An elasto-plastic and viscoplastic damage constitutive model for dilatancy and fracturing behavior of soft rock squeezing deformation

Soft rock squeezing deformation mainly consists of pre-peak damage-dilatancy and post-peak fracture-bulking at the excavation unloading instant,and creep-dilatancy caused by time-dependent damage and fracturing.Based on the classic elastoplastic and Perzyna over-stress viscoplastic theories,as well as triaxial unloading confining pressure test and triaxial unloading creep test results,an elastoplastic and viscoplastic damage constitutive model is established for the short-and long-term dilatancy and fracturing behavior of soft rock squeezing deformation.Firstly,the criteria for each deformation and failure stage are expressed as a linear function of confining pressure.Secondly,the total damage evolution equation considering time-dependent damage is proposed,including the initial damage produced at the excavation instant,in which the damage variable increases exponentially with the lateral strain,and creep damage.Thirdly,a transient five-stages elasto-plastic constitutive equation for the short-term deformation after excavation that comprised of elasticity,pre-peak damage-dilatancy,post-peak brittle-drop,linear strain-softening,and residual perfectly-plastic regimes is developed based on incremental elasto-plastic theory and the nonassociated flow rule.Fourthly,regarding the timedependent properties of soft rock,based on the Perzyna viscoplastic over-stress theory,a viscoplastic damage model is set up to capture creep damage and dilatancy behavior.Viscoplastic strain is produced when the stress exceeds the initial static yield surface fs;the distance between the static yield surface fs and the dynamic yield surface fd determines the viscoplastic strain rate.Finally,the established constitutive model is numerically implemented and field applied to the-848 m belt conveyer haulage roadway of Huainan Panyidong Coal Mine.Laboratory test results and in-situ monitoring results validate the rationality of the established constitutive model.The presented model takes both the transient and time-dependent damage and fracturing into consideration.

An elasto-plastic constitutive model of moderate sandy clay based on BC-RBFNN

Application research of neural networks to geotechnical engineering has become a hotspot nowadays.General model may not reach the predicting precision in practical application due to different characteristics in different fields.In allusion to this,an elasto-plastic constitutive model based on clustering radial basis function neural network(BC-RBFNN) was proposed for moderate sandy clay according to its properties.Firstly,knowledge base was established on triaxial compression testing data;then the model was trained,learned and emulated using knowledge base;finally,predicting results of the BC-RBFNN model were compared and analyzed with those of other intelligent model.The results show that the BC-RBFNN model can alter the training and learning velocity and improve the predicting precision,which provides possibility for engineering practice on demanding high precision.

Elasto-plastic analysis of masonry with anisotropic plastic material model

This paper establishes an anisotropic plastic material model to analyze the elasto-plastic behavior of masonry in plane stress state.Being an anisotropic material,masonry has different constitutive relation and fracture energies along each orthotropic axes.Considering the unique material properties of masonry,a new yield criterion for masonry is proposed combining the Hill's yield criterion and the Rankine's yield criterion.The new yield criterion not only introduces compression friction coefficient of shear but also considers yield functions for independent stress state along two material axes of tension.To solve the involved nonlinear equations in numerical analysis,several nonlinear methods are implemented,including Newton-Raphson method for nonlinear equations and Implicit Euler backward mapping algorithm to update stresses.To verify the proposed material model of masonry,a series of tests are operated.The simulation results show that the new developed material model implements successfully.Compared with isotropic material model,the proposed model performs better in elasto-plastic analysis of masonry in plane stress state.The proposed anisotropic model is capable of simulating elasto-plastic behavior of masonry and can be used in related applications.

Nonlinear constitutive models of rock structural plane and their applications

Structural planes play an important role in controlling the stability of rock engineering,and the influence of structural planes should be considered in the design and construction process of rock engineering.In this paper,mechanical properties,constitutive theory,and numerical application of structural plane are studied by a combination method of laboratory tests,theoretical derivation,and program development.The test results reveal the change laws of various mechanical parameters under different roughness and normal stress.At the pre-peak stage,a non-stationary model of shear stiffness is established,and threedimensional empirical prediction models for initial shear stiffness and residual stage roughness are proposed.The nonlinear constitutive models are established based on elasto-plastic mechanics,and the algorithms of the models are developed based on the return mapping algorithm.According to a large number of statistical analysis results,empirical prediction models are proposed for model parameters expressed by structural plane characteristic parameters.Finally,the discrete element method(DEM)is chosen to embed the constitutive models for practical application.The running programs of the constitutive models have been compiled into the discrete element model library.The comparison results between the proposed model and the Mohr-Coulomb slip model show that the proposed model can better describe nonlinear changes at different stages,and the predicted shear strength,peak strain and shear stiffness are closer to the test results.The research results of the paper are conducive to the accurate evaluation of structural plane in rock engineering.

