Bibliographies thématiques / Spectral fitting method

Littérature scientifique sur le sujet « Spectral fitting method »

Auteur : Grafiati
Publié le 10 mars 2023

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Articles de revues sur le sujet "Spectral fitting method"

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Yang, Yong, Lei Wang et Chuan Zheng Zhu. « Equivalent Brightness Fitting Calculation Method about White LEDs ». Applied Mechanics and Materials 121-126 (octobre 2011) : 2721–25. http://dx.doi.org/10.4028/www.scientific.net/amm.121-126.2721.

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White LEDs can show different correlated color temperature (abbreviated as CCT) by adjusting the luminous spectrum peak distribution and relative strength. Recent research results indicate that spectral luminous efficiency function of mesopic vision Vmes(λ) and equivalent brightness are associated with luminous spectra of light sources. A series of white LEDs with different CCT are tested and calculated, it shows white LED with higher CCT has higher mesopic vision equivalent brightness, although the brightness are identical when the tester corrected by traditional photopic vision spectral luminous efficiency V(λ). From the equivalent brightness curve fitting, the curve can be described as a polynomial function, for it excellent correlation, the more value of equivalent brightness could be calculated without complex derivation.
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Zhang, Liu, Jiakun Zhang, Hongzhen Song, Wen Zhang et Wenhua Wang. « Case Study on the Fitting Method of Typical Objects ». Photonics 8, no 10 (9 octobre 2021) : 432. http://dx.doi.org/10.3390/photonics8100432.

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This study proposes different fitting methods for different types of targets in the 400–900 nm wavelength range, based on convex optimization algorithms, to achieve the effect of high-precision spectral reconstruction for small space-borne spectrometers. This article first expounds on the mathematical model in the imaging process of the small spectrometer and discretizes it into an AX=B matrix equation. Second, the design basis of the filter transmittance curve is explained. Furthermore, a convex optimization algorithm is used, based on 50 filters, and appropriate constraints are added to solve the target spectrum. First, in terms of spectrum fitting, six different ground object spectra are selected, and Gaussian fitting, polynomial fitting, and Fourier fitting are used to fit the original data and analyze the best fit of each target spectrum. Then the transmittance curve of the filter is equally divided, and the corresponding AX=B discrete equation set is obtained for the specific object target, and a random error of 1% is applied to the equation set to obtain the discrete spectral value. The fitting is performed for each case to determine the best fitting method with errors. Subsequently, the transmittance curve of the filter with the detector characteristics is equally divided, and the corresponding AX=B discrete equation set is obtained for the specific object target. A random error of 1% is applied to the equation set to obtain the error. After the discrete spectral values are obtained, the fitting is performed again, and the best fitting method is determined. In order to evaluate the fitting accuracy of the original spectral data and the reconstruction accuracy of the calculated discrete spectrum, the three evaluation indicators MSE, ARE, and RE are used for evaluation. To measure the stability and accuracy of the spectral reconstruction of the fitting method more accurately, it is necessary to perform 500 cycles of calculations to determine the corresponding MSE value and further analyze the influence of the fitting method on the reconstruction accuracy. The results show that different fitting methods should be adopted for different ground targets under the error conditions. The three indicators, MSE, ARE, and RE, have reached high accuracy and strong stability. The effect of high-precision reconstruction of the target spectrum is achieved. This article provides new ideas for related scholars engaged in hyperspectral reconstruction work and promotes the development of hyperspectral technology.
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Bluteau, Cynthia E., Nicole L. Jones et Gregory N. Ivey. « Estimating Turbulent Dissipation from Microstructure Shear Measurements Using Maximum Likelihood Spectral Fitting over the Inertial and Viscous Subranges ». Journal of Atmospheric and Oceanic Technology 33, no 4 (avril 2016) : 713–22. http://dx.doi.org/10.1175/jtech-d-15-0218.1.

