Quantitative Reliability Assessment Research Articles

Development and application of the Demands for Population Health Interventions (Depth) framework for categorising the agentic demands of population health interventions

BackgroundThe ‘agentic demand’ of population health interventions (PHIs) refers to the capacity, resources and freedom to act that interventions demand of their recipients to benefit, which have a socio-economical pattern. Highly agentic interventions, e.g. information campaigns, rely on recipients noticing and responding to the intervention and thus might affect intervention effectiveness and equity. The absence of an adequate framework to classify agentic demands limits the fields’ ability to systematically explore these associations.MethodsWe systematically developed the Demands for Population Health Interventions (Depth) framework using an iterative approach: (1) developing the Depth framework by systematically identifying examples of PHIs aiming to promote healthier diets and physical activity, coding of intervention actors and actions and synthesising the data to develop the framework; (2) testing the Depth framework in online workshops with academic and policy experts and a quantitative reliability assessment. We applied the final framework in a proof-of-concept review, extracting studies from three existing equity-focused systematic reviews on framework category, overall effectiveness and differential socioeconomic effects and visualised the findings in harvest plots.ResultsThe Depth framework identifies three constructs influencing agentic demand: exposure — initial contact with intervention (two levels), mechanism of action — how the intervention enables or discourages behaviour (five levels) and engagement — recipient response (two levels). When combined, these constructs form a matrix of 20 possible classifications. In the proof-of-concept review, we classified all components of 31 interventions according to the Depth framework. Intervention components were concentrated in a small number of Depth classifications; Depth classification appeared to be related to intervention equity but not effectiveness.ConclusionsThis framework holds potential for future research, policy and practice, facilitating the design, selection and evaluation of interventions and evidence synthesis.

THE PROBLEM OF RELIABILITY OF GEODESIC NETWORKS

Nowadays, the theory of reliability is widely used in the construction industry, and it is also used in the field of geodesy. By abstracting its position, it can be successfully transferred to systems that, it would seem, are not in a dynamic state. Let's take, for example, the points of the polygonal (leveling) network in the city. It would seem that such a network is in a static state, but over time it undergoes changes, that is, it is in imperceptible dynamics and its reliability gradually decreases.
 Reliability in the broadest sense of the word means the ability of a technical device (system, network) to operate without interruption (failure) for a given period of time under certain conditions. Such a period of time is usually determined by the time of execution of some task, which is carried out by the device or system and is part of the general operational task.
 Currently, the problem of reliability is becoming one of the central problems of engineering and management organization. Ensuring the reliable operation of all system elements is of primary importance.
 The modern interpretation of the term "reliability" in geodesy is associated with Baard's reliability theory, according to which reliability is defined as "the ability of the network to self-monitor against gross errors [1]. One of the indicators of reliability is the minimum amount of gross error that can be detected after statistical analysis of the corrections obtained after equalization. On this path, many difficulties arise, most of which remain unsolved, namely the impossibility of localizing a gross error, quantitative assessment of reliability, methods of designing reliable geodetic networks. The unsatisfactory state of reliability theory limits its practical application, but at the same time, the problem of product reliability is the main one in modern production and its importance is growing all the time. In this regard, there is an acute problem in highlighting new views on solutions to this problem in the field of designing and creating geodetic networks.
 A new scheme for constructing the theory of reliability of geodetic measurements is proposed. Its basis is a probabilistic determination of reliability, a system of tolerances, and methods of localizing gross errors. Reliability is defined as a probabilistic measure of the homogeneity of measurements that have passed control. Quantitative reliability is estimated by three indicators: differential, integral and the minimum gross error. The Neumann-Pearson criterion is recommended for establishing tolerance. This theory makes it possible to design geodetic networks with a given reliability. 

