Development and Application of a Power Law Constitutive Model for Eddy Current Dampers

Eddy current dampers (ECDs) have emerged as highly desirable solutions for vibration control due to theirexceptional damping performance and durability. However, the existing constitutive models present challenges tothe widespread implementation of ECD technology, and there is limited availability of finite element analysis (FEA)software capable of accurately modeling the behavior of ECDs. This study addresses these issues by developing anewconstitutivemodel that is both easily understandable and user-friendly for FEAsoftware. By utilizing numericalresults obtained from electromagnetic FEA, a novel power law constitutive model is proposed to capture thenonlinear behavior of ECDs. The effectiveness of the power law constitutive model is validated throughmechanicalproperty tests and numerical seismic analysis. Furthermore, a detailed description of the application process ofthe power law constitutive model in ANSYS FEA software is provided. To facilitate the preliminary design ofECDs, an analytical derivation of energy dissipation and parameter optimization for ECDs under harmonicmotionis performed. The results demonstrate that the power law constitutive model serves as a viable alternative forconducting dynamic analysis using FEA and optimizing parameters for ECDs.

Exact Solutions of a Power Law Fluid Model in Posttreatment Analysis of Wire Coating with Linearly Varying Boundary Temperature

In this paper, analysis of post-treatment of wire coating is presented. Coating material satisfies power law fluid model. Exact solutions for the velocity field, volume flow rate and average velocity are obtained. Moreover, the heat transfer results are presented for different cases of linearly varying on the boundaries. The variations of velocity, volume flow rate, radius of coated wire, shear rate and the force on the total wire are presented graphically and discussed.

Simplified Wave Models Applicability to Shallow Mud Flows Modeled as Power-Law Fluids

Simplified wave models- such as kinematic,diffusion and quasi-steady- are widely employed as a convenient replacement of the full dynamic one in the analysis of unsteady open-channel flows,and especially for flood routing.While their use may guarantee a significant reduction of the computational effort,it is mandatory to define the conditions in which they may be confidently applied.The present paper investigates the applicability conditions of the kinematic,diffusion and quasisteady dynamic shallow wave models for mud flows of power-law fluids.The power-law model describes in an adequate and convenient way fluids that at low shear rates fluids do not posses yield stress,such as clay or kaolin suspensions,which are frequently encountered in Chinese rivers.In the framework of a linear analysis,the propagation characteristics of a periodic perturbation of an initial steady uniform flow predicted by the simplified models are compared with those of the full dynamic one.Based on this comparison,applicability criteria for the different wave approximations for mud flood of power-law fluids are derived.The presented results provide guidelines for selecting the appropriate approximation for a given flow problem,and therefore they may represent a useful tool for engineering predictions.

Francis Turbine and Governor Improved Models Considering Step Closing Law of Guide Vanes for Power System Stability Analysis

The Francis turbine governing system models in PSD-BPA can’t precisely reflect the actual characteristics. Endeavor was done in this paper to solve the problem. An improved model of actuating mechanism was developed, which could reflect the step closing characteristic of hydro guide vanes. The effect of the inflection point value of actuating mechanism on load rejection was analyzed based on simulation. The non-linear Francis turbine model with power versus gate position module was researched in this paper. Based on field test, comparisons of simulation results with measured data were presented. The analysis demonstrates that the improved models of Francis turbine and governor proposed in this paper are more realistic than the models of BPA, and can be applied in power system simulation analysis better.

隧洞平行摄影测量立体影像尺度差估计及匹配优化

为提升平行摄影隧洞序列影像的同名点匹配率及精度,对成像规律及匹配方法展开研究。提出了一种窗口尺度自动改正的LK光流法,核心是利用物像空间关系构建尺度差模型,并采用可变窗口进行特征点光流跟踪。结果表明:隧洞序列影像像点尺度差呈对称性径向分布,差异值符合幂函数模型增长趋势;将该方法应用在多组尺度差立体像对的匹配实验中,均取得了优于0.3个像素精度的实验结果,较基本光流法至少提升34.3%,最大提升45.5%。研究成果可为顾及尺度差的匹配方法提供参考,也可为隧洞平行摄影立体影像匹配提供基础。

Novel extended C-m models of flow stress for accurate mechanical and metallurgical calculations and comparison with traditional flow models

Here,we developed novel extended piecewise bilinear power law(C-m)models to describe flow stresses under broad ranges of strain,strain rate,and temperature for mechanical and metallurgical calculations during metal forming at elevated temperatures.The traditional C-m model is improved upon by formulating the material parameters C and m,defined at sample strains and temperatures as functions of the strain rate.The coefficients are described as a linear combination of the basis functions defined in piecewise patches of the sample strain and temperature domain.A comparison with traditional closed-form function flow models revealed that our approach using the extended piecewise bilinear C-m model is superior in terms of accuracy,ease of use,and adaptability;additionally,the extended C-m model was applicable to numerical analysis of mechanical,metallurgical,and microstructural problems.Moreover,metallurgy-related values can be calculated directly from the flow stress information.Although the proposed model was developed for materials at elevated temperatures,it can be applied over a broad temperature range.

