Classical Series Model Research Articles

Heterogeneous filler distribution in polymeric capacitor films: An efficient route to improve their dielectric properties

High dielectric constant filler is often used to improve the dielectric properties of polymer. Most studies are focused on the uniform filler dispersion and interface between filler and polymer. Herein, multi-layered films containing BaTiO3 and multi-wall carbon nanotubes (MWCNTs) as fillers, with different filler distributions were designed and prepared, including alternating distribution of layers with/without filler; core-shell distribution with filler concentrated at core or shell; and uniform distribution. The overall filler content in these films was kept constant. These films have almost the same dielectric loss. Interestingly, it was noted that the largest dielectric constant is achieved for sample with filler concentrated at the shell (around 50% higher than the rest at low frequency). Interfacial polarization and filler localization are thought to play important role. However, classic Series model does not take these issues into account. To understand this, a modified Series model was proposed to calculate the dielectric constant of multi-layered films by considering these issues. Such equation is much more accurate at describing experimental results from current study as well as some published literature than classic Series model. Our work demonstrates the importance of hierarchical structure in polymer composites for dielectric property and heterogeneous distribution of filler could be much better than uniform distribution.

System-Reliability Evaluation Based on Series Chain Model under Exponential Distribution

In the general reliability analysis of series systems, the components which compose the system are assumed independent of each other. However, for most mechanical series systems, dependent failure is their common feature. If neglecting dependent failures where CCF(Common Cause Failure) plays an important role, it will lead to considerable errors or even misleading conclusions. In this article, the concept of series chain model is put forward in consideration of the CCF. By using the load—strength interference model, the order statistic theory and the knowledge of statistical distribution, the author develops a specific method to evaluate the reliability of series systems under exponential distribution. In the last part, by using Monte Carlo simulation, a group of specific data are given to verify the series chain model and compare the two different series system model. The results show that the reliability calculation under the classic series model is relatively conservative, while the reliability calculation under the series chain model is convincing. And thus, the series chain model is more applicable in engineering.