Definition Of Reliability Research Articles

Reliability of water supplies in low and middle-income countries: a structured review of definitions and assessment criteria

Abstract The unreliability of water supplies in developing countries is a widely recognised concern. However, unreliability means different things in the variety of literature on water supplies, and no unified definition or assessment criteria exists. We review definitions of water supply reliability used in existing literature, as well as the various ways in which it is assessed. Thirty-three papers were selected for review that reported on reliability of domestic water supply and were based on empirical research in developing countries. Explicit definitions of reliability are given in four out of the 33 papers reviewed. These definitions vary, but features common are the functionality of the water supply system itself, and the extent to which it meets the needs of water users. Assessment criteria also vary greatly, with the most common criterion in urban settings being the duration/continuity of supply in hours per day, while in rural settings, the proportion of functional water systems is commonly used. The heterogeneity in the definitions and assessment criteria found in the review is perhaps indicative of a multi-attribute nature of the concept of reliability and any unifying definition and assessment criteria might do well to take this into account.

Анализ методов оценки надежности оборудования и систем. Практика применения методов

The analysis of models and methods of reliability evaluation of hardware and software is carried out. The basic concepts of reliability and safety methods of such systems and situations leading to errors, defects and failures are defined. The definition of reliability and safety of technical systems and software systems is given. The classification of reliability models: predictive, measuring and evaluation types. Evaluation models that are used more in practice are described. The standard of Software life cycle (ISO 15288:2002) is defined, focused on the development and control of system components for errors, starting with the system requirements. The results of application of reliability models (Moussa, Goel-Okomoto, etc.) to small, medium and large projects are presented and their comparative assessment is given. The technological module (TM) of reliability evaluation of complex software systems VPK (1989) is described. The quality model of the standard ISO 9126 (1-4): 2002-2004 with indicators of functionality, reliability, efficiency, etc., which are used in determining the maturity and certificate of the product is shown.

Reliability of information systems in organization in the context of banking sector: Empirical study from Poland

The notion of information systems (IS) reliability in organization is discussed in this article. It contains critical review of the literature, definition of IS reliability and brief overview of the theoretical model of IS reliability in organization developed by the author (including system reliability, information reliability, service reliability and usage reliability). The potential use of the model of IS reliability is demonstrated as a part of empirical research devoted to the analysis and evaluation of IS by the information technology (IT) specialists from inside and outside of the banking sector. The analysis is based on survey conducted among more than 200 IT specialists from and outside of the banking sector in Wroclaw, Lower Silesia, Poland. Banking sector is given as an example due to its uniqueness—extreme sensitivity to IS reliability and accuracy. The analysis of IS reliability in organization is supplemented by the comparison of the way of understanding the notion by the two groups of specialists in order to verify whether the IS reliability is understood in the same way by industry sectors differing in terms of their sensitivity to IS support.

A maximal flow method to search for d-MPs in stochastic-flow networks

Since 1954, the maximal flow problems have gained much attention in the world. They are also extended to many other fields for applications. For example, the definition of a network reliability is just to evaluate the probability of a live connection between the source node and the sink node such that the maximal flow of the network is no less than the demand d. The popular methods in the literature to evaluate the network reliability are mostly through minimal paths (MP) or minimal cuts (MC) of the network. One of them is the three-stages method: (a) searching for all MPs/MCs; (b) searching for all d-MPs (the minimal system states for d via MP)/d-MCs (the maximal system states for d via MC); (c) calculating union probability from these d-MPs/d-MCs. We found that a creative innovation in solving the maximal flow problems may have benefits in the evaluation of network reliability. Based on this idea, this paper proposes a new approach to tackle the problem of searching for all d-MPs by given MPs. The comparisons with the well known algorithm are made for benchmarking. More complicated examples are also examined for illustrative purposes.

