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Sealing rings are the core components of flange sealing structures and play a crucial role in the storage and operation of gas generators. The aging and deformation of seals affect the safe operation of the device. This paper aims to investigate the effect of rubber aging on the sealing performance of the components, which is realized by nonlinear finite element analysis. Firstly, an accelerated degradation test method was used to obtain the compression permanent deformation and stress–strain curve of rubber during the aging process. A two-dimensional finite element model of the sealing structure was constructed and the Yeoh model was utilized to describe the mechanical response of rubber. During the simulation, the contact area was modified based on the compression permanent deformation, and the Yeoh model was updated based on the stress–strain curve changes obtained by the test. The impact of key parameters such as material property changes, rubber physical section deformation, and fluid pressure on sealing performance during the seal ring aging process was systematically studied. The numerical results indicate that due to the aging deformation of rubber seals, there is a significant decrease in contact stress and contact width, as well as a shift in maximum equivalent stress area. Taking into account these findings, this study proposes a new design concept for sealing structures. This provides a relatively simple research method for studying flange sealing structure performance. [ABSTRACT FROM AUTHOR]

To address the situation that the degraded system cannot be repaired as new and the degradation is accelerated after repair in engineering practice, an imperfect condition-based maintenance model is proposed based on the Gamma process by introducing the maintenance improvement factor and the accelerated degradation factor. The maintenance improvement factor describes the recovery degree of the degradation amount after imperfect maintenance, then gives a quantitative representation method of the system maintenance improvement effect and the determination method of the maximum number of imperfect maintenance. The accelerated degradation factor is combined with the geometric process to describe the accelerated degradation process of the system after imperfect maintenance. The Monte Carlo method is used to determine the optimal number of imperfect preventive maintenance decisions. Through the demonstration of calculation examples, the influence of accelerated degradation factor and maintenance improvement factor on the long-term operation maintenance rate and the optimal number of imperfect maintenance is analyzed. The results show that the model can more comprehensively describe the degradation and maintenance process of degraded systems, and it can effectively reduce maintenance cost ratio under long-term operation. It provides a certain theoretical support for formulating an economical and reasonable maintenance strategy that is more in line with the actual degradation and maintenance process in engineering practice. [ABSTRACT FROM AUTHOR]

The effects on the stability under accelerated degradation of phenolic resin used for the corrosion inhibition of metallic surfaces in aeronautical and nuclear spare parts are evaluated by nonisothermal chemiluminescence (CL) at four different heating rates: 5, 10, 15, and 20 °C min-1. The simulation of the interface interaction between the metallic bodies and protection layers is achieved by the addition of metallic oxides as corrosion promoters: Gd2O3, CeO2, Pr2O3, MgO, MnO2, Cr2O3, and In2O3. These metallic atoms may be the main alloying elements that are present in the compositions of special application products. The presence of a specific peak in the CL spectra between 160 and 177°C proves the oxidation activity of filler in the connection of electronic interference. The differences between the emission intensities of the studied formulations certify the unlike contributions of alloying components. The heating rate plays also the role of oxidation factor that influences the refreshing surrounding atmosphere. The present results define the thermal technological limits of peculiar operation conditions for any metallic item subjected to a high level of warranty. The initiation of degradation in phenolic resin is done by γ-irradiation when free fragments are provided for the interaction with metallic structures. The development of oxidation is analyzed by the modification of CL emission intensities from room temperature to 250°C. The diminution of this process parameter over 200°C is found an essential factor for the preservation of surface integrity. [ABSTRACT FROM AUTHOR]

[Display omitted] Assessment of cold stability is essential for manufacture and commercialization of biotherapeutics. Storage stability is often estimated by measuring accelerated rates at elevated temperature and using mathematical models (as the Arrhenius equation). Although, this strategy often leads to an underestimation of protein aggregation during storage. In this work, we measured the aggregation rates of two antibodies in a broad temperature range (from 60 °C to −25 °C), using an isochoric cooling method to prevent freezing of the formulations below 0 °C. Both antibodies evidenced increasing aggregation rates when approaching extreme temperatures, because of hot and cold denaturation. This behavior was modelled using Arrhenius and Gibbs-Helmholtz equations, which enabled to deconvolute the contribution of unfolding from the protein association kinetics. This approach made possible to model the aggregation rates at refrigeration temperature (5 °C) in a relatively short timeframe (1–2 weeks) and using standard characterization techniques (SEC-HPLC and DLS). [ABSTRACT FROM AUTHOR]

