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Articles de revues sur le sujet « Frequency refinement »

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Auteur : Grafiati
Publié le 14 mars 2023

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1

Mizutani, Yoshiki, Jun Kawata, Kenji Miwa, Kazuo Yasue, Takuya Tamura et Yasuji Sakaguchi. « Effect of the frequency of electromagnetic vibrations on microstructural refinement of AZ91D magnesium alloy ». Journal of Materials Research 19, no 10 (1 octobre 2004) : 2997–3003. http://dx.doi.org/10.1557/jmr.2004.0369.

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The static magnetic field and the alternating electric field were simultaneously imposed on AZ91D magnesium alloy melt, and α-dendrite particles were refined by the electromagnetic vibrations. The effect of the frequency of electromagnetic vibrations on microstructural refinement was quantitatively investigated. In the frequency range from 60 to 1000 Hz, the vibration frequency near 200 Hz was the most effective for the refinement of α-dendrite particles, and α-dendrite particles were refined up to approximately 100 μm from 1800 μm at this frequency. However, the effect of refinement by the electromagnetic vibrations became weak at frequencies above 400 Hz. Although the degree of refinement of the primary particles differed with the frequency of the electromagnetic vibrations, the dendrite arm spacing was almost constant, 30–40 μm, in our experiment. Therefore, the refinement of primary α-dendrite particles is likely to be caused by collapse of dendrite arms due to the cavitation phenomenon and the stirring of the melt.
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2

Zuo, Yu Bo, Zhi Hao Zhao, Hai Tao Zhang, Ke Qin et Jian Zhong Cui. « Combined Effect of Electromagnetic Field and Grain Refiner on Microstructure of Φ310 Mm 7050 Aluminium Alloy Ingot ». Advanced Materials Research 399-401 (novembre 2011) : 1708–11. http://dx.doi.org/10.4028/www.scientific.net/amr.399-401.1708.

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Grain refinement is quite important for producing 7050 alloy ingot especially in large scale. Low frequency electromagnetic casting (LFEC) process was used to make 7050 aluminum alloy Φ310 ingots and study the effect of electromagnetic field and grain refiner on the microstructure of 7050 alloy ingots. The results showed that both grain refiner and low frequency electromagnetic field can result in some grain refinement of 7050 alloy. However, the low frequency electromagnetic field shows more remarkable grain refinement. For the grain refined alloy by grain refiner, further significant grain refinement can be achieved with the application of low frequency electromagnetic field. The finest microstructure was achieved by combining the applications of both grain refiner and electromagnetic field.
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3

Maksimenko, S. G. « Design procedure of relative frequency measure error refinement ». Izmeritel`naya Tekhnika, no 1 (2018) : 15–17. http://dx.doi.org/10.32446/0368-1025it.2018-1-15-17.

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4

JUN, Jae-Hee, Ji-Hoon CHOI et Jong-Ok KIM. « Middle-Frequency Based Refinement for Image Super-Resolution ». IEICE Transactions on Information and Systems E99.D, no 1 (2016) : 300–304. http://dx.doi.org/10.1587/transinf.2015edl8180.

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5

Lunin, V. Yu, et T. P. Skovoroda. « Frequency-restrained structure-factor refinement. I. Histogram simulation ». Acta Crystallographica Section A Foundations of Crystallography 47, no 1 (1 janvier 1991) : 45–52. http://dx.doi.org/10.1107/s0108767390010042.

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6

Goodman, T. N. T., et Charles A. Micchelli. « On Refinement Equations Determined by Pólya Frequency Sequences ». SIAM Journal on Mathematical Analysis 23, no 3 (mai 1992) : 766–84. http://dx.doi.org/10.1137/0523040.

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7

Ma, Xiaoping, Yingju Li et Yuansheng Yang. « Grain refinement effect of pulsed magnetic field on solidified microstructure of superalloy IN718 ». Journal of Materials Research 24, no 10 (octobre 2009) : 3174–81. http://dx.doi.org/10.1557/jmr.2009.0382.

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The refinement mechanism of pulsed magnetic field (PMF) was discussed by experimental investigation, and the effects of exciting frequency, exciting voltage, and delay time of PMF on grains refinement of superalloy were studied. The experimental results show that, as exciting frequency or exciting voltage is increased, the grains are refined. However, the grains become coarse when frequency increases further. As delay time of PMF increases, the grain size increases. The refinement effect of PMF is attributed to the detachment of heterogeneous nuclei on the mold wall and subsequently separation of nuclei in the melt. The Joule heat can prolong the continuous nucleation process. However, the refinement effect will be impaired if the Joule heat is strong enough to remelt the detached nuclei.
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8

Deng, Leilei, et Kaijing Leng. « Application of two spectrum refinement methods in frequency estimation ». Journal of Physics : Conference Series 2290, no 1 (1 juin 2022) : 012070. http://dx.doi.org/10.1088/1742-6596/2290/1/012070.