Reliability Assessment of Cyber–Physical Distribution Systems Considering Cyber Disturbances

With the development of communication technology, traditional distribution networks have gradually developed into cyber–physical systems (CPSs), from which the cyber system provides more protection for the grid and brings new security threat–cyber disturbances. Current research cannot scientifically measure the impact of cyber disturbances on the system and lacks reliability indices for a comprehensive quantitative assessment of CPS reliability from the perspective of cyber–physical fusion. If the impact of information disturbances on system reliability is not assessed accurately, it will not be possible to provide a scientific and reasonable decision basis for system planning and operation. Therefore, a set of reliability assessment methods and indices for distribution network CPSs considering cyber disturbances is proposed. Firstly, a reliability modeling method combining fault tree and Petri net is proposed to model the reliability of a distribution network CPS, which can improve the efficiency and accuracy of the modeling. Secondly, the system state is divided into two categories: normal operation state and cyberattack state. Then, generalized reliability indices considering cyber disturbances for distribution network CPSs are defined. Finally, through the tests on the modified IEEE RBTS BUS2 distribution network CPS, an analysis of the effects of information component failures, cyberattacks, and access network structures on system reliability is conducted in this paper to verify the efficiency of the proposed method and the rationality of the newly defined reliability indices.

Analysis of data transmission network construction technologies with high requirements for information security, reliability, and latency

The scientific article is dedicated to the analysis of contemporary approaches and technologies in the construction of data transmission networks aimed at ensuring information security, reliability, and minimal latency. The necessity of comprehensively considering factors influencing network efficiency with a focus on reliability and security is substantiated. Network analysis enables the creation of an infrastructure that meets the demands of the modern information environment, comprehensively weighing the advantages and disadvantages of each network technology during construction. For the mathematical evaluation of data transmission network reliability, a Markov model is proposed, which is based on Markov processes theory. Developed using the Python programming language and relevant libraries, the model allows for a quantitative assessment of data transmission network reliability, considering various failure factors, state transitions, and recovery. The model facilitates forecasting network states and planning preventive organizational and technical measures to ensure reliability and security, in light of the constantly increasing demands for service quality and confidential information protection. An analysis of transmission delay methods has revealed a correlation between the transmission speed and volume of information with various factors, such as bandwidth, network load, connection type and speed, and data processing by network nodes. The research underscores the need to choose specific methods based on the network’s characteristics and its intended tasks. Based on the analysis results, to construct efficient networks that meet information security, reliability, and transmission delay requirements, there is a recognized need for comprehensive development of evaluation systems and the creation of a unified evaluation model.

A quantitative reliability assessment and risk quantification method for microgrids considering supply and demand uncertainties

Microgrids have received great interest in achieving high renewable energy penetration. However, intermittent renewable generation may cause reliability problem (i.e., power inadequacy), especially for islanded microgrids. A comprehensive quantitative reliability assessment of microgrids considering uncertainties is essential. Current uncertainty-based reliability assessment approaches usually consider the uncertainties on the supply side only or additionally consider the uncertainties on the demand side using a general distribution without considering the uncertainty characteristics of different demands. This may lead to unreliable assessment results. Besides, existing reliability performance indexes cannot measure the probability/risk of power inadequacy under uncertainties. In this study, a novel uncertainty-based reliability assessment approach is therefore developed for microgrids considering uncertainties at both supply and demand sides. A new reliability index is proposed and a risk quantification method is developed to measure the risk/probability of power inadequacy under uncertainties. The uncertainties at both supply and demand sides are detailedly quantified using a bottom-up approach. The proposed reliability assessment and risk quantification method are tested on an islanded hotel microgrid in Hong Kong. The results show that the proposed reliability assessment approach can provide more robust reliability assessment results while the conventional approach has a probability of 8% to underestimate the maximum outage power. The proposed risk quantification method can help to provide more comprehensive reliability assessment results under uncertainties. The risk quantification results indicate that the highest monthly power inadequacy risk of the hotel microgrid appears in August (i.e., 5.8%), while the highest hourly risk appears at 9:00 p.m. (i.e., 4.8%).