下垫面非均匀流域的幂指数TOPMODEL的模拟研究

利用取消流域土壤表层饱和导水率0K、土壤饱和导水率有效衰减系数m和地下水补给速率R为空间均匀假设的幂指数TOPMODEL,对流域水量平衡各分量进行敏感性研究试验,揭示空间非均匀性对幂指数TOPMODEL模拟结果的影响。从特定研究流域所得结果中可得的主要结论有:1)0K、m和R的空间变化对流域的逐日地表径流和基流以及逐日总径流有影响,针对设定的0K、m和R的空间变化,其中m的空间变化较明显地增加了逐日地表径流和洪峰流量。2)就设定的0K、m和R的空间变化而论,对流域多年平均年总径流以及蒸发模拟结果影响不大,但改变了径流在地表径流和基流之间的分配;其中R的空间变化影响最显著,m和0K的空间变化影响则较小。

Modeling online social networks based on preferential linking

We study the phenomena of preferential linking in a large-scale evolving online social network and find that the linear preference holds for preferential creation, preferential acceptance, and preferential attachment. Based on the linear preference, we propose an analyzable model, which illustrates the mechanism of network growth and reproduces the process of network evolution. Our simulations demonstrate that the degree distribution of the network produced by the model is in good agreement with that of the real network. This work provides a possible bridge between the micro=mechanisms of network growth and the macrostructures of online social networks.

Rheology of rock salt for salt tectonics modeling

Numerical modeling of salt tectonics is a rapidly evolving field; however, the constitutive equations to model long-term rock salt rheology in nature still remain controversial. Firstly, we built a database about the strain rate versus the differential stress through collecting the data from salt creep experiments at a range of temperatures（20–200 ℃） in laboratories. The aim is to collect data about salt deformation in nature, and the flow properties can be extracted from the data in laboratory experiments.Moreover, as an important preparation for salt tectonics modeling, a numerical model based on creep experiments of rock salt was developed in order to verify the specific model using the Abaqus package. Finally, under the condition of low differential stresses, the deformation mechanism would be extrapolated and discussed according to microstructure research. Since the studies of salt deformation in nature are the reliable extrapolation of laboratory data, we simplified the rock salt rheology to dislocation creep corresponding to power law creep（n = 5） with the appropriate material parameters in the salt tectonic modeling.

A local-world evolving hypernetwork model

Complex hypernetworks are ubiquitous in the real system. It is very important to investigate the evolution mecha- nisms. In this paper, we present a local-world evolving hypernetwork model by taking into account the hyperedge growth and local-world hyperedge preferential attachment mechanisms. At each time step, a newly added hyperedge encircles a new coming node and a number of nodes from a randomly selected local world. The number of the selected nodes from the local world obeys the uniform distribution and its mean value is m. The analytical and simulation results show that the hyperdegree approximately obeys the power-law form and the exponent of hyperdegree distribution is 7 = 2 ＋ 1/m. Furthermore, we numerically investigate the node degree, hyperedge degree, clustering coefficient, as well as the average distance, and find that the hypemetwork model shares the scale-flee and small-world properties, which shed some light for deeply understanding the evolution mechanism of the real systems.

Critical Behaviors in a Stochastic One-Dimensional Sand-Pile Model

A one-dimensional sand-pile model (Manna model), which has a stochastic redistribution process, is studied both in discrete and continuous manners. The system evolves into a critical state after a transient period. A detailed analysis of the probability distribution of the avalanche size and duration is numerically investigated. Interestingly,contrary to the deterministic one-dimensional sand-pile model, where multifractal analysis works well, the analysis based on simple finite-size scaling is suited to fitting the data on the distribution of the avalanche size and duration. The exponents characterizing these probability distributions are measured. Scaling relations of these scaling exponents and their universality class are discussed.

A DISCUSSION ON FRESNEL APPROXIMATION IN PHASE SCREEN MODEL

The Fresnel approximation in phase screen model is discussed and the coherencefunction is derived for k】】k.The application condition for Rino’s results is obtained,and it is|▽R△Ne|/R△ne【【1.

Nonlinear Mixed-Effects Models for Repairable Systems Reliability

Mixed-effects models,also called random-effects models,are a regression type of analysis which enables the analyst to not only describe the trend over time within each subject,but also to describe the variation among different subjects.Nonlinear mixed-effects models provide a powerful and flexible tool for handling the unbalanced count data.In this paper,nonlinear mixed-effects models are used to analyze the failure data from a repairable system with multiple copies.By using this type of models,statistical inferences about the population and all copies can be made when accounting for copy-to-copy variance.Results of fitting nonlinear mixed-effects models to nine failure-data sets show that the nonlinear mixed-effects models provide a useful tool for analyzing the failure data from multi-copy repairable systems.

