Research on numerical simulation of the groundwater funnels restoration in Shijiazhuang

In order to simulate the recovery of groundwater funnels under the condition of reducing groundwater abstraction, hydrogeological conditions of recoverability construction of Shijiazhuang groundwater funnel were analyzed, and a numerical simulation method was used based on the change of various parameters. The results show that the groundwater flow model can accurately reflect groundwater hydrogeological characteristics, and can guarantee the reliability of groundwater restoration prediction. The research has set up four schemes for rural water-saving, planting structure adjustment, urban reducing abstraction and integrated method. The effect of four restoration schemes on the restoration of groundwater funnels was compared with water table variations of two observation well. Comparison results show that the level changes of plan Three and Four are different from the other two kinds of exploitation and the drop trend of water table in the funnel area is flat. So we can conclude that Plan Three and Four have significant effect on the groundwater funnel restoration of Shijiazhuang.

Study of wind towers with different funnels attached to in crease natural ventilation in an underground building

Finding ways to cool buildings by natural,passive techniques is crucial in the context of global warming.For centuries,wind towers(traditi onal win dcatchers)have been used in the Middle East for cooling purposes.In this study,the use of funnels at the openings of wind towers for wind ingress and egress is proposed primarily to increase the mass flow captured by the wind tower.The use of funnels in the wind in gress openings in creases the inlet area,improving the capture of wind.In parallel,the use of funnels in the egress openings modifies the wake of the tower,which aims to ease the exit of the flow from inside the building.Several design configurations are presented,where the length and width of the funnels are changed and tested separately by computational fluid dynamics(CFD).Results of over 120 CFD simulations are presented and compared.The volumetric flow entering the wind towers in creases by 10.7% in several cases.These results in dicate that adding funnels to wind towers could positively in fluence their performance.Changing the dimensions of the funnels affects their efficacy and can increase or decrease the airflow entering the tower.

PI磁滞非线性系统的动态伪逆补偿控制算法

通过设计磁滞动态伪逆补偿和新型动态面控制来消除非线性系统中未知饱和磁滞的影响。磁滞动态伪逆补偿通过构建辅助滤波器,提出了一种实时在线补偿磁滞的机制,且不需要构建显式磁滞逆和辨识相应的未知参数。此外,基于正时变积分函数设计了新型非线性滤波器,该滤波器不仅避免“微分爆炸”问题,降低计算负担,而且补偿动态面边界层误差,使系统的跟踪误差收敛到零。理论分析表明:该方案能有效地消除未知磁滞的影响,保证闭环系统的稳定。最后,通过仿真实例验证了该方案的有效性。

未知非线性多智能体系统的分布式有限时间自适应神经网络控制

针对一类具有未知磁滞输入的非线性多智能体系统,提出了一种基于改进命令滤波器的分布式预设性能自适应神经网络渐近一致控制方案。首先,为保证系统的跟踪性能,提出了基于新型性能函数的有限时间Funnel控制方案,使得跟随者与领导者在有限的时间内输出一致。其次,利用径向基神经网络和放缩方法消除了未知非线性的影响。然后,使用命令滤波器解决了传统递归方法的“微分爆炸”难题。理论分析表明:该控制方案消除了未知磁滞输入的影响并且实现了一致性误差渐近收敛至0。最后通过实例仿真验证了文中控制方案的有效性。

时变参数执行器故障系统的渐近跟踪控制算法

针对一类具有时变参数和未知执行器故障的不确定非线性系统,提出了一种基于命令滤波器的自适应预定性能渐近跟踪控制算法。首先,基于正时变积分函数设计未知时变参数和外部扰动的动态补偿量,消除其在控制器设计过程中的影响。其次,构造新型Funnel模型,不仅能够保证跟踪误差的瞬态性能,同时避免了控制器设计中的奇异性问题。最后,利用命令滤波器解决了传统自适应反推控制方法中存在的“微分爆炸”问题,降低计算负担;同时,设计的补偿信号消除了滤波器引起的误差。理论分析表明闭环系统所有信号一致最终有界,且系统跟踪误差渐近收敛到零。仿真实例验证了该控制方案的有效性。