Parametric model measurement: reframing traditional measurement ideas in neuropsychological practice and research

Objective: Neuropsychology is an applied measurement field with its psychometric work primarily built upon classical test theory (CTT). We describe a series of psychometric models to supplement the use of CTT in neuropsychological research and test development. Method: We introduce increasingly complex psychometric models as measurement algebras, which include model parameters that represent abilities and item properties. Within this framework of parametric model measurement (PMM), neuropsychological assessment involves the estimation of model parameters with ability parameter values assuming the role of test ‘scores’. Moreover, the traditional notion of measurement error is replaced by the notion of parameter estimation error, and the definition of reliability becomes linked to notions of item and test information. The more complex PMM approaches incorporate into the assessment of neuropsychological performance formal parametric models of behavior validated in the experimental psychology literature, along with item parameters. These PMM approaches endorse the use of experimental manipulations of model parameters to assess a test’s construct representation. Strengths and weaknesses of these models are evaluated by their implications for measurement error conditional upon ability level, sensitivity to sample characteristics, computational challenges to parameter estimation, and construct validity. Conclusion: A family of parametric psychometric models can be used to assess latent processes of interest to neuropsychologists. By modeling latent abilities at the item level, psychometric studies in neuropsychology can investigate construct validity and measurement precision within a single framework and contribute to a unification of statistical methods within the framework of generalized latent variable modeling.

Multi-objective design of water distribution systems based on the fuzzy reliability index

This paper reports the application of a multi-objective evolutionary algorithm to the design of water distribution systems. The objective functions are the minimization of the capital costs and the maximization of the hydraulic reliability of the network so as to identify the tradeoff between cost and reliability. Furthermore, a new deterministic reliability index named fuzzy reliability index is introduced utilizing fuzzy logic and the definition of hydraulic reliability. The multi-objective honey-bee mating optimization (MOHBMO) algorithm is developed to achieve the design of two well-known water distribution networks. Results show that the proposed reliability measure is able to produce appropriate hydraulic reliability in the system and the MOHBMO algorithm calculates desirable Pareto-optimal solutions.

171 - Mathematical Theory of Reliability as Affirmative Approach to Free Radical Theory of Aging

Similarly to technical devices, biological constructions are not perfectly reliable in operation, i.e. malfunctions happen alternating with normal operation functions. In engineering, reliability is defined as the ability of a device to perform its function for a given time under given specific conditions. The same definition of reliability fits biological systems. The conferences, which were initiated by Dmytro Grodzinsky, Ukrainian Academy of Sciences in Kiev, Ukraine, starting from 1975, have given a strong impetus to research in this direction (Grodzinsky, 1977). The reliability approach to the free-radical theory of aging is based on the simple general principles that (i) biomolecular constructions are designed in keeping with the genetic program in order to perform the programmed preset functions; (ii) all of them operate with limited reliability; (iii) timely replacement or prophylaxis of unreliable functional elements, i.e. metabolic turnover, is the main line of assuring high systems reliability; (iv) there is a finite number of critical elements which perform the supervisory functions over the preventive maintenance; (v) the supervisors operate with the limited reliability. On this basis, universal features of aging, such as the exponential growth of mortality rate with time and correlation of longevity with the species-specific resting metabolism, are naturally explained. The stochastic malfunctions of mitochondrial electron transport nanoreactors, which produce oxygen radical anions O2●– as the by-products of respiration, seem to be of first importance. As the reducing agent, O2●– affects the ratio of NADH/NAD+ and, by changing the activity of sirtuins, slows down renewal of biomolecular constructs. Furthermore, the mitochondrial O2●– production tends to increase with aging (Nohl, Koltover, Stolze, 1993; Payne, Chinnery, 2015). As a consequence, the oxidative-stress products and other metabolic “garbage” accumulate with the resulting impetus to autophagic or apoptotic cell death and the age-associated clinical disorders. Basing on this reliability-theory approach, one can estimate that the longevity of human brain could reach 250 years should the antioxidant defense against the free-radical failures be perfect. Hence, the free-radical redox timer serves as the effective stochastic mechanism of realization of the programmed deficiency in reliability of biomolecular constructs. The rate constants and concentrations of the so-called antioxidants are small to compete with the antioxidant enzymes for reactive oxygen species (ROS). However, the antioxidants provide the preventive protection against ROS, i.e. prophylactic maintenance via the organism’s neuro-hormonal system and/or microbiota (Koltover, 2009; 2016). Thus, the systems reliability approach serves as heuristic methodology in searching realistic mechanisms of antioxidant therapy of aging.

Can segmentation evaluation metric be used as an indicator of land cover classification accuracy?

