Coupling dynamic stiffness identification of mechanical assembly with linear and planar connection by the indirect scheme of inverse substructuring analysis

Mechanical assembly is an important process in manufacturing electromechanical products and it directly affects the dynamic quality of a whole product. The traditional inspection and analysis of mechanical assembly quality mainly focuses on the “static quality”, such as the shape accuracy and dimensional coordination, while ignoring its “dynamic quality”, which is incomplete estimation on the assembly quality. Meanwhile, the assembly coupling dynamic stiffness is a key determinant of the dynamic quality of mechanical assembly. To overcome test operation difficulties in practical application which is caused by the direct scheme of inverse substructuring of the mechanical assembly coupling dynamic stiffness, it needs to discrete the non-ideal mechanical assembly connection interface including linear and planar connection interface so as to apply two kinds of indirect method of inverse substructuring analysis based on frequency response function (FRF) spectrum to recognize its coupling dynamic stiffness. The experimental models of mechanical assembly for the more practical linear and planar connections are designed, and the practicability of applying these two methods to recognize the dynamic stiffness after assembly coupled is verified

The dynamic predictive power of company comparative networks for stock sector performance

As economic integration and business connections increase, companies actively interact with each other in the market in cooperative or competitive relationships. To understand the market network structure with company relationships and to investigate the impacts of market network structure on stock sector performance, we propose the construct of a company comparative network based on public media data and sector interaction metrics based on the company network. All the market network structure metrics are integrated into a vector autoregression model with stock sector return and risk. Several findings demonstrate the dynamic relationships that exist between sector interactions and sector performance. First, sector interaction metrics constructed based on company networks are significant leading indicators of sector performance. Interestingly, the interactions between sectors have greater predictive power than those within sectors. Second, compared with the company closeness network, the company comparative network, which labels the cooperative or competitive relationships between companies, is a better construct to understand and predict sector interactions and performance. Third, competitive company interactions between sectors impact sector performance in a slower manner than cooperative company interactions. The findings enrich financial studies regarding asset pricing by providing additional explanations of company/sector interactions and insights into company management using industry-level strategies

Experimental verification on applying indirect inverse substructuring analysis to identify coupling dynamic stiffness of mechanical assembly via planar surface

To broaden the engineering application of inverse substructuring analysis, the mechanical assembly via planar surface is experimentally studied. Specifically, the first and the second schemes of indirect inverse substructuring analysis are applied to identify the coupling dynamic stiffness of the assembly. The experimental model of the assembly is designed, and the surface is then discretized equivalently into point-to-point connections for testing the frequency response functions (FRFs) involved in the schemes. Experimental results show that, applying both of the schemes are feasible for the identification, and the identified stiffnesses approach to be stable as the number of discretized points increases

Coupling dynamic stiffness identification of mechanical assembly with linear connection by the second indirect scheme of inverse substructuring analysis

A non-ideal connection of mechanical assembly with linear assembling interface is firstly considered in the coupling dynamic stiffness identification by applying the second scheme of indirect inverse substructuring analysis. The experimental model of the mechanical assembly is designed, and the interface is then discretized equivalently as ideal point-coupling for testing the frequency response functions (FRFs) involved in the scheme. As the results of the experimental study, applying the scheme is verified to be feasible for the stiffness identification of a mechanical assembly with linear connection, and the identified stiffness approaches to be stable with increase of the number of discretized points

Molecular Beam Epitaxy Growth of Superconducting LiFeAs Film on SrTiO3(001) Substrate

The stoichiometric "111" iron-based superconductor, LiFeAs, has attacted great research interest in recent years. For the first time, we have successfully grown LiFeAs thin film by molecular beam epitaxy (MBE) on SrTiO3(001) substrate, and studied the interfacial growth behavior by reflection high energy electron diffraction (RHEED) and low-temperature scanning tunneling microscope (LT-STM). The effects of substrate temperature and Li/Fe flux ratio were investigated. Uniform LiFeAs film as thin as 3 quintuple-layer (QL) is formed. Superconducting gap appears in LiFeAs films thicker than 4 QL at 4.7 K. When the film is thicker than 13 QL, the superconducting gap determined by the distance between coherence peaks is about 7 meV, close to the value of bulk material. The ex situ transport measurement of thick LiFeAs film shows a sharp superconducting transition around 16 K. The upper critical field, Hc2(0)=13.0 T, is estimated from the temperature dependent magnetoresistance. The precise thickness and quality control of LiFeAs film paves the road of growing similar ultrathin iron arsenide films.Comment: 7 pages, 6 figure

Coupling dynamic stiffness identification of mechanical assembly with linear and planar connection by the indirect scheme of inverse substructuring analysis

Mechanical assembly is an important process in manufacturing electromechanical products and it directly affects the dynamic quality of a whole product. The traditional inspection and analysis of mechanical assembly quality mainly focuses on the “static quality”, such as the shape accuracy and dimensional coordination, while ignoring its “dynamic quality”, which is incomplete estimation on the assembly quality. Meanwhile, the assembly coupling dynamic stiffness is a key determinant of the dynamic quality of mechanical assembly. To overcome test operation difficulties in practical application which is caused by the direct scheme of inverse substructuring of the mechanical assembly coupling dynamic stiffness, it needs to discrete the non-ideal mechanical assembly connection interface including linear and planar connection interface so as to apply two kinds of indirect method of inverse substructuring analysis based on frequency response function (FRF) spectrum to recognize its coupling dynamic stiffness. The experimental models of mechanical assembly for the more practical linear and planar connections are designed, and the practicability of applying these two methods to recognize the dynamic stiffness after assembly coupled is verified