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Dynamics of thinning and destruction of the continental cratonic lithosphere: Numerical modeling

Science China Earth Sciences 2018年第7期61卷 823-852页

作者： Mingqi LIU Zhonghai LI Key laboratory of {1. geodynamics College of Earth and Planetary Sciences University of Chinese Academy of Sciences Institute of Geology Chinese Academy of Geological Sciences

Thinning of the cratonic lithosphere is common in nature, but its destruction is not. In either case, the mechanisms for both thinning and destruction are still widely under debate. In this study, we have made a review on the processes and mechanisms of thinning and destruction of cratonic lithosphere according to previous studies of geological/geophysical observations and numerical simulations, with specific application to the North China Craton(NCC). Two main models are suggested for the thinning and destruction of the NCC, both of which are related to subduction of the oceanic lithosphere. One is the "bottom-up" model, in which the deeply subducting slab perturbs and induces upwelling from the hydrous mantle transition zone(MTZ). The upwelling produces mantle convection and erodes the bottom of the overriding lithosphere by the fluid-meltperidotite reaction. Mineral compositions and rheological properties of the overriding lithospheric mantle are changed, allowing downward dripping of lithospheric components into the asthenosphere. Consequently, lithospheric thinning or even destruction occurs. The other is the "top-down" model, characterized by the flat subduction of oceanic slab beneath the overriding cratonic lithosphere. Dehydration reactions from the subducting slab would significantly hydrate the lithospheric mantle and decrease its rheological strength. Then the subduction angle may be changed from shallow to steep, inducing lateral upwelling of the asthenosphere. This upwelling would heat and weaken the overriding lithospheric mantle, which led to the weakened lithospheric mantle dripping into the asthenosphere. These two models have some similarities, in that both take the subducting oceanic slab and relevant fluid migration as the major driving mechanism for thinning or destruction of the overriding cratonic lithosphere. The key difference between the two models is the effective depth of the subducting oceanic slab. One is stagnation and flattening in t

关键词： Lithospheric thinning Cratonic destruction Big mantle wedge Plate subduction Fluid migration Numericalmodeling

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3D MHD simulation of the double-gradient instability of the magnetotail current sheet

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Science China(Technological Sciences) 2018年第9期61卷 1364-1371页

作者： DUAN AiYing ZHANG Huai LU Hao Yu Key laboratory of {1. geodynamics University of Chinese Academy of Sciences State Key laboratory of Space Weather Chinese Academy of Sciences School of Space and Environment Beihang University

Flapping motion of the current sheet(CS) is an important physical process in the Earth's magnetotail. The magnetic doublegradient model, which includes both the instability and wave modes, offers a reasonable explanation for the exciting and propagation of the flapping wave. In this paper, we apply an advanced numerical magnetohydrodynamic(MHD) scheme(conservation element and solution element(CESE)-MHD) to simulate the magnetic double-gradient instability in an idealized current sheet that mimics the magnetotail configuration. We initialize the simulations with a numerically relaxed magnetotail equilibrium, in which the normal component of the magnetic field has a tailward gradient. It is confirmed in our simulation that the instability develops in the current layer. The growth rate of the instability yielded from the simulation is very close to the prediction of theory, with a relative deviation of only ten percent. The results demonstrate that the CESE-MHD scheme is very powerful in numerical study of the double-gradient mechanism of the CS flapping mode, and can be used for further investigations of the flapping motion in more realistic CS configurations.

关键词： Earth's magnetotail current sheet flapping magnetohydrodynamic numerical simulation

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Pure quantum gradient descent algorithm and full quantum variational eigensolver

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Frontiers of physics 2024年第2期19卷 221-234页

作者： Ronghang Chen Zhou Guang Cong Guo Guanru Feng Shi-Yao Hou College of Physics and Electronic Engineering Center for Computational SciencesSichuan Normal UniversityChengdu 610068China Shenzhen SpinQ Technology Co. Ltd.Shenzhen 518045China DEEPROUTE.AI

Optimization problems are prevalent in various fields,and the gradient-based gradient descent algorithm is a widely adopted optimization ***,in classical computing,computing the numerical gradient for a function with variables necessitates at least d+1.function evaluations,resulting in a computational complexity of O(d).As the number of variables increases,the classical gradient estimation methods require substantial resources,ultimately surpassing the capabilities of classical ***,leveraging the principles of superposition and entanglement in quantum mechanics,quantum computers can achieve genuine parallel computing,leading to exponential acceleration over classical algorithms in some *** this paper,we propose a novel quantum-based gradient calculation method that requires only a single oracle calculation to obtain the numerical gradient result for a multivariate *** complexity of this algorithm is just O(1..Building upon this approach,we successfully implemented the quantum gradient descent algorithm and applied it to the variational quantum eigensolver(VQE),creating a pure quantum variational optimization *** with classical gradient-based optimization algorithm,this quantum optimization algorithm has remarkable complexity advantages,providing an efficient solution to optimization *** proposed quantum-based method shows promise in enhancing the performance of optimization algorithms,highlighting the potential of quantum computing in this field.