It is a broadly established belief that the segmentation result significantly affects subsequent image classification accuracy. However, the actual correlation between the two has never been evaluated. Such an evaluation would be of considerable importance for any attempts to automate the object-based classification process, as it would reduce the amount of user intervention required to fine-tune the segmentation parameters. We conducted an assessment of segmentation and classification by analyzing 100 different segmentation parameter combinations, 3 classifiers, 5 land cover classes, 20 segmentation evaluation metrics, and 7 classification accuracy measures. The reliability definition of segmentation evaluation metrics as indicators of land cover classification accuracy was based on the linear correlation between the two. All unsupervised metrics that are not based on number of segments have a very strong correlation with all classification measures and are therefore reliable as indicators of land cover classification accuracy. On the other hand, correlation at supervised metrics is dependent on so many factors that it cannot be trusted as a reliable classification quality indicator. Algorithms for land cover classification studied in this paper are widely used; therefore, presented results are applicable to a wider area.

Assessing the Reliability of a Nanosensor Network for Monitoring Human Lung Cells

Recent advances in Nano-Science and Technology have provided opportunity to develop sensor nodes below 100 nm using various types of novel materials. These nanosensors have great potential in practical applications, such as measuring chemical compounds in concentrations as low as one part per billion, drug delivery, and disease diagnostics. Much research is devoted to designing and fabricating these nanosensors. However, the question of reliability is often ignored during the design process. Our research focuses on the reliability of one particular wireless nanosensor network (WNSN) that is used for monitoring human lung cells. The WNSN is probabilistically modeled and its reliability is analyzed under different scenarios. The main challenge here is how to define the reliability function for this particular WNSN. We attempt to do it by introducing a flexible definition of reliability that makes sense intuitively and allows for assessing the reliability function. Although this paper is motivated by one particular WNSN, our method of assessing reliability can also be used for any nanosensor where our proposed definition of reliability is reasonable.

AO Distal Radius Fracture Classification: Global Perspective on Observer Agreement.

Background The primary objective of this study was to test interobserver reliability when classifying fractures by consensus by AO types and groups among a large international group of surgeons. Secondarily, we assessed the difference in inter- and intraobserver agreement of the AO classification in relation to geographical location, level of training, and subspecialty. Methods A randomized set of radiographic and computed tomographic images from a consecutive series of 96 distal radius fractures (DRFs), treated between October 2010 and April 2013, was classified using an electronic web-based portal by an invited group of participants on two occasions. Results Interobserver reliability was substantial when classifying AO type A fractures but fair and moderate for type B and C fractures, respectively. No difference was observed by location, except for an apparent difference between participants from India and Australia classifying type B fractures. No statistically significant associations were observed comparing interobserver agreement by level of training and no differences were shown comparing subspecialties. Intra-rater reproducibility was "substantial" for fracture types and "fair" for fracture groups with no difference accounting for location, training level, or specialty. Conclusion Improved definition of reliability and reproducibility of this classification may be achieved using large international groups of raters, empowering decision making on which system to utilize. Level of Evidence Level III.

A unique method for estimating the reliability learning curve of optic nerve sheath diameter ultrasound measurement.

BackgroundOptic nerve sheath diameter (ONSD) measurement using ultrasound has been proposed as a rapid, non-invasive, point of care technique to estimate intra-cranial pressure (ICP). Ultrasonic measurement of the optic nerve sheath can be quite challenging and there is limited literature surrounding learning curves for this technique. We attempted to develop a method to estimate the reliability learning curve for ONSD measurement utilizing a unique definition of reliability: a plateau in within-subject variability with unchanged between-subject variability.MethodsAs part of a previously published study, a single operator measured the ONSD in 120 healthy volunteers over a 6-month period. Utilizing the assumption that the four measurements made on each subject during this study should be equal, the relationship of within-subject variance was described using a quadratic-plateau model as assessed by segmental polynomial (knot) regression.ResultsSegmental polynomial (knot) regression revealed a plateau in within-subject variance after the 21st subject. However, there was no difference in overall mean values [3.69 vs 3.68 mm (p = 0.884)] or between-subject variance [14.49 vs 11.92 (p = 0.54)] above or below this cutoff.ConclusionsThis study suggests a significant finite learning curve associated with ONSD measurements. It also offers a unique method of calculating the learning curve associated with ONSD measurement.