基于AFF和SGA的科氏质量流量计信号处理方法

采用一种新的方法来处理科里奥利质量流量传感器的信号。该方法将自适应Funnel滤波器(AFF)和滑动Goertzel算法(SGA)结合起来,能够精确地跟踪信号的频率,计算相位差。与以往的方法相比,该方法跟踪精度高且跟踪速度快,具有用定点实现其算法时不容易产生溢出和适合于时变信号的优点。

基于改进Funnel控制的机械臂轨迹跟踪约束控制

针对关节柔性机械臂系统在未知输入饱和的情况下的稳态和瞬态性能约束问题,提出一种改进Funnel控制结合RBF自适应神经网络的轨迹跟踪控制方法。设计了改进的Funnel控制变量以避免控制律中的微分不可导的情况;构造了时变的瞬态性能约束函数,调节系统输出初始阶段的超调量和收敛速度;采用最小参数学习法的RBF自适应神经网络,逼近机械臂系统模型的未知函数和虚拟控制律的导数,简化了控制器的设计;通过李雅普诺夫稳定性定理,证明了闭环系统中所有变量是半全局一致最终有界的。仿真实验验证了所提方法有效性。

带有饱和的电机伺服系统非奇异终端滑模funnel控制（英文）

本文提出一种非奇异终端滑模funnel控制(NTSMFC)方法,实现带有饱和输入电机伺服系统的指定性能跟踪控制.根据中值定理,非光滑饱和函数转化为放射形式,并且应用一个简单的神经网络进行逼近和补偿.为保证跟踪误差被限制在指定的界限内,同时为避免构建复杂的barrier李雅普诺夫函数或逆函数,本文采用一个新的限制变量.然后,构建非奇异终端滑模funnel控制器保证电机伺服系统的指定跟踪性能.该方法无需事先已知输入饱和函数的界限等先验知识,且基于李雅普诺夫函数设计可以保证位置跟踪误差的收敛性,最后给出仿真对比实例证明了该方法的有效性.

基于未知系统动态估计器的柔性关节机械臂funnel控制

针对带有模型不确定和外部干扰的柔性关节机械臂,提出一种基于未知系统动态估计器的funnel控制方法。基于低通滤波器设计未知系统动态估计器,用于估计模型不确定和外部干扰,该估计器结构简单,仅有一个可调参数。构造带有时变约束边界的新型funnel变量,保证系统跟踪误差被限制在预先设定的边界内,进而改善系统瞬态性能。在此基础上,设计反演控制器,保证系统输出快速准确跟踪期望轨迹。为避免传统反演法中的“微分爆炸”问题,设计跟踪微分器逼近虚拟控制律导数。并给出数值仿真对比验证本文所提方法的有效性。

多电机驱动系统的保性能鲁棒Funnel控制

本文针对含参数不确定性的多电机驱动系统,提出一种基于最优保性能鲁棒的Funnel控制方法实现系统的规定跟踪性能.该控制方法通过构造Funnel函数对误差系统进行变换,并设计自适应反步控制器保证变换后系统的稳定性即可使跟踪误差的瞬态和稳态响应均被限制在给定的Funnel边界内.然而由于系统中存在的参数不确定性会影响系统的规定控制性能,本文在Funnel控制基础上又设计了最优保性能鲁棒控制器.它是通过将参数不确定性系统的保性能鲁棒控制问题转化为标称系统的最优控制问题,并求解新的黎卡提方程而得到的.因此所设计的控制器不但消除了参数不确定性对系统的影响并且能够使系统的性能指标达到一确定的上界.最后,对四电机驱动系统进行了仿真和实验验证,说明所提出控制方法的有效性.

基于DAF算法的地图寻径研究

融合了Delaunay Triangulation算法,A*算法以及Funnel算法的优点,提出了DAF算法,并将其应用于网络游戏的地图寻径中,解决了地图信息获取不便捷和搜索路径比较曲折的问题,得出一条最优路径。计算机仿真结果表明DAF算法提高了搜索效率和路径的平滑程度。

输入时滞非线性系统的新型动态面Funnel控制

本文针对一类带有输入时滞的不确定非线性系统,提出了新型动态面Funnel控制方案.首先设计补偿动态变量将输入时滞系统转换成无时滞的系统,仅需在递归控制的最后一步补偿,从而优化了控制器设计过程.其次,构造Funnel函数,使系统的瞬态和稳态跟踪误差被限制在给定边界内.最后,提出新型非线性动态面控制方法,不仅避免了自适应反推控制中的“微分爆炸”问题,而且消除了边界层误差,使得系统的跟踪误差最终渐近收敛到零.理论分析表明该闭环系统的所有信号一致最终有界,仿真结果验证了该控制方案的有效性.

