电力系统稳态数据参数化压缩算法

针对电力系统运行中产生的大量稳态数据,提出一种基于自适应神经模糊推理系统(adaptive-network-based fuzzy inference system,ANFIS)建模的参数化压缩算法。通过实现等相位采集方式,有效改善电网稳态数据的周期滑步现象,并建立和分析等相位数据的数学模型,为参数化压缩算法提供理论依据。设计参数化压缩算法的结构,并给出实现流程。该算法利用ANFIS系统建立基准序列模型,用于重构数据,采用三次样条插值建立基准相位模型,用于计算各周波相位差,由此将需存储的数据变为模型参数及相位差。最后利用仿真和实测数据详细分析影响系统信噪比和压缩比的因素,为参数的选取提供了参考,验证了算法不仅能提高稳态数据的压缩比,而且能有效滤除系统噪声,为电力系统海量数据的压缩提供了一种新思路。

谈电力系统稳态数据参数化压缩算法

电力系统日趋复杂多样化,为满足电能质量分析、故障监控以及广域测量等电网监控需求,针对电力系统运行中产生的大量稳态数据,提出一种基于自适应神经模糊推理系统建模的参数化压缩算法。通过实现等相位采集方式,有效改善电网稳态数据的周期滑步现象,并建立和分析等相位数据的数学模型,为参数化压缩算法提供理论依据。电力系统稳态数据同样蕴含着丰富的信息,其对分析电网运行状态、电网故障诊断和预测等有着重要意义。

广义参数化同步压缩变换及其在旋转机械振动信号中的应用

广义参数化时频分析通过构造匹配的参数化变换核,能够有效提高强调频信号的时频能量聚集性。然而,受短时傅里叶变换中窗函数结构的影响,利用该方法获得的时频能量分布在真实瞬时频率附近始终存在能量扩散现象。同步压缩变换利用同步压缩操作可将短时傅里叶变换处理后的时频能量压缩至真实瞬时频率位置,然而,同步压缩变换仅适用于分析频率成分恒定的纯谐波信号。以短时傅里叶变换为纽带,将两种时频分析方法相结合,提出了广义参数化同步压缩变换。考虑到旋转机械振动信号多为多分量信号,通过迭代处理的方式,依次获取各单分量信号的时频能量分布,对其进行叠加得到最终的时频能量分布。通过数值仿真以及变转速下转子不对中、滚动轴承外圈故障模拟试验验证了所提方法的有效性。

High temperature deformation behavior and optimization of hot compression process parameters in TC11 titanium alloy with coarse lamellar original microstructure

The high temperature deformation behaviors of α＋β type titanium alloy TC11 （Ti-6.5Al-3.5Mo-1.5Zr-0.3Si） with coarse lamellar starting microstructure were investigated based on the hot compression tests in the temperature range of 950-1100 ℃ and the strain rate range of 0.001-10 s-1. The processing maps at different strains were then constructed based on the dynamic materials model, and the hot compression process parameters and deformation mechanism were optimized and analyzed, respectively. The results show that the processing maps exhibit two domains with a high efficiency of power dissipation and a flow instability domain with a less efficiency of power dissipation. The types of domains were characterized by convergence and divergence of the efficiency of power dissipation, respectively. The convergent domain in a＋fl phase field is at the temperature of 950-990 ℃ and the strain rate of 0.001-0.01 s^-1, which correspond to a better hot compression process window of α＋β phase field. The peak of efficiency of power dissipation in α＋β phase field is at 950 ℃ and 0.001 s 1, which correspond to the best hot compression process parameters of α＋β phase field. The convergent domain in β phase field is at the temperature of 1020-1080 ℃ and the strain rate of 0.001-0.1 s^-l, which correspond to a better hot compression process window of β phase field. The peak of efficiency of power dissipation in ℃ phase field occurs at 1050 ℃ over the strain rates from 0.001 s^-1 to 0.01 s^-1, which correspond to the best hot compression process parameters of ,8 phase field. The divergence domain occurs at the strain rates above 0.5 s^-1 and in all the tested temperature range, which correspond to flow instability that is manifested as flow localization and indicated by the flow softening phenomenon in stress-- strain curves. The deformation mechanisms of the optimized hot compression process windows in a＋β and β phase fields are identified to be spheroidizing and dynamic recrystallizing controlled by self-diffusion mechanism, respectively. The microstructure observation of the deformed specimens in different domains matches very well with the optimized results.

Optimal choice of parameters for particle swarm optimization

The constriction factor method (CFM) is a new variation of the basic particle swarm optimization (PSO), which has relatively better convergent nature. The effects of the major parameters on CFM were systematically investigated based on some benchmark functions. The constriction factor, velocity constraint, and population size all have significant impact on the per- formance of CFM for PSO. The constriction factor and velocity constraint have optimal values in practical application, and im- proper choice of these factors will lead to bad results. Increasing population size can improve the solution quality, although the computing time will be longer. The characteristics of CFM parameters are described and guidelines for determining parameter values are given in this paper.

Simulation of dynamic recrystallization in 23Co13Ni11Cr3Mo steel using a modified cellular automaton

A modified cellular automaton(CA) program was developed to simulate the process of dynamic recrystallization(DRX) for 23Co13Ni11Cr3Mo ultrahigh strength steel.In this model,influences of deformation parameters on hardening rate and solute drag effect were considered.Moreover,an inverse analysis method was proposed for parameters identification of dislocation model and solute drag effect based on the results of isothermal compression tests on Gleeble-1500.Then,simulated microstructures under different deformation conditions were compared with those of experiments.A good agreement is achieved.Furthermore,influences of deformation parameters on microstructure evolution for 23Co13Ni11Cr3Mo steel were investigated in details.High strain is an effective measure to refine grain and improve homogeneity.Meanwhile,the desired deformation parameters are temperature of 1000-1050 °C and strain rate of 0.008-0.01 s-1 for obtaining grains smaller than 22.5 μm.

Aerodynamic Sweeping Study and Design for Transonic Compressor Rotor blades

The objective of the present paper is to study the sweep effect on the blade design performance of a transonic compressor rotor.The baseline to be modified and swept is a designed well efficient transonic single rotor compressor. The first part of the present study is concerning the sweep effect with straight leading edge.In this case fixing the hub section the swept blade is formed by tilting the leading edge with whole blade forwards and backwards axially.The second part is to use an optimization strategy with simple gradient-based optimum-searching method and multi-section blade parameterization technique to search and generate an optimal swept rotor with curved arbitrary leading edge.Its adiabatic efficiency is a little bit greater than that of the reference un-swept rotor.