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The three-parameter Weibull distribution is one of the most widely used probabilistic models for the characterization of fatigue failure data. The linear regression estimation (LRE), the minimum discrepancy estimation (MDE), errors-in-variables estimation (EIV) as well as the least squares estimation (LSE) are generally applied in the estimation of Weibull parameters for their simplicity, in which probability estimators play an important role. In this paper, compared with five commonly used estimators, an optimal probability estimator with the four methods for different sample sizes is obtained by Monte Carlo simulations. The optimal probability estimator shows more robustness and higher accuracy. In conclusion, an optimal probability estimator of the midpoint rank is recommended for LRE, MDE and EIV especially with small samples in practical applications. [ABSTRACT FROM AUTHOR]

Synergy theories for multi‐component agent combinations use 1‐agent dose‐effect relations (DERs), known from analyzing previous 1‐agent experiments, to calculate neither‐synergy‐nor‐antagonism combination DERs. Synergy theories are widely used in pharmacology, toxicology, and radiation biology. This article analyzes mathematical properties of one important synergy theory, proposed by John Hand in a little‐known article published in 2000 and here called Hand Incremental Effect Additivity (HIEA). In 2018, Hand's approach was reinvented in a radiobiology study that inadvertently overlooked his paper. We carefully state the assumptions required for mathematically rigorous development of HIEA and other synergy theories. Under these assumptions, studying synergy/antagonism between any number of agents can be done on a single 2d plot. We show that HIEA combination DER is in general not well‐defined in that it can "blow up" at finite total dose. We also formulate necessary and sufficient conditions on 1‐agent DERs preventing such pathology. Using weighted harmonic means, we study the betweenness property of HIEA synergy theory and demonstrate that Hand's combination DER has a systematic tendency for betweenness violation. On the positive side, we introduce the concept of a strongly dominant agent and show that the presence of such an agent ensures the betweenness property. We show also that the betweenness property holds for another major synergy theory, Loewe–Berenbaum Additivity. Our emphasis in this article on synergy theories that can handle any number of agents was motivated by applications to the study of toxic effects of galactic cosmic rays on astronauts during interplanetary travel. [ABSTRACT FROM AUTHOR]

Abstract The Weibull distribution is the most applied model in reliability field for lifetime analysis. The Weibull location parameter, characterizing the minimum possible life, plays a significant role in engineering applications. In this paper, we consider the interval estimation on the location parameter when the product’s lifetime follows the three-parameter Weibull distribution with a known shape parameter. A novel approach based on the relationship between the minimum order statistics, the location parameter, and the sample size is developed to construct confidence intervals for the Weibull location parameter. Thereafter, we compare it with other two interval estimation approaches by the performances of the coverage probability and the average length via simulations and a real application. The results show that the proposed method outperforms the pivot quantity (PQ) method and the bias-corrected and accelerated (Bca) bootstrap method in small and medium samples in terms of coverage probability. [ABSTRACT FROM AUTHOR]

Welding is prone to several defects. To test the fatigue properties of the welded defective joints of high-speed rail bogies, SMA490BW steel cruciform welded joints were employed with artificial defects treatment. Consequently, fatigue tests were conducted on the specimens. Fatigue fracture morphology was studied via scanning electron microscopy. The ABAQUS (version 2022) finite element software was used to calculate the stress distribution and concentration factor of cruciform welded joints with defects. The results show that the fatigue limits of 1 and 2.4 mm defect specimens were approximately 57.2 and 53.75 Mpa, respectively. Furthermore, the stress concentration factor of no, 1 mm, and 2.4 mm defects were 2.246, 4.441, and 6.684, respectively, indicating that the stress concentration factor of 1 and 2.4 mm defects increased by 98 and 198%, respectively, with respect to the no-defect case. [ABSTRACT FROM AUTHOR]

The most applied principles for parameter estimation are maximum likelihood and least square error. This paper presents a new principle with regard to the parameter estimation of the three-parameter Weibull distribution. By transforming the cumulative distribution function, constructed is a mapping from the value of the random variable and its corresponding cumulative distribution probability to the scale parameter. The scale parameter estimated by such a mapping is the random variable value and the corresponding cumulative distribution probability dependent when the shape parameter and/ or location parameter applied in the mapping is subject to error. Given a set of random variable values or a set of sample values, a larger error in the shape/location parameter brings about larger differences between the scale parameter values obtained with the individual random variable values or sample values, respectively. Based on such a causal relationship between the discrepancy and the shape/ location parameter value applied in the mapping relation, a new parameter estimation method is proposed. For the Weibull distribution parameter estimation according to a set of sample values, the right shape parameter and location parameter are those minimizing the discrepancy between the scale parameter values obtained with the individual sample values, respectively. Case studies demonstrate that the proposed method outperforms the maximum likelihood method and the Weibull plot-based least squares method. [ABSTRACT FROM AUTHOR]

It has been previously noted that the development of aerospace material technology and breakthroughs are inseparable when obtaining great achievements in the aerospace industry. Materials are the basis and precursor of modern high technology and industry. As one of the most powerful aluminium alloys, 7050 is widely used in the aerospace field. In this manuscript, the vibration fatigue behaviour of aircraft aluminium alloy 7050 is studied based on experiments. A vibration fatigue experiment and the traditional fatigue testing of aluminium alloy 7050 were performed. We found that there was an extreme difference between the vibration fatigue and the traditional fatigue curves. In addition, the experimental end criteria for the vibration fatigue experiment of aluminium alloy 7050 was obtained from the acceleration reduction and the frequency reduction value. For the acceleration experimental end criterion, 2% was the acceleration reduction value for the vibration fatigue experimental end criteria of aluminium alloy 7050. For the frequency experimental end criterion, 2% was the frequency reduction value for the vibration fatigue experimental end criteria of aluminium alloy 7050. [ABSTRACT FROM AUTHOR]

