Life Distribution Research Articles

Assessment of Moment Live Load Distribution in FRP Composite Tub Girders for Highway Bridges

Assessment of Moment Live Load Distribution in FRP Composite Tub Girders for Highway Bridges

An AK‐MCS‐based probabilistic fatigue life prediction framework for turbine disc with a mean stress correction model

AbstractThe turbine disc plays a crucial role in aerospace engine, significantly influencing both their fatigue life and overall reliability. Due to the substantial uncertainties present, devising a method for the probabilistic analysis of turbine disc fatigue life becomes crucial. This paper introduces a novel framework that combines adaptive Kriging Monte Carlo simulation (AK‐MCS) with a mean stress correction model to evaluate fatigue life distribution effectively. AK‐MCS, stands out as an algorithm that constructs a Kriging model, effectively reducing the need for an extensive finite element analysis. Furthermore, a mean stress correction model is proposed for the Masson‐Coffin equation tailored for fatigue life prediction of GH4133 disc material. This model has been empirically validated to be effective. The presented framework for probabilistic fatigue life analysis not only holds considerable engineering value but also offers innovative approaches for tackling analogous challenges in the field.

An Integrated Detection-Prognostics Methodology for Components with Intermittent Faults

Abstract Some industrial components, such as valves, relay switches, and motors occasionally experience intermittent faults (IFs) that usually disappear without any repair or intervention. This phenomenon occurs at a relatively low frequency even in components that are in an “as good as new” state. However, an increase in the frequency of IFs often indicates the onset of degradation. We develop an integrated detection-prognostics model for components that exhibit IFs and whose degradation data is high-dimensional. We discuss the use of Dynamic Time Warping (DTW) and a Variational Autoencoder (VAE) to perform feature engineering on the data. We then propose a Hidden Markov Model (HMM) based monitoring strategy composed of two parts: (1) a detection model that tracks and flags changes in the intermittent fault frequency (IFF), and (2) a prognostic model that leverages how the transition probabilities of the HMM evolve with progressive degradation to compute the remaining life distribution (RLD) of the component. We examine the performance of our modeling framework using high-dimensional data generated from a vehicular electrical system testbed designed to accelerate the degradation of a vehicle starter motor.

Birnbaum Saunders distribution for imprecise data: statistical properties, estimation methods, and real life applications

A neutrosophic statistic is a random variable and it has a neutrosophic probability distribution. So, in this paper, we introduce the new neutrosophic Birnbaum–Saunders distribution. Some statistical properties are derived, using Mathematica 13.1.1 and R-Studio Software. Two different estimation methods for parameters estimation are introduced for new distribution: maximum likelihood estimation method and Bayesian estimation method. A Monte-Carlo simulation study is used to investigate the behavior of parameters estimates of new distribution, compare the performance of different estimates, and compare between our distribution and the classical version of Birnbaum–Saunders. Finally, study the validity of our new distribution in real life.

Life history characteristics and distribution of lake sturgeon in an unfragmented section of a northern river

Life history characteristics and distribution of lake sturgeon in an unfragmented section of a northern river

Advancements in Laplace transform techniques: Performing non-parametric hypothesis testing on real-world data through statistical analysis

This research delves into the exploration of a statistical testing approach grounded in Laplace transform techniques specifically tailored for the New Better than Used Laplace transform order (NBUL) class of life distributions. The developed test exhibits versatility, accommodating both complete and censored data, and critical values are systematically calculated for its application. Beyond the methodological presentation, our study investigates the test’s statistical power and explores Pitman’s asymptotic efficiency concerning various alternative distributions. Comparative analyses with other tests within the same class contribute to a comprehensive understanding of the proposed approach. To demonstrate practical applicability, we apply this novel testing technique to authentic engineering and medical datasets. The outcomes of these applications serve as illustrative examples, showcasing the effectiveness and relevance of the proposed methodology in real-world scenarios.