关键词： quantum algorithm gradient descent variational quantum algorithm

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Ultra-simplified diffraction-based computational spectrometer

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Light(Science & Applications) 2024年第6期13卷 1022-1031页

作者： Chuangchuang Chen Honggang Gu Shiyuan Liu State Key laboratory of Intelligent Manufacturing Equipment and Technology Huazhong University of Science and TechnologyWuhanHubei430074China Optics Valley laboratory WuhanHubei430074China

Miniaturizing spectrometers for compact and cost-effective mobile platforms is a major challenge in current spectroscopy research,where conventional spectrometers are impractical due to their bulky *** miniaturized designs primarily rely on precalibrated response functions of nanophotonic structures to encode spectral information captured in a snapshot by detector *** spectrum reconstruction is achieved through computational techniques,but this requires precise component design,high-precision fabrication,and *** propose an ultra-simplified computational spectrometer that employs a one-to-broadband diffraction decomposition strategy facilitated by a numerical regularized transform that depends only on the spectrum of the diffracted *** key feature of our design is the use of a simple,arbitrarily shaped pinhole as the partial disperser,eliminating the need for complex encoding designs and full spectrum *** spectrometer achieves a reconstructed spectral peak location accuracy of better than 1.nm over a 200 nm bandwidth and excellent resolution for peaks separated by 3 nm in a bimodal spectrum,all within a compact footprint of under half an ***,our approach also reveals a breakthrough in broadband coherent diffractive imaging without requiring any prior knowledge of the broadband illumination spectrum,assumptions of non-dispersive specimens,or correction for detector quantum efficiency.

关键词： simplified spectrum illumination

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Controlled analogue experiments on propagation of seismic electromagnetic signals

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Chinese Science Bulletin 2005年第17期50卷 1956-1961页

作者： HUANG Qinghua computational {1. laboratory Department of GeophysicsSchool of Earth and Space Sciences Peking University Beijing 100871China

This study presented a method of laboratory analogue experiments based on a geographical scaling model and a waveguide model to investigate the characteristics of the propagation of seismic electromagnetic signals in the crust and the atmosphere. Some controlled experiments were done to evaluate the possible influence on the experimental results from the background electromagnetic field, geo-graphical conditions, boundary effects, the source of elec-tromagnetic signals (position, magnitude, and frequency), and media conductivity. The reliability and the extensibility of the above analogue experimental method were also inves-tigated. This study indicated that such kind of analogue ex-perimental method provided an intuitionistic way of studying the propagation of seismic electromagnetic signals, which is one of the most difficult research topics in seismo-electro- magnetism.

关键词：地震电磁信号传播方式波导模式震源

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Numerical analysis on thermal conductivity of poly-mineral rock

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Earthquake Science 2010年第3期23卷 223-232页

作者： Huimin Jing Xiangwei Yu Huai Zhang Yaolin Shi laboratory of {1. geodynamics Graduate University of Chinese Academy of Sciences Beijing 100049 China

In order to explore the thermal conductivity of the natural poly-mineral rock,numerical tests of rock models with randomly-distributed components were conducted and compared with each *** designed Monte Carlo method was adopted to ingratiate the requirement of the random characteristics of grain size and the grains＇spatial *** requirement was fulfilled by clustering the randomly generated unstructured tetrahedral elements in full three *** rocks are consisted of randomly distributed crystal particles or intergranular *** primary results verify that the thermal conductivity of the rock is strongly sensitive to the ingredients＇ volume fraction and their spatial ***,we proved that,in order to reduce the measurement error to a reasonable range,the numerical specimen must be large enough or include sufficient number of mineral *** numerical test results are in accordance with a variety of empirical formulas which are currently employed in petrology.

关键词： thermal conductivity poly-mineral numerical test finite element method

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Modeling seismic wave propagation in heterogeneous medium using overlap domain pseudospectral method

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Earthquake Science 2008年第1期21卷 46-57+108页

作者：严九鹏王彦宾 Beijing 1.0871.China laboratory of {1. geodynamics Department of Geophysics School of Earth and Space Sciences Pe-king University laboratory of {1. geodynamics Department of Geophysics School of Earth and Space Sciences Pe-king University

Pseudospectral method is an efficient and high accuracy numerical method for simulating seismic wave propaga- tion in heterogeneous earth medium. Since its derivative operator is global, this method is commonly considered not suitable for parallel computation. In this paper, we introduce the parallel overlap domain decomposition scheme and give a parallel pseudospectral method implemented on distributed memory PC cluster system for modeling seismic wave propagation in heterogeneous medium. In this parallel method, the medium is decomposed into several subdomains and the wave equations are solved in each subdomain simultaneously. The solutions in each subdomain are connected through the transferring at the overlapped region. Using 2D models, we compared the parallel and traditional pseudospectral method, analyzed the accuracy of the parallel method. The results show that the parallel method can efficiently reduce computation time for the same accuracy as the traditional method. This method could be applied to large scale modeling of seismic wave propagation in 3D heterogeneous medium.

