Life Distribution Research Articles

Multiple ‘memory-based’ schemes for monitoring Maxwell distributions with measurement errors

In many industrial applications, Maxwell is used as a life distribution to describe the life characteristics of a product. However, the accuracy of the life test results is usually affected by factors such as the way the operator operates and the accuracy of the measuring instrument, which in turn affects the reliability of the test results. Measurement errors can adversely affect the inspection results. In this paper, we focus on solving the problem of measurement error when Maxwell distribution is used as a lifetime distribution. This paper focuses on Shewhart, double exponentially weighted moving average (DEWMA) and homogeneously weighted moving average (HWMA), exponentially weighted moving average (EWMA), and generally weighted moving average (GWMA) control charts with measurement error models are presented, respectively. In addition, corresponding control charts corrected for multiple measurements are provided to minimize the effects of measurement errors and ensure that the Maxwell distribution's lifetime characteristics are accurately monitored. Sometimes, relying only on good zero-state run length metrics can be misleading. Therefore, we used a variety of metrics to assess the performance differences between these control charts, including multiple zero-state run length metrics and conditional delay expectations (CED). Meanwhile, through Monte Carlo simulations, we investigate the effects of relevant parameters on the performance of the control charts. Finally, the effectiveness of these control charts in practical applications is further verified through two real examples.

On the Equivalence of Likelihood‐Based Confidence Bands for Fatigue‐Life and Fatigue‐Strength Distributions

ABSTRACTFatigue data arise in many research and applied areas, and there have been statistical methods developed to model and analyze such data. The distributions of fatigue life and fatigue strength are often of interest to engineers designing products that might fail due to fatigue from cyclic‐stress loading. Based on a specified statistical model and the maximum likelihood method, the cumulative distribution function (cdf) and quantile function (qf) can be estimated for the fatigue‐life and fatigue‐strength distributions. Likelihood‐based confidence bands can then be obtained for the cdf and qf. This paper provides equivalence results for confidence bands for fatigue‐life and fatigue‐strength models. These results are useful for data analysis and computing implementation. We show (a) the equivalence of the confidence bands for the fatigue‐life cdf and the fatigue‐life qf, (b) the equivalence of confidence bands for the fatigue‐strength cdf and the fatigue‐strength qf, and (c) the equivalence of confidence bands for the fatigue‐life qf and the fatigue‐strength qf. Then we illustrate the usefulness of those equivalence results with two examples using experimental fatigue data.

Molecular Identification and Description of the Tadpole of Leptobrachella melanoleuca (Matsui, 2006) (Amphibia: Anura: Megophryidae)

Identifying tadpoles will significantly enhance future studies on life histories, behavior, ecology, and distribution of amphibian species. This study provides a detailed morphological and buccopharyngeal description of Leptobrachella melanoleuca tadpoles, utilizing DNA barcoding for accurate identification. Ten tadpoles, measuring 15.0±1.22 mm (range: 12.0–16.6 mm) in body length, were collected from Khlong Saeng Wildlife Sanctuary, Surat Thani Province, southern Thailand. Mitochondrial gene sequences, including 12S rRNA, tRNA-Val, and 16S rRNA, showed less than 0.1% divergence from adult L. melanoleuca in GenBank and our adult specimens, confirming the identification. Both tadpoles and adults were found in a small rocky stream. The tadpoles exhibit dark brown coloration with brown blotches in life, while preserved specimens show significant fading. The tadpoles’ external morphology includes a translucent abdomen, darkened throat, and dark gray chest. The tail musculature is gray with light brown spots, and the fins are slightly transparent. Buccopharyngeal anatomy revealed a semicircular prenarial arena with knobby projections, narrow choanae, and a densely pustular buccal roof arena. The buccal floor features triangular tongue anlage, trapezoidal prelingual arena, and large buccal floor arena papillae. The Keratodont Row Formula (KRF) is recorded as 1:2–2/0 or 2+2/0, with black jaw sheaths. These findings contribute significantly to our understanding of tadpole morphology in the genus Leptobrachella, providing a crucial reference for future taxonomic and ecological studies of this and related species.

