Series-parallel System Research Articles

Analyzing component failures in series-parallel systems with dependent components

This paper investigates a series-parallel system comprising N independent subsystems with interchangeable dependent components, a prevalent reliability structure in engineering and network design. The primary aim of this research is to derive the joint probability distribution of the number of failed components within these configurations, considering component dependence and varying distributions across subsystems. This approach reflects a more realistic scenario than previously explored in the literature. Initially, the analysis is conducted for systems with two subsystems and subsequently extended to encompass configurations with N subsystems. The study also evaluates key reliability metrics including the average number of failed components and the mean time to failure (MTTF) of the entire system, theoretically proving that the system’s MTTF increases with the number of components under certain sufficient conditions. In addition to probabilistic analysis, an optimization problem is addressed to determine the optimal allocation of components within each subsystem. The objective is to minimize the average cost associated with corrective maintenance, thereby enhancing the cost-effectiveness of system operation.

Optimization of time-dependent MORRAP for series–parallel system using improved NSGA-II in interval environment

Optimization of time-dependent MORRAP for series–parallel system using improved NSGA-II in interval environment

Reliability optimization of reliability-redundancy allocation problems based on K-mixed strategy

In a reliability-redundancy allocation problem (RRAP), system reliability is maximized by selecting component reliabilities and finding the most suitable redundancy of subsystems. The advantages of a K-mixed strategy were introduced by modeling, so as to better improve system reliability. Compared with other existing redundancy strategies, the performance of a K-mixed strategy was verified using redundancy allocation problems (RAP). In this study, for the first time, a reliability calculation model under the new structure ( [Formula: see text] = 2 and [Formula: see text] = 1) is proposed, and the K-mixed strategy under the new structure is used in the reliability-RAP (RRAP), which is more complex than the RAP and further saves the production cost. In practical optimization, there was a complex decision-making problem to ensure optimal system reliability while minimizing system volume, weight, and cost. Then, this K-mixed strategy was adopted for modeling three benchmark problems in RRAP to seek a better and more flexible system structure. A powerful evolutionary algorithm (NSGA-II) was used to solve the new RRAP model to obtain the best system structure and reliability. The advantages of this model were confirmed by comparison with results from previous reliability optimization studies. The results show that the cost-saving advantages of the new structure in ensuring maximum reliability are significant. All the optimized remaining costs are noticeably higher than those of other methods, with the cost savings of the series-parallel system being the greatest. The difference in remaining costs compared to previous optimizations remains in the tens. Moreover, in more complex systems (Complex bridge system), the advantage in remaining volume is very significant, with the improvement being three times that of the optimization results of other methods.

System availability assessment and optimization of a series-parallel system using a genetic algorithm

System availability assessment and optimization of a series-parallel system using a genetic algorithm

Performance enhancement of PV array using successive ring adder algorithm based reconfiguration techniques

The photovoltaic array’s output is decreased due to increase of mismatch losses (ML) under partial shading condition. Different row currents begin to flow from the PV modules as a result. Therefore, the panels must be reconfigured to minimize the row current differential in order to get the most power possible from the PV panel. This paper suggests Successive Ring Adder Algorithms (SRAA) to minimize the difference of row current. Under various shading patterns, the proposed scheme’s superiority is evaluated and contrasted with series-parallel (SP) and Total-Cross-Tied (TCT) configurations. The numerical outcomes demonstrate the superiority of the suggested algorithm. Additionally, unlike the recently reported reconfiguration techniques, it may be used with both square (9 × 9) and non-square (9 × 6) PV arrays. In comparison to SP and TCT configuration system, the maximum power generation has improved by 4.04% and 9.25%, respectively. In comparison to TCT (30.96%) and SP (37.52%), the ML was obtained with the lowest value i.e. 25.87%. The efficiency for a 9 × 9 PV array is measured at 13.18%, the highest among TCT (12.67%) and SP (12.07%) configurations. For non-squared (9 × 6) PV array arrangement, similar types of enhanced outcomes are produced.

