixture spectra, but MESS can successfully reconstruct pure component spectra of unknown intermediate products for real reaction systems by the addition of minimization of spectral similarity. The quantitative measure of spectral similarity between two spectra was given by their inner products. The results indicate that MESS is a stable and useful algorithm for spectral pattern recognition of highly overlapped experimental reaction spectra. Comparison is also made between MESS, entropy minimization, simple-to-use interactive self-modeling mixture analysis (SIMPLISMA), interactive principle component analysis (IPCA), and orthogonal projection approach–alternating least squares (OPA-ALS).
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Zhang, Xiaodian, Kun Gao, Junwei Wang, Pengyu Wang, Zibo Hu, Zhijia Yang, Xiaobin Zhao, and Wei Li. "Target Detection Adapting to Spectral Variability in Multi-Temporal Hyperspectral Images Using Implicit Contrastive Learning." Remote Sensing 16, no. 4 (February 18, 2024): 718. http://dx.doi.org/10.3390/rs16040718.

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Hyperspectral target detection (HTD) is a crucial aspect of remote sensing applications, aiming to identify targets in hyperspectral images (HSIs) based on their known prior spectral signatures. However, the spectral variability resulting from various imaging conditions in multi-temporal hyperspectral images poses a challenge to both classical and deep learning (DL) methods. To overcome the limitations imposed by spectral variability, an implicit contrastive learning-based target detector (ICLTD) is proposed to exploit in-scene spectra in an unsupervised way. First, only prior spectra are utilized for explicit supervision, while an implicit contrastive learning module (ICLM) is designed to normalize the feature distributions of prior and in-scene spectra. This paper theoretically demonstrates that the ICLM can transfer the gradients from prior spectral features to those of in-scene spectra based on their feature similarities and differences. Because of transferred gradient signals, the ICLTD is regularized to extract similar representations for the prior and in-scene target spectra, while augmenting feature differences between the target and background spectra. Additionally, a local spectral similarity constraint (LSSC) is proposed to enhance the capability of scene adaptation by leveraging the spectral similarities among in-scene targets. To validate the performance of the ICLTD under spectral variability, multi-temporal HSIs captured under various imaging conditions are collected to generate prior spectra and in-scene spectra. Comparative evaluations against several DL detectors and classical methods reveal the superior performance of the ICLTD in achieving a balance between target detectability and background suppressibility under spectral variability.
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Feng, Wei Bin, Bin Yang, Hai Jing Cao, and Xing Ye Ni. "Study on Wave Spectra in South Coastal Waters of Jiangsu." Applied Mechanics and Materials 212-213 (October 2012): 193–200. http://dx.doi.org/10.4028/www.scientific.net/amm.212-213.193.

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The paper examined the spectral characteristics of shallow water waves, which was based on the wave data collected along the south coast of Jiangsu. It proposes a tentative spectra model which can work better than Joint North Sea Wave Project (JONSWAP)spectra. Both of the value of tentative spectral parameters (α and γ) increase with significant wave height and spectral peak frequency. According to a regression analysis, empirical equations are achieved, which is related to the parameters with significant wave height and spectral peak frequency. The study shows that the measured wave spectra can be represented by tentative spectra, and the fitting results in high-frequency tail of tentative spectra are better than that of JONSWAP spectrum with modified parameters.
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Sun, Yan, Wensheng Cai, and Xueguang Shao. "Chemometrics: An Excavator in Temperature-Dependent Near-Infrared Spectroscopy." Molecules 27, no. 2 (January 11, 2022): 452. http://dx.doi.org/10.3390/molecules27020452.

