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2025 IEEE International Conference on Acoustics, Speech, and Signal Processing, ICASSP 2025

作者： Simantiraki, Olympia Markaki, Maria Pantazis, Yannis Institute of Applied and Computational Mathematics Foundation for Research and Technology Hellas Greece

ISBN: (纸本)9798350368741

Synthetic speech is occasionally required to be enhanced by a fixed amount before being presented to the listener. However, this approach neglects the diverse types and levels of noise, potentially resulting in either unintelligible or unpleasant speech. This paper proposes a dynamic speech enhancement approach, which generates speech while accounting for the presence of noise. Our methodology extends the WaveRNN vocoder by conditioning not only the speech mel-spectrograms but also the spectrogram from the background noise. In training, the target speech is tilted according to the listeners' preference and we further introduce an objective metric that aims at maximizing the spectro-temporal regions where target energy exceeds the masker energy. The generated speech was tested in speech-shaped noise at various noise levels. Our evaluation results showed that (a) in more adverse conditions, both a fixed-amount post-enhanced baseline system and the suggested dynamically-enhanced system performed equally well in terms of intelligibility and preference and (b) in the least noisy conditions, where the intelligibility scores of all models were nearly identical, listeners preferred the dynamically-enhanced speech. Our findings demonstrate and reinforce the benefits of using dynamic speech enhancement techniques in noisy environments. © 2025 IEEE.

关键词： dynamic adaptation noise-aware synthesis speech enhancement Speech synthesis

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Phase-field simulations of the effect of temperature and interface for zirconiumδ-hydrides

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Chinese Physics B 2024年第4期33卷 701-710页

作者：陈子航盛杰刘瑜施小明黄厚兵许可王越超武帅孙博刘海风宋海峰 School of Materials Science and Engineering Beijing Institute of TechnologyBeijing 100081China Advanced Research Institute of Multidisciplinary Science Beijing Institute of TechnologyBeijing 100081China Laboratory of Computational Physics Institute of Applied Physics and Computational MathematicsBeijing 100088China Department of Physics University of Science and Technology BeijingBeijing 100083China

Hydride precipitation in zirconium cladding materials can damage their integrity and *** temperature and material defects have a significant effect on the dynamic growth of *** this study,we have developed a phasefield model based on the assumption of elastic behaviour within a specific temperature range(613 K-653 K).This model allows us to study the influence of temperature and interfacial effects on the morphology,stress,and average growth rate of zirconium *** results suggest that changes in temperature and interfacial energy influence the length-to-thickness ratio and average growth rate of the hydride *** ultimate determinant of hydride orientation is the loss of interfacial coherency,primarily induced by interfacial dislocation defects and quantifiable by the mismatch degree *** escalation in interfacial coherency loss leads to a transition of hydride growth from horizontal to vertical,accompanied by the onset of redirection ***,redirection occurs at a critical mismatch level,denoted as qc,and remains unaffected by variations in temperature and interfacial ***,this redirection leads to an increase in the maximum stress,which may influence the direction of hydride crack *** research highlights the importance of interfacial coherency and provides valuable insights into the morphology and growth kinetics of hydrides in zirconium alloys.

关键词： zirconium hydride phase-field method temperature effect mismatch degree

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A Composite Ansatz for Calculation of Dynamical Structure Factor

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Chinese Physics Letters 2024年第1期41卷 92-103页

作者：张玉佩莫崇杰张平康炜 HEDPS Center for Applied Physics and Technologyand School of PhysicsPeking UniversityBeijing 100871China Beijing Computational Science Research Center Beijing 100193China Institute of Applied Physics and Computational Mathematics Beijing 100088China HEDPS Center for Applied Physics and Technologyand College of EngineeringPeking UniversityBeijing 100871China

We propose an ansatz without adjustable parameters for the calculation of a dynamical structure *** ansatz combines the quasi-particle Green’s function,especially the contribution from the renormalization factor,and the exchange-correlation kernel from time-dependent density functional theory together,verified for typical metals and semiconductors from a plasmon excitation regime to the Compton scattering *** has the capability to reconcile both small-angle and large-angle inelastic x-ray scattering(IXS)signals with muchimproved accuracy,which can be used as the theoretical base model,in inversely inferring electronic structures of condensed matter from IXS experimental signals *** may also be used to diagnose thermal parameters,such as temperature and density,of dense plasmas in x-ray Thomson scattering experiments.