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AbstractA technique is presented to derive the dissipation of turbulent kinetic energy ϵ by using the maximum likelihood estimator (MLE) to fit a theoretical or known empirical model to turbulence shear spectral observations. The commonly used integration method relies on integrating the shear spectra in the viscous range, thus requiring the resolution of the highest wavenumbers of the turbulence shear spectrum. With current technology, the viscous range is not resolved at sufficiently large wavenumbers to estimate high ϵ; however, long inertial subranges can be resolved, making spectral fitting over both this subrange and the resolved portion of the viscous range an attractive method for deriving ϵ. The MLE takes into account the chi-distributed properties of the spectral observations, and so it does not rely on the log-transformed spectral observations. This fitting technique can thus take advantage of both the inertial and viscous subranges, a portion of both, or simply one of the subranges. This flexibility allows a broad range of ϵ to be resolved. The estimated ϵ is insensitive to the range of wavenumbers fitted with the model, provided the noise-dominated portion of the spectra and the low wavenumbers impacted by the mean flow are avoided. For W kg−1, the MLE fitting estimates agree with those obtained by integrating the spectral observations. However, with increasing ϵ the viscous subrange is not fully resolved and the integration method progressively starts to underestimate ϵ compared with the values obtained from fitting the spectral observations.
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Carpenter, M. H., J. G. Jernigan, P. Beiersdorfer et G. V. Brown. « The photon clean method : an event-based approach to analyzing X-ray spectra ». Canadian Journal of Physics 86, no 1 (1 janvier 2008) : 245–50. http://dx.doi.org/10.1139/p07-153.

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The Photon Clean Method (PCM) is an inverse Monte-Carlo method of spectral fitting that differs from traditional fitting routines found in spectral modeling packages by fitting event lists as opposed to binned spectra. The model spectrum is represented in event form as well. Thus, using this method it is possible to fit data of higher dimensionality than can be fit using binned spectra and standard routines based on Chi-Square statistics, such as event-mode data from electron beam ion traps or satellite observations that are tagged, for example, as a function of time, position, or energy. To demonstrate some of the power of the PCM and aid in its development, we have implemented a simplified one-dimensional version of the PCM algorithm (PCM1D). Using our implementation, which is a command-line program intended for public release, we have performed tests on simulated and observed Chandra ACIS CCD data, and present two examples, one on Cassiopeia A and another on a simulated multitemperature plasma in collisional ionization equilibrium. PACS No.: 52.65.Pp
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Gill, S., P. F. L. Maxted et B. Smalley. « The atmospheric parameters of FGK stars using wavelet analysis of CORALIE spectra ». Astronomy & ; Astrophysics 612 (avril 2018) : A111. http://dx.doi.org/10.1051/0004-6361/201731954.

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Context. Atmospheric properties of F-, G- and K-type stars can be measured by spectral model fitting or with the analysis of equivalent width (EW) measurements. These methods require data with good signal-to-noise ratios (S/Ns) and reliable continuum normalisation. This is particularly challenging for the spectra we have obtained with the CORALIE échelle spectrograph for FGK stars with transiting M-dwarf companions. The spectra tend to have low S/Ns, which makes it difficult to analyse them using existing methods. Aims. Our aim is to create a reliable automated spectral analysis routine to determine Teff, [Fe/H], V sini from the CORALIE spectra of FGK stars. Methods. We use wavelet decomposition to distinguish between noise, continuum trends, and stellar spectral features in the CORALIE spectra. A subset of wavelet coefficients from the target spectrum are compared to those from a grid of models in a Bayesian framework to determine the posterior probability distributions of the atmospheric parameters. Results. By testing our method using synthetic spectra we found that our method converges on the best fitting atmospheric parameters. We test the wavelet method on 20 FGK exoplanet host stars for which higher-quality data have been independently analysed using EW measurements. We find that we can determine Teff to a precision of 85 K, [Fe/H] to a precision of 0.06 dex and V sini to a precision of 1.35 km s−1 for stars with V sini ≥ 5 km s−1. We find an offset in metallicity ≈− 0.18 dex relative to the EW fitting method. We can determine log g to a precision of 0.13 dex but find systematic trends with Teff. Measurements of log g are only reliable enough to confirm dwarf-like surface gravity (log g ≈ 4.5). Conclusions. The wavelet method can be used to determine Teff, [Fe/H], and V sini for FGK stars from CORALIE échelle spectra. Measurements of log g are unreliable but can confirm dwarf-like surface gravity. We find that our method is self consistent, and robust for spectra with S∕N ⪆ 40.
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Eskola, Sisko Maria, et Folke Stenman. « Interpolation of Spectral Data Using the Shift Theorem of the Discrete Fourier Transform ». Applied Spectroscopy 51, no 8 (août 1997) : 1179–84. http://dx.doi.org/10.1366/0003702971941719.