The three-parameter Weibull distribution is popular in reliability analysis. However, in the context of a small sample size, the issue of parameter estimation of the three-parameter Weibull distribution is difficult to address. If only a small sample size is available, a reasonable method is to empirically determine the shape parameter, and the emphasis is placed on location parameter estimation. This paper presents a theoretical model to establish the relationship between the location parameter, the minimal sample value, and the sample size. Moreover, an iterative method is proposed to estimate the Weibull location parameter and scale parameter with an empirical value for the shape parameter. Compared with the maximum likelihood method (MLE), the Weibull plot with the sample correlation coefficient and TL-moment, the proposed method can more effectively estimate the parameters of the three-parameter Weibull distribution. [ABSTRACT FROM AUTHOR]

• A determination of the initial crack size of notched members has been presented. • The initial crack size is a function of fatigue life and fatigue notch factor. • This model can be extended to members weakened by geometric discontinuities. The precise definition of initial crack size applicable to fracture mechanics is crucial for predicting the total fatigue life of structural components. Given that the demarcation between crack formation and crack propagation depends not only on the material but also on the stress level, theoretical and experimental procedures for defining the crack boundary point are developed. Underlying the procedure is that the designed notched members have the same local stress distribution as the structure. Consequently, the fatigue life and initial crack size of S355J2 steel notched components with different scales but similar stress fields were predicted and compared with experimental data. Results show that fatigue life predictions fall within ±2 factor band, and the crack initiation size obtained by AM is closest to the experimental results, with a difference of less than 30.2%, which proves that the approach of treating the initial crack size as a function related to fatigue life and fatigue notch factor is reasonable. [ABSTRACT FROM AUTHOR]

An "index stress" (a constant amplitude cyclic stress) is introduced to characterize the scatter of the fatigue life under a variable amplitude load history. It is defined as a fatigue damage weighted average of the amplitudes of the individual stress cycles in a variable amplitude load history. The fatigue test results show that the scatter of fatigue life under variable amplitude load histories can be well characterized by such defined index stress. For probabilistic fatigue life prediction and failure probability estimation, a multiple-site damage structural part is taken as a series system, and the total probability theorem is applied to reflect the effect of load history uncertainty on failure probability. [ABSTRACT FROM AUTHOR]

Generalized reliability models and failure rate models of mechanical systems are developed in this paper according to the system working mechanism, which take the design parameters as input. The models consider strength degradation and imperfect maintenance. Besides, the models take into account the failure correlation caused by homologous load effect and the maintenance correlation owing to group maintenance. Unlike traditional reliability models, the models do not rely on empirical assumptions when considering failure correlation and maintenance correlation and have clear physical meaning. Moreover, the correctness and effectiveness of the models are verified by Monte Carlo simulations. Finally, the influences of failure correlation and maintenance correlation on generalized reliability, the influences of failure correlation on maintenance correlation, and the influences of maintenance correlation on failure correlation are analyzed via numerical examples. The results show that failure correlation and maintenance correlation have great influences on generalized reliability, and the interaction between the two correlation shows obvious time-varying characteristics. [ABSTRACT FROM AUTHOR]

For structural performance functions with characteristics of multivariable, non-normality, small failure probability and nonlinearity, it is usually difficult to pursue satisfactory accuracy by means of traditional probabilistic methods such as first-order reliability method and second-order reliability method. According to the idea of adaptive subdivision, a backward recursive method based on the universal generating function is suggested for structural reliability calculation. In the sensitive region, the variable space is subdivided partially, the discrete interval length is reduced, and the random variables are discretized nonuniformly and adaptively by the backward recursion operation. Compared with the current method of forward recursion operator and the corresponding similar items merging operation, the backward recursion operator can not only avoid low accuracy owing to subdividing the state combinations in the sensitive region, but avert the high cost of calculation owing to merging state combinations in the nonsensitive region of the variable space as well. Three examples are presented to demonstrate the rationality of the backward recursive algorithm. The results indicate that the accuracy of the proposed method is significantly higher than that of traditional methods, and the computational efficiency of the proposed method meets the engineering requirement. The research work provides a new path for reliability calculation with consideration of complex performance functions. [ABSTRACT FROM AUTHOR]

Objectives. To measure changes in the contraceptive methods used by Title X clients after implementation of Delaware Contraceptive Access Now, a public–private initiative that aims to increase access to contraceptives, particularly long-acting reversible contraceptives (LARCs). Methods. Using administrative data from the 2008–2017 Family Planning Annual Reports and a difference-in-differences design, we compared changes in contraceptive method use among adult female Title X family planning clients in Delaware with changes in a set of comparison states. We considered permanent methods, LARCs, moderately effective methods, less effective methods, and no method use. Results. Results suggest a 3.2-percentage-point increase in LARC use relative to changes in other states (a 40% increase from baseline). We were unable to make definitive conclusions about other contraceptive method types. Conclusions. Delaware Contraceptive Access Now increased LARC use among Title X clients. Our results have implications for states considering comprehensive family planning initiatives. [ABSTRACT FROM AUTHOR]

This paper develops an improved dynamic reliability model for compressor rotor system, defined as a “unconventional active system” here. First, regarding to the variety of system-component connections, system specific reliability modeling technique is presented, in which the stress and strength are both nonnegative stochastic processes. The new model fully considers the load characteristics of rotor blades, and inherently embodied the effect of the statistical dependence between the failures of the rotor blades. Then, calculated by the new model, the relationship between reliability and time, and that between the hazard rate and time, for a compressor rotor system are discussed, respectively. Comparing to the traditional series system reliability model, the new system reliability model developed in this paper has higher accuracy for compressor rotor system, since the traditional models neglect the difference between compressor rotor system and traditional active system. Moreover, in order to master the cruise characteristics of the aero-plane during reliability analysis of its compressor rotor blade set, a flight cruise is separated into several stages based on the value of Mach number and its change rate, and a subsection solution method is innovatively proposed accordingly. At the end of the paper, a certain cruise of fighter plane is analyzed to verify the accuracy of the new method. The results show that, as to a flight cruise with different stages, the new method is basically reasonable to most of the load histories, especially for the situation with impact loads existing. [ABSTRACT FROM AUTHOR]