关键词： excitation inverse verified

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Dynamic mode decomposition of nonequilibrium electron-phonon dynamics:accelerating the firstprinciples real-time Boltzmann equation

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npj computational Materials 2024年第1期10卷 1970-1977页

作者： Ivan Maliyov Jia Yin Jia Yao Chao Yang Marco Bernardi Department of Applied Physics and Materials Science California Institute of TechnologyPasadenaCA 91125USA Applied Mathematics and Computational Research Division Lawrence Berkeley National LaboratoryBerkeleyCA 94720USA Department of Physics California Institute of TechnologyPasadenaCA 91125USA

Nonequilibrium dynamics governed by electron–phonon(e-ph)interactions plays a key role in electronic devices and spectroscopies and is central to understanding electronic excitations in *** real-time Boltzmann transport equation(rt-BTE)with collision processes computed from first principles can describe the coupled dynamics of electrons and atomic vibrations(phonons).Yet,a bottleneck of these simulations is the calculation of e–ph scattering integrals on dense momentum grids at each time *** we show a data-driven approach based on dynamic mode decomposition(DMD)that can accelerate the time propagation of the rt-BTE and identify dominant electronic *** apply this approach to two case studies,high-field charge transport and ultrafast excited electron *** both cases,simulating only a short time window of~10%of the dynamics suffices to predict the dynamics from initial excitation to steady state using DMD *** of the momentum-space modes extracted from DMD sheds light on the microscopic mechanisms governing electron relaxation to a steady state or *** combination of accuracy and efficiency makes our DMD-based method a valuable tool for investigating ultrafast dynamics in a wide range of materials.

关键词： materials dynamics phonon

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Sub-pixel Material Fraction Mapping in the UrbanScape using PRISMA Hyperspectral Imagery

Sub-pixel Material Fraction Mapping in the UrbanScape using ...

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2023 Joint Urban Remote Sensing Event, JURSE 2023

作者： Poursanidis, Dimitris Panagiotakis, Emmanouil Chrysoulakis, Nektarios Institute of Applied and Computational Mathematics Foundation for Research and Technology Hellas Remote Sensing Lab Crete Heraklion Greece

ISBN: (纸本)9781665493734

New spaceborne imaging spectrometers will provide great opportunities for mapping urban materials. We use the PRISMA Hyperspectral Imagery to estimate the fractional covers of key urban classes at two levels of details. Impervious, pervious and vegetation at level I where at level II we split the class Impervious to manmade surfaces (cement, asphalt, and metal roofs), the class pervious to soil and non-photosynthetic vegetation (NPV) and the class vegetation into and high and low canopy. The use of Random Forests Regression with synthetically mixed training data generated from the image-based spectral library was used for fraction mapping. Mean Absolute Error for all classes, at both levels, was lower than 18%. All classes at level I achieve error values close to 10% while at level II the majority achieves close to 11% with the lowest (5%) to be for the class "metals"and the highest (17%) to be at the class "soil"which has been overestimated across the urbanscape. We resume that the combination of RFR and synthetically mixed training data generated from the image-based library can allow a generalized urban fraction mapping across various cities of same typology and region when field-based data are absent. © 2023 IEEE.

关键词： Hyperspectral imaging

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Dynamic Speech Generation to Enhance Intelligibility in Noisy Environments

Dynamic Speech Generation to Enhance Intelligibility in Nois...

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International Conference on Acoustics, Speech, and Signal Processing (ICASSP)

作者： Olympia Simantiraki Maria Markaki Yannis Pantazis Institute of Applied and Computational Mathematics Foundation for Research and Technology Greece

ISBN: (数字)9798350368741

ISBN: (纸本)9798350368758

Synthetic speech is occasionally required to be enhanced by a fixed amount before being presented to the listener. However, this approach neglects the diverse types and levels of noise, potentially resulting in either unintelligible or unpleasant speech. This paper proposes a dynamic speech enhancement approach, which generates speech while accounting for the presence of noise. Our methodology extends the WaveRNN vocoder by conditioning not only the speech mel-spectrograms but also the spectrogram from the background noise. In training, the target speech is tilted according to the listeners’ preference and we further introduce an objective metric that aims at maximizing the spectro-temporal regions where target energy exceeds the masker energy. The generated speech was tested in speech-shaped noise at various noise levels. Our evaluation results showed that (a) in more adverse conditions, both a fixed-amount post-enhanced baseline system and the suggested dynamically-enhanced system performed equally well in terms of intelligibility and preference and (b) in the least noisy conditions, where the intelligibility scores of all models were nearly identical, listeners preferred the dynamically-enhanced speech. Our findings demonstrate and reinforce the benefits of using dynamic speech enhancement techniques in noisy environments.