关键词： overlap domain decomposition scheme Fourier pseudospectral method parallel computation seismic wavefield

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Regional 3D geological modeling along metro lines based on stacking ensemble model

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Underground Space 2024年第5期18卷 65-82页

作者： Xia Bian Zhuyi Fan Jiaxing Liu Xiaozhao Li Peng Zhao Key laboratory of Ministry of Education for Geomechanics and Embankment Engineering Hohai UniversityNanjing 210098China Yunlong Lake laboratory of Deep Underground Science and Engineering Xuzhou 221000China State Key laboratory for Geomechanics and Deep Underground Engineering China University of Mining and TechnologyXuzhou 221000China

This paper presents a regional 3D geological modeling method based on the stacking ensemble technique to overcome the challenges of sparse borehole data in large-scale linear underground *** proposed method transforms the 3D geological modeling problem into a stratigraphic property classification problem within a subsurface space grid cell *** data is pre-processed and trained using stacking method with five different machine learning *** resulting modelled regional cells are then classified,forming a regional 3D grid geological model.A case study for an area of 324 km2 along Xuzhou metro lines is presented to demonstrate the effectiveness of the proposed *** study shows an overall prediction accuracy of 85.4%.However,the accuracy for key stratigraphy layers influencing the construction risk,such as karst carve strata,is only 4.3%due to the limited borehole *** address this issue,an oversampling technique based on the synthetic minority oversampling technique(SMOTE)algorithm is *** technique effectively increases the number of sparse stratigraphic samples and significantly improves the prediction accuracy for karst caves to 65.4%.Additionally,this study analyzes the impact of sampling distance on model *** is found that a lower sampling interval results in higher prediction accuracy,but also increases computational resources and time ***,in this study,an optimal sampling distance of 1.m is chosen to balance prediction accuracy and computation ***,the number of geological strata is found to have a negative effect on prediction *** mitigate this,it is recommended to merge less significant stratigraphy layers,reducing computation *** key strata layers,such as karst caves,which have a significant impact on construction risk,further onsite sampling or oversampling using the SMOTE technique is recommended.

关键词： 3D geological modeling Borehole data Stacking Machine learning

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Thermal structure about southwest sub-basin of South China Sea

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Earthquake Science 2011年第5期24卷 427-436页

作者： Lin Meng Jian Zhang laboratory of {1. geodynamics The Graduate University of the Chinese Academy of Sciences Beijing 100049 China

There are some factors, such as the topographic relief, sedimentary thickness and thermal conductivity, magmatic activity and thermal cooling, influencing the seafloor heat flow and the evolution of lithosphere structure in southwest sub-basin （SWSB）, South China Sea. On the base of the geological structure characteristic of SWSB this paper will discuss some other factors including thermal anomaly area, dike produced by magma intrusion and lithosphere relief, by modeling and calculating. Calculating results indicate partial areas where temperature is higher than vicinity in the lithosphere, which we call thermal anomaly here containing thermal anomaly area and dike in this paper, could decrease heat flow below, increase above, and gradually increase to two sides; heat flow in upwelling parts of lithosphere is usually higher than sinking parts, and in the middle is of a gradual transition.

关键词： southwest sub-basin (SWSB) thermal anomaly field heat flow dike lithosphere relief

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Origin of the Disparity between the Stability of Transmutated Mix-Cation and Mix-Anion Compounds

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Chinese Physics Letters 2024年第5期41卷 53-60页

作者：野仕伟耿松源梁汉普张燮魏苏淮 Beijing computational Science Research Center Beijing 100193China Advanced Materials Thrust Function HubHong Kong University of Science and TechnologyGuangzhou 511458China School of Materials Science and Engineering Northwestern Polytechnical UniversityXi’an 710072China

Transmutation is an efficient approach for material design. For example, ternary compound CuGaSe_(2) in chalcopyrite structure is a promising material for novel optoelectronic and thermoelectric device applications. It can be considered as formed from the binary host compound ZnSe in zinc-blende structure by cation transmutation(i.e., replacing two Zn atoms by one Cu and one Ga). While cation-transmutated materials are common, aniontransmutated ternary materials are rare, for example, Zn_(2)As Br(i.e., replacing two Se atoms by one As and one Br)is not reported. The physical origin for this puzzling disparity is unclear. In this work, we employ first-principles calculations to address this issue, and find that the distinct differences in stability between cation-transmutated(mix-cation) and anion-transmutated(mix-anion) compounds originate from their different trends of ionic radii as functions of their ionic state, i.e., for cations, the radius decreases with the increasing ionic state, whereas for anions, the radius increases with the increasing absolute ionic state. Therefore, for mix-cation compounds,the strain energy and Coulomb energy can be simultaneously optimized to make these materials stable. In contrast, for mix-anion systems, minimization of Coulomb energy will increase the strain energy, thus the system becomes unstable or less stable. Thus, the trend of decreasing strain energy and Coulomb energy is consistent in mix-cation compounds, while it is opposite in mix-anion compounds. Furthermore, the study suggests that the stability strategy for mix-anion compounds can be controlled by the ratio of ionic radii r3/r1. with a smaller ratio indicating greater stability. Our work, thus, elucidates the intrinsic stability trend of transmutated materials and provides guidelines for the design of novel ternary materials for various device applications.

关键词： stability stability ternary

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