A rate-based method for dynamic analysis and optimal design of reactive extraction: n-Hexyl acetate esterification as an example

The dynamic analysis and optimal design of reactive extraction are challenging due to high nonlinearity of model equations and tough decision of judging criteria. In this work, a dynamic rate-based method is developed on g PROMS platform to get easy access to the solutions of reactive extraction with phase splitting. Based on rigorous criteria, dynamic analysis from initial state to final equilibrium(e.g., evolution of phase composition, mass transfer rate and reaction rate) and optimal design of operating conditions(e.g., extractant dosage and feed molar ratio) are achieved. To illustrate the method, the esterification of n-hexyl acetate is taken as an example. The approach proves to be reliable in the analysis and optimization of the exemplified system, which provides instructive reference for further process design and simulation of reactive extraction.

Optimal control approach to stability criteria on Hill's equations

This paper gives a tutorial on how to prove Lyapunov type criteria by optimal control methods. Firstly, we consider stability criteria on Hill’s equations with nonnegative potential. By optimal control methods developed in 1990s, we obtain several stability criteria including Lyapunov’s criterion, Neǐgauz and Lidskiǐ’s criterion. Secondly, we present stability criteria on Hill’s equations with sign-changing potential in which Brog’s criterion and Krein’s criterion are included.

Optimal Design Criteria of Tandem Configuration for High-Load Compressor Cascades

Axial overlap(AO)and percent pitch(PP)are considered as key position configuration parameters that affect the tandem cascade performance.The objective of the current study is to investigate the optimal design criteria for these two parameters in tandem cascades of subsonic highly-loaded two-dimensional compressors.Before that,the influence mechanisms of AO and PP are explored separately.Research results show that higher PP is beneficial for decreasing rear blade(RB)load,but an invalidity of gap flow occurs when it approaches 1.The change in AO has an influence on the adverse pressure gradient of the front blade(FB),and it also affects the gap flow strength and FB wake development.Then,the optimal design criteria for AO and PP are obtained in a large design space,which clarifies the matching relationship of the two parameters at different operating conditions.The best global range of AO is about-0.05 to 0.05 while PP is between 0.85 to 0.92,and PP should be smaller to avoid performance degradation as AO increases.According to the fault tolerance in practical applications,PP should be closer to the lower bound to ensure that the deterioration boundary is wide enough.

Coordinated optimal allocation of water resources and industrial structure in the Beijing-Tianjin-Hebei regions of China

Optimizing the allocation of water resources is critical for promoting the optimization and upgrading of industrial structure and coordinated development in the Beijing-Tianjin-Hebei regions of China.Based on specific regional and water conditions,to strengthen the constraints on water resources,the“three-step”adaptive management approach of“scheme design-scheme diagnosis-scheme optimization”of water resource allocation are adopted to facilitate the coordinated optimal allocation of water resources and industrial structure in the Beijing-Tianjin-Hebei regions.First,from the level of overall industry,a water resource allocation scheme for the regions is designed by applying the master-slave hierarchical mode and a bi-level optimal model to determine the ideal amount of water resource allocation for the regions and respective industries.Second,the diagnostic criteria of spatial balance,structural matching,and coordinated development are constructed to determine the rationality of the water resource allocation scheme.Then a benefit compensation function with water market transactions is developed,to adaptively adjust the water resource allocation scheme.Finally,the optimization and upgrading of industrial structure are promoted to improve water consumption efficiency and the coordinated development of the Beijing-Tianjin-Hebei regions.The study can provide reference for the Beijing-Tianjin-Hebei regions to realize the comprehensive optimal allocation of water resources in the regions and improve the adaptability of water resources and industrial structure optimization.

Combined Life Cycle Assessment and Costing Analysis Optimization Model Using Multiple Criteria Decision Making in Earth-Resource Systems

Life Cycle Assessment (LCA) is a comprehensive method to evaluate all attributes or aspects of potential environmental impact throughout a product’s lifecycle. Financial impacts are often added to the systemic evaluation process to reflect both environmental and economic assessment. For the specific application of LCA informing design of new technologies, when numerous variables are undecided or under defined, the process of forming an inventory of complete dataset is very difficult. Accumulating the early data consumes time, and limits application of LCA to new technologies and projects. As such, LCA may not normally be associated with forecasting or guiding a design/production process with an incomplete data set. Here, a life cycle assessment optimization model (LCAO) is described for incomplete data sets, based on the life cycle inventory (LCI) hybrid method and a modified multiple criteria decision making (MCDM) approach. The approach requires data, but can proceed in the given an incomplete or uncertain data set. The model of the algorithm also shows promising results to reveal previously unknown key variables within the dataset, which can then facilitate the minimization of environmental impact while maximizing economic benefits in product design.

