气象卫星监测土壤含水量模型及其应用

估测大面积近地表土壤含水量对指导灌溉、防洪排涝、旱情预报等具有很大价值。本文首先从理论上分析了地表土壤日温差、热惯量和土壤含水量三者的关系,探讨了由地表土壤日温差推求热惯量、再由热惯量推求土壤含水量的方法,建立了由气象卫星监测土壤含水量模型,通过实测资料验证,表明该模型具有较高精度。其次,将所建立的模型应用于实际土壤含水量的监测,做出了土壤含水量分布图。     

气象卫星监测土壤含水量模型及其应用

估测大面积近地表土壤含水量对指导灌溉，防洪排涝。旱情预报等具有大价值。本文首先从理论上分析了地表土壤日温差，热惯量和土壤含水量三者的关系，探讨了由地表土壤日温差推求热惯量，再由热惯量推求土壤含水量的方法，建立了由气象卫监测土壤含水量的模型，通过实测资料验证，表明该模型具有较高精度，其次，将所建立的模型应用于实际土壤含水量的监测，做出了土壤含水量分布图。     

双惯量系统振动抑制算法研究

双惯量谐振系统易发生低频机械振动,针对此问题,设计了一种基于Luenberger状态观测器的双惯量谐振系统振动抑制算法。根据双惯量谐振系统模型构造了系统的状态方程,并对其进行了离散化处理,在验证系统满足能观性条件的基础上,建立了用于观测双惯量系统负载转速和转矩的状态观测器模型。将实际模型与估计模型输出间的误差反馈至估计模型进行修正,使得状态估计值逐渐逼近实际值,进一步进行状态反馈控制,有效抑制系统机械振动。实验结果验证了设计的双惯量系统振动抑制算法的有效性和可行性。     

时滞反馈非线性扭振系统的稳定性与Hopf分岔研究

研究了具有Duffing-Vanderpol组合振子和时滞特性两惯量非线性扭振系统的稳定性和Hopf分岔问题。建立了两惯量非线性扭振系统的动力学方程,通过设计线性位移和速度时滞反馈控制器构造了扭振受控系统。采用多尺度法推导出极限环幅值与时滞参数之间的关系。在对系统零解稳定性分析的基础上,得出Hopf分岔产生的条件。通过数值模拟的方法研究了扭振系统Hopf分岔和极限环幅值控制问题。仿真研究表明,所设计的时滞反馈控制器既能控制极限环的幅值,也能控制Hopf分岔的产生。     

基于PMU同步测量的分区惯量估计方法

随着电力系统中新能源接入量的不断增大,电网出现频率扰动的风险增加,评估系统的惯量水平已成为电力系统频率稳定的重要研究方向,同步相量测量单元(PMU)的大量装备,为利用扰动后数据评估系统惯量提供了可能。首先分析了系统惯性时间常数计算原理,考虑系统频率的传播特性,对系统进行分区处理,提出了一种基于PMU同步测量的分区惯量估计方法,利用扰动后各区域间联络线上传输功率和系统频率,采用一种差值法计算系统各区域惯量水平。所提方法对于故障区域与非故障区域的惯量具有统一的计算形式,且不需要识别故障功率的大小及发生区域,减小了测量及计算的复杂度。在EPRI-36节点系统中验证了所提方法的正确性,仿真算例表明,分区惯量估计方法能准确计算系统惯量,并计及了负荷等因素对惯量的影响。准确评估系统惯量,对于系统新能源接入、调频策略优化配置具有重要的指导作用。     

稀土永磁低惯量直流伺服电动机

在近代数字计算机外围设备中,广泛使用低惯量直流伺服电动机。这类电动机的典型用途是驱动数字磁带机的主动轮。本文集中地对稀土永磁低惯量直流伺服电动机中的两种基本磁结构、即切向和径向磁化磁铁的磁结构进行了比较。在电动机的设计阶段,采用了基于场模型和使用有限元法的计算机辅助设计方法。为了提高数值解的精度,提出了一种用于开放型磁结构并计及端部漏磁通的、改进的二维场模型。样机试验和计算结果表明提出的数值方法十分方便和有效,并表明采用本文所述方法后,能够得到尺寸大为缩小和性能显著提高的低惯量直流伺服电动机。     