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We present a method for interpolating discrete spectral data using the shift theorem of the discrete Fourier transform. The advantages of the method as compared to ordinary curve fitting and similar direct interpolation methods are that, being based on the discrete Fourier transform, our method is also very fast for large sample volumes if used with the fast Fourier transform (FFT) algorithm. In contrast to direct interpolation methods in spectral space, our method does not modify the modulus of the inverse Fourier transform of the shifted profile, so that the spectral content of the signal is preserved. The basis of the method also makes it suitable for analyzing hot-band structures in vibrational spectra. The method is illustrated with two examples.
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Ewans, K. C., E. M. Bitner-Gregersen et C. Guedes Soares. « Estimation of Wind-Sea and Swell Components in a Bimodal Sea State ». Journal of Offshore Mechanics and Arctic Engineering 128, no 4 (18 décembre 2004) : 265–70. http://dx.doi.org/10.1115/1.2166655.

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Methods for separating the spectral components and describing bimodal wave spectra are evaluated with reference to wave spectra from directional wave measurements made at the Maui location off the west coast of New Zealand. Two methods involve partitioning bimodal wave spectra into wind-sea and swell components and then fitting a spectral function to each component, while the third assigns an average spectral shape based on the integrated spectral parameters. The partitioning methods involve separating the wave spectrum into two frequency bands: a low-frequency peak, the swell component, and a high-frequency peak, the wind-sea. One partitioning method uses only the frequency spectrum while the other analyzes the complete frequency-direction spectrum. Comparison of the spectral descriptions and derived parameters against the measured counterparts provides insight into the accuracy of the different approaches to describing actual bimodal sea states.
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Wu, Hao, Qing Wang, Liang Zhou et Jin Meng. « Spectral fitting method for designing radar sequence with spectral nulling and correlation constraints ». IET Radar, Sonar & ; Navigation 12, no 11 (novembre 2018) : 1260–67. http://dx.doi.org/10.1049/iet-rsn.2018.5171.

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Zhu, Xiaolan, Ya Dai, Changguo Wang et Lanlan Tan. « Quantitative and Structure Analysis of Cellulose in Tobacco by 13C CP / MAS NMR Spectroscopy ». Beiträge zur Tabakforschung International/Contributions to Tobacco Research 27, no 3 (1 juillet 2016) : 126–35. http://dx.doi.org/10.1515/cttr-2016-0014.

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SUMMARY A new method utilizing 13C cross-polarization/magic angle spinning (CP/MAS) nuclear magnetic resonance (NMR) spectra was developed for the simultaneous quantitative determination and structure analysis of tobacco cellulose from hot water or acid detergent extraction. A reference spectrum of tobacco noncellulose components was subtracted from the spectrum of each sample to obtain a subspectrum of the cellulose components. The NMR spectra in combination with spectral fitting were analyzed in detail and some parameters, such as the content of cellulose, crystallinity, allomorph composition and lateral dimensions for cellulose elementary fibrils and microfibrils were determined. The quantitative results showed that the average recovery was 94.0% with a relative standard deviation (RSD) of 4.6–4.8%. The structure results obtained by the spectral fitting for the cellulose C1-region showed that the main allomorph composition in tobacco cellulose was Iβ. The cellulose crystallinity calculated by the spectral fitting in C4 -region was about 50%. The lateral dimensions for cellulose elementary fibrils and microfibrils were in the range of 3.0–6.0 nm and 6.0–13.0 nm, respectively. Therefore, this NMR method could provide important information on both amount and structure of cellulose in tobacco.
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Zhu, Jianxiong, Charles K. Mann et Thomas J. Vickers. « Simultaneous Dual-Window Measurements with a Linear Photodiode Array Detector ». Applied Spectroscopy 42, no 8 (novembre 1988) : 1567–71. http://dx.doi.org/10.1366/0003702884429733.