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Temperature-dependent near-infrared (NIR) spectroscopy has been developed and taken as a powerful technique for analyzing the structure of water and the interactions in aqueous systems. Due to the overlapping of the peaks in NIR spectra, it is difficult to obtain the spectral features showing the structures and interactions. Chemometrics, therefore, is adopted to improve the spectral resolution and extract spectral information from the temperature-dependent NIR spectra for structural and quantitative analysis. In this review, works on chemometric studies for analyzing temperature-dependent NIR spectra were summarized. The temperature-induced spectral features of water structures can be extracted from the spectra with the help of chemometrics. Using the spectral variation of water with the temperature, the structural changes of small molecules, proteins, thermo-responsive polymers, and their interactions with water in aqueous solutions can be demonstrated. Furthermore, quantitative models between the spectra and the temperature or concentration can be established using the spectral variations of water and applied to determine the compositions in aqueous mixtures.
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Dotsenko, M. A. "ABSORPTION AND LUMINESCENCE PROPERTIES OF ACID AND SALT FORMS OF MONONUCLEOTIDES, THEIR COMPONENTS AND COMPLEXES WITH D-MANNITOL AT ROOM TEMPERATURE." Biotechnologia Acta 17, no. 2 (April 30, 2024): 36–37. http://dx.doi.org/10.15407/biotech17.02.036.

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Aim. The aim of this work was to analyze and compare spectral properties of aqueous nucleotide solutions in conditions close to biological systems. We studied the absorption and luminescence (Ex and Em fluorescence and Em phosphorescence) of monoribonucleotides, their disodium salts, bases and nucleosides, and mixes with D-mannitol dissolved in water at room temperature. Methods. There were measured absorbance spectra using a Specord 210plus instrument and fluorescence excitation and emission and phosphorescence spectra using Horiba Fluoro Max 4+ instruments. Results. There were obtained the absorption, excitation, and luminescence spectra of aqueous solutions 1 mg/ml of nucleotides, their components, and mixtures with mannitol (in ratio 1:4). We observed a change in the ratio between the peaks of the spectra of acidic and salt forms of nucleotides. Conclusions. The observations confirmed that nucleotides, nucleosides, and nucleic acid bases exhibit luminescence at room temperature, which might be useful information for further research in this area. In addition, a comparative analysis of the spectra showed possible interactions between nucleotide molecules and mannitol.
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Hofstraat, J. W., and M. J. Latuhihin. "Correction of Fluorescence Spectra." Applied Spectroscopy 48, no. 4 (April 1994): 436–47. http://dx.doi.org/10.1366/000370294775269027.

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Several methods that can be applied to remove wavelength-dependent instrumental effects from fluorescence emission and excitation spectra have been investigated. Removal of such artifacts is necessary for the comparison of spectra that have been obtained on different instruments. Without correction, spectral line positions and relative intensities will be instrument-determined to a great extent. Furthermore, the application of adequate correction procedures provides excitation spectra which can be directly compared to absorption spectra; comparison of corrected excitation spectra and absorption spectra can be used to interpret the efficiency and pathways of radiative processes. Finally, corrected reflection spectra can be obtained, which can be directly transformed into absorption spectra and are useful for remote sensing applications. The methods that have been studied for the correction of emission spectra are the application of a standard lamp with calibrated spectral output and the use of fluorescence standards. The standards are a series of luminescent phosphors in polymer films and a solution of quinine sulfate dihydrate in perchloric acid, all provided with certified spectral emission values. For correction of excitation spectra, a quantum counter was applied. Several quantum counters were investigated. The best results were obtained for application of a mixture of the dyes basic blue and HITC, which provided good correction for the wavelength range 250 to 820 nm. No good quantum counters have been reported thus far for this (large) wavelength range. Correction for wavelength dependence of the excitation optics was realized by measurement of the excitation light intensity at the sample position and at the reference position with a Si photodiode. Correction factors for the excitation spectra were checked with a number of reference materials. Attention has also been paid to polarization-dependent effects that may occur in fluorescence spectra. The application of correction procedures was demonstrated for phytoplankton fluorescence spectra.
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Dissertations / Theses on the topic "Spectra"

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Rozario, Hoimonti Immaculata. "Spectroscopic study of acetylene and hydrogen cyanide." Thesis, Lethbridge, Alta. : University of Lethbridge, Dept. of Physics and Astronomy, c2012, 2012. http://hdl.handle.net/10133/3415.