Toward a General Model of Financial Markets

This paper aims to discuss the possibilities of capturing efficient market hypothesis and behavioral finance under a general framework using the literature of decision theories and information sciences. The focus is centered on the broad definition of rationality, the imprecision and reliability of information. The main thesis advanced is that the root of behavioral anomalies comes from the imprecision and reliability of information. Modeling on basis of imprecision and reliability of information within the broad definition of rationality will lead us to a more general model of financial markets.

Reliability-Map-Guided Phase Unwrapping Method

Path-following algorithms are important components of phase unwrapping methods and present the merits of conciseness upon approach and efficiency during operation. These algorithms employ information from phase residues or data quality, typically in an independent mode for the difference between the distribution discreteness of residues and the distribution continuity of data quality values. Residues are a part of discontinuity boundaries, and poor data quality suggests where discontinuity boundaries lie; a combined application of these would result in better effects in unwrapping. In this letter, a novel priority-map-guided phase unwrapping method is proposed, and the proposed priority measure, which is called reliability, is a combination of the distance from residues and data quality. The definition of reliability ensures locations of long distances from residues and good data quality values with high priority in the unwrapping path, and locations near residues with poor data quality, which are liable to be discontinuity boundaries, are set as low priority. Such a priority map design provides a more reliable scheme than classic path-following algorithms. Through experiments and the resulting analysis, the robustness and efficiency of the proposed phase unwrapping method are demonstrated.

Reliability-based design optimization under mixture of random, interval and convex uncertainties

In view of the significant influences of multi-source uncertainties on structural safety, which generally exist in practical engineering (such as the dispersion of material, the uncertainty of external load and the error of processing technology), more academic research and engineering applications had paid attention to uncertainty in recent years. However, due to the complexity of the structural problems, there may be multiple uncertain parameters. Traditional methods of optimal design by single-source uncertainty model, particularly the one derived from probability theory, may no longer be feasible. This paper investigates a new formulation and numerical solution of reliability-based design optimization (RBDO) of structures exhibiting random and uncertain-but-bounded (interval and convex) mixed uncertainties. Combined with the non-probabilistic set-theory convex model and the classical probabilistic approach, the mathematical definition of hybrid reliability is firstly presented for a quantified measure of the safety margin. The reliability-based optimization incorporating such mixed reliability constraints is then formulated. The PSO algorithm is employed to improve the convergence and the stability in seeking the optimal global solution. Additionally, by introducing the general concept of the safety factor, the compatibility between the proposed hybrid RBDO technique and the safety factor-based model is further discussed. By virtue of the above two methods, two numerical examples of typical components (the cantilever structure and the truss structure) as well as one complex engineering example (the hypersonic wing structure) are performed, subjected to the strength or stiffness criteria. The accuracy and effectiveness of the present method are then demonstrated.

Product quality characteristics oriented task reliability modelling method for manufacturing equipments

To evaluate the task reliability of manufacturing equipments with many components, a short-time and long-time manufacturing process reliability model is proposed to fulfil this task. The short-time manufacturing process reliability model based on multiple regressions aims to eliminate the effect of datum error on product quality. The long-time manufacturing process reliability model studies reliability change mechanism over time by means of Markov chains. Reliability computing method is given by considering the general definition of task reliability. Proposed product quality characteristics oriented model applies to manufacturing equipment reliability evaluation which avoids discussing numerous components of manufacturing equipment and complex relationship between them. Finally, the case result indicates that the proposed model can get more accurate estimated value of manufacturing equipment task reliability.

Product quality characteristics oriented task reliability modelling method for manufacturing equipments

To evaluate the task reliability of manufacturing equipments with many components, a short-time and long-time manufacturing process reliability model is proposed to fulfil this task. The short-time manufacturing process reliability model based on multiple regressions aims to eliminate the effect of datum error on product quality. The long-time manufacturing process reliability model studies reliability change mechanism over time by means of Markov chains. Reliability computing method is given by considering the general definition of task reliability. Proposed product quality characteristics oriented model applies to manufacturing equipment reliability evaluation which avoids discussing numerous components of manufacturing equipment and complex relationship between them. Finally, the case result indicates that the proposed model can get more accurate estimated value of manufacturing equipment task reliability.