Nonlinear Dynamical Behavior in BS Evolution Model Based on Small-World Network Added with Nonlinear Preference

We introduce a modified small-world network adding new links with nonlinearly preferential connectioninstead of adding randomly,then we apply Bak-Sneppen(BS)evolution model on this network.We study severalimportant structural properties of our network such as the distribution of link-degree,the maximum link-degree,and thegth of the shortest path.We further argue several dynamical characteristics of the model such as the important criticalvalue f_c,the f_0 avalanche,and the mutating condition,and find that those characteristics show panticular behaviors.

填土应力路径下珊瑚砂幂律应力-应变模型的适用性研究

岛礁工程建设常用珊瑚砂吹填地基或作为土工构筑物的填料。珊瑚砂在填筑期的应力路径具有静止土压力系数K_(0)固结和等应力比路径的特点,为了准确预估填筑期的填土变形量,需要建立能够反映填土应力路径影响的变形计算模型。根据广义虎克定律,建立了幂律形式的非线性弹性模型来描述土体的应力-应变关系,提出了变形参数的表达式。对珊瑚砂开展了K_(0)固结试验和等应力比路径下的排水三轴压缩试验,分析了珊瑚砂的应力-应变曲线和颗粒破碎状况,研究了幂律应力-应变模型的适用性,并将模型计算结果与试验曲线进行了对比。结果表明:填土路径下的应力-应变曲线具有幂函数曲线形式,可以用幂律非线性弹性模型来描述。模型的切线模量和切线泊松比均可以表示为轴向有效应力的函数,并通过与主应力比或系数K_(0)相关的参数得到表达。等应力比路径下的切线泊松比和切线模量随着轴向有效应力的增加而增大。在相同的轴向有效应力条件下,主应力比越大,切线模量越大,切线泊松比越小。随着轴向有效应力的增加,K_(0)固结珊瑚砂的静止土压力系数和切线泊松比减小,切线模量增大。在试验应力范围内,填土路径下珊瑚砂的颗粒破碎量都很小,对应力-应变特性的影响不大。幂律模型合理地预测了一定主应力比值范围内等应力比路径下珊瑚砂的应力-应变曲线,并能够考虑应力路径对应力-应变关系的影响。

Criticality in Two-Variable Earthquake Model on a Random Graph

A two-variable earthquake model on a quenched random graph is established here.It can be seen as a generalization of the OFC models.We numerically study the critical behavior of the model when the system is nonconservative:the result indicates that the model exhibits self-organized criticality deep within the nonconservative regime.The probability distribution for avalanche size obeys finite size scaling.We compare our model with the model introduced by Stefano Lise and Maya Paczuski [Phys.Rev.Lett.88 (2002) 228301],it is proved that they are not in the same universality class.

A Lecture of the Taylor Rule from the Sandpile Model

Sandpile phenomena in dynamic systems in the vicinity of criticality always appeal to a sudden break of stability with avalanches of different sizes due to minor perturbations. We can view the intervention of the Central Banks on the rate of interest as a perturbation of the economic system. It is an induced perturbation to a system that fare in vicinity of criticality according to the conditions of stability embedded in the equations of the neoclassical model. An alternative reading of the Taylor Rule is proposed in combination with the Sandpile paradigm to give an account of the economic crisis as an event like an avalanche, that can be triggered by a perturbation, as is the intervention of the Central Bank on the interest rate.

7050铝合金蠕变本构模型及其泛化能力研究

目的研究7050铝合金在温度为121~163℃、外加载荷为170~250 MPa条件下的蠕变拉伸行为。建立7050铝合金蠕变本构模型,对比本构模型精度并研究其泛化能力。方法采用CTM504-A1高温蠕变持久试验机进行蠕变拉伸实验,基于蠕变曲线及数据处理,分析蠕变温度和外加载荷对蠕变拉伸行为的影响,采用人工神经网络模型和幂律方程构建7050铝合金蠕变本构模型。结果7050铝合金在温度为121~163℃、外加载荷为170~250 MPa时,蠕变速率为4.44×10^(-8)~1.09×10^(-5) s^(−1),蠕变应变和稳态蠕变速率随着温度的升高而增大,在温度为163℃、外加载荷为250 MPa以及温度为177℃、外加载荷为170~250 MPa条件下,出现了蠕变第3阶段的加速蠕变,依据幂律方程构建的本构模型预测值的平均相对误差为2.45%,相关系数为99.02%;人工神经网络本构模型的预测值的平均相对误差为0.96%,相关系数为99.98%。结论在温度为121~149℃、外加载荷为170~250 MPa时,合金具有良好的低温抗蠕变性能。通过验证分析,与幂律方程模型相比,人工神经网络模型的预测精度更高;人工神经网络模型具有较强的泛化能力,在蠕变参数外仍具有很高的预测精度。