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High-resolution molecular spectroscopy has been used to study acetylene line parameters and emission spectra of hydrogen cyanide. All acetylene spectra were recorded in our laboratory at the University of Lethbridge using a 3-channel tuneable diode laser spectrometer. N2-broadened line widths and N2-pressure induced line shifts have been measured for transitions in the v1+v3 band of acetylene at seven temperatures in the range 213–333K to obtain the temperature dependences of broadening and shift coefficients. The Voigt and hard-collision line profile models were used to retrieve the line parameters. The line-broadening and line-shift coefficients as well as their temperature-dependent parameters have been also evaluated theoretically, in the frame work of a semi-classical approach based on an exponential representation of the scattering operator, an intermolecular potential composed of electrostatic quadrupole–quadrupole and pairwise atom–atom interactions as well as on exact trajectories driven by an effective isotropic potential. The experimental results for both N2-broadening and shifting show good agreement with the theoretical results. We have studied the line intensities of the 1νl20←0νl20 band system from the HCN emission spectrum. The infrared emission spectrum of H12C14N was measured at the Justus-Liebig University, Giessen, Germany. The emission spectrum was analyzed with the spectrum analysis software Symath running using Mathematica as a platform. This approach allowed us to retrieve information on band intensity parameters.
viii, 112 leaves : ill. ; 29 cm
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Bandeira, Nuno Filipe Cabrita. "Spectral networks algorithms for de novo interpretation of tandem mass spectra." Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2007. http://wwwlib.umi.com/cr/ucsd/fullcit?p3274510.

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Thesis (Ph. D.)--University of California, San Diego, 2007.
Title from first page of PDF file (viewed October 2, 2007). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 141-152).
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Harvey, Pierre Dominique. "Applications of vibrational spectroscopy and NMR spin-lattice relaxation time measurements to organometallic and organic molecular crystals." Thesis, McGill University, 1985. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=73986.

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Strömwall, Joakim. "Staggered Ladder Spectra." Thesis, Karlstads universitet, Fakulteten för teknik- och naturvetenskap, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-13872.

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Barnes, David James. "Rational Equivariant Spectra." Thesis, University of Sheffield, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.486771.

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Al-Doujan, Fawwaz Awwad. "Spectra of graphs." Thesis, University of East Anglia, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.306195.

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Angeltveit, Vigleik. "Noncommutative ring spectra." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/34549.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mathematics, 2006.
Includes bibliographical references (p. 87-91).
Let A be an Ax ring spectrum. We give an explicit construction of topological Hochschild homology and cohomology of A using the Stasheff associahedra and another family of polyhedra called cyclohedra. Using this construction we can then study how THH(A) varies over the moduli space of AO structures on A, a problem which seems largely intractable using strictly associative replacements of A. We study how topological Hochschild cohomology of any 2-periodic Morava K-theory varies over the moduli space of AO structures and show that in the generic case, when a certain matrix describing the multiplication is invertible, the result is the corresponding Morava E-theory. If this matrix is not invertible, the result is some extension of Morava E-theory, and exactly which extension we get depends on the AO structure. To make sense of our constructions, we first set up a general framework for enriching a subcategory of the category of noncommutative sets over a category C using products of the objects of a non-E operad P in C. By viewing the simplicial category as a subcategory of the category of noncommutative sets in two different ways, we obtain two generalizations of simplicial objects.
(cont.) For the operad given by the Stasheff associahedra we obtain a model for the 2-sided bar construction in the first case and the cyclic bar and cobar construction in the second case. Using either the associahedra or the cyclohedra in place of the geometric simplices we can define the geometric realization of these objects.
by Vigleik Angeltveit.
Ph.D.
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Browne, Sarah Louise. "E-theory spectra." Thesis, University of Sheffield, 2017. http://etheses.whiterose.ac.uk/17812/.

