Maintenance Considerations Research Articles

Design for maintainability tool for nano-façade coating applications on high-rise facades in the tropics

PurposeThe self-cleaning properties of nanostructured titanium dioxide facade coatings are useful in Singapore's tropical climate. However, its potential maintenance issues need to be determined right at the design stage. The purpose of this paper is to highlight the development of the design for maintainability tool which is a multicriteria design decision score sheet that evaluates the maintainability potential of nano-facade coating applications on high-rise façades with concrete and stonemasonry finishes and curtain walls.Design/methodology/approachQuantitative methods (expert and practitioner surveys) are conducted in this research study. Analytic hierarchy process (AHP) and sensitivity analysis were used to develop a robust Design for Maintainability tool.FindingsSafety measures indicator received the highest weighted score by experts, while the maximizing performance, minimizing risk, minimizing negative environmental impact and minimizing consumption of matter and energy were the top ranking main criteria by both experts and practitioners. The top ranked design for maintainability sub-criteria identified by practitioners and experts were risk management, maintenance considerations, climatic conditions, safety measures, lifecycle cost and maintenance access, sun's path, rainfall intensity, biological growth measures and building age profile.Originality/valueMost researches on the maintainability of nano-façade coatings uses experimentation to test the durability of nano-façade coatings, while this study focuses on design based empirical data such as establishing and ranking the list of design for maintainability criteria or indicators to minimize future defects and maintenance issues. The design for maintainability tool contributes to the maintainability of nano-façade coatings leading to maximizing its performance while minimizing cost, risks, resource consumption and negative environmental impact.

Nonparametric bayes estimation of the reliability function of a coherent system

Complex coherent systems are the engines driving forward our technological world. A coherent system is composed of components, which could be modules or sub-systems, that interact with each other according to some structure function. For purposes of maintenance and safety considerations, it is of critical importance to gain knowledge of the distribution of the system lifetime, with this distribution being a function of the distributions of the components lifetimes. Since the monitoring of a system ceases upon system failure, at system failure some components will be failed, while others, depending on the structure function, will still be functioning with their lifetimes right-censored by the system lifetime. This paper deals with the estimation of the system lifetime distribution. The inferential framework is nonparametric Bayesian, with partition-based Dirichlet processes (PBDP) assigned as priors on the components lifetime distributions. PBDP are more general than the usual Dirichlet process (DP) priors and are particularly suited as priors in settings with censored data. The resulting estimator of the system life distribution, which is a function of the nonparametric Bayes estimators of the components lifetime distributions, is compared in terms of bias and variance with a product-limit type estimator proposed by Doss, et. al. (Ann. Statist., 1989), which can be obtained as a limit of the proposed estimator. These comparisons, which are facilitated through computer simulations, demonstrate that the proposed estimator possesses some robustness. The proposed estimator is illustrated using a synthetic data for a parallel system with five components.

WITHDRAWN: AI-based approaches for profitable investment and trading in stock market

Abstract One of the most widely discussed financial issues is artificial intelligence. More successful and efficient decisions can be learned and implemented by AI rather than routine and repetitive tasks. Investigations have shown that in some financial firms AI already dominates and outperforms people. The aim of the research was to find profitability in the trade and investment on the financial market from conventional against AI methods. On the basis of current work on the AI trading and investment business, the following questions are raised: what do AI trading benefits and disadvantages offer? In addition, how successful or risky is trading based on AI versus a conventional approach?, Budget and maintenance considerations. In this research, an online AI trading platform was introduced and TEDx was presented. In this analysis, AI's use in trade and investment as well as chaos and automation theories were used. Analysis of the above content reveals that it is time consuming for conventional trade methods to obtain and generate strategies by analysing them. Although it is costly to build an AI trading system, it can explore broad data and generate more and better results until, for instance, quickly pick-up stock. The findings showed that artificial knowledge has tremendous effects on trade and investment in financial markets. Although investing as an investor or as a small business is costly, at the same time, it has proved more lucrative for large finance companies. In different AI-based approaches, AI implementations are different depending on stocks and assets of different financial markets. Different timeframes and minor adjustments when the AI methods are scaled have different results; more study is therefore needed to define specific data trends on individual parts that may be more precise in terms of AI trade and investment performance.

