10℃条件下纳米C-S-H掺量对水泥早期水化的影响

目的探究10℃条件下不同掺量纳米C-S-H对水泥早期水化进程及强度发展的影响,并分析其早强剂作用机理。方法通过溶液共沉淀法制备纳米C-S-H悬浮液,将其掺入到普通硅酸盐水泥中,在10℃条件下进行养护,分析其对水泥凝结时间、抗折强度、抗压强度的影响;通过XRD、TG等检测手段分析水泥的水化进程及对水化产物的影响。结果掺入0.05%纳米C-S-H,可使水泥初凝时间缩短9.9%,终凝时间缩短10.4%;24 h时抗折强度和抗压强度分别提高了34%和33.5%。纳米C-S-H的掺入造成水泥3 d抗折强度略有降低。水化产物中Ca(OH)2质量分数在12 h、16 h和24 h时较参比样分别提高了17.6%、21.3%和29.6%。结论在10℃条件下,纳米C-S-H的加入能够有效促进C 3S和C 2S的水化过程,形成更多的水化产物,从而缩短水泥凝结时间,提高24 h内水泥砂浆强度,28 d强度没有显著降低。

基于T-S模糊逻辑的混合储能孤岛直流微电网功率分配控制

在含混合储能的直流微电网中,传统阻容下垂控制无法解决由线路电阻和负荷功率波动导致的系统功率分配失衡问题。为此,提出一种基于Takagi-Sugeno(T-S)模糊逻辑的自适应阻容下垂控制方法以实现混合储能的分频分配。根据蓄电池和超级电容的物理特性,建立单个蓄电池支路输出电压、蓄电池组间输出功率差额和阻性下垂系数之间的T-S模糊逻辑关系,以及单个超级电容支路输出功率及其变化率、超级电容组间功率差额和容性下垂系数之间的T-S模糊逻辑关系,并由此构建基于T-S模糊逻辑的阻容下垂控制器。推导含混合储能的直流微电网中各部分的平均阻抗模型,并采用阻抗比分析法对微电网的小信号稳定性进行研究。MATLAB/Simulink仿真结果表明,基于T-S模糊逻辑的阻容下垂控制可保证在线路电阻和负荷功率波动情况下系统功率的合理分配。

固定翼UAV路径跟踪的全局稳定积分滑模S面控制

针对固定翼无人机的三维路径跟踪控制问题,设计了一种基于全局稳定积分滑模S面模型的内外环控制器。控制器外环采用全局稳定积分滑模控制,内环采用S面控制。设计控制器外环的全局稳定积分滑模控制律,并采用Lyapunov理论证明所设计控制律的稳定性。对内环的指令信号设计S面控制器,考虑到S面控制器中求导的复杂性,引入二阶微分器,解决内环中导数存在积分爆炸的问题。半物理仿真试验结果表明,提出的控制器能精确跟踪期望路径,具有良好的控制性能和抗干扰性能。

S对铸造高温合金K417G凝固行为的影响

在1340~1230℃采用等温凝固实验,研究了w[S]分别为0.0001%、0.0018%和0.0037%对K417G合金凝固特性的影响。结果表明,S降低合金的固相线温度,扩大固液两相区,当w[S]从0.0001%增加到0.0037%时,合金的固相线温度由1255℃降低至1245℃。在凝固过程中S元素偏析于液相,并在终凝区析出Y相,且S促进Al、Cr元素在固液界面处的富集。在相同等温温度下,S元素对MC碳化物和γ+γ’共晶的析出温度与形貌无明显影响,但S含量的增加促使MC碳化物、γ+γ’共晶和Y相数量的增加,且Y相的析出温度从1230℃提升至1240℃。

Energy Stable Nodal DG Methods for Maxwell’s Equations of Mixed-Order Form in Nonlinear Optical Media

