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Universal insertion of molecules in ionic compounds under pressure

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National Science Review 2024年第1期11卷 120-128页

作者： Feng Peng Yanming Ma Chris J.Pickard Hanyu Liu Maosheng Miao College of Physics and Electronic Information Luoyang Normal University Department of Chemistry and Biochemistry California State University Northridge State Key Laboratory of Superhard Materials & Key Laboratory of Material Simulation Methods and Software of Ministry of Education College of Physics Jilin University International Center of Future Science Jilin University Department of Materials Science & Metallurgy University of Cambridge Advanced Institute for Materials Research Tohoku University Department of Earth Science University of California Santa Barbara

Using first-principles calculations and crystal structure search methods, we found that many covalently bonded molecules such as H2, N2, CO2, NH3, H2O and CH4may react with NaC l, a prototype ionic solid,and form stable compounds under pressure while retaining their molecular structure. These molecules,despite whether they are homonuclear or heteronuclear, polar or non-polar, small or large, do not show strong chemical interactions with surrounding Na and Cl ions. In contrast, the most stable molecule among all examples, N2, is found to transform into cyclo-N5-anions while reacting with NaC l under high pressures. It provides a new route to synthesize pentazolates, which are promising green energy materials with high energy density. Our work demonstrates a unique and universal hybridization propensity of covalently bonded molecules and solid compounds under pressure. This surprising miscibility suggests possible mixing regions between the molecular and rock layers in the interiors of large planets.

关键词： molecule-solid hybrid materials high-pressure crystal structure prediction density functional theory planet interior

Optical cavity resonance with magnetized plasma

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Chinese Optics Letters 2018年第5期16卷 17-20页

作者： Dongyang Wang Jiaguang Han Shuang Zhang School of Physics ＆ Astronomy University of Birmingham Birmingham B15 2TT UK Center for Terahertz Waves and College of Precision Instrument and Optoeleetronics Engineering Tianjin University Tianjin 300072 China

Indefinite media with mixed signs of dielectric tensor elements possess unbounded equifrequency surfaces that have been utilized for diverse applications such as superimaging, enhanced spontaneous emission, and thermal radiation. One particularly interesting application of indefinite media is an optical cavity supporting anomalous scaling laws. In this Letter, we show that by replacing an indefinite medium with magnetized plasma one can construct a tunable indefinite cavity. The magnetized plasma model is based on realistic semiconductor material properties at terahertz frequencies that show hyperbolic dispersion in a certain frequency regime. The hyperbolic dispersion features are utilized for the design of optical cavities. Dramatically different sizes of cavities can support the same resonance mode at the same frequency. For a cavity of fixed size, the anomalous scaling law between the resonance frequency and mode number is confirmed. The resonance frequency can be strongly modulated by changing the strength of the applied magnetic field. The proposed model provides active controllability of terahertz resonances on the deep subwavelength scale with realistic semiconductor materials.

关键词： Optical cavity resonance with magnetized plasma

Highly efficient surface-emitting semiconductor lasers exploiting quasi-crystalline distributed feedback photonic patterns

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Light(Science & Applications) 2020年第1期9卷 1498-1508页

作者： Simone Biasco Andrea Ciavatti Lianhe Li AGiles Davies Edmund H.Linfield Harvey Beere David Ritchie Miriam S.Vitiello NEST CNR-Istituto Nanoscienze and Scuola Normale SuperiorePiazza San Silvestro 1256127 PisaItaly School of Electronic and Electrical Engineering University of LeedsLeeds LS29JTUK Cavendish Laboratory University of CambridgeCambridge CB30HEUK

Quasi-crystal distributed feedback lasers do not require any form of mirror cavity to amplify and extract *** implemented on the top surface of a semiconductor laser,a quasi-crystal pattern can be used to tune both the radiation feedback and the extraction of highly radiative and high-quality-factor optical modes that do not have a defined symmetric or anti-symmetric ***,this methodology offers the possibility to achieve efficient emission,combined with tailored spectra and controlled beam ***,we apply this concept to a onedimensional quantum cascade wire *** lithographically patterning a series of air slits with different widths,following the Octonacci sequence,on the top metal layer of a double-metal quantum cascade laser operating at THz frequencies,we can vary the emission from single-frequency-mode to multimode over a 530-GHz bandwidth,achieving a maximum peak optical power of 240mW(190 mW)in multimode(single-frequency-mode)lasers,with record slope efficiencies for multimode surface-emitting disordered THz lasers up to ≈570 mW/A at 78 K and ≈720 mW/A at 20 K and wall-plug efficiencies of η≈1%.

