Optimization of cutting power and power efficiency during particleboard helical milling

With the aim of providing scientific guidance for the application of spiral cutters in particleboard machining, this work studied the influence of milling parameters on milling power and power efficiency during helical milling of particleboard. And the response surface methodology was applied to optimize the milling parameters to reduce machining energy consumption and improve energy efficiency. The factors of milling depth, spindle speed and helical angle were selected as input parameters, and the mathematical models between the input parameters and the response parameters were established. Then, the significant influence of each factor and the interaction of two factors were determined by variance analysis, and the change trend of milling power and power efficiency was studied by response surface methodology. Results showed that the milling depth had the greatest impact on milling power and power efficiency, followed by the spindle speed and helical angle. An increase in the milling depth and spindle speed resulted in an increase in milling power and power efficiency, while the increased helical angle resulted in a decrease in milling power and power efficiency. The optimized values of helical angle, spindle speed and milling depth were 54°, 5650 min⁻¹ and 1.3 mm, respectively.     

基于谐波平衡法的双稳态压电发电系统非线性振动特性研究

研究双稳态压电发电系统非线性振动特性。通过谐波平衡法计算获得系统幅频响应方程,分析不同非线性系数、阻抗参数与激励对系统幅值解影响,随激励频率、幅值的变化,双稳态压电发电系统幅值解存在跳跃、多解现象,调节非线性系数及阻抗参数可使不稳定区域范围最小;研究外加激励对功率影响,随非线性系数及阻抗参数的增加,输出功率先增加后减小,通过调节磁化强度与负载阻抗可使系统输出功率最大;通过实验所得频率电压响应曲线及电阻功率响应曲线,验证系统非线性分析结果。可为双稳态压电发电系统工程应用提供理论依据。     

Multi-objective optimal design and performance of magnetorheological damper

In order to solve the problems of high power consumption and low output damping force of magnetorheological dampers, the relationship model between the structural parameters and the optimization objectives of dampers is established with the low power consumption and lightweight of magnetorheological dampers. The key structural parameters of the magnetorheological damper are optimized by the multi-objective genetic algorithm, and the optimal solution is obtained, and the optimized magnetorheological damper is tested and studied. The rationality of the selected parameters is verified by experimental study. The results show that the power consumption of magnetorheological dampers is reduced by 43 % and the damping force is increased by 30 % after optimization. There is a balance relationship between the power consumption optimization and the damping force optimization of the damper. Therefore, when finding the optimal solution, we should consider the needs of the actual situation and select the most reasonable parameters.     

An algorithm for determining global parameters of minimum-phasesystems with fractional power spectra

A method to determine the singularities and the corresponding powers of minimum-phase system functions with fractional power spectra from experimental data is presented. The characteristic parameters of the dynamic system are computed from the measured frequency spectrum using the derivative method to obtain an initial estimate of the parameters followed by a least-square optimization technique for fine tuning. Mathematical formulations of the derivative and the optimization steps are discussed, and a comparison between the estimated and theoretical parameters is provided. The simulated and experimental data collected from a polarized metal electrode-electrolyte interface serve to test the performance of the algorithm. Although the algorithm is proposed to extract the global parameters of fractional power spectrum systems, it can also be used to obtain the characteristic parameters of systems with integer power factors     

On fatigue life under stationary Gaussian random loads

Load parameters for a stationary Gaussian random load are taken as the location, scale and shape parameters of its power spectrum. The centre frequency of a power spectrum is proposed as a measure of fatigue life. A fatigue life function, formulated in terms of the load parameters, is evaluated from the test results obtained by fatigue testing a structural steel under six different power spectral shapes. The concept of a shape operator is employed to correlate fatigue lives under different power spectral shapes.     

基于输入能量的地震动时程强度包络函数研究

结构随机振动分析和人工合成地震动记录均需要将反应谱转换为功率谱,地震动强度包络函数对转换结果有着重要影响。为合理地确定强度包络函数模型中各参数的取值,依据输入能量谱与傅里叶幅值谱的精确转换关系,建立了由非平稳地震动功率谱计算输入能量谱的方法,并分析了各参数取值对功率谱与能量谱的影响。以匹配设计谱的天然地震动记录样本的平均输入能量谱作为参考依据,通过与设计谱转换得到的输入能量谱进行对比分析,确定了各类场地设计谱转换为功率谱时,强度包络函数模型的各参数取值。通过人工合成地震动记录的输入能量谱分析,验证了各参数取值的合理性。     