Demand Elasticity for China's Major Imported Agriculture Textile Material Based on Restricted Version of Source Differentiated Almost Ideal Demand System Model

By comparing China's import of major imported agriculture textile material( cotton and wool),the characteristics of import are concluded. On this basis,a restricted version of source differentiated almost ideal demand system( RSDAIDS) is used to estimate the income and price elasticity of major imported agriculture textile material from the major sources based on the data from 1992 to 2015. The results are shown as follows.( 1) Although the dependency on imported cotton is lower than wool, the fluctuation of cotton import is much more drastic; China's demand for cotton is relatively price elastic with higher expenditure elasticity compared with wool; besides,the existence of complementarity is proved between imported cotton and wool.( 2) According to the import elasticity of cotton,demand for cotton imported from India shows priority over cotton from other sources; demand for cotton imported from America is the most price-sensitive one; substitution among cotton from different sources is weak.( 3) According to the import elasticity of wool,wool imported from Uruguay has bright market prospects. In addition,wool imported from Australia has irreplaceable advantage than that from New Zealand.

Study of the Influence of Nanoparticles on the Molecular Model of an Ideal Fluid

In the article a molecular model of oil with nanoparticles on the basis of the model of ideal fluid is considered. It is assumed that the molecular model of the oil can be represented as a homogenous distribution of identical molecules in space. It is assumed that the central interaction between the oil molecules and nanoparticles, results in a change of the model parameters. It is shown that for an ideal fluid the effect of nanoparticles is reduced to a change of the coefficient at the pressure.

A Finite-Mode Model of Ideal Fluid Dynamics on the 2-Sphere

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A Numerical Simulation of Air Flow in the Human Respiratory System Based on Lung Model

The lung is an important organ that takes part in the gas exchange process. In the study of gas transport and exchange in the human respiratory system, the complicated process of advection and diffusion (AD) in airways of human lungs is considered. The basis of a lumped parameter model or a transport equation is modeled during the inspiration process, when oxygen enters into the human lung channel. The quantitative measurements of oxygen are detached and the model equation is solved numerically by explicit finite difference schemes. Numerical simulations were made for natural breathing conditions or normal breathing conditions. The respiratory flow results for the resting conditions are found strongly dependent on the AD effect with some contribution of the unsteadiness effect. The contour of the flow rate region is labeled and AD effects are compared with the variation of small intervals of time for a constant velocity when breathing is interrupted for a negligible moment.

基于理想过程模型的探究学习评价——探究学习评价的新思路

在教育情境下,探究学习被定义为旨在达到特定高阶能力目标的学习过程。因此,其评价应侧重于过程取向,而非结果取向。为刻画理想的探究学习过程并保留情境信息,特别是学习目标信息,需对特定的探究学习设计进行理想过程建模,所生成的理想过程模型可作为评价实际发生的探究学习的标尺。探究学习的理想过程建模包括以下五个步骤:(1)完成探究学习的详案设计;(2)绘制探究学习活动所蕴含的知识建模图;(3)具体描述探究学习的整体过程;(4)将探究学习整个过程划分为多个环节,并绘制探究环节图;(5)将所有环节图按照探究学习的一般过程连接成一个整体,形成理想过程模型。对实际发生的探究学习也应进行上述操作,并在完成预处理后,生成探究学习的真实过程模型。通过比较真实过程模型与理想过程模型,找出差异点,依此可以评估实际发生的探究学习。这种评价方法不仅有助于了解探究学习的质量,还能为探究学习设计的改进提供反馈,更为重要的是,它可以使探究学习成为日常教学的一部分。

