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Academic literature on the topic 'Stochastic gratient'

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Published: 25 May 2024

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Journal articles on the topic "Stochastic gratient"

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Li, Huiyan. "A Novel Machine Translation Method based on Stochastic Finite Automata Model for Spoken English." International Journal of Emerging Technologies in Learning (iJET) 14, no. 06 (March 29, 2019): 98. http://dx.doi.org/10.3991/ijet.v14i06.10161.

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Stochastic finite automata have been applied to a variety of fields, machine trans-lation is one of them. It can learn from data and build model automatically from training sets. Stochastic finite automata are well adapted for the constrained inte-gration of pairs of sentences for language processing. In this paper, a novel ma-chine translation method based on stochastic finite automata is proposed. The method formalized rational grammars by using stochastic finite automata. Through given pairs of source and target utterances, our proposed method will produce a series of conventional rules from which a stochastic rational grammar would be inferred, and the grammar is finally converted into a finite state automa-ton. The efficacy and accuracy of our proposed method is evaluated by a large number of English-Chinese and Chinese-English machine translation experi-ments.
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Solomon, Joshua A., and Michael J. Morgan. "Stochastic re-calibration: contextual effects on perceived tilt." Proceedings of the Royal Society B: Biological Sciences 273, no. 1601 (July 11, 2006): 2681–86. http://dx.doi.org/10.1098/rspb.2006.3634.

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The human visual system exaggerates the difference between the tilts of adjacent lines or grating patches. In addition to this tilt illusion, we found that oblique flanks reduced acuity for small changes of tilt in the centre of the visual field. However, no flanks—regardless of their tilts—decreased sensitivity to contrast. Thus, the foveal tilt illusion should not be attributed to orientation-selective lateral inhibition. Nor is it similar to conventional crowding, which typically does not impair letter recognition in the fovea. Our observers behaved as though the reference orientation (horizontal) had a small tilt in the direction of the flanks. We suggest that the extent of this re-calibration varies randomly over trials, and we demonstrate that this stochastic re-calibration can explain flank-induced acuity loss in the fovea.
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von Martens, Hans-Jürgen. "Investigations into the Uncertainties of Interferometric Measurements of Linear and Circular Vibrations." Shock and Vibration 4, no. 5-6 (1997): 327–40. http://dx.doi.org/10.1155/1997/183527.

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A uniform description is given of a method of measurement using a Michelson interferometer for measuring the linear motion quantities acceleration, velocity and displacement, and a diffraction grating interferometer for measuring the circular motion quantities angular acceleration, angular velocity and rotation angle. The paper focusses on an analysis of the dynamic behaviour of an interferometric measurement system based on the counting technique with regard to the measurement errors due to deterministic and stochastic disturbing quantities. The error analysis and description presented are aimed at giving some rules, mathematical expressions and graphical presentations that have proved to be helpful in recognizing the errors in interferometric measurements of motion quantities, optimizing the measurement conditions (e.g., filter settings), obtaining corrections and estimating the uncertainty of measurement.
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Juan, M. L., J. Plain, R. Bachelot, P. Royer, S. K. Gray, and G. P. Wiederrecht. "Stochastic model for photoinduced surface relief grating formation through molecular transport in polymer films." Applied Physics Letters 93, no. 15 (October 13, 2008): 153304. http://dx.doi.org/10.1063/1.2999625.

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Bai, Ping, Mohamed S. Abdelkhalik, Diogo G. A. Castanheira, and Jaime Gómez Rivas. "Evolutionary optimization of the short-circuit current enhancement in organic solar cells by nanostructured electrodes." Journal of Applied Physics 132, no. 15 (October 21, 2022): 153103. http://dx.doi.org/10.1063/5.0097964.

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Using a particle swarm optimization algorithm (a population-based stochastic optimization technique) combined with 3D finite-difference time-domain simulations, we inverse design periodic arrays of metallic nanoparticles on indium-tin-oxide electrodes and nanoholes in metallic thin films working as electrodes in P3HT (Poly(3-hexylthiophene-2,5-diyl)):PCBM ([6,6]-Phenyl C61 butyric acid methyl ester) organic solar cells to achieve the maximum short-circuit currents ([Formula: see text]). Nanohole-array electrodes have large optical losses, leading to a net reduction of [Formula: see text] compared to a reference solar cell. On the other hand, nanoparticle arrays can lead to a significant enhancement of [Formula: see text] of up to 20%. Detailed simulations show that this enhancement is caused by the grating coupling of the incident light to surface plasmon polaritons at the interface of the metal electrode and the hole transport layer, leading to the enhancement of the electromagnetic field in the organic blend.
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Zhao, Long, Xinbo Huang, Jianyuan Jia, Yongcan Zhu, and Wen Cao. "Detection of Broken Strands of Transmission Line Conductors Using Fiber Bragg Grating Sensors." Sensors 18, no. 7 (July 23, 2018): 2397. http://dx.doi.org/10.3390/s18072397.

