基于鲁棒性的概率优化设计在薄壁构件耐撞性中的应用

汽车结构的耐撞性及碰撞吸能优化是现代汽车工业重要的研究内容。耐撞性的优化涉及材料与结构的众多参数，传统的确定性优化设计、碰撞仿真及实验往往只能在一定程度上改善结构的碰撞性能，而无法评估设计参数的可靠性和目标函数的鲁棒性，以及在给定可靠性约束条件下使目标函数的鲁棒性达到最优状态。将实验设计、响应面模型和蒙特卡罗模拟技术相结合，构造了基于产品质量工程的6σ鲁棒性优化设计方法，实现了对设计目标的优化，并提高了设计变量的可靠性和目标函数的鲁棒性。     

轿车乘员约束系统的试验验证及参数优化

应用MADYMO模型进行虚拟试验或数值仿真是乘员约束系统开发流程中重要的方式。为得到可靠的计算结果,必需遵循规范的验证流程。详细介绍了MADYMO正面碰撞约束系统的建立和试验验证的流程。基于验证模型,进行了试验设计、参数灵敏度分析、响应面模型分析以及优化设计。优化设计结果使乘员受重伤的概率下降4.2%。在实际的工程应用中,利用MADYMO模拟可有效匹配约束系统的设计参数,达到稳健可靠的乘员保护效果。     

基于正交试验设计的乘员约束系统性能优化

在微型轿车正面碰撞过程中,乘员容易受到严重伤害,优化乘员约束系统对于乘员的保护极其重要。利用MADYMO软件建立了包含座椅、安全带、仪表板及转向系统在内的某微型客车乘员约束系统的分析模型,并通过试验验证了模型的有效性。最后利用验证后的模型对约束系统的参数应用正交试验设计的方法进行优化,实现了对该车正面碰撞过程约束系统的较全面且较可靠的评价。     

基于正交试验设计的乘员约束系统性能优化

在轿车正面碰撞过程中,乘员容易受到严重伤害,优化乘员约束系统对于乘员的保护极其重要。利用MADYMO软件建立了包含座椅、安全带、仪表板及转向系统在内的某轿车乘员约束系统的分析模型,并通过试验验证了模型的有效性。最后利用验证后的模型对约束系统的参数应用正交试验设计的方法进行优化,实现了对该车正面碰撞过程约束系统的较全面且较可靠的评价。     

优化法求解几何约束的问题

几何约束的求解对于变量设计系统是最为关键的问题,提出用优化求解的方法来求解循环约束,一定程度上克服了Newton-Raphson算法的不稳定性,且可较容易地求解欠约束和过约束的问题。     

优化法求解几何约束的问题

几何约束的求解对于变量设计系统是最为关键的问题 ,提出用优化求解的方法来求解循环约束 ,一定程度上克服了Newton -Raphson算法的不稳定性 ,且可较容易地求解欠约束和过约束的问题     

面向约束优化的改进响应面法在车身轻量化设计中的应用

轿车车身轻量化设计是一个多约束的复杂系统优化问题,且必须满足各项车身结构性能,其中碰撞安全性是先决条件.实际中普遍采用试验设计和响应面法相结合的手段开展轻量化研究.针对传统响应面法拟合约束函数易引起优化解落在非可行域内的缺陷,提出一种面向不等式约束函数的改进响应面法,使近似约束边界分布在可行域中,得到能够满足设计约束的优化解,数值算例验证了改进响应面法在处理约束优化问题中具有比传统响应面法更为明显的优势.将其应用到车身轻量化设计中,结果表明,基于本研究提出的改进响应面法的轻量化方案优于传统响应面法,整车耐撞性能得到提高的同时实现车身前部结构减重21.4%,为开展车身轻量化设计研究提供可借鉴的方法.     

