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Phase-matching-free parametric oscillators based on two-dimensional semiconductors

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Light(Science & Applications) 2018年第1期7卷 992-1000页

作者： alessandro ciattoni Andrea Marini Carlo Rizza Claudio Conti Consiglio Nazionale Delle Ricerche(CNR-SPIN) Via Vetoio 1067100 L’AquilaItaly Department of Physical and Chemical Sciences University of L’AquilaVia Vetoio 1067100 L’AquilaItaly Institute for Complex Systems(ISC-CNR) Via dei Taurini 1900185 RomeItaly ICFO-Institut de Ciencies Fotoniques The Barcelona Institute of Science and Technology08860 CastelldefelsBarcelonaSpain Department of Industrial and Information Engineering and Economics University of L’AquilaVia G.Gronchi 18I-67100 L’AquilaItaly Department of Physics University SapienzaPiazzale Aldo Moro 500185 RomeItaly

Optical parametric oscillators are widely used as pulsed and continuous-wave tunable sources for innumerable applications,such as quantum technologies,imaging,and biophysics.A key drawback is material dispersion,which imposes a phase-matching condition that generally entails a complex design and setup,thus hindering tunability and *** we show that the burden of phase-matching is surprisingly absent in parametric microresonators utilizing mono-layer transition-metal dichalcogenides as quadratic nonlinear *** the exact solution of nonlinear Maxwell equations and first-principle calculations of the semiconductor nonlinear response,we devise a novel kind of phase-matching-free miniaturized parametric oscillator operating at conventional pump *** find that different two-dimensional semiconductors yield degenerate and non-degenerate emission at various spectral regions due to doubly resonant mode excitation,which can be tuned by varying the incidence angle of the external pump *** addition,we show that high-frequency electrical modulation can be achieved by doping via electrical gating,which can be used to efficiently shift the threshold for parametric *** results pave the way for the realization of novel ultra-fast tunable micron-sized sources of entangled photons—a key device underpinning any quantum *** miniaturized optical parametric oscillators may also be employed in lab-on-chip technologies for biophysics,detection of environmental pollution and security.

关键词： parametric matching degenerate

A novel solution treatment and aging for powder bed fusion–laser beam Ti–6Al–2Sn–4Zr–6Mo alloy: Microstructural and mechanical characterization

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International Journal of Minerals,Metallurgy and Materials 2025年第02期 414-424页

作者： Gianluca Pirro Alessandra Martucci alessandro Morri Mariangela Lombardi Lorella Ceschini Department of Industrial Engineering (DIN) Alma Mater Studiorum–University of Bologna Department of Applied Science and Technology (DISAT) Politecnico di Torino

Ti–6Al–4Zr–2Sn–6Mo alloy is one of the most recent titanium alloys processed using powder bed fusion–laser beam(PBF–LB) technology. This alloy has the potential to replace Ti–6Al–4V in automotive and aerospace applications, given its superior mechanical properties, which are approximately 10% higher in terms of ultimate tensile strength(UTS) and yield strength after appropriate heat treatment. In as-built conditions, the alloy is characterized by the presence of soft orthorhombic α″ martensite, necessitating a postprocessing heat treatment to decompose this phase and enhance the mechanical properties of the alloy. Usually, PBFed Ti6246 components undergo an annealing process that transforms the α″ martensite into an α–β lamellar microstructure. The primary objective of this research was to develop a solution treatment and aging(STA) heat treatment tailored to the unique microstructure produced by the additive manufacturing process to achieve an ultrafine bilamellar microstructure reinforced by precipitation hardening. This study investigated the effects of various solution temperatures in the α–β field(ranging from 800 to 875°C), cooling media(air and water), and aging time to determine the optimal heat treatment parameters for achieving the desired bilamellar microstructure. For each heat treatment condition,different α–β microstructures were found, varying in terms of the α/β ratio and the size of the primary α-phase lamellae. Particular attention was given to how these factors were influenced by increases in solution temperature and how microhardness correlated with the percentage of the metastable β phase present after quenching. Tensile tests were performed on samples subjected to the most promising heat treatment parameters. A comparison with literature data revealed that the optimized STA treatment enhanced hardness and UTS by13% and 23%, respectively, compared with those of the annealed alloy. Fracture surface analyses were conducted to investigate fracture

