Life Test Research Articles

Assessing the feasibility of a bowel management program for patients with neurogenic bowel function after spinal cord injury

The aim of this study was to assess the feasibility of a bowel management program for patients with neurogenic bowel function after spinal cord injury. The program is based on evidence-based nursing, expert meeting and pre-experiment construction, the construction process is standardized and scientific, and the content is comprehensive, mainly includes 4 dimensions of bowel assessment, bowel intervention, assessment indices and discharge follow-up, which were carried out at the time of admission (T1), discharge (T2) and 1 month after discharge (T3) of patients in the experimental group, while the control group used routine orthopedic bowel management, and bowel function indices, quality of life and laboratory tests were used as outcome indices, and differences in the observed indices of patients in the two groups were compared to validate the effect of the program. Compared with the control group, the incidence of bloating, constipation and fecal incontinence was significantly reduced in the experimental group, while the frequency of defecation scores, fecal character scores, Neurogenic Bowel Dysfunction scores, laboratory test results and quality of life were also effectively improved. The results also highlight the need for a large, multi-center, long-term follow-up study to validate the efficacy of this protocol to improve the feasibility of bowel management protocols for patients with neurogenic bowel function after spinal cord injury. This study provides a reference base for further exploration of bowel management in patients with neurogenic bowel function after spinal cord injury and is worthy of promotion and application in clinical practice.

Torque Loss, Survival, and Strain Distribution of Implant-Supported Prostheses with Zirconia and Cobalt–Chromium Hybrid Abutments

Background and Objectives: The manufacturing of single crowns using hybrid abutments is an alternative that may be interesting in clinical practice, combining the advantages of the different materials used in a personalized design for each case. The purpose of this in vitro study was to evaluate the torque loss, survival, reliability, failure mode, and strain distribution of implant-supported prostheses with zirconia (Zir) and cobalt–chromium (Co-Cr) hybrid abutments. Materials and Methods: Abutments were milled by CAD/CAM and divided into two groups according to the materials used, Zir and Co-Cr, and cemented on titanium bases screwed to dental implants. Monolithic zirconia crowns were cemented on the abutments. The implant/abutment/crown sets were subjected to thermomechanical cycling (n = 10) (2 Hz, 140 N, 1 × 106 cycles, immersed in water at 5–55 °C) to evaluate the torque loss. The single load to fracture test (SLF) was performed to design the loading profiles (light, moderate, and aggressive) of the step-stress accelerated life testing (SSALT) (n = 21) to evaluate the survival and reliability. The representative fractured specimens were analyzed under optical and scanning electron microscopy. The digital image correlation (DIC) (n = 1) was performed using specimens embedded in polyurethane resin models that received static point loading, and the strain distribution was analyzed. Results: There was no difference in torque loss, survival, or reliability between zirconia and Co-Cr abutments. An analysis of the fractured surfaces showed that the abutments presented the same failure mode, where the fracture probably started in the titanium base/screw. The zirconia abutment model presented only compressive strains around the implant, while the Co-Cr abutment model showed tensile and compressive strains in the middle of the implant; however, all strains were within the clinically acceptable limits. There was a strain concentration in the titanium base close to the implant platform for both groups. Conclusions: Zirconia and Co-Cr hybrid abutments presented similar torque loss, survival, reliability, and failure modes, but the abutment material influenced the strain distribution around the implant. The titanium base screw was the weakest link in the system.

Data Model Implementation of Weapon Live Test Support Asset based on DoDAF Meta Model

In order to safely and effectively conduct weapon live tests in an environment with limited human resources, it is essential to utilize a decision support system to enable quick and accurate decision-making at key stages. The role of the decision support system is to provide situational awareness information and key decision-making elements based on data acquired from test support assets, and an architecture design methodology for system implementation was proposed through prior research. In order to share heterogeneous data between multiple support assets and decision support system, research on the application of standardized data models was required. This paper proposes a method of applying the DM2(DoDAF 2.0 Meta Model) developed in the U.S. DoD considering easy connectivity between models and compatibility with future weapon system model. A case study is illustrated the feasibility of the proposed method through data modeling in ATLAS(Ammunition Transport and Loading Autonomy System), one of the support assets operated during ammunition firing test.