Quantitative Assessment of the Operational Reliability of Overhead Power Transmission Lines

Quantitative Assessment of the Operational Reliability of Overhead Power Transmission Lines

Automated Analysis of Service Life of Air-Lines of the Electricity Transmission of Electric Power Systems

Basic EPS objects, which service life has exceeded normative value, increasingly affect – every year to a greater extent – the efficiency of overall performance. This manifests itself in increase of a number of automatic emergency shutdowns, an amount and complexities of accident-hazardous defects. After the expiration of the standard service life, there is a special need for a quantitative assessment of reliability and safety of an object. It is recommended to organize the operation, maintenance and repair of these objects according to their technical condition, and since it determines the reliability and safety of the object, these properties should be taken into account more fully. The relevant recommendations in electric power systems are implemented at a qualitative level, intuitively, according to the operating experience. There are neither quantitative evaluations nor methodology for their performance. Therefore, a method and algorithm of quantitative assessment of integral indicators of reliability and safety of operation of thermal power units of thermal power plants as concentrated objects of continuous operation were previously analyzed by the authors. The present paper examines distributed objects of continuous operation, viz. overhead power transmission lines with a voltage of 110 kV and higher, whose service life exceeds the standard value. Attention is paid to the issues of quantitative assessment of the degree of aging for a set of overhead power transmission lines, classification of these lines to identify the most significant classes and methodology for assessing the difference in the degree of aging when classifying them according to specified types of signs (for example, the difference in the degree of aging of overhead power transmission lines of grid enterprises of electric power systems). It is shown that it unacceptable to use the estimates of the relative number of overhead power transmission lines, the service life of which exceeds the calculated one, for comparison since it causes a great risk of an erroneous decision. The methodology and algorithm of methodological support of the management of electric power systems and grid enterprises in the organization of operation, maintenance and repair have been developed.

Unbalanced currents effect on the thermal characteristic and reliability of parallel connected power switches

In many industrial applications, parallel connection of power semiconductor switches is widely used to achieve higher power levels and fault-tolerant operation. But there is a current imbalance between parallel connected switches in practical applications. In this research, the impact of unbalanced currents on the junction temperature and the reliability of parallel connected switches are quantified and analyzed. Markov based reliability model is developed for quantitative assessment of reliability for parallel switches under different current sharing. The Mean Time to Failure (MTTF) is calculated for different conditions to be used as reliability metric for comparison of various conditions. A sensitivity analysis is also presented to show the effect of parameter variation on the junction temperatures of devices and reliability of the system. At last, a downscaled setup has been built up and tested. Experimental results verify the theoretical analysis and confirm procedure. Also, junction temperatures of power semiconductor devices are measured using thermal camera.

Evaluating the Impact of Prediction Techniques: Software Reliability Perspective

Maintaining software reliability is the key idea for conducting quality research. This can be done by having less complex applications. While developers and other experts have made significant efforts in this context, the level of reliability is not the same as it should be. Therefore, further research into the most detailed mechanisms for evaluating and increasing software reliability is essential. A significant aspect of growing the degree of reliable applications is the quantitative assessment of reliability. There are multiple statistical as well as soft computing methods available in literature for predicting reliability of software. However, none of these mechanisms are useful for all kinds of failure datasets and applications. Hence finding the most optimal model for reliability prediction is an important concern. This paper suggests a novel method to substantially pick the best model of reliability prediction. This method is the combination of analytic hierarchy method (AHP), hesitant fuzzy (HF) sets and technique for order of preference by similarity to ideal solution (TOPSIS). In addition, using the different iterations of the process, procedural sensitivity was also performed to validate the findings. The findings of the software reliability prediction models prioritization will help the developers to estimate reliability prediction based on the software type.

Study on the Reliability of Mechanical Components of Squib Valve in Passive Nuclear Power Plant

The action principle of squib valve employed in passive nuclear power plant was introduced and the main factors affecting the reliability of the mechanical components of the squib valve were analyzed, and the shear cover material of the squib valve was subjected to different strain rates at normal temperature, 155 °C and 350 °C, The parameter distribution of Johnson-Cook constitutive model was obtained by fitting the test data, and the impact velocity, material properties and failure strain of the squib valve piston were selected as random variables, and the reliability of the mechanical components of the squib valve was calculated by the joint simulation of ABAQUS+NESSUS. The results show that the reliability of the squib valve is high, and the mechanical performance of the shear cap material is the biggest impact on the mechanical reliability of the squib valve. The mechanical reliability of the squib valve is positively related to the impact speed of the piston. This study provides a reliable basis and reference for quantitative assessment of the overall reliability of the squib valve and the application in passive nuclear power plant.

