Single-machine scheduling with preventive periodic maintenance and resumable jobs in remanufacturing system

A single-machine scheduling with preventive periodic maintenance activities in a remanufacturing system including resumable and non-resumable jobs is studied.The objective is to find a schedule to minimize the makespan and an LPT-LS algorithm is proposed.Non-resumable jobs are first scheduled in a machine by the longest processing time（LPT） rule,and then resumable jobs are scheduled by the list scheduling（LS） rule.And the worst-case ratios of this algorithm in three different cases in terms of the value of the total processing time of the resumable jobs（denoted as S2） are discussed.When S2 is longer than the spare time of the machine after the non-resumable jobs are assigned by the LPT rule,it is equal to 1.When S2 falls in between the spare time of the machine by the LPT rule and the optimal schedule rule,it is less than 2.When S2 is less than the spare time of the machine by the optimal schedule rule,it is less than 2.Finally,numerical examples are presented for verification.

On Problems of Multicomponent System Maintenance Modelling

We present an overview of some recent developments in the area of mathematical modeling of maintenance decisions for multi-unit systems. The emphasis is on three main groups of multicomponent maintenance optimization models： the block replacement models, group maintenance models, and opportunistic maintenance models. Moreover, an example of a two-unit system maintenance process is provided in order to compare various maintenance policies.

Patent portfolio analysis model based on legal status information

Purpose:This research proposes a patent portfolio analysis model based on the legal status information to chart out a competitive landscape in a particular field,enabling organizations to position themselves within the overall technology landscape.Design/methodology/approach:Three indicators were selected for the proposed model:Patent grant rate,valid patents rate and patent maintenance period.The model uses legal status information to perform a qualitative evaluation of relative values of the individual patents,countries or regions’ technological capabilities and competitiveness of patent applicants.The results are visualized by a four-quadrant bubble chart To test the effectiveness of the model,it is used to present a competitive landscape in the lithium ion battery field.Findings:The model can be used to evaluate the values of the individual patents,highlight countries or regions’ positions in the field,and rank the competitiveness of patent applicants in the field.Research limitations:The model currently takes into consideration only three legal status indicators.It is actually feasible to introduce more indicators such as the reason for invalid patents and the distribution of patent maintenance time and associate them with those in the proposed model.Practical implications:Analysis of legal status information in combination of patent application information can help an organization to spot gaps in its patent claim coverage,as well as evaluate patent quality and maintenance situation of its granted patents.The study results can be used to support technology assessment,technology innovation and intellectual property management.Originality/value:Prior studies attempted to assess patent quality or competitiveness by using either single patent legal status indicator or comparative analysis of the impacts of each indicator.However,they are insufficient in presenting the combined effects of the evaluation indicators.Using our model,it appears possible to get a more complete and objective picture of the current competitive situation.

Periodic Preventive Maintenance Policy with Infinite Time and Limit of Reliability Based on Health Index

The aging of machine can be slowed and the life of machine can be increased by implementing periodic predictive maintenance. In this article,an improvement factor considering maintenance cost,age of machine and learning effect in the process of maintaining is constructed to describe the effect of periodic preventive maintenance. The model of improvement factor can be fitted through health index. Based on improvement factor with infinite time,cost function including preventive maintenance cost,minimal repair cost and replacement cost is explored. The unit cost and the optimized maintenance time interval based on limit of reliability are deduced. The process of optimization and an example are given.