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Coulomb Friction Driving Brownian Motors

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Communications in Theoretical Physics 2014年第10期61卷 505-513页

作者： alessandro Manacorda Andrea Puglisi alessandro Sarracino Dipartimento di Fisica Università "Sapienza"p.le A.Moro 200185 RomeItaly Istituto dei Sistemi Complessi - CNR and Dipartimento di Fisica Università "Sapienza"p.le A.Moro 200185 RomeItaly Kavli Institute for Theoretical Physics China the Chinese Academy of Sciences Laboratoire de Physique Théorique de la Matière Condensée CNRS UMR 7600case courrier 121Université Paris 64Place Jussieu75255 Paris CedexFrance

We review a family of models recently introduced to describe Brownian motors under the influence of Coulomb friction, or more general non-linear friction laws. It is known that, if the heat bath is modeled as the usual Langevin equation(linear viscosity plus white noise), additional non-linear friction forces are not sufficient to break detailed balance, i.e. cannot produce a motor effect. We discuss two possibile mechanisms to elude this problem. A first possibility, exploited in several models inspired to recent experiments, is to replace the heat bath's white noise by a "collisional noise", that is the effect of random collisions with an external equilibrium gas of particles. A second possibility is enlarging the phase space, e.g. by adding an external potential which couples velocity to position, as in a Klein–Kramers equation. In both cases, non-linear friction becomes sufficient to achieve a non-equilibrium steady state and, in the presence of an even small spatial asymmetry, a motor effect is produced.

关键词： Brownian motors ratchet effect Coulomb friction

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A flexible multi-body model of a surface miner for analyzing the interaction between rock-cutting forces and chassis vibrations

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International Journal of Mining Science and Technology 2021年第3期31卷 365-375页

作者： alessandro Medolago Stefano Melzi Tesmec S.p.A. Grassobbio 24050Italy Department of Mechanics Politecnico di MilanoMilano 20156Italy

The discontinuous nature of rock cutting can easily cause unwanted vibrations in the structure of a surface *** these vibrations are not properly addressed,the related stress cycles can gradually damage the chassis resulting in fatigue *** events can seriously undermine the safety of operators and digging operations may be stopped for days,with an obvious economic *** work presents an analysis of the dynamics of a surface miner,focusing on the interaction between cutting machine dynamics and cutting forces,which is a new approach for this type of *** this purpose,the authors developed a numerical model of the cutting process made up of(1)a multi-body model of the cutting machine,which takes into account the chassis's flexibility;(2)a model of the rotating cutting head;and(3)a model of the interaction between the cutting head and rock,based on Shao's *** model was compared with experimental results and then used to investigate the effects of cutting speed and cutting depth on the machine dynamics.

关键词： Surface miner Flexible multi-body model Validation Cutting forces Chassis vibrations

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Spin-phonon decoherence in solid-state paramagnetic defects from first principles

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npj Computational Materials 2023年第1期9卷 1129-1136页

作者： Sourav Mondal alessandro Lunghi School of Physics AMBER and CRANN InstituteTrinity CollegeDublin 2Ireland

Paramagnetic defects in diamond and hexagonal boron nitride possess a combination of spin and optical properties that make them prototypical solid-state *** the coherence of these spin qubits being critically limited by spin-phonon relaxation,a full understanding of this process is not yet *** we apply ab initio spin dynamics simulations to this problem and quantitatively reproduce the experimental temperature dependence of spin relaxation time and spin coherence *** demonstrate that low-frequency two-phonon modulations of the zero-field splitting are responsible for spin relaxation and decoherence,and point to the nature of vibrations in 2-dimensional materials as the culprit for their shorter coherence *** results provide an interpretation to spin-phonon decoherence in solid-state paramagnetic defects,offer a strategy to correctly interpret experimental results,and pave the way for the accelerated design of spin qubits.