In this work,we develop energy stable numerical methods to simulate electromagnetic waves propagating in optical media where the media responses include the linear Lorentz dispersion,the instantaneous nonlinear cubic Kerr response,and the nonlinear delayed Raman molecular vibrational response.Unlike the first-order PDE-ODE governing equations considered previously in Bokil et al.(J Comput Phys 350:420–452,2017)and Lyu et al.(J Sci Comput 89:1–42,2021),a model of mixed-order form is adopted here that consists of the first-order PDE part for Maxwell’s equations coupled with the second-order ODE part(i.e.,the auxiliary differential equations)modeling the linear and nonlinear dispersion in the material.The main contribution is a new numerical strategy to treat the Kerr and Raman nonlinearities to achieve provable energy stability property within a second-order temporal discretization.A nodal discontinuous Galerkin(DG)method is further applied in space for efficiently handling nonlinear terms at the algebraic level,while preserving the energy stability and achieving high-order accuracy.Indeed with d_(E)as the number of the components of the electric field,only a d_(E)×d_(E)nonlinear algebraic system needs to be solved at each interpolation node,and more importantly,all these small nonlinear systems are completely decoupled over one time step,rendering very high parallel efficiency.We evaluate the proposed schemes by comparing them with the methods in Bokil et al.(2017)and Lyu et al.(2021)(implemented in nodal form)regarding the accuracy,computational efficiency,and energy stability,by a parallel scalability study,and also through the simulations of the soliton-like wave propagation in one dimension,as well as the spatial-soliton propagation and two-beam interactions modeled by the two-dimensional transverse electric(TE)mode of the equations.

专家控制-改进S面算法在近水面航行器运动控制中的应用研究

[目的]旨在提高舵板响应速度和效率,以满足近水面航行器在静水及波浪干扰下的深度保持和姿态控制要求。[方法]在S面算法的基础上,提出一种具有更快收敛速度的改进S面控制算法,并与专家智能控制相结合,建立闭环专家控制-改进S面算法的混合控制模型,构建混合算法控制器。对比分析PID算法、S面算法、改进S面算法以及专家控制-改进S面算法在近水面航行器航行深度、姿态控制间的差异,并进行波浪干扰下的运动预报。[结果]预报结果表明:改进S面算法在静水航行控制中可提高收敛速度,波浪干扰下可降低纵摇幅度;专家控制-改进S面算法能够提高舵的控制效率,在静水中快速实现航行状态稳定转换,在波浪中有效降低近水面航行器垂荡和纵摇幅值30%以上。[结论]所提专家控制-改进S面算法对近水面航行器运动稳定性的提高适用性良好。

基于S-SAR边坡雷达的滑坡形变监测分析研究

露天矿山边坡安全是矿山安全的保障,边坡表面变形监测数据分析有助于获得准确的滑坡时间预测,因此,滑坡形变监测分析研究是研究的重点。本文对比分析了两个矿山滑坡时的合成孔径边坡雷达变形监测数据,获得了在滑坡时边坡表面变形监测特征曲线,进而建立了变形特征曲线与滑坡之间的关系。通过分析发现了边坡在发生破坏性变形之前会有多次异常的加速变形现象,这一点与斋藤法的三阶段变形相符。边坡在滑坡前并不会呈加速—匀速—再加速的变形规律,而是会重复多次加速—匀速—加速循环的变形现象。

Effect of cyclic drying and wetting on engineering properties of heavy metal contaminated soils solidified/stabilized with fly ash

团结 / 稳定(S/S ) 是重金属污染了土壤的处理的最有效的方法之一。在团结 / 稳定的污染土壤上的周期的弄湿并且弄干的效果被调查。一系列测试节目，自由压缩力量(UCS ) 测试， TCLP 沥滤测试和扫描电子显微镜学(SEM ) 测试，在污染的铅和锌上被执行土壤由苍蝇灰团结 / 稳定。UCS 和 S/S 的重金属离子的沥滤的特征污染了的测试结果表演玷污显著地随苍蝇灰内容的增加被改进。S/S 土壤的 UCS 第一随弄干并且弄湿周期的时间的增加增加，在到达山峰以后，它与它减少。当污染物质内容更低时(1 000 mg/kg ) ， TCLP 集中稍微首先在周期的弄干并且弄湿下面减少，然后增加，而是变化是次要的。TCLP 集中在 5 000 mg/kg 的一个高污染物质内容下面是更高的，并且随弄干并且弄湿周期的时间的增加增加。扫描电子显微镜学(SEM ) 的结果测试与 UCS 测试和 TCLP 沥滤测试一致，它揭示在弄干并且弄湿周期以后设计稳定的污染土壤的性质的变化的微观机构。

Green's function solution for transient heat conduction in annular fin during solidification of phase change material

The Green＇s function method is applied for the transient temperature of an annular fin when a phase change material （PCM） solidifies on it. The solidification of the PCMs takes place in a cylindrical shell storage. The thickness of the solid PCM on the fin varies with time and is obtained by the Megerlin method. The models are found with the Bessel equation to form an analytical solution. Three different kinds of boundary conditions are investigated. The comparison between analytical and numerical solutions is given. The results demonstrate that the significant accuracy is obtained for the temperature distribution for the fin in all cases.