Research on Reliability Analysis and Life Distribution of Brushed DC Motor Based on Intelligent Valve Working Condition

Research on Reliability Analysis and Life Distribution of Brushed DC Motor Based on Intelligent Valve Working Condition

Diversity and Adaptation of Plant Life Forms in Bassi Wildlife Sanctuary: A Phytoclimatic Analysis

Bassi Wildlife Sanctuary is located in the South-Eastern part of Rajasthan, India. This study resulted in plant life form diversity and distribution using Raunkiaer's classification system. Extensive field surveys were conducted in BWS between April 2017 and March 2019 to identify and record plant species. The collected specimens were identified by using state and regional floras (Shetty & Singh, 1987, 1991, 1993; Tiagi and Aery, 2007; Yadav& Meena, 2011; Harikrishna et al., 2022). A total of 468 plant species belonging to 322 genera and 85 families were recorded. The results indicate that therophytes (55.8%) are the dominant life form, followed by phanerophytes (23.5%), hemicryptophytes (7.3%), cryptophytes (6.8 %) and chamaephytes (6.6%). On comparison with Raunkiaer’s normal spectrum, the present study area depicts Thero-phanerophytic type of phytoclimate. This study also provides valuable insights into the plant ecology of BWS and contributes to the understanding of the region's biodiversity.

Гарантированные оценки функции распределения остаточного ресурса технологического оборудования промышленных предприятий

The article discusses the functioning processes of the process equipment at industrial enterprises, including numerical control machines (CNC), metal cutting machines, press-forging and bending equipment, welding and laser equipment, molding and casting equipment, etc. The problem of determining guaranteed estimates of the distribution function of process equipment’s residual life is formulated as a problem of finding guaranteed (lower and upper) estimates of the probabilistic functionality on the multitude of distribution functions with preset timings equal to the distribution timings determined based on the initial small sample size of trouble-free operation timings of process equipment. An approach to finding guaranteed estimates of the residual life distribution function in conditions of incomplete data on the process equipment operation time before a failure based on the results of the solution for Markov’s timing problem has been proposed. Guaranteed estimates of residual life distribution functions are based on a multitude of discrete distribution functions that meet the timing limitations. Examples of finding guaranteed estimates of process equipment residual life distribution function are provided.

Temperature and precipitation influence the distribution of different Cyperaceae life forms: The role of protected areas in the Amazon for conservation

Climate change is the main cause of global biodiversity loss and changes in the structure of ecological communities. Species distribution models are an efficient tool for predicting suitable areas for species and their vulnerability to climate change. In this study, we evaluated the impact of precipitation and temperature (factors of climate change) on 12 species of the Cyperaceae family, classified into three groups: aquatic, amphibian, and terrestrial. Our results provide a comprehensive overview of habitat projections for aquatic, amphibian and terrestrial Cyperaceae species in the Amazon biome under current and future scenarios. We highlight significant range losses projected for species such as Scleria amazonica and Cyperus lacustris in the future. The relationship between climate and its influence on species distribution is critical, emphasizing the urgent need to conserve biodiversity in the face of climate change. In the models, protected areas were essential refuges for species under threat, highlighting their crucial role in preventing biodiversity loss. Variables such as temperature and seasonality (rainfall variability) strongly influenced the distribution patterns of Cyperaceae species. Seasonal fluctuations such as extreme droughts can influence water availability and the growth dynamics of hydrophytic plants. Amphibian species adapt to temperature fluctuations and changes in precipitation, while terrestrial plants prefer warmer and rainy regions. Our results emphasize the importance of conservation strategies for Amazonian species. We have also shown that protected areas play an essential role in conserving biodiversity and protecting Cyperaceae species from future changes.

Influence of cross-girder spacing on RC T-beam bridges: a comparative theoretical and finite element approach

Cross girders are seen as typical elements in different types of bridges. In a T-beam bridge, cross girders are essential in stiffening the longitudinal girders laterally and reducing the exterior girder’s torsion. This study aimed to understand the effects of varying cross-girder spacing in a T-beam bridge by studying the relationship between several cross-girders with key structural parameters like Shear force (SF), maximum displacement, Bending moment (BM) and torsion. For this, different models were prepared in Finite Element Analysis (FEA) software, and cross girders varied from 0 to 10 in number. Here, the span and width of the bridge were taken constant, with several cross girders as the only varying parameter. The loadings were taken as per the IRC code. From analysis, it has been found when considering a combination of dead load and live load, the odd number of cross girders is seen as more effective in live load distribution. Further, it’s seen that BM and deflection decrease when cross girders are increased from 2 to 3 but then increase with further addition of no. of cross girders. Hence, an optimum number of cross girders that reduce BM and deflection is 3. Similarly, a comparison was made between the distribution factor obtained from FEA software and Courbon’s distribution factor, and variations were observed.