PEEK及PES的低温热容的研究

用全自动绝热量热计从80K到380K测定了两种高分子材料PEEK及PES的低温热容,在实验温区这两种高分子材料均未观察到热异常现象．根据实验热容数据,用最小二乘拟合方法得到了计算这两种高分子材料80～380K热容值的多项式方程．     

高比例可再生能源接入下电力系统惯量研究综述及展望

在碳达峰和碳中和目标的推动下, 高比例可再生能源接入导致新型电力系统的低惯量特征突出。为保障电网安全稳定运行、支撑可再生能源消纳, 对电力系统惯量相关领域的研究进行综述与展望。阐述电力系统惯量的内涵, 探讨传统惯量、虚拟惯量和等效惯量间的关系, 剖析虚拟惯量控制的物理意义。从惯量来源的角度总结风机、光伏和储能等虚拟惯量控制技术的研究动态及成果, 并对电力系统惯量评估方法进行归纳梳理。总结电力系统惯量相关领域中亟待研究的重点内容并给出建议。     

热脉冲-时域反射技术原位测定土壤孔隙度及其影响因素分析

针对传统测量方法无法动态监测土壤孔隙度(n)的局限性,本研究基于热脉冲-时域反射(ThermoTDR)技术,利用改进后的Thermo-TDR探头在实验室内对不同质地土壤孔隙度和充气孔隙度(na)进行测定,并应用于野外原位动态监测土壤孔隙度,进而对热脉冲-时域反射技术测定土壤充气孔隙度的影响因素进行分析.实验表明,Thermo-TDR值与烘干法比较,室内测定均方根误差(RMSE)值为0.015,野外测定RMSE值为0.023,相对误差均在5%以内,可以准确反映土壤孔隙度的动态变化.探针间距r和热量q是影响热脉冲-时域反射技术测定土壤孔隙度的准确性的关键因素.减少探针入土时摆动导致的探针间距变化可以有效降低热脉冲-时域反射技术测定误差.Thermo-TDR技术测定迅速,准确性高且对土壤结构破坏小,具有广阔的应用前景和推广价值.     

PEK-C及PES-C的低温热容的研究

用全自动绝热量热计从80K到380K测定了两种高分子材料PEK－C及PES－C的低温热容,在实验温区这两种高分子材料均未观察到热异常现象．根据实验热容数据,用最小二乘拟合方法得到了计算这两种高分子材料80～380K热容值的多项式方程．     

A new measuring technique of soil thermal inertia

Thermal inertia is the function of substance density, heat capacity and heat diffusivity, and is an important parameter for researching the process of surface heat balance using remote sensing technique. In this paper, using soil heat plates, infrared thermometer, data logger and other instruments, by man-controlled changing the solar radiation status on the soil samples, the authors gave a new method to measure soil thermal inertia. Using the continuously surveying data of soil heat flux and infrared radiation temperature, thermal inertia can be calculated easily. Based on the thermal inertia calculation of three soil samples with different water content, good results were abtained by the authors, so this method is feasible. Meanwhile, this measuring technique is also a new attempt.     

A new measuring technique of soil thermal inertia

Thermal inertia is the function of substance density, heat capacity and heat diffusivity, and is an important parameter for researching the process of surface heat balance using remote sensing technique. In this paper, using soil heat plates, infrared thermometer, data logger and other instruments, by man-controlled changing the solar radiation status on the soil samples, the authors gave a new method to measure soil thermal inertia. Using the continuously surveying data of soil heat flux and infrared radiation temperature, thermal inertia can be calculated easily. Based on the thermal inertia calculation of three soil samples with different water content, good results were abtained by the authors, so this method is feasible. Meanwhile, this measuring technique is also a new attempt.     

粗放式屋顶绿化的热惰性

屋顶绿化的热工性能是进行建筑节能工程设计和评价的依据,但目前对屋顶绿化热工性能的研究很少关注热情性.以一种粗放式屋顶绿化在自然通风状态下连续5个月的对比测量数据为依据,采用统计分析方法研究了屋顶绿化对气候热作用波动的衰减和延迟特性.结果表明,绿化屋顶与裸屋顶相比,对气候热作用波动的平均衰减倍数提高了1倍以上,延迟时间有所减少.     