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This thesis combines the fields of functional analysis and topology. $C^\ast$-algebras are analytic objects used in non-commutative geometry and in particular we consider an invariant of them, namely $E$-theory. $E$-theory is a sequence of abelian groups defined in terms of homotopy classes of morphisms of $C^\ast$-algebras. It is a bivariant functor from the category where objects are $C^\ast$-algebras and arrows are $\ast$-homomorphisms to the category where objects are abelian groups and arrows are group homomorphisms. In particular, $E$-theory is a cohomology theory in its first variable and a homology theory in its second variable. We prove in the case of real graded $C^\ast$-algebras that $E$-theory has $8$-fold periodicity. Further we create a spectrum for $E$-theory. More precisely, we use the notion of quasi-topological spaces and form a quasi-spectrum, that is a sequence of based quasi-topological spaces with specific structure maps. We consider actions of the orthogonal group and we obtain a orthogonal quasi-spectrum which we prove has a smash product structure using the categorical framework. Then we obtain stable homotopy groups which give us $E$-theory. Finally, we combine these ideas and a relation between $E$-theory and $K$-theory to obtain connections of the $E$-theory orthogonal quasi-spectrum to $K$-theory and $K$-homology orthogonal quasi-spectra.
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Ajohani, Maha. "SPECTRAL PHASOR ANALYSIS ON ABSORBANCE SPECTRA FOR QUANTIFYING THE CONTENT OF DYE MIXTURES." Miami University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=miami1464191406.

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Suzuki, Nao. "Cosmology from quasar spectra." Diss., Connected to a 24 p. preview or request complete full text in PDF format. Access restricted to UC IP addresses, 2005. http://wwwlib.umi.com/cr/ucsd/fullcit?p3189997.

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Thesis (Ph. D.)--University of California, San Diego, 2005.
Title from first page of PDF file (viewed March 7, 2006). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 344-361).
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Books on the topic "Spectra"

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Art World, the Fine Art Gallery (Chennai, India), Gallery Katayun (Kolkata India), and Time & Space for Contemporary Arts (Bangalore, India), eds. Spectra. Bangalore: Gallerie Zen, 2013.

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Museo de Arte Contemporáneo (Panama, Panama), ed. Caribe spectra. Panamá: Museo de Arte Contemporáneo, 2000.

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H, Tipping R., and United States. National Aeronautics and Space Administration., eds. An improved quasistatic line-shape theory: The effect of molecular motion on the line wings. [Washington, D.C: National Aeronautics and Space Administration, 1994.

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Reilly, James P. Free radical and overtone spectroscopy. [Washington, DC: National Aeronautics and Space Administration, 1991.

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Reilly, James P. Free radical and overtone spectroscopy. [Washington, DC: National Aeronautics and Space Administration, 1991.

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Samraj, Adi Da. The spectra suites. New York, NY: Welcome Books, 2006.

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Triebel, Hans. Fractals and Spectra. Basel: Springer Basel, 1997. http://dx.doi.org/10.1007/978-3-0348-0034-1.

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Brouwer, Andries E., and Willem H. Haemers. Spectra of Graphs. New York, NY: Springer New York, 2012. http://dx.doi.org/10.1007/978-1-4614-1939-6.

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Al-Doujan, Fawwaz Awwad. Spectra of graphs. Norwich: University of East Anglia, 1992.

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H, Haemers Willem, and SpringerLink (Online service), eds. Spectra of Graphs. New York, NY: Andries E. Brouwer and Willem H. Haemers, 2012.

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Book chapters on the topic "Spectra"

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Bessell, M. S., B. Barbuy, A. Boesgaard, P. Cottrell, M. Gerbaldi, D. Gray, G. Mathys, et al. "Stellar Spectra (Spectres Stellaires)." In Reports on Astronomy, 283–92. Dordrecht: Springer Netherlands, 1997. http://dx.doi.org/10.1007/978-94-011-5762-9_27.

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McNally, Derek. "Stellar Spectra (Spectres Stellaires)." In Reports on Astronomy, 309–26. Dordrecht: Springer Netherlands, 1991. http://dx.doi.org/10.1007/978-94-011-3364-7_21.

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Salinger, D. L., and J. D. Stegeman. "Spectral synthesis and difference spectra." In Harmonic Analysis, 265–71. Berlin, Heidelberg: Springer Berlin Heidelberg, 1988. http://dx.doi.org/10.1007/bfb0086607.