Bi-Criteria Optimization Technique in Stochastic System Maintenance Allocation Problem

In this paper, the problem of optimum allocation of repairable and replaceable components in a system is formulated as a Bi-objective stochastic non linear programming problem. The system maintenance time and cost are random variable and has gamma and normal distribution respectively. A Bi-criteria optimization technique, weighted Tchebycheff is used to obtain the optimum allocation for a system. A numerical example is also presented to illustrate the computational details.

An Application of the Maximum Theorem in Multi-Criteria Optimization, Properties of Pareto-Retract Mappings, and the Structure of Pareto Sets

In this paper we consider three problems in continuous multi-criteria optimization: An application of the Berge Maximum Theorem, properties of Pareto-retract mappings, and the structure of Pareto sets. The key goal of this work is to present the relationship between the three problems mentioned above. First, applying the Maximum Theorem we construct the Pareto-retract mappings from the feasible domain onto the Pareto-optimal solutions set if the feasible domain is compact. Next, using these mappings we analyze the structure of the Pareto sets. Some basic topological properties of the Pareto solutions sets in the general case and in the convex case are also discussed.

Optimal Route Selection Method Based on Vague Sets

Optimal route selection is an important function of vehicle trac flow guidance system. Its core is to determine the index weight for measuring the route merits and to determine the evaluation method for selecting route. In this paper, subjective weighting method which relies on driver preference is used to determine the weight and the paper proposes the multi-criteria weighted decision method based on vague sets for selecting the optimal route. Examples show that, the usage of vague sets to describe route index value can provide more decision-making information for route selection.

Multi-Criteria Decision Analysis for Usage Based Optimization of Powertrains

The electrification of powertrains leads to an increasing diversification of powertrain configurations. Each single configuration has its specific advantages which appear depending on the usage profile. To find the usage based optimal powertrain in consideration of a variety of evaluation criteria, the powertrains have to be optimized for the usage profile and characteristics have to be extracted from the usage profile. The carbon dioxide emissions of the optimized powertrains and usage based criteria are used in a multi-criteria decision analysis to determine the optimal powertrain for a specific usage profile. The description of characteristic maps forms the objective function of a minimization problem. The determined carbon dioxide emissions are one criterion in a multi-criteria decision process. All considered criteria are at least partly objective so that subjective ratings are eliminated as far as possible. The result is an optimized powertrain for a desired usage under the consideration of objective criteria that are extracted from the usage profile.

气流分选技术研究进展

双碳背景下,气流分选技术因污染低、成本低、不用水、投资省、工艺简单等优势备受关注。为提升气流分选技术在多领域、多地区、多工况的适应性,解决气流分选物料适用范围窄、细粒分选效率低、设备大型化难等问题迫在眉睫。围绕气流分选理论、技术应用和技术改进3方面系统评述气流分选技术研究进展。首先,介绍了气流分选技术原理,分析气流分选过程颗粒受力及分选理论进展;其次,综述了气流分选在固废、矿业、农业等领域的应用进展,并评析了技术优势和技术短板;再次,系统分析了气流分选供风方式优化和设备结构优化等技术改进进展;最后,给出了通过单体并联和相似放大准则提高设备处理量,通过预干燥、分选干燥一体化、改进入料方式提高潮湿物料适应性与分散性,通过窄粒级分选和保持物料形状一致性的预处理过程提高细粒和薄片物料分选效率等路径。展望了未来气流分选技术在线检测与控制智能化、分选装备大型化、分选效率精细化、分选工艺联合化等方面的发展方向,为气流分选技术进一步研究和推广应用提供重要依据。

热电器件性能的权衡优化研究

热电器件能够实现热能与电能的直接转换,在废热利用和发展洁净能源技术方面具有特殊优势,而增强热电器件的热力学性能更具有实践性意义.本文利用权衡优化方法(也称Ω判据)研究了热电器件的热力学特征,在构建权衡优化目标函数的基础上,得到了权衡优化判据下的效率和制冷系数表达式,详细阐释了热电品质因子对于效率和制冷系数的影响.与最大功率(最大制冷功率)方法进行比较,发现权衡优化下的热电器件容易实现热力学性能的提高.