关键词： lasers surface quantum

Almost sure stabilization of hybrid systems by feedback control based on discrete-time observations of mode and state

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Science China(Information Sciences) 2018年第7期61卷 130-145页

作者： Gongfei SONG Zhenyu LU Bo-Chao ZHENG Xuerong MAO Jiangsu Collaborative Innovation Center on Atmospheric Environment and Equipment Technology School of Information and Control Nanjing University of Information Science and Technology School of Electronic and Information Engineering Nanjing University of Information Science and Technology Department of Mathematics and Statistics University of Strathclyde

Although the mean square stabilization of hybrid systems by feedback control based on discretetime observations of state and mode has been studied by several authors since 2013, the corresponding almost sure stabilization problem has received little attention. Recently, Mao was the first to study the almost sure stabilization of a given unstable system ˙x(t) = f(x(t)) by a linear discrete-time stochastic feedback control Ax([t/τ ]τ)d B(t)(namely the stochastically controlled system has the form dx(t) = f(x(t))dt +Ax([t/τ ]τ)d B(t)), where B(t) is a scalar Brownian, τ > 0, and [t/τ ] is the integer part of t/τ. In this paper, we consider a much more general problem. That is, we study the almost sure stabilization of a given unstable hybrid system ˙x(t) = f(x(t), r(t)) by nonlinear discrete-time stochastic feedback control u(x([t/τ ]τ), r([t/τ ]τ))d B(t)(so the stochastically controlled system is a hybrid stochastic system of the form dx(t) = f(x(t), r(t))dt + u(x([t/τ ]τ), r([t/τ ]τ))d B(t)), where B(t) is a multi-dimensional Brownian motion and r(t) is a Markov chain.

关键词： Brownian motion Markov chain generalized Itö formula almost sure exponential stability stochastic feedback control

Why does caloric restriction increase life and healthspan? The ‘clean cupboards’ hypothesis

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National Science Review 2020年第7期7卷 1153-1156页

作者： John R.Speakman State Key Laboratory of Molecular Developmental Biology Institute of Genetics and Developmental Biology Chinese Academy of Sciences Institute of Biological and EnvironmentalSciences University of Aberdeen CAS Center of Excellence in Animal Evolution and Genetics Kunming Institute of Zoology Chinese Academy of Sciences

The disposable soma hypothesis explanation of the effects of caloric restriction(CR) on lifespan fails to explain why CR generates negative impacts alongside the positive effects and does not work in all species. I pr... 详细信息

关键词： SHORT-TERM CALORIE DIETARY RESTRICTION PROTEIN RESTRICTION GRADED-LEVELS LONGEVITY SURVIVAL IMPACT RETARDATION EVOLUTION RODENTS

All-optical switching in silicon photonic waveguides with an epsilon-near-zero resonant cavity [Invited]

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Photonics Research 2018年第5期6卷 I0026-I0030页

作者： ANDRES D.NEIRA GREGORY A.WURTZ ANATOLY V.ZAYATS Department of Physics King's College London

Strong nonlinearity of plasmonic metamaterials can be designed near their effective plasma frequency in the epsilon-near-zero(ENZ) regime. We explore the realization of an all-optical modulator based on the Au nonlinearity using an ENZ cavity formed by a few Au nanorods inside a Si photonic waveguide. The resulting modulator has robust performance with a modulation depth of about 30 dB/μm and loss less than 0.8 dB for switching energies below 600 fJ. The modulator provides a double advantage of high mode transmission and strong nonlinearity enhancement in the few-nanorod-based design.

关键词： All-optical switching silicon photonic waveguides an epsilon-near-zero resonant cavity

Reinvigorating the Wiener-Hopf technique in the pursuit of understanding processes and materials

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National Science Review 2021年第2期8卷 11-13页

作者： David Abrahams Xun Huang Anastasia Kisil Gennady Mishuris Michael Nieves Sergei Rogosin Ilya Spitkovsky IsaacNewtonInstituteforMathematicalSciences CollegeofEngineering PekingUniversity DepartmentofMathematics UniversityofManchester DepartmentofMathematics AberystwythUniversity SchoolofComputingandMathematics KeeleUniversity FacultyofEconomics BelarusianStateUniversity ScienceandMathematics NewYorkUniversityAbuDhabi