Multi-Objective Trade-Off Quantification Based Design Optimization for Power Electronic Systems in More-Electric-Aircrafts

In this paper, a comprehensive formulation of reliability models for active and passive power components (i.e., capacitors and power semiconductor devices (MOSFETS)) of a regulated transformer rectifier unit (RTRU) for more electric aircraft application is presented. Additionally, the work focuses on the reliability analysis and evaluation at the system level for a non-modular discrete MOSFET based auxiliary power supply unit for more-electric-aircraft. A rigorous quantitative assessment of reliability, volume and power loss is carried out at the component level as well as system level, verifying how a particular design relates to the specific performance parameters. Keeping this as a motivation, this paper also focuses on studying and analyzing the inter-relation among reliability and other performance metrics such as power density and efficiency taking a 3kW RTRU as an example design. The major metrics under consideration for this study are the failure in time (FIT), mean time to failure (MTTF), power density, efficiency while keeping the eye on most failure prone elements of the power converter - capacitors and active power semiconductors. A comprehensive quantitative evaluation based on thermal management size, system reliability is done on choice of the switching semiconductors where the candidate pool includes Si and SiC MOSFET technologies. From the analysis on three different types of widely used capacitors - film, ceramic, aluminum electrolytic, it is concluded that the optimum choices of capacitors for high voltage DC link and low-voltage output belong to Aluminum and Ceramic types, respectively. Finally, the optimum selection of power stage components is derived from the extensive evaluation of the overall RTRU system in terms of system size and reliability.

Fault Detection in a Hybrid Dickson DC–DC Converter for 48-V Automotive Applications

Autonomous driving features have introduced safety-critical processor modules. A 48-V network has been developed to enable efficient power distribution. A fault-tolerant high-voltage power management unit is required to ensure continuous power delivery to critical loads. This article compares the cost and efficiency penalty of accommodating the fault-tolerant capability in common dc-dc topologies. The comparison is verified using a 0.13-μm high-voltage automotive Bipolar-CMOS-DMOS SMARTMOS technology in a Cadence simulation environment. Besides, a quantitative reliability assessment of the single-phase and multiphase configurations is presented. This has led to the selection of the hybrid Dickson topology, which has the best electrical performance and comparable cost and reliability among all for high-conversion-ratio fault-tolerant 48-V automotive application. Moreover, this article presents a fast and robust short-circuit and open-circuit fault detection scheme for power switches and flying capacitors in a hybrid Dickson dc-dc converter. The detection method only observes the low-voltage switching node, which eliminates the challenges associated with high-voltage high-bandwidth sensing. The performance of the design has been verified using a multiphase 48-V-to-3.3-V 4-to-1 Dickson converter prototype. The measured results demonstrate that the short-circuit faults are detected within two switching cycles of 250 kHz, which is less than the 10-μs short-circuit immunity of commercial silicon devices.

Reliability Assessment Based on GO Method of Metro Traction System

In order to improve the reliability of the metro traction system (MTS), the whole life cycle of metro vehicles can be operated safely and reliably. A reliability assessment method based on the GO method of the MTS is proposed. In this paper, the reliability assessment is completed without operation service failure of the metro vehicle. The maintainability and shutdown correlation of many electrical components in the MTS are considered. An accurate algorithm with shared signals is used. Then the quantitative and qualitative reliability assessment of the system is achieved with the goal of traction system providing traction for the vehicle. The evaluation identifies the weak links of the system. Comparing the completely independent quantitative calculation result of each component with the accurate quantitative calculation results, it is found that the complex correlation in the repairable system has an important effect on the reliability of the system. A comparative analysis is performed on the calculating results of the GO method and fault tree analysis (FTA) method. The results demonstrate that the reliability analysis of the MTS by the GO method is feasible and reasonable. The principle of the method is simple and the logic is clear. It can not only objectively reflect the working process of the MTS, but also fully characterize the complex correlation with shut down fault in the MTS. The qualitative assessment results of the system show that the cut set probability of the pantograph is the highest, which should be the focus of the MTS.