基于NSGA-Ⅱ的复合材料防撞梁碰撞损伤多目标优化

为在设计时考虑低速碰撞损伤对碳纤维复合材料(CFRP)防撞梁力学性能的影响,发展了改进Hashin失效准则的VUSDFLD子程序来判定低速碰撞时CFRP防撞梁7个方向的损伤程度,采用壳单元模拟了复合材料的力学性能,建立了CFRP防撞梁低速碰撞有限元显式动力学模型。采用该方法对相同实验条件下的复合材料层合板低速冲击剩余强度进行了计算,并将计算结果与实验结果进行了对比,仿真结果与实验结果吻合较好。在此基础上,以复合材料防撞梁铺层厚度和铺层角度为设计变量,将复合材料防撞梁的质量和低速冲击时产生的损伤单元数作为优化目标,建立了CFRP防撞梁低速碰撞损伤动力学多目标优化模型,采用基于Pareto策略改进的NSGA-Ⅱ非支配排序遗传算法对其进行多目标优化求解。优化后,CFRP防撞梁质量由1.02 kg降为0.76 kg,减重率为25%;损伤单元数由30238个降为23206个,损伤降低率为23%。结果表明,所发展基于Hashin失效准则的VUSDFLD子程序和对CFRP防撞梁低速碰撞损伤多目标优化是行之有效的,为复合材料防撞梁结构的优化设计提供了参考。

陕西地震行业网优化的实践

陕西地震行业网承担地震数据汇集与转发、地震速报与编目、公共信息服务、地震应急等功能,经过多年的建设运行,已具备一定的安全防御能力。但随着公共网络安全行业的发展变化,陕西地震行业网在网络结构、安全防御、设备配置、机房环境、制度建设等方面存在的不同程度的缺陷与隐患逐一显现。本文以安全等级保护测评、密码应用测评为依据,对陕西地震行业网在重塑网络结构、优化设备配置、健全制度机制、升级机房环境等方面进行了一系列的优化改造,为陕西省地震局网络优化技术升级、运维保障、安全运行、有效管理提供了良好基础。此次陕西地震行业网的优化升级改造经验,可为其他单位及行业网的网络优化升级改造建设提供一定经验借鉴。

复合材料机翼多工况下的自适应优化设计

为获得具有优良气动性能且兼具结构强度及轻量化的复合材料飞机机翼,提出考虑气动分析和结构分析多目标多工况优化方法。分别对机翼进行气动分析及结构强度分析,以机翼展弦比、锥度比、后掠角为几何优化变量,以机翼上下机翼蒙皮的-45°、90°、45°、0°层厚度和夹芯厚度为结构优化变量,建立以应力、位移为约束,以升阻比最大化和质量最小化为目标的协同优化模型。针对复合材料机翼多目标优化设计存在的计算量大难以取舍的问题,提出基于多准则和物理规划的自适应约束Kriging模型多目标优化算法(adaptive constraint kriging model multi-objective optimization algorithm based on multi-criteria and physical programming,AKBCP)。该算法引入了物理规划法和多准则加点,通过测试算例对比分析表明该算法具有较好的优化效果。将该算法应用到机翼多目标优化中,与初始机翼相比,优化后机翼升阻比提高3.12%,质量减轻31%,研究结果可为复合材料机翼优化设计提供参考。

面向供水管网漏损监测的传感器优化布置多准则决策分析方法

供水管网漏损精准监测对于避免水资源浪费具有重要意义,为此,提出一种面向供水管网漏损监测的传感器优化布置多准则决策分析方法。基于充分考虑传感器布置优化的权重、差异阈值和偏好阈值的不确定性,利用信息熵在整个决策空间内对传感器的初始位置进行筛选再根据漏损监测目标,通过定义一组传感器布置优化准则,利用多准则决策分析方法对初始方案进行排序,得到顾及多组参数及不同偏好场景下各种初始方案的概率排序。为了验证该方法的适用性,采用基准测试管网k1模型开展仿真试验并比较了几种不同的偏好场景。结果表明所提出的方法能够适应顺序优先和最重要的优先顺序,而且能够对方案进行排序和成对比较,避免了使用“黑匣子”对传感器布置方案进行选择。

