Slack Due-Window Assignment Scheduling Problem with Deterioration Effects and a Deteriorating Maintenance Activity

This paper studies the slack due-window assignment scheduling problem with deterioration effects and a deterioration maintenance activity on a single-machine. The machine deteriorates during the machining process, and at a certain moment performs a deterioration maintenance activity, that is, the duration time of the maintenance activity is a linear function of the maintenance starting time. It is needed to make a decision on when to schedule the deteriorating maintenance activity, the optimal common flow allowances and the sequence of jobs to minimize the weighted penalties for the sum of earliness and tardiness, weighted number of early and delayed, and weighted due-window starting time and size. This paper proposes a polynomial time algorithm to solve this problem.

Railway Infrastructure Asset Management Modelling

Railway infrastructure comprises a large collection of diverse and complex systems and structures. Many of them are aging assets and require a significant budget to deliver the maintenance to ensure the required safety and service performance standards. With such a large amount of money spent each year to maintain and renew the network assets, small percentage savings can amount to substantial sums of money. There is therefore a huge incentive to better understand the degradation that assets experience and how these can be effectively managed through the implementation of efficient maintenance strategies. Track and bridges are the most expensive assets to keep in the required condition, and this chapter provides a method to analyse their degradation and build Petri net models to predict the future state of the asset, the number of each maintenance activity which are expected to be undertaken, and their costs experienced by following a particular strategy. Utilising these models enables the quality of the asset management decisions made to be improved and optimised.

Foraging and nest maintenance activity of the leafcutter ant Acromyrmex lobicornis (Hymenoptera: Formicidae) in an organic vineyard in the Monte desert of Mendoza, Argentina

Exclusive to the Neotropical region, leaf cutter ants are considered agricultural pests, although they can also have a positive effect on plants. In Mendoza vineyards, vegetal biodiversity is minimal, therefore they cut off this plant as a feeding resource. Acromyrmex lobicornis Emery it is mostly nocturnal and forages according to temperature. Foraging and maintenance activity was measured monthly in 14 colonies, throughout a full day at fourhour intervals, from October 2019 to March 2020. Acromyrmex lobicornis showed different seasonal patterns of foraging activity. Foraging intensity was highest throughout January and February, intermediate during December, and lowest in October and November. A bimodal feeding pattern was observed, foraging both day and night avoiding the hottest hours. The maximum collection of fragments was observed in the range of 10 and 19 °C, less between 20 - 39 °C, minimum between 40 - 49 °C and null between 0 - 9 °C. The nest - maintenance activity was maximum between 20 - 29 °C, less between 30 - 39 ° C, minimum between 40 - 49 °C and null between 0 - 20 °C.

Creation of a knowledge management model based on CBR

This paper proposes a solution to facilitate maintenance activities associated with stand-alone solar photovoltaic installations in our developing countries. The autonomous photovoltaic solar installation is not connected to the electricity distribution grid. It meets the electricity needs on the one hand, of those who are too far away and who do not have access to the distribution grid. On the other hand, those who wish to overcome the constraints of connection to the electrical distribution grid. Our work focuses on the capitalization of knowledge in maintenance activity. The goal is to propose a model capable of helping maintenance technicians during their interventions by providing them with knowledge elements that will be drawn from a knowledge base. This knowledge base is built from the knowledge collected during previous maintenance activities in a given solar photovoltaic installation.

Results of Parallel-Machine Scheduling Model with Maintenance Activity considering Time-Dependent Deterioration, Delivery Times, and Resource Allocation

This paper investigates parallel-machine scheduling models with maintenance activity, delivery times, time-dependent deterioration, and resource allocation. We consider two forms of the problem: the first is to minimize the sum of total completion times, total machine loads, the total absolute deviation of job completion times, and the total resource allocation; the second is to minimize the sum of total waiting times, total machine loads, the total absolute deviation of job waiting times, and the total resource allocation. The problems are proved to be solvable in polynomial time.