Multi-objective optimization of series-parallel system with mixed subsystems failure dependencies using NSGA-II and MOHH

In complex systems, failure dependencies play a crucial role in determining their overall performance. This paper explores the multi-objective optimization of series-parallel systems with mixed failure dependencies. By optimizing system cost and availability, the study aims to identify the most efficient redundancy and repair strategies. Two optimization algorithms, the non-dominated sorting genetic algorithm II (NSGA-II) and a novel multi-objective algorithm named the multi-objective hoopoe heuristic (MOHH), are utilized alongside constraint handling techniques to produce Pareto fronts. These fronts illustrate the trade-offs between cost and availability. Additionally, a fuzzy decision method is utilized to determine the best compromise solutions from each optimization technique. Comparing the results, NSGA-II consistently outperforms MOHH in providing better compromise solutions across five independent runs. However, MOHH demonstrates a better standard deviation in its performance.

Reliability dependent production-inventory model for redundancy allocation via fuzzy logic

This study deals with a reliability dependent production-inventory model in two scenarios: a redundancy allocation with crisp structure and the other with fuzzy logic. Here, a manufacturer purchases some raw-materials/components in variable cycles and arranges them as series-parallel system to produce a single item with production cost dependent on system reliability. In this model, a retailer gets the opportunity of warranty period and credit period offered by the manufacturer. Also, the retailer’s demand is dependent on system reliability, credit period and selling price. In the crisp model, the component reliability is exponentially dependent on known failure rate and failure time. However, there is no dependent relationship between these two parameters. Actually, the real world is full of uncertainty and these two parameters may depend on each other following some uncertain nature which can be expressed as fuzzy logic. So, in the fuzzy model, failure time has been considered as dependent on failure rate following fuzzy logic and these fuzzy relations are defuzzified by using three fuzzy inference techniques: Mamdani, Sugeno and Tsukamoto. Main goal of this article is to determine the optimum number of cycles and components to maximize manufacturer’s profit and system reliability with some constraints. The model is solved by using elitist non-dominated sorting genetic algorithm (NSGA-II) and some numerical examples closed to real-world have been executed. Comparative analyses are done for different cases; different fuzzy inference techniques and for active and mixed strategies. Finally, some sensitivity analyses and managerial insights are drawn.

Enhancing safety and reliability in multistory construction: A multi-state system assessment of shoring/reshoring operations using interval-valued belief functions

Ensuring safety and reliability in multistory concrete construction necessitates rigorous assessment methodologies capable of addressing the inherent uncertainties of the construction process. This paper introduces a novel reliability assessment methodology for shoring/reshoring (S/R) operations, framed within a multi-state parallel-series system (MSS). Our approach innovatively combines concrete slab capacities, forming system strengths, and construction quality, integrating cost and time efficiencies. Central to our method is the use of Interval Universal Generating Functions (IUGF), which leverage Dempster-Shafer (D-S) theory and interval analysis to robustly estimate system reliability under uncertainty. For instance, the model considers concrete strength ranging from 0.72 × 2.1D to 0.96 × 2.1D at different curing stages, producing a system reliability index between 0.63 and 0.76, against a desired threshold of 0.8. This methodology produces interval-valued belief functions that capture a comprehensive range of potential system states and their likelihoods, offering a refined perspective on system safety. An illustrative case study demonstrates the practical application of this methodology in optimizing formwork removal and S/R schedules, significantly enhancing decision-making in construction operations. This paper aligns with the core themes of reliability engineering and system safety by addressing critical safety and reliability issues in complex technological systems through advanced probabilistic safety assessment methods. It significantly enriches the professional discourse by presenting a robust method that can be adapted across various engineering fields facing similar reliability challenges.

Efficient opportunistic maintenance strategies via pruning in parallel–series systems with economic dependence

Opportunistic maintenance stands out as an effective strategy for minimizing maintenance costs and enhancing system efficiency. Despite its importance, current opportunistic maintenance models are often tailored to specific system types, particularly those with series structures, or they offer heuristic approaches for multi-component redundant systems. This paper shifts focus to the most common of such systems, the parallel–series system. We approach the optimization of opportunistic maintenance in a parallel–series system through a Markov Decision Process framework, utilizing phase-type approximations of individual component hazard functions. Addressing the challenge of the curse of dimensionality in the action space, this study conducts a thorough structural analysis of the optimal opportunistic maintenance policy, deriving a pruning procedure, which can reduce the extensive combinatorial action space into a more manageable linear complexity without sacrificing the strategy’s effectiveness in parallel–series systems. Building on this more manageable action space, we introduce a more efficient algorithm leveraging the proposed pruning procedure for determining the optimal opportunistic maintenance policy. The effectiveness and practical applicability of this approach are rigorously demonstrated through comprehensive numerical experiments.

