Improved Staggered Algorithm for Phase-Field Brittle Fracture with the Local Arc-Length Method

The local arc-length method is employed to control the incremental loading procedure for phase-field brittle fracture modeling.An improved staggered algorithm with energy and damage iterative tolerance convergence criteria is developed based on the residuals of displacement and phase-field.The improved staggered solution scheme is implemented in the commercial software ABAQUS with user-defined element subroutines.The layered system of finite elements is utilized to solve the coupled elastic displacement and phase-field fracture problem.A one-element benchmark test compared with the analytical solution was conducted to validate the feasibility and accuracy of the developed method.Our study shows that the result calculated with the developed method does not depend on the selected size of loading increments.The results of several numerical experiments show that the improved staggered algorithm is efficient for solving the more complex brittle fracture problems.

The Numerical Modeling of 3-D Elastic Wave Equation Using a High-Order,Staggered-Grid, Finite Difference Scheme

This article provides the application of the high-order, staggered-grid, finite-difference scheme to model elastic wave propagation in 3-D isotropic media. Here, we use second-order, temporal-and high-order spatial finite-difference formulations with a staggered grid for discretization of the 3-D elastic wave equations of motion. The set of absorbing boundary conditions based on paraxial approximations of 3-D elastic wave equations are applied to the numerical boundaries. The trial resuits for the salt model show that the numerical dispersion is decreased to a minimum extent, the accuracy high and diffracted waves abundant. It also shows that this method can be used for modeling wave propagation in complex media with the lateral variation of velocity.

Quantum Monte Carlo study on the phase transition for a generalized two-dimensional staggered dimerized Heisenberg model

In order to gain a deeper understanding of the quantum criticality in the explicitly staggered dimerized Heisenberg models, we study a generalized staggered dimer model named the J0 J1 J2 model, which corresponds to the staggered j-j′ model on a square lattice and a honeycomb lattice when J1/J0 equals 1 and O, respectively. Using the quantum Monte Carlo method, we investigate all the quantum critical points of these models with J1/J0 changing from 0 to 1 as a function of coupling ratio a = J2/J0. We extract all the critical values of the coupling ratio ac for these models, and we also obtain the critical exponents v,β/ν, and η using different finite-size scaling ansatz,. All these exponents are not consistent with the three-dimensional Heisenberg universality class, indicating some unconventional quantum ciriteial points in these models.

Effects of Staggered Magnetic Field on Entanglement in the Anisotropic XY Model

我们调查效果蹒跚磁性在各向异性的 XY 模型在热纠纷上删除。为二地点的案例的纠纷的分析结果被获得。为甚至地点的一般案例，我们证明当各向异性的参数是零时，在有一个蹒跚的磁场的 XY 模型的纠纷与一个一致磁场与那一样。

Accuracy of the staggered-grid finite-difference method of the acoustic wave equation for marine seismic reflection modeling

Seismic wave modeling is a cornerstone of geophysical data acquisition, processing, and interpretation, for which finite-difference methods are often applied. In this paper, we extend the velocity- pressure formulation of the acoustic wave equation to marine seismic modeling using the staggered-grid finite-difference method. The scheme is developed using a fourth-order spatial and a second-order temporal operator. Then, we define a stability coefficient (SC) and calculate its maximum value under the stability condition. Based on the dispersion relationship, we conduct a detailed dispersion analysis for submarine sediments in terms of the phase and group velocity over a range of angles, stability coefficients, and orders. We also compare the numerical solution with the exact solution for a P-wave line source in a homogeneous submarine model. Additionally, the numerical results determined by a Marmousi2 model with a rugged seafloor indicate that this method is sufficient for modeling complex submarine structures.

Staggered Quadrupolar Phase and Bicritical Point of Spin-1 Bond and Anisotropy Dilution Blume-Emery-Griffiths Model

在有效领域理论(水蜥) 以内，蹒跚 quadrupolar 阶段和双性人 spin-1 债券和 anisotropy 冲淡布鲁坶钢玉粉 Griffiths 模型的批评的点在四乘幂的相互作用和双线性的相互作用比率 α ≤ 的限制范围在简单立方的格子上被学习-1。阶段图论述一根线蹒跚 quadrupolar 顺磁(SQ-P ) 阶段和一根线铁磁性顺磁(F-P ) 分阶段执行，由一个双性人分开了批评的点(BCP ) 。大否定比率和二个不同冲淡因素在 T-α 或 T-D 飞机放大 SQ 阶段的范围和铁磁性的阶段的还原剂范围。这些参数能帮助 SQ-P 线的重入的行为并且压制 F-P 线的。BCP 上的契约冲淡的影响对 anisotropy 冲淡的不一样。以在 T-D 飞机的地面状态有一个退化模式。一些结果获得了由纯恳求模型在对蒙特卡罗模拟的结果的质的同意。