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Transmission lines are affected by Aeolian vibration, which causes strands to break and eventually causes an entire line to break. In this paper, a method for monitoring strand breaking based on modal identification is proposed. First, the natural frequency variation of a conductor caused by strand breakage is analyzed, and a modal experiment of the LGJ-95/15 conductor is conducted. The measurement results show that the natural frequencies of the conductor decrease with an increasing number of broken strands. Next, a monitoring system incorporating a fiber Bragg grating (FBG)-based accelerometer is designed in detail. The FBG sensor is mounted on the conductor to measure the vibration signal. A wind speed sensor is used to measure the wind speed signal and is installed on the tower. An analyzer is also installed on the tower to calculate the natural frequencies, and the data are sent to the monitoring center via 3G. Finally, a monitoring system is tested on a 110 kV experimental transmission line, and the short-time Fourier transform (STFT) method and stochastic subspace identification (SSI) method are used to identify the natural frequencies of the conductor vibration. The experimental results show that SSI analysis provides a higher precision than does STFT and can extract the natural frequency under various wind speeds as an effective basis for discriminating between broken strands.
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SHINOHARA, N., B. SHISHKOV, H. MATSUMOTO, K. HASHIMOTO, and A. K. M. BAKI. "New Stochastic Algorithm for Optimization of Both Side Lobes and Grating Lobes in Large Antenna Arrays for MPT." IEICE Transactions on Communications E91-B, no. 1 (January 1, 2008): 286–96. http://dx.doi.org/10.1093/ietcom/e91-b.1.286.

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Wu, G., and Y. Cai. "Polarization ellipse and Stokes parameters of a stochastic electromagnetic Gaussian Schell-model beam propagating through a polarization grating." Applied Physics B 105, no. 4 (July 8, 2011): 893–907. http://dx.doi.org/10.1007/s00340-011-4607-z.

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Li, Sheng, Liang Jin, Jinpeng Jiang, Honghai Wang, Qiuming Nan, and Lizhi Sun. "Looseness Identification of Track Fasteners Based on Ultra-Weak FBG Sensing Technology and Convolutional Autoencoder Network." Sensors 22, no. 15 (July 28, 2022): 5653. http://dx.doi.org/10.3390/s22155653.

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Changes in the geological environment and track wear, and deterioration of train bogies may lead to the looseness of subway fasteners. Identifying loose fasteners randomly distributed along the subway line is of great significance to avoid train derailment. This paper presents a convolutional autoencoder (CAE) network-based method for identifying fastener loosening features from the distributed vibration responses of track beds detected by an ultra-weak fiber Bragg grating sensing array. For an actual subway tunnel monitoring system, a field experiment used to collect the samples of fastener looseness was designed and implemented, where a crowbar was used to loosen or tighten three pairs of fasteners symmetrical on both sides of the track within the common track bed area and the moving load of a rail inspection vehicle was employed to generate 12 groups of distributed vibration signals of the track bed. The original vibration signals obtained from the on-site test were converted into two-dimensional images through the pseudo-Hilbert scan to facilitate the proposed two-stage CAE network with acceptable capabilities in feature extraction and recognition. The performance of the proposed methodology was quantified by accuracy, precision, recall, and F1-score, and displayed intuitively by t-distributed stochastic neighbor embedding (t-SNE). The raster scan and the Hilbert scan were selected to compare with the pseudo-Hilbert scan under a similar CAE network architecture. The identification performance results represented by the four quantification indicators (accuracy, precision, recall, and F1-score) based on the scan strategy in this paper were at least 23.8%, 9.5%, 20.0%, and 21.1% higher than those of the two common scan methods. As well as that, the clustering visualization by t-SNE further verified that the proposed approach had a stronger ability in distinguishing the feature of fastener looseness.
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Plock, Matthias, Martin Hammerschmidt, Sven Burger, Philipp-Immanuel Schneider, and Christof Schutte. "Impact study of numerical discretization accuracy on parameter reconstructions and model parameter distributions." Metrologia, July 6, 2023. http://dx.doi.org/10.1088/1681-7575/ace4cd.