关键词： Training Adaptation models Vocoders Virtual assistants Noise Speech enhancement Acoustics Noise measurement Speech synthesis Spectrogram

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Fragmentation dynamics of electron-impact double ionization of helium

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Chinese Physics B 2023年第6期32卷 9-15页

作者：刘士炜叶地发刘杰 Beijing Computational Science Research Center Beijing 100193China Laboratory of Computational Physics Institute of Applied Physics and Computational MathematicsBeijing 100088China Graduate School China Academy of Engineering PhysicsBeijing 100193China HEDPS Center for Applied Physics and Technologyand College of EngineeringPeking UniversityBeijing 100871China

We study the double ionization dynamics of a helium atom impacted by electrons with full-dimensional classical trajectory Monte Carlo simulation. The excess energy is chosen to cover a wide range of values from 5 e V to 1 ke V for comparative study. At the lowest excess energy, i.e., close to the double-ionization threshold, it is found that the projectile momentum is totally transferred to the recoil-ion while the residual energy is randomly partitioned among the three outgoing electrons, which are then most probably emitted with an equilateral triangle configuration. Our results agree well with experiments as compared with early quantum-mechanical calculation as well as classical simulation based on a two-dimensional Bohr's model. Furthermore, by mapping the final momentum vectors event by event into a Dalitz plot,we unambiguously demonstrate that the ergodicity has been reached and thus confirm a long-term scenario conceived by Wannier. The time scale for such few-body thermalization, from the initial nonequilibrium state to the final microcanonical distribution, is only about 100 attoseconds. Finally, we predict that, with the increase of the excess energy, the dominant emission configuration undergoes a transition from equilateral triangle to T-shape and finally to a co-linear mode. The associated signatures of such configuration transition in the electron–ion joint momentum spectrum and triple-electron angular distribution are also demonstrated.

关键词： double ionization classical trajectory Monte Carlo simulation Wannier threshold law ergodicity

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Improved error estimates for a modified exponential Euler method for the semilinear stochastic heat equation with rough initial data

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Science China mathematics 2024年第12期67卷 2873-2898页

作者： Xinping Gui Buyang Li Jilu Wang Beijing Computational Science Research Center Beijing 100193China Department of Applied Mathematics The Hong Kong Polytechnic UniversityHong KongChina School of Science Harbin Institute of TechnologyShenzhen 518055China

A class of stochastic Besov spaces BpL^(2)(Ω;˙H^(α)(O)),1≤p≤∞andα∈[−2,2],is introduced to characterize the regularity of the noise in the semilinear stochastic heat equation du−Δudt=f(u)dt+dW(t),under the following conditions for someα∈(0,1]:||∫_(0)^(t)e−(t−s)^(A)dW(s)||L^(2)(Ω;L^(2)(O))≤C^(t^(α/2))and||∫_(0)^(t)e−(t−s)^(A)dW(s)||_B^(∞)L^(2)(Ω:H^(α)(O))≤C..The conditions above are shown to be satisfied by both trace-class noises(withα=1)and one-dimensional space-time white noises(withα=1/2).The latter would fail to satisfy the conditions withα=1/2 if the stochastic Besov norm||·||B∞L^(2)(Ω;˙H^(α)(O))is replaced by the classical Sobolev norm||·||L^(2)(Ω;˙Hα(O)),and this often causes reduction of the convergence order in the numerical analysis of the semilinear stochastic heat *** this paper,the convergence of a modified exponential Euler method,with a spectral method for spatial discretization,is proved to have orderαin both the time and space for possibly nonsmooth initial data in L^(4)(Ω;˙H^(β)(O))withβ>−1,by utilizing the real interpolation properties of the stochastic Besov spaces and a class of locally refined stepsizes to resolve the singularity of the solution at t=0.

