气动肌肉肘关节MPI迟滞模型与补偿控制

针对气动肌肉驱动的四连杆肘关节输入气压与输出角度间的迟滞进行分析。建立肘关节迟滞的PrandtlIshlinskii(PI)模型,采用Levenberg-Marquardt方法辨识模型参数;选择改进Play算子合适的包络函数,设计一种可描述非对称迟滞现象的改进PI(Modified PI,MPI)模型,相较于传统PI模型(Classical PI,CPI),MPI模型对非对称迟滞曲线拟合度更高。基于MPI模型,设计前馈积分逆补偿器,并与PID组成积分逆补偿控制器(MPI-I-I-PID);完成了MPI-I-I-PID、PID与基于CPI模型的积分逆补偿PID控制器(CPI-I-I-PID)的位置控制仿真。仿真结果表明,MPI-I-I-PID可以减小跟踪误差,提高跟踪精度。在不同负载下进行了控制实验,实验结果表明,随着负载增加,补偿效果减弱,为此在补偿器中加入分段PID,MPI-I-I-pPID可减小抖动幅度,降低肘关节跟踪误差,提高位置控制精度和稳定性,验证了迟滞补偿器的有效性。     

直接进给机构摩擦力特性研究

以直线电机驱动的直接进给机构为研究对象,进行直接进给机构摩擦力特性分析。搭建了直接进给机构摩擦力测试实验平台,采用激光干涉仪和高频电流传感器等设备进行位移和电流数据收集,进行数据处理;得到摩擦力与位移、摩擦力与速度的关系,建立摩擦力特性模型。结果表明,预滑动阶段,摩擦力存在明显的迟滞现象,且摩擦力随进给速度的增加呈线性增长,增长过程中摩擦力表现为粘滞摩擦。为直线进给机构摩擦情况的研究提供了支持和参考。     

Soil physical characteristics of peat soils

Drainage and intensive use of fens lead to alterations in the physical characteristics of peat soils. This was demonstrated using parameters of water balance (available water capacity) and the evaluated unsaturated hydraulic conductivity. Deriving the distribution of the pore size from the water retention curve was flawed because of shrinkage due to drainage, especially at high soil water potentials. These errors became greater as the peat was less influenced by soil‐genetic processes. The water retention curves (desorption) evaluated in the field and the laboratory satisfactorily corresponded. However, the wetting‐ and drainage‐curves obtained in the field differed up to 30 vol.‐% water content at same soil water potentials. These differences were largely due to a wetting inhibition.     

基于滞后效应函数的土石坝渗流水位模型应用

根据长期观测资料用数理统计回归分析建立土石坝渗流效应量模型,是目前普遍采用的大坝安全监测资料分析方法。传统土石坝渗流效应量模型主要受库水位、降雨和时间3个因素直接影响,并考虑前期平均库水位和降雨的影响。然而采用前期平均法并不能真实有效的反映库水位和降雨对大坝渗流的滞后影响,近年来提出了考虑库水位、降雨动态效应权重的滞后效应函数法,可以更好的描述变化库水位及降雨作用下的大坝渗流场。以此为基础,建立较为合理的大坝渗流模型,对某水库的渗流水位进行了多元非线性回归分析,采用遗传算法及最小二乘原理优化求得滞后参数及各分量系数,并进一步分析了库水位滞后参数演变规律。基于滞后效应函数的渗流水位模型拟合效果好,很接近实际情况,有利于对大坝的运行工况做出准确、合理的判断。     

1960-2013年广东省梅江流域径流特征及其对降水的滞后效应

[目的]全面了解梅江流域的水文特征及其变化趋势,为河流水量调节、防洪防汛及流域生态环境保护等方面提供决策依据。[方法]以该地区的典型河流梅江为例,利用1960—2013年流域的径流、降水数据,结合累积距平、变异系数、集中度和集中期等数理方法,对梅江的径流量、降水量在年代、年际、季节等时间尺度上进行分析,并用集中期来反映径流对降水变化的滞后效应。[结果]梅江径流量年际变化整体呈下降趋势,递减率为5．79 mm／10 a ;流域径流主要集中在4—9月,季节上主要集中在夏季和春季,径流集中期主要集中在5月下旬至7月中旬;流域内多年降水量呈波动减少趋势,但减少幅度很小,降水集中期主要集中在5—6月;流域内年径流量与降水量存在极大的相关性,并呈线性回归关系（r ＝0．824＞0．428＝ R0．001,54,回归显著水平超过0．001）,流域径流对降水具有滞后效应,多年平均滞后时间为21 d ,且滞后天数随着时间推移呈扩大趋势。[结论]可以推测是人类活动改变了地表覆被状况或者是气候的变化。     