In engineering practice, it is generally accepted that most of components are subjected to multiaxial stress‐strain state. To analyse this complicated loading state, different types of specimens of 2A12 (2124 in the United States) aluminium alloy were tested under multiaxial loading conditions and a new multiaxial fatigue analysis method for the state of three‐dimensional stress and strain is proposed. Elastic‐plastic finite element method (FEM) and a proposed vector computing method are used to describe the loading state at the critical point of specimen, by which the parameter ΓT is calculated at the new defined subcritical plane to consider the effect of additional cyclic hardening. Meanwhile, the principal equivalent strain is still calculated at the traditional critical plane. The new damage parameter is composed of different process parameters, by which the dynamic path of strain state, including loading environments and material properties, are fully considered in one loading cycle. According to experimental verifications with 2A12 aluminium alloy, the results show that the proposed method shows satisfactory, accurate, and reliable results for multiaxial fatigue life prediction in the state of three‐dimensional stress and strain. [ABSTRACT FROM AUTHOR]

Surrogate models have been widely adopted for reliability analysis. The common approach is to construct a series of surrogates based on a training set and then pick out the best one with the highest accuracy as an approximation of the time-consuming limit state function. However, the traditional method increases the risk of adopting an inappropriate model and does not take full advantage of the data devoted to constructing different surrogates. Furthermore, obtaining more samples is very expensive and sometimes even impossible. Therefore, to save the cost of constructing the surrogate and improve the prediction accuracy, an ensemble strategy is proposed in this paper for efficiently analyzing the structural reliability. The values of the weights are obtained by a recursive process and the leave-one-out technique, in which the values are updated in each iteration until a given prediction accuracy is achieved. Besides, a learning function is used to guide the selection of the next sampling candidate. Because the learning function utilizes the uncertainty estimator of the surrogate to guide the design of experiments (DoE), to accurately calculate the uncertainty estimator of the ensemble of surrogates, the concept of weighted mean square error is proposed. After the high-quality ensemble of surrogates of the limit state function is available, the Monte Carlo method is employed to calculate the failure probabilities. The proposed method is evaluated by three analytic problems and one engineering problem. The results show that the proposed ensemble of surrogates has better prediction accuracy and robustness than the stand-alone surrogates and the existing ensemble techniques. [ABSTRACT FROM AUTHOR]

Background: Late-life depression is a great burden of public health. Previous studies reported that physical activity is associated with reduced depressive symptoms among older adults, while the competing nature of physical activity and sedentary behaviors has been largely neglected in studies. We aimed to examine the associations of replacing sedentary behaviors with walking/bicycling or moderate-to-vigorous physical activity (MVPA) with depressive symptoms in older adults.Methods: A cross-sectional analysis was conducted among 8374 older adults (60 years or older) included in the National Health and Nutrition Examination Survey (NHANES), 2007-2016. The Global Physical Activity Questionnaire was used to measure self-reported time for sedentary behaviors, walking/bicycling, and MVPA. The 9-item Patient Health Questionnaire was used to measure depressive symptoms (including overall, somatic, and cognitive). Z-scores were created for depressive symptoms. Isotemporal substitution models using multivariable linear regression were applied to examine the associations of sedentary behaviors, walking/bicycling, and MVPA with z-scores of depressive symptoms.Results: Replacing 30 min/day sedentary behaviors with 30 min/day of MVPA (beta (β) = -0.10, 95% confidence interval (CI): -0.14, -0.06) or 30 min/day of walking/bicycling (β = -0.04, 95% CI: -0.06, -0.02) was associated with lower z-score for depressive symptoms. Replacing 30 min/day of walking/bicycling for 30 min/day of MVPA was associated with lower z-score for depressive symptoms (β = -0.06, 95% CI: -0.10, -0.02).Limitations: A cross-sectional study design precludes causal inferences.Conclusion: Replacing sedentary behaviors with walking/bicycling or MVPA is associated with lower depressive symptoms among older adults. Future research is expected to investigate the effectiveness of physical activity on prevention and treatment of late-life depression. [ABSTRACT FROM AUTHOR]

How to quantitatively analyze the transition size and establish a total life model has always been a research topic. Crack transition size plays the role of the divider of crack initiation and propagation phases, and the total fatigue life is in the treatment of the summation of fatigue initiation and propagation periods. In this article, a unified model of combination of the corrected local stress (strain) method with the concept of fracture mechanics is applied to estimate the total fatigue life of a notched member and to validate the predictions proposed in this paper, which is compared with the experimental tests, and the results showed good consistency for the notched structure of a certain aluminum alloy. [ABSTRACT FROM AUTHOR]

A three‐parameter Weibull small sample aggregation method is proposed to address the problem of small sample fatigue data in practical engineering. First, based on the empirical assumption that the shape parameter is a constant and data equivalent conversion and aggregation, the small sample fatigue life data are converted into "equivalent large samples." Second, through the linear relationship between logarithmic scale parameter and stress, an iterative procedure is established to estimate the scale parameters of small sample data. At the same time, the moment and rank estimation methods are used to solve the location parameters quickly. Finally, P–S–N curves with different survival rates are given, and a 7‐series aluminum alloy is selected to verify the correctness and reliability of the method proposed in this study. The results show that the predicted life obtained by the method still has high accuracy under a high survival rate, which can provide a theoretical basis for solving practical engineering problems. Highlights: A three‐parameter Weibull small sample aggregation method is proposed.The WSSA program is used to estimate the P–S–N curve of small sample data.The fatigue data of aluminum alloys verify the effectiveness of this method. [ABSTRACT FROM AUTHOR]