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Abstract Considering the limitation of FFT frequency estimation method in resolution, this paper briefly introduces the complex modulation ZOOM-FFT and Chirp-Z transform spectrum zooming methods. The simulation results show that the ZOOM-FFT method has better anti spectrum leakage and interference effect. Furthermore, the two methods are applied to the frequency estimation of underwater high-speed maneuvering target, and it is found that Chirp-Z transform method can obtain smoother and stable frequency history, and has more flexible frequency resolution.
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9

Lunin, V. Yu, et E. A. Vernoslova. « Frequency-restrained structure-factor refinement. II. Comparison of methods ». Acta Crystallographica Section A Foundations of Crystallography 47, no 3 (1 mai 1991) : 238–43. http://dx.doi.org/10.1107/s0108767390013526.

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10

Wu, Kai, Wei Ni, J. Andrew Zhang, Ren Ping Liu et Y. Jay Guo. « Refinement of Optimal Interpolation Factor for DFT Interpolated Frequency Estimator ». IEEE Communications Letters 24, no 4 (avril 2020) : 782–86. http://dx.doi.org/10.1109/lcomm.2019.2963871.

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11

Zhong, Ming Shou, Quan Min Xie, Tao Guo, Xing Bo Xie, Hao Quan Liu et Zhong Hong Yan. « Refinement Analysis for Time-Frequency Characteristic of Blasting Seismic Exploration Signals ». Advanced Materials Research 926-930 (mai 2014) : 3541–44. http://dx.doi.org/10.4028/www.scientific.net/amr.926-930.3541.

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Accurate extraction of time-frequency features for blasting vibration signals has great significance for blasting seismic exploration, so time-frequency analysis method for blasting seismic signals was researched based on frequency slice wavelet transformation technology, and separation and extraction of time-frequency features were were successfully achieved. Frequency slice wavelet transformation can be introduced into blasting vibration effect analysis fields, it can provide a new research idea for refinement analysis of time-frequency characteristics, and it also has great significance for improving the effect of blasting seismic exploration in China.
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12

Millwater, Harry R., Michael P. Enright et Simeon H. K. Fitch. « Convergent Zone-Refinement Method for Risk Assessment of Gas Turbine Disks Subject to Low-Frequency Metallurgical Defects ». Journal of Engineering for Gas Turbines and Power 129, no 3 (15 septembre 2006) : 827–35. http://dx.doi.org/10.1115/1.2431393.

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Titanium gas turbine disks are subject to a rare but not insignificant probability of fracture due to metallurgical defects, particularly hard α. A probabilistic methodology has been developed and implemented in concordance with the Federal Aviation Administration (FAA) Advisory Circular 33.14-1 to compute the probability of fracture of gas turbine titanium disks subject to low-frequency metallurgical (hard α) defects. This methodology is further developed here to ensure that a robust, converged, accurate calculation of the probability is computed that is independent of discretization issues. A zone-based material discretization methodology is implemented, then refined locally through further discretization using risk contribution factors as a metric. The technical approach is akin to “h” refinement in finite element analysis; that is, a local metric is used to indicate regions requiring further refinement, and subsequent refinement yields a more accurate solution. Supporting technology improvements are also discussed, including localized finite element refinement and onion skinning for zone subdivision resolution, and a restart database and parallel processing for computational efficiency. A numerical example is presented for demonstration.
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13

Yang, Xiao Lan, Min Ping Jia, Jing Chao Zou, Ji Feng Liu et Fang Min Xv. « Frequency Conversion Control for Vibration Mill with High Vibration Intensity Based on Multi-Wave Variable Sinusoid ». Advanced Materials Research 538-541 (juin 2012) : 2504–7. http://dx.doi.org/10.4028/www.scientific.net/amr.538-541.2504.

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The key technology of vibration machine to finish deaggregation and powder refinement is both high vibration Intensity with a certain frequency and steady vibration of frequency conversion control. A frequency conversion control for vibration mill system based on multi-wave variable sinusoidal frequency ascending and descending cycle curve was developed. The frequency conversion control test of vibration mill was finished through sensing signal amplification, analog digital conversion and on line detection. The results show that the high and super-high vibration intensity with certain action time is produced and the effect of multi-amplitude and multi-frequency is acquired. The experimental data show that the super micro grinding of superfine particles is achieved, energy consumption is reduced, the useful life of wearing parts such as bearing is extended, and engineering effects of deaggregation and refinement of super-hard superfine powder are obtained by frequency conversion control.
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14

Niruban. « NOVEL COLOR FILTER ARRAY DEMOSAICING IN FREQUENCY DOMAIN WITH SPATIAL REFINEMENT ». Journal of Computer Science 10, no 8 (1 août 2014) : 1591–99. http://dx.doi.org/10.3844/jcssp.2014.1591.1599.

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15

Olmo, G., L. Lo Presti et D. Bosetto. « Progressive refinement approach to MLE : an application to carrier frequency recovery ». IEEE Transactions on Communications 49, no 7 (juillet 2001) : 1148–53. http://dx.doi.org/10.1109/26.935154.

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16

Hawary, Fatma, Guillaume Boisson, Christine Guillemot et Philippe Guillotel. « Compressively sampled light field reconstruction using orthogonal frequency selection and refinement ». Signal Processing : Image Communication 92 (mars 2021) : 116087. http://dx.doi.org/10.1016/j.image.2020.116087.