木材吸湿机理及其应用

木材是一种多孔性、吸湿性和各向异性的天然高分子材料,水分影响着木材多方面的性质。文中从木材组分的角度综述了木材对水分的吸湿机理,介绍了木材对水分吸附的基本理论,解释了木材吸湿滞后现象的基本原因;在上述基础上评述了降低木材吸湿性的基本方法及其实现原因,还分析了机理应用方面存在的不足以及测试方法的不统一,并对未来研究趋势进行了展望。     

绒山羊次级毛囊基因表达滞后性的转录组分析

毛囊是具有高度的自我更新能力、独特的可再生器官,其周期性变化是一个动态过程,为了研究毛囊差异基因表达变化情况,文章以内蒙古绒山羊生长期毛囊为研究对象,利用Illumina高通量测序技术方法,检测6~10月皮肤毛囊差异基因表达变化情况,寻找对绒毛生长及质量具有调控作用的特异表达基因。试验发现,多数差异基因分别在初级毛囊（PF）的7、8月份和次级毛囊的（SF）8、9月份表达;在绒毛生长期的相邻月份中,发现FAM83C、LOC102185501、FYCO1、CTTNBP2NL、C6orf132、KRTAP29-1 和 CRYBG3 7个共同差异表达基因呈现相同的表达趋势,且在次级毛囊上的表达变化均比初级毛囊滞后1个月。综上所述,次级毛囊在基因表达调控中存在一定的滞后性,这将为绒毛周期生长发育和分子育种提供重要的理论基础。     

基于微观球体颗粒模型的土水特征曲线研究

When variations occur in the water content or dry bulk density of soil,the contact angle hysteresis will affect the soil-water characteristic curve(SWCC).The occurrence of the contact angle hysteresis can be divided into slipping and pinning.It is difficult to determine the effect of pinning existence on SWCC by tests.In this study,the effect of contact angle hysteresis on SWCC was analyzed either in the case of no variations in soil dry bulk density with changes in soil water content or no variations in soil water content with changes in soil dry bulk density.In both cases,soil particles were simplified to the spherical particle model.Based on the geometrically mechanic relationship between the particles and connecting liquid bridges,a physical model for predicting the SWCC was derived from the spherical particle model.Adjusting parameters made the model applicable to various soils,that is,the cohesive soil was considered as micron-sized spherical particles.Through the simulations on SWCC test data of sand,silt,clay,and swelling soil,it was confirmed that the physical model possessed good reliability and practicability.Finally,the analysis of rationality of contact angle was performed based on the basic assumptions of the model.     

并联混合型有源电力滤波器的设计与应用研究

分析并联混合型有源电力滤波系统的基本组成及工作原理,阐述对谐波检测及其产生补偿电流的控制方法,利用MATLAB软件建立仿真模型。试验结果表明,该设计对负载谐波源有良好的抑制作用。     

源于松针的可溶性有机物对土壤多环芳烃吸附和解吸行为的影响研究

Study of the relationship between plant litter-derived dissolved organic matter（DOM） and organic pollutant transport in soil is important for understanding the role of forest litter carbon cycling in influencing pollutant behaviour and fate in forest soil.With the aim of providing insight into the capacity of plant litter-derived DOM to influence sorption and desorption of selected polycyclic aromatic hydrocarbons（PAHs） on soil, batch experiments were carried out with application of a sorption-desorption model incorporating DOM effects. Freshly fallen pine（Pinus elliottii） needles were used as the source of organic matter. Input of the pine needle litter-derived DOM was found to significantly decrease desorption hysteresis as well as soil adsorption capacity of phenanthrene（PHE） and fluoranthene（FLA）. Addition of 1 728 mg L-1dissolved organic carbon（DOC） lowered the organic carbon-normalized sorption distribution coefficient of PHE from 7 776 to 2 541 L kg-1C and of FLA from 11 503 to 4 368 L kg-1C. Decreases of the apparent sorption-desorption distribution coefficients of PHE and FLA with increased DOC concentration indicated that DOM favored desorption of PAHs from soil. Increases in the fraction of apparently dissolved PAHs were attributable to the dissolved PAH-DOM complexes, accounting for the dissolved proportions of 39% to 69% for PHE and 26% to 72% for FLA in the sorption and desorption processes as the concentration of the added DOM solution rose from 0 to 1 728 mg L-1. Our results suggest that pine needle litterderived DOM can have a substantial effect of inhibiting PAHs sorption and promoting PAHs desorption, thus leading to enhanced leaching in soil, which should be taken into account in risk assessment of PAHs accumulated in forest soil.