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高阶材料常数：基于张量不变性的对称关系
No full textInternational audienceHöherordentliche Materialkonstanten bestimmen die nichtlineare Elastizität, feldvorgespannte Elektromechanik, Akustoelastizität sowie zahlreiche moderne Anwendungen in der nichtlinearen Akustik, piezoelektrischen Wandlung und in kristallinen Funktionsmaterialien. Dennoch ist selbst für gut untersuchte Kristalle die Symmetriereduktion höherer Tensoren in der Literatur fragmentiert, oft unvollständig hergeleitet oder in uneinheitlichen Konventionen dargestellt.Dieses Buch stellt einen einheitlichen, auf Invarianz beruhenden Ansatz zur systematischen Ableitung von Symmetrierelationen materialabhängiger Tensoren in kristallinen Medien vor. Ausgehend von exakten Tensortransformationsgesetzen und Punktgruppengeneratoren werden alle zulässigen Tensorkomponenten und ihre linearen Abhängigkeiten ohne heuristische Annahmen oder implizite Vereinfachungen bestimmt. Die Methode ist rangunabhängig und gilt einheitlich für verschiedene physikalische Kopplungen, wodurch kanonische reduzierte Formen entstehen, die transparent, reproduzierbar und konsistent sind.Ein vollständig ausgearbeitetes trigonal-symmetrisches Referenzbeispiel, basierend auf früheren Arbeiten des Autors in Annalen der Physik, validiert den Ansatz. Anschließend wird die Methode systematisch auf alle kristallographischen Punktgruppen erweitert und in übersichtlichen Zusammenfassungstabellen zusammengeführt.Higher-order material constants govern nonlinear elasticity, bias-field electromechanics, acoustoelasticity, and a wide range of modern applications in nonlinear acoustics, piezoelectric transduction, and engineered crystalline media. Yet even for well-studied crystals, the symmetry reduction of higher-rank tensors remains scattered across the literature, derived incompletely, or presented in incompatible conventions.This book provides a unified, invariance-based framework for deriving symmetry relations of material tensors in crystalline media. Starting from exact tensor transformation laws and point-group generators, all admissible tensor components and their linear relations are obtained systematically—without heuristic assumptions or undocumented shortcuts. The method applies uniformly across tensor ranks and physical couplings, yielding canonical reduced forms that are transparent, reproducible, and internally consistent.A fully worked trigonal benchmark, grounded in the author’s earlier Annalen der Physik study of biased piezoelectric crystals, validates the approach. The treatment then extends exhaustively across all crystallographic point groups and culminates in consolidated summary tables for rapid reference.This volume provides a rigorous generator-based invariance procedure applicable at arbitrary tensor rank, explicit symmetry reductions for elastic, piezoelectric, dielectric, electrostrictive, and higher-order coupled tensors, complete coverage of all crystallographic point groups and the isotropic limit, and a consistent Voigt and generalized-Voigt convention designed to eliminate sign and indexing ambiguities.Intended as both a reference and a methodological guide, this book offers a dependable foundation for researchers and engineers working with higher-order constitutive models in crystalline and multiphysics media.Las constantes materiales de orden superior gobiernan la elasticidad no lineal, la electromecánica bajo campos de polarización, la acustoelasticidad y numerosas aplicaciones modernas en acústica no lineal, transducción piezoeléctrica y medios cristalinos diseñados. Sin embargo, incluso para cristales bien estudiados, la reducción por simetría de tensores de alto orden sigue estando dispersa en la literatura, a menudo incompleta o presentada bajo convenciones incompatibles.Este libro introduce un marco unificado basado en la invariancia tensorial para derivar sistemáticamente las relaciones de simetría de los tensores de propiedades materiales en medios cristalinos. A