Longitudinal vibration of pile in layered soil based on Rayleigh-Love rod theory and fictitious soil-pile model

The dynamic response of pile in layered soil is theoretically investigated when considering the transverse inertia effect.Firstly, the fictitious soil-pile model is employed to simulate the dynamic interaction between the pile and the soil layers beneath pile toe. The dynamic interactions of adjacent soil layers along the vertical direction are simplified as distributed Voigt models.Meanwhile, the pile and fictitious soil-pile are assumed to be viscoelastic Rayleigh-Love rods, and both the radial and vertical displacement continuity conditions at the soil-pile interface are taken into consideration. On this basis, the analytical solution for dynamic response at the pile head is derived in the frequency domain and the corresponding quasi-analytical solution in the time domain is then obtained by means of the convolution theorem. Following this, the accuracy and parameter value of the hypothetical boundaries for soil-layer interfaces are discussed. Comparisons with published solution and measured data are carried out to verify the rationality of the present solution. Parametric analyses are further conducted by using the present solution to investigate the relationships between the transverse inertia effects and soil-pile parameters.     

一种较普遍的地表红外辐射模型

文中建立了一种适合于晴天或天空中有云复盖时光裸地面土壤热模型。利用能量守恒列出求解地表温度的热动平衡方程。其中各能量项采用较为普遍、精确度较高的实用表达式。为了验证,作者进行了有关物理量的实际测量。理论上求得的土壤表面温度与实测温度之差小于3度。     

Study on thermal wave based on the thermal mass theory

The conservation equations for heat conduction are established based on the concept of thermal mass. We obtain a general heat conduction law which takes into account the spatial and temporal inertia of thermal mass. The general law introduces a damped thermal wave equation. It reduces to the well-known CV model when the spatial inertia of heat flux and temperature and the temporal inertia of temperature are neglected, which indicates that the CV model only considers the temporal inertia of heat flux. Numerical simulations on the propagation and superposition of thermal waves show that for small thermal perturbation the CV model agrees with the thermal wave equation based on the thermal mass theory. For larger thermal perturbation, however, the physically impossible phenomenon predicted by CV model, i.e. the negative temperature induced by the thermal wave superposition, is eliminated by the general heat conduction law, which demonstrates that the present heat conduction law based on the thermal mass theory is more reasonable. Supported by the National Natural Science Foundation of China (Grant No. 50606018)     

Numerical and experimental evaluation on methods for parameter identification of thermal response tests

Several parameter identification methods of thermal response test were evaluated through numerical and experimental study. A three-dimensional finite-volume numerical model was established under the assumption that the soil thermal conductivity had been known in the simulation of thermal response test. The thermal response curve was firstly obtained through numerical calculation. Then, the accuracy of the numerical model was verified with measured data obtained through a thermal response test. Based on the numerical and experimental thermal response curves, the thermal conductivity of the soil was calculated by different parameter identification methods. The calculated results were compared with the assumed value and then the accuracy of these methods was evaluated. Furthermore, the effects of test time, variable data quality, borehole radius, initial ground temperature, and heat injection rate were analyzed. The results show that the method based on cylinder-source model has a low precision and the identified thermal conductivity decreases with an increase in borehole radius. For parameter estimation, the measuring accuracy of the initial temperature of the deep ground soil has greater effect on identified thermal conductivity.     

数据采集与解析计算相结合的温度快速测量

提出了能够实现温度快速测量的等间隔3点采集计算测量法,将数据采集与解析计算相结合,先等间隔采集3个时刻的传感器温度值,再经解析计算得到被测介质温度。该方法数据采集点数少,解析计算严谨简单,易于在以微处理器或信号处理器为核心的测试系统中实现,可以避免基于复杂原理和算法的其他测量方法存在的误差因素。该方法的测量速度取决于系统电性能,与传感器热惰性无关,适用于各种接触式温度传感器快速测量各种介质温度。     

土壤墒情监测系统在特色林果种植中的应用

引进土壤墒情自动监测系统,以枣树及葡萄为试种对象,采用烘干法测定值为标准,分析研究了土壤墒情监测系统监测的土壤含水率的准确性.试验结果表明,果树根区0~10 cm土壤含水率变化最为剧烈,10~20 cm土壤含水率变化相对平稳,20~40 cm土壤含水率最大且为试种果木根系主要的分布层,器测值与烘干法测定值变化趋势与幅度较为接近;器测数据相对烘干法测定值误差范围在-4.19%~9.26%,大部分误差值在1%~4%,误差较小;将烘干法测定值与同时、同地器测土壤含水率拟合,拟合方程为y=0.944 9x+0.410 7,拟合度达0.922 5,说明该型土壤墒情监测系统的传感器能够准确地测定土壤含水率.