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Abstract In optical nano metrology numerical models are used widely for parameter reconstructions. Using the Bayesian target vector optimization method we fit a finite element numerical model to a Grazing Incidence X-Ray fluorescence data set in order to obtain the geometrical parameters of a nano structured line grating. Gaussian process, stochastic machine learning surrogate models, were trained during the reconstruction and afterwards sampled with a Markov chain Monte Carlo sampler to determine the distribution of the reconstructed model parameters. The numerical discretization parameters of the used finite element model impact the numerical discretization error of the forward model. We investigated the impact of the polynomial order of the finite element ansatz functions on the reconstructed parameters as well as on the model parameter distributions. We showed that such a convergence study allows to determine numerical parameters which allows for efficient and accurate reconstruction results.
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Dissertations / Theses on the topic "Stochastic gratient"

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Koroko, Abdoulaye. "Natural gradient-based optimization methods for deep neural networks." Electronic Thesis or Diss., université Paris-Saclay, 2023. http://www.theses.fr/2023UPASG068.

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La méthode du gradient stochastique est la technologie actuellement prédominante pour effectuer la phase d'entraînement des réseaux de neurones. Par rapport à une descente classique, le calcul du vrai gradient comme une moyenne sur les données est remplacé par un élément aléatoire de la somme. En présence de données massives, cette approximation audacieuse permet de diminuer le nombre d'évaluations de gradients élémentaires et d'alléger le coût de chaque itération. Le prix à payer est l'apparition d'oscillations et la lenteur de convergence souvent excessive en nombre d'itérations. L'objectif de cette thèse est de concevoir une approche à la fois : (i) plus robuste, en faisant appel aux méthodes fondamentales qui ont fait leur preuve en optimisation classique, i.e., en dehors du cadre de l'apprentissage ; et (ii) plus rapide, en termes de vitesse convergence. Nous nous intéressons en particulier aux méthodes de second ordre, connues pour leur stabilité et leur rapidité de convergence. Pour éviter le goulot d'étranglement de ces méthodes, qui est le coût exorbitant d'une itération où intervient un système linéaire à matrice pleine, nous tentons d'améliorer une approximation récemment introduite sous le nom de Kronecker-Factorized Approximation of Curvature (KFAC) pour la matrice de Fisher, laquelle remplace la matrice hessienne dans ce contexte. Plus précisément, nos axes de travail sont : (i) construire de nouvelles factorisations de Kronecker fondées sur une justification mathématique plus rigoureuse que KFAC ; (ii) prendre en compte l'information issue des blocs hors diagonaux de la matrice de Fisher, qui représentent l'interaction entre les différentes couches ; (iii) généraliser KFAC à une architecture de réseau autre que celles pour lesquelles elle a été initialement développée
The stochastic gradient method is currently the prevailing technology for training neural networks. Compared to a classical descent, the calculation of the true gradient as an average over the data is replaced by a random element of the sum. When dealing with massive data, this bold approximation enables one to decrease the number of elementary gradient evaluations and to alleviate the cost of each iteration. The price to be paid is the appearance of oscillations and the slowness of convergence, which is often excessive in terms of number of iterations. The aim of this thesis is to design an approach that is both: (i) more robust, using the fundamental methods that have been successfully proven in classical optimization, i.e., outside the learning framework; and (ii) faster in terms of convergence speed. We are especially interested in second-order methods, known for their stability and speed of convergence. To circumvent the bottleneck of these methods, which lies in the prohibitive cost of an iteration involving a linear system with a full matrix, we attempt to improve an approximation recently introduced as Kronecker-Factorized Approximation of Curvature (KFAC) for the Fisher matrix, which replaces the Hessian matrix in this context. More specifically, our work focuses on: (i) building new Kronecker factorizations based on a more rigorous mathematical justification than in KFAC; (ii) taking into account the information from the off-diagonal blocks of the Fisher matrix, which represent the interaction between the different layers; (iii) generalizing KFAC to a network architecture other than those for which it had been initially developed
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Conference papers on the topic "Stochastic gratient"

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Glabisch, Sven, Sophia Schröder, Sascha Brose, Henning Heiming, Jochen Stollenwerk, and Carlo Holly. "Investigation of stochastic roughness effects for nanoscale grating characterization with a stand-alone EUV spectrometer." In Photomask Technology 2022, edited by Bryan S. Kasprowicz and Ted Liang. SPIE, 2022. http://dx.doi.org/10.1117/12.2641625.

