Testing and explaining economic resilience with an application to Italian regions

This paper studies regional economic resilience by exploiting the properties of the non‐linear smooth‐transition autoregressive model. A testing procedure to distinguish between engineering and ecological resilience is presented, and a measurement of economic resilience is provided. Regional differences in economic resilience are explained by the presence of spatial interactions and by adopting a set of determinants like economic diversity, export performance, financial constraints, and human and social capital. An empirical investigation is conducted for analysing regional employment evolution in Italy from 1992 to 2012. Some concluding suggestions propose possible future areas of research.     

A Coupled Magnetic-Elastic-Thermal Free-Energy Model with Hysteretic Nonlinearity for Terfenol-D Rods

Based on the thermodynamic theory and the postulates of Jiles and Atherton, a general coupled magnetic-elastic-thermal free-energy model with hysteretic nonlinearity is established for Terfenol-D rods, in which the effect of Weiss molecular field is incorporated. The quantitative agreement between numerical simulation results predicted by the free-energy model and existing experimental data confirms the validity and reliability of the obtained nonlinear theoretical model, and indicates that the free-energy model can accurately capture the nonlinear hysteresis characteristic of Terfenol-D. Meanwhile, the free-energy model is employed to investigate the influences of mechanical stress and the temperature on the magnetostrictive effect of Terfenol-D in detail, and its predictions are coincident with some well-known experimental results including the temperature-dependent saturation nonlinearity and "overturn phenomenon". It indicates that the free-energy model can also effectively capture the nonlinear magnetic-elastic-thermal coupling characteristic of Terfenol-D. Some important physical parameters, such as the maximum magnetostrictive strain, the maximum piezomagnetic coefficient, are summarized, which can be used to optimize the performance of Terfenol-D in practical application. In addition, the free-energy model uses simple differential equation and algebraic equations, in which all of parameters have definite physical implications and can be easily determined by experiments. Thus, the free-energy model established in this article has very strong and wide practicability.     

变压器铁芯磁滞回线模型参数辨识

利用MATLAB遗传算法工具箱,由实验测得的磁滞回线,将模型参数分为2组,分别通过磁滞回线饱和特性和损耗特性的方法,对Jiles-Atherton（J-A）模型中的5个模型参数进行了辨识,并应用具体实例对该方法的有效性进行了仿真验证。仿真结果表明,所提方法能较好拟合磁滞回线。     

聚丙烯酰倍半硅氧烷(MPMS-SSO)有机/无机杂化气凝胶中的N_2等温吸脱附特性分析

采用自制的甲基丙烯酰多羟基倍半硅氧烷(MPMS-SSO)制备了UV固化的有机/无机杂化湿凝胶。N2等温吸脱附实验表明,气凝胶样品具有典型低压吸附滞后现象。将POSS分子中的笼形结构抽象为不同形状的极微孔模型,并对其进行了相关的数据计算,表明低压区吸附滞后现象可能与笼形结构对N2分子的强吸附有关。场发射扫描电子显微镜(FESEM)、高分辨透射电镜(HRTEM)分析表明构成气凝胶三维珍珠链结构的骨架的颗粒尺寸为20～30nm,骨架上具有约5～10nm的孔洞结构,珍珠链之间的孔洞结构尺寸约20nm,HRTEM表明气凝胶骨架的基本颗粒有机、无机组分分布均一,没有明显的相界面,初级颗粒约为几个纳米大小,由不同数目的倍半硅氧烷分子聚合而成。     

FeCoBSiNb非晶环的制备和磁性能研究

本文采用铜模吸铸工艺制备了外径5 mm、内径3 mm的Fe36Co36B19.2Si4.8Nb4非晶合金磁环,并采用X射线衍射（XRD）、示差扫描量热仪（DSC）、振动样品磁强计（VSM）和软磁交流性能测量仪分析了该非晶合金环的结构、热稳定性和磁性能。结果表明：该非晶合金的玻璃转变温度和晶化温度分别为568.5℃和604.4℃,饱和磁化强度为99.7 emu/g;在磁感应强度不变时,频率升高,其相对磁导率降低,磁损耗增大;保持频率不变,磁感应强度增大时,其相对磁导率降低,磁损耗增大。     