A scheme to treat the singularity in global seismic wavefield simulation using pseudospectral method with staggered grids

The pseudospectral method has been applied to the simulation of seismic wave propagation in 2-D global Earth model. When a whole Earth model is considered, the center of the Earth is included in the model and then singularity arises at the center of the Earth where r=0 since the 1/r term appears in the wave equations. In this paper, we extended the global seismic wavefield simulation algorithm for regular grid mesh to staggered grid configuration and developed a scheme to solve the numerical problems associated with the above singularity for a 2-D global Earth model defined on staggered grid using pseudospectral method. This scheme uses a coordinate transformation at the center of the model, in which the field variables at the center are calculated in Cartesian coordinates from the values on the grids around the center. It allows wave propagation through the center and hence the wavefield at the center can be stably calculated. Validity and accuracy of the scheme was tested by compared with the discrete wavenumber method. This scheme could also be suitable for other numerical methods or models parameterized in cylindrical or spherical coordinates when singularity arises at the center of the model.

3D numerical simulation in acoustic-elastic coupled media with staggered-grid finite-difference method

Acoustic-elastic coupled media is often encountered in most marine explorations, and accurate simulation of acoustic-elastic coupled media is of great significance. At present, the study of acoustic-elastic coupled media still assumes that the solid of the acoustic-elastic coupled media is isotropic, but this assumption is not in accordance with the actual situation. In this paper, we derive the solid media of acoustic-elastic coupled media from isotropic media to anisotropic media, and propose an acoustic-elastic coupled medium based ontransverse isotropic media with vertical symmetric axes(VTI) to improve the accuracy of forward modeling. Based on the relationship between the Thomsen parameter and the coefficient matrix of the anisotropic elastic wave equation, we transform the Thomson parameter into a velocity model with anisotropic properties. We use a staggered grid finite difference method to simulate the propagation of a wavefield in a three-dimensional acoustic-elastic coupled media. We obtain the snapshots of the wave field when the solid of the acoustic-elastic coupled media is an isotropic medium and a VTI media. When the solid of the acoustic-elastic coupled media is considered VTI media, we can observe the qP wave and qS wave that cannot be observed in the isotropic medium from the wave field snapshot. We can also find that the seismic records obtained by the method we use are more realistic. The algorithm proposed in this paper is of great significance for high-precision ocean numerical simulation.

窄河谷大夹角挑流消能工体型优化研究

针对窄河谷大夹角条件下挑流消能易出现冲击两岸、冲坑过深的问题,采用水工整体模型试验方法对具有代表性的某水利枢纽深孔放水冲沙洞挑流鼻坎体型开展优化研究,并对比分析了水舌形态和下游河道冲刷特性。结果表明,不对称收缩的异型窄缝式消能工可使水流在狭窄河道归槽,水舌纵向拉伸效果较好,大幅减轻了河床冲刷;提出了收缩比、收缩角差、斜切面积比等特征参数适宜的挑流消能工体型,可供窄河谷大夹角条件下挑流消能设计参考。

知识产权战略与企业数字化转型--基于渐进双重差分模型的实证分析

知识产权示范城市作为国家知识产权战略实施的先行示范区发挥着重要作用,知识产权战略对企业数字化转型也有积极意义。基于2008—2021年沪深A股上市公司数据,使用渐进双重差分模型(DID)验证知识产权战略是否对企业数字化转型产生影响。结果表明,知识产权战略能够显著赋能企业数字化转型,通过平行趋势和动态效应检验、安慰剂检验和倾向得分匹配等多种稳健性检验后,结论依然成立;从作用机制来看,知识产权战略通过专利补贴促进效应和技术创新激励效应显著赋能企业数字化转型。

农地确权对农民市民化的影响研究

农地确权为农民土地提供法律保护,理论上有助于推动农民市民化。本文利用2013—2019年间四期中国农村家庭追踪调查数据和渐进DID模型,实证考察农地确权对农民市民化的影响。研究发现,农地确权通过促进非农就业改善农民市民化行为,且这种效应在非粮食主产区和人口净流入省份更为明显;农地确权也提高了农民市民化意愿,该效应在所有成员为农业户籍的家庭中更为突出。因此,未来既要因地制宜,消除进城农民失去土地的顾虑,也要因户施策,开通农民城市落户的绿色通道。