Salinity tolerance of fishes: Experimental approaches and implications for aquaculture production

AbstractThe life history, distribution and diversity of fishes are largely influenced by environmental salinity. Changes in salinity affect a range of physiological processes including metabolism, nutrition, reproduction and growth. Therefore, fish can be conditioned to environmental parameters most suitable for production, where distinct traits are optimised through species‐specific manipulation of salinities. The primary purpose of this review is to summarise the existing literature on the salinity tolerance of aquacultured fish. The various experimental approaches for determining salinity tolerance are compared, along with summarised information for key species employed in aquaculture, including their native distributions, life history stage and optimal salinity for survival and growth. The implications for production were assessed by considering the effects of salinity on growth, reproduction, management, disease mitigation and marketability.

Bayesian estimation of equipment reliability with normal-type life distribution based on multiple batch tests

Abstract The test of new equipment is usually carried out in multiple batches according to the task schedule and test results. Constrained by the test environment, cost, and other factors, the amount of reliability test data in each batch is relatively limited, which brings difficulties to the accurate equipment reliability estimation work. For the reliability simulation tests conducted before each batch tests, it is particularly important to make full use of each batch tests information and simulation tests information to estimate the reliability of the equipment for small sample tests. This study takes the common normal-type life distribution equipment as the research object, and selects the normal-inverse gamma distribution as the equipment life parameters prior distribution based on the Bayesian method. Combined with the system contribution, the fusion weights of each batch tests information are determined and all the batch tests information is fused. Finally, the estimation of equipment reliability based on multiple batch tests is completed. The research results show that this method can integrate the information of each batch test and simulation test, overcome the problem of insufficient information of single batch tests, and provide an effective analytical tool for equipment reliability estimation.

Pre‐impoundment fish migrations in the Mobile Basin, Alabama

AbstractAssessing the status of several migratory fishes in the Mobile River Basin, Alabama, has been complicated due to a general lack of historical data on their life history, habitat requirements, and distributions. Whether distributions were restricted by natural or man‐made barriers to migration is difficult to answer because few scientific collections were made before dams were built, and the earliest dams were built at the largest biogeographic barrier in the basin: the geological fall line. Therefore, we used what information was available, including anecdotal information, primarily records from archived newspapers and government reports, to describe the ranges of six migratory species prior to the construction of dams in the Mobile Basin. We describe the complicated history of Alabama Shad Alosa alabamae and show that range declines may have been masked by the stocking of American Shad Alosa sapidissima in the late 19th century. We show that Gulf Sturgeon Acipenser oxyrinchus desotoi probably migrated well above the fall line in the Coosa River, and may have been sympatric with Lake Sturgeon Acipenser fulvescens. We found no records of Alabama Sturgeon Scaphirhynchus suttkusi above the fall line. American Eel Anguilla rostrata migrated above the fall line in every Mobile Basin river before dams were built. Finally, Paddlefish Polyodon spathula may have once occurred above the fall line in at least two rivers, but they persist today in impounded reaches in the coastal plain, unlike some other species. We hope that future work will continue to consider archival sources of information to re‐trace the histories of imperilled species.

Statistical Insights: Analyzing Shock Models, Reliability Operations and Testing Exponentiality for NBRUmgf Class of Life Distributions

This study deals with a novel category of life distributions called the new better than renewal used in moment generating function (NBRUmgf) class. It delves into the connections between this form of aging and established aging categories, along with its relevance in a shock model. Additionally, it explores how this aging concept remains consistent through certain reliability operations which is consider a very important tool in reliability engineering. The research computes Pitman's asymptotic efficiencies for this testing procedure, comparing them with alternative methods. Furthermore, the study furnishes a comprehensive table of percentiles for the test statistic associated with this proposed method. Furthermore, in order to showcase the relevance of the study's conclusions, we utilize distinct real-world datasets, which illustrate the effectiveness of our test across various types of real data.