高压氢气泄漏过程中气体参数计算的新方法

基于气体等熵喷射过程和绝热变化过程分析氢气泄漏的热力学过程,建立理想气体状态方程、Abel-Noble状态方程和基于NIST(National Institute of Standards and Technology)的真实气体状态方程的计算模型,利用MATLAB对稳态/非稳态泄漏过程进行计算。结果显示,建立的稳态泄漏模型能够精确计算泄漏口处的相关参数,在保证计算精度的前提下与数值模拟相比,误差可以忽略不计;非稳态泄漏模型中,与基于理想气体状态方程和Abel-Noble状态方程相比,基于NIST的真实气体状态方程误差更小;非稳态泄漏过程中,罐内气体温度高于理论预测值,泄漏质量流量小于理论预测值。真实气体模型在一定程度上体现了热力学模型的局限性,但与数值模拟等计算方法相比,该模型计算更加快捷精准,对实际气体泄漏事故的预测具有理论指导意义。

共享制造环境下基于Z-RIM的QoS多方异质评价方法

为解决共享制造环境下决策信息异质、候选服务数量动态变化的制造服务QoS评价问题,基于平台、服务需求方、服务提供方的三方决策信息,提出一种符合共享制造特点的QoS多方异质制造服务评价方法。通过精确数、语言变量和Z-number处理异质信息;基于共识最大化计算决策方权重向量,利用TrFWAA算子集结多方信息,依据离差最大化模型计算属性权重;在此基础上,采用RIM对各服务进行评估。结合共享制造环境下的制造业服务优选案例对提出的方法进行验证分析,结果表明该方法具有较好的实用性和优越性。

基于知识工程的面向船体结构总体振动的计算网格生成方法

根据结构总体振动计算网格生成的工程需求,分析其具体使用要求与实现难点,结合知识工程的理论,开展基于3DExperience三维设计软件中的知识工程工具的分析,主要包括基于三维模型的知识表达、知识推理技术,提出具体的生成面向结构总体振动网格的实施方案,并通过某客滚船项目进行验证,结果表明,知识工程具有普适性、与设计模型强关联、开发成本低等特点,在船舶领域有极大的应用前景。

基于云-TOPSIS法的应急物流供应商综合评价

为实现应急物流降本增效的目标,从供应商层面出发,运用云-逼近理想解排序法(TOPSIS)评价应急物流供应商综合能力;根据应急物流特点,从应急响应能力、物资质量、成本控制、应急响应柔性、企业内外部条件等5方面,构建应急物流供应商综合评价指标体系;借鉴博弈论思想,将用改进熵权法求得的客观权重和用层次分析法(AHP)求得的主观权重作为博弈对手,确定最优组合权重;运用云模型量化指标决策云和加权云对供应商的模糊定性评价语义;采用TOPSIS法构建正负理想解集合,计算备选方案与正负理想解的距离确定相对贴近度,确定最优备选方案。研究结果表明:指标决策云能准确地将评价语言量化,云-TOPSIS法的评价结果更合理;在供应商相对贴近度排序中,采用云-TOPSIS法计算的最优与最劣者差值为0.3315,而TOPSIS法为0.0882,两者相差0.2433,表明云-TOPSIS法的评价结果区分度更大,能更直观地辅助决策者做出最优选择。

住宅小区理想规模的模型探究——基于共有空间社会密度的视角

住宅小区内共有空间的社会密度会对居民间的邻里交往产生显著影响。为保证住宅小区共有空间资源的数量和品质,在第Ⅲ建筑气候区条件下建立小区模型,对不同类型小区的共有空间进行分析。结果显示,随着小区内建筑平均层数的增加,户均共有空间资源的数量逐渐减少,共有空间的品质在空间尺度、围合度、私密性等维度上显著降低。基于模型研究结果和城市对土地利用的要求,进而提出住宅小区的理想规模为3~4 hm2,住宅平均层数宜为5~8层,而当确有需要建设高层住宅时,住宅平均层数也不宜超过14层。