With the rapid development of smart manufacturing, data-driven deep learning (DL) methods are widely used for bearing fault diagnosis. Aiming at the problem of model training crashes when data are imbalanced and the difficulty of traditional signal analysis methods in effectively extracting fault features, this paper proposes an intelligent fault diagnosis method of rolling bearings based on Gramian Angular Difference Field (GADF) and Improved Dual Attention Residual Network (IDARN). The original vibration signals are encoded as 2D-GADF feature images for network input; the residual structures will incorporate dual attention mechanism to enhance the integration ability of the features, while the group normalization (GN) method is introduced to overcome the bias caused by data discrepancies; and then the model is trained to complete the classification of faults. In order to verify the superiority of the proposed method, the data obtained from Case Western Reserve University (CWRU) bearing data and bearing fault experimental equipment were compared with other popular DL methods, and the proposed model performed optimally. The method eventually achieved an average identification accuracy of 99.2% and 97.9% on two different types of datasets, respectively. [ABSTRACT FROM AUTHOR]

The folding wing mechanism is essential for the normal flight of an aircraft, and it is necessary to evaluate the reliability of its deployment performance to ensure the long-term stable operation of the aircraft. In this study, a deployment dynamic model of the folding wing mechanism was developed and solved, and the essential factors affecting the deployment performance of the folding wing were analysed. The reliability evaluation models of the folding wing deployment performance were then presented for constant and non-constant random variable distribution parameters. Finally, the proposed improved AK-IS method was used to calculate the reliability of the deployment performance under the above two conditions. Through validation and analysis of the four cases, the results show that the improved AK-IS method is more efficient than the original AK-IS method, with guaranteed computational accuracy. Compared with the Monte Carlo Simulation, the improved AK- IS method also shows higher efficiency and good robustness in solving engineering problems, such as the reliability evaluation of deployment performance; thus, the proposed method can support the reliability evaluation of similar deployment mechanisms. [ABSTRACT FROM AUTHOR]

• Bert is embedded into the federated learning framework with C-S architecture. • Federated Bert Network integrates an improved local-model aggregation algorithm. • Length Alignment Algorithm adapts multi-attribute time series to batch calculating. • Our model is superior in cross-lingual verification and privacy data protection. Online signature verification has a great challenge due to the poor performance of deep learning techniques on cross-lingual datasets under privacy constraints. In this paper, we propose a novel Federated Bert Network (FBN) by embedding the Bidirectional Encoder Representations from Transformers (Bert) into a Federated Learning (FL) framework with client-server architecture. A new Length Alignment Algorithm is employed to unify the signature pairs' sequence length, and the input representations are fed into the different clients to complete the independent learning of local-models. In addition, the server (coordinator) uses the improved Federated Average Algorithm with Reward-Punishment Mechanism (FedAvgRP) to aggregate these local-models and further generate a global-model. After multiple iterations, the optimal model can be obtained and cross-tested on four datasets (SVC 2004, MCYT-330, BioecurID, and Ours) with skilled forged (random forged) EERs of 7.65% (4.76%), 10.73% (8.46%), 10.09% (7.13%), and 8.28% (5.74%), respectively, far higher than that of the independent learning of state-of-the-art methods. Compared with the domain adaptation and improved FL models, our FBN model performs best in random and skilled forgery scenarios. Moreover, the FedAvgRP algorithm helps our model maintain high performance in the face of data attacks. [ABSTRACT FROM AUTHOR]

Handwritten signature has been regarded as one of the most accepted and practical means of person verification since ancient times. Unlike existing methods to trace the signer only considering a single spatial or temporal information, in this paper, we propose to combine two forms of signature data (stroke images and sensor signals) to realize person verification using the novel Fusion Triplet Supervised Network (fuseTSN). First, the Electronic Handwritten Signature Acquisition System 1.0 (EHS-AS 1.0) connected to the Wacom tablet is developed to construct a synchronous static–dynamic Chinese signature dataset (SynCS) and to transform existing dynamic signature datasets into static–dynamic datasets. Then, the hybrid feature extractor (ResCNN-BiLSTM with attention) as the backbone is embedded into the fuseTSN model, mapping the images and time-series signal into a common hyperspace. Furthermore, the similarity of the input [Anchor, Positive, Test] is measured to produce the final output. Finally, the proposed fuseTSN is tested on three public datasets and also evaluated on our SynCS dataset comprised of 24000 unique triplet label samples. The results show that the accuracy of the fuseTSN model is at least 5.01% higher than that of a unimodal system with only stroke image or sensor data on the SynCS dataset and outperforms the current state-of-the-art multimodal methods for writer-independence (WI) verification on public datasets. In addition, we present the fuseTSN's reliable judgment basis for spatial strokes in the heat-map and further find that the combination of time attributes (OA and OE) can significantly improve the model performance. • An Electronic Handwritten Signature Acquisition System is developed based on the Wacom tablet. • The Synchronous Static-dynamic Chinese Signature Database is created, called SynCS. • A novel Fusion Triplet Supervised Network is proposed to mine the potential relationship between spatio-temporal data. • The key features of spatio-temporal signals learned by the fusion feature extractor are visualized. [ABSTRACT FROM AUTHOR]

The gear transmission system is a typical time-domain series system, and its fatigue reliability evaluation under variable amplitude loading has long attracted the interests from scholars. The widely used Monte Carlo (MC) method to evaluate the reliability of a system with material and load uncertainties is time consuming, especially when used in combination with a fatigue analysis software. Concerning this problem, this paper proposes a “deterministic damage-random threshold (DDRT)” reliability model. The model converts the randomness from damage to the threshold, thus saving time because only the median damage and the damage for key reliability of each fatigue part are required in reliability evaluation. Based on this model, a reliability calculation flow of a gear transmission system is proposed considering the time-domain characteristic of gears. Finally, the model is verified by numerical examples and the fatigue test data of gears. [ABSTRACT FROM AUTHOR]