partir de leyes exactas de transformación tensorial y generadores de grupos puntuales, se obtienen rigurosamente todas las componentes admisibles y sus relaciones lineales, sin recurrir a suposiciones heurísticas ni atajos no documentados. El método se aplica de forma uniforme a cualquier rango tensorial y a diversos acoplamientos físicos, produciendo formas reducidas canónicas, transparentes y reproducibles.Un ejemplo completamente desarrollado para la simetría trigonal, basado en el trabajo previo del autor publicado en Annalen der Physik, valida el enfoque. El tratamiento se extiende posteriormente a todos los grupos puntuales cristalográficos y culmina en tablas resumen para consulta rápida.Les constantes matérielles d’ordre supérieur gouvernent l’élasticité non linéaire, l’électromécanique sous champ biaisé, l’acoustoélasticité et de nombreuses applications modernes en acoustique non linéaire, transduction piézoélectrique et milieux cristallins ingénierés. Pourtant, même pour des cristaux bien étudiés, la réduction par symétrie des tenseurs de rang élevé demeure dispersée dans la littérature, souvent incomplète ou formulée selon des conventions incompatibles.Cet ouvrage propose un cadre unifié fondé sur l’invariance tensorielle pour dériver systématiquement les relations de symétrie des tenseurs de constantes matérielles dans les milieux cristallins. À partir des lois exactes de transformation tensorielle et des générateurs des groupes ponctuels, l’ensemble des composantes admissibles et de leurs relations linéaires est obtenu sans hypothèses heuristiques ni raccourcis non documentés. La méthode s’applique uniformément à tous les rangs tensoriels et aux différents couplages physiques, conduisant à des formes réduites canoniques transparentes, reproductibles et cohérentes.Une étude de référence entièrement développée pour la symétrie trigonale, fondée sur les travaux antérieurs de l’auteur publiés dans Annalen der Physik sur les cristaux piézoélectriques sous champ biaisé, valide la démarche. Le traitement est ensuite étendu de manière exhaustive à l’ensemble des groupes ponctuels cristallographiques et aboutit à des tableaux de synthèse facilitant l’utilisation pratique des résultats.Cet ouvrage fournit ainsi une procédure d’invariance rigoureuse applicable à tout rang tensoriel, des réductions explicites pour les constantes élastiques, piézoélectriques, diélectriques, électrostrictives et autres couplages d’ordre supérieur, une couverture complète des symétries cristallographiques jusqu’à la limite isotrope, ainsi qu’une convention Voigt et Voigt généralisée cohérente visant à éliminer toute ambiguïté de signe ou d’indexation.Conçu à la fois comme ouvrage de référence et comme guide méthodologique, ce livre constitue une base fiable pour les chercheurs et ingénieurs travaillant sur des modèles constitutifs d’ordre supérieur dans les milieux cristallins et multiphysiques.उच्च-क्रम भौतिक स्थिरांक गैर-रेखीय प्रत्यास्थता, पक्षपाती क्षेत्र विद्युत-यांत्रिकी, ध्वनि-प्रत्यास्थता तथा गैर-रेखीय ध्वनिकी, पाईजोइलेक्ट्रिक ट्रांसडक्शन और अभियांत्रिक क्रिस्टलीय माध्यमों में अनेक आधुनिक अनुप्रयोगों को नियंत्रित करते हैं। इसके बावजूद, सुविख्यात क्रिस्टलों के लिए भी उच्च-क्रम टेन्सरों का सममिति-आधारित अपसारण साहित्य में बिखरा हुआ, अपूर्ण अथवा असंगत परंपराओं में प्रस्तुत पाया जाता है।यह पुस्तक क्रिस्टलीय माध्यमों में भौतिक टेन्सरों के सममिति संबंधों को व्यवस्थित रूप से प्राप्त करने हेतु टेन्सर अपरिवर्तनीयता पर आधारित एकीकृत ढांचा प्रस्तुत करती है। सटीक टेन्सर रूपांतरण नियमों और बिंदु-समूह जनकों से प्रारंभ करते हुए, सभी अनुमत टेन्सर घटक और उनके रैखिक संबंध कठोरता से प्राप्त किए जाते हैं, बिना किसी हीयुरिस्टिक अनुमान या अव्यक्त सरलीकरण के।高次材料定数は、非線形弾性、バイアス場下の電気機械結合、音弾性効果、ならびに非線形音響、圧電変換、設計結晶材料における多くの現代的応用を支配している。しかし、十分に研究された結晶であっても、高次テンソルの対称性縮約は文献中に散在しており、不完全または互換性のない規約で示されることが多い。本書は、テンソル不変性に基づく統一的枠組みを提示し、結晶媒体における材料テンソルの対称関係を体系的に導出する。正確なテンソル変換則と点群生成元から出発し、すべての許容テンソル成分およびそれらの線形関係を、ヒューリスティックな仮定や暗黙的近似なしに厳密に求める。