Impact of Cycle Time and Payload of an Industrial Robot on Resource Efficiency

Modern industry benefits from the automation capabilities and flexibility of robots. Consequently, the performance depends on the individual task, robot and trajectory, while application periods of several years lead to a significant impact of the use phase on the resource efficiency. In this work, simulation models predicting a robot’s energy consumption are extended by an estimation of the reliability, enabling the consideration of maintenance to enhance the assessment of the application’s life cycle costs. Furthermore, a life cycle assessment yields the greenhouse gas emissions for the individual application. Potential benefits of the combination of motion simulation and cost analysis are highlighted by the application to an exemplary system. For the selected application, the consumed energy has a distinct impact on greenhouse gas emissions, while acquisition costs govern life cycle costs. Low cycle times result in reduced costs per workpiece, however, for short cycle times and higher payloads, the probability of required spare parts distinctly increases for two critical robotic joints. Hence, the analysis of energy consumption and reliability, in combination with maintenance, life cycle costing and life cycle assessment, can provide additional information to improve the resource efficiency.

Impact of Cycle Time and Payload of an Industrial Robot on Resource Efficiency

Modern industry benefits from the automation capabilities and flexibility of robots. Consequently, the performance depends on the individual task, robot and trajectory, while application periods of several years lead to a significant impact of the use phase on the resource efficiency. In this work, simulation models predicting a robot’s energy consumption are extended by an estimation of the reliability, enabling the consideration of maintenance to enhance the assessment of the application’s life cycle costs. Furthermore, a life cycle assessment yields the greenhouse gas emissions for the individual application. Potential benefits of the combination of motion simulation and cost analysis are highlighted by the application to an exemplary system. For the selected application, the consumed energy has a distinct impact on greenhouse gas emissions, while acquisition costs govern life cycle costs. Low cycle times result in reduced costs per workpiece, however, for short cycle times and higher payloads, the probability of required spare parts distinctly increases for two critical robotic joints. Hence, the analysis of energy consumption and reliability, in combination with maintenance, life cycle costing and life cycle assessment, can provide additional information to improve the resource efficiency.

Automated crack severity level detection and classification for ballastless track slab using deep convolutional neural network

The classification and treatment of cracks with different severity levels based on the width measurement is a critical consideration in maintenance of ballastless track slab. Existing deep learning methods cannot directly quantify cracks, which must rely on image processing technologies to post-process the initial results by deep learning, inevitably leading to multiple steps and low efficiency. This paper proposes a novel quantitative classification method for cracks with different severity levels based on deep convolutional neural networks, using orthogonal projection method to preprocess training data and define the severity level, which is validated and evaluated from four aspects: network structures, crack data, classification methods, and environmental conditions. Results show that the Inception-ResNet-v2 network can classify crack images into three severity levels without pixel segmentation or post-processing, achieving the accuracy, precision, recall and F1 score all exceeding 93%, with good robustness and adaptability to noise and light intensity.

Group maintenance optimization of subsea Xmas trees with stochastic dependency

Subsea Xmas trees (XTs) are vital equipment for offshore oil and gas development. Due to a long and continuous operation, components of XTs often become vulnerable subjected to degradation and unexpected failures. Due to the uncertainties of subsea operation and fault tolerance design, current maintenances on heterogeneous components, which are assumed to be independent of each other, perform separately. Only one PM mode (imperfect or perfect) is considered. However, these assumptions impede the application of state-of-the-art research results on the maintenance of this equipment. Therefore, for XTs with stochastic dependency, this study proposes a group maintenance optimization approach that combines maintenance activities to reduce maintenance costs. Reduction factors are introduced to measure the effects of various preventive maintenance (PM) actions, and the optimal component-level PM intervals can be obtained. An improved group strategy can be explored in consideration of stochastic dependency and opportunity maintenance. Utilizing the collaborative particle swarm optimization (CPSO) algorithm, the cost of an optimal group maintenance plan can be minimized while maintaining the availability. The uses and advantages of the proposed group maintenance approach are illustrated by a case study on a Horizon Xmas tree with a 14-component system.