The Wiener-Hopf(WH) method was created in 1931, by Norbert Wiener and Eberhard Hopf, to deliver exact solutions to integral equations with convolutiontype kernels on a half-line. It appears that this problem is closely related to that posed by Riemann in 1857 on the problem concerning the construction of a Fuchsian system of differential equations with given singular points and a prescribed monodromy group. This later became known as the 21 st Hilbert problem. The WH method is a powerful and long-standing tool that served as a catalyst in broadening the applicability of Fourier analysis, owing to the essential characteristics of analytic functions. Employing the Fourier transform(FT) to the integral equation leads to a RiemannHilbert(RH) problem on the real axis:

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A HYPERBOLIC SYSTEM OF CONSERVATION LAWS FOR FLUID FLOWS THROUGH COMPLIANT AXISYMMETRIC VESSELS

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Acta Mathematica Scientia 2010年第2期30卷 391-427页

作者： Gui-Qiang G.Chen School of Mathematical Sciences,Fudan University,Shanghai 200433,China Mathematical Institute,University of Oxford,24-29 St Giles,Oxford,OX1 3LB,UK Department of Mathematics,Northwestern University,Evanston,IL 60208-2730,USA Weihua Ruan Department of Mathematics,Computer Science and Statistics,Purdue University Calumet,Hammond,IN 46323-2094,USA School of Mathematical Sciences Fudan University Shanghai 200433 China Mathematical Institute University of Oxford 24-29 St Giles Oxford OX1 3LB UK Department of Mathematics Northwestern University Evanston IL 60208-2730 USA Department of Mathematics Computer Science and Statistics Purdue University Calumet Hammond IN 46323-2094 USA

We are concerned with the derivation and analysis of one-dimensional hyperbolic systems of conservation laws modelling fluid flows such as the blood flow through compliant axisyminetric vessels. Early models derived are nonconservative and/or nonho- mogeneous with measure source terms, which are endowed with infinitely many Riemann solutions for some Riemann data. In this paper, we derive a one-dimensional hyperbolic system that is conservative and homogeneous. Moreover, there exists a unique global Riemann solution for the Riemann problem for two vessels with arbitrarily large Riemann data, under a natural stability entropy criterion. The Riemann solutions may consist of four waves for some cases. The system can also be written as a 3 × 3 system for which strict hyperbolicity fails and the standing waves can be regarded as the contact discontinuities corresponding to the second family with zero eigenvalue.

关键词： conservation laws hyperbolic system fluid flow blood flow vessel hyper-bolicity Riemann problem Riemann solution wave curve shock wave rarefaction wave standing wave stability

Supersonic flow onto solid wedges, multidimensional shock waves and free boundary problems Dedicated to Professor LI Ta Tsien on the Occasion of His 80th Birthday

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Science China Mathematics 2017年第8期60卷 1353-1370页

作者： CHEN Gui-Qiang School of Mathematical Sciences Fudan University Academy of Mathematics and Systems Science Chinese Academy of Sciences School of Mathematical Sciences University of Chinese Academy of Sciences Mathematical Institute University of Oxford

When an upstream steady uniform supersonic flow impinges onto a symmetric straight-sided wedge,governed by the Euler equations,there are two possible steady oblique shock configurations if the wedge angle is less than the detachment angle—the steady weak shock with supersonic or subsonic downstream flow(determined by the wedge angle that is less than or greater than the sonic angle)and the steady strong shock with subsonic downstream flow,both of which satisfy the entropy *** fundamental issue—whether one or both of the steady weak and strong shocks are physically admissible solutions—has been vigorously debated over the past eight *** this paper,we survey some recent developments on the stability analysis of the steady shock solutions in both the steady and dynamic *** the static stability,we first show how the stability problem can be formulated as an initial-boundary value type problem and then reformulate it into a free boundary problem when the perturbation of both the upstream steady supersonic flow and the wedge boundary are suitably regular and small,and we finally present some recent results on the static stability of the steady supersonic and transonic *** the dynamic stability for potential flow,we first show how the stability problem can be formulated as an initial-boundary value problem and then use the self-similarity of the problem to reduce it into a boundary value problem and further reformulate it into a free boundary problem,and we finally survey some recent developments in solving this free boundary problem for the existence of the PrandtlMeyer configurations that tend to the steady weak supersonic or transonic oblique shock solutions as time goes to *** further developments and mathematical challenges in this direction are also discussed.

关键词： shock wave free boundary wedge problem transonic mixed type Euler equations static stability dynamic stability