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Jardine, John F. "Spectra and T-spectra." In Springer Monographs in Mathematics, 337–430. New York, NY: Springer New York, 2015. http://dx.doi.org/10.1007/978-1-4939-2300-7_10.

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Switzer, Robert M. "Spectra." In Algebraic Topology — Homotopy and Homology, 133–51. Berlin, Heidelberg: Springer Berlin Heidelberg, 2002. http://dx.doi.org/10.1007/978-3-642-61923-6_9.

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Civiš, Svatopluk, Ekaterina Zanozina, Adam Pastorek, Petr Kubelík, Martin Ferus, and Ashok Chilukoti. "Spectra." In Atomic Emission Spectra of Neutral Noble Gases in the Infrared Spectral Range, 9–144. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-47352-5_3.

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Gooch, Jan W. "Spectra." In Encyclopedic Dictionary of Polymers, 686. New York, NY: Springer New York, 2011. http://dx.doi.org/10.1007/978-1-4419-6247-8_10964.

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Engleman, Rolf. "Spectra." In Th Thorium, 17–174. Berlin, Heidelberg: Springer Berlin Heidelberg, 1989. http://dx.doi.org/10.1007/978-3-662-07410-7_2.

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Cozzo, Emanuele, Guilherme Ferraz de Arruda, Francisco Aparecido Rodrigues, and Yamir Moreno. "Spectra." In SpringerBriefs in Complexity, 39–53. Cham: Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-319-92255-3_4.

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Cowley, Charles, Wolfgang L. Wiese, Jeffrey Fuhr, and Ludmila A. Kuznetsova. "Spectra." In Allen’s Astrophysical Quantities, 53–93. New York, NY: Springer New York, 2002. http://dx.doi.org/10.1007/978-1-4612-1186-0_4.

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Conference papers on the topic "Spectra"

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Shcherbina, M. P., V. V. Busarev, and S. I. Barabanov. "New reflectance spectra of Main belt asteroids: clarification of taxonomic types and composition of matter." In ASTRONOMY AT THE EPOCH OF MULTIMESSENGER STUDIES. Proceedings of the VAK-2021 conference, Aug 23–28, 2021. Crossref, 2022. http://dx.doi.org/10.51194/vak2021.2022.1.1.094.

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The mineralogy of the surface matter of asteroids can be judged using a qualitative interpretation of the reflection spectraof these bodies. The features of the reflectance spectra (absorption bands) are wide enough for correct interpretation even ata low resolution of the recording device. It should be noted that the number of events of registration of sublimation activityamong primitive asteroids has been increasing recently. The emergence of a temporary exosphere affects the asteroid’sreflection spectrum. The reflection spectra of 12 asteroids of the Main Belt, mainly of primitive type, have been obtainedand analyzed. The aim of the research was to study the influence of the temporal exosphere on the correct determinationof the spectral type of the asteroid. In addition, for asteroid 203 Pompeia, the spectral type has been determined for thefirst time(class C).
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Gutman, William M., William A. Peterson, and Dennis M. Garvey. "Spatial frequency shifts in Fourier transform spectra." In OSA Annual Meeting. Washington, D.C.: Optica Publishing Group, 1992. http://dx.doi.org/10.1364/oam.1992.ftt2.

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High resolution atmospheric transmission spectra collected with a Fourier transform instrument sometimes exhibit small systematic shifts in the apparent positions of spectral features. Although small, these shifts result in line shape distortions such as "S-curving" when, in the data reduction, one spectrum must be divided by another. The origin of the shifting is in small residual angular deviations between the laser reference and measurement beams and the mechanical axis of the spectrometer. Thermal distortion of the instrument resulting from temperature gradients that change from spectrum to spectrum during a data acquisition operation are the source of the angular deviation. The authors typically measure spectra under field conditions by using trailer-mounted instruments. The level of temperature control necessary to eliminate shifting is not possible under these conditions. Strategies must be found to reduce or eliminate the effects during processing. The processing method that is explored here is to measure the relative shift between the individual spectra and then to interpolate one of them to the precise spatial frequency values present in the other prior to point-by-point division. Relatively simple interpolation schemes yield significant reduction of the distortion when applied to simulated data, and smaller but still good reduction when applied to measured spectra.
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Nie, Jinsuo R., Jim Xu, Vladimir Graizer, and Dogan Seber. "Uncertainties in In-Structure Response Spectra Due to Uncertainties in Input Motion Amplitude and Phase Spectra." In ASME 2023 Pressure Vessels & Piping Conference. American Society of Mechanical Engineers, 2023. http://dx.doi.org/10.1115/pvp2023-105307.