Analysis and applications of Nakagami constant-stress model using progressive type-II censored data

Abstract In the case of trustworthy products, accelerated life tests are crucial techniques used to gather information regarding the lifetime of the target population with a shorter time frame compared to routine investigations. The received data in higher stress levels than normal are then used to predict the reliability of the product under consideration in regular working circumstances. In this paper, the constant-stress accelerated life tests are employed when the data are obtained through a progressive Type-II censoring strategy from Nakagami populations. Besides estimating the model parameters, the reliability function under the usual use conditions is predicted using four estimation procedures. The maximum likelihood, least squares, weighted least squares and maximum product of spacing estimation approaches are utilized for estimation purposes. In addition, two interval estimation methods are considered utilizing the asymptotic features of the maximum likelihood and maximum product of spacing estimates. A simulation investigation is conducted to evaluate the efficiency of diverse point and interval estimations beneath various strategies involving sample sizes, effective number of failures, and removal designs. From a practical perspective, a pair of datasets are explored to confirm the effectiveness of the theoretical findings.

Point and interval estimation for one-shot devices under Weibull distribution with dependent failure modes using copulas

A one-shot device is a unit that performs its intended function only once. Actual lifetimes of such kind of devices cannot be observed. One can only observe if a failure occurred before or after a certain inspection time so the data is either left- or right-censored. Since one-shot devices are highly reliable products, accelerated life testing is commonly used to induce early failures. There are often more than one dependent failure modes causing the device to fail. Copula models have become one of the most popular tools for modeling dependence. In this paper, we provide statistical inference for modeling the dependence structure between failure modes in one-shot devices under constant stress accelerated life testing using copulas with Weibull marginals. The point estimates of the unknown parameters for the Weibull distribution along with the dependence parameter estimate are obtained using two estimation methods; the maximum likelihood estimation and the inference function for margins. Also, interval estimates are constructed using the asymptotic and bootstrap methods. The basic bootstrap and the studentized-t bootstrap intervals are obtained. Moreover, the survival probabilities are predicted under normal conditions. Numerical analysis including simulated data and a real life data are conducted to study the performance of the estimates.

Validating Accelerated Shelf Life Testing Methodology for Predicting Shelf Life in High-Pressure-Processed Meat Products

The shelf life of meat products is a critical factor in ensuring both consumer safety and product quality. Traditional methods for determining shelf life are labor-intensive and time-consuming, making it challenging for manufacturers to adapt to market demands. The accelerated shelf life testing (ASLT) methodology offers a viable solution by exposing products to controlled elevated conditions that simulate long-term storage, allowing for faster shelf life predictions. This study evaluates the ASLT methodology as a predictive tool for determining the shelf life of high-pressure (HPP)-treated meat products. The present study includes experiments to verify the shelf life of frankfurter-type sausages under accelerated conditions. By simulating long-term storage at elevated temperatures (4–18 °C), a kinetic model was developed to monitor spoilage bacteria growth, with validation under dynamic temperature conditions. The results indicate that the main spoilage population of frankfurter-type sausages was lactic acid bacteria (LAB), which was strongly correlated with the total mesophilic microflora of the products. The findings show that elevated storage temperatures (8 and 18 °C) provide accurate shelf life predictions, offering an efficient approach to ensure product quality and meet consumer demands.