Quantitative software reliability assessment methodology based on Bayesian belief networks and statistical testing for safety-critical software

This study proposes an overall methodology that provides in-depth evidence on software reliability. It is used to quantitatively assess the reliability of nuclear power plant (NPP) safety-critical software for the incorporation of digital instrumentation and control systems into NPP probabilistic risk assessment (PRA). The methodology consists of three parts: (1) the relationships among the software development life cycle (SDLC) phases, the number of remaining faults in the software, and the probability of failure on demand (PFD) are modeled by a Bayesian belief network, which can provide a prior distribution of the software PFD; (2) a reliability model for the PFD is used to calculate the number of no-failure tests needed to meet the expected reliability target according to the prior distribution; (3) the software statistical testing (SST) based on PRA is used as a reliability validation test method to assess reliability, when the required no-failure tests are completed, it is considered that the software meets the expected reliability target. The main contribution of this methodology is that it fully considers the factors that affect software reliability, i.e. the quality of development activities and verification & validation (V&V) activities of the SDLC processes, software operational profile and software operational environment when assessing software reliability. This is done such that the methodology overcomes the subjectivity of separate quality assessments of the SDLC processes. It also solves the problem that occurs because an individual SST using an uninformative prior distribution is conservative.

A Bayesian Network Approach to Estimating Software Reliability of RSG-GAS Reactor Protection System

Reliability represents one of the most important attributes of software quality. Assessing the reliability of software embedded in the safety of high ly critical systems is essential. Unfortunately, there are many factors influencing software reliability that cannot be measured directly. Furthermore, the existing models and approaches for assessing software reliability have assumptions and limitations which are not directly acceptable for all systems, such as reactor protection systems. This paper presents the result of a study which aims to conduct quantitative assessment of the software reliability at the reactor protection system (RPS) of RSG-GAS based on software development life cycle. A Bayesian network (BN) is applied in this research and used to predict the software defect in the operation which represents the software reliability. The availability of operation failure data, characteristics of the RPS components and their operation features, prior knowledge on the software development and system reliability, as well as relevant finding from references were considered in the assessment and the construction of nodes on causal network model. The structure of causal model consists of eight nodes including design quality, problem complexity, and defect inserted in the software. The calculation result using Agenarisk software revealed that software defect in the operation of RPS follows binomial statistic distribution with the mean of 1 . 393. This number indicated the high software maturity level and high capability of the organization. T he improvement of software defect concentration range on the posterior distribution compared with the prior’s is also identified . The result achieved is valuable for further reliability estimation by introducing new evidence and experience data, and by setting up an appropriate plan in order to enhance software reliability in the RPS.

METHODOLOGY OF ASSESSING INDIVIDUAL RELIABILITY OF UNIQUE STRUCTURES

The paper describes the author’s methodology of quantitative reliability assessment of unique systems that are components of very expensive critical/strategic infrastructures, manufactured in very small series/batches, or even as single, unique structures. It was dubbed “theory of individual structural reliability — TISR”. With the development of the 3D digital technology and digitization that opened the door to creating digital twins in design, the share of unique products is growing non-stop in all branches of contemporary heavy industry and machine-building (rotor excavators, continuous casting plants, drilling rigs), adjacent sectors of industry (ship-building, aircraft building), and construction industry (large span bridges, super high skyscrapers, exhibition pavilions etc.). In this paper the TISR methodology is described for a class of unique and non-renewable objects using as an example a one-time-deployed-when-on-orbit robotic technological complex, designed to serve without interruption for 12–15 years in the near-space environment. The paper is a direct extract from preprint [1], revised and translated into English by its first author. The initial data needed for writing paragraphs 4 and 6 of this paper belongs to Yu. P. Pokhabov, published elsewhere, which made the description of implementing the TISR methodology in the field of unique spacecraft design up to date. The author greatly appreciates and acknowledges the provided input.