Impact of global environmental changes on the range contraction of Eurasian moose since the Late Pleistocene

Climatic oscillations are considered primary factors influencing the distribution of various life forms on Earth. Large species adapted to cold climates are particularly vulnerable to extinction due to climate changes. In our study, we investigated whether temperature increase since the Late Pleistocene and the contraction of environmental niche during the Holocene were the main factors contributing to the decreasing range of moose (Alces alces) in Europe. We also examined whether there were significant differences in environmental conditions between areas inhabited by moose in Europe and Asia, that could support the division of moose into western and eastern forms, as suggested by genetic and morphological data. We analysed environmental conditions in the locations of 655 subfossil and modern moose occurrences over the past 50,000 years in Eurasia. We found that the most limiting climatic factor for the moose distribution since the Late Pleistocene was July temperature. More than 90 % of moose records were found in areas where mean summer temperature was below 19 °C, with July temperatures showing over 3 times narrower interquartile range compared to January temperatures. We identified significant differences in environmental conditions between areas inhabited by the European and Asiatic moose. In Europe, the species occurred in regions with milder climates, higher primary productivity, and more frequently within forest biomes compared to Asiatic individuals. The moose range shifted more in the west-east than in the south-north direction during the Holocene climate warming in Europe. We conclude that although the area of suitable moose habitat has increased since 12–8 ka years BP, as demonstrated by environmental niche modeling, the retreat of A. alces in large areas of Europe was likely caused by anthropogenic landscape change (e.g., deforestation) and overhunting by humans during the late Holocene rather than by climate warming during the Pleistocene to Holocene transition.

An assessment of live hard coral cover distribution and its physicochemical factors in the Strait of Malacca from 1995 to 2016

The Strait of Malacca is well-known as an important trade route with high marine biodiversity. Among the organisms residing in the strait are the reef-building hard corals. Studies have shown that climate change and other anthropogenic stressors have induced severe degradation of coral reefs through the disruption of coral productivity and metabolisms. Moreover, in-depth investigations of causal inference of coral degradation and its correlations with potential coral-affecting physicochemical factors within the strait are limited. Hence, this study presents the analyses of the latest bi-decadal time-series trend from 1995 to 2016 of the live hard coral coverage (or live coral cover) and six coral-affecting physicochemical factors (significant wave height, sea surface salinity, particulate inorganic carbon, particulate organic carbon, turbidity, and sea surface temperature) using remote sensing and reanalysis datasets. Their potential correlations were interpreted by implementing meta- and statistical analyses of past coral surveys and remote sensing data. This study revealed the overall persistent bi-decadal decline in live hard coral coverage within the Strait of Malacca and the complex correlations among the factors that correspond to the spatial stratification of the marine environment. Among the six physicochemical factors, sea surface temperature, turbidity, and sea surface salinity were determined to be the most influential parameters on live coral cover distribution within the strait.

Reliability Analysis for Unknown Age Class of Lifetime Distribution with Real Applications in Medical Science

Analyzing the reliability of the aging class of life distribution provides important information about how long a product lasts and sustainability measures that are essential for determining the environmental impact and formulating resource-saving plans. The study emphasizes the goodness-of-fit technique of the nonparametric test for the NBRUmgf class because age data are crucial for applications. Evaluations were conducted using the test’s asymptotic properties and Pitman efficiency methodology for some selected asymmetric probability models, and the outcomes were compared with those of alternative methods. We assessed the test’s power against widely used reliability distributions for some well-known alternative asymmetric distributions, including the Weibull, Gamma, and linear failure rate (LFR) distributions, and provided percentiles for both censored and uncensored data. This study shows the efficacy of the test in various sectors using real-world datasets and comprehensive tables of test statistics.

The Consortium of Celestials: Cosmic objects equitable interactions

This speculative design study presents a provocative inquiry into the idea of an equitable society, addressed through the exploration of cosmic scale and celestial object interactions. The issues of injustice occurring in current society are influenced by the lack of access to resources and opportunities, where architecture also plays a part. Using a post-humanist approach, the study speculates on the scale of society, broadening the context of civilisation to develop an equitable society. The study creates a science narrative of a cosmic-scale civilisation as the basis of the architectural scheme between celestial objects in cosmic space that interacts in an equitable way. The narratives inform systems of architectural interactions that are designed to support an equitable life system, including communication, extraction, processing, and distribution of spatial and environmental resources. Five particular scenarios are outlined to demonstrate these interactions, from scenarios of resource exchange, climate calibration, and anticipation of destruction. This study demonstrates an important discussion on how design of an equitable society can be informed by the interactions between cosmic objects, systems, and resources. In doing so, this study introduces new narrative of architecture as a form of extraterrestrial built environment, expanding the current understanding of context and its environmental limitations.