超高速碰撞下相变效应的交错网格物质点法研究

超高速碰撞下的结构毁伤过程常伴随材料相变、断裂失效及碎片云的产生与演化,其所具有的压力强间断、材料非线性等几何大变形等问题给数值模拟带来了困难。交错网格物质点法SGMP通过背景网格格心积分消除了物质点法MPM跨网格误差,是模拟固体冲击爆炸等极端大变形与材料破坏问题的一种有效数值分析方法。本文将含金属相变的GRAY状态方程及含非线性内聚力断裂的Johnson-Cook修正金属模型引入SGMP中,模拟超高速碰撞单层、多层靶板问题。结果表明,SGMP和修正金属模型可以很好地模拟超高速碰撞问题中的碎片云形貌特征和相变效应。

低碳转型政策对上市公司环境-社会责任-公司治理的影响及作用机制

全面建设社会主义现代化国家的战略部署对中国经济社会发展的绿色低碳转型提出了新的要求。企业作为推进这一凤凰涅槃过程的核心主体,其践行环保减排、承担绿色责任的激励机制已经成为社会和学界关注的热点。该研究以低碳城市试点政策的实施作为一项代表性低碳转型政策和准自然实验,基于2009—2021年中国上市公司的微观数据,运用渐进双重差分模型考察了该政策实施对上市公司环境-社会责任-公司治理(ESG)质量的影响及作用机制。研究发现:①中国自2010年以来实施的低碳城市试点政策显著提升了上市公司的ESG质量,该政策使试点城市上市公司的ESG指数平均提高了27.42%,且这一结果在排除其他政策干扰、倾向得分匹配、安慰剂检验等一系列稳健性检验后依旧可靠。②在该政策的影响下,来自政府监管和公众舆论监督的压力是企业自主改善ESG质量的重要动因。③通过绿色金融支持缓解企业融资约束和推动企业绿色技术创新,是低碳转型政策改善企业ESG质量的重要机制。其中,绿色技术创新表现为量质齐升的良好态势,且能源节约类绿色技术的创新水平和质量提升在低碳城市试点政策改善企业ESG质量过程中发挥着更重要的作用。该研究表明,中国的低碳城市试点政策不仅在宏观层面推动了区域绿色低碳转型,在微观上也促进了企业践行低碳转型理念、承担可持续发展和绿色发展责任,这在丰富和补充企业ESG质量影响因素研究内容的同时,也为我国实现“双碳”目标提供了一定的学理支持和决策依据。

标准治理是否促进区域经济高质量发展——标准化综合改革试点的准自然实验

标准化是形成科学有效社会治理体制的基础工程,标准治理因其多元、高效、可复制性而成为推动经济高质量发展的基础性、引领性手段。研究标准政策的实施效应可以为多方面推动经济高质量发展提供经验依据。基于2004—2020年中国省级面板数据,围绕创新、协调、绿色、开放、共享五大维度对经济高质量发展水平进行测算,借助标准化综合改革这一试点政策,运用多期双重差分模型探究标准治理对区域经济高质量发展的影响,并探讨环境规制在标准治理与经济高质量发展中的调节作用。研究结果表明,标准治理显著促进区域经济高质量发展,其中,标准治理显著地促进了经济高质量发展的创新发展、协调发展、绿色发展和开放发展,而对经济共享发展并没有产生直接影响;机制检验证实环境规制水平的提高对标准治理影响经济高质量发展起到先抑制后促进的作用;异质性分析发现标准治理对东部地区以及标准发展水平较高地区的经济高质量发展促进效果更明显。因此,要通过重点加强政府的公共管理与服务的标准化水平,优化资源要素配置,实现经济共享发展,同时根据不同的经济发展阶段设置合理的环境规制强度以加快经济绿色增长,促进经济高质量发展。

Resistance Analysis of Unsymmetrical Trimaran Model with Outboard Sidehulls Configuration

河和海环境里的运输的一个模式在最近的年里很快成长了的多壳轮船或三个船体并列的游艇容器的申请。三个船体并列的游艇容器由于能被完成的水动力学效率的高水平当前具有为许多新高速度轮船工程的兴趣，与相比单音壳并且长筏壳表格。这研究的目的是识别与配置(S/L ) 使用一个不对称的三个船体并列的游艇轮船模型的可能的效果 0.10.3 并且 R/L=0.10.2。有主要尺寸的不对称的三个船体并列的游艇轮船模型：L=2000mm， B=200 公里和 T=45 公里。试验性的方法(拖引的坦克) 在第 0.10.6 期弗鲁德点用速度变化在学习被执行。轮船模型被其速度能被改变并且调整的一台电动机拉。轮船模型抵抗被使用一个负担房间变换器精确测量。为每种配置与的轮船抵抗的比较单音壳作为全部的抵抗系数和弗鲁德数字的功能在图上被显示出。测试结果发现有效拖减小能与配置 S/L=0.1 在 Fr=0.35 被完成直到 17% 。