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17

Zuo, Yu Bo, Zhi Hao Zhao et Jian Zhong Cui. « Grain Refinement of Direct Chill Cast 7050 Aluminium Alloy with Low Frequency Electromagnetic Field ». Advanced Materials Research 402 (novembre 2011) : 850–53. http://dx.doi.org/10.4028/www.scientific.net/amr.402.850.

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Low frequency electromagnetic casting (LFEC) process was used to make 7050 aluminum alloy 162mm ingots and study its effect on the as-cast microstructure. Effects of electromagnetic field parameters such as frequency and current intensity on microstructures were systemically investigated. The results showed that LFEC has a significant grain refining effect on 7050 alloy. The microstructures of LFEC ingot from the border to the center of the cross section are all equiaxed or nearly equiaxed grains which are much finer and more uniform than those of DC cast ingot. It was also found that electromagnetic field frequency and current intensity play important roles on the microstructure refinement. The discussion was mainly focused on the mechanism of grain refinement by LFEC process.
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18

Dey, Saikat. « Evaluation of p-FEM Approximations for Mid-Frequency Elasto-Acoustics ». Journal of Computational Acoustics 11, no 02 (juin 2003) : 195–225. http://dx.doi.org/10.1142/s0218396x03001882.

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p-refinement strategies for numerical simulation of three-dimensional elasto-acoustic problems in the mid-frequency range are evaluated using high-order finite/infinite element-based approximations. Numerical experiments are used to study the convergence of an appropriate quantity-of-interest (QOI) as a function of polynomial degrees for the elastic-displacement and pressure fields.
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19

Sindhu, Monica, N. Ahlawat, Sujata Sanghi, Ashish Agarwal, A. Ashima, Rekha Kumari et Navneet N. Ahlawat. « Rietveld Refinement and DC Conductivity of Na0.5K0.5NbO3 Ceramics ». Advanced Materials Research 585 (novembre 2012) : 210–13. http://dx.doi.org/10.4028/www.scientific.net/amr.585.210.

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Potassium Sodium Niobate, Na0.5K0.5NbO3 is a promising base material for lead free piezoceramics. The polycrystalline sample Na0.5K0.5NbO3 was synthesized using solid state reaction method. The crystal structure and phase purity was studied by XRD and analysed using Rietveld refinement method. Good agreement was observed between the observed and calculated patterns in Rietveld refinement. The refinement inferred orthorhombic crystal structure with Amm2 space group. The impedance spectroscopy of the sample was performed in frequency range 10 Hz to 7 MHz in temperature range 573K to 703K. The activation energy was obtained to be 0.67eV from the reciprocal temperature variation of dc conductivity which follows the Arrhenius law.
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20

White, Charmaine, Cliff Richardson et Libertad Raibstein. « High-Frequency Ventilation and Extracorporeal Membrane Oxygenation ». AACN Advanced Critical Care 1, no 2 (1 août 1990) : 427–44. http://dx.doi.org/10.4037/15597768-1990-2022.

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Dramatic improvement in morbidity and mortality associated with neonatal respiratory failure has evolved over the last 30 years. Favorable survival statistics can be directly related to the institution and refinement of assisted ventilation techniques. Short-and long-term pulmonary complications continue to be of major concern. New ways to support the neonate in respiratory failure are being investigated. Concentrated efforts are being undertaken to find ways to safely and effectively treat these infants while decreasing the morbidity associated with therapy. Two such therapies, both experimental and controversial, which are gaining widespread recognition, are high-frequency ventilation (HFV) and extracorporeal membrane oxygenation (ECMO)
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21

Sovago, Ioana, Anna A. Hoser et Anders Ø. Madsen. « A combined model of electron density and lattice dynamics refined against elastic diffraction data. Thermodynamic properties of crystalline L-alanine ». Acta Crystallographica Section A Foundations and Advances 76, no 1 (1 janvier 2020) : 32–44. http://dx.doi.org/10.1107/s205327331901355x.

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Thermodynamic stability is an essential property of crystalline materials, and its accurate calculation requires a reliable description of the thermal motion – phonons – in the crystal. Such information can be obtained from periodic density functional theory (DFT) calculations, but these are costly and in some cases insufficiently accurate for molecular crystals. This deficiency is addressed here by refining a lattice-dynamics model, derived from DFT calculations, against accurate high-resolution X-ray diffraction data. For the first time, a normal-mode refinement is combined with the refinement of aspherical atomic form factors, allowing a comprehensive description and physically meaningful deconvolution of thermal motion and static charge density in the crystal. The small and well diffracting L-alanine system was used. Different lattice-dynamics models, with or without phonon dispersion, and derived from different levels of theory, were tested, and models using spherical and aspherical form factors were compared. The refinements indicate that the vibrational information content in the 23 K data is too small to study lattice dynamics, whereas the 123 K data appear to hold information on the acoustic and lowest-frequency optical phonons. These normal-mode models show slightly larger refinement residuals than their counterparts using atomic displacement parameters, and these features are not removed by considering phonon dispersion in the model. The models refined against the 123 K data, regardless of their sophistication, give calculated heat capacities for L-alanine within less than 1 cal mol−1 K−1 of the calorimetric measurements, in the temperature range 10–300 K. The findings show that the normal-mode refinement method can be combined with an elaborate description of the electron density. It appears to be a promising technique for free-energy determination for crystalline materials at the expense of performing a single-crystal elastic X-ray diffraction determination combined with periodic DFT calculations.
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22

Dely, Alexandre, Francesco P. Andriulli et Kristof Cools. « An Impedance Boundary Condition EFIE That Is Low-Frequency and Refinement Stable ». IEEE Transactions on Antennas and Propagation 65, no 3 (mars 2017) : 1259–66. http://dx.doi.org/10.1109/tap.2016.2647684.