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A generally applicable method is described for simultaneous measurement of reference and analyte spectral features which would not otherwise fall within the range covered by a single linear diode array detector. The method employs dual entrance slits on the spectrometer to cause two spectral windows to overlap on the detector. The method is demonstrated for fluorescence measurement of Rhodamine B in ethanol. Recovery of the spectral information from the overlapped spectra using a least-squares fitting procedure is demonstrated. The simultaneously recorded reference measurements are shown to be effective in correcting for excitation source intensity variation by comparing corrected and uncorrected excitation spectra and calibration curve data.
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Thèses sur le sujet "Spectral fitting method"

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Chih-FengLin et 林志峯. « Investigation of spectral fitting method for extracting optical properties of tissue phantoms at NIR range ». Thesis, 2016. http://ndltd.ncl.edu.tw/handle/n3e922.

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碩士
國立成功大學
光電科學與工程學系
104
In this thesis, we demonstrate the use of optical method, diffuse reflectance spectroscpoy (DRS), and we will the obtain spectrum of liquid phantoms from DRS, to investigate physiological parameters of liquid phantoms. First, we will obtain reflectance of phantoms at the range of 500nm to 1000nm. Further we will compare two spectral fitting methods of DRS in measuring biological optical properties, one is Multi-Wavelength method and another is Multi-Distance method. The liquid phantoms are used to measure the absorption and scattering coefficient under the range of normal and tumorous breast tissue by these two spectral fitting methods, and to compare both effect. The purpose is to construct a non-invasive, cheaper and simple optical system, and the system can quantify the chromophore concentrations of breast tissue in the future.
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FORTUNATO, COSIMO. « From inversion processes optimization to model optimization ». Doctoral thesis, 2013. http://hdl.handle.net/2158/799891.

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The present work traces a path in the context of inverse problems, within a more general framework of complex systems. In our case, the inverse problem originates from the need to interpret indirect physical measurements of an object of interest. Moving in this area two cases are brought to the attention. The first is the estimation of the parameters of a mathematical model, based on a comparison with experimental measurements. The second tries to identify what it might be called the "best model" that takes into account the experimental behavior recorded in various situations of interest. The first case relates to the recovery of the fluorescence and reflectance of maize chlorophyll. The second case addressed concerns the development of a model that takes into account the effects of silanization in aggregates and dispersed laser-activatable gold nanorods.
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Su, Yo-Lin, et 蘇佑璘. « Numerical fitting method used in analyzing spectrum signal of sphygmograph for Dyspepsia and Rhinitis ». Thesis, 2011. http://ndltd.ncl.edu.tw/handle/8r54g2.

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碩士
國立中興大學
生物產業機電工程學系所
99
Traditional Chinese Medicine (TCM) has a complete set of diagnosis and treatment method, but it seems too subjective that all diagnosis and treatments depend on Chinese medicine practitioners. Therefore, the scientific study of TCM in diagnosis is executed by radial arterial pulse use sphygmograph and numerical methods. The recording of radial pressure pulse at Chun, Guan and Chy positions were further analyzed. In this study, 103 subjects including 39 controls, 33 dyspepsias and 31 rhinitis were diagnosed by Chinese medicine practitioner. Every subject was recorded 6 seconds of radial arterial pulse at Chun, Guan and Chy positions on both hands. Then the numerical methods of Fourier transform , filter, and fitting were employed to analysis the data and 4 parameters of a, b, x0,and y0 were induced. The four parameters were adopted to calculate the area between graph and horizontal axis without the effect of y0. Each parameter’s outliers were removed by the criterion of the group mean ±three times the standard deviation. These five indicators (a, b, x0, y0, and area) were analyzed by ANOVA. The parameter has no effect on the result at significant level α = 0.01. The different positions with the other four parameters were analyzed and discussed by ANOVA and Tukey’s test. At significant level α = 0.01, parameter b and x0 cannot distinguish the difference between normal, dyspepsia and rhinitis, nevertheless, at right Guan, dyspepsia and rhinitis’ values of a and area are higher than normal’s, and the rhinitis’ values of a and area are higher than dyspepsia’s at left Chun.
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Hlavacek-Larrondo, Julie. « Analyse cinématique de l'hydrogène ionisé et étude du gaz ionisé diffus de trois galaxies du Groupe Sculpteur : NGC253, NGC300 et NGC247 ». Thèse, 2009. http://hdl.handle.net/1866/8048.