Improving the Performance of a Parallel-Series System Based on Lindley Distribution

In this paper, a parallel-series system is improved. All components assume independent and identically distributed. The Lindley distribution with three parameters is assumed to be a lifetime distribution for the components. Four methods are used to improve the performance of the parallel-series system. The γ-fractiles and equivalence factors are derived. Finally, numerical results are discussed.

A comparison and an application of reliability, reliability system, hybrid reliability system functions for Rayleigh, Pareto, and Rayleigh Pareto distributions

This study dealt with the analysis of the reliability function for hybrid systems with asymmetric components, where the operating times of these components follow Rayleigh, Pareto, and Rayleigh Pareto distributions, furthermore, we introduced a method of operation based on hybrid systems in order to increase the reliability of the machines operating times. Different simulation experiments were done to estimate the reliability function of these systems using the ML method, then a comparison was made between those estimators, the simulation results proved that the Rayleigh-Pareto distribution gives the best estimate for the reliability functions, also the estimated values for the reliability function for the hybrid parallel-series system greater than the estimated values of the reliability function for the hybrid series-parallel system, finally, the estimated reliability function values of the proposed system are better than the estimated values of the two other systems. In the application part, it was chosen the operating times for the machines of the University House for printing, publishing ,and translation in Baghdad, where the factory management depends on the system hybrid serial-parallel system to operate the factory machines, this system leads to a decrease in the reliability of the operating times of the factory machines to 50% at the first operating hour, but if the blistering hybrid system is followed, i.e. the similar machines are run in parallel, and the different machines are run in series, then the probability that the machinery system will continue to operate for four hours will be 50%.

Mathematical Techniques for Computing the Reliability of a Parallel-series System of Order (2,3,1) under Rayleigh Failure Laws

Some well-known mathematical techniques have been used to compute the reliability of a parallel-series system of order (2,3,1). The system is composed of four units labelled as A, B, C and D. The configuration involves two parallel subsystems: the first containing units A, B and C arranged in series and the second comprising a single unit D. The failure rate of units is assumed to follow the Rayleigh distribution. With the use of the decomposition method, cut set method and event space method, expressions for both reliability and Mean Time to System Failure (MTSF) have been derived. By considering all units to be identical, the reliability measures have been obtained numerically for specific parameter values. The trends of these measures have been represented graphically to understand the effect of parameters. The study has its practical significance in assessing the reliability of solar panel system. . KEYWORDS :Parallel-series System, Rayleigh failure laws, Decomposition method, Cut set method, Event space method.

A Method for Evaluating Systematic Risk in Dams with Random Field Theory

The parameters of gravity dams and foundation materials objectively exhibit spatial variability due to environmental and load influences, which significantly affect the safety status of dam structures. Therefore, a safety risk analysis method for a gravity dam–foundation system based on random field theory is proposed in this paper. Spatial variabilities in materials are particularly considered by using the finite element method. Then, composite response surface equations for the performance function (PF) of strength and stability failure are established, and then, the system failure risk is obtained using the Monte Carlo method. The proposed method solves the problem wherein the effect of spatial variability on failure risk cannot be reflected accurately by the performance function of multi-element sliding paths, and the difficulties in solving the failure risk of the series–parallel system due to multiple failure paths and their complex correlations. The application of a gravity dam shows that the developed method overcomes the disadvantages of the traditional method, such as the homogenization of the spatially random characteristics of parameters and the overestimation of failure risk in the system due to large variance estimation.

Joint optimization of maintenance and spares inventory policy for a series-parallel system considering dependent failure processes

This paper investigates the joint optimization of condition-based opportunistic maintenance and spare inventory policies for a series-parallel system consisting of software and components. Software failure follows a homogeneous Poisson process. Components are subject to mutually dependent competing failure processes. When the software failure occurs, an opportunistic inspection will be implemented for the components. Besides the maintenance policy, the (s, S) inventory policy is applied for components. The maintenance and order decisions will be made according to the conditions of the components and inventory level at each inspection. The state transition probabilities and expected sojourn times can be obtained by the formulated semi-Markov decision process. The optimal inspection interval, the preventive replacement threshold of the component, and the order point can be derived by minimizing the expected average cost rate. Finally, the effectiveness and superiority of the proposed joint optimization model are verified by an illustrative example.