Grading in Secondary Schools in Germany – The Impact of Social Origin and Gender

In the German school system, grades are the essential means of performance feedback and assignment. However, little research has been conducted on the factors that determine grades in addition to competencies, and existing findings are poorly replicated. Using data from the representative IQB Trends in Student Performance 2015 survey, our analysis combined a variety of personal and structural characteristics to examine and replicate grade-determining factors in German. In data analysis, we paid particular attention to the data generation processes. The results are interpreted based on Bourdieu's considerations of habitus and status maintenance and Boudon's primary and secondary effects of social origin. The results tie in with the reproduction-theoretical considerations of Bourdieu and Boudon and illustrate the dependence of grades on students' background characteristics.

Intra- and inter-site variability of soil contamination in road shoulders – Implications for maintenance operations

This study addresses soil contamination in vegetated road shoulders with diffuse inflow of runoff. It aims (i) to characterize the spatial distribution of three metals (copper, lead, zinc) and PAHs, and (ii) to identify influencing factors for the inter-site differences. An extensive sampling campaign was carried out on forty road segments in the Paris region, targeting various distances and soil depths. Copper and zinc contamination was found to be mainly restricted to the first 30 cm from the road, where their concentrations ranged respectively between 40 and 270 mg.kg−1, and between 150 and 950 mg.kg−1 (with a few additional extreme values related to the presence of a galvanized steel guardrail). Lead contamination was moderate (< 100 mg.kg−1 in more than 75% of the sites) and relatively uniform across the width of the shoulders. Conversely, highest PAH concentrations were found further from the road. These differences between contaminants were likely due to the varying importance of wet weather-related processes and atmospheric transport in their dispersion mechanisms. Copper and zinc concentrations correlated well with the traffic density, which alone explained ≥ 69% of the inter-site variability, whereas lead and PAHs did not exhibit such dependence. Soil organic matter was found to control the “ceiling” concentration of metals, thus limiting the maximum amounts that can be intercepted from road runoff. These results illustrate the feasibility of estimating contamination levels on road shoulders, and thus offer interesting perspectives for better consideration of the infrastructures' maintenance needs and improved routine operations.

Adaptive Leader–Follower Formation Control of Underactuated Surface Vehicles With Guaranteed Performance

This article studies the formation tracking control problem for a group of underactuated surface vehicles with guaranteed transient properties, including connectivity maintenance, collision avoidance, and tracking performance specifications. The formation is within the leader–follower control framework, in which every follower is controlled to track its leader and maintain a desired relative distance and bearing angle with respect to its leader such that the prescribed formation geometry is achieved based on local sensing capability. The onboard sensor systems are of limited range and angle of view, thus defining a cone of detectable region for every follower. Each follower can detect its leader, if and only if the relative distance and bearing angle keep always inside the predefined detectable region such that the connectivity between the follower and its leader is maintained over time. In addition to the consideration of connectivity maintenance, no collision between the follower and its leader is also considered. A transverse function control approach is introduced to overcome the difficulties caused by the off-diagonal system matrix and underactuation. The barrier Lyapunov function and adaptive backstepping procedure are incorporated into the formation control design to achieve the boundedness of the closed-loop systems with guaranteed transient performance. Collision avoidance and connectivity maintenance between every follower and its leader are also proven mathematically. Simulation studies are performed to show the effectiveness of the proposed control design technique.

Design, operation and maintenance considerations of horizontal flow roughing filters preceding slow sand filters

Design, operation and maintenance considerations of horizontal flow roughing filters preceding slow sand filters

An Efficient Case Retrieval Algorithm for Agricultural Case-Based Reasoning Systems, with Consideration of Case Base Maintenance

Case-based reasoning has considerable potential to model decision support systems for smart agriculture, assisting farmers in managing farming operations. However, with the explosive amount of sensing data, these systems may achieve poor performance in knowledge management like case retrieval and case base maintenance. Typical approaches of case retrieval have to traverse all past cases for matching similar ones, leading to low efficiency. Thus, a new case retrieval algorithm for agricultural case-based reasoning systems is proposed in this paper. At the initial stage, an association table is constructed, containing the relationships between all past cases. Afterwards, attributes of a new case are compared with an entry case. According to the similarity measurement, associated similar or dissimilar cases are then compared preferentially, instead of traversing the whole case base. The association of the new case is generated through case retrieval and added in the association table at the step of case retention. The association table is also updated when a closer relationship is detected. The experiment result demonstrates that our proposal enables rapid case retrieval with promising accuracy by comparing a fewer number of past cases. Thus, the retrieval efficiency of our proposal outperforms typical approaches.

