基于干扰观测器的多光伏光柴混合系统协调控制研究

提出了一种基于干扰观测器的多光伏光柴混合系统协调控制方法,并与采用最大功率跟踪控制而不加协调的多光伏系统的供电效果进行了对比.仿真结果证明,该方法减小了光柴混合系统的频率偏差,并且使各个光伏系统获得了较大功率输出.     

永磁同步风力发电系统的分数阶比例积分控制算法研究

将分数阶比例积分(PIλ)控制器应用于直驱型永磁同步风力发电系统,来达到实现系统高性能控制的目的。重点研究了永磁同步风力发电系统的分数阶PIλ控制器参数设计方法。通过分数阶PIλ控制器系统的仿真研究与试验分析,结果表明:采用分数阶PIλ控制器的系统具有较快的响应速度和较高的功率输出性能,具有一定的发展潜力和实用价值。     

Optimal maintenance policies for several imperfect repair models

Three new maintenance models, two imperfect preventive maintenance models and a cost limit (imperfect) repair model are proposed. In these models the imperfect maintenance is treated in such a way that after maintenance the lifetime of a unit will be decreased to a fraction of the one immediately preceding it, and the imperfect repair time as well as cost increases as the number of imperfect repairs increases. The long-run expected maintenance cost rates and corresponding asymptotic average availabilities for these three models are derived. The optimum maintenance policies subject to maintenance time are discussed. Some constraint optimization problems related to maintenance cost rate and availability are presented. Finally, numerical examples are given.     

基于安全衰减路径速度积的含表面裂纹缺陷压力容器安全裕度表征方法

针对压力容器表面裂纹安全衰减的时变问题,在表面裂纹安全衰减路径仿真基础上,提出基于路径速度积的裂纹缺陷安全裕度的表征方法,依据疲劳裂纹的扩展速率规律建立了压力容器表面缺陷的剩余寿命算法模型。仿真试验表明:新的方法可以定量精确地表征缺陷的动态安全裕度,并可利用由有限元J积分法求得的裂纹尖端应力强度因子与Paris公式分段迭代求解缺陷的剩余寿命。     

A Study of the Denaturation of Egg White Proteins during Freezing Using Differential Scanning Calorimetry

Differential Scanning Calorimetry was used to determine the effect of freezing rate, thawing conditions, storage time, and storage temperature on the enthalpy of denaturation of frozen egg white. Viscosity, foam specific gravity and foam instability of the product were also determined. Loss of enthalpy of denaturation was increased by slower freezing rates, higher thawing temperatures, higher storage temperatures, and longer storage times. Conalbumin suffered greater losses, and ovalbumin smaller losses, than egg white itself. Changes in egg white viscosity, foam specific gravity and foam instability varied depending on the processing variable tested and had no clear-cut relation with losses in enthalpy of denaturation.     

外界压力对粗糙表面摩擦与接触的影响研究

为研究外界压力对粗糙表面摩擦的影响,建立斜面滑块在不同真空度下的模型并进行试验测量在不同真空度下不同摩擦副配伍材料发生初始滑动时的斜面倾角。试验结果表明：随着外界压力增加,滑块发生初始滑动时的倾角增大,静摩擦力也增大。对于硬度小、重量轻以及接触面积大的摩擦副材料和零部件,其所受外界压力的影响更大。当外界压力从真空度-0.095 MPa增加到0 MPa,轴承钢/轴承钢的最大静摩擦力增大11%、轴承钢/聚碳酸酯增大12%,而聚碳酸酯/聚碳酸酯增大39%。由于通常情况下物体间的摩擦性能总是会受到外界压力的影响,因此真实摩擦角应在绝对真空环境下进行测量,而在大气中进行的测量都存在误差。同时可用文中方法测量两物体的实际接触面积。试验表明随着载荷增加实际接触面积增加,跟摩擦学的经验理论一致。     

Shearing interference microscope for step‐height measurements

A shearing interference microscope using a Savart prism as the shear plate is proposed for inspecting step‐heights. Where the light beam propagates through the Savart prism and microscopic system to illuminate the sample, it then turns back to re‐pass through the Savart prism and microscopic system to generate a shearing interference pattern on the camera. Two measurement modes, phase‐shifting and phase‐scanning, can be utilized to determine the depths of the step‐heights on the sample. The first mode, which employs a narrowband source, is based on the five‐step phase‐shifting algorithm and has a measurement range of a quarter‐wavelength. The second mode, which adopts a broadband source, is based on peak‐intensity identification technology and has a measurement range up to a few micrometres. This paper is to introduce the configuration and measurement theory of this microscope, perform a setup used to implement it, and present the experimental results from the uses of the setup. The results not only verify the validity but also confirm the high measurement repeatability of the proposed microscope.     

线性自抗扰控制在全桥DC–DC变换器中的应用

针对DC–DC变换器在实际应用中会受到多种输入扰动、负载扰动及电磁扰动影响的问题,本文结合全桥DC–DC变换器的系统模型特点,对传统线性自抗扰控制器进行了改进.设计了基于降阶扩张状态观测器和以比例控制作为误差反馈律的自抗扰控制器用于实际系统,在确保系统性能的前提下优化了参数整定过程.仿真和实验结果表明,该控制系统具有比传统PI控制系统更优的快速性、鲁棒性和适应性,且大大简化了传统自抗扰控制器设计过程中参数过多、取值困难的问题,具有良好的发展前景.     

Cr/nanodiamond composite plating with cobalt cation additive

The effect of cationic additive on Cr/nanodiamond plating was studied. Chromium plating was performed in Sargent bath. Morphology of deposit was observed by scanning electron microscope(SEM); microhardness by hardness tester; wear rate by tribometer; amount of diamond in deposit by combustion method and passivity by potentiodynamic scan. Experimental results show that in the presence of cobalt cation, the amount of nanodiamond particle in the deposit is increased. With increasing diamond particle amount, the metallurgical, mechanical and electrochemical properties of Cr/nanodiamond deposit are improved. However, this improvement seems to be constrained. In the presence of 10 g/L of nanodiamond powder and 2.5 g/L of cobalt cation in the bath, the amount of diamond particle in deposit is increased by 4 times; and wear rate of Cr-Co/nanodiamond deposit is decreased by 2–3 times as compared with pure Cr/deposit. The passive current of Cr-Co/nanodiamond composite deposit is decreased from 18 to 8 μA. The morphology of Cr/nanodiamond is smooth remarkably in the presence of cobalt cation.