This paper presents an optimization method for gear processes; through this method, the most worth optimized processes can be obtained and optimized, thus improving the reliability and supportability of gear products. Firstly, the POPN (Process Optimization Priority Number) analysis method considering the current process level and the process improvement cost is proposed with reference to the RPN (Risk Priority Number) analysis method to obtain the most worth optimized processes. Due to the fact that the unreasonable weight distribution of importance (I), changing difficulty (C), rationality (R), and detective difficulty (D) still exists in the POPN analysis, then combining the POPN analysis method and the AHP (Analytic Hierarchy Process)-fuzzy comprehensive evaluation method to evaluate and rank the FPOPN (fuzzy POPN) level of each process, the higher the FPOPN level is, the more the process should be optimized. Finally, according to the evaluation results, some processes with high FPOPN level are optimized and the optimal parameters' combination of these processes is obtained through the tests based on the Taguchi method. A detailed optimization example is also given from the beginning to end in accordance with the above methods, and compared with the original process gears, the optimized gears have a big increase in gear performance through the above optimization method. [ABSTRACT FROM AUTHOR]

Abstract A failure analysis was performed to determine the causes of a crack on a high-speed train bolster, which was observed after an accelerated corrosion-fatigue test. The nominal stress method was used to evaluate the crack initiation life. The crack is not the result of a deficient design or geometry defects, for the theoretical lifetime of the bolster is more than 1 × 107 load cycles. The fracture surface was observed by the scanning electron microscope, and the crack source was determined to be the micro-holes caused by welding defects. The fracture mechanics method was employed to examine the crack propagation life, and it only occupied about 0.55% of the whole test time. Thus, after operating for 10 years, this bolster could provide safe service for another 20 years. Meanwhile, advanced welding technology or more welding inspection is suggested to prevent and detect the similar cracks. Highlights • The crack initiation life was evaluated to exclude the possibility of deficient design. • The micro-holes caused by the deficiencies in welding procedure were determined as the crack source. • The crack propagation life calculated by the fracture mechanics method only occupied about 0.55% of the whole test time • This bolster could safely operate for another 20 years, but more welding inspection prior to employment are recommended. [ABSTRACT FROM AUTHOR]

For a period of mission time, only zero‐failure data can be obtained for high‐quality long‐life products. In the case of zero‐failure data reliability assessment, the point estimates and confidence interval estimates of distribution parameters cannot be obtained simultaneously by the current reliability assessment models, and the credibility of the assessment results may be reduced if they are obtained at the same time. A new model is proposed for consistency problem in this paper. In the proposed model, the point estimates of reliability can be obtained by the lifetime probability distribution derived from matching distribution curve method, while the confidence interval estimates of reliability can be obtained by using new samples generated from the lifetime probability distribution according to parameter bootstrap method. By analyzing the zero‐failure data of the torque motors after real operation, the results show that the new model not only meets the requirements of reliability assessment but also improves the accuracy of reliability interval estimation. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Astaxanthin was extracted from an oilseed via ethanol-modified SC-CO 2 first time. • Ethanol-modified SC-CO 2 performed better than accelerated solvent extractions. • Ethanol concentration did not have any effect at lower pressures (30 MPa). • Oils extracted with ethanol-modified SC-CO 2 had the highest antioxidant activity. Abstract Natural astaxanthin, a high-value carotenoid that is currently extracted mainly from marine organisms, was extracted from engineered camelina seed using ethanol-modified supercritical carbon dioxide (SC-CO 2) for the first time, and compared with hexane and accelerated solvent extraction using hexane and ethanol. Response surface methodology (RSM) based on central composite rotatable design was employed to investigate the effect of pressure (30–45 MPa), temperature (40–60 °C), and ethanol concentration (10–35%, w/w). RSM-optimized conditions (41.6 MPa, 36.6 °C and 42.0% ethanol concentration) predicted the astaxanthin concentration as 437 μg/g oil, whereas the actual concentration was 421 ± 14 μg/g oil. Astaxanthin concentration in accelerated solvent extracted oil was significantly lower than that in ethanol-modified SC-CO 2 - and hexane-extracted oils (P < 0.05). Oils extracted with ethanol-modified SC-CO 2 had the highest antioxidant activity. Results indicated that ethanol-modified SC-CO 2 extraction method can be successfully used as a green method to extract astaxanthin from high oil feedstocks. [ABSTRACT FROM AUTHOR]

Traditional reliability models of the gear system either simplify the gear system unreasonably or are too complicated to be applicable for some gear systems. Therefore, a reliability model of the gear system considering statistically dependent failure based on the theory of the order statistics is developed in this paper. Firstly, the gear bending fatigue test of small sample is implemented to obtain the P-S-N curves that are fitted by using the least square method and the linear regression method of the statistical parameters under the test stress levels. Then, according to stress-strength interference theory and the theory of the order statistics, the reliability models considering the number of load cycles from a gear to gear system are built, which indicates clear modeling process of the gear system. Finally, the proposed reliability model of gear system is validated by using the Monte Carlo Simulation (MCS) and the system reliability under special load history is analyzed qualitatively. [ABSTRACT FROM AUTHOR]

Conventional reliability models of planetary gear systems are mainly static. In this paper, dynamic reliability models and random lifetime models of planetary gear systems are developed with dynamic working mechanism considered. The load parameters, the geometric parameters, and the material parameters are taken as the inputs of the reliability models and the random lifetime models. Moreover, failure dependence and dynamic random load redistributions are taken into account in the models. Monte Carlo simulations are carried out to validate the proposed models. The results show that the randomness of the load distribution is obvious in the system working process. Failure dependence has significant influences on system reliability. Moreover, the dispersion of external load has great impacts on the reliability, lifetime distribution, and redundancy of planetary gear systems. [ABSTRACT FROM AUTHOR]

This paper presents a study on the fatigue life prediction of notched fiber-reinforced 2060 Al-Li alloy laminates under spectrum loading by applying the constant life diagram. Firstly, a review on the state of the art of constant life diagram models for the life prediction of composite materials is given, which highlights the effect on the forecast accuracy. Then, the fatigue life of notched fiber-reinforced Al-Li alloy laminates (2/1 laminates and 3/2 laminates) is tested under cyclic stress, which has different stress cycle characteristics (constant amplitude loading and Mini-Twist spectrum loading). The introduced models are successfully realized based on the available experimental data of examined laminates. In the case of Mini-Twist spectrum loading, the effect of the constant life diagram on the life prediction accuracy of examined laminates is studied based on the rainflow-counting method and Miner damage criteria. The results show that the simple Goodman model and piecewise linear model have certain advantages compared to other complex models for the life prediction of notched fiber metal laminates with different structures under Mini-Twist loading. From the engineering perspective, the S-N curve prediction based on the piecewise linear model is most applicable and accurate among all the models. [ABSTRACT FROM AUTHOR]