Axial live load distribution among single row of piles of integral bridges

This study investigates the axial live load distribution among steel H-piles in single-span integral bridges. To achieve this, two- and three-dimensional finite-element models for various integral bridges are conducted and analysed using the structural analysis software SAP2000, to determine the maximum axial loads in steel H-piles within two- and three-dimensional models. Subsequently, axial live load distribution factors from the ratio of axial loads calculated from these models are derived. The parametric study reveals that girder spacing and pile spacing exert notable influences on the axial live load distribution among the steel H-piles in integral bridges. Then, non-linear regression analysis is employed to formulate practical equations as functions of these two parameters. These equations can effectively calculate the live load distribution factors for the piles in integral bridges. To validate the accuracy of the live load distribution factors calculated from the proposed formulae, a comparative analysis is performed with results obtained from structural analysis. The standard deviations of the ratios between these two results are found to be a mere 2%. This clearly demonstrates that the developed formulae yield highly precise estimates of axial live load effects in integral bridge piles.

Fuzzy Regional Co-Location Pattern Mining Based on Efficient Density Peak Clustering and Maximal Fuzzy Grid Cliques

Due to the heterogeneity of data distribution in real life and the spatial autocorrelation among spatial instances, traditional spatial co-location pattern mining methods tend to ignore valuable information specific to local regions. To address the limitation, regional co-location pattern mining has been proposed to find patterns that may be hidden within local regions. In this paper, a fuzzy regional co-location pattern mining framework based on efficient density peak clustering and maximal fuzzy grid cliques is presented. By incorporating a grid-splitting method and fuzzy theory, an efficient density peak clustering algorithm is proposed to divide the global area into distinct local regions. Furthermore, we propose a method to materialize the neighbor relationships between instances based on the maximal fuzzy grid cliques, and parallelize the clustering process to improve the algorithm efficiency. Experimental results show that the proposed algorithm can not only reduce the time consumption by about 40%, but also mine meaningful patterns with tighter instance distributions.

Amphibitic stoneflies (Plecoptera) are integrators of ecosystem processes in alluvial aquifers of gravel‐bed river floodplains

AbstractOver 50 years ago nymphs of the Plecoptera species, Paraperla frontalis Banks, 1906 (Plecoptera: Chloroperlidae), were shown to exist in a shallow floodplain aquifer of the Tobacco River, a gravel‐bed river in western Montana and later they were documented throughout the main stems of the Flathead River system. Nymphs are almost never found in surface waters, until they emerge on the river shorelines. As teneral adults, they mate and subsequently deposit fertilized eggs into the river. This novel life cycle is termed “amphibitic.” Over the years we and others have found P. wilsoni Ricker, 1965 (Plecoptera: Chloroperlidae), Kathroperla perdita Banks, 1920 (Plecoptera: Kathroperlidae), and five species of Isocapnia Banks, 1938 (Plecoptera: Capniidae), including long‐winged and brachypterous adults and wingless dwarfs (male and female), occupying amphibitic niches in the alluvial aquifers of rivers in Washington, Idaho, Colorado, Alaska and British Columbia. These stoneflies are remarkably tolerant of hypoxia which allows them to exist as abundant consumers in aquifer food webs subsidized by ancient methane. Indeed, stonefly tissues contain carbon that is up to 7000 years old, underscoring the existence of a strong interaction involving the uptake of labile carbon derived from methanogenic and methanotrophic process in aquifers. Details of life cycles, trophic relationships, distribution and abundance have been documented by a suite of studies on the Nyack Floodplain of the Middle Flathead River, Montana. In this paper we review the ecophysiology and ecology of these unique stoneflies in the context of their functional role in gravel‐bed river ecosystems.This article is categorized under: Water and Life > Nature of Freshwater Ecosystems Water and Life > Conservation, Management, and Awareness

Global Climate Change and Its Effects on Medicinal and Aromatic Plants: A Review Article

Medicinal herbs have been used for a long time to cure health problems and prevent disease, including epidemics. Medicinal plants are used for different purposes and in diverse uses of human beings. People around them have a basic knowledge and using through their traditional medicine from the past several years. Natural and manmade calamities, such as rapid climate change, urban growth, industrial boom, overpopulation pollution, declining forest cover, habitat loss, over-harvesting, destructive harvesting, and floods, are the principal reasons of the reduction of wild medicinal plant species. The life cycles and distribution of the world's vegetation, especially wild medicinal plants, are being affected by climate change. The impact of global climate change on medicinal plants could have a huge influence, especially in terms of their utility in conventional medication systems and as economically useful plants. The current essay emphasises the importance of study to improve our understanding of climate influences on medicinal plants properties, phenology and metabolic responses. The purpose of this paper is to review the impact of abiotic variables on secondary metabolite formation and different adaptation measures as well as future research initiatives. Furthermore, such issues with global climate change will undoubtedly become more visible or immediate threats, putting further strain on medicinal plant species. The impact of global climate change on medicinal plants could negatively correlate with environment concerns parameters, especially in terms of their utility in conventional medication systems and as economically useful plants.

