用微机图象法对脉冲MAG焊接熔池进行观察和控制的研究

本文对微机图象法在脉冲MAG焊接中的应用作了探讨,设计和采用了带有CCD摄象机的微机控制系统,对脉冲MAG焊接熔池进行了观察、监控和图象处理。其结果证明了采用微机图象法来实现实时控制是可行的。     

The study on the conductivity of styrene-maleic anhydride copolymer electrolytes based on poly(ethylene glycol)400 and LiClO4

Polyelectrolytes, in this study were synthesized from styrene-maleic anhydride (SMA) copolymer, poly(ethylene glycol)400 (PEG400), and lithium perchlorate (LiClO₄). Fourier transform infrared spectroscopy (FTIR), and magic angle spinning (MAS) solid-state NMR were used to monitor the interaction between Li⁺ ions and polymer. The results of FTIR and MAS solid-state NMR indicate the Li⁺ ions are preferentially coordinated to the ether oxygen of PEG. The T_g of the PEG segments in polyelectrolyte increases with LiClO₄ concentration, as determined by differential scanning calorimetry (DSC), indicating that solubility of the Li⁺ ions in the host polymer increases with the PEG content. Impedance spectroscopy (IS) shows that the bulk conductivity of polyelectrolytes and the conductivity behavior obeys the Vogel-Tamman-Fulcher (VTF) equation.     

12Ni3MoV钢焊接HAZ中的粒状组织

本文用热模拟技术研究了低温球罐用钢12Ni3MoV钢模拟焊接HAZ中的粒状组织和粒状贝氏体的组织形态、形成过程及影响因素。研究结果表明,12Ni3MoV钢两相区和细晶区的组织为粒状组织,粗晶区的组织为侧板条粒状贝氏体和针片状粒状贝氏体。奥氏体状态对冷却后的转变产物育显著的影响。奥氏体晶粒细小或奥氏体成分不均匀,冷却过程中易形成粒状组织,奥氏体晶粒粗大,且成分均匀,冷却过程中易形成粒状贝氏体。     

未焊透焊缝疲劳强度分析及工程应用

本文针对工程中焊接结构大量采用单面焊对接焊缝这一事实,对含有未焊透缺陷的单面焊对接焊缝试件进行了疲劳试验,得到了疲劳强度曲线。由于单面焊对接焊缝中的未焊透缺陷位于试件根部表面,在缺陷率相同的条件下,其疲劳强度损失比双面焊未焊透焊缝更严重。试件母材为低碳钢钢板(σ_b≥450MPa)。本试验结果应用于钢瓶焊缝的缺陷容限分析,为制订我国民用在役液化石油气钢瓶判废标准提供了实验依据。     

逆变式脉冲TIG焊机的研究

本文详述了逆变式脉冲TIG焊机的性能和基本工作原理,分析了系统的稳态误差,对焊接工艺性能及其特有的静外特性作了介绍,并提出了提高整机抗干扰能力和降低中频噪音的方法、措施。该焊机由于采用了中频逆变技术,使其效率和功率因数都有较大幅度的提高,不但减小了体积,减轻了重量,而且具有比传统TIG焊机更精密的控制、调节性能等。     

An LMI approach to synthesis subject to almost asymptotic regulation constraints

A multi-objective controller synthesis problem is considered in which an output is to be regulated approximately by assuring a bound on the steady-state peak amplification in response to an infinite-energy disturbance, while also guaranteeing a desired level of performance measured in terms of the worst-case energy gain from a finite-energy input to a performance output. Relying on a characterization of the controllers with which almost asymptotic regulation is accomplished, the problem of guaranteeing the desired level of performance is reduced to solving a system of linear matrix inequalities subject to a set of linear equality constraints. Based on the solution of this system, a procedure is outlined for the construction of a suitable controller whose order is equal to the order of the plant plus the order of the exogenous system.     

Controller synthesis with guaranteed closed-loop phase constraints

In this paper, we present an analysis and synthesis approach for guaranteeing that the phase of a single-input, single-output closed-loop transfer function is contained in the interval [−α,α] for a given α>0 at all frequencies. Specifically, we first derive a sufficient condition involving a frequency domain inequality for guaranteeing a given phase constraint. Next, we use the Kalman–Yakubovich–Popov theorem to derive an equivalent time domain condition. In the case where , we show that frequency and time domain sufficient conditions specialize to the positivity theorem. Furthermore, using linear matrix inequalities, we develop a controller synthesis approach for guaranteeing a phase constraint on the closed-loop transfer function. Finally, we extend this synthesis approach to address mixed gain and phase constraints on the closed-loop transfer function.     

中国环境艺术的系统化设计

文章通过中国环境艺术的系统化设计内涵及方法论的研究,从设计角度出发,对中国环境艺术设计的现状做出了明确的总结并且提出对于中国环境艺术设计在未来的展望,从此达到人与环境和谐共生,可持续发展的目的。     

A reactive GRASP and path relinking for a combined production–distribution problem

An NP-hard production–distribution problem for one product over a multi-period horizon is investigated. The aim is to minimize total cost taking production setups, inventory levels and distribution into account. An integer linear model is proposed as a compact problem specification but it cannot be solved to optimality for large instances. Instead of using a classical two-phase approach (production planning and then route construction for each day), metaheuristics that simultaneously tackle production and routing decisions are developed: a GRASP (greedy randomized adaptive search procedure) and two improved versions using either a reactive mechanism or a path-relinking process. These algorithms are evaluated on 90 randomly generated instances with 50, 100 and 200 customers and 20 periods. The results confirm the interest of integrating production and distribution decisions, compared to classical two-phase methods. Moreover, reaction and path-relinking give better results than the GRASP alone.