The parallel 3D magnetotelluric forward modeling algorithm

3D 磁电机的工作量碲的向前当模特儿的算法那么大传统的连续算法花费一极其大计算时间。然而，向前为算法建模的 3D 能在频率域处理数据，它对平行计算很合适。与 MPI 并且基于 3D 磁电机的流动的分析的优点碲的连续前面的算法，我们建议平行计算的想法并且使用它。三个理论模型被测试，实行效率处于不同状况被比较。结果显示向前为计算建模的平行 3D 是正确的，效率极大地被改进。这个方法对大尺寸合适地球物理的计算。

Multi-wave forward modeling of a reservoir and AVO analysis

In the process of accurate interpretation of multi-wave seismic data,we wanted to solve the problem of multi-wave information recognition.Based on techniques of elastic wave forwarding,targeting the geological model of a reservoir of an oil field exploration area,we used a high-order staggered-grid difference technology to simulate many shots of seismic records of nonzero offset shots,implemented multi-wave seismic data processing to acquire the CMP of P waves and converted waves,NMO traces of CCP pre stacks,including AVA information and superposition profiles.Based on the AVA calculation of the model,the layer parameters of the model and the forwarding wave field relations of the P-S wave,we also compared and studied the correspondence between P waves and converted waves.The results of our analysis show that the results from simulation and from the AVO analysis are consistent.Significant wave field differences between P waves and converted waves in the same reservoir were found,which are helpful in recognizing and interpreting the multi-wave information in this area.We made use of the multi-wave data to provide the important guidelines for reservoir prediction.

数字基础设施建设与城市创新质量——基于长江经济带110个地级市的实证分析

中国创新驱动正由数量增长转向质量提升,提升创新质量是驱动经济高质量发展的关键一环。文章基于2010—2020年长江经济带110个地级市面板数据,在理论分析数字基础设施建设影响城市创新质量内在机理的基础上,以“宽带中国”示范政策为准自然实验构建渐进双重差分模型,系统考察数字基础设施建设对长江经济带城市创新质量的影响效应。研究发现:数字基础设施建设对长江经济带城市创新质量具有显著提升作用,且该结论通过了一系列稳健性检验;机制分析表明,数字基础设施建设通过增强人才集聚、提高互联网发展水平和强化政府战略引领等途径促进了城市创新质量提升;异质性分析表明,数字基础设施建设对长江经济带一般城市和上游、中游地区的创新质量提升作用更明显。研究结论为进一步推动创新驱动发展战略和数字中国建设提供了参考和借鉴。

低碳城市试点政策能提高重污染企业全要素生产率吗?

在全球变暖的大背景下,以碳减排为主要目标的低碳城市试点政策是我国应对气候变化、推动绿色低碳发展的重要举措。以2008—2020年全部A股重污染上市公司与企业所在城市匹配的面板数据为样本,利用多期双重差分模型考察低碳城市试点政策对重污染企业全要素生产率的影响。研究发现,低碳城市试点政策通过促进企业技术创新、缓解融资约束和提高资源配置效率三个传导机制提升了重污染企业全要素生产率;低碳城市试点政策对企业全要素生产率的影响在不同企业、不同地区存在显著差异。应完善对试点城市的考核机制,因地制宜开展低碳城市试点政策,实现重污染企业绿色低碳转型。

串列布置不同容量风力机输出功率的数值模拟

为了研究垂直交错布置方式布置不同风力机对其输出功率的影响,本文利用OpenFOAM开源软件,使用致动线模型和RANS结合标准k-ε模型的数值方法,对采用5种布置方式的WindPACT 1.5 MW(WP 1.5 MW)风力机和两种不同轮毂高度的NREL 5 MW风力机的风电场进行研究。研究表明:将两台WP 1.5 MW风力机中的一台风力机替换为NREL5 MW风力机可有效提高风电场总输出功率。将上游风力机替换可以更大地提升风电场总输出功率,总输出功率提升了104.12%;提高NREL 5 MW风力机的轮毂中心高度,形成垂直交错风电场时可以增加上下游风力机的输出功率,进而能够更好地利用垂直方向上的风资源。将下游NREL 5 MW风力机轮毂中心高度提升0.5D能更大程度提升风电场的总输出功率,总输出功率提升了132.79%。