Defect sensitivity in L-PBF AlSi7Mg0.6 alloy subjected to fatigue load: Effect of load ratio and torsion loading

This study aims to investigate the impact of the defects on the fatigue behavior of the AlSi7Mg0.6 alloy processed by laser powder bed fusion (L-PBF) by considering uniaxial and torsion loadings up to 2×106 cycles. Several sets of specimens were produced and characterized using X-ray tomography. Fatigue tests were performed applying axial loading with different load ratios on the one hand, and torsion loading on the other hand. The critical defects responsible for fatigue failure were either isolated pores or clusters of small gas pores. The impact of the loading condition on the sensitivity to the different defect types observed in the material is discussed based on the analysis of the fracture surfaces. In particular, the results obtained for axial loadings showed that the critical defect size required to induce fatigue failure is decreased when a positive mean stress is applied, which impacts the distribution of the fatigue lives compared to pure tension-compression tests. For torsion loading, the clusters of gas pores were the predominant critical defect type, as opposed to axial loading. This increase in the criticality of the clusters when changing the loading type was investigated by means of numerical simulations accounting for real defect geometries.

Diversity and distribution of Raunkiær's life forms in European vegetation

AbstractAimsThe Raunkiær's system classifies vascular plants into life forms based on the position of renewal buds during periods unfavourable for plant growth. Despite the importance of Raunkiær's system for ecological research, a study exploring the diversity and distribution of life forms on a continental scale is missing. We aim to (i) map the diversity and distribution of life forms in European vegetation and (ii) test for effects of bioclimatic variables while controlling for habitat‐specific responses.LocationEurope.MethodsWe used data on life forms of 8883 species recorded in 546,501 vegetation plots of different habitats (forest, grassland, scrub and wetland). For each plot, we calculated: (i) the proportion of species of each life form and (ii) the richness and evenness of life forms. We mapped these plot‐level metrics averaged across 50 km × 50 km grid cells and modelled their response to bioclimatic variables.ResultsHemicryptophytes were the most widespread life form, especially in the temperate zone of Central Europe. Conversely, therophyte and chamaephyte species were more common in the Mediterranean as well as in the dry temperate regions. Moreover, chamaephytes were also more common in the boreal and arctic zones. Higher proportions of phanerophytes were found in the Mediterranean. Overall, a higher richness of life forms was found at lower latitudes while evenness showed more spatially heterogeneous patterns. Habitat type was the main discriminator for most of the responses analysed, but several moisture‐related predictors still showed a marked effect on the diversity of therophytes and chamaephytes.ConclusionsOur maps can be used as a tool for future biogeographic and macro‐ecological research at a continental scale. Habitat type and bioclimatic conditions are key for regulating the diversity and distribution of plant life forms, with concomitant consequences for the response of functional diversity in European vegetation to global environmental changes.

A novel refined maintenance strategy for full life cycle of high‐speed automatic train protection system

AbstractAutomatic train protection (ATP) system is essential for ensuring the safe operation of high‐speed trains. However, the existing extensive and fixed maintenance mode of the ATP system results in a waste of resources. To achieve a state of operation and maintenance that ensures both protection capability and economic efficiency, a lean method in a dynamic maintenance mode for the full life cycle of the ATP system is proposed. Firstly, reliability tests are carried out based on historical failure data. The parameter values of the possible life distribution are estimated by maximum likelihood method, and the optimal life distribution of different devices is obtained through the Kolmogorov–Smirnov hypothesis test. Secondly, a dynamic failure rate function is introduced to describe the impact of maintenance on device performance. A refined maintenance model is then established within the life cycle, and the dynamically changing preventive maintenance intervals and frequencies are obtained using a genetic algorithm. Finally, to mitigate the impact of the intermittent operation of ATP system on maintenance, the multidimensional relationships among the maintenance strategy, service time and operation mileage are revealed. The effectiveness of the proposed method is verified through an example test on a type of driver machine interface device.