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23

Sage, J. Timothy. « Infrared Crystallography : Structural Refinement through Spectroscopy ». Applied Spectroscopy 51, no 4 (avril 1997) : 568–73. http://dx.doi.org/10.1366/0003702971940611.

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A method for determining the orientation of individual bonds within complex macromolecules from polarized IR measurements on oriented single crystals is described. At present, X-ray diffraction is the principal technique used to define the global structure and orientation of macromolecules in the crystalline state. However, resolution limitations and conformational disorder limit the accuracy of the resulting structural model. A quantitative understanding of protein function often requires a more precise description of structural features at a localized active site. Polarized IR measurements of internal stretching bands of N−3, CN−, OCN−, and SCN− bound at the ferric heme iron of single crystals of myoglobin are presented. A synthesis of such measurements on different crystal forms leads to an N−3 orientation consistent with IR measurements on both P21 and P212121 crystals, but significantly different from the orientation reported in X-ray crystal structures. Subtle structural changes between these two crystal forms of the CN− complex may account for small differences in the stretching frequency and orientation of the C–N bond.
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24

Wróbel, T., et J. Szajnar. « Modification of Pure Al and AlSi2 Alloy Primary Structure with Use of Electromagnetic Stirring Method ». Archives of Metallurgy and Materials 58, no 3 (1 septembre 2013) : 941–44. http://dx.doi.org/10.2478/amm-2013-0106.

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Abstract The paper presents modification of primary structure of Al 99,5% and 99,8% purity and AlSi2 alloy by electromagnetic stirring of liquid metal within foundry mould. The movement of solidifying liquid metal within the mould was forced by horizontal electromagnetic field produced by the induction coil (stirrer), supplied by current of elevated frequency. The structure refinement obtained by electromagnetic stirring was compared with refinement obtained by traditional modification, i.e. by introducing Ti, B, C and Sr modifying additives into melt. The results of studies show possibility of effective primary structure refinement of pure Al and selected Al-Si alloy by using only horizontal electromagnetic field, without necessity of Ti, B and C additives application.
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Chen, Banqiao, Chibiao Ding, Wenjuan Ren et Guangluan Xu. « Automatically Tracking Road Centerlines from Low-Frequency GPS Trajectory Data ». ISPRS International Journal of Geo-Information 10, no 3 (1 mars 2021) : 122. http://dx.doi.org/10.3390/ijgi10030122.

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High-quality digital road maps are essential prerequisites of location-based services and smart city applications. The massive and accessible GPS trajectory data generated by mobile GPS devices provide a new means through which to generate maps. However, due to the low sampling rate and multi-level disparity problems, automatically generating road maps is challenging and the generated maps cannot yet meet commercial requirements. In this paper, we present a GPS trajectory data-based road tracking algorithm, including an active contour-based road centerline refinement algorithm as the necessary post-processing. First, the low-frequency trajectory data were transferred into a density estimation map representing the roads through a kernel density estimator, for a seeding algorithm to automatically generate the initial points of the road-tracking algorithm. Then, we present a template-matching-based road-direction extraction algorithm for the road trackers to conduct simple correction, based on local density information. Last, we present an active contour-based road centerline refinement algorithm, considering both the geometric information of roads and density information. The generated road map was quantitatively evaluated using maps offered by the OpenStreetMap. Compared to other methods, our approach could produce a higher quality map with fewer zig-zag roads, and therefore more accurately represents reality.
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26

Xie, Jiuming, Dengyue Sun, Chengying Xu et Jin Wu. « The Influence of Finite Element Meshing Accuracy on a Welding Machine for Offshore Platform’S Modal Analysis ». Polish Maritime Research 25, s3 (1 décembre 2018) : 147–53. http://dx.doi.org/10.2478/pomr-2018-0124.

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Abstract The purpose objective of this study was to investigate the influence of finite element meshing accuracy on modal analysis which is one of the basic factors affecting the accuracy of finite element analysis and mostly preoccupies the working staff in pre-processing finite element simulation models. In this paper, we established several finite element models of a welding machine for offshore platform, with the meshing accuracy as the variable and workbench software as the platform for modal analysis, as the same time, comparing the analysis results. The results indicated that for some specific structures and simulation types, mesh refinement alone does not achieve desired results, and the authors indicate that mesh refinement is rarely related to the equipment’s low-frequency modal analysis but it’s great related to the equipment’s high-frequency modal analysis. The findings of this study may serve as breaking the opinion that smaller mesh size means higher calculation precision and provides references for mesh division practices in low frequency modal analysis.
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Zhang, Zhi Qiang, Qi Chi Le et Jian Zhong Cui. « Effect of Physical Fields on Solidification Structures of DC Casting AZ80 Magnesium Alloy Billets ». Applied Mechanics and Materials 105-107 (septembre 2011) : 1616–19. http://dx.doi.org/10.4028/www.scientific.net/amm.105-107.1616.