Rob Gray, Forever Inspiring The Greening of Accountancy

ABSTRACT This paper highlights the seminal contribution of Rob Gray to the Greening of Accountancy on the criticality of capital maintenance and careful consideration of our resources. Today we are facing the extreme challenge of saving our planet and climate adaptation. Issues of intergenerational equity and resilience highlighted by Rob three decades ago remain today as paramount as they did in 1990 and his words remind us, we have far surpassed nature’s tolerance.

The role of biodiversity concerns in regional and nationwide forest management plans of Japan -Do forest plans promote conservation?

To clarify how regional biodiversity is conserved by forest management plans, we compared the regional forest plans of Japan with nationwide forest plans and the condition of the forest at each regional level. Some important considerations (e.g., riparian areas) for conservation and maintenance of biodiversity in forest production landscapes were omitted from the descriptions in some regional plans but were nevertheless included in the nationwide forest plan. In regional forest plans, “Designated specific forests that are important forests for conserving biodiversity were conserved” are essential in the plans, and other forests were not targeted for biodiversity conservation. Thus, land sparing (land-use specialization) was applied strictly, and major measures to conserve biodiversity in regional forest plans, rather than land sharing (multiple-use forestry), were taken. In particular, forestry-active prefectures emphasized that forests other than those already conserved were not considered for biodiversity conservation in the regional plans. The regional variability of biodiversity conservation in the regional plans depended mainly on the economic conditions of the forests. Since climate conditions and the natural disturbance regime have an impact on biodiversity in Japan, biogeographical variations should be incorporated into forest management plans. Top-down governance for forestry and biodiversity and decentralization to reflect regionality should be considered and reconciled.

Static flexural behaviour of concrete-filled spiral-welded stainless-steel tubes

Abstract Durability and maintenance considerations may necessitate the use of stainless-steel for concrete-filled steel tube structural elements. The cost-effectiveness of such concrete-filled stainless-steel tubes (CFSSTs) can be improved by utilising spiral-welded tubes compared to their longitudinally welded counterparts. Spiral-welded stainless-steel tubes (SWSSTs) are fabricated by helically bending a continuous length of steel plate and welding the resulting abutting edges. The flexural behaviour under static loading of such hollow as well as concrete-filled spiral-welded stainless-steel tubes (CF-SWSSTs) has not been investigated to date, unlike for other stainless-steel tube types. To address this research gap, an experimental program was conducted consisting of four-point bending tests on twelve self-compacting CF-SWSST specimens. Tube geometries of nominal outside diameter 152 mm, 203 mm and 229 mm with wall thicknesses of 2 mm and 3 mm each were considered for the tests, together with infill concrete strengths of 20 MPa and 50 MPa. Six hollow SWSSTs corresponding to each of the six tube geometries were also tested for reference. The study showed that the ultimate limit state (ULS) deformation mode of CFSSTs was similar, irrespective of the tube fabrication method. The same was found to be true for hollow stainless-steel tubes as well. However, for hollow SWSSTs, it appears that there is greater probability for local buckling to occur at the spiral-weld seam, unlike for CF-SWSSTs. Nonetheless, for both hollow and CF-SWSSTs, existing codified guidelines were found to provide considerably conservative estimates of the respective ULS moment capacities. The prediction conservativeness was comparable to that reported for other tube types. For the tested CF-SWSSTs, the existence of non-uniform concrete core confinement at the ULS was confirmed experimentally. Explicit consideration of such effects may lead to improved predictions of the ULS flexural capacity compared to existing methods.

Green infrastructure in western Washington and Oregon: Perspectives from a regional summit

Green infrastructure (GI) has grown in acceptance as a sustainable means to manage stormwater in urbanizing landscapes, while providing a multitude of additional benefits that range from improving community health to protecting local ecosystems. The mandated use of GI for the management of stormwater is arguably more prevalent in the Pacific Northwest, where GI is a required practice per municipal stormwater regulations in western Washington State, and the City of Portland OR. However, adoption in the region has faced several challenges. A regional summit to elucidate some of these successes and challenges was organized in Oregon and drew attendees from western Oregon and Washington. Six challenges that impact GI adoption, and six themes that emerged as possible strategies to overcome these challenges, were identified. The six challenges that were identified were: the lack of coordination, traditionalism, site-specific scales, environmental costs, a lack of expertise, and little consideration for maintenance. The six emergent themes identified were: the need for adaptive design and maintenance, the placement of GI for maximum impact, the concept of collective impact, valuation of GI, equity and GI, and the intersection of GI and community health.

