Reversible Flat to Rippling Phase Transition in Fe Containing Layered Battery Electrode Materials

Layered sodium transition metal oxides of NaTMO₂ (TM = 3d transition metal) show unique capability to mix different compositions of Fe to the TM layer, a phenomenon that does not exist in LiTMO₂. Here, a novel spontaneous TM layer rippling in the sodium ion battery cathode materials is reported, revealed by in situ X‐ray diffraction, Cs‐corrected scanning transmission electron microscopy, and density functional theory simulation, where the softening and distortion of FeO₆ octahedra collectively drives the flat TM planes into rippled ones with inhomogeneous interlayer distance at high voltage. In such a rippling phase, charge and discharge of Na ions take different evolution pathways, resulting in an unusual hysteresis voltage loop. Importantly, upon discharge beyond a certain Na composition, the rippling TM layer will go back to flat, giving the reversibility of such structural evolution in the following cycles.     

Seismic response prediction of base-isolated structures with high damping rubber bearings

To characterize the highly nonlinear hysteretic behavior of high damping rubber (HDR) bearings, a previously developed mathematical hysteresis model, rather than a simplified bilinear hysteresis model, is adopted in this study. Unilateral and bilateral seismic simulation tests of a scaled-down multistory structure isolated with HDR bearings subjected to three recorded earthquakes were conducted. Based on the unilateral test results, different sets of model parameters can be identified. The fidelity of the adopted hysteresis model is investigated by comparing the analytical predictions using all sets of identified parameters with results measured from the tests. The significant influence ascribed to different ground motion characteristics such as the effects of near-field and far-field earthquakes on modeling the hysteretic behavior of HDR bearings is observed. Besides, a feasibility study on applying the identified parameters of the adopted hysteresis model to predict the bilateral seismic responses is performed. Even though the prediction accuracy of the seismic responses is satisfactory in two orthogonally horizontal directions, the bilateral hysteretic modeling of HDR bearings requires further intensive studies considering the coupling effect under bilateral excitations.     

Influence of iron on phase and magnetic property of the LaFe_（11.6）Si_（1.4） compound

The phase relation, microstructure, Curie temperatures, hysteresis, and magnetocaloric effects of LaFex*11.6Si1.4 (x=0.96, 0.98, 1.0, and 1.02) compounds prepared by arc-melting and then annealed at 1423 K (1.5 h)+1523 K (4.5 h) were investigated. The main phase was NaZn13-type phase, the impurity phases included a small amount of α-Fe and LaFeSi phase in four samples. The crystal cell parameters of 1:13 phase increased from 1.1433(5) to 1.1454(4) nm with x increasing from 0.96 to 1.02, respectively. All samples kept the typical first-order magnetic transition. The increase of Fe strengthened IEM behavior, and led to the remarkable enhancement of MCE effect and negative slopes in Arrott plots around TC. The maximum ΔSM (T, H) under a low magnetic field (0-2 T) was 15.3, 16.8, 17.9, and 24.7 J/kg K with increasing of Fe content from x=0.96 to 1.02, respectively.     

三态DPM电流滞环控制零电压开关逆变器的分析与设计

文中分析了三态DPM电流滞环控制技术在逆变器中的应用。基于高频脉冲直流环节单向电压源逆变技术设计了三态电流滞环控制零电压开关逆变器,克服了依靠谐振电路实现软开关所带来的结构复杂和控制难度大的缺陷,在工程应用中效果良好。     

A New Prototype Two‐Phase (TiNi)–(β‐W) SMA System with Tailorable Thermal Hysteresis

The Ti–Ni–W two‐phase shape memory alloy (SMA) thin film system is presented as a prototype for new SMAs with tailorable thermal transformation hysteresis (ΔT). The concept is to combine the SMA TiNi with almost insoluble W to create the two‐phase system (TiNi)–(β‐W). This system behaves like a pseudobinary TiNi system. Phase transformation behavior for compositions above the solubility limit of W in TiNi exhibit a B2–R phase transformation with characteristically small ΔT. Moreover, ΔT is dependent on the amount of W and it can be tailored to zero and even negative. This phenomenon is rationalized as being due to the mechanical interaction between the phases B2‐TiNi and β‐W. The presented results are very promising for the development of high‐speed Ti–Ni‐based SMA actuators.     

5kW光伏并网发电系统及其仿真研究

随着新能源发电的迅速发展,越来越多的可再生能源被转化为电能并通过并网逆变器输送到电网。利用MATLAB仿真工具箱建立了由光伏阵列输出、Boost升压电路、逆变器、控制器、电网等组成的5 kW光伏并网发电系统的仿真模型,研究了光伏并网系统的特性。采用变结构模糊PID控制器实现5 kW光伏发电系统的MPPT;采样电网电压作为逆变器电流的参考信号,利用滞环比较法控制逆变器,实现系统输出电流与电网电压同频同相,功率因素近似为1。仿真结果表明,系统较好地实现了光伏发电系统的MPPT及安全并网,对实际光伏并网系统的设计有参考意义。     

Fatigue,Magnetic and Mechanical Hysteresis

Abstract: The objective of this research is to explore correlations between piezomagnetic signals of initially unmagnetised ferromagnetic steel samples of AISI 1018 steel with progressive changes that take place during the fatigue process. A series of strain‐controlled fatigue tests were carried out to quantitatively study the piezomagnetic fields surrounding steel specimens by measuring magnetic field variations in the milligauss range resulting from the cyclic application of stress. It was observed that the piezomagnetic hysteresis traces change systematically with the progression of fatigue. The piezomagnetic hysteresis loop areas, when plotted as a function of the number of loading cycles, demonstrate the three principal stages of fatigue: initial accommodation, accretion of damage and terminal failure. The results derived from the piezomagnetic hysteresis traces are consistent with those obtained from mechanical hysteresis studies. However, when approaching failure, the piezomagnetic traces show more conspicuous changes than the corresponding mechanical stress–strain curves. It was also observed that the piezomagnetic field surrounding a specimen subjected to cyclic loading behaves approximately like that of a bar magnet. This study has demonstrated that the piezomagnetic effects can be exploited to evaluate the progress of fatigue in ferromagnetic steels.     

聚合物材料转矩流变仪转矩测量系统的研究

通过虚拟样机仿真对新型用于转矩流变仪的转矩测量系统进行了精度及可靠性分析。仿真表明,随着回差的增大,系统的误差也显著增大,因此在设计转矩流变仪时,对减速器的选择提出了一定的精度的要求。在仿真基础上研制了转矩测量系统部件。试验表明这种测量系统消除了机械系统所造成的回滞误差,使研制的转矩测量系统具有优于0．1％的测量精度。     

并联复合隔震体系非线性性能的试验研究

对一并联复合隔震结构模型进行了振动台试验研究,通过逐渐增加摩擦滑板的数量来调整隔震层摩擦承压比的大小。分析了复合隔震体系不同摩擦承压比对隔震层滞回特性、基底剪力系数以及复合隔震体系非线性性能的影响。试验结果表明:复合隔震结构的非线性特性与摩擦承压比的大小及地震烈度大小有关,在合理的摩擦承压比取值范围内复合隔震结构具有良好的隔震性能。     

宽电压输入范围的自动垂直钻井系统电源模块设计

针对石油行业井下自动垂直钻井系统三相钻杆式发电机电压输出范围较大的问题,给出了一种优化垂钻系统电源模块的设计方法,使电源模块既能适应较宽的电压输入范围,又能基本满足井下高温环境工作要求。