旋转爆震火箭发动机推进性能分析

针对旋转爆震发动机(Rotating Detonation Engine,RDE)燃烧室简化二维流场,采用流场分区,建立了一种适用于RDE工作特性的性能分析模型,可快速准确地估算RDE的推进性能。模型考虑了燃烧室内气流膨胀过程中的气流角度匹配,可准确描述存在单个爆震波时的基本流场结构特征,包括爆震波倾斜角度、斜激波角度、滑移线角度等,结果与已有文献的研究结果一致性较高。根据模型流场中所取控制体的进出口参数,可得理想膨胀状态下RDE的推进性能,估算结果与已有性能估算模型吻合较好,与已有实验数值偏差为8%。经验证推导,模型亦可用于多波模态。采用该性能分析模型对比研究了不同反应物当量比、进气总压和总温下火箭式RDE的推进性能。研究表明,性能分析模型可准确反映RDE燃烧室的非稳态流场特征,且可快速准确地估算RDE的推进性能,为RDE推进性能的评估提供了简便可靠的方法。

IDEAL模型的研究

首先介绍了软件过程能力成熟度模型 (SW CMM)及其实施方法论IDEAL模型的概念 ,接着阐明了IDEAL模型各个阶段的目的、任务和软件过程改进的管理 ,举例说明了用PDCA周期实施软件过程改进 ,并对ICASE模型进行了简单说明。最后结合中国传统文化和信息时代的特点对SW CMM实施方法论进行了若干讨论。

三维理想河口盐水入侵对径潮驱动变化的响应

为探究在人类活动与气候条件改变的影响下,径潮动力以及水深的改变对河口区域盐水入侵的影响,建立了三维理想河口盐水入侵数值模型,分析了纵向环流及盐度的垂向与横向沿程分布,研究了垂向与横向剪切作用以及潮泵效应引起的纵向盐输运对盐水入侵的影响以及盐分输运过程对径潮动力与水深变化的响应。结果表明:盐水上溯程度对流量与潮振幅的变化有明显响应,流量增大与潮振幅增大对盐水入侵均有抑制作用;在较浅的河口,潮驱动增大在河口上下游引起相反的潮平均盐度变化趋势,这与横向、纵向剪切与潮泵效应分别引起的纵向盐输运对径潮水深条件的响应相关。

基于逼近理想解排序法模型的大型医疗设备管理质量评价

目的:研究基于逼近理想解排序法(TOPSIS)模型的大型医疗设备管理质量评价,以改善医疗设备管理质量评价效果。方法:采用文献分析及专家咨询方式初步确定医疗设备管理质量评价指标,采用主基底分析法对评价指标初选结果作为变量筛选,以降低原始评价指标数据维度,获得具有突出代表性的简化指标集合,通过熵权法计算各评价指标权重,利用TOPSIS模型确定各评价目标至正、负理想解的距离,依据该距离计算评价对象与最优管理方案间的贴合度,基于贴合度分值实现大型医疗设备管理质量等级确定。选取2022年北京朝阳医院、北京中医药大学第三附属医院等医院临床在用的82台大型医疗设备,采用TOPSIS模型对大型医疗设备管理质量进行评价,分析设备管理质量评价效果与实际设备管理质量结果的差异性。结果:基于TOPSIS模型的大型医疗设备管理质量评价指标包含4个一级指标、9个二级指标和16个三级指标。采用该评价指标对医院的大型医疗设备管理质量进行评价,评价结果与实际管理质量结果基本一致,二者在同一等级区间。结论:TOPSIS模型用于医疗机构大型医疗设备管理质量评价,可实现评价指标权重计算和医疗设备管理质量等级评估,质量评价结果与实际设备管理质量相符。

考虑中频变压器非理想几何结构的通用漏感解析模型

中频变压器非理想几何结构引起的畸变磁场对漏感解析计算精度有较大影响,进而影响变压器设计及变换器运行特性和效率特性。首先针对副边绕组为非理想几何结构的漏感解析计算问题,基于叠加定理和洛氏高度等效方法,将传统只考虑纵向漏磁场的一维模型,改进为综合考虑纵向和横向漏磁场的二维模型,显著提升计算精度,并依据此模型提出一种通用漏感优化方法。进一步,针对原副边均为非理想几何结构情况,引入洛氏叠加区域,将原副边非正交且耦合的横向漏磁场能量考虑在内,提出一种计及中频变压器非理想几何因素的通用解析模型,计算误差在7.5%以下。仿真和实验验证了模型的准确性和通用性。