基于MADYMO儿童乘员约束系统参数优化仿真研究

对汽车正面碰撞儿童乘员约束系统的参数优化进行仿真研究,运用MADYMO软件建立儿童约束系统仿真模型,并进行参数优化仿真,利用参数灵敏度来分析伤害指标的优化程度,将仿真结果进行对比验证,最终确定最优模型参数组合。该研究为儿童乘员约束系统的优化设计提供参考。     

遗传算法与惩罚函数法相结合在约束优化问题中的应用

提出了将遗传算法与惩罚函数法相结合应用于约束优化问题的具体方法,改善了遗传算法应用的局限性。     

基于可靠性优化的汽车乘员约束系统的性能改进

针对某款微型轿车,通过MADYMO软件建立并验证了该车的乘员侧正面碰撞约束系统仿真模型,并将试验设计、Kriging近似模型和可靠性理论相结合,构造了乘员约束系统可靠性优化设计方法。与传统的确定性优化结果相比较,可靠性优化结果不仅较好地满足了乘员约束系统的设计目标,而且大幅度地提高了系统设计约束的可靠性。     

null

根据复合双星排和复合双联排的各元件之间的相互啮合关系,建立了复合排的运动学方程组并确定了各元件的转速关系。通过建立多自由度行星变速机构的构件相对转速图,提出了一种多自由度复合行星传动方案设计理论和方法。确定了设计多自由度复合行星传动方案应满足的必要条件,以及组成复合排的各构件属性判别方法和行星排的特性参数计算方法。设计实例验证了该方法的可行性和正确性。     

基于桨叶模态修型的直升机减振优化

基于Hamilton原理推导了模态修型减振优化的有限元动力学模型,通过修改桨叶的剖面刚度和线密度来改变结构的动力学模态。以最小振动载荷为目标函数,以桨叶剖面刚度及质量为设计变量,以桨叶的频率、自转惯量、质量及模态修型参数等为约束条件,进行了减振优化。算例表明:在约束条件都满足的情况下,优化后,3/转的桨根剪力减小了55.4%,4/转的桨根剪力减小了66.5%,5/转的桨根剪力减小了53.4%,优化效果明显。     

基于序列响应面法的汽车结构件蜂群优化设计

将蜂群算法应用于汽车结构件的优化问题。先由试验设计和序列响应面法构建目标函数及约束条件的代理模型,再应用改进的蜂群算法求解最优设计。在优化过程中调用的是代理模型,显著减少了有限元计算次数,提高了优化效率。最后,选取典型实例对该算法进行验证,比较预期值与实际值的结果表明,该算法具备了足够的求解精度,能够满足工程实际要求。     

A Novel Consideration of Species Distribution of Copper(II)/Histidine System at Physiological pH

Abstract

The copper(II)–L‐histidine system plays a pivotal role in copper transport across cell membranes. The coordination mode of copper(II)–L‐histidine species at physiological pH has been elusive in aqueous solution for the last four decades, despite exhaustive characterization studies. Recently, the isolation and the X‐ray crystal structure of the physiological [Cu(His)₂] complex have been reported. The X‐ray structure is different from all the structures suspected for this complex in solution.

We carried out a polarographic analysis to identify copper(II)–L‐histidine species at physiological pH. In our experimental conditions, three copper(II)–L‐histidine species coexist around the physiological pH. These novel considerations can explain the controversy encountered in the investigation of the coordination mode in aqueous solution.     