基于STM32的频率和功率可调非接触供电超声电源设计

为解决接触式供电中漏电、磨损、电能传输不良以及超声电源在加工中谐振频率漂移、跟踪速度慢、输出功率不稳定等问题,文章以STM32单片机作为主控系统,设计了一种频率和功率可调的非接触供电超声电源。根据采样反馈电路采集的电压电流相位差和有效值信号,采用锁相环和模糊比例积分(Proportional Integral, PI)控制相结合的方法对频率进行跟踪,并用传统 PI 控制法控制输出功率。在 Matlab 软件中搭建电源仿真模型,利用附加电阻、附加电感和附加电容模拟加工过程中负载参数的突变,对有频率调节和功率控制子系统以及没有子系统的电源模型分别进行仿真。仿真结果表明,电源输出功率稳定在 248 W。当负载参数发生改变时,电源的谐振频率发生漂移,经过频率自动跟踪子系统的调节后,电源在 0.01 s 后重新回到谐振状态。此控制算法实现了频率快速跟踪和功率控制。     

TiO2膜层制备参数对Ag/TiO2复合膜隔热性能的影响

采用磁控溅射工艺制备玻璃基Ag/TiO_2复合膜,研究TiO_2膜的射频功率、溅射时间、氩气流量和本底真空度4个制备参数对复合膜隔热性能的影响。结果表明:复合膜的隔热温差随着射频功率、溅射时间、氩气流量、本底真空度的增加均呈现先增大后减少的变化趋势;4个制备参数对复合膜隔热温差的影响程度由大到小的顺序依次为本底真空度、溅射时间、射频功率、氩气流量;4个制备参数的较优组合为本底真空度4×10~(-3) Pa,射频功率150 W,溅射时间15 min,氩气流量20 m L/min。     

基于FFT的电力系统谐波检测仪研制

为了准确地测量和分析电力系统中的谐波参数,在分析了常用的几种谐波测量方法的基础上,提出了一种基于FFT数字倍频整周期采样的电力系统谐波参数的测量方法.研制了以高性能ARM Context-M3内核的STM32微处理器为核心的电力系统谐波检测仪.检测仪具有测量基波和各次谐波的电压、电流绝对值的功能,并且能够测得谐波含有率、功率因数、功率和基波频率等其他参数,实现了对电力系统谐波参数的实时监控.     

Analysis of optical switching in a Yb3+-doped fiber Bragg grating by using self-phase modulation and cross-phase modulation

The optical performances of the all-optical switching based on Yb3+-doped fiber Bragg grating (FBG) are investigated under the case of self-phase modulation (SPM) and cross-phase modulation (XPM). For the SPM case, the optical bistability of FBG under different parameters is investigated. It shows that the width of the hysteresis loop and threshold switching power are strongly dependent on the fiber grating length, fiber grating detuning, and coupling constant. For the XPM case, the expressions of the threshold switching power in the different detuning range are given. The influence of parameters about different detuning and coupling constant to the threshold switching power and extinction ratio are also studied. In comparison with the SPM case, the switching power of FBG under XPM case can be reduced to less than 20 mW by optimizing the parameters of FBG.     

Coordinated stability control

An adaptive coordination scheme is proposed to improve the transient stability, voltage security and frequency damping of a power system network by optimally scheduling the parameters of the available controllers. A set of real-time stability indicators, including a transient stability index, transient voltage stability index and damping factor are used to reflect the stabilities of power systems. Then, the relative significances of a group of controllers to the power system are used as references for the optimiser to schedule new controller parameters. This coordinated control scheme effectively allocates power system resources to handle different stability issues in different time frames. The results suggest that power system security can be further enhanced by means of coordinated control.     

The effect of physical vapor deposition parameters on the thermoelectric power of thin film molybdenum-nickel junctions

The effect of various physical vapor deposition parameters on the thermoelectric power of thin film (10 000 Å) Mo-Ni junctions deposited by electron beam evaporation was investigated in this study. The deposition parameters of interest were the substrate temperature, the deposition rate and the vapor source purity. The thermoelectric power of the thin film Mo-Ni junctions was dependent on the structure of the Mo thermoelectric element of the couple, the characteristics of which were significantly altered by varying the deposition parameters. Varying the deposition parameters caused a change in lattice imperfections in the metal, which changed the mean free path of the conduction electrons and the thermoelectric power of the couple. The parameters having the greatest effect on the thermoelectric power were the deposition rate and the substrate temperature. Couples deposited at a high deposition rate (10 000 Å min^-1) and a high substrate temperature (? 300 °C) demonstrated e.m.f. characteristics closest to bulk values.     