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Livres sur le sujet "Spectral fitting method"

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Chance, Kelly, et Randall V. Martin. Data Fitting. Oxford University Press, 2017. http://dx.doi.org/10.1093/oso/9780199662104.003.0011.

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This chapter explores several of the most common and useful approaches to atmospheric data fitting as well as the process of using air mass factors to produce vertical atmospheric column abundances from line-of-sight slant columns determined by data fitting. An atmospheric spectrum or other type of atmospheric sounding is usually fitted to a parameterized physical model by minimizing a cost function, usually chi-squared. Linear fitting, when the model of the measurements is linear in the model parameters is described, followed by the more common nonlinear fitting case. For nonlinear fitting, the standard Levenberg-Marquardt method is described, followed by the use of optimal estimation, one of several retrieval methods that make use of a priori information to providing regularization for the solution. In the context of optimal estimation, weighting functions, contribution functions, and averaging kernels are described. The Twomey-Tikhonov regularization procedure is presented. Correlated parameters, with the important example of Earth’s atmospheric ozone, are discussed.
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Chapitres de livres sur le sujet "Spectral fitting method"

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Schmal, Christoph, Gregor Mönke et Adrián E. Granada. « Analysis of Complex Circadian Time Series Data Using Wavelets ». Dans Methods in Molecular Biology, 35–54. New York, NY : Springer US, 2022. http://dx.doi.org/10.1007/978-1-0716-2249-0_3.

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AbstractExperiments that compare rhythmic properties across different genetic alterations and entrainment conditions underlie some of the most important breakthroughs in circadian biology. A robust estimation of the rhythmic properties of the circadian signals goes hand in hand with these discoveries. Widely applied traditional signal analysis methods such as fitting cosine functions or Fourier transformations rely on the assumption that oscillation periods do not change over time. However, novel high-resolution recording techniques have shown that, most commonly, circadian signals exhibit time-dependent changes of periods and amplitudes which cannot be captured with the traditional approaches. In this chapter we introduce a method to determine time-dependent properties of oscillatory signals, using the novel open-source Python-based Biological Oscillations Analysis Toolkit (pyBOAT). We show with examples how to detect rhythms, compute and interpret high-resolution time-dependent spectral results, analyze the main oscillatory component, and to subsequently determine these main components’ time-dependent instantaneous period, amplitude, and phase. We introduce step-by-step how such an analysis can be done by means of the easy-to-use point-and-click graphical user interface (GUI) provided by pyBOAT or executed within a Python programming environment. Concepts are explained using simulated signals as well as experimentally obtained time series.
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Hawthorne, F. C., et G. A. Waychunas. « Chapter 3. SPECTRUM-FITTING METHODS ». Dans Spectroscopic Methods in Mineralogy and Geology, sous la direction de Frank C. Hawthorne, 63–98. Berlin, Boston : De Gruyter, 1988. http://dx.doi.org/10.1515/9781501508974-005.

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Hillinger, Claude, et Monika Sebold. « Identifying Discrete Cycles in Economic Data : Maximum Entropy Spectra and the Direct Fitting of Sinusoidal Functions ». Dans Maximum Entropy and Bayesian Methods, 321–29. Dordrecht : Springer Netherlands, 1989. http://dx.doi.org/10.1007/978-94-015-7860-8_32.

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Xu, Zuxiong, Ruzhang Ma et Jueyun Ping. « The Fitting Method for Mössbauer Spectra of Amorphous Alloys and an Investigation of their Properties and Structure ». Dans Industrial Applications of the Mössbauer Effect, 371–98. Boston, MA : Springer US, 1986. http://dx.doi.org/10.1007/978-1-4613-1827-9_19.

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Eremenko, S. A., O. N. Kalugin et D. A. Nerukh. « Decomposition of Vibrational Spectra of Liquids with Overlapping Bands of Complex Shape : Uniqueness of Solution and Method of Fitting ». Dans Spectroscopy of Biological Molecules : Modern Trends, 575–76. Dordrecht : Springer Netherlands, 1997. http://dx.doi.org/10.1007/978-94-011-5622-6_262.