In recent decades, there has been an increasing focus on the alarming decline in global bee populations, given their critical ecological contributions to natural pollination and biodiversity. This decline, marked by a substantial reduction in bee colonies in forested areas, has serious implications for sustainable beekeeping practices and poses a broader risk to ecological well-being. Addressing these pressing issues requires innovative solutions, one of which involves the development and fabrication of beehives crafted from composite materials that are ecologically compatible with bee biology. Importantly, these materials should also exhibit a high resistance to environmental factors, such as ultraviolet (UV) radiation, in order to maintain their mechanical integrity and longevity. To investigate this, we conducted accelerated UV degradation tests on a variety of composite materials to rapidly assess their susceptibility to UV-induced changes. High-density polyethylene (HDPE) served as the matrix material and was reinforced with natural fibers, specifically fique fibers (Furcraea bedinghausii), banana fibers, and goose feathers. Our findings indicate that UV radiation exposure results in a noticeable reduction in the tensile strength of these materials. For example, wood composites experienced a 48% decline in tensile strength over a 60-day period, a rate of deterioration notably higher than that of other tested composite materials. Conversely, HDPE composites fortified with banana fibers initially demonstrated tensile strengths exceeding 9 MPa and 10 MPa. Although these values gradually decreased over the observation period, the composites still displayed favorable stress–strain characteristics. This research underscores the substantial influence of UV radiation on the longevity and efficacy of beehive materials, which in turn affects the durability of natural wood hives exposed to these environmental factors. The resultant increased maintenance and replacement costs for beekeepers further emphasize the need for judicious material selection in beehive construction and point to the viability of the composite materials examined in this study. [ABSTRACT FROM AUTHOR]

Copyright of Electric Machines & Control / Dianji Yu Kongzhi Xuebao is the property of Electric Machines & Control and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

To cope with the severe plastic waste crisis, massive efforts are made to develop sustainable polymer materials whose degradation involves a disposing and decomposing to small molecule (DDM) and/or a chemical recycling to monomer (CRM) process. Polyacetals, a type of pH‐responsive polymers, are degradable under acidic conditions, while highly stable under neutral and basic circumstances. As for their synthesis, the cationic ring‐opening polymerization (CROP) of cyclic acetals is an elegant and promising approach, though suffering from fatal side reactions and polymerization‐depolymerization equilibrium. Recent development in CRM restimulates the interest in the long‐forgotten CROP method due to its inherent depolymerization characteristics. In terms of the end‐of‐life options, polyacetals are recyclable materials with both DDM and CRM potentials. They not only expand the scope of materials for closed‐loop recycling but also help to tune the degradation properties of traditional polyesters and polyolefins. This review aims to discuss the synthesis of various polyacetals by CROP and their degradation properties from the perspectives of 1) polymerization of cyclic acetals, dioxepins, and hemiacetal esters, 2) copolymerization of cyclic acetals with heterocyclic or vinyl monomers, and 3) degradation and recycling properties of the related polymers. [ABSTRACT FROM AUTHOR]

Fe-based biodegradable materials as next-generation bone implants attract considerable attentions due to outstanding mechanical properties and favorable biocompatibility. However, their too slow degradation to match bone growth is a dilemma which urgently needs to be solved and thus is given special attentions in this review. Analyses and countermeasures to increase degradation rates of Fe-based materials are summarized. Meanwhile, detailed effects of accelerating degradation on biocompatibility and mechanical properties are also discussed. Subsequently, efforts about manufacturing mechanisms and methods of Fe-based biodegradable materials are consolidated and presented. Moreover, future outlook for Fe-based biodegradable materials is proposed. This review provides critical and valid information for development and breakthrough of Fe-based biodegradable materials toward orthopaedic applications.