Life Prediction and Reliability Evaluation of Reinforced Concrete Frame Structures Considering the Collision Response Under Earthquake Conditions

Firstly, in this study, we utilize the high-order element model (truss link model) simulation method in OpenSees (3.7.0) software and verify the feasibility of this method by comparing it with the shaking table test. Secondly, the structural dynamic response of adjacent structures with different performance levels, spacing, and layout forms under large earthquakes is analyzed, and the corresponding structural failure probability is studied. Furthermore, the life distribution within the design service life of the structure is predicted according to the nonparametric Kaplan–Meier estimation model. Finally, the reliability of adjacent structures is evaluated by using the joint engineering demand parameters. The analysis method of replacing the theoretical analysis based on engineering experience and certainty in the current specification with probability analysis is proposed, which provides a more reliable theoretical basis for decision-making regarding the reinforcement, maintenance, or demolition of structures in the later stage.

Pore-based prediction of crack initiation life in very-high-cycle fatigue

The porosity of the material produced by additive manufacturing technology gives rise to a notable dispersion of the crack initiation life in the very-high-cycle fatigue regime. The crack initiation life in the very high cycle fatigue regime can be divided into the initial crack initiation life and early microcrack growth life. This paper proposed a model considering the effect of pore morphology and location to predict the initial crack initiation life. The average local stress in a grain near the pore is modified by considering the relationship between pore roundness, inclination, position, and stress concentration factor. The growth life of early microcrack is determined by integrating empirical formulas based on dislocation theory. Subsequently, the probability distribution of crack initiation life is obtained, which is in good agreement with the experimental results. The competition factor is proposed to quantitatively evaluate the tendency of crack initiation from the surface or the interior, taking into account the influence of local average stress and grain size. The predicted load corresponding to the shift in crack initiation position is in accordance with the experimental results.

Residual Inaccuracy Extropy and its properties

Abstract In this paper, we introduce a novel concept of a dynamic residual inaccuracy measure based on extropy. We extend the traditional residual inaccuracy measure to its dynamic version, which allows us to measure the discrepancy between two residual life distributions. We study the properties of the proposed measure, including its discrimination principle and the proportional hazard rate model. We also investigate a characterization problem related to the extropy inaccuracy measure and propose some alternative expressions of the dynamic residual measure of inaccuracy. Furthermore, we establish upper and lower bounds and some inequalities concerning dynamic residual inaccuracy measures based on extropy. We demonstrate that the defined measure of inaccuracy is invariant under scale but not under location transformation. The given findings have important implications for statistical inference, estimation, and modeling. The proposed extropy-based dynamic residual inaccuracy measure provides a powerful tool for quantifying the discrepancy between two residual life distributions over time. At the end of the paper, we provide two non-parametric estimators for the proposed extropy measure of inaccuracy for both the non-censored (complete sample) and the right-censored scheme. The performances of these estimators are compared numerically based on their bias and MSE.

Efficacy and long-term effects of the intervention of Zhan Zhuang Qigong on Pisa syndrome in Parkinson's disease: the study protocol for a randomised control trial.

Pisa syndrome (PS) is a postural abnormality that frequently manifests in various neurological disorders. In recent years, the dangers associated with Parkinson's disease (PD) and PS have been increasingly acknowledged, leading to heightened research efforts directed toward the treatment of PS. Nevertheless, the underlying causes of PS remain complex, and no clinically effective treatments have been established. While several studies have demonstrated the significant effects of Qigong in treating PD, there is currently no evidence to support the efficacy of Qigong in the treatment of PS. To assess the immediate and long-term effects of Zhan Zhuang Qigong on PS in participants with PD using a rigorous randomised, parallel-control design with assignment concealment and evaluator-blinding methodologies. 60 PD participants meeting the inclusion criteria will be recruited and randomly assigned to one of two groups: conventional treatment (n=30) or Zhan Zhuang Qigong (n=30). The conventional treatment group will receive standard medications and physical therapy. The Zhan Zhuang Qigong group will receive conventional medicine plus 30 min of Zhan Zhuang Qigong practiced five times per week. The long-term effects of Qigong on PS will be evaluated after 6 months and 1 year of follow-up. Assessment tools will include the NeuroPostureApp, the B-PHY(A model of a balance testing system) balance check training system, the Unified Parkinson's Disease Rating Scale and the Parkinson's Disease Quality of Life Questionnaire, which will measure total camptocormia, upper hump degree, Pisa angles, plantar pressure distribution, motor function and quality of life in participants with PD. The local ethics committee approved this study (approval number: 2023-K068). The committee will oversee the study throughout its duration and will be notified of any protocol modifications. The results of the study will be disseminated through publication in an international journal or presentation at a conference. ChiCTR2400079696.