Positive and negative exchange bias in IrMn/NiFe bilayers

We present the observation of double shifted hysteresis loops in IrMn/NiFe bilayer structures. The bilayer structures were fabricated using high vacuum DC magnetron sputtering system. The hysteresis loops of the as deposited samples show the double shifted loops at NiFe layer thicknesses 5 nm and 6 nm, whereas the IrMn layer thickness was kept constant at 15 nm. The results were interpreted as the contribution of both positive and negative exchange bias fields. We suppose that this phenomenon is occurring due to the ferromagnetic (FM) layer exchange coupled with the antiferromagnetic (AFM) layer in two different magnetization directions. The ferromagnetic coupling of the interface spins in some regions of the film generates the hysteresis loop shift toward negative fields and antiferromagnetic coupling toward positive fields in the other regions. The double shifted hysteresis loops disappeared after magnetic field annealing of the samples above Neel temperature of the AFM layer. The X-ray diffraction patterns of the sample show the IrMn (111) crystalline growth necessary for the development of exchange bias field in this system. The correlation between the Magnetic Force Microscopy (MFM) domain structures of the as deposited sample and the magnetization reversal process of the double shifted hysteresis loops were discussed. The results suggest that the larger multidomain formation in the AFM layer with different magnetization directions was responsible for the positive and negative exchange bias fields in IrMn/NiFe bilayer samples.     

阻尼力双向调节磁流变阻尼器的性能测试与滞回模型

基于概念设计和理论分析,制作了4个阻尼力双向调节磁流变阻尼器的模型,并测试了模型阻尼器在不同输入电流状态下阻尼通道内的磁场分布以及力-位移和力-速度等性能曲线;通过对改进型Sigmoid模型的参数识别,建立了模型阻尼器的动力滞回模型。研究表明:模型阻尼器的磁路结构能够较好地实现阻尼力的双向调节,且阻尼通道内的磁场分布基本满足设计要求;模型阻尼器在零、最大正向和最大负向电流状态分别实现中等出力、最大出力和最小出力,且零电流状态的中等出力既能保证阻尼器的故障安全性能,又能防止磁流变液沉降;所建立的滞回模型简单、实用,且精度高。     

基于滞环控制的三相高功率因数整流器

目前大多数整流装置使用二极管或晶闸管整流,这些整流方式存在谐波污染大、功率因数低的问题。针对谐波问题提出了很多方法,如有源滤波、多重化技术,但这些方法没有从根本上解决谐波问题。三相高功率因数整流器不产生谐波,且可在高功率因数下运行,控制方法也较为灵活。在此介绍了该整流器主电路结构及其控制方法,详细分析了用滞环比较策略产生开关管控制信号的方法。用Matlab对该控制方法进行仿真,验证了方法的可行性。     

三元复合驱吸附滞留规律

针对大庆油田三元复合驱现场实施过程工艺参数难以确定的问题,基于北二区东部油层储层物性参数,通过填砂模型室内驱替实验,研究三元复合驱过程中各组分质量浓度、剪切降黏和界面张力变化规律,并通过数值模拟研究三元复合驱动态条件下各组分的吸附滞留规律.实验结果表明:三元复合驱的各类组分质量浓度均随运移距离的增加而降低,随注入量的增...     

统一电能质量调节器控制策略及仿真

通过对统一电能质量调节器(UPQC)电路拓扑的稳态功率进行详细分析,并与基于传统控制策略下UPOC所需容量进行一系列比较,提出一种基于串联侧无有功注入的新型控制策略.该控制策略根据相应的负载功率因数角、电压跌落程度决定串联侧补偿电压的幅值,在特定补偿电压注入角情况下,使得串联侧不消耗任何有功,同时能够减小并联侧无功补偿容量.该控制策略不仅能完成电网电压跌落补偿、谐波治理、负载无功补偿和输入功率因数校正,且在串联侧不消耗任何有功的情况下降低整个UPQC的补偿容量.为了克服滞环控制的不足,串联侧采用恒频滞环来保持开关频率的稳定.仿真结果验证了理论分析的正确性与可行性.