METHODS AND MODELS FOR ASSESSMENT OF RELIABILITY OF STRUCTURAL-COMPLEX SYSTEMS


 
 
 
 The article presents the main propositions of logical-probabilistic method of analysis the assurance and enhancement of reliability of structurally complex systems, in which the structure of the system is described by means of mathematical logic and quantitative assessment of reliability is performed using probability theory. An example build script the dangerous condition and performed a quantitative investigation of the reliability of complex systems with interdependent basic events. The methods and models are implemented in a computer system that provides the ability to objectively assess the reliability and safety of structurally complex systems and solving problems of operational decision-making in complex emergencies.
 
 
 

ТЕОРЕТИКО-МНОЖИННІ МОДЕЛІ ОБ’ЄКТІВ ЗІ ЗМІННОЮ СТРУКТУРОЮ

Мета статті – обґрунтування можливості використання теорії множин для моделювання об’єктів зі змінною структурою для уточнення кількісної оцінки значень показників надійності з врахуванням часу роботи окремих частин. Результати. У статті запропонований підхід до аналізу структур радіоелектронних засобів, що відрізняються багатофункціональністю та багаторежимністю, тобто змінюють структуру під час використання за призначенням, із застосування математичного апарату теорії множин. Це дозволяє в подальшому кількісно оцінити значення показників надійності (наробітку на відмову та середнього часу відновлення) залежно від порядку взаємодії підмножин елементів та їх потужності. Висновки. Врахування властивості багаторежимності засобів спеціального зв’язку з впровадженням теоретико-множинної моделі їх структури дозволяє точніше кількісно оцінити значення показників надійності. Отримані результати доцільно використовувати під час розробки математичної моделі і методів оцінки надійності багаторежимних засобів та систем спеціального зв’язку зі змінною структурою. Подальші дослідження слід направляти на формалізацію процесу кількісної оцінки показників надійності об’єктів зі зміною структурою.

Design and validation of a simple automated optical step counting method for treadmill walking

Background: Reliable step counting is a critical part of locomotion research. Current counting methods can be inaccurate, time consuming, expensive or encumbering to the subject. Here, we present a camera-based optical method for automatically counting steps.Methods: Fifteen healthy adults walked, jogged and ran on a treadmill at three different constant speeds (1.21, 2.01, 2.68 m/s) and once at varying speed (1.21–2.68 m/s) for 90 s. Subjects had visual marker affixed to their left foot while walking. Video was recorded synchronously at low- and high-resolution during trials. The step count found manually from the video was compared to an automated video analysis system using the two configurations of the optical system.Results: Bland–Altman plots, Intra-class correlation coefficients (ICC) and relative error comparison were used for quantitative assessment of device reliability. Reliability of optical method was high (ICC ≥0.98).Conclusions: The method produces accurate step count results for the range of speeds tested. They use customisable open-source software and off-the-shelf hardware. The method has a low cost of implementation compared to many consumer products and grants researchers access to the raw sensor data.

Mechanical Characteristics of Cylinder Pin Tumbler Locks as They Relate to Resistance Testing

In recent years, there has been a great development of methodologies, procedures and software tools for quantitative assessment of reliability, efficiency and effectiveness of physical protection systems. Absence of some important input values, as well as missing method to obtain them, is still the most serious problem. This paper is focused on analysis of possibilities how to obtain delay time values in the case of cylinder pin tumbler locks using non-destructive methods of breaking. In the introduction of the article, a proposal of the methodology for testing the mechanical resistance of cylinder pin tumbler locks is elaborated. Consequently, the focus is set on analysis of results obtained during the pilot tests in order to verify the correctness of the proposed methodology. With the tests, it is possible to assess the resulting resistance of cylinder pin tumbler locks also in terms of classification into resistance classes. The pilot testing needs to be implemented mainly due to the lack of a technical standard that processes the issue within the established methodology.