Improving the Performance of a Series-Parallel System Based on Gamma Distribution

The performance of a series-parallel system is improved by using the reliability equivalence factors technique. The lifetimes of the components are assumed to be gamma distributed. The system reliability is improved by using three different methods: (i) Reduction method, (ii) Hot duplication method, (iii) Cold duplication method. The reliability function and mean time to failure for each method are derived. Finally, the numerical application is introduced.

A Markovian approach to reliability estimation of series-parallel system with Fermatean fuzzy sets

Markov process has been an extremely contributive method in the reliability evaluation of electrical systems for the past many decades, as a result, it has been extended by numerous researchers to address various types of issues occurring in different types of engineering systems. However, one thing it fails to address is the fuzziness in real-life systems. This fuzziness or randomness can occur either because of incomplete awareness of the operating conditions or the application of different numerical assessment methods by different operators, causing inconsistency in a system’s assessment. It can be dealt with the incorporation of the concept of fuzzy sets in the reliability analysis. This study aims to incorporate fuzzy sets, specifically, Fermatean fuzzy sets (FFS) with the Markov procedure for assessing the fuzzy reliability, availability, and sensitivity of fuzzy reliability of a system. The described approach is justified with an example of a generic series–parallel system and its fuzzy reliability and availability are computed by Markov modelling where failure rates are characterized by triangular Fermatean fuzzy numbers (TFFN). It is obtained that the behaviour of reliability, availability and sensitivity are the same as in conventional reliability evaluation, thus establishing that the proposed technique is valid. The parameters thus obtained are also depicted both in tabular and graphical forms to achieve conclusive results.

Series–Parallel System Analysis and Reliability Research of Grid Structures Considering Adaptive Dynamic Bounding Threshold

There are many bars in grid structures, and their topological relationships are complex, so the workload of calculations involved in researching their reliability is large. In this paper, based on the geometric topological relationship within a grid structure, a series–parallel system analysis of the structure is carried out by means of node analysis, constraint grade division, and hierarchical combination analysis, and the series–parallel analysis results for the structure are used to judge the failure of the structure. In order to avoid the problem of missing important components due to unreasonable selection of the bounding threshold when identifying failed components, an adaptive dynamic bounding threshold method with high accuracy is introduced. The failure probability value of the failure path is calculated using the direct numerical integration method, and the reliability of the whole structure is obtained. Finally, the validity of this method is verified using an example of a square pyramid grid structure. The results show that the method is feasible for series–parallel system analysis, structural failure judgment, and reliability analysis of a grid structure.

Standby redundancy allocation for series and parallel systems

. The allocation of redundant components to a system is an efficient technique to improve its lifetime. In this article, we study the problem of two standby redundancy allocations for series and parallel systems, consisting of n-component (n≥2), in the sense of various stochastic orderings. It is assumed that components and redundancies follow a general lifetime distribution. For the case of allocating two redundancies to a series (parallel) system, we show that allocating the relatively stronger redundancy to the weaker component and the weaker redundancy to the stronger components can result in a system lifetime that is longer (shorter) in terms of the usual stochastic order. Moreover, various results associated with the hazard rate and reversed hazard rate orders are established. The outcomes of various papers are strengthened and generalized through our results. In addition, some applications are provided to illustrate our findings.

Exploring the synergistic effects of warm and cold standby units in availability modelling and assessment of complex series-parallel systems

Exploring the synergistic effects of warm and cold standby units in availability modelling and assessment of complex series-parallel systems

The General Crack Component Model for reversed cyclic shear

AbstractA growing body of research has shown that reversed cyclic shear loading of reinforced concrete (RC) causes effects that are not accounted for in monotonic behavioral models. Notable among these effects are a reduction in shear strength and significant plastic offsets. This paper presents the General Crack Component Model, a rational, mechanics‐based model that explicitly considers the constitutive behavior of cracks in RC. Cracked RC is treated as a series–parallel system of bonded and unbonded regions, where the crack interfaces have both crack closing hysteresis and a kinematic contact constraint. Validation was performed using data from monotonic and reversed cyclic experiments on panel elements, and has shown that this analytical model is able to accurately capture the salient features of reversed cyclic shear behavior.