Hogere-orde materiaalconstanten bepalen niet-lineaire elasticiteit, elektromecanica onder biasvelden, acousto-elasticiteit en talrijke moderne toepassingen in niet-lineaire akoestiek, piëzo-elektrische transductie en ontworpen kristallijne media. Desondanks blijft de symmetriereductie van hogere-rang tensoren, zelfs voor goed bestudeerde kristallen, versnipperd in de literatuur, vaak onvolledig afgeleid of gepresenteerd in onderling incompatibele conventies.Dit boek introduceert een uniform, op tensorinvariantie gebaseerd raamwerk voor de systematische afleiding van symmetrierelaties van materiaaltensoren in kristallijne media. Vertrekkend van exacte tensortransformatiewetten en puntgroepgeneratoren worden alle toegestane tensorcomponenten en hun lineaire relaties strikt afgeleid, zonder heuristische aannames of ongedocumenteerde vereenvoudigingen.As constantes de materiais de ordem superior governam a elasticidade não linear, a eletromecânica sob campos de polarização, a acustoelasticidade e diversas aplicações modernas em acústica não linear, transdução piezoelétrica e meios cristalinos engenheirados. No entanto, mesmo para cristais amplamente estudados, a redução por simetria de tensores de alta ordem permanece dispersa na literatura, frequentemente incompleta ou apresentada em convenções incompatíveis.Este livro apresenta um arcabouço unificado baseado na invariância tensorial para a derivação sistemática das relações de simetria de tensores de propriedades materiais em meios cristalinos. A partir de leis exatas de transformação tensorial e geradores de grupos pontuais, todas as componentes admissíveis e suas relações lineares são obtidas de forma rigorosa, sem pressupostos heurísticos ou simplificações implícitas. O método aplica-se uniformemente a qualquer ordem tensorial e a diferentes acoplamentos físicos, resultando em formas reduzidas canônicas, transparentes e reproduzíveis.Высшие материальные константы определяют нелинейную упругость, электромеханику при наличии смещающих полей, акустоэластичность и широкий спектр современных приложений в нелинейной акустике, пьезоэлектрической трансдукции и инженерных кристаллических средах. Тем не менее даже для хорошо изученных кристаллов редукция тензоров высокого ранга по симметрии остаётся фрагментированной в литературе, часто выводится неполно или представляется в несовместимых конвенциях.В данной книге предлагается единый подход, основанный на тензорной инвариантности, для систематического вывода симметрийных соотношений материальных тензоров в кристаллических средах. Исходя из точных законов тензорного преобразования и генераторов точечных групп, все допустимые компоненты тензоров и их линейные соотношения выводятся строго и прозрачно — без эвристических предположений и недокументированных упрощений. Метод применяется одинаково для любых тензорных рангов и физических связей, приводя к каноническим редуцированным формам, которые являются воспроизводимыми и внутренне согласованными.Полностью разработанный эталонный пример для тригональной симметрии, основанный на предыдущей работе автора в Annalen der Physik по пьезоэлектрическим кристаллам под действием смещающих полей, подтверждает корректность метода. Далее изложение охватывает все кристаллографические точечные группы и завершается сводными таблицами для быстрого практического использования.高阶材料常数控制着非线性弹性、偏置场电机耦合、声弹性以及非线性声学、压电换能和工程化晶体介质中的诸多现代应用。然而，即便对于研究充分的晶体，高阶张量的对称约化仍然零散地分布于文献中，往往推导不完整，或采用彼此不兼容的约定。本书提出了一种基于张量不变性的统一框架，用于系统地推导晶体介质中材料张量的对称关系。从精确的张量变换定律和点群生成元出发，严格地获得所有允许的张量分量及其线性关系，避免了启发式假设和未说明的简化。该方法对不同张量阶数和物理耦合形式具有统一适用性，得到的约化形式清晰、可重复且内部一致。书中通过一个完整的三方晶系实例验证了该方法，该实例基于作者先前发表于 Annalen der Physik 的偏置压电晶体研究。随后，方法被系统地推广至所有晶体学点群，并最终汇总为便于快速查阅的对称约化表格
De nouveaux alliés du bien-être des animaux confrontés aux défis des transitions agroécologiques et climatiques
No full textNational audienc
Accuracy of Complex Mathematical Operations and Functions in Single and Double Precision
No full textVertical Space Charge Limited Device (VSCLD) driving an integrated Quantum-Dots Light-Emitting Diode