Stability, Fat Content and Protein Content Test of Instant Powder Protein Combination of Milk, Egg Yolk and Temulawak (Curcuma xanthorrhiza Roxb.) Eggs to Prevent Stunting

Consuming foods or drinks that contain animal protein, such as milk and yolks, is one way to prevent stunting. In addition, the addition of temulawak in the formula can enhance appetite. Innovation is needed to turn milk, yolks, and temulawak into powder because their high protein content makes the products prone to spoilage. Information about the stability and content of products is very important to ensure that the products are safe for consumption. One way to determine the stability of a formulation is to conduct tests at various storage temperatures. The purpose of this research is to determine the storage stability (temperature and shelf life), fat content, and protein content of the instant powder preparation combining milk, yolk, and temulawak. Stability testing using the accelerated stability testing method or Accelerated Shelf Life Testing (ASLT) to determine shelf life. This method uses temperature variations, namely T1: refrigerator temperature 4°C ± 2°C, T2: room temperature 30°C ± 2°C, and T3: warm temperature 40°C ± 2°C for a duration of 2 weeks. The parameters used are moisture content, redispersibility time, and the pH of the preparation. Stability data analysis is calculated using the Arrhenius model and reaction order. The fat content and protein content are determined using the method outlined in the SNI-01-2970-2006 attachment for powdered milk. The research results show that the instant powder combination of milk, yolk, and temulawak has a fat content of 10.09% and a protein content of 71.07%. The stability test of the preparation conducted at storage temperatures of 4°C ± 2°C, 30°C ± 2°C, and 40°C ± 2°C, respectively, showed results based on moisture content (54 days, 26 days, 20 days), redispersibility time (371 days, 99 days, 63 days), and pH of the preparation. (247 hari, 72 hari, 47 hari). The decrease in stability is directly proportional to the increase in storage temperature. In conclusion, the instant powder combination of milk, yolk, and temulawak is stable at storage temperatures below 30°C, with a fat content of 10.09% and a protein content of 71.07%.

Inference and Optimal Design on Partially Accelerated Life Tests for the Power Half-Logistic Distribution Under Adaptive Type II Progressive Censoring

This study explores accelerated life tests to examine the durability of highly reliable products. These tests involve applying higher stress levels, such as increased temperature, voltage, or pressure, that cause early failures. The power half-logistic (PHL) distribution is utilized due to its flexibility in modeling the probability density and hazard rate functions, effectively representing various data patterns commonly encountered in practical applications. The step stress partially accelerated life testing model is analyzed under an adaptive type II progressive censoring scheme, with samples drawn from the PHL distribution. The maximum likelihood method estimates model parameters and calculates asymptotic confidence intervals. Bayesian estimates are also obtained using Lindley’s approximation and the Markov Chain Monte Carlo (MCMC) method under different loss functions. Additionally, D- and A-optimality criteria are applied to determine the optimal stress-changing time. Simulation studies are conducted to evaluate the performance of the estimation methods and the optimality criteria. Finally, real-world datasets are analyzed to demonstrate the practical usefulness of the proposed model.

A method of coating life prediction based on high temperature thermal shock life test and three-dimensional heat transfer analysis

In this study, a method for predicting the thermal shock life of coatings is proposed, and a model for predicting the thermal shock life of coatings based on high temperature thermal shock life test and three-dimensional heat transfer analysis is established. Firstly, the thermal shock life of coatings at different cooling and heating cycle temperatures is obtained through a designed thermal shock life testing device for silicide coatings at a wide-temperature range from 500℃ to 3000℃. Secondly, the actual thickness of the coating and the continuous oxidation in the thermal shock life test are taken into consideration. Based on the finite element analysis method, the three-dimensional heat transfer analysis for coatings with different oxidation thickness is carried out to obtain the average value of the maximum thermal stress range on the surface of the coating. Last, the least square method is used to process the data of the life prediction model. Then the parameters of the life prediction model are obtained based on the thermal shock life test of the coating and the average value of the maximum thermal stress range on the coating surface. It turns out that the predicted results of the thermal shock life prediction model established in this study are in good agreement with the tested results. Besides, the relative error is less than 6%. Therefore, the life prediction method proposed in this study can be used to predict the thermal shock life of silicide coatings. What’s more, the research work in this study can also provide a theoretical basis for the life prediction of coating materials.