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Abstract We concluded in PVP2020-21132 that the four or five time histories in the current practice are not sufficient for estimating stable mean in-structure response spectra (ISRS), therefore a check of their power spectral density functions is necessary. The time histories used in that work were not developed based on typical response spectrum (RS) convergence criteria and did not consider the uncertainties in Fourier amplitude spectra. This paper examines how the uncertainties in both Fourier phase spectra and Fourier amplitude spectra of the input motions resulting from seed time histories and a new RS-matching algorithm affect the uncertainties in ISRS. This study finds that the coefficient of variation in ISRS reached as high as 68%, generally confirming previous results obtained using a different RS-matching algorithm. This level of ISRS variation continues to support our conclusions in PVP2020-21132. Therefore, a check of the power spectral density functions of the multiple input time histories in the current practice is necessary to ensure the estimated mean ISRS would vary on the conservative side, although not as stable as necessarily required for reasonable confidence levels. These results provide the necessary technical bases for consistent technical positions between industry standards and regulatory guide for nuclear power plants.
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Brault, Janes W., and Mark C. Abrams. "DECOMP: A Fourier Transfom Spectra Decomposition Program." In High Resolution Fourier Transform Spectroscopy. Washington, D.C.: Optica Publishing Group, 1989. http://dx.doi.org/10.1364/hrfts.1989.pdp2.

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Current techniques for processing high resolution Fourier transform spectra revolve around interactive graphical display of the spectrum on a computer. The DECOMP spectrum decomposition program is designed explicitly for the reduction of Fourier transform spectra and focuses on reducing a spectrum into a list of line parameters. Basic methods of spectrum manipulation will be demonstrated and a IBM PC - compatible computer will be available for hands-on demonstrations of the process of spectrum analysis. Figures 1 and 2 illustrate the process of background subtraction: in Figure 1 a low resolution spectrum is generated by binning the high resolution spectrum and beneath the spectrum is a background correction function generated by creating a low resolution "minima" spectrum and smoothing the spectrum. The results of the background correction are given in Figure 2. Figure 3 illustrates a common problem in Fourier transform spectroscopy: the finite length of the interferogram introduces "ringing" into the spectrum. Using a filtered fitting routine in DECOMP the ringing can be effectively removed yielding a spectrum illustrated in Figure 4, in which several new spectral features that had been hidden beneath the ringing. An example of the atlas plots that can be generated using DECOMP is given in Figure 5.
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Lucchini, Andrea, Paolo Franchin, and Fabrizio Mollaioli. "A Spectrum-to-Spectrum Method for Calculating Uniform Hazard Floor Response Spectra." In ASME 2017 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/pvp2017-65293.

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In codes’ provisions and design procedures for acceleration-sensitive nonstructural components, seismic demand is commonly defined by means of floor response spectra expressed in terms of pseudo-acceleration. Depending on the considered analysis method, floor response spectra may be derived from floors’ acceleration histories, based on structural response-history analysis, or calculated using a predictive equation from a given input ground motion spectrum. Methods for estimating floor response spectra that are based on the second alternative are commonly called spectrum-to-spectrum methods. The objective of this paper is to briefly review these methods, and to discuss the main assumptions they are based on. Both predictive equations from selected seismic codes and proposals from the literature are included in the review. A new probability-based method, recently developed by the Authors for generating uniform hazard floor response spectra, namely, floor response spectra whose ordinates are characterized by a given target value of the mean annual frequency of being exceeded, is also described. By using this method floor spectra are determined through closed-form equations, given the mean annual frequency of interest, the damping ratio of the spectra, the modal properties of the structure, and three uniform hazard ground spectra. The method is built on a proposal for a probabilistic seismic demand model that relates the ground spectral acceleration with the floor spectral acceleration, and is able to explicitly account for the ground motion variability of the nonstructural response. Results for a case study consisting of a service frame of a visbreaking unit in an oil refinery are presented to show the good predictive accuracy of the method with respect to exact uniform hazard floor response spectra obtained through a standard probabilistic analysis.
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Fullerton, Anne M., and Thomas C. Fu. "Statistics of Greater Sea States." In ASME 2011 30th International Conference on Ocean, Offshore and Arctic Engineering. ASMEDC, 2011. http://dx.doi.org/10.1115/omae2011-49934.