关键词： phonon relaxation state

Matrix Algebras in Non-Hermitian Quantum Mechanics

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Communications in Theoretical Physics 2011年第7期56卷 96-98页

作者： alessandro Sergi School of Physics University of KwaZulu-NatalPietermaritzburg CampusPrivate Bag X01 Scottsville

In principle, non-Hermitian quantum equations of motion can be formulated using as a starting point either the Heisenberg＇s or the Schroedinger＇s picture of quantum dynamics. Here it is shown in both cases how to map the algebra of commutators, defining the time evolution in terms of a non-Hermitian Hamiltonian, onto a non-Hamiltonian algebra with a Hermitian Hamiltonian. The logic behind such a derivation is reversible, so that any Hermitian Hamiltonian can be used in the formulation of non-Hermitian dynamics through a suitable algebra of generalized （non-Hamiltonian） commutators. These results provide a general structure （a template） for non-Hermitian equations of motion to be used in the computer simulation of open quantum systems dynamics.

关键词： non-hermitian quantum mechanics non-Hamiltonian dynamics open quantum systems

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Recent Advances in the Catalytic Functionalization of “Electrophilic” Indoles

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Chinese Journal of Chemistry 2020年第3期38卷 287-294页

作者： alessandro Cerveri Marco Bandini Dipartimento di Chimica"Giacomo Ciamician"-Alma Moter Studiorum Universita di Bologna Via Selmi 240126 BolognaItaly Consorzio C.I.N.M.P.I.S.Via Selmi 2 40126 BolognaItaly

When "dark"is bright:the scarcely explored electrophilic profile of the indolyl core(dark side)continues to inspire developments in organic synthesis by means of new catalytic *** advancements in the field enabled mol... 详细信息

关键词： chemistry. Catalytic heterocyclic

Cysteine carboxyethylation:a novel post-translational modification associated with autoimmune arthritis

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Signal Transduction and Targeted Therapy 2023年第8期8卷 3561-3562页

作者： alessandro Didonna Department of Anatomy and Cell Biology Brody School of MedicineEast Carolina UniversityGreenvilleNC 27834USA

In a study recently published in Science,Zhai et *** that protein carboxyethylation results in the formation of neoantigens with the ability to trigger autoimmune arthritis in the context of ankylosing spondylitis(AS)pathology.1 This work defines a novel molecular mechanism underlying immune tolerance breakdown,which could serve as a target for innovative therapeutic strategies against AS and other autoimmune disorders.

关键词： autoimmune pathology

Comparison Between Deep Learning Models and Traditional Machine Learning Approaches for Facial Expression Recognition in Ageing Adults

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Journal of Computer Science & Technology 2020年第5期35卷 1127-1146页

作者： Andrea Caroppo alessandro Leone Pietro Siciliano Institute for Microelectronics and Microsystems National Research Council of ItalyLecce 73100Italy

Facial expression recognition is one'of the most active areas of research in computer vision since one of the non-verbal communication methods by which one understands the lnood/mental state of a person is the expression of ***,it has been used in various fields such as human-robot interaction,security,computer graphics animation,and ambient ***,it remains a challenging task since existing approaches lack generalizability and almost all studies ignore the effects of facial attributes,such as *** expression recognition even though the research indicates that facial expression inanifestation varies with ***,a lot of progress has been made in this topic and great improvements in classification task were achieved with the emergence of deep learning *** approaches have sliown how hierarchies of features can be directly learned from original data,thus avoiding classical hand designed feature extraction methods that generally rely on manual operations witli labelled ***,research papers systematically exploring tlu4 performance of existing deep architectures for the task of classifying expression of ageing adults are absent in the *** the present work a tentative to try this gap is done considering the performance of three recent deep convolutiorial neural networks models(VGG-16,AlexNet and GoogLeNet/Inception V1)and evaluating it on four different benchmark datcisets(FACES,Lifespan,CIFE,and FER2013)which also contain facial expressions performed by elderly *** the baseline,and with the aim of making a comparison,two traditional inacliine learning approaches based on handcrafted features extraction process are evaluated on the same *** out an exhaustive and rigorous experimentation focused on the concept of "transfer learning",which consists of replacing the output level of the deep architectures considered with new output levels appropriate to the number of classes(facial expressions),

关键词： computer vision deep learning facial expression machine learning ageing adult