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Mukamel, Shaul, Zhifang Deng, and Roger F. Loring. "Time-Domain And Frequency-Domain Four-Wave Mixing; A Unified Stochastic Approach." In International Conference on Ultrafast Phenomena. Washington, D.C.: Optica Publishing Group, 1986. http://dx.doi.org/10.1364/up.1986.thc7.

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A microscopic theory is developed for time-domain and frequency-domain four-wave mixing of polyatomic molecules in condensed phases. The nonlinear response function R(t3,t2,t1) is expressed in terms of the four-point correlation function of the dipole operator F(τ1, τ2, τ3, τ4) and is evaluated explicitly for a stochastic Langevin model of line broadening which holds for any correlation time of the solvent. Our results interpolate between the fast modulation limit, in which the optical Bloch equations are valid, and the static limit of inhomogeneous line broadening. Green function techniques are developed and used to perform the necessary summations over the vibronic manifolds required in the calculation of nonlinear susceptibilities in harmonic polyatomic molecules. Application is made to the calculation of excitation profiles of ground state CARS, excited state CARS, and incoherent Raman scattering of large polyatomic molecules in solution. The use of picosecond CARS as a probe for vibrational dephasing in liquids will be analyzed. In addition, a frequency-domain analogue of the transient grating experiment is developed. It is shown that degenerate four-wave mixing provides a sensitive probe for exciton dynamics (coherent, incoherent, and localized).
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Mait, Joseph N. "Complex plane representation and design of array generators." In OSA Annual Meeting. Washington, D.C.: Optica Publishing Group, 1991. http://dx.doi.org/10.1364/oam.1991.wa3.

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The development of free-space optical interconnect systems has created a need for efficient algorithms for the design of multiple beam splitting optical elements commonly referred to as array generators. A technique for the design of continuous phase gratings is presented that is based on the representation of the array generator in terms of complex poles and zeroes. Infinite impulse response filter design theory is then applied to array generator design; an all-pass IIR filter insures that the phase-only constraint is always satisfied. A stochastic optimization algorithm is presented that is based on the specification of complex poles and zeroes. Preliminary results indicate the efficacy of using IIR filter design techniques, but grating performance to date is only moderate. Phase gratings have been designed that generate spot arrays at ~90% diffraction efficiency with 7% uniformity.
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Fourkas, John T., Rick Trebino, M. D. Fayer, and Mark A. Dugan. "Extra Resonances in Time-Domain Nonlinear Spectroscopies." In Nonlinear Optics. Washington, D.C.: Optica Publishing Group, 1992. http://dx.doi.org/10.1364/nlo.1992.tud2.

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Extra resonances between initially unpopulated excited states (IUES) or equally populated ground states (EPGS) have been studied extensively in the context of frequency-domain nonlinear spectroscopies such as Nearly-Degenerate Four-Wave Mixing (NDFWM)1. In the absence of strong laser fields2 or effects such as pure dephasing3, stochastic fluctuations in laser fields4, and laser transients5, the NDFWM extra resonances are either very weak (in the case of EPGS) or nonexistent (in the case of IUES). It is perhaps under-appreciated that "Fourier-transform" time- and frequency-domain FWM techniques do not necessarily provide the same information. For instance, under certain circumstances6, the NDFWM and transient grating (TG) techniques form such a pair, which would imply that TG extra resonances might disappear under the same experimental conditions in which they disappear in NDFWM. This assumption is belied by the TG data shown in Fig. 1. These data were taken by exciting and probing the D1 line of Na atoms in a cell in which there was no buffer gas and the Na pressure was low enough to preclude any significant number Na-Na collisions on the experimental time scale. Even in the absence of pressure-induced dephasing, these data exhibit strong extra resonances at both the 1.77-GHz ground-state hyperfine-splitting frequency and the 189-MHz excited-state hyperfine-splitting frequency. These data have prompted us to undertake a theoretical study of the nature of extra resonances in time-domain nonlinear spectroscopies, the preliminary results of which are discussed here. We show that time-domain extra resonances increase in strength with decreasing dephasing, and that IUES resonances exist even in the complete absence of pure dephasing. Finally, we show that IUES and EPGS extra resonances have a common origin in the time domain.
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