Implantable Cardioverter-Defibrillators and Cardiovascular Resynchronization Therapy with Left Ventricular Assist Devices: A MOMENTUM 3 Trial Analysis.

The benefit of implantable cardioverter-defibrillators (ICD) and cardiovascular resynchronization therapy (CRT-D) in patients supported with a HeartMate 3 left ventricular assist device (LVAD) remains uncertain. An analysis of the MOMENTUM 3 randomized clinical trial and the first 1000 patients in the Continued Access Protocol trial. Patients were divided into three groups based on the presence of ICD and/or CRT-D: No device (n=153, 11%), ICD only (n=699, 50.4%), CRT-D (n=535, 38.6%). We assessed the association of ICD or CRT-D with overall mortality, ventricular arrhythmias (VA), rehospitalization rates, quality of life and six-minute walk test distance at 2-years of follow-up. Patients with ICD or CRT-D had similar survival to those without (HR 1.3, 95% CI 0.8-2.1, p=0.36) with no differences in rehospitalizations, quality-of-life or six-minute walk test distance. VA occurred more frequently in patients with ICD or CRT-D (HR 2.4, 95% CI 1.3-4.3, p=0.006). Compared to ICD alone, patients with CRT-D demonstrated similar survival (HR 1.1, 95% CI 0.9-1.5, p=0.36), however, had increased rates of VA (HR 1.3, 95% CI 1.0-1.7, p=0.03). There were no differences in rate of rehospitalization between those with ICD or CRT-D and those without (p=0.19) or between those with ICD and those with CRT-D (p=0.32). A propensity-matched sensitivity analysis confirmed these findings. In this post-hoc analysis of the MOMENTUM 3 trial, the presence of ICD or CRT-D at the time of HM3 LVAD implantation was associated with an increased incidence of VA but was not associated with survival, quality of life or functional capacity. Momentum 3 portfolio, NCT02224755 (Pivotal) and NCT02892955 (CAP).

Statistical Inference for Generalized Half‐Normal Model Under Step‐Stress Accelerated Life Test in the Presence of Hybrid Censoring

ABSTRACTIn this paper, we consider the problem of estimating the unknown parameters of a generalized half‐normal (GHN) distribution when lifetime data are observed from accelerated life test (ALT) experiments in the presence of hybrid censoring. To relate the lifetime of products under different stress levels, we make use of a cumulative exposure model (CEM), and obtain maximum likelihood estimates using a numerical approach and stochastic expectation–maximization (SEM) algorithm. We further obtain the expected Fisher information matrix, and use it to compute associated confidence interval estimates for the unknown parameters of the distribution. The expected Fisher information matrix is also used to select the optimal time to conduct an experiment based on three considered optimality criteria. Next, we consider independent and conditional gamma priors and obtain the associated posterior distributions for the unknown parameters. We then make use of samples generated from the posterior distributions using importance sampling and the MH algorithm to compute the Bayesian estimates under the squared error loss function. Furthermore, the highest associated posterior density interval estimates are also computed. Finally, we conduct a simulation study to evaluate the efficiency of the suggested approaches in various situations and analyze a real data set for illustration purposes.

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.

Clinical Outcomes of a New Foot-Worn Non-Invasive Biomechanical Intervention Compared to Traditional Physical Therapy in Patients With Chronic Low Back Pain. A Randomized Clinical Trial.