New delay-dependent robust stability and stabilization for uncertain T-S fuzzy time-delay systems under imperfect premise matching

To alleviate the conservativeness of the stability criterion for Takagi-Sugeno(T-S)fuzzy time-delay systems,a new delay-dependent stability criterion was proposed by introducing a new augmented Lyapunov function with an additional triple-integral term,which was firstly used to derive the stability criterion for T-S fuzzy time-delay systems.By the same approach,the robust stability issue for fuzzy time-delay systems with uncertain parameters was also considered.On the other hand,in order to enhance the design flexibility,a new design approach for uncertain fuzzy time-delay systems under imperfect premise matching was also proposed,which allows the fuzzy controller to employ different membership functions from the fuzzy time-delay model.By the numerical examples,the proposed stability conditions are less conservative in the sense of getting larger allowable time-delay and obtaining smaller feedback control gains.For instance,when the allowable time-delay increases from 7.3s to 12s for an uncertain T-S fuzzy control system with time-delay,the norm of the feedback gains decreases from(34.299 2,38.560 3)to(10.073 3,11.349 0),respectively.Meanwhile,the effectiveness of the proposed design method was illustrated by the last example with the robustly stable curves of system state under the initial condition ofx(0)=[3-1].

Stabilization of Discrete-time 2-D T-S Fuzzy Systems Based on New Relaxed Conditions

This paper is concerned with the problem of stabilization of the Roesser type discrete-time nonlinear 2-D system that plays an important role in many practical applications. First, a discrete-time 2-D T-S fuzzy model is proposed to represent the underlying nonlinear 2-D system. Second, new quadratic stabilization conditions are proposed by applying relaxed quadratic stabilization technique for 2-D case. Third, for sake of further reducing conservatism, new non-quadratic stabilization conditions are also proposed by applying a new parameter-dependent Lyapunov function, matrix transformation technique, and relaxed technique for the underlying discrete-time 2-D T-S fuzzy system. Finally, a numerical example is provided to illustrate the effectiveness of the proposed results.

EXPERIMENTAL RESEARCH ON DIRECTIONAL SOLIDIFICATION OF Al－4．5wt％Cu ALLOY BY ACRT METHOD

Accelerated crucible rotation technique(ACRT) has been used for the directional solidification of Al-4.5wt% Cu binary alloy.By rotating the crucible at varying rate and direction,forced liquid flows are aroused These flows include Ekman flow,Couette flow and Spiral Shear flow.Especially,Ekman flow acts directly at the L/S interface,changes diffusion and heat exchange conditions and has strong influences on the morphology of L/S interface.Experimental results show that,compared with normal Bridgman specimens,the solidification region is much narrower and the cell spacing is much smaller in ACRT specimens.These influences become much stronger when the accelerating rate is increased.

Impulsive stabilization of a class of nonlinear system with bounded gain error

Considering mechanical limitation or device restriction in practical application, this paper investigates impulsive stabilization of nonlinear systems with impulsive gain error. Compared with the existing impulsive analytical approaches,the proposed impulsive control method is more practically applicable, which includes control gain error with an acceptable boundary. A sufficient criterion for global exponential stability of an impulsive control system is derived, which relaxes the condition for precise impulsive gain efficiently. The effectiveness of the proposed method is confirmed by theoretical analysis and numerical simulation based on Chua＇s circuit.

Stability and stabilization of discrete T-S fuzzy time-delay system based on maximal overlapped-rules group

The problems of stability and stabilization for the discrete Takagi-Sugeno（T-S） fuzzy time-delay system are investigated.By constructing a discrete piecewise Lyapunov-Krasovskii function（PLKF） in each maximal overlapped-rules group（MORG）,a new sufficient stability condition for the open-loop discrete T-S fuzzy time-delay system is proposed and proved.Then the systematic design of the fuzzy controller is investigated via the parallel distributed compensation control scheme,and a new stabilization condition for the closed-loop discrete T-S fuzzy time-delay system is proposed.The above two sufficient conditions only require finding common matrices in each MORG.Compared with the common Lyapunov-Krasovskii function（CLKF） approach and the fuzzy Lyapunov-Krasovskii function（FLKF） approach,these proposed sufficient conditions can not only overcome the defect of finding common matrices in the whole feasible region but also largely reduce the number of linear matrix inequalities to be solved.Finally,simulation examples show that the proposed PLKF approach is effective.