Considering the fuzziness of load, strength, operational states, and state probability, reliability models of multistate systems are developed based on universal generating function (UGF). The fuzzy UGF of load and the fuzzy UGF of strength are proposed in this paper, which are used to derive the fuzzy component UGF and the fuzzy system UGF. By defining the decomposition operator and the inner product operator, failure dependence and effects of multiple load applications are taken into account in the established reliability models. Moreover, dynamic fuzzy reliability models of multistate systems are constructed considering the strength degradation of components. The results show that failure dependence and the effects of multiple load applications have significant impacts on system reliability, which considerably decrease system reliability and increase the fuzziness of system reliability under low performance requirements. Besides, in the dynamic reliability analysis of multistate systems, strength degradation dependence could lead to large computational error. [ABSTRACT FROM AUTHOR]

Time-dependent statistical characteristics of load process and strength degradation process are critical to lifetime distribution of series mechanical systems. Conventional rain-flow counting method for lifetime distribution estimation has limited practical application due to its strict requirement for statistical properties of load process. Besides, dynamic interaction between load process and strength degradation process results in strength degradation path dependence (SDPD). SDPD and failure dependence of components jointly bring considerable difficulties in prediction of system lifetime distribution and system residual lifetime distribution. To address these problems, reliability-based analytic models for estimation of whole lifetime distribution and residual lifetime distribution of series mechanical systems under random load are developed in this paper, which take the time-dependent statistical parameters of load process and strength degradation process as the input of the models. Furthermore, SDPD and failure dependence of components are taken into account in the proposed models in an explicit mathematical expression. The results show that SDPD, failure dependence of components, and initial strength dispersion have significant influences on system lifetime distribution. [ABSTRACT FROM AUTHOR]

To investigate the influence of surface features, in the form of pits, on the wear resistance of grey cast iron (GCI), a finite element model of the pin-on-disc friction system, with pits distributed in a curved radial direction, was developed using APDL programming and the tribological behavior of textured surfaces was studied. The influence of relative rotation direction between the disc and the pin on the thermal behavior of the friction system under dry wear conditions was researched. GCI and C30E steel samples with pit textured surfaces were manufactured using laser marking equipment and tested using a tribology wear testing rig. The mass losses were measured and the worn surfaces were characterized. The influence of different rotation directions on the tribological behavior of the pit textured surfaces was also investigated. The simulation and test results revealed that rotation direction was a crucial parameter in determining the tribological behavior of surfaces with these features, regardless of the material. Under the conditions tested, when the pin rotated anticlockwise, the samples showed better friction and wear behavior than when the pin rotated clockwise. These results can provide important guidance for the optimization of the design of heavy-load brake systems and other similar applications. [ABSTRACT FROM AUTHOR]

Due to inevitable manufacturing and installation errors, there are many problems of unequal load sharing in planetary gear train. In this paper, a model is established to predict the reliability of helicopter planetary gear train under the condition of partial load. Firstly, the structure of gear system and partial load state are analyzed in detail, and the load histories of each gear are transformed into equivalent constant amplitude load spectrums to be as the load input variable for reliability model. At the same time, a tooth bending fatigue test is carried out with specific gears, and the statistical results of test data are as the strength input variable for reliability model. Then, according to partial load characteristics of the gear system, the reliability model is established based on the concept of minimum order statistic. Finally, the bad influence of unequal load sharing on planetary gear train is shown by prediction result and the reliability model is verified through a statistical analysis method of random censored data. [ABSTRACT FROM AUTHOR]

The method and effects of extracting information from different fatigue test data were analyzed and compared according to the test data in engineering in this paper. By probability statistical analysis, the life data of ignored censored data were collected and analyzed to fit the distribution types and P-S-N curves. Otherwise, the life data including censored data were estimated by maximum likelihood estimation and K-S test. It is shown that the practice of simply ignoring censored data will underestimate the fatigue performance of the test sample in different degrees after analysis and comparison of the two results. Therefore, according to different types of test data, the influence of censored data should be considered fully in order to select the appropriate treatment method. Censored data in engineering usually should not be ignored. [ABSTRACT FROM AUTHOR]

Based on Monte-Carlo simulation, a new method is proposed to measure and estimate probabilistic fatigue limits, particularly for the situation with large scattering data. Firstly, the appropriate distribution was determined from four possible distributions by checking its consistency with the fatigue physics and checking its fit goodness. Then, the test procedure of this method was illustrated, which could use variable stress step sizes regardless of pairing observations. Finally, the method was applied to determine the fatigue limit of A7N01S-T4 aluminum. The results exhibited that this method was more flexible in test and could determine fatigue limit using fewer specimens. [ABSTRACT FROM AUTHOR]