No full textInternational audienceVertical light-emitting space charge limited device (V-LESCLD) is fabricated at low temperature using the cheapest solution process (spin-coating) and inorganic materials for the bottom driving device and for the light emitting layer. The device integrates a bottom space charge limited device (SCLD) and a top quantum dots light emitting diode (QLED). The new SCLD device is a three terminals device. Its structure is a stack of a bottom contact, a resistive low mobility layer, an ITO nanoparticles layer, a ZnO semiconducting layer and a top contact. The bottom contact acts as a gate. The intermediate ITO nanoparticles layer as a source and the top contact as a drain. The device has the same structure as Vertical Field Effect transistor (VFET).The main purpose to use this cheap spin-coated SCLD is that it can deliver more than 1 A cm-2 at low voltage, much more than any usual VFET, allowing the driving of the top QLED. Moreover, the very low subthreshold swing of 40 mV/dec over 5 drain current decades, probably due to a tunnel effect from ITO NPs to ZnO, allows fast driving of the QLED. Finally, and for the first time when using vertical electronic device, spin-coated ITO nanoparticles layer with some space between the nanoparticles is used as source. This layer covers much more the source area than any other nanowire-based layer.The V-LESCLD device achieves a low driving voltage of 1.9V in both gate and drain voltage driving modes, with a brightness of 11,300 cd m-2 and an on/off ratio of 106 at VGS = –6.5V and VDS = 9V
Analytical reliability performance maps for bond wire interfaces in power modules under cyclic thermomechanical loads
No full textInternational audienceReliability of power modules based on Insulated Gate Bipolar Transistors (IGBTs) is majorly challenged by thermomechanical fatigue, especially at the wirebond-chip interface where lift-off failure mechanisms commonly occur. This paper introduces a novel analytical model tailored to the geometry and material properties of the wirebond-chip interface to rapidly predict reliability performance maps highlighting different zones of expected elastoplastic behaviors under thermomechanical cycling. The model integrates a thermomechanical stress formulation with a Dugdale Cohesive Zone Model to capture plastic zone development at the interface and applies the Lower Bound Shakedown Theorem to identify elastoplastic behaviors without having to perform full cyclic incremental finite element simulations. The proposed analysis enables classification of cyclic behaviors into elastic, shakedown, and alternating plasticity regimes, providing a deeper understanding of the transition to low cycle fatigue at the shakedown/alternating plasticity boundary. Analytical predictions are compared to 2D finite element analyses, which confirm the ability of the model to capture key features like plastic strain evolution and its stabilization. The proposed modular model serves as a rapid and adaptable tool for early-stage reliability assessment as a function of geometric, material, and loading parameters
Three-dimensional effects on carbon capture in wavy falling films
No full textInternational audienceWave evolution in thin-film flows is highly relevant for heat and mass transfer applications, such CO2 capture in falling film absorbers. To develop a detailed understanding of potential enhancement mechanisms associated with the evolution of three-dimensional (3D) waveforms, we perform 3D direct numerical simulations of passive scalar transport in laminar-wavy film flows, using a hybrid front-tracking/level-set method to accurately resolve interfacial features. CO2 absorption is greatly enhanced in the presence of interfacial waves with the liquid-side mass transfer coefficient increasing tenfold relative to that of a flat film for the highest film Reynolds numbers (Re) studied. This is primarily due to changes in interfacial and internal flow dynamics rather than an increase in the gas-liquid interfacial area. The recirculation