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Kasugai, Y., N. Matsuda, Y. Sakamoto, H. Nakashima, H. Yashima, H. Matsumura, H. Iwase et al. « Fitting Method for Spectrum Deduction in High-Energy Neutron Field Induced by GeV-Protons Using Experimental Reaction-Rate Data ». Dans Reactor Dosimetry : 14th International Symposium, 675–89. 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959 : ASTM International, 2012. http://dx.doi.org/10.1520/stp49648t.

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Kasugai, Y., N. Matsuda, Y. Sakamoto, H. Nakashima, H. Yashima, H. Matsumura, H. Iwase et al. « Fitting Method for Spectrum Deduction in High-Energy Neutron Field Induced by GeV-Protons Using Experimental Reaction-Rate Data ». Dans Reactor Dosimetry : 14th International Symposium, 675–89. 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959 : ASTM International, 2012. http://dx.doi.org/10.1520/stp155020120051.

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Heremans, Karel, et Koen Goossens. « Pressure-Tuning Spectroscopy of Proteins : Fourier Transform Infrared Studies in the Diamond Anvil Cell ». Dans High Pressure Effects in Molecular Biophysics and Enzymology. Oxford University Press, 1996. http://dx.doi.org/10.1093/oso/9780195097221.003.0007.

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The effect of hydrostatic pressure on the secondary structure of proteins can be followed by Fourier transform infrared (FTIR) spectroscopy in the diamond anvil cell. Pressure-induced changes in the amide I’ region of the deconvolved spectrum are used to follow the features of the secondary structure up to 20 kbar. The changes in the side chains such as tyrosine also can be followed. A self-deconvolution and fitting procedure is presented that allows the determination of both pressure-induced and temperature-induced changes in the secondary structure of proteins. The method takes into account the elastic, as well as the possible conformational, effects on the spectral bands of the protein. Applications are presented on pressure-induced changes in several proteins. Attention is also given to the influence of inert cosolvents. The fundamental principles of the phase diagram of proteins are presented to clarify their importance for understanding the behavior of proteins under pressure at different temperatures. Our results show that the infrared technique explores unique aspects of the behavior of proteins under these extreme conditions. The study of the effects of pressure has received considerable attention in recent years (Balny et al., 1992; Silva & Weber, 1993). In general, low pressures induce reversible changes such as the dissociation of protein-protein complexes, the binding of ligands, and conformational changes. Pressures higher than about 5 kbar induce denaturation, which in most cases is irreversible. However, reports on a few proteins indicate that such high pressures may also cause reversible changes. One such protein is horse scrum albumin (Chen & Heremans, 1990). A molecular interpretation of these phenomenon is based on the fact that pressure mainly affects the volume of a system, thus damping the molecular fluctuations. Temperature effects are known to affect both the kinetic energy and the volume of the system. Early in this century, it was shown that one can cook an egg by subjecting it to high pressure (Bridgman, 1914). The appearance of the pressure-induced coagulum of egg white is quite different from the coagulum induced by temperature.
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Deng, Jin, et Shutong Li. « Correlation Fitted of Loess Microscopic Parameter Statistics with Shear Strength C and φ ». Dans Advances in Transdisciplinary Engineering. IOS Press, 2022. http://dx.doi.org/10.3233/atde220854.

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The microstructure of loess mainly reflects the size distribution, orientation, contact mode and pore distribution of particles. The six original loess (low clayey silt loess) on the same site in Lanzhou is selected by the direct shear test, high power electron microscope and energy spectrum test. To simulated calculation the cohesion (C) and internal friction angle (φ), used by the parameters data, including to the mineral element (Fe/Al/Si, Al/Si, K) ratio, microstructure parameters (Long axis of the particles, long axis’ skewness, kurtosis and orientation degree. The results indicated that the (φ) value was linearly correlated with the mean value of the Angle, and the correlation coefficient of the fitting formula was 0.82. The cohesion C value was linearly correlated with the kurtosis, Skewness, Fe/Si, Al/Si and K/Al of the long axis, and the maximum correlation coefficient after fitting was 0.99. The fitting formula of microcosmic parameters and shear strength can provide a new research method for predicting the shear strength of loess samples.
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Actes de conférences sur le sujet "Spectral fitting method"

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Wu, Hao, Jin Meng, Qing Wang, Jin ling Xing et Liang Zhou. « A spectral fitting method for designing spectrum compatibility sequence with low correlation sidelobes ». Dans 2018 IEEE International Symposium on Electromagnetic Compatibility and 2018 IEEE Asia-Pacific Symposium on Electromagnetic Compatibility (EMC/APEMC). IEEE, 2018. http://dx.doi.org/10.1109/isemc.2018.8393818.