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AZ80 magnesium alloy was semi-continuously cast under different physical fields which were conventional direct chill (DC) casting, low frequency electromagnetic casting (LFEC), ultrasonic casting (USC) and electromagnetic-ultrasonic combined casting (ECUC), respectively. The effect of different physical fields on solidification structures of AZ80 alloys was investigated. The results show that compared with the conventional DC casting, structures of AZ80 alloys billets cast with LFEC and USC have been greatly refined. The effective refinement takes place in the edge of billets when LFEC is applied. However, the effective refinement takes place in the center of billets when USC is applied. When combination of low frequency electromagnetic and ultrasonic fields is applied during semi-continuous casting AZ80 magnesium alloy billet, structures of AZ80 alloys are refined significantly in the whole billets everywhere and more uniform.
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Avrin, Joel D. « Large-frequency global regularity for the incompressible Navier–Stokes equation ». Proceedings of the Royal Society of Edinburgh : Section A Mathematics 129, no 5 (1999) : 903–12. http://dx.doi.org/10.1017/s0308210500030997.

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We obtain global existence and regularity of strong solutions to the incompressible Navier–Stokes equations for a variety of boundary conditions in such a way that the initial and forcing data can be large in the high-frequency eigenspaces of the Stokes operator. We do not require that the domain be thin as in previous analyses. But in the case of thin domains (and zero Dirichlet boundary conditions) our results represent a further improvement and refinement of previous results obtained.
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29

Tan, Shui Lin, Quan Zhou, Jia Bin Fu et Hao Fu. « Grain Refinement of Mg97Y2Cu1 Alloy Solidified with Pulsed Direct Current Magnetic Field ». Advanced Materials Research 842 (novembre 2013) : 279–83. http://dx.doi.org/10.4028/www.scientific.net/amr.842.279.

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The influences of different pulse voltage, discharging frequency, pouring temperature and mold temperature on marostructure of Mg97Y2Cu1alloy under pulsed direct current magnetic field (PDCMF) were studied and the related mechanism was also discussed. The results show that grains of Mg97Y2Cu1alloy can be refined greatly by PDCMF treatment. Macrostructure of the alloy is changed from coarsened grains to complete fine equiaxed grains. When the pulse voltage is at 0-250V, grain size of the alloy decreases dramatically as pulse voltage increases. When the discharging frequency is at 1-10Hz, grain size of the alloy increases firstly, then decreases, and the turning point is 5 Hz. The change of grain size is not obvious, when the discharging frequency increases from 1 Hz to 5 Hz. When the discharging frequency reaches 10 Hz, the effect of grain refinement is the best. When the mold temperature is at 20-600°C or the pouring temperature is at 660-750°C, grain size of the alloy with PDCMF treatment decreases grossly with the increase of the mold temperature or the pouring temperature. The higher the pouring temperature or the mold temperature, the better the effect of grain refinement with PDCMF treatment.
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Kofoed, Phillip Miguel, Anna A. Hoser, Frederik Diness, Silvia C. Capelli et Anders Østergaard Madsen. « X-ray diffraction data as a source of the vibrational free-energy contribution in polymorphic systems ». IUCrJ 6, no 4 (8 mai 2019) : 558–71. http://dx.doi.org/10.1107/s2052252519003014.

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In this contribution we attempt to answer a general question: can X-ray diffraction data combined with theoretical computations be a source of information about the thermodynamic properties of a given system? Newly collected sets of high-quality multi-temperature single-crystal X-ray diffraction data and complementary periodic DFT calculations of vibrational frequencies and normal mode vectors at the Γ point on the yellow and white polymorphs of dimethyl 3,6-dichloro-2,5-dihydroxyterephthalate are combined using two different approaches, aiming to obtain thermodynamic properties for the two compounds. The first approach uses low-frequency normal modes extracted from multi-temperature X-ray diffraction data (normal coordinate analysis), while the other uses DFT-calculated low-frequency normal mode in the refinement of the same data (normal mode refinement). Thermodynamic data from the literature [Yang et al. (1989), Acta Cryst. B45, 312–323] and new periodic ab initio DFT supercell calculations are used as a reference point. Both approaches tested in this work capture the most essential features of the systems: the polymorphs are enantiotropically related, with the yellow form being the thermodynamically stable system at low temperature, and the white form at higher temperatures. However, the inferred phase transition temperature varies between different approaches. Thanks to the application of unconventional methods of X-ray data refinement and analysis, it was additionally found that, in the case of the yellow polymorph, anharmonicity is an important issue. By discussing contributions from low- and high-frequency modes to the vibrational entropy and enthalpy, the importance of high-frequency modes is highlighted. The analysis shows that larger anisotropic displacement parameters are not always related to the polymorph with the higher vibrational entropy contribution.
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Yoneda, Akira, Yoshitaka Aizawa, Md Mahbubar Rahman et Shunsuke Sakai. « High Frequency Resonant Ultrasound Spectroscopy to 50 MHz : Experimental Developments and Analytical Refinement ». Japanese Journal of Applied Physics 46, no 12 (6 décembre 2007) : 7898–903. http://dx.doi.org/10.1143/jjap.46.7898.

