A Novel Method for Acquiring Engineering-Oriented Operational Empirical Knowledge

The operational knowledge of skilled technicians gained from years of experience is invaluable for an enterprise. Possession of such knowledge will facilitate an enterprise sharing technician’s know-how and training of new employees effectively. However, until now there is rare efficient quantitative method to obtain this kind of tacit knowledge. In this paper we propose a concept of engineering-oriented operational empirical knowledge (OEK) to describe this kind of knowledge and design a framework to acquire OEK from skilled technician’s operations. The framework integrates motion analysis, motion elicitation, and intent analysis. The modular arrangement of predetermined time standards (MODAPTS) is used to divide the technician’s operational process into basic motion elements; and the variable precision rough set (VPRS) algorithm is used to extract the technician’s OEK content, which combined with the technician’s intent elicited via interview; the completed OEK is obtained. At the end of our study, an engineering case is used to validate the feasibility of the proposed method, which shows that satisfactory results have been reached for the study

Gut Microbial Compositions in Four Age Groups of Tibetan Minipigs

In this study, the gut microbiota was characterized in four age strata of Tibetan minipigs. Results indicated that the fecal bacteria of 7-, 28-, 56-, and 180-day-old minipigs did not significantly differ in terms of phylogenetic diversity (i.e., PD whole tree) or the Shannon index (both, p > 0.05). Findings of a principal coordinate analysis demonstrated that fecal bacteria of 180-day-old minipigs were discernable from those of the other three age groups. From ages seven to 56 days, the abundance of Bacteroidetes or Firmicutes appeared to vary. Regarding genera, the populations of Bacteroides and Akkermansia decreased with increasing age

An Opportunistic Maintenance Policy of Multi-unit Series Production System with Consideration of Imperfect Maintenance

Abstract: This paper proposes an opportunistic maintenance policy for the multi-unit series production system. This proposed maintenance policy is on the basis of the failure rate analysis, which is more realistic than age-based or time-based opportunistic replacement models. When a system halts for performing preventive maintenance or opportunistic maintenance, the alternative decision of replacement and repair is made by economic evaluation of these two types of maintenance actions. The optimal preventive maintenance plans in a finite time horizon can be obtained by adjusting the preventive maintenance threshold and opportunistic maintenance threshold. A numerical example is given for illustrating the applications of the proposed policy

Tristage Bargaining Dynamic Game-Based Preventive Maintenance for Electric Multiple Unit

The operation and maintenance sectors of electric multiple unit (EMU) are considered as game participants to optimize the preventive maintenance (PM) schedule of EMU components. The total cost of a component over a life cycle includes failure risk and maintenance cost. The failure risk of EMU components is assessed quantitatively by using an analytic hierarchy process and scoring and weighting the factors that affect the failure risk of such components. The operation sector expects failure risk to be minimized, whereas the maintenance sector expects maintenance costs to be low, and their interests interfere with each other to some extent. This study establishes a tristage bargaining dynamic game model of the operation sector priority bid and maintenance sector priority bid considering the PM reliability threshold R as the bargaining object. A numerical example demonstrates that the result is more beneficial to the sector that bids first, and the operation priority bid allows the component to maintain a higher reliability level over a life cycle, especially in the latter half of the component life cycle

Integrated operation and maintenance optimization for high-speed train fleets considering passenger flow

A joint optimization model of maintenance and operation of high-speed train fleets is established with the optimization objective of minimizing the total costs, considering dynamic passenger flow and maintenance resources. A new maintenance strategy CCPM (Coordinating Conflicts Preventive Maintenance) is proposed to optimize the problem. The effectiveness of the model and the strategy are verified by numerical examples. The comparison between the strategy in the paper and the existing approach proves that the new strategy is more effective and shows the importance of considering dynamic passenger flow. The model and the strategy provide decision support for the actual high-speed trains operation and maintenance program. This study also offers new ideas to the subsequent research on preventive maintenance of high-speed trains

Pressure thresholds of the human foot: measurement reliability and effects of stimulus characteristics

Information related to reliable values of discomfort thresholds can help to improve the designs of various products. This study aimed to investigate the measurement reliabilities associated with pressure thresholds, while determining the effects of stimulus characteristics (stimulus area, indentation speed) of the human foot. An indentation apparatus was used with four sizes of indentation probes and three indentation speeds. In total, 13 locations on the right foot of 10 male and 10 female participants were tested to determine the pressure discomfort thresholds (PDT) and pressure pain thresholds (PPT). Results show that the tests had very good measurement reliability with intra-class correlations (ICC) greater than 0.8 for the PPT measurements and acceptable reliability (most ICC > 0.75, with a few between 0.5 and 0.75) for the PDT measurements, demonstrating that participants are capable of judging their pain and discomfort thresholds. Pressure sensitivity differs across locations of the foot, with the medial plantar arch of the foot being the most sensitive, followed by the dorsal surface of the foot. The heel area was the least sensitive. PPT and PDT are dependent on the stimulus characteristics of the area and the speed of indentation. A smaller area has a higher PPT and PDT, indicating significant effects of spatial summation. The increase of PDT and PPT at higher speeds may be partially explained by the increase in stiffness because foot tissue exhibits viscoelastic properties. The findings can have a significant impact on the design of footwear and other accessories for improved foot health and comfort. Statement of Relevance: This study investigated the threshold measurement reliability while determining the pressure sensitivity on the surface of the foot with varying stimulus characteristics. The findings may be very useful in the design of footwear and other accessories for improved comfort and reduced injuries.close

A CAD system for shoe last customization

Customized shoes are desired in shoe industries nowadays to satisfy customer needs on style, fit and comfort. This paper proposes a CAD system for designing the customized shoe last based on the customer preferred shoe style and his/her foot features. Eighteen important foot features are firstly extracted from the laser-scanned foot data. The features are then used to deform the base shoe last of the customer preferred style to the customized shoe last with better fit to the customer's foot, while maximally maintaining the customer preferred style. Finally, the fit between the customer's foot and the customized shoe last is evaluated through a color-coded map