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Pan, Jingchang, et Weixiang Dong. « Extraction of Characteristic Spectral Line Based on Gaussian Fitting Method ». Dans 2009 International Conference on Artificial Intelligence and Computational Intelligence. IEEE, 2009. http://dx.doi.org/10.1109/aici.2009.36.

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Ferrier, Graham A., Shahraam Afshar V., Xiaoyi Bao et Liang Chen. « A new fitting method for spectral characterization of Brillouin-based distributed sensors ». Dans Applications of Photonic Technology, sous la direction de Roger A. Lessard et George A. Lampropoulos. SPIE, 2003. http://dx.doi.org/10.1117/12.543836.

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Arina, R., R. Marsilio, R. Arina et R. Marsilio. « A shock-fitting spectral method for the study of shock-vortex interactions ». Dans 28th Fluid Dynamics Conference. Reston, Virigina : American Institute of Aeronautics and Astronautics, 1997. http://dx.doi.org/10.2514/6.1997-1839.

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Bai, Xiaodong, Wendeng Zhu, Gengxin Zhang, Tao Hong, Laiding Zhao et Jing Hu. « Identification Method of Power Spectral Signal Based on Fourier Series Fitting and Density Clustering ». Dans the 8th International Conference. New York, New York, USA : ACM Press, 2018. http://dx.doi.org/10.1145/3290480.3290495.

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Taudt, Christopher, et Peter Hartmann. « Method for simple phase recovery and denoising in spectral imaging interferometry based on error-diffusion dithering ». Dans Imaging Systems and Applications. Washington, D.C. : Optica Publishing Group, 2022. http://dx.doi.org/10.1364/isa.2022.if3b.1.

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Dithering of spectral interferometric data helps to reduce intensity noise and improve fitting accuracy. A simple phase recovery method is developed using dithering to enhance measurement range in profilometry.
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Scragg, Carl A. « Spectral Analysis of Ship-Generated Waves in Finite-Depth Water ». Dans ASME 2002 21st International Conference on Offshore Mechanics and Arctic Engineering. ASMEDC, 2002. http://dx.doi.org/10.1115/omae2002-28510.

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Recent efforts to compare the waves generated by different vessels traveling in finite-depth water have struggled with difficulties presented by various data sets of wave elevations (either measurements or predictions) corresponding to different lateral distances from the ship. Some of the attempts to shift the data to a common reference location have relied upon crude and potentially misleading approximations. The use of free-wave spectral-methods not only overcomes such difficulties, but it also provides us the means to accurately extend CFD results into the far field. As in the deep-water case, one can define a free-wave spectrum that is valid for all lateral positions and distances astern of the vessel. The free-wave spectrum contains a complete description of the Kelvin wake, and wave elevations at any far-field position can be readily calculated once the spectrum is known. For the case of infinitely deep water, Eggers, Sharma, and Ward [1967] presented a method by which free-wave spectra can be determined from appropriate measurements of the far-field wave elevations. The current paper discusses the use of free-wave spectra for finite-depth problems and presents a method for the determination of free-wave spectra based upon fitting predicted wave elevations to a corresponding data set. The predicted wave elevations can be calculated from an unknown distribution of finite-depth Havelock singularities. The unknown singularities are determined by minimizing the mean-square-difference between predicted and measured wave fields. The method appears to be quite general and can be used to calculate either finite or infinite-depth free-wave spectra from experimental data or from local CFD predictions.
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Liu, Xu, et F. J. Murcray. « N2O Vertical Profiles Retrieved from Ground-based Solar Absorption Spectra Taken at McMurdo Station During Austral Spring of 1989 ». Dans Optical Remote Sensing of the Atmosphere. Washington, D.C. : Optica Publishing Group, 1995. http://dx.doi.org/10.1364/orsa.1995.tuc5.