关键词： semilinear stochastic heat equation additive noise space-time white noise exponential Euler method spectral method strong convergence stochastic Besov space real interpolation

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Physics-Informed Deep Learning Approach for Reintroducing Atomic Detail in Coarse-Grained Configurations of Multiple Poly(lactic acid) Stereoisomers (vol 64, pg 1853, 2024)

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JOURNAL OF CHEMICAL INFORMATION AND MODELING 2024年第17期64卷 6926-6926页

作者： Christofi, Eleftherios Bacova, Petra Harmandaris, Vagelis A. Computation-based Science and Technology Research Center The Cyprus Institute Nicosia 2121 Cyprus Departamento de Ciencia de los Materiales e Ingeniería Metalúrgica y Química Inorgánica Facultad de Ciencias IMEYMAT Campus Universitario Río San Pedro s/n. Puerto Real Cádiz 11510 Spain Department of Mathematics and Applied Mathematics University of Crete Heraklion GR-71110 Greece Institute of Applied and Computational Mathematics Foundation for Research and Technology - Hellas Heraklion GR-71110 Crete Greece

Multiscale modeling of complex molecular systems, such as macromolecules, encompasses methods that combine information from fine and coarse representations of molecules to capture material properties over a wide range of spatiotemporal scales. Being able to exchange information between different levels of resolution is essential for the effective transfer of this information. The inverse problem of reintroducing atomistic degrees of freedom in coarse-grained (CG) molecular configurations is particularly challenging as, from a mathematical point of view, it is an ill-posed problem; the forward mapping from the atomistic to the CG description is typically defined via a deterministic operator (“one-to-one” problem), whereas the reversed mapping from the CG to the atomistic model refers to creating one representative configuration out of many possible ones (“one-to-many” problem). Most of the backmapping methods proposed so far balance accuracy, efficiency, and general applicability. This is particularly important for macromolecular systems with different types of isomers, i.e., molecules that have the same molecular formula and sequence of bonded atoms (constitution) but differ in the three-dimensional configurations of their atoms in space. Here, we introduce a versatile deep learning approach for backmapping multicomponent CG macromolecules with chiral centers, trained to learn structural correlations between polymer configurations at the atomistic level and their corresponding CG descriptions. This method is intended to be simple and flexible while presenting a generic solution for resolution transformation. In addition, the method is aimed to respect the structural features of the molecule, such as local packing, capturing therefore the physical properties of the material. As an illustrative example, we apply the model on linear poly(lactic acid) (PLA) in melt, which is one of the most popular biodegradable polymers. The framework is tested on a number of model sys

关键词： Biopolymers Copolymers Monomers Organic polymers Plastics

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Inferring the Parameters of Ultrafast Lasers from Images with Surface Patterns 13

Inferring the Parameters of Ultrafast Lasers from Images wit...

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13th International Symposium on Image and Signal Processing and Analysis, ISPA 2023

作者： Litsas, Anastasis Fraggelakis, Fotis Tsibidis, George D. Stratakis, Emmanuel Pantazis, Yannis University of Crete Computer Science Department Heraklion Crete Greece Institute of Electronic Structure and Laser Foundation for Research and Technology - Hellas Heraklion Crete Greece Institute of Applied and Computational Mathematics Foundation for Research and Technology - Hellas Heraklion Crete Greece

ISBN: (纸本)9798350315363

In this paper, we explore the potential of deep learning techniques in the field of ultra-fast laser processing. More specifically, we trained convolutional neural networks on an in-house dataset with the aim of predicting the laser parameters from images which capture the morphological characteristics of the material surface after being laser fabricated. There are several challenges related with the collected dataset stemming from stochastic variations of the material and the laser, the sampling scheme and the overall low sample size. Therefore, to further test our models we additionally construct a synthetic dataset. The results on the synthetic dataset are almost perfect showing that the proposed predictive models have the capacity to learn the assigned tasks. As expected, the predictive performance decreases when the real dataset is utilized. Nevertheless, we show that both the accuracy in the classification task and the mean square error in the majority of the regression tasks are satisfactory (e.g., classification accuracy drops from 99.9% to 94.8%). © 2023 IEEE.

关键词： Convolutional neural networks

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