Addressing the Issues of Maintenance Management in SMEs: Towards Sustainable and Lean Maintenance Approach

This paper outlines on the preliminary outcomes of pilot project aimed at exploring the issue related to managing of maintenance activity in the Malaysian Small and Medium Enterprises (SMEs). SMEs have been accepted as vital components of domestic industry development in many countries. However, the literature portrays that many of Malaysian SMEs particularly the companies involved in manufacturing, fabrication and machining services are struggling to manage the maintenance of their manufacturing equipment. Dependable manufacturing equipment is important factor towards organizational profitability. Managing the maintenance activity of those manufacturing equipment nowadays, is becoming more challenging due to automation and computerization. Due to such issues, SMEs companies are under stiff pressure to minimize lost time for their survival. Thus, this study seeks to explore the related issues towards further improvements. Qualitative research methodology was adopted in the study. Data were collected at eight (8) SMEs located in three (3) different areas, namely southern, central and eastern region of peninsular Malaysia. Information was gathered from semi-structured interviews with SMEs management and observations focuses on different areas of maintenance management at the respective SMEs. The main concern is to validate the critical success factors (CSFs) in managing the maintenance activity at selected SMEs. This study discovered that nine (9) CSFs are having the most significant impact towards improving the maintenance management practice for SMEs. These include: understanding the MM philosophy; management commitment and leadership; maintenance strategy; maintenance planning; maintenance training; monitoring and assessment; appropriate number of maintenance staff; integration of tools, techniques and technology, and; record of maintenance data. All those CSFs construct are integrated in a simple yet self-explanatory MM Framework to convey the conceptual idea of MM implementation program to the management and technical people within SMEs. It is believed that the MM Framework developed would serve as an indicator of company’s MM focus level. Through the identification of the CSFs constructs, the SMEs can utilize the information to improve their approach in systematic MM program. The discovered CSFs are vital for all stakeholders that directly or indirectly involve in managing the maintenance activity in SMEs. Doi: 10.28991/esj-2021-01283 Full Text: PDF

Propose a Polynomial Time Algorithm for Total Completion Time Objective

In this study, we integrate deteriorate jobs with repair&maintenance activity on a single machine scheduling subject to total completion time. This work has more than one motivation. First, jobs are assigned to machines in an automated production line. Later, to schedule the maintenance activities, if needed, to prevent machinery from breaking down later. There are some important mathematical models to solve this combination. However, due to the complexity of the problem which is Np-hard, a polynomial algorithm should be needed for solving large problems. Therefore, this article introduces several polnomial algorithms to determine the order of things best. With using these algorithms, it will be possible to determine where to assign to the schedule, taking into account the number of maintenance activities required and their optimum total completion time.

Influence of height on endothelial maintenance activity: a narrative review

Recent studies have revealed an inverse association between height and cardiovascular disease. However, the background mechanism of this association has not yet been clarified. Height has also been reported to be positively associated with cancer. Therefore, well-known cardiovascular risk factors, such as increased oxidative stress and chronic inflammation, are not the best explanations for this inverse association because these risk factors are also related to cancer. However, impaired blood flow is the main pathological problem in cardiovascular disease, while glowing feeding vessels (angiogenesis) are the main characteristic of cancer pathologies. Therefore, endothelial maintenance activity, especially for the productivity of hematopoietic stem cells such as CD34-positive cells, could be associated with the height of an individual because this cell contributes not only to the progression of atherosclerosis but also to the development of angiogenesis. In addition, recent studies have also revealed a close connection between bone marrow activity and endothelial maintenance; bone marrow-derived hematopoietic stem cells contribute towards endothelial maintenance. Since the absolute volume of bone marrow is positively associated with height, height could influence endothelial maintenance activity. Based on these hypotheses, we performed several studies. The aim of this review is not only to discuss the association between height and bone marrow activity, but also to describe the potential mechanism underlying endothelial maintenance. In addition, this review also aims to explain some of the reasons that implicate hypertension as a major risk factor for stroke among the Japanese population. The review also aims to clarify the anthropological reasons behind the high risk of atherosclerosis progression in Japanese individuals with acquired genetic characteristics.