The dimensionless total turnover number TTN, the average number of turnovers per active site of a catalyst over the catalyst's lifetime, is a universal criterion for the operational stability of a catalyst. If the cost of the catalyst is known, the cost contribution per catalytic cycle can be determined. The present work honors the contributions by Prof. Christian Wandrey and his group on the topic of TTN and describes some recent developments on the subject. [ABSTRACT FROM AUTHOR]

Copyright of Lubrication Engineering (0254-0150) is the property of Editorial Office of LUBRICATION ENGINEERING and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In a system, prediction of remaining useful lifetime (RUL) of servicing before reaching to a specified breakdown threshold is a very important practical issue, and research in this field is still regarded as an appreciated research gap. Operational environment of an equipment is not constant and changes regarding to stresses and shocks. These random environmental factors accelerate system deterioration by affecting on the level or rate of degradation path. The present study focuses on providing a practical operational guideline to estimate the RUL of a system with general degradation path after receiving a shock which only affects on the degradation level. Due to exact estimation of the shock arrival times and measuring the magnitudes of future shocks to investigate shock effects on RUL is almost impossible in the real world and laborious in practice, in this research a new procedure based on total defect size monitored in the constant inspection periods and Accelerated Factor (AF) is proposed to analyze RUL of the system. A Micro-Electro-Mechanical system (MEMS) is used as an example and the results show the applicability of the proposed approach.

Hydrochlorothiazide (HCT) is a pharmaceutical micropollutant highly toxic to the environment, being absolutely necessary to oxidize it completely to CO2. Here, the variables stoichiometric H2O2 excess for (a) degradation and (b) mineralization are defined and used as metric to quantify the dosimetry of the H2O2. So that, dose of H2O2 qualifies being under- and over-dose respectively for values below and above such standards. In this work, these concepts have been elucidated across AOPs regarding the H2O2 degradation excess, whereas only UVC-Fenton was used regarding the H2O2 mineralization excess. At a H2O2 mineralization excess of 0.68 (equivalent to degradation excess of 36.74), oxidation via UVC-H2O2 enables absolute (100%) HCT degradation within 60 min; however, the mineralization of HCT demonstrated limited optimization for all AOPs employed in the beaker-like reactor of this work, being the underlying reasons investigated hereby. At best, 26.70% HCT mineralization was observed within 60 min of UVC photo-Fenton using an initial 2.00 H2O2 mineralization excess. Such mineralization of 26.7% is unexpectedly low considering that, in addition, the residual H2O2 concentration almost fully depletes within 30 min of UVC-Fenton oxidation. Taken all that together, the loss of H2O2 due its decomposition induced by the risen temperature from 28 to 70ºC very likely were the underlying reason preventing better mineralization performance. We successfully demonstrated 18% of mean efficiency of radical •OH consumption signals that the overheating is indeed a designer problem with the photo-reactor since a well-refrigerated photo-reactor shows a mean efficiency of 38% for the same H2O2 excess. [ABSTRACT FROM AUTHOR]

Poly (L‐lactic acid) (PLLA) vascular stents are promising to be used to treat vascular stenosis. However, the degradation of these implanted stents has a great influence on the mechanical properties. In this work, we studied the factors that can influence the mechanical properties by accelerating the degradation of PLLA stents with crimping and expansion in phosphate buffer solution (PBS) at 70°C. The typical influence factors such as the real‐time weight‐average molecular weight (Mw), crystallinity, surface morphologies, and mass loss of these samples were analyzed in detail. Results showed that radial strength of the stents increased from 877 to 1204 mmHg after accelerated degradation for 2 days and then decreased to almost 0 mmHg after 10 days. Meanwhile, radial stiffness showed an upward trend which is caused by the decrease in Mw, increase in crystallinity and local damage during the crimping and expansion process. Moreover, negligible mass loss of stents was observed in this period and the bulk degradation behavior predominated in the whole process. [ABSTRACT FROM AUTHOR]

In recent decades, there has been an increasing focus on the alarming decline in global bee populations, given their critical ecological contributions to natural pollination and biodiversity. This decline, marked by a substantial reduction in bee colonies in forested areas, has serious implications for sustainable beekeeping practices and poses a broader risk to ecological well-being. Addressing these pressing issues requires innovative solutions, one of which involves the development and fabrication of beehives crafted from composite materials that are ecologically compatible with bee biology. Importantly, these materials should also exhibit a high resistance to environmental factors, such as ultraviolet (UV) radiation, in order to maintain their mechanical integrity and longevity. To investigate this, we conducted accelