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Retinal pigment epithelium (RPE) dysfunction, manifested as drusen formation and RPE mottling, is a characteristic lesion of aging. The mechanism of RPE dysfunction remains unknown. Previous animal studies have proven that the activation of NLRP3 inflammasome in RPE leads to apoptosis and pyroptosis, which may play a very important role in the development of age-related macular degeneration (AMD). However, there is a lack of clinical evidence to support the above hypothesis. Herein, we report a 38-year-old Chinese Han woman who had NLRP3-associated autoinflammatory disease (NLRP3-AID) with widely scattered drusen at the posterior pole in both eyes. NLRP3-AID is a rare disease caused by mutations of the NLRP3 gene, leading to NLRP3 inflammasome activation. This report of early-onset drusen provides clinical evidence that the NLRP3 inflammasome might contribute to the occurrence of RPE dysfunction and is a potential cause of age-related macular degeneration (AMD). [ABSTRACT FROM AUTHOR]

Nowadays selecting the most suitable robot is a difficult task for manufacturing firms due to increase in production demands and availability of various robot models. Robot evaluation and selection can be regarded as a multiple criteria decision-making (MCDM) problem and three key issues are the assessment of robots, the determination of criteria weights and the prioritisation of alternatives. This paper aims to propose an integrated model based on hesitant 2-tuple linguistic term sets and an extended QUALIFLEX approach for handling robot selection problems with incomplete weight information. The new model can not only manage uncertain and imprecise assessment information of decision-makers with the aid of hesitant 2-tuple linguistic term sets, but also derive the important weights of criteria objectively when the weight information is incompletely known. Moreover, based on the extended QUALIFLEX algorithm, the priority orders of robots can be clearly determined and a more reasonable and credible solution can be yielded in a particular industrial application. Finally, a robot selection case study is carried out, and comparative experiments indicate the practicality and effectiveness of the proposed integrated linguistic MCDM approach. [ABSTRACT FROM PUBLISHER]

It is always difficult to discuss the analytical formulas, in which optimum solutions of replacement policies satisfy, due to the mathematical complexity. This paper proposes several approximate calculations for age-based random replacement policies, such that the unit is replaced at time T, at random time Y j (j = 1 , 2 , ...) over time T, and at random time YN for Y j (j = 1 , 2 , ... , N). We use the inequality properties of the formulas and the bounds of the extended failure rate functions to find the approximate calculations of replacement times in analytical ways. It is shown from numerical examples that these approximate calculations would become useful references for the optimum age-based random replacement times. [ABSTRACT FROM AUTHOR]

When we consider the improvement of the functional performances that are released by the new updates of the products, it is an interesting problem to revisit the existing replacement policies. For such a viewpoint, four replacement models with product update announcements, i.e., PUA for abbreviation, are given in this paper: Model 1, the unit is replaced at time T or at PUA over time T. Model 2, the unit is replaced at the Kth failure or at PUA over the Kth failure. By considering both time T and failure K, Models 3 and 4 are obtained based on the approaches of replacement first and last. We obtain the expected cost rates for four models and discuss analytically their optimal replacement policies Further, numerical examples are given when the time for PUA has an exponential distribution. [ABSTRACT FROM AUTHOR]

It has been modeled for several replacement policies in literatures that the whole life cycle or operating interval of an operating unit should be finite rather than infinite as is done with the traditional method. However, it is more natural to consider the case in which the finite life cycle is a fluctuated parameter that could be used to estimate replacement times, which will be taken up in this article. For this, we first formulate a general model in which the unit is replaced at random ageU, random timeYfor the first working number, random life cycleS, or at failureX, whichever occurs first. The following models included in the general model, such that replacement done at ageTwhen variableUis a degenerate distribution, and replacement done at working numbersNsummed by numberNof variableY, are optimized. We obtain the total expected cost until replacement and the expected replacement cost rate for each model. Optimal ageT, working numberN, and a pair of (T,N) are discussed analytically and computed numerically. [ABSTRACT FROM AUTHOR]

The tribopairs of water hydraulic plunger pumps are usually operated under severe conditions, due to the poor lubrication of water and silt suspended in natural water. It is essential to identify the desired engineering materials and material combinations for designing water pumps. As the candidate materials of tribopairs, the tribological characteristics of different Al2O3-TiO2 coatings combined with Si3N4 ceramics under silt-laden water and tap water lubrication were investigated. The Al2O3-TiO2 coatings with different weight percentages of TiO2 in a wide range from 3 to 100% were tested. The tribological characteristics of the various couple pairs were researched using a ring-on-ring test rig. The microstructures of the contact surfaces were analyzed with a scanning electron microscope before and after the test to study the wear mechanism. The experimental results indicate that the friction coefficient of the Al2O3-TiO2/Si3N4 tribopairs increases with an increase in the percentage of TiO2 content in the Al2O3-TiO2 coating. However, the TiO2 content does not present a clear relationship with the wear rate. Considering the friction and wear properties, Al2O3-13%TiO2 is the preferred coating to use in water hydraulic pumps when sliding against Si3N4. [ABSTRACT FROM AUTHOR]

It has been assumed for a standby unit that periodic inspection is performed more easily to detect failures, but such a strict periodic mode would be impractical if the unit is executing some procedures without stops. From the above viewpoint, this paper first optimises a random inspection policy in accordance with random procedure times, compares it with periodic inspection and computes a modified checking cost for random inspection to determine the case where such a random inspection would be adopted. Second, this paper proposes three new inspection models in which inspections with deterministic policies are scheduled strategically while their performances need to be limited by completion times of operation procedures. These policies are called inspection first, inspection last and inspection overtime. The total expected inspection and downtime costs of each model until failure detection are obtained, and optimal policies which minimise them are derived analytically. Furthermore, the three inspection policies are compared with periodic inspection, inspection first and last are compared with each other, and a modified checking cost for inspection overtime is discussed when the policy would be better than periodic inspection. [ABSTRACT FROM AUTHOR]

In some practical situations, it may be more economical to work a used system than do a new one. From this viewpoint, this article considers three basic preventive maintenance (PM) policies for a used system: the system with initial variable damage Y 0 begins to operate at time 0, and suffers damage due to shocks. It fails when the total damage exceeds a failure level K and corrective maintenance is made immediately. To prevent such failure, it undergoes PM at a planned time T, a shock number N and a damage level k, but maintenances are imperfect. However, failure rate of a used system maybe higher than that of a new one, so some maintenance is applied to the policies at each shock in the extended models. Using the theory of cumulative processes, expected cost rate models are obtained, optimal policies which minimise them are derived analytically and discussed numerically. [ABSTRACT FROM PUBLISHER]

This article considers an extended parallel system with cascading failure: Compared with the conventional parallel system with independent failure, the factor that cascading failure could reduce the reliability of the system due to redistribution of the workload. Reliability measures of the system are derived, using the theory of stochastic processes. To counteract the impact of cascading failure, a preventive maintenance policy is proposed. Further, this is applied to a dual active system. An optimal maintenance policy which minimizes the expected cost rate is derived. Finally, a numerical example is given and some discussions are made. [ABSTRACT FROM AUTHOR]