End-grafted Sugar Chains as Aqueous Lubricant Additives: Synthesis and Macrotribological Tests of Poly(<Emphasis Type="SmallCaps">l</Emphasis>-lysine)-<Emphasis Type="Italic">graft</Emphasis>-Dextran (PLL-<Emphasis Type="Italic">g</Emphasis>-dex) Copolymers

Comb-like graft copolymers with carbohydrate side chains have been developed as aqueous lubricant additives for oxide-based tribosystems, in an attempt to mimic biological lubrication systems, whose surfaces are known to be covered with sugar-rich layers. As adopted in the previous studies of the graft copolymer poly(l-lysine)-graft-poly(ethylene glycol) (PLL-g-PEG), which showed both excellent lubricating and antifouling properties, a similar approach was chosen to graft dextran chains onto the same backbone, thus generating PLL-g-dex. PLL-g-dex copolymers readily adsorb from aqueous solution onto negatively charged oxide surfaces. Tribological characterization at the macroscopic scale, either under pure sliding conditions or a mixed sliding/rolling contact regime, shows that PLL-g-dex is very effective for the lubrication of oxide-based tribosystems. The relative lubricating capabilities of PLL-g-dex copolymers compared with PLL-g-PEG copolymers were observed to be highly dependent on the molecular structure of the copolymers (in particular, side-chain density along the backbone) and the measurement conditions (in particular, time between tribocontacts); the PLL-g-dex copolymers with a low degree of grafted side chains (≤20% grafting of available protonated primary amine groups along the backbone) showed better lubricating performance than their PLL-g-PEG counterparts at high tribocontact frequency (≥ca. 0.32 Hz).     

Self-healing behavior of a polyelectrolyte-based lubricant additive for aqueous lubrication of oxide materials

We report on the self-healing behavior of a polyelectrolyte-based aqueous lubricant additive, poly(l-lysine)-graft-poly(ethylene glycol) (PLL-g-PEG), during aqueous lubrication of an oxide-based tribosystem. Combined pin-on-disk tribometry and fluorescence microscopy experiments have shown that stable lubricating performance was enabled by means of rapid healing of the worn tribopair surface by polymers dissolved in the adjoining bulk lubricant. This rapid ‘self-healing’ of PLL-g-PEG is attributed to electrostatic interactions between the polycationic poly(l-lysine) (PLL) backbone of the polymer and negatively charged oxide surface. In contrast, a similar healing effect was not readily achievable in the case of methoxy-poly(ethylene glycol)-trimethylsilylether (Sil-PEG), a lubricant additive that is covalently bonded to the surface prior to tribological stress.     

Modeling, identification, and validation of models for predictive ammonia control in a wastewater treatment plant--a case study

The aim of this work is to develop the ammonia models that could be used for model predictive control (MPC) of nitrification process in a wastewater treatment plant. First, a reduced nonlinear model is presented, which is based on expression for nitrification reaction rate in activated sludge model No. 1 and modified for attached biomass processes, while second, a linear black-box model is shown. The data used for model identification were collected during several weeks of experiments on a real plant so that good identification data were obtained. The designed models were validated based on open loop simulations and predictions. Validation results show that the reduced nonlinear model performs better compared to the linear model, however, both models show relatively large errors compared to the real plant data. Hence, a closed loop simulation study was performed to see the differences between the performance of model predictive controller using previously estimated linear and nonlinear models and a standard proportional integral (PI) controller. From the simulation study results it was seen that in spite of relatively large model errors the MPC algorithms give better results in terms of ammonia removal compared to the PI controller, while MPC with the nonlinear model shows additional improvements over the MPC with the linear model.     

Mathematical models of the simplest fuzzy PI/PD controllers with skewed input and output fuzzy sets

This paper unveils mathematical models for fuzzy PI/PD controllers which employ two skewed fuzzy sets for each of the two-input variables and three skewed fuzzy sets for the output variable. The basic constituents of these models are Gamma-type and L-type membership functions for each input, trapezoidal/triangular membership functions for output, intersection/algebraic product triangular norm, maximum/drastic sum triangular conorm, Mamdani minimum/Larsen product/drastic product inference method, and center of sums defuzzification method. The existing simplest fuzzy PI/PD controller structures derived via symmetrical fuzzy sets become special cases of the mathematical models revealed in this paper. Finally, a numerical example along with its simulation results are included to demonstrate the effectiveness of the simplest fuzzy PI controllers.