Analysis of operating limits and combustion state regulation for low-calorific value gases in industrial burners

The effective and efficient utilization of low-calorific value (LCV) gases has gained increasing attention in scientific research and industrial fields. In this study, the combustion characteristics of three LCV gases in practical devices are analyzed by using a nonadiabatic perfectly stirred reactor model. The complete steady-state solution in the temperature-residence time parameter space is obtained with arc-length continuation. The stable operation region is quantified by the eigenvalue analysis. The transition of solution curves is quantified with heat loss coefficient. Five key system parameters are systematically investigated on their effects on stability limits. With the combustion performance being quantified by a combustion state index, a combustion state regulation method is proposed to find the optimal regulation path of system parameters. Active subspace method is further applied to shorten the regulation step by identifying the active direction. The proposed method and findings are useful for optimal regulation of burning LCV gases in industrial burners.     

Symmetry properties and bifurcation analysis of a class of periodically forced chemical reactors

In this work, we discuss how periodic forcing may induce symmetry properties into mathematical models of chemical reactors. We define a class of reactors subjected to discontinuous periodic forcing, and show that all the reactors belonging to this class have spatio-temporal symmetry. This symmetry and its influence on the possible bifurcation scenarios are discussed. The bifurcation analysis is carried out with suitable discrete systems that exploit a property of the Poincaré map. In fact, it is shown that the spatio-temporal symmetry induced by the forcing makes the Poincaré map of the continuous system an iterate of another map. On this basis, a technique to implement parameter continuation methods is proposed. With such a technique, it is also possible to characterize symmetric and nonsymmetric regimes and unstable limit sets otherwise undetected with “bruteforce” approaches. Examples for reverseflow reactors and networks of n-reactors with periodically switched feed and discharge positions are presented.     

五轴并联机床正解研究

并联机床运动学正解问题由于涉及到求解非线性方程组问题而不易解决。首先对五轴并联机床进行运动学建模，获得了其运动学方程；然后使用连续同伦方法，对上述方程组进行求解，并获得并联机床正解。     

A complex solution framework for the kinetostatic synthesis of a compliant four-bar mechanism

This paper presents a systematic solution framework for the kinetostatic synthesis of compliant four-bar mechanisms. The goal of the kinetostatic synthesis is to find feasible compliant mechanism solutions for a given set of kinematic and force/energy specifications. Similar to the synthesis of rigid body linkages, we first classify kinetostatic synthesis problems into three major categories: function, motion and path generations. The kinetostatic synthesis equations are derived by combining the kinematic synthesis and static equilibrium equations. We then propose a comprehensive framework based on polynomial solvers for obtaining solutions to these synthesis equations. When kinematic and static equations are decoupled, we solve first kinematic equations independently and then solve static equations for springs' stiffness. While they are coupled, we transform them into a polynomial form and solve them simultaneously with polynomial solvers. For this case a parameter continuation is devised to avoid computing for the junk solutions. At last, three representative examples are provided to demonstrate the solution process and verify the solution framework.     

新一代调控系统分析决策中心业务多活框架与技术

新一代电网调度控制系统采用"物理分布、逻辑统一"的体系架构,全局分析决策业务集中部署于多个异地分析决策中心。在研究新一代电网调度控制系统分析决策业务运行时特征的基础上,提出了分析决策中心业务多活的技术框架,研发了负载均衡、中心容错、阶段结果数据同步、断点续算和业务单元化等关键技术,并结合原型系统进行了验证测试,实现了各分析决策中心地位均等,同时对外提供服务。确保了单个分析决策中心故障下,其他中心对核心业务或全部业务的快速接管,实现用户对中心故障的"透明无感知"。     

机床直行部件运动误差的在线测量

提出了采用精确时域两点法测量机床直行部件运动误差的新方法。该方法可以克服利用经典频域三点法测量直行部件运动误差时,由于误差的非周期性、非封闭性以及端点不连续而引起的高阶谐波分量失真等边缘效应。另外,该方法既可以得到机床直行部件的运动误差,又可以得到在该机床上加工零件的直线度形状误差,这些测量信息都有助于诊断机床的误差源,以提高机床的加工精度。     

Pseudo-transient continuation-based variable relaxation solver in nonlinear magnetohydrodynamic simulations

Efficient and robust Variable Relaxation Solver, based on pseudo-transient continuation, is developed to solve nonlinear anisotropic thermal conduction arising from fusion plasma simulations. By adding first- and/or second-order artificial time derivatives to the system, this type of method advances the resulting time-dependent nonlinear PDEs to steady state, which is the solution to be sought. In this process, only the stiffness matrix itself is involved so that the numerical complexity and errors can be greatly reduced. In fact, this work is an extension of integrating efficient linear elliptic solvers for fusion simulation on Cray X1E. Two schemes are derived in this work, first- and second-order variable relaxations. Four factors are observed to be critical for efficiency and preservation of solution's symmetric structure arising from periodic boundary condition: refining meshes in different coordinate directions, initializing nonlinear process, varying time steps in both temporal and spatial directions, and accurately generating nonlinear stiffness matrix. First finer mesh scale should be taken in strong transport direction; next the system is carefully initialized by the solution with linear conductivity; third, time step and relaxation factor are vertex-based varied and optimized at each time step; finally, the nonlinear stiffness matrix is updated by just scaling corresponding linear one with the vector generated from nonlinear thermal conductivity.     

城市设计中的记忆追寻——2014郑州滨水新区国际联合设计工作营后的思考

《城市意象》开启了认知城市的新方式,它打破了《雅典宪章》中传统的"功能规划"思想.城市除了功能外对人有更多的意义,城市景观在城市的众多角色中,依然是人们可见、可忆、可喜的源泉.景观都市主义的兴起,改变了整个城市系统的设计理念.它把建筑与基础设施看成是景观的延续,景观系统成为整个城市的载体.进一步延续这条线索,在郑州滨水新区国际设计工作营的三个追寻城市特色的概念方案的探索中,追寻城市记忆成为又一个最重要问题.回溯记忆的源头,从江户一路发展到今天的东京能给我们带来启发.中国传统城市格局中蕴含着先人们认知、建造城市的方式,回到最初才能找到城市设计中要追寻和保留的城市记忆.     

一类二阶时滞微分方程非局部共振问题解的存在性与唯一性

利用Mawhin连续性定理研究了一类具有时滞的二阶微分方程三点共振边值问题,获得了该边值问题解的存在性和唯一性的一些新的结果。     

Motion planning in velocity affine mechanical systems

We address the motion planning problem in specific mechanical systems whose linear and angular velocities depend affinely on control. The configuration space of these systems encompasses the rotation group, and the motion planning involves the system orientation. Derivation of the motion planning algorithm for velocity affine systems has been inspired by the continuation method. Performance of this algorithm is illustrated with examples of the kinematics of a serial nonholonomic manipulator, the plate-ball kinematics and the attitude control of a rigid body.