Quality Inspection Plan for Imperfect Production System with Assembly Configuration

In this study, the model concerning a negative binomial sampling inspection plan is proposed and applied to an imperfect production system with assemble-to-order configuration, where the production system is subject to a Weibull deteriorating process and is operated under an in-control or an out-of-control state. The proposed model of this study contributes to developing an approach which can effectively integrate the considerations of the production system status, the defective rate, the working efficiency of employees, and the market demands with an aim to determine the optimal number of conforming items for inspection with minimum total cost, and the results can be practically applied to the assembly of products in various industries, especially for the prevalent Industry 4.0 in manufacturing.

Lifetime Estimation for Multi-Phase Deteriorating Process with Random Abrupt Jumps

Owing to operating condition changing, physical mutation, and sudden shocks, degradation trajectories usually exhibit multi-phase features, and the abrupt jump often appears at the changing time, which makes the traditional methods of lifetime estimation unavailable. In this paper, we mainly focus on how to estimate the lifetime of the multi-phase degradation process with abrupt jumps at the change points under the concept of the first passage time (FPT). Firstly, a multi-phase degradation model with jumps based on the Wiener process is formulated to describe the multi-phase degradation pattern. Then, we attain the lifetime’s closed-form expression for the two-phase model with fixed jump relying on the distribution of the degradation state at the change point. Furthermore, we continue to investigate the lifetime estimation of the degradation process with random effect caused by unit-to-unit variability and the multi-phase degradation process. We extend the results of the two-phase case with fixed parameters to these two cases. For better implementation, a model identification method with off-line and on-line parts based on Expectation Maximization (EM) algorithm and Bayesian rule is proposed. Finally, a numerical case study and a practical example of gyro are provided for illustration.

Influence of Frost Damage on Chloride Penetration into Concrete

In most national and international codes for durability design, service life is estimated after selection of one single and dominant deteriorating process such as carbonation, chloride penetration or frost attack. Application of existing codes has shown, however, that the predicted service life is not reached in practice in most cases. Early damage occurs and as a consequence expensive repair measures become frequently necessary, long before the design service life is reached. One reason for this discrepancy is certainly the fact that in practice each dominant deteriorating process is usually accompanied by other aggravating processes. In this contribution capillary absorption of different types of concrete is studied first. The influence of an increasing number of freeze-thaw cycles on capillary absorption of water is studied first, then chloride penetration before and after exposure to a certain number of freeze-thaw cycles was determined experimentally. It was found that an increasing number of freeze-thaw cycles increases chloride penetration significantly, and hence reduces service life in aggressive environment. It can be concluded that for realistic service life prediction the interaction between frost damage and chloride penetration has to be taken into consideration in regions with low temperatures.

Defective actin dynamics in dendritic spines: cause or consequence of age-induced cognitive decline?

Ageing is a complex deteriorating process that coincides with changes in metabolism, replicative senescence, increased resistance to apoptosis, as well as progressive mitochondria dysfunction that lead to an increase production and accumulation of reactive oxygen species (ROS). Although controversy on the paradigm of the oxidative damage theory of ageing exists, persuasive studies in Caenorhabditis elegans and yeast have demonstrated that manipulation of ROS can modify the process of ageing and influences the damage of proteins, lipids and DNA. In neurons, ageing impacts on the intrinsic neuronal excitability, it decreases the size of neuronal soma and induces the loss of dendrites and dendritic spines. The actin cytoskeleton is an abundant and broadly expressed system that plays critical functions in many cellular processes ranging from cell motility to controlling cell shape and polarity. It is thus hardly surprising that the expression and the function of actin in neurons is crucial for the morphological changes that occur in the brain throughout life. We propose that alterations in actin filament dynamics in dendritic spines may be one of the key events contributing to the initial phases of ageing in the brain.

Maximizing the Percentage of On-Time Jobs with Sequence Dependent Deteriorating Process Times

The paper addresses the problem of maximizing the percentage of on-time jobs in a parallel machine environment with sequence dependent deterioration. The deterioration of each machine (and therefore of the job processing times) is a function of the sequence of jobs that have been processed by the machine. Two machine loading strategies are combined with a set of list scheduling algorithms to solve the identical and unrelated machine versions of the problem. The proposed solutions approaches are tested using a large set of problem instances that consider various levels of the number of jobs and machines, the due date tightness, and the deterioration effect. The results indicate that the approach based on loading considering all machines simultaneously and assigns jobs by due date is the most effective.

Research of the Multi-State Deteriorating System Failure Based on RPN and the Multi-Granularity Linguistic System

Traditional FMEA lacks systematicness. A new approach of multi-state deteriorating system failure assessment is proposed base on the risk priority number (RPN) and multi-granularity linguistic information system. With this method, the key links and parameters of system deteriorating process is clear, and fault evolution analysis is more comprehensive. Policy iteration algorithm is introduced to calculate the optimal maintenance strategy under different fault conditions. Finally, numerical examples illustrate the failure analysis process; the results show that the new approach is efficient and practical.