A system reliability demonstration test design method based on subsystem test data

AbstractReliability demonstration test (RDT) is the test to verify that the reliability of the product meets the reliability requirements during product development and is usually required to be performed to determine whether it can be accepted. It is essential for complex systems with higher costs. However, the traditional test plans such as the plan in the current RDT standard GJB‐899A have the problem of too long test time or too high risk. In addition, the test data of the complex system itself is usually less, but the test data of the subsystem is easier to obtain. In this paper, the research object is the system, and the main research content is how to use the reliability growth data in the development stage of the subsystem to design the system RDT. First, based on the reliability growth model, the test data in the development stage of the subsystems are modeled to obtain the reliability of each subsystem. The Bayesian theory is used to obtain the lifetime distribution of the system. Then, according to the definition of the two types of risks in the RDT, the life distribution of the product is integrated into the two types of risks, and the RDT plans of the system are designed. Finally, a simulation case is used to verify our RDT design method, and the results show that compared with the traditional plan, our RDT plan designed has a shorter test time and lower test risk.

Fatigue Life and Stress Analysis of a Single Cylinder Four Stroke Crankshaft

This paper focuses on the optimization of a crankshaft using ANSYS software in terms of weight and strength. The initial designs of the crankshaft, piston, and connecting rod were created using SolidWorks. The force generated by the gas during the combustion process was calculated to be 12017 N. Next, the SolidWorks assembled system was imported into ADAMS View software for simulation, which revealed a time-variant force of the crankpin of 14049 N. The calculated value was verified with results obtained from analytical calculations, showing a deviation of 0.23%. Finite element analysis was done for the crankshaft using ANSYS transient structural after applying loadings and boundary conditions. The optimization process aimed to minimize the crankshaft's weight while maintaining its strength and durability. The results of the ANSYS simulations showed a weight reduction of 2.5% from the original 2.983 kg to 2.907 kg, while maintaining the required strength and durability. The optimized crankshaft was compared to its original design in terms of fatigue life, weights, and stresses. The maximum von Mises stress was reduced by 16%, shear stress by 3.5%, and deformation by 3.5%, which were validated through analytical calculations. The crankshaft analysis resulted in a significant increase in fatigue life, calculated to be infinite under the given conditions. To conclude, the objective to optimize the crankshaft for performance and efficiency was achieved, demonstrating a 2.5% weight reduction and substantial improvements in fatigue life and stress distribution, proving the effectiveness of ANSYS software for the design optimization process.

Analytical method of incorporating failure probability to predict the fatigue life of ultra-high-performance concrete (UHPC)

This study predicted the fatigue life (N) of UHPC incorporated with different volume fractions (Vf = 0.0%, 0.5%, 1.0%, 1.5% and 2.0%) of steel fiber under flexural cyclic loading at various stress levels (S). The Weibull distribution, a two-parameter model, was utilized to estimate the distribution of fatigue life in UHPC. Subsequently, three methods were employed to calculate the parameters: the graphical method, the method of moments, and the method of maximum likelihood. The averaged values of these parameters were then obtained to enhance the accuracy of the estimation. The results are presented in the form of S-N diagrams, which depict the quantitative relationship between stress (S) and fatigue life (N). This relationship was determined using the Wohler equation, the modified Wohler equation, and the power equation. By employing these equations, the flexural fatigue strength of UHPC can be accurately predicted. Subsequently, the fatigue failure probability (Pf) was incorporated to enhance the reliability of the S-N quantitative relation. The fatigue testing results were presented in the form of S-N-Pf curves, which comprehensively reflect the relationship between stress, fatigue life, and failure probability. Furthermore, the mathematical relation of the S-N-Pf curves was derived to predict the fatigue life of UHPC with a given failure probability, providing a more comprehensive and accurate assessment of its fatigue behavior.

Stochastic properties of varentropy based on residual lifetime

The objective in the study of reliability and survival theory is to have precision in the extracted information. The measure of dispersion in the information content has been newly introduced in the information theory, known as varentropy. Studying the variability in the uncertainty measure is found productive for stochastic systems conditional on survival. In this paper, we provide a novel stochastic order based on the notion of residual varentropy and study its properties. Further on the basis of the residual varentropy, novel classes of life distributions are identified and investigated in detail. Moreover, some applications of the proposed order are produced at the end.