Notes on the distribution and colouration in life of Stenomacra tungurahuana Brailovsky & Mayorga, 1997 (Hemiptera: Largidae)

The hemipteran Stenomacra tungurahuana Brailovsky & Mayorga, 1997 (Hemiptera, Heteroptera, Largidae) remains known from just two localities in the inter-Andean valley of Ecuador. No ecological information nor description of its colouration in life have been reported. In this contribution, I provide the first record of S. tungurahuana on the northeastern slopes of the Eastern Cordillera of the Andes and the first description of its colouration in life, including photographs, based on a specimen from San Isidro Lodge, province of Napo, ca. 108 km from the species’ type locality.

Reliability-Centered Preventive Maintenance Optimization for a Single-Component Mechanical Equipment

Due to the high failure rates of mechanical equipment with complex structures and numerous moving parts, devising an effective preventive maintenance (PM) plan and avoiding the influence brought by failure is crucial. However, some PM efforts are disorganized, unpractical, and unscientific, leading to prolonged downtime and significant cost losses. The challenge in creating PM plans is exacerbated by the asymmetry between maintenance and failure data. Therefore, focusing on single-unit mechanical equipment, the reliability-centered maintenance (RCM) idea is put forward to find out the key parts to implement preventive maintenance, and PM models are built to draw up a more reasonable PM plan. Such strategies aim to lower maintenance costs and enhance economic performance. Data on past maintenance and failures are analyzed to determine the life distribution and maintenance effect functions, helping to quantify the uncertainty caused by data asymmetry. Two PM optimization models considering time-varying failure rates are proposed: one focuses on minimizing costs, while the other aims to maximize availability. A PM plan example is demonstrated using a component from a tire-building machine including six parts, which proves the validity of the models. The availability results of two parts corresponding to the maintenance strategy obtained by the availability maximization model are above 0.99, and the results of total costs per unit time of the remaining four parts obtained by the cost minimization model are under 5.69.

Astroecology: bridging the gap between ecology and astrobiology

Abstract Although astrobiology studies how life functions and evolves, ecology is still largely overlooked in astrobiology research. Here we present an argument for astroecology, a merger of ecology and astrobiology, a self-aware scientific endeavour. Ecology is rarely mentioned in influential documents like the NASA Astrobiology Strategy (2015), and terms such as ‘niche’ can end up being used in a less precise fashion. As ecology deals with sequential levels of organization, we suggest astrobiologically-relevant problems for each of these levels. Organismal ecology provides ecological niche modelling, which can aid in evaluating the probability that Earth-like life would survive in extraterrestrial environments. Population ecology provides a gamut of models on the consequences of dispersal, and if lithopanspermia can be validated as a form of space dispersal for life, then metabiospheres and similar astrobiological models could be developed to understand such complex structure and dynamics. From community ecology, the discussion of habitability should include the concept of true vacant habitats (a misnomer, perhaps better called ‘will-dwells’) and contributions from the blossoming field of microbial ecology. Understanding ecosystems by focusing on abiotic properties is also key to extrapolating from analogue environments on Earth to extraterrestrial ones. Energy sources and their distribution are relevant for ecological gradients, such as the biodiversity latitudinal gradient – would tropics be species-rich in other inhabited planets? Finally, biosphere ecology deals with integration and feedback between living and non-living systems, which can generate stabilized near-optimal planetary conditions (Gaia); but would this work for other inhabited planets? Are there ‘strong’ (like Earth) and ‘weak’ (perhaps like Mars) biospheres? We hope to show ecology can contribute relevant ideas to the interdisciplinary field of astrobiology, helping conceptualize further levels of integration. We encourage new partnerships and for astrobiologists to take ecology into account when studying the origin, evolution and distribution of life in the universe.