基于多准则决策方法的作战方案优选方法

作战方案评估优选的过程往往存在主观性过强和忽略指标间内部关联关系等问题,这些问题会对作战决策的结果产生一定影响。针对作战决策中作战方案优选的问题,通过结合最优最劣法(BWM)、基于指标相关性的指标权重(CRITIC)确定法、多准则优化妥协决策(VIKOR)和梯形模糊数,提出一种用于作战方案评估优选的决策方法。首先,根据作战方案核心要素构建评估指标体系。然后,综合运用模糊BWM和基于距离相关系数的CRITIC为评估指标综合赋权,根据指标的组合权重信息和评价信息通过VIKOR法对各候选方案进行优选排序。最后,应用该方法解决了防御作战方案优选的实际问题,并通过对比分析和讨论,验证了该文所提作战方案优选决策方法的有效性。

HCO-ADE求解单点交叉口信号配时问题

为克服信号配时问题求解中单一约束优化方法的局限性,提出混合约束优化自适应差分进化算法(HCO-ADE)。以交叉口通行效率为目标建立信号配时优化模型,依据模型中约束条件被满足程度,采用外罚函数法和可行性准则法相结合的混合约束优化策略(HCOS)对约束条件进行处理,并提出饱和度偏好准则作为自适应差分进化算法(ADE)的选择策略,构建HCO-ADE。最后,以哈尔滨市四相位交叉口高峰时段5 min采集标段交通量数据为例,验证HCO-ADE。结果表明:提出的信号配时问题求解方法可行、有效,优于基于饱和度区间可能度的罚函数约束优化自适应差分进化算法(PFCO-ADE),所得信号配时方案较实测方案平均延误减少3.32%,通行能力提高2.16%,能够更好地提高信号配时方案稳定性。

桥梁传感器优化布置的研究现状与发展趋势

桥梁在交通网络中充当着极其重要的角色,其正常运行与否关系到人民生活幸福指数的高低。所以,为其建立结构健康监测系统以实时监测其安全状态、预警其异常行为及预测其工作性能走向的方法极为必要。桥梁结构传感器的优化布置,简单来说就是通过正确合理地布置所需传感器来获取桥梁的各项信息。传感器的优化布置研究的关键则在于其布置方法与评价准则,国内外的学者经过多年的研究,在该领域取得一定的突破与创新,但是仍然存在很多不完善的地方,如何通过改进各种算法来确定传感器优化布置最优解成为研究的主要方向。该文重点阐述传感器优化布置准则和传感器优化布置的方法在目前研究方向中发挥的重要作用,并对桥梁健康监测的后续发展表达看法和展望。

基于覆盖准则的多轮测试用例优先排序方法

针对测试用例优先排序中存在的覆盖准则选择困难、确定最优准则序列难等问题,提出了一种基于扩展有限状态机模型的最优覆盖准则序列排序方法(CWTCP)。该方法首先运用鲸鱼优化算法挑选出最优覆盖准则序列,为后续的排序提供了有力支持;其次将覆盖准则序列依次应用在多轮排序中,以应对可能出现的平局问题。为了验证CWTCP方法的有效性,在5个扩展有限状态机模型上进行了实验,采用平均故障检测百分比(APFD)作为度量标准。实验结果表明,CWTCP的平均APFD值为0.918,比随机算法的相应值高了19.8%。

约束多目标优化问题的一类内-外混合罚函数方法

该文提出一种内-外混合罚函数方法求解具有等式和不等式约束的多目标优化问题.其中罚函数由目标函数,内点罚函数和可行集外点罚函数构成.在适当的条件下,借助具有单调性的辅助函数,证明了算法所生成的迭代序列收敛于问题的Pareto最优解或弱Pareto最优解.同时给出了三个数值实验来验证算法的可行性.最后将算法应用于解决多指标交通网络最小费用流问题,并与线性加权法进行比较,结果表明该算法在时间成本上具有明显的优势.