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32

Guo, Shijie, Qichi Le, Zhihao Zhao, Zhongjun Wang et Jianzhong Cui. « Microstructural refinement of DC cast AZ80 Mg billets by low frequency electromagnetic vibration ». Materials Science and Engineering : A 404, no 1-2 (septembre 2005) : 323–29. http://dx.doi.org/10.1016/j.msea.2005.05.070.

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33

Steurer, M., et W. Hribernik. « Frequency Response Characteristics of a 100 MJ SMES Coil—Measurements and Model Refinement ». IEEE Transactions on Appiled Superconductivity 15, no 2 (juin 2005) : 1887–90. http://dx.doi.org/10.1109/tasc.2005.849324.

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Wang, Yingxin, Xiaoqin Zeng, Wenjiang Ding, Alan A. Luo et Anil K. Sachdev. « Grain Refinement of AZ31 Magnesium Alloy by Titanium and Low-Frequency Electromagnetic Casting ». Metallurgical and Materials Transactions A 38, no 6 (26 juin 2007) : 1358–66. http://dx.doi.org/10.1007/s11661-007-9215-5.

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35

Lubich, L. « A Refinement of the Square Wave Phase Noise Evaluation ». Engineering, Technology & ; Applied Science Research 8, no 1 (20 février 2018) : 2361–66. http://dx.doi.org/10.48084/etasr.1733.

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Oscillators are often followed by square wave forming circuits and frequency dividers. Traditionally, the level of the phase noise, transferred from the oscillator outputs to the square waves obtained is calculated ignoring the correlations in the oscillator phase noise spectrum. In this paper, accurate expressions are derived, taking into account the phase noise mechanisms in the oscillators. The phase noise power spectral densities are calculated in both the traditional way and by using the proposed expressions and they are compared. The situations where the proposed expressions can be useful are identified.
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36

Hoser, Anna A., Marcin Sztylko, Damian Trzybiński et Anders Ø. Madsen. « Theoretically derived thermodynamic properties can be improved by the refinement of low-frequency modes against X-ray diffraction data ». Chemical Communications 57, no 74 (2021) : 9370–73. http://dx.doi.org/10.1039/d1cc02608a.

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Herein, a framework for the estimation of the thermodynamic properties of molecular crystals via the refinement of frequencies from density functional theory calculations against X-ray diffraction data is presented.
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37

Xiang, Jing Zhong, Hui Zhu, Meng Jin Gao, Fang Jian Chen, Xian Jiang Shi et Yan Ling Zhao. « EMD and Zoom Envelope Spectrum for Rolling Bearing Fault Diagnosis ». Advanced Materials Research 791-793 (septembre 2013) : 841–44. http://dx.doi.org/10.4028/www.scientific.net/amr.791-793.841.

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ntrinsic mode function component (IMF) has been effectively decomposed by using empirical mode (EMD) decomposition method, and the high-frequency resonance frequency band the rolling bearing components is extracted. Then the high frequency component of the IMF is shifted to the lower frequency by using real frequency modulation principle, and a new envelope refining spectrum is obtained through the Hilbert transform after low frequency sampling. The method not only simplifies the design of band-pass filtering process but improves refinement computational efficiency of the envelope spectrum. The method verifies the correctness of the theory and practical method through the analysis of the fault diagnosis of rolling bearing inner ring experiment.
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38

Levis, Nicholas A., et David W. Pfennig. « Plasticity-led evolution : evaluating the key prediction of frequency-dependent adaptation ». Proceedings of the Royal Society B : Biological Sciences 286, no 1897 (27 février 2019) : 20182754. http://dx.doi.org/10.1098/rspb.2018.2754.

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Plasticity-led evolution occurs when a change in the environment triggers a change in phenotype via phenotypic plasticity, and this pre-existing plasticity is subsequently refined by selection into an adaptive phenotype. A critical, but largely untested prediction of plasticity-led evolution (and evolution by natural selection generally) is that the rate and magnitude of evolutionary change should be positively associated with a phenotype's frequency of expression in a population. Essentially, the more often a phenotype is expressed and exposed to selection, the greater its opportunity for adaptive refinement. We tested this prediction by competing against each other spadefoot toad tadpoles from different natural populations that vary in how frequently they express a novel, environmentally induced carnivore ecomorph. As expected, laboratory-reared tadpoles whose parents were derived from populations that express the carnivore ecomorph more frequently were superior competitors for the resource for which this ecomorph is specialized—fairy shrimp. These tadpoles were better at using this resource both because they were more efficient at capturing and consuming shrimp and because they produced more exaggerated carnivore traits. Moreover, they exhibited these more carnivore-like features even without experiencing the inducing cue, suggesting that this ecomorph has undergone an extreme form of plasticity-led evolution—genetic assimilation. Thus, our findings provide evidence that the frequency of trait expression drives the magnitude of adaptive refinement, thereby validating a key prediction of plasticity-led evolution specifically and adaptive evolution generally.
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39

Pienkowski, Martin, et Robert V. Harrison. « Tone Frequency Maps and Receptive Fields in the Developing Chinchilla Auditory Cortex ». Journal of Neurophysiology 93, no 1 (janvier 2005) : 454–66. http://dx.doi.org/10.1152/jn.00569.2004.