region present in the leading and trailing fronts of the 3D waves intensifies mass transfer, and their effectiveness increases with Re. At low Re, there is a film region beneath the wavy interface, which remains relatively undisturbed where mass transfer is dominated by diffusion. The introduction of structured substrates to promote mass transfer under these conditions is recommended. The visco-capillary ripple region, which precedes the leading and trailing fronts for sufficiently high Re, provides a relatively high degree of spanwise advection, with the mean spanwise velocity magnitude reaching around one-quarter that in the streamwise direction. This underscores the importance of solving the fully-3D problem as these effects do not have a two-dimensional analogue
Routing India towards Net Zero: Optimal Planning of the CCS Infrastructure
No full textGiven its size, growing population, and emerging economy, India's energy choices are critically important for mitigating global climate change. The country's increasing energy consumption, heavily reliant on coal, raises concerns about its ability to achieve its net-zero target by 2070. Carbon Capture and Storage (CCS) technologies offer a potential solution to reduce emissions from coal-fired power plants. However, the size, cost, and feasibility of CCS deployment in India remain largely unexplored.This paper addresses this gap by introducing a cost-minimizing Mixed Integer Linear Program (MILP) model for CCS deployment in India. The model incorporates detailed carbon capture investment, pipeline routing, and onshore and offshore storage investments. To examine the implications of CCS adoption, we analyze four scenarios that reflect alternative policy mandates, storage restrictions, and capture targets.Our results reveal several important findings. First, India's optimal CO2 pipeline network is characterized by local infrastructures concentrated around storage basins rather than forming a nationally integrated network. Second, a significant portion of emissions is transported along an eastern transportation 'backbone' in all modeled scenarios
Divergence-Free Diffusion Models for Incompressible Fluid Flows
No full textGenerative diffusion models are extensively used in unsupervised and self-supervised machine learning with the aim to generate new samples from a probability distribution estimated with a set of known samples. They have demonstrated impressive results in replicating dense, real-world contents such as images, musical pieces, or human languages. This work investigates their application to the numerical simulation of incompressible fluid flows, with a view toward incorporating physical constraints such as incompressibility in the probabilistic forecasting framework enabled by generative networks. For that purpose, we explore different conditional, score-based diffusion models where the divergence-free constraint is imposed by the Leray spectral projector, and autoregressive conditioning is aimed at stabilizing the forecasted flow snapshots at distant time horizons. The proposed models are run on a benchmark turbulence problem, namely a Kolmogorov flow, which allows for a fairly detailed analytical and numerical treatment and thus simplifies the evaluation of the numerical methods used to simulate it. Numerical experiments of increasing complexity are performed in order to compare the advantages and limitations of the diffusion models we have implemented and appraise their performances, including: (i) in-distribution assessment over the same time horizons and for similar physical conditions as the ones seen during training; (ii) rollout predictions over time horizons unseen during training; and (iii) out-of-distribution tests for forecasting flows markedly different from those seen during training. In particular, these results illustrate the ability of diffusion models to reproduce the main statistical characteristics of Kolmogorov turbulence in scenarios departing from the ones they were trained on