Randomized Controlled Trial. Chronic low back pain (CLBP) is a major public health concern that will continue to grow with the expected aging of the population. The purpose of this study was to examine the clinical effect of a personalized, home-based biomechanical intervention compared to traditional physical therapy in patients with CLBP. This was a randomized controlled trial. One-hundred and sixty-two patients were randomized in a 2:1 ratio to a home-based biomechanical intervention (HBBI, AposHealth) or traditional physical therapy (TPT), respectively. Patients were assessed at baseline and after 12weeks and 52weeks. The primary outcome measure was pain at 52weeks, using a standard Numeric Rating Scale (NRS). Secondary outcomes included pain and function metrics, quality of life and objective spatio-temporal gait test. A Linear Mixed Model assessed changes over time across all study visits. A significant reduction in NRS was found after 52weeks with a superiority effect of the HBBI arm compared to TPT (F = 13.82, P < 0.001). Patients in the HBBI arm demonstrated a marginal mean reduction of 3.5 points, from 6.2 to 2.7 (a 56% reduction), while patients in the TPT arm reported a mean decrease of 1.8 points from 6.9 to 5.1 (a 26% reduction). A new foot-worn, home-based, biomechanical intervention for patients with chronic non-specific back pain was found to be clinically effective. Given the lack of non-surgical, non-pharmacological interventions for this populations, this treatment might serve as an adjunct to the current standard of care.

Quality and Reliability Assessment of Electrical Units in Accelerated Life Testing via Bayesian Statistical Approach

ABSTRACTThis study discusses predicting the survival times of some electrical units over future time subjected to an accelerated life test (ALT), namely the step stress ALT. Due to the longevity of the tested units, a censoring scheme is applied, namely the type I censoring scheme, to limit the time of the applied test. The main theme of this paper is to assess the quality of the tested items, based on Bayesian estimation, to guarantee that these units are more reliable and can compete in the world markets.

Deposition of VS2/MoS2 bilayer layers of 2D material on nickel inverse opal structural substrates by SILAR and ECD processes as supercapacitor electrodes

The composition, microstructure, and electrochemical properties of the two kinds of thin film electrode materials, namely VS2/MoS2/Ni-IOS and VS2/MoS2/Ni-foam, were analyzed. The research results indicate that the self-assembled photonic crystal (PhC) templates with adjusted electrophoretic self-assembly processing parameters (100 V cm-1; 7 min) would lead the specimen to a face-centered closely packed structure. Metallic nickel inverse opal structure (IOS) PhCs whose thickness can be freely regulated simply by electrochemical deposition time. VS2and MoS2are 2D materials with excellent electrochemical properties. We employed them as the electroactive material in this study and deposited them onto nickel IOS (Ni-IOS) surfaces to form a composite of The specimens exhibited an excellent specific capacitance (2180 F g-1) at a charge-discharge current density of 5 A g-1. After the 2000 cycles during the life test, the sample can still retain the original specific capacitance value by 72.3%. The IOS PhC substrate produced in this work is designed as VS2/MoS2/Ni-IOS supercapacitor electrode materials, which is proved to offer a significant technical contribution to the application of 2D materials in high-performance supercapacitors currently.

Load Testing Application for Truss Bridge Design Verification: Live Load Testing

This is the second of two companion papers discussing application of load testing techniques for verification of bridge design. The bridge was a six-spans continuous steel truss structure, about 338-m long and 14.45-m wide, in the State of New York. Design of the bridge was completed using an unconventional approach where the top chords of the main trusses, floor beams, and stringers were designed to act composite with the concrete deck. In addition to axial forces, such a design also gives rise to secondary moments in the truss main members under design loads. This aroused interest in verification of the design through an instrumentation, monitoring, and load testing program. Comparing the members’ actual service load axial forces and moments with those used in the design, it was concluded that axial forces were overestimated in the design by about 20 percent for service dead load and by about 25 percent for service live load. Similar comparison for moments, indicated that service dead load moments were within 20 percent of those used in the design and service live load moments were underestimated by about 55 percent. The above differences for service dead load can be attributed to the way the deck pours were accounted for in the design and the possibility of construction loads being on the structure during the deck pour monitoring. For service live load, these differences can be explained by possible discrepancies in estimating service live load from the test results and the fact that the analysis for service live load in the design was performed ignoring the contribution of the composite concrete deck. Adequacy of the structural design under actual axial forces and moments was confirmed by checking the AASHTO interaction equations for steel members under combined axial and bending loading conditions. The major contribution of this and the companion paper is that, they introduced a new approach for estimating total dead load effects by only monitoring strains in a limited number of truss members during staged deck construction and load testing of a very large truss bridge structure, it validated the unconventional design under both dead load and live load as a viable method for design of truss bridge structures, and it supplemented the very limited literature on dead load monitoring of bridges.