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Single-unit responses to tone pip stimuli were isolated from numerous microelectrode penetrations of auditory cortex (under ketamine anesthesia) in the developing chinchilla ( laniger), a precocious mammal. Results are reported at postnatal day 3 (P3), P15, and P30, and from adult animals. Hearing sensitivity and spike firing rates were mature in the youngest group. The topographic representation of sound frequency (tonotopic map) in primary and secondary auditory cortex was also well ordered and sharply tuned by P3. The spectral-temporal complexity of cortical receptive fields, on the other hand, increased progressively (past P30) to adulthood. The (purported) refinement of initially diffuse tonotopic projections to cortex thus seems to occur in utero in the chinchilla, where external (and maternal) sounds are considerably attenuated and might not contribute to the mechanism(s) involved. This compares well with recent studies of vision, suggesting that the refinement of the retinotopic map does not require external light, but rather waves of (correlated) spontaneous activity on the retina. In contrast, it is most probable that selectivity for more complex sound features, such as frequency stacks and glides, develops under the influence of the postnatal acoustic environment and that inadequate sound stimulation in early development (e.g., due to chronic middle ear disease) impairs the formation of the requisite intracortical (and/or subcortical) circuitry.
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40

Wang, Fuyue, Xiangjie Wang et Jianzhong Cui. « Effect of Low-Frequency Electromagnetic Casting on Micro-Structure and Macro-Segregation of 5A90 Alloy Ingots ». Materials 13, no 12 (15 juin 2020) : 2720. http://dx.doi.org/10.3390/ma13122720.

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The effect of low-frequency electromagnetic fields on the micro-structure and macro-segregation of 5A90 alloy ingots during the semi-continuous casting process were quantitatively investigated. The ingots of a 5A90 alloy with a diameter 170 mm were produced by the conventional direct chill casting (DCC) process and low-frequency electromagnetic casting (LFEC) with 10 Hz/100 A. The results showed that LFEC can substantially refine the micro-structure and shorten the width of the columnar grain area of an ingot. The refinement effect came with the relieving of grain boundary segregation and an improvement in the macro-segregation of the ingot. Compared with the traditional DCC process, the tensile properties of the aged alloy prepared by the LFEC process were improved due to the effects of the increase in solid solubility and the strengthening of the grain refinement, so that the stability of the tensile properties was also improved. Meanwhile, the rate of yield increased by 2.3% with a decrease in the peeling thickness of the ingot.
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41

Wang, Yang, Yibin Yao, Liang Zhang et Mingshan Fang. « A Refinement Method of Real-Time Ionospheric Model for China ». Remote Sensing 12, no 20 (14 octobre 2020) : 3354. http://dx.doi.org/10.3390/rs12203354.

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Ionospheric delay is a crucial error source and determines the source of single-frequency precise point positioning (SF-PPP) accuracy. To meet the demands of real-time SF-PPP (RT-SF-PPP), several international global navigation satellite systems (GNSS) service (IGS) analysis centers provide real-time global ionospheric vertical total electron content (VTEC) products. However, the accuracy distribution of VTEC products is nonuniform. Proposing a refinement method is a convenient means to obtain a more accuracy and consistent VTEC product. In this study, we proposed a refinement method of a real-time ionospheric VTEC model for China and carried out experiments to validate the model effectiveness. First, based on the refinement method and the Centre National d’Études Spatiales (CNES) VTEC products, three refined real-time global ionospheric models (RRTGIMs) with one, three, and six stations in China were built via GNSS observations. Second, the slant total electron content (STEC) and Jason-3 VTEC were used as references to evaluate VTEC accuracy. Third, RT-SF-PPP was used to evaluate the accuracy in the positioning domain. Results showed that even if using only one station to refine the global ionospheric model, the refined model achieved a better performance than CNES and the Center for Orbit Determination in Europe (CODE). The refinement model with six stations was found to be the best of the three refinement models.
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42

Wróbel, Tomasz. « Transformation of Pure Al Structure under the Influence of Electromagnetic Field ». Advanced Materials Research 702 (mai 2013) : 159–64. http://dx.doi.org/10.4028/www.scientific.net/amr.702.159.

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In paper problem concerning inoculation of primary structure of aluminum with purity of 99,5% and 99,8%, which is realized mainly by intensification of liquid metal movement in mould is presented. In aim of realization of forced movement during the crystallization of liquid metal was used rotating electromagnetic field produced by the induction coil supplied by current with elevated frequency. The degree of structure refinement was represented by equiaxed crystals zone content on transverse section of ingot and average area of macro-grain in this zone. Effect of structure refinement obtained by influence of electromagnetic field was compared with refinement obtained by use of traditional inoculation, which consists in introducing of additives i.e. titanium, boron and carbon to metal bath. The results of studies and their analysis show possibility of effective refinement of pure Al primary structure, only with use of rotating electromagnetic field and without necessity of application of inoculants such a Ti, B and C. This method of inoculation is important, because inoculants decrease the degree of purity and electrical conductivity of pure Al. Moreover Ti and B are reason of point cracks formation during rolling of ingots.
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43

Wróbel, Tomasz. « The Influence of Electromagnetic Stirring on Primary Structure of Pure Al and Al-Si Alloy ». Advanced Materials Research 746 (août 2013) : 478–83. http://dx.doi.org/10.4028/www.scientific.net/amr.746.478.

