基于结构代理模型与二级优化策略的航天结构模型修正研究

随着我国航天事业的不断发展,航天结构形式越来越复杂,有限元结构模型往往存在各种假设和简化,因此与实际结构往往存在一定的误差,特别是部件的连接、边界条件的不确定以及材料性能(尤其是复合材料)与工艺的不确定性,都会对有限元模型的分析精度产生较大影响。本文基于初始有限元模型,通过试验设计构造结构代理模型,然后采用遗传优化算法与梯度优化算法的二级优化策略进行模型修正。另一方面,在每次模型修正迭代分析之前,自动进行置信值MAC(Modal Assurance Criterion)分析,使有限元分析模型与实验结果进行匹配,提高模型修正的正确性。分析表明该修正方法具有较高的分析精度,也能对结构参数进行识别。

虚拟企业中的多代理技术研究

对虚拟企业中的多代理技术进行了研究 ,提出了虚拟企业的代理结构模型 ,讨论了基于多代理的虚拟企业运行机制 。

Multi-objective optimisation of a vehicle energy absorption structure based on surrogate model

In order to optimize the crashworthy characteristic of energy-absorbing structures, the surrogate models of specific energy absorption （SEA） and ratio of SEA to initial peak force （REAF） with respect to the design parameters were respectively constructed based on surrogate model optimization methods （polynomial response surface method （PRSM） and Kriging method （KM））. Firstly, the sample data were prepared through the design of experiment （DOE）. Then, the test data models were set up based on the theory of surrogate model, and the data samples were trained to obtain the response relationship between the SEA ＆amp; REAF and design parameters. At last, the structure optimal parameters were obtained by visual analysis and genetic algorithm （GA）. The results indicate that the KM, where the local interpolation method is used in Gauss correlation function, has the highest fitting accuracy and the structure optimal parameters are obtained as： the SEA of 29.8558 kJ/kg （corresponding toa=70 mm andt= 3.5 mm） and REAF of 0.2896 （corresponding toa=70 mm andt=1.9615 mm）. The basis function of the quartic PRSM with higher order than that of the quadratic PRSM, and the mutual influence of the design variables are considered, so the fitting accuracy of the quartic PRSM is higher than that of the quadratic PRSM.

Quotient space model based on algebraic structure

In the quotient space theory of granular computing,the universe structure is assumed to be a topology,therefore,its application is still limited.In this study,based on the quotient space model,the universe structure is assumed as an algebra instead of a topology.As to obtain the algebraic quotient operator,the granulation must be uniquely determined by a congruence relation,and all the congruence relations form a complete semi-order lattice,which is the theoretical basis of granularities ' completeness.When the given equivalence relation is not a congruence relation,it defines the concepts of upper quotient and lower quotient,and discusses some of their properties which demonstrate that falsity preserving principle and truth preserving principle are still valid.Finally,it presents the algorithms and example of upper quotient and lower quotient.The work extends the quotient space theory from structure,and provides theoretical basis for the combination of the quotient space theory and the algebra theory.

Modeling Farm Management Modernization： Case Study of Japanese Rice Farming Corporations

While conventional family-owned and family-operated farms remain the most common structure, the number of Japanese agricultural corporations has increased in recent years as a result of changing policies. Some of them are possibly starting to adopt modem corporate management practices to remain viable in a more competitive environment. However, changes in the business structure have not always been accompanied by changes in farm management practices. This study represents a theoretical and empirical investigation into farm modernization practices to provide perspective and recommendations to enhance farm business. Various aspects of farm modernization were considered, including temporal, economic and functional modernization. Critical elements of farm modernization were examined using a structural equation model of surveys, wherein questionnaires were delivered to 2,260 agricultural corporations across Japan in 2014 and 2016, generating 669 usable responses from rice farming corporations. Overall, these corporations demonstrated moderate degrees of modernization, indicating that they have not yet completely transitioned from conventional management styles to modem corporate management and that the farm-household complex system still exists for many of them. It was also found that farm modernization is significantly affected by both production and business management systems, although it was unclear whether a farmer＇s managerial capabilities were critical for farm modernization. The findings of this study indicate that current farming corporations may benefit from incorporating additional modernization practices. The analytical framework and results will help farmers to better understand their management practices and can be used to provide ideas for policy development to promote competitive farm businesses.