Fatigue Life Analysis of Titanium Torsion Spring Based on Continuous Damage Mechanics.

In this study, a titanium alloy torsional spring used in aviation was taken as the research subject. Aiming at the fatigue life prediction problem of this spring, the life analysis of the titanium alloy torsional spring was performed using a customized UMAT subroutine based on the theory of continuous damage mechanics. Several sets of life prediction models and tests were compared. The fatigue lives of the springs at 60, 80, 100, and 120 degrees were 45,070, 65,067, 99,677, and 181,322 cycles, respectively. Compared with other fatigue life prediction methods, the fatigue life calculated by the customized subroutine was the most consistent with the fatigue life of the titanium alloy torsion spring tests. The average relative error between the measured experimental life value and the predicted value was 2.04%, which is less than 5%, meeting engineering measurement requirements. The effectiveness and applicability of the proposed model and method were verified, and the time and economic cost caused by excessively long experimental cycles were reduced. This helps improve the accuracy of fatigue life prediction for this titanium alloy torsional spring and provides analysis support for subsequent structural optimization and improvement.

Optimization of Ti/TiO2 Nanotube/Nano PbO2 Anodes for Enhanced Electrocatalytic Degradation of Methylene Blue: Pulse vs Direct Current Approaches

This study focused on examining how the presence of a TiO2 nanotube (NT) interlayer and decreasing particle size affects the electrochemical performance and service life of PbO2-coatings on a titanium substrate. The Ti/TiO2-NT/β-PbO2 and Ti/PbO2 electrodes were synthesized using direct current with particle size of 3 μm and optimized current density values, while the Ti/TiO2-NT/nanoβ-PbO2 electrodes with β-PbO2 particle size of 35 nm were synthesized using a simple pulse electrodeposition method and optimized duty cycle. The results of cyclic voltammetry demonstrated that the Ti/TiO2-NT/nanoPbO2 electrode exhibited a larger electrochemically active surface area, voltammetry charge values of 3.06 mC cm−2, and a lower charge transfer resistance of 9.47 Ω.cm2 compared to the Ti/TiO2-NT/microPbO2 and Ti/PbO2, which had values of 9.26 and 14.62 mC cm−2 and 61.58 Ω.cm2, and 8900 Ω.cm2, respectively. Accelerated service life tests showed that the Ti/TiO2/nanoPbO2 electrode (55 h) had a better service life than those of Ti/TiO2-NT/microPbO2 and Ti/PbO2 electrodes (50 and 18 h respectively). Moreover, the Ti/TiO2-NT/nanoβ-PbO2 electrode showed the highest performance in degrading methylene blue in simulated wastewater by bulk electrolysis, with a removal efficiency of approximately 100% at optimal current density (60 mAcm−2), surpassing the efficiency of the Ti/TiO2-NT/microPbO2 (76%) and Ti/PbO2 electrodes (53%).

Estimating the shelf life of instant turmeric rice seasonings with various turmeric concentrations through Accelerated Shelf Life Testing (ASLT)

Estimating the shelf life of instant turmeric rice seasonings with various turmeric concentrations through Accelerated Shelf Life Testing (ASLT)

Prediction of gear degradation trend under failure modes based on accelerated life test

Prediction of gear degradation trend under failure modes based on accelerated life test