ASSESSMENT OF RELIABILITY AND RISK DEGREE FOR ACCIDENT INITIATION AT SLIME STORAGES OF 4th MINING ADMINISTRATION, JSC “BELARUSKALI”

Definition of reliability for dams of slime storage embankment is given on the basis of reliability theory and characteristics of reliability and their analysis are presented in the paper. The paper specifies qualitative indices for earth dams which are subdivided in two groups: applicability factors and structural reliability factors. A short analysis of all possible causes for accident initiation at earth dams has been made and the analysis has permitted to pinpoint eleven main objects for diagnosis for slime storage dams. In order to assess risk degree of accident initiation at JSC “Belaruskali” slime storages all possible causes of emergency cases and their probability of occurrence have been analyzed in the paper. The paper acknowledges the fact that dam malfunction is possible, as a rule, due to violation of operational rules and regulations. Main parameters of slime storage state which are to be controlled regularly in the process of its operation have been noted in the paper. Observation results over slime storages, calculations of dam slope stability for normal operation (a principal calculation case) and operating irregularities in water seals (a special calculation case). As a stability margin factor is close to 1.0 for a special calculation case, an extreme position of depression curve has been determined for all design sections. It has been recommended to carry out a constant control over its position, and in the case when it reaches its peak value it is necessary to undertake appropriate measures in order to reduce its value. Final expert estimations on probability of accident initiation at the investigated slime storage dams of the 4th Mining Administration, JSC “Belaruskali” have been prepared on the basis of the analysis comprising all the required factors. A conclusion has been made about low risk degree of their destruction.

Quantifying the True Cost of Transit: Case Study of Bus Routes in Boulder, Colorado

Quantification of the affordability of public transit must consider factors beyond the farebox cost. Monetization of the cost of service reliability was made possible by the availability of automatic vehicle locator (AVL) data, examined in this study of the Regional Transportation District (RTD) in the Denver, Colorado, metropolitan region in 2014. When time was valued at seven-tenths of an individual’s hourly wage, AVL data for the Dash route, which served Boulder, Colorado, showed that, taken together, the hidden cost of unreliable transit service and the incremental time to take transit rather than to drive could be up to 52% higher than the farebox cost alone for those that earned Colorado’s minimum wage. Over the course of a year, this monetized opportunity cost became equivalent to 269 one-way fares on a locally priced RTD route. Reliable service is a subjective parameter, and different definitions of reliability yield different monetized costs from the data set. For riders who depend on transit to arrive at work or other destinations on time, reliability and affordability are intricately connected. The interplay of these factors, particularly the often-ignored cost of unreliable transit routes, should influence efforts to improve public transit service.

Reliability, Dimensionality, and Internal Consistency as Defined by Cronbach: Distinct Albeit Related Concepts

This article uses definitions provided by Cronbach in his seminal paper for coefficient α to show the concepts of reliability, dimensionality, and internal consistency are distinct but interrelated. The article begins with a critique of the definition of reliability and then explores mathematical properties of Cronbach's α. Internal consistency and dimensionality are then discussed as defined by Cronbach. Next, functional relationships are given that relate reliability, internal consistency, and dimensionality. The article ends with a demonstration of the utility of these concepts as defined. It is recommended that reliability, internal consistency, and dimensionality each be quantified with separate indices, but that their interrelatedness be recognized. High levels of unidimensionality and internal consistency are not necessary for reliability as measured by α nor, more importantly, for interpretability of test scores.

Multi-domain DSM method for design process management of complex system

Design of a complex system is a collaborative activity among multiple domains, such as mechanical engineering, software engineering, and control engineering. A dependency model is effective for the management of its process. Because different domains often have different recognition of dependency, a design manager should coordinate the understanding gaps among multiple domains. This article proposes a multi-domain design structure matrix (MDDSM) method expanding a conventional DSM to coordinate differences of designers’ understandings about dependency of system components. MDDSM assumes that a designer describes dependency based on his/her expertise. MDDSM provides a method to define reliability of dependency description according to the degree of designer’s expertise of the corresponding system components. When different designers describe different dependencies, the reliability definition helps to decide which designer’s description is most reliable. This article also demonstrates a case study applying MDDSM to an industrial robot design process in order to verify its ability.