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N2O can be a tracer of atmospheric air motion due to its long life time. Ground-based FTIR solar spectra contain information on the vertical distributions of N2O due to pressure-broadening of absorption lines. We have combined the Chahine-Twomey' relaxation method with a line-by-line layer-by-layer radiative transfer code to retrieve N2O VMR profiles from ground-based solar absorption spectra. The spectra were taken at McMurdo station during the austral spring of 1989 with a 0.02 wavenumber resolution FTIR spectrometer. Since N2O is released from troposphere and is photolyzed in the stratosphere, the line shape of its absorption is mainly due Lorentz broadening. The 0.02 wavenumber resolution is high enough for us to retrieve N2O VMR profiles up to 25 kilometers. Figure 1 shows a typical observed N2O solar spectrum near 1993.15 wavenumber (solid line) and a calculated spectrum using our profile retrieval program. The best fit is obtained by iteratively adjusting N2O VMR profile according to the formulation of Chahine and Twomey. A contour plot of N2O VMR versus altitude and julian day number is shown in Figure 2. The lower tropospheric N2O VMRs have an average value around 310 ppb. Correlations of the N2O contour with that of temperature shows interesting features of tropospheric and lower stratospheric air motions. We have also compared the total N2O column amounts retrieved from this profile retrieval method and from the PC version of the non-linear least square spectral fitting algorithm (SFIT). The temporal variations of the N2O total column amounts retrieved from two methods show excellent correlation.
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Kong, Boran, Han Zhang, Kaijie Zhu, Chen Hao, Jiong Guo et Fu Li. « The Optimal Theta of Optimally Diffusive Coarse Mesh Finite Difference Method to Accelerate DGFEM Based SN ». Dans 2022 29th International Conference on Nuclear Engineering. American Society of Mechanical Engineers, 2022. http://dx.doi.org/10.1115/icone29-89221.

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Abstract Optimally diffusive coarse mesh finite difference (odCMFD) method is a recently developed acceleration method for neutron transport equation. Compared with the traditional CMFD, it adds an optimal theta on the diffusion coefficient. This new acceleration method achieves a higher convergence rate than the traditional CMFD and promises the convergence even in large optical thickness region. However, the optimal theta of odCMFD is determined by the Fourier analysis results of the 1D traditional SN. When applying the odCMFD to accelerate DGFEM based SN, this optimal theta is not always suitable. Therefore, it is necessary to find a new optimal theta for this new scheme. In this paper, a Fourier analysis of DGFEM based SN using odCMFD acceleration for k-eigenvalue neutron transport problem is conducted. Fourier analysis results show that when the number of inner iterations is higher than 10, the increment of the inner iterations has little impact on the spectral radius. Meanwhile, the order of the DGFEM based SN and the order of SN quadrature set have little impact on the spectral radius. The scattering ratio has great impact on the spectral radius, the decrement of scattering ratio increases the spectral radius. Set the number of inner iterations as 10, for different scattering ratio, an optimal theta of odCMFD and a polynomial fitting curve are obtained by Fourier analysis. Finally, numerical estimations of spectral radius are obtained by real 1D DGFEM based SN calculation with odCMFD acceleration. The experiment values fit well with the Fourier analysis theoretical results.
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Antunes, Jose, Laurent Borsoi, Xavier Delaune et Philippe Piteau. « Identification of the Turbulence Force Field Excitation From a Set of Vibratory Responses of a Multi-Supported Tube ». Dans ASME 2013 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/pvp2013-98146.

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In this paper we address the identification of the spectral and spatial features of random flow excitations, for multi-supported tubular components such as steam generator tubes and nuclear fuel rods. In the proposed work, source identification is performed from a set of measured vibratory responses, in the following manner: (1) The modal response spectra and modeshape amplitudes at the measurement locations are first extracted through a blind decomposition of the physical response matrix, using the SOBI method; (2) The continuous modeshapes are interpolated from the identified values at the measurement locations; (3) The system modal parameters are identified from the modal responses using a simple SDOF fitting technique; (4) Inversion from the modal response spectra is performed for the identification of the modal excitation spectra; (5) Finally, an equivalent physical excitation spectra as well as the flow velocity profiles are estimated. The proposed approach is illustrated with identification results based on realistic numerical simulations of a multi-supported tube under linear support conditions.
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