Nuclear heat storage and recovery for the APR1400

Detailed here is the proposed design of the tertiary side of a Thermal Energy Storage (TES) System to be interfaced with the steam cycle of a Light Water Reactor (LWR) plant. This study extends the understanding provided by many previous investigations (i.e., beyond thermodynamic considerations) by specifically addressing real world constraints associated with the backfit of such a system to an operating LWR. These constraints relate to the feasibility of design modifications during an extended refueling outage, and to licensing, operational, and maintenance considerations. The Korean designed and built APR1400 plant is selected for integration with the TES tertiary system, resulting in a design which can be readily be adapted to most LWR plant. Heat transfer and transport from and to the nuclear steam cycle is by synthetic oil with high temperature capabilities. Heat storage is in the form of packed beds consisting of crushed rock. While the rates of storage and recovery are constrained by the design of the nuclear reactor and steam plant (i.e., 20% of reactor thermal power during storage, and ~11% during recovery) the total stored energy component of the system can be readily and economically scaled to any desired capacity (at the marginal cost of carbon steel vessels filled with rock). Finally, it is proposed that any nuclear installation with water access could employ bulk thermal energy storage built into an Ultra Large Barge for turnkey delivery with a concomitant reduction in installed cost and risk.

Combination of the custom trays bleaching technique with the in-office bleaching and considerations for result maintenance

ABSTRACT This study goal is to present a case report of tooth bleaching treatment with the combination of the custom tray and in-office techniques, and to discuss about the considerations for result maintenance. A treatment approach was planned involving exogenous bleaching with custom trays with 7.5% hydrogen peroxide, and in-office bleaching with 35% hydrogen peroxide. The in-office bleaching agent was applied in two 15-minute applications, without led light. The patient was instructed to use the custom trays only a day after, with one drop of the bleaching agent for each tooth space. After the application of the bleaching agent, the patient used the trays for 1 hour per day, continuously for 30 days, 15 days for each arch. Considering the executed treatment approach, we may conclude that when correctly indicated, tooth bleaching with the combination of the in-office and custom trays techniques can be an acceptable choice of treatment, capable of enhancing the smile esthetics with a simple technique that preserves the sound dental structure. The patient should be instructed for the maximum color preservation and esthetic result maintenance, and should be advised that retreatments may become necessary depending on the oral hygiene and frequence of coloured food and drinks intake.

Investigation of the influence of trunnion pin axial direction imperfection on arm stress based on the measurement results of Koubo dam new radial gates and a consideration for rational maintenance

Investigation of the influence of trunnion pin axial direction imperfection on arm stress based on the measurement results of Koubo dam new radial gates and a consideration for rational maintenance

Stator Flux Based Model Reference Adaptive Observers for Sensorless Vector Control and Direct Voltage Control of Doubly-Fed Induction Generator

A position sensorless operation of a doubly-fed induction generator (DFIG) is desired from considerations of cost, maintenance, cabling, and reliability. This article proposes two stator flux based model reference adaptive observers (SF-MRAOs) for the estimation of the rotor speed and position in a stand-alone DFIG. The cross product of the reference and estimated stator flux linkage vectors is fed as controller input in the existing method, thereby, making the observer model nonlinear. The first proposed method, which is based on notch filtering, offers a performance comparable to that of the existing method while reducing the number of voltage and current sensors required. The second proposed method linearizes the error input to the controller, making the controller design straight forward, and also leading to superior performance than the existing methods. The linearized SF-MRAO is shown to work successfully with good dynamic performance in vector control of a stand-alone DFIG. This article also shows that the proposed linearized SF-MRAO can be employed for obtaining the rotor current angle in direct voltage control of a stand-alone DFIG. Simulation and experimental results are presented from a laboratory prototype of a 10-hp DFIG coupled to a squirrel-cage induction motor. The sensitivity of the performance of the proposed linearized SF-MRAO to variations in machine parameters is also studied theoretically and experimentally.