锅炉远程水吹灰器更换小口径喷嘴研究

大规模风电并网需要火电机组的灵活调节,在调节能力改造过程中应该保持锅炉的正常运行。为了减少远程水吹灰对锅炉炉膛热负荷的扰动,抑制锅炉本体膨胀,保证输出功率的灵活调节,对锅炉参数进行了研究。某电厂#1、#2锅炉远程水吹灰器流量较大、吹灰过程中对锅炉参数影响较大,通过更换小口径喷嘴,控制了水吹灰器对锅炉参数的扰动。根据试验前后参数对比分析远程水吹灰器更换小口径喷嘴对锅炉不同参数的影响,证明通过更换小口径喷嘴来改造是可行和安全的。     

Output microwave radiation power of low-voltage vircator with external inhomogeneous magnetic field

Dependence of the power of a broadband microwave radiation generated by a low-voltage oscillator with virtual cathode (vircator) on the parameters of an external inhomogeneous magnetic field has been studied by numerical simulations using a two-dimensional model. It is established that there are optimum parameters of the generator (configuration of the external magnetic field, electron beam current) for which the output radiation power is maximum. A relationship between the optimum conditions of virtual cathode formation in the electron beam and the microwave generation regime is established.     

一种水电厂房振动模态参数识别方法

水电厂房的振动是机械力、电磁力、水力脉动共同作用的结果,其动荷载很难测得,结构模态参数识别的难度不言自明。为解决以上困难,提高厂房结构振动模态参数识别的精度,在厂房结构各种荷载未知的情况下,将突然停机工况下动荷载释放后的振动信号,利用随机减量法提取自由衰减信号成分,以基于ARMA模型参数识别法实现了对某大型水电站厂房低阶模态参数的识别。识别结果表明,随机减量法和ARMA联合分析方法是解决大型复杂厂房结构动态参数识别的有效方法,识别结果可用于结构物的健康监测和振动控制中,同时该方法在大型水电站厂房振动模态参数的在线识别领域中具有广阔的工程应用前景。     

中高功率离子推力器的性能参数分析研究

此次系统调研在已有高功率离子推力器研制情况的基础上,对中高功率离子推力器的主要性能参数进行了分析研究,得到了离子推力器性能随功率变化的经验关系,并应用这些关系分析预测了中高功率离子推力器的性能极限,得出了基于现有技术的离子推力器难以满足未来高功率电推进使命需求的分析结论。     

峰值功率计校准方法的研究

为解决峰值功率计所特有的突发功率参数的校准问题,从在数字移动通信系统中广泛使用的突发信号的各项特殊功率参数以及峰值功率计的测量原理入手,以传统功率校准为基础,结合新参数特点对校准峰值功率计的原理和方法进行了研究,最后建立了校准系统,并给出了突发功率的测量不确定度分析,结果其扩展不确定度为0.17 dB,满足峰值功率计的校准要求。     

Transmitting electric energy through a metal wall by acoustic waves using piezoelectric transducers

The feasibility of transmitting electric energy through a metal wall by propagating acoustic waves using piezoelectric transducers is examined by studying the efficiency of power transmission and its dependence upon the relevant system parameters for a simplified system consisting of an elastic plate sandwiched by two piezoelectric layers. One of these layers models the driving transducer for generating acoustic wave, and the other layer models the receiving transducer for converting the acoustic energy into electric energy to power a load circuit. The output voltage, the output power, and the efficiency of this system are expressed as explicit functions of the system parameters. A numerical example is included to illustrate the dependence of the system performance upon the physical and geometrical parameters.     

工艺参数对冷坩埚连续铸造Ti6Al4V表面的影响

为消除冷坩埚连续成形钛合金铸棒表面缺陷，了解工艺参数对表面质量影响规律，并制备出无裂纹铸棒，通过正交试验和理论分析的方法，研究了不同工艺参数对表面质量的影响，研究表明：表面质量随功率和线圈匝数的增加而变坏，随抽拉速度和拉锭高度的增加先变好后变坏；各参数影响程度不同，线圈匝数影响最大，功率次之，抽拉速度再次，拉锭高度影响最小；铸造表面质量良好钛合金棒的工艺参数为：抽拉速度5mm／min，功率50kW，线圈3匝，拉锭高度30mm。     

基于希尔伯特变换的信号解调算法及其在飞机供电特性参数测试系统中的应用

电压调制幅度、频率调制幅度和畸变频谱是对飞机机载电源系统供电特性参数进行测试时与信号调制相关的重要参数。为了更好地测试这些参数,提出了一种基于希尔伯特变换原理的数字解调算法,可以将采集的幅度或频率调制信号进行解调分析;同时,构建了一套飞机供电特性参数测试系统,将解调程序与硬件设备结合,通过程序控制数据采集卡对机载电源信号采样与解调分析;设计了实验对波形发生器产生的调制信号进行采样与解调,验证了该系统具有良好的效果,可以应用于飞机供电特性参数的测试中。