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Accurate representations of seaway statistics are important for physical and computational predictions of ship motions. The spectra that are most typically used in these applications are the Pierson-Moskowitz or Bretschneider. While these spectra are useful for fully developed seas, the larger sea states (Sea State (SS) 7 and higher) are typically not fully developed. In these cases, other spectral models may be more appropriate. It is critical to ship motion prediction, for both physical and numerical models, to accurately capture the frequency range for the sea state of interest. Sea state statistics, including wave heights, periods, and spectral bandwidths from various buoys and a platform in the North Sea are collected and compared with statistics from lower sea states. The spectral data are then averaged to generate a typical spectrum under the measured conditions. These developed spectra are compared with the ideal spectra mentioned previously.
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Korotaev, O. N., I. P. Kolmakov, V. P. Karpov, and M. F. Shchanov. "The High Pressure Effects in Optical Spectra of Impurity Crystals." In Spectral Hole-Burning and Related Spectroscopies: Science and Applications. Washington, D.C.: Optica Publishing Group, 1994. http://dx.doi.org/10.1364/shbs.1994.wd58.

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It is customary to assume that the optical spectra of glasses have some distinctive features which are caused by two-level systems (TLS) in the host. In the last few years the new data appeared which indicated that TLS can be found in the crystals as well. Among the evidences are the spectral jumps observation in the single molecule spectrum of p-terphenyl doped with pentacene molecular crystal [1], the revealing of the anomalous quasylinear thermal dependency of zero-phonon line halfwidth in the spectra of perylene in n-octane matrices [2,3] etc.
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Dai, Bin, Christopher Jones, Jimmy Price, Darren Gascooke, and Anthony Van Zuilekom. "COMPRESSIVE SENSING BASED OPTICAL SPECTROMETER FOR DOWNHOLE FLUID ANALYSIS." In 2021 SPWLA 62nd Annual Logging Symposium Online. Society of Petrophysicists and Well Log Analysts, 2021. http://dx.doi.org/10.30632/spwla-2021-0112.

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Downhole fluid analysis has the potential to resolve ambiguity in very complex reservoirs. Downhole fluid spectra contain a wealth of information to fingerprint a fluid and help to assess continuity. Commonly, a narrowband spectrometer with limited number of channels is used to acquire optical spectra of downhole fluid. The spectral resolution of this type of spectrometer is low due to limited number of narrowband channels. In this paper, we demonstrate a new type, compressive sensing (CS) based broadband spectrometer that provides accurate and high-resolution spectral measurement. Several specially designed broadband filters are used to simplify the mechanical, electrical, optical, and computational construction of a spectrometer, therefore provides measurement of fluid spectrum with high signal-to-noise ratio, robustness, and a broader spectral range. The compressive sensing spectrometer relies on reconstruction technique to compute the optical spectrum. Based on a large spectral database, containing more than 10000 spectra of various fluids at different temperature and pressure conditions, which were collected using conventional high resolution spectrometer in a lab, the basis functions of the optical spectra of three types of fluids (water, oil and gas/condensate) can be extracted. The reconstruction algorithm first classifies the fluid into one of three fluid types based on multichannel CS spectrometer measurements, the optical spectrum is reconstructed by using linear combination of the basis functions of corresponding fluid type, with weighting coefficients determined by minimizing the difference between calculated detector responses and measured detector responses across multiple optical channels. The reconstructed data may then be used for purposes such as contamination measurement, fluid property trends for reservoir continuity assessment, and digital sampling. Digital sampling is the process of extrapolating clean fluid properties from formation fluids not physically sampled. The reconstruction spectrum covers wavelengths from 500 nm to 3300 nm, which is a wider spectral region than has historically been accessible to formation testers. The expanded wavelength range allows access of the mid-infrared spectral region for which synthetic drilling-fluid components typically have higher optical absorbance. This reconstruction spectra may allow contamination to be directly determined. This paper will discuss the CS optical spectrometer design, fluid classification and spectral reconstruction algorithm. In addition, the applicability of the technique to fluid continuity assessment, sample contamination assessment and digital sampling will also be discussed.
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Ishijima, Tatsuki, and Takahide Sakamoto. "Wideband Ultra-Flat Spectral Enhancement by Cascaded Phase Modulation on Frequency Comb Generated from Mach-Zehnder Modulator." In CLEO: Applications and Technology. Washington, D.C.: Optica Publishing Group, 2022. http://dx.doi.org/10.1364/cleo_at.2022.jth3a.24.