Characteristics of Caragana korshinskii and Hippophae rhamnoides stemflow and their significance in soil moisture enhancement in Loess Plateau, China

Stemflow of xerophytic shrubs represents a significant component of water replenishment to the soil-root system and influences water utilization of plant roots at the stand scale,especially in water-scarce semi-arid ecosystems.The stemflow of two semi-arid shrubs(Caragana korshinskii and Hippophae rhamnoides)and its effect on soil moisture enhancement were evaluated during the growing season of 2011 in the semi-arid loess region of China.The results indicated that stemflow averaged 12.3%and 8.4%of the bulk precipitation for C.korshinskii and H.rhamnoides,respectively.Individual stemflow increased in a linear function with increasing rainfall depth.The relationship between funneling ratios and rainfall suggested that there existed a rainfall depth threshold of 11 mm for both C.korshinskii and H.rhamnoides.Averaged funneling ratios were 156.6±57.1 and49.5±30.8 for C.korshinskii and H.rhamnoides,respectively,indicating that the canopy architecture of the two shrubs was an effective funnel to channel stemflow to the root area,and C.korshinskii showed a greater potential to use stemflow water in the semi-arid conditions.For individual rainfall events,the wetting front depths were approximately 2 times deeper in the rooting zone around the stems than in the bare area outside canopy for both C.korshinskii and H.rhamnoides.Correspondingly,soil water content was also significantly higher in the root area around the shrub stem than in the area outside the shrub canopy.This confirms that shrub stemflow conserved in the deep soil layers may be an available moisture source for plant growth under semi-arid conditions.

Corrosion mechanism of magnesia-chromite refractories by ZnO-containing fayalite slags: Effect of funnel glass addition

An efficient approach for lead extraction from waste funnel glass through the lead smelting process has been proposed. To clarify the effect of funnel glass addition on the degradation of magnesia-chromite refractories by ZnO-containing fayalite slag, the corrosion behavior of magnesia-chromite refractories in lead smelting slags with different funnel glass additions from 0wt% to 40wt% was tested. Scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS) was used to acquire the microstructural information of the worn refractory samples. Experimental results showed that the corrosion of magnesia-chromite refractory consisted predominantly of the dissolution of MgO into slag. ZnO and FeO reacted with periclase and chromite to form (Zn,Fe,Mg)O solid solution and (Zn,Fe,Mg)(Fe,Al,Cr)2O4 spinel, respectively. With the addition of funnel glass, the solubility of MgO increased whereas ZnO levels remained stable, thereby resulting in a reduced Mg content and an elevated Zn and Fe content in the (Zn,Fe,Mg)O solid solution and the (Zn,Fe,Mg)(Fe,Al,Cr)2O4 spinel. Considering the stability of the (Zn,Fe,Mg)O solid solution layer and the penetration depth of the slag, the optimal funnel glass addition for lead smelting was found to be 20wt%.

Modelling stemflow production by juvenile lodgepole pine(Pinus contorta var.latifolia)trees

Stemflow is a focused point source input of precipitation and nutrients at the base of a tree or plant and can have a significant impact on site hydrology. To date, no known studies have modelled stemflow production for juvenile lodgepole pine （Pinus contorta vat. latifolia）. Meteorological conditions, tree characteristics, and stemflow were sampled for two juvenile lodgepole pine stands over the course of the 2009 growing season. Step-wise multiple regression was used to assess which meteorological and tree architecture variables influenced stemflow production for each research plot. Once predictor variables were identified, models were produced for each stand and a generic model was produced that applied to both plots. A model employing precipitation depth and crown projection area successfully explained 71.3% of the variation in stemflow production from sampled trees. Stemflow was found to represent 1.8% of the study period rainfall and, although not a large component of the plot-scale canopy water balance, it is an order of magnitude greater than the fractioning of stemflow from mature lodgepole and lodgepole pine dominated forest. Additionally, stemflow funnelling ratios were found to average 22.2 and 24.3 from the two sample plots over the study period with a single tree, single event maximum of 111.7 recorded for a tree with a 3.3 cm bole diameter and a rain depth of 17.4 mm.

