A high-throughput chaotic advection microreactor for preparation of uniform and aggregated barium sulfate nanoparticles

A high-throughput (105.5 g/h) passive four-stage asymmetric oscillating feedback microreactor using chaotic mixing mechanism was developed to prepare aggregated Barium sulfate (BaSO₄) particles of high primary nanoparticle size uniformity. Three-dimensional unsteady simulations showed that chaotic mixing could be induced by three unique secondary flows (i.e., vortex, recirculation, and oscillation), and the fluid oscillation mechanism was examined in detail. Simulations and Villermaux–Dushman experiments indicate that almost complete mixing down to molecular level can be achieved and the prepared BaSO₄ nanoparticles were with narrow primary particle size distribution (PSD) having geometric standard deviation, σ_g, less than 1.43 when the total volumetric flow rate Q_total was larger than 10 ml/min. By selecting Q_total and reactant concentrations, average primary particle size can be controlled from 23 to 109 nm as determined by microscopy. An average size of 26 nm with narrow primary PSD (σ_g = 1.22) could be achieved at Q_total of 160 ml/min.     

Polynomial filtering for nonlinear stochastic systems with state‐ and disturbance‐dependent noises

This article is concerned with the polynomial filtering problem for a class of nonlinear stochastic systems governed by the Itô differential equation. The system under investigation involves polynomial nonlinearities, unknown‐but‐bounded disturbances, and state‐ and disturbance‐dependent noises ((x,d)‐dependent noises for short). By expanding the polynomial nonlinear functions in Taylor series around the state estimate, a new polynomial filter design method is developed with hope to reduce the conservatism of the existing results. In virtue of stochastic analysis and inequality technique, sufficient conditions in terms of parameter‐dependent linear matrix inequalities (PDLMIs) are derived to guarantee that the estimation error system is input‐to‐state stable in probability. Moreover, the desired polynomial matrix can be obtained by solving the PDLMIs via the sum‐of‐squares approach. The effectiveness and applicability of the proposed method are illustrated by two numerical examples with one concerning the permanent magnet synchronous motor.     

干扰床分选机分选磷矿规律的试验研究

文中分析了我国丰富的磷矿资源及传统的分选磷矿方法,阐述了研究干扰床分选机分选磷矿的规律具有重要意义,研究设计了试验室干扰床分选机分选系统,试验采用宜昌某磷矿原矿中0~3.0mm粒度的粗矿泥进行试验研究,分析了干扰床分选机分选磷矿的规律,找出了分选最佳工况点并进行了对比曲线分析,论证了显著的经济效益和广阔的市场前景。     

煤油气共生矿井底板油型气赋存特征及防治

为了提高煤油气共生矿井油型气灾害治理的科学性，以黄陵二矿为例，采用现场测试、钻探取芯、跟踪观测、地质分析等多种方法，研究了采掘工作面煤层底板油型气分布特征、涌出规律和运移机理，并初步探讨了底板油型气体灾害防治措施。结果表明:底板油型气涌出点多位于底板砂岩储层上倾尖灭端和砂岩透镜体附近，呈现不连续区带状分布特征，涌出的油型气主要来自富县组砂岩层，涌出的动力主要为地层流体压力差，底板油型气通过地层中存在大量的断裂和裂缝、微裂缝系统进入采掘空间，采掘扰动是底板油型气异常涌出的工程诱导因素。建议加强油型气综合探查技术、油型气灾害预测预报技术、油型气综合抽采技术和智能化矿井建设等方面的研究。     

风速时间序列混沌判定方法比较研究

混沌识别是对非线性时间序列进行混沌预测的前提。针对时间序列风速确定性与随机性相结合的复杂非线性特征,研究了不同的混沌识别方法,并对风速时间序列进行混沌特征识别。应用随机噪声、周期运动及经典混沌系统的时间序列对所选方法进行可靠性验证。对美国国家风能研究中心M2测风塔实测时间序列风速数据进行非线性混沌特征识别。结果表明:风速时间序列具有明显的混沌特征;各风速时间序列表现出不同程度的混沌特征;各混沌识别方法对风速时间序列混沌特征的表达形式不同,互为补充,相互验证。     

开采扰动对中关铁矿堵水帷幕稳定性影响的数值模拟研究

注浆堵水帷幕技术在矿山基建和生产期可有效地堵截地下水而被众多大水矿山采用,矿山开采的同时需疏干堵水帷幕内围岩中的地下水,为探究疏干排水后开采扰动对堵水帷幕稳定性的影响规律,以中关铁矿堵水帷幕为研究对象,在详细分析矿区地质资料、帷幕内外水位变化规律的基础上,建立堵水帷幕三维地质、力学模型,采用数值模拟方法,分析疏干排水与开采扰动联合作用对堵水帷幕稳定性的影响。结果表明,堵水帷幕与强渗透性围岩接触区域及刚度与围岩差异较大区域,易形成高应力集中区;疏干排水与开采扰动联合作用对堵水帷幕、堵水帷幕与围岩接触区域应力场分布具有显著影响,矿床开采边界距帷幕越近,影响越显著。研究结果可为堵水帷幕稳定性监测提供依据。     

煤与瓦斯突出实时监测预警系统声—电噪声扰动分析

为了在金佳矿建立煤与瓦斯突出区域—局部动态实时监测预警系统，基于KJ838声电瓦斯系统，对11224运输巷工作面掘进周期内声发射与电磁辐射的噪声扰动进行了分析。结果表明:KJ838声电瓦斯系统能及时对巷道中的环境变化进行响应，放炮、开溜槽、开铲车等工序均会对声—电信号造成特定扰动。     

基于滑模的运载器主动段俯仰通道姿控系统设计

与传统比例-积分-微分（PID）控制方法相比，滑模控制（SMC）方法可以比较容易地将不确定性纳入控制器设计中，从而增强系统的鲁棒性。探索了SMC技术在运载器主动段姿态控制中的工程应用，首先通过分析基于趋近律的SMC系统，提出了降低不连续切换项系数的需求，然后研究了基于干扰上界的SMC方法。三通道小偏差仿真结果验证了两种方法的控制效果，表明第2种控制器的鲁棒性更好，稳态误差小，同时发动机喷管摆角需求较小。     

以减小初始扰动为目标的火箭弹定心部优化设计

In order to study the influences of rocket bourrelets structural parameters on the rocket initial disturbances, a dynamic simulation model of the interaction between rocket and rail was established. Taking minimizing initial disturbances as goals, and nonoccurrence of impact between rocket body and rail as constraint, launch dynamic simulation and optimal analysis of the rocket bourrelets were performed. The optimal design parameters of the rocket bourrelets were obtained. The optimal results show that the rocket bourrelets width has a large influence on initial disturbances, and the optimization of the bourrelets structural parameters may minimize initial disturbances of rocket to a great extent. The optimal method and results will provide reference to rocket bourrelet design.     

基于控制变量参数化方法的自由漂浮空间机器人路径规划研究

针对自由漂浮空间机器人传统路径规划方法对基座卫星扰动较大的问题，提出了一种基于控制变量参数化的路径规划方法。该方法将路径规划问题转化成以基座姿态扰动最小为目标函数并满足一系列约束条件的最优控制问题，并采用控制变量参数化方法进行离散化处理，将最优控制问题转化成求解非线性规划问题，并给出了完整的理论收敛性证明，从而准确地估计出自由漂浮空间机器人末端执行器的最优路径。仿真结果表明，与传统的分解加速度方法相比，该方法得到的运动路径所引起的基座卫星姿态扰动为0.104rad，相比传统方法降低了17.53%，验证了所提路径规划方法的有效性与最优性。