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We demonstrated efficient spectral enhancement of comb generator where cascaded phase-modulation was applied to comb generated from Mach-Zehnder Modulator; additionally enhancing spectra keeping spectral flatness without increasing modulators cascade scale. 25×25-GHz spectrum was experimentally generated.
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van Zutphen, Hermione J., Philip Jonathan, and Kevin C. Ewans. "A Generic Method to Model Frequency-Direction Wave Spectra for FPSO Motions." In ASME 2008 27th International Conference on Offshore Mechanics and Arctic Engineering. ASMEDC, 2008. http://dx.doi.org/10.1115/omae2008-57481.

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We report a new approach to model the frequency-direction spectrum, in which the frequency-direction spectra from measurements or hindcast studies are fitted simultaneously in two dimensions, frequency and direction. Depending on the amount of wind forcing on the partition, either a unimodal (swell) or bimodal (wind-sea) wave spreading function is adopted together with the spectral form which best fits the frequency spectrum. This paper describes the new method and presents the results on a measured dataset.
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Reports on the topic "Spectra"

1

Thompson, James. Spectra Swarm Evaluation. Office of Scientific and Technical Information (OSTI), February 2021. http://dx.doi.org/10.2172/1765853.

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Polk, Donald. Raman Spectra of Glasses. Fort Belvoir, VA: Defense Technical Information Center, November 1986. http://dx.doi.org/10.21236/ada203343.

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Watson, K. Spectra of Surface Waves. Fort Belvoir, VA: Defense Technical Information Center, March 1989. http://dx.doi.org/10.21236/ada208482.

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Dosier, Caden. X-Ray Spectra Characterization. Office of Scientific and Technical Information (OSTI), August 2022. http://dx.doi.org/10.2172/1884752.

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Katakura, J., and T. R. England. Augmentation of ENDF/B fission product gamma-ray spectra by calculated spectra. Office of Scientific and Technical Information (OSTI), November 1991. http://dx.doi.org/10.2172/6384311.

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Hearst, J. R. Choice of computer software for analysis of spectra from the Multi-Spectral Logging System. Office of Scientific and Technical Information (OSTI), July 1994. http://dx.doi.org/10.2172/10182794.

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Balmforth, N. J., and P. J. Morrison. Normal modes and continuous spectra. Office of Scientific and Technical Information (OSTI), December 1994. http://dx.doi.org/10.2172/29346.

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Cullen, D. Sampling ENDL Watt Fission Spectra. Office of Scientific and Technical Information (OSTI), April 2004. http://dx.doi.org/10.2172/15009825.

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Russ, G. P. III, M. W. Caffee, G. B. Hudson, and N. A. Storch. Reduction of multielement mass spectra. Office of Scientific and Technical Information (OSTI), June 1990. http://dx.doi.org/10.2172/6441133.

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Davis, M. J. Hierarchical analysis of molecular spectra. Office of Scientific and Technical Information (OSTI), March 1996. http://dx.doi.org/10.2172/207374.

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