INFLUENCES OF CASTING SPEED AND SEN DEPTH ON FLUID FLOW IN THE FUNNEL TYPE MOLD OF A THIN SLAB CASTER

In recent years, thin slab continuous casting technology has been widely used to improve the quality of the product and to reduce the cost. One of the challenges faced by this technology is to design reasonable flow patterns, which strongly affect the surface and inner properties of the final slab in the mold. With the fixed scales and complex geometrical structures of nozzle and funnel type mold, a series of numerical simulations are made to analyze the flow patterns in melt steel using finite volume method based on structured body fitted coordinate grids. The CFD （computational fluid dynamics） package is validated first using one typical case described in previously published studies, and then it is developed to study the effect of operational parameters on fluid flow in thin slab caster. Two operational parameters, casting speed and SEN （submerged entry nozzle） depth, are mainly considered for numerical analysis. On the basis of present simulations, the reasonable SEN submergence depths corresponding to different casting speeds are suggested according to fluid flow characteristics like, flow jet impingement on the narrow side of the mold, flow speed of the melt steel beneath the meniscus and the recirculation region. This is the first stage of study on the numerical analysis of the whole thin slab casting process with electromagnetic brake.

Rheological Properties of Cement-Based Grouts Determined by Different Techniques

The rheological properties of cement-based grouts containing talc or palygorskite were investigated for optimizing fluidity and quick strengthening at injection. The fluidity controls the ability of grout to penetrate fractures and can be determined by pipe flow tests, Marsh funnel tests, mini-slump cone tests and rheometer tests. The grouts were 1) Talc for fluidity and strength by reacting with cement, 2) Palygorskite (attapulgite) for early gelation by being thixotropic, and 3) Powdered quartz for chemical integrity. The freshly prepared grouts behaved as Bingham fluids with viscosities from 0.151 to 0.464 Pas and yield stresses 5.2 Pa to 36.7 Pa. Statistical analysis of the flow test data converted Marsh flow time into viscosity. The pipe flow tests gave 26.5% higher values than the viscometer for grout with Portland cement and talc, and about 13.7% lower than the viscometer data for the grout with low-pH cement and talc. The big Marsh funnel gave values differing by 5.2% - 5.3% from those of the viscometer for grout with talc and Portland, and Merit 5000 cements. For grout with palygorskite the viscosity was at least twice that of the other grouts. Grout fluidity was positively affected by talc and negatively by palygorskite and early cement hydration.

Controllable Magnetic Focusing of Cold Atoms on a Chip

We propose a new lens scheme to focus cold atoms by using a controllable inhomogeneous magnetic field from a square current-carrying wire fabricated on a chip. The spatial distributions of the magnetic field are calculated, and the results show that the generated magnetic field is a two-dimensional （2D） quadrupole one and can be used to focus cold atoms or a cold atomic beam. The dynamic processes of cold atoms passing through our square wire layout and its focusing properties are studied by using Monte Carlo simulations. Our study shows that the atomic clouds can be focused effectively by our magnetic lens scheme, and the focal length of the atomic lens and its radius of focused spot can be continuously changed by adjusting the current in the wires.

Discussion on compact mechanism of air-stream and synchro-formed clamp plate impact molding

Applying the air impact molding method to mold the complicated pattern with wider opening surface and deeper concave, there always exist vaulted phenomenon and lower compactibility of sand mold over the entrance and the concave regions. Using the air-stream and synchro-formed clamp plate impact molding, however, this problem will be preferably solved. In this paper, the compact mechanism of the new molding method and the effect of some configuration factors, such as the area flowed by compressed air and the highness of the protruding block displacement around the diffluent clamp plate, on the compactibility of sand mold were discussed.

Fast electrons collimating and focusing by an ultraintense laser interacting with a high density layers

The use of a novel double-cone funnel target with high density layers （HDL） to collimate and focus electrons is investigated by two-dimensional particle-in-cell simulations. The proposed scheme can guide, collimate and focus electron beams to smaller sizes. The collimation reasons are analyzed by the quasi-static magnetic fields generation inside the beam collimator with HDL. It is found that the energy conversion efficiency is increased by a factor of 2.2 in this new scheme in comparison with the that without HDL. Such a target structure has potential for design flexibility and prevents inefficiencies in important applications such as fast ignition, etc.