Former smokers are at increased risk for cardiovascular disease. We hypothesized that dietary aronia polyphenols would reduce biomarkers of cardiovascular disease risk, inflammation, and oxidative stress in former smokers. We also determined the extent these effects were associated with polyphenol bioavailability. A 12-week, randomized, placebo-controlled trial was conducted in 49 healthy adult former smokers (n = 24/placebo, n = 25/aronia) to evaluate if daily consumption of 500 mg aronia extract modulated plasma lipids, blood pressure, biomarkers of inflammation and oxidative stress, and lipid transport genes of peripheral blood mononuclear cells. The primary outcome was change in low-density lipoprotein cholesterol (LDL-C) from baseline, and multivariate correlation analysis was performed to determine if changes in lipids were associated with urinary polyphenol excretion. Aronia consumption reduced fasting plasma total cholesterol by 8% ( P = .0140), LDL-C by 11% ( P = .0285), and LDL receptor protein in peripheral blood mononuclear cells ( P = .0036) at 12 weeks compared with the placebo group. Positive changes in the urinary polyphenol metabolites peonidin-3- O -galactoside, 3-(4-hydroxyphenyl) propionic acid, and unmetabolized anthocyanin cyanidin-3- O -galactoside were associated with lower plasma total cholesterol and LDL-C in the aronia group. Aronia consumption did not change blood pressure or biomarkers of inflammation and oxidative stress. Aronia polyphenols reduced total and LDL-C in former smokers but did not improve biomarkers of oxidative stress and chronic inflammation. The cholesterol-lowering activity of aronia extract was most closely associated with urinary levels of cyanidin-3- O -galactoside and peonidin-3- O -galactoside, its methylated metabolite. This trial was registered at ClinicalTrials.gov as NCT01541826 . [ABSTRACT FROM AUTHOR]

A single-dose pharmacokinetic trial was conducted in 6 adults to evaluate the bioavailability of anthocyanins and colonic polyphenol metabolites after consumption of 500 mg aronia berry extract. UHPLC-MS methods were developed to quantitate aronia berry polyphenols and their metabolites in plasma and urine. While anthocyanins were bioavailable, microbial phenolic catabolites increased ∼10-fold more than anthocyanins in plasma and urine. Among the anthocyanins, cyanidin-3- O -galactoside was rapidly metabolized to peonidin-3- O -galactoside. Aronia polyphenols were absorbed and extensively metabolized with t max of anthocyanins and other polyphenol catabolites from 1.0 h to 6.33 h in plasma and urine. Despite significant inter-individual variation in pharmacokinetic parameters, concentrations of polyphenol metabolites in plasma and urine at 24 h were positively correlated with total AUC in plasma and urine (r = 0.93, and r = 0.98, respectively). This suggests that fasting blood and urine collections could be used to estimate polyphenol bioavailability and metabolism after aronia polyphenol consumption. [ABSTRACT FROM AUTHOR]

Time-dependent multi-configuration is a typical feature for mechanical systems such as gear trains and chain drives. As a series system, a gear train is distinct from a traditional series system, such as a chain, in load transmission path, system-component relationship, system functioning manner, as well as time-dependent system configuration. Firstly, the present paper defines time-domain series system to which the traditional series system reliability model is not adequate. Then, system specific reliability modeling technique is proposed for gear sets, including component (tooth) and subsystem (tooth-pair) load history description, material priori/posterior strength expression, time-dependent and system specific load-strength interference analysis, as well as statistically dependent failure events treatment. Consequently, several system reliability models are developed for gear sets with different tooth numbers in the scenario of tooth root material ultimate tensile strength failure. The application of the models is discussed in the last part, and the differences between the system specific reliability model and the traditional series system reliability model are illustrated by virtue of several numerical examples. [ABSTRACT FROM AUTHOR]

• Our designed 2D representation method transforms the original time-series signature data into image data, presenting the spatial trajectory and simultaneously retaining the critical dynamic information (altitude, azimuth and pressure). • The Channel-wise Weights Learning mechanism was integrated into the deep triplet network to determine the importance of three dynamic attributes, making it an excellent help for feature extraction. • A new Triplet Supervised Network (TSN) was implemented on three databases (SVC 2004, MCYT-100, Ours), showing the high accuracy and strong generality for large-scale online signature verification. Online signature verification (OSV) as a critical link of the paperless office still has tremendous challenges. In this paper, we propose a novel Writer-Independent (WI) OSV framework that includes three parts. (1) The two-dimensional (2D) representation method is designed to transform the original time-series signature data into stroke images with dynamic-static hybrid information. (2) The Channel-wise Weight Learning (CWL) mechanism is integrated into the feature extractor to mine the potential relationship between three dynamic attributes (altitude, azimuth, and pressure). (3) A new Triplet Supervised Network (TSN) that contains three weight-shared convolution neural network (CNN) streams was provided to measure the distance of [Anchor, Positive, Test]. The experimental results show that our model has at least 1.29% accuracy improvement when confronted with skilled forgery signatures than that of other classical CNNs and 11.43% than lightweight models. Moreover, the TSN model is superior to the previous OSV algorithms in the WI pattern. [ABSTRACT FROM AUTHOR]

Fuzzy dynamic reliability models of mechanical parallel systems with respect to stress parameters and strength parameters are developed in this paper. Strength degradation path dependence (SDPD) and failure dependence of components in the system are two main problems to be addressed in developing fuzzy dynamic reliability of mechanical systems, which are taken into account in the proposed reliability models. In addition, the SDPD sensitivity function and the failure dependence sensitivity function are defined to analyze the influences of the fuzzy characteristics of stress on the effects of SDPD and failure dependence of mechanical components on dynamic reliability. The bolted joint systems for connection between launch vehicle and satellite are chosen as illustrative examples to demonstrate the proposed model. Moreover, Monte Carlo simulations are carried out to validate the effectiveness of the proposed models. The results show that SDPD and failure dependence of components have significant impacts on fuzzy dynamic reliability of mechanical systems. Besides, the influences of the fuzzy characteristics of stress on SDPD sensitivity and that on failure dependence sensitivity are different. [ABSTRACT FROM AUTHOR]

The present work aims at experimentally quantifying the effect of the process, environmental, and geometric conditions on the interlaminar tension stress (ILTS) performance of curved composite laminates. First, an innovative experimental matrix is established considering the material and process variability, environmental conditions, lay-up, thickness, radius-to-thickness ratio, defects, and thermal cycles. Subsequently, four-point bending tests are performed on the L-shaped laminated specimens. The effects of each condition on ILTS are obtained, with an interpretation of the corresponding mechanism. The results demonstrated that the material and process variability for the ILTS is about 24%. The stress of the hygrothermally aged specimens was reduced by 34.84%, but the performance was improved by 64.63% at −55 °C. Moreover, it is worth noting that, among all the design factors, the initial defects resulted in a significant stress reduction of up to 63.94%. Finally, the design allowable values under different environmental conditions were accurately calculated by the proposed method. The experimental results have been compared with corresponding observations reported in the literature, exhibiting a good agreement. Consequently, the conclusions of this study are highly useful for civil aircraft design applications. [ABSTRACT FROM AUTHOR]

