Performance deterioration modeling and optimal preventive maintenance strategy under scheduled servicing subject to mission time

AbstractServicing is applied periodically in practice with the aim of restoring the system state and prolonging the lifetime. It is generally seen as an imperfect maintenance action which has a chief influence on the maintenance strategy. In order to model the maintenance effect of servicing, this study analyzes the deterioration characteristics of system under scheduled servicing. And then the deterioration model is established from the failure mechanism by compound Poisson process. On the basis of the system damage value and failure mechanism, the failure rate refresh factor is proposed to describe the maintenance effect of servicing. A maintenance strategy is developed which combines the benefits of scheduled servicing and preventive maintenance. Then the optimization model is given to determine the optimal servicing period and preventive maintenance time, with an objective to minimize the system expected life-cycle cost per unit time and a constraint on system survival probability for the duration of mission time. Subject to mission time, it can control the ability of accomplishing the mission at any time so as to ensure the high dependability. An example of water pump rotor relating to scheduled servicing is introduced to illustrate the failure rate refresh factor and the proposed maintenance strategy. Compared with traditional methods, the numerical results show that the failure rate refresh factor can describe the maintenance effect of servicing more intuitively and objectively. It also demonstrates that this maintenance strategy can prolong the lifetime, reduce the total lifetime maintenance cost and guarantee the dependability of system

Research on modular analysis and evaluation method of ship repair cost

Based on the idea of modular design of ship, the ship modular method is used to study the target cost of ship repair, and a modular decomposition and analysis method of ship repair cost is proposed to decompose the ship repair project into relatively independent sub-modules, standardizes the repair scope of sub modules, determines the repair cost standard of sub-modules, and accumulates the repair cost of corresponding sub-modules. At the same time, from the perspective of cost control, cost risks are identified, and the fuzzy analytic hierarchy process is applied to analyze and evaluate risk factors to lay the foundation for cost adjustment and cost reduction risks

USP2a Supports Metastasis by Tuning TGF-beta Signaling

TGF-beta has been demonstrated to promote tumor metastasis, and the regulatory mechanisms are poorly understood. Here, we report the role of USP2a in promoting metastasis by facilitating TGF-beta-triggered signaling. USP2a interacts with TGFBR1 and TGFBR2 upon TGF-beta stimulation and removes K33-linked polyubiquitin chains from Lys502 of TGFBR1, promoting the recruitment of SMAD2/3. Simultaneously, TGFBR2 phosphorylates Ser207/Ser225 of USP2a, leading to the disassociation of SMAD2/3 from TGFBR1. The phosphorylation of USP2a and SMAD2 is positively correlated in human tumor biopsies, and USP2a is hyper-phosphorylated in lung adenocarcinomas with lymph node invasion. Depletion or pharmacologic inhibition of USP2a dampens TGF-beta-triggered signaling and metastasis. Our findings have characterized an essential role of USP2a as a potential target for treatment of metastatic cancers