Effects of Ca(Y)-Si modifier on interface morphology and solute segregation during directional solidification of an austenite medium Mn steel

The austenite medium Mn steel modified with controlled additions of Ca, Y, Si were directionally solidified using the vertical Bridgman method to study the effects of Ca（Y）-Si modifier on the solid-liquid （S-L） interface morphology and solute segregation. The interface morphology and the C and Mn segregation of the steel directionally solidified at 6.9 μtrn/s were investigated with an image analysis and a scanning electron microscope equipped with energy dispersive X-ray analysis. The 0.5wt% Ca-Si modified steel is solidified with a planar S-L interface. The interface of the 1.0wt% Ca-Si modified steel is similar to that of the 0.5wt% Ca-Si modified steel, but with larger nodes. The 1.5wt% Ca-Si modified steel displays a cellular growth parttern. The S-L interface morphology of the 0.5wt% Ca-Si＋1.0wt% Y-Si modified Mn steel appears as dendritic interface, and primary austenite dendrites reveal developed lateral branching at the quenched liquid. In the meantime, the independent austenite colonies are formed ahead of the S-L interface. A mechanism involving constitutional supercooling explains the S-L interface evolution. It depends mainly on the difference in the contents of Ca, Y, and Si ahead of the S-L interface. The segregation of C and Mn ahead of the S-L interface enhanced by the modifiers is observed.

New Approach to Stability Analysis and Stabilization of Discrete-Time T-S Fuzzy Descriptor Systems

The problems of stability and state feedback control for a class of discrete-time T-S fuzzy descriptor systems are investigated in this paper. Based on fuzzy Lyapunov function,a set of slack variables is introduced to remove the basic semi-definite matrix inequality condition to check the regularity,causality and stability of discrete-time T-S fuzzy descriptor systems; a new sufficient condition for the discrete-time T-S fuzzy descriptor systems to be admissible is proposed in terms of strict linear matrix inequalities( LMIs). And a sufficient condition is proposed for the existence of state feedback controller in terms of a set of coupled strict LMIs.Finally,an illustrative example is presented to demonstrate the effectiveness of the proposed approach.

A new neural network model for the feedback stabilization of nonlinear systems

A new neural network model termed ‘standard neural network model’ (SNNM) is presented, and a state-feedback control law is then designed for the SNNM to stabilize the closed-loop system. The control design constraints are shown to be a set of linear matrix inequalities (LMIs), which can be easily solved by the MATLAB LMI Control Toolbox to determine the control law. Most recurrent neural networks (including the chaotic neural network) and nonlinear systems modeled by neural networks or Takagi and Sugeno (T-S) fuzzy models can be transformed into the SNNMs to be stabilization controllers synthesized in the framework of a unified SNNM. Finally, three numerical examples are provided to illustrate the design developed in this paper.

海浪扰动下电液3-UPS/S舰船并联稳定平台振动特性分析

针对电液驱动的舰船并联稳定平台在实际工况下的振动问题,以电液3-UPS/S舰船并联稳定平台为研究对象,在考虑铰链刚度的基础上应用虚功原理建立稳定平台的动力学模型;通过海浪谱函数,计算了随机海浪激励下船舶的运动响应,进而得到稳定平台跟踪舰船运动的响应规律;分析了稳定平台在随机海浪激励条件下和初始工作空间内的固有频率变化特性;最后,为验证动力学模型的正确性,采用脉冲激励法对稳定平台样机进行模态试验,固有频率理论值与试验值的最大误差为4.66%,可以验证动力学模型的正确性。

不确定非方广义分数阶T-S模糊系统的鲁棒镇定

针对不确定非方广义分数阶T-S模糊系统阶数为0<α<1的鲁棒镇定问题,提出了一个有效的判据.首先,利用一个新的T-S模糊动态补偿器,将不确定非方广义分数阶T-S模糊系统转化为一个增广的不确定方形广义分数阶T-S模糊系统.由于增广变量的引入,动态补偿器的设计问题可以等价为静态输出反馈控制器的设计问题.其次,设计一个分数阶导数反馈控制器对得到的增广系统进行正常化处理.然后,对正常化得到的不确定分数阶T-S模糊系统进行研究,得到一个系统渐近稳定的充分条件.该条件保守性小并且形式简洁.最后,通过一个数值算例和一个实际例子验证了本文所提出结论的正确性和有效性.