Highlights: [•] The innovative idea and efficient method to quantify the failure trajectory concept. [•] Backwards statistical inference technique to fit P–S–N curve by small sample data. [•] The strategy to search the life standard deviation – stress relationship. [•] The method saves specimens, shortens test time and keeps a quite high accuracy. [•] Simple and mathematically traceable, involving no impractical assumption. [ABSTRACT FROM AUTHOR]

Highlights: [•] Stilbenes were identified in three California almond varieties. [•] Resveratrol-3-β-glucoside (polydatin) was present at 7.19–8.52μg/100g almond among Butte, Carmel, and Nonpareil varieties. [•] Stilbenes are concentrated in almond skins and easily extracted by hot-water blanching. [Copyright &y& Elsevier]

Highlights: [•] Cellular antioxidant activity assay (CAA) using oleic acid as stressor is developed. [•] Oleic acid promotes oxidative stress without causing the decrease of cell viability. [•] EGCG is the best ROS inhibitor among 16 flavonoids in CAAoleic acid assay. [•] The CAAoleic acid assay is probably more biological relevant than the CAAAAPH assay. [ABSTRACT FROM AUTHOR]

Abstract: The objective of this study is to investigate the effect of holes on the low strain rate fatigue properties of the nickel foam material and to understand the lifetime of this material which is subjected to the repeated loads. Failures of foam materials under single and repeated loads analogous to fatigue are essential to designers and users in military and aerospace structures. The material failure induced by repeated low strain rate loading becomes a critical issue because of significant loss of stiffness and compressive strength in the foam material. Testing methods to study low strain rate (that is, strain rate) fatigue are quite numerous; no single standard testing procedure is defined for studying the low strain rate fatigue property of a material. The increasing application of foam material in aerospace structures, owing to high specific stiffness and strength has attracted a great concern about the high sensitivity to low strain rate damage introduced during manufacture or in service, and the effects of such damage on structural degradation. To investigate this issue, this study sets up an experimental procedure to determine the low strain rate fatigue properties of nickel foam material. This study performs both experimental and numerical investigations to catch the low strain rate fatigue behavior of nickel foam with open-cell type. The experiments are conducted by rod up and down at the strain rate fatigue of loading. The crack length at the specific cycles are measured experimentally by taking pictures with a paper ruler attached on the surface of specimen and these values are apply to the computer simulations as crack seam model. The simulation result of stress intensity factors are compared with a well known theoretical calculation. Design life and probability of failure or survival at specified life can be calculated so that the fatigue life of nickel core material subjected to repeated low strain rate loading is predicted. [Copyright &y& Elsevier]

Abstract: Multiple site damage is the occurrence of small fatigue cracks at several sites within aging aircraft structures. Focusing on this typical structure, an analytical method for calculating the stress intensity factor of an infinite plate containing multiple hole-edge cracks was introduced in this paper. The properties of complex variable functions are used to evaluate the stress function. The approximate superposition method is applied to solve stress intensity factor problems on multiple holes. The equivalent crack is introduced to modify the method. Some numerical examples of an infinite plate containing two hole-edge cracks are examined by the method. By comparing the analytical and finite element analysis results it was realized that the analytical results are accurate and reliable. This modified analytical method is easier to apply than some traditional analytical methods and can provide stress intensity factor solutions for an infinite plate containing a random distribution of multiple hole-edge cracks. [Copyright &y& Elsevier]

Abstract: Nonalcoholic fatty liver disease (NAFLD) is the most common liver disease and its incidence is rising worldwide. We compared the antioxidant capacity of seventeen flavonoids with their inhibitory effects on oleic acid-induced triglyceride (TG) over-accumulation in HepG2 cells. The results showed significant correlations (P < 0.01) between the inhibition of intracellular TG levels and the suppression effects on reactive oxygen species. Nevertheless, the radical-reducing activities of flavonoids assessed by chemical assays (cyclic voltammetry and Folin–Ciocalteu reagent assay) were poorly correlated with their intracellular TG inhibitory effects. The relationships between structural properties of flavonoids and their inhibitory effects on TG over-accumulation were discussed. [Copyright &y& Elsevier]

The dynamic reliability model of components is developed using order statistics, and probability differential equations. The relationship between reliability and time, and that between the hazard rate and time, are discussed in this paper. First, according to the statistical meaning of random load application, the cumulative distribution function, and probability density function of equivalent load, when random load is applied at multiple times, are derived. Further, the reliability model of components under repeated random load, is developed. Then, the loading process described under a Poisson process, the dynamic reliability model of components without strength degeneration, and that with strength degeneration are developed respectively. Finally, the reliability, and the hazard rate of components are discussed. The result shows that, when strength doesn't degenerate, the reliability of components decreases over time, and the hazard rate of components decreases over time, too. When strength degenerates, the reliability of components decreases over time more obviously, and the hazard rate curve is bathtub-shaped. [ABSTRACT FROM AUTHOR]

The issue of information loss in the process of system reliability modeling through conventional load–strength interference analysis is discussed first, and the reason why it is impossible to construct dependent system reliability model simply by means of component reliability index is demonstrated. Then, an approach to modeling the reliability of dependent system with common cause failure (CCF) is presented. The approach is based on system-level load–strength interference analysis and a concept of ‘conditional failure probability of component’ as well. With the opinion that load randomness is the direct cause of failure dependence, a discrete type system reliability model is developed via the conditional component failure probability concept. At last, the model''s capabilities to estimate system reliability with CCF effect and to predict high multiplicity failure probability based on low multiplicity failure event data are proved. [Copyright &y& Elsevier]