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In paper problem concerning inoculation of primary structure of Al with purity of 99,5% and 99,8% and AlSi2 alloy, which is realized mainly by intensification of liquid metal movement in mould is presented. In aim of realization of forced movement during the crystallization of liquid metal was used horizontal electromagnetic field produced by the induction coil (stirrer) supplied by current with elevated frequency. The degree of structure refinement was represented mainly by equiaxed crystals zone content on transverse section of ingot and average area of macro-grain in this zone. Effect of structure refinement obtained by influence of electromagnetic stirring was compared with refinement obtained by use of traditional inoculation, which consists in introducing of additives i.e. titanium, boron and strontium to metal bath. The results of studies and their analysis show possibility of effective refinement of pure Al and Al-Si alloy primary structure, only with use of horizontal electromagnetic field and without necessity of application of inoculants such a Ti and B. This method of inoculation is important, because inoculants decrease the degree of purity and electrical conductivity of pure Al. Moreover inoculants are reason of point cracks formation during rolling of ingots.
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44

Chernyshov, Dmitry, Wouter van Beek, Hermann Emerich, Marco Milanesio, Luca Palin, Rocco Caliandro et Atsushi Urakawa. « Getting More from Powder Diffraction Experiment : Modulation-Enhanced Diffraction ». Acta Crystallographica Section A Foundations and Advances 70, a1 (5 août 2014) : C132. http://dx.doi.org/10.1107/s2053273314098672.

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Introducing a periodic perturbation of structural parameters of a given frequency results in a modulated diffraction response that may have a complex frequency spectrum. Frequency analysis of the diffraction signal allows untangling contributions from the average and varying part of the scattering density as well as interference between them; both model and real proof-of principal experiments will be discussed. An analysis of advantages and drawbacks of the modulation approach will be given together with new opportunities for structure determination and refinement offered by MED for powder diffraction experiments with synchrotron radiation.
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45

Wesling, Volker, Antonia Schram et Henning Wiche. « Investigation of the Process- and System-Induced Activation of Material Reactions during Discontinuous High-Frequency Welding ». Advanced Materials Research 137 (octobre 2010) : 247–93. http://dx.doi.org/10.4028/www.scientific.net/amr.137.247.

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Besides weldable component geometries for the high-frequency welding process also possible process and system induced activated material reactions during discontinuous high-frequency welding are presented in this paper. Among others such material reactions can be a locally limited thermal influence on the base metal, defined plastic derformations during the upsetting process as well as grain refinement in the weld seam, comparable to thermomechanical treatment during rolling for increasing strength or ductility.
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46

Wang, Xiang Jie, Fang Yu, Peng Wei Li, Wei Sun, Hong Juan Tan, Lei Li et Jian Zhong Cui. « Effects of Electromagnetic Agitation on Crystal Growth during the Pure Aluminum Slow Cooling Process ». Materials Science Forum 993 (mai 2020) : 398–403. http://dx.doi.org/10.4028/www.scientific.net/msf.993.398.

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Refining grains are important to obtain sound cast billets suitable for further processing. The structure refinement of low frequency electromagnetic field (LFEF) during the aluminum alloy semi-continuous casting process has been confirmed by many researchers. In this work, effects of the electromagnetic agitation on the crystal growth were investigated during the pure aluminum slow cooling process. The results showed that the grain refinement effect by electromagnetic agitation mainly occurred at the first half period of crystal growth. With increasing of applying LFEF treated time, the fine grain occupied the whole section of ingot, and the ratio of fine grain zone to the whole section was proportional to the treated time.
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Mizutani, Yoshiki, Takuya Tamura et Kenji Miwa. « Effect of Electromagnetic Vibration Frequency and Temperature Gradient on Grain Refinement of Pure Aluminum ». MATERIALS TRANSACTIONS 48, no 3 (2007) : 538–43. http://dx.doi.org/10.2320/matertrans.48.538.

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Guo, Jing, Yong Zhou, Changmeng Liu, Qianru Wu, Xianping Chen et Jiping Lu. « Wire Arc Additive Manufacturing of AZ31 Magnesium Alloy : Grain Refinement by Adjusting Pulse Frequency ». Materials 9, no 10 (9 octobre 2016) : 823. http://dx.doi.org/10.3390/ma9100823.

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Geza, V., J. Vencels, G. Zageris et S. Pavlovs. « Numerical study of surface waves generated by low frequency EM field for silicon refinement ». IOP Conference Series : Materials Science and Engineering 424 (13 octobre 2018) : 012049. http://dx.doi.org/10.1088/1757-899x/424/1/012049.

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Barchanski, A., T. Steiner, H. De Gersem, M. Clemens et T. Weiland. « Local grid refinement for low-frequency current computations in 3-D human anatomy models ». IEEE Transactions on Magnetics 42, no 4 (avril 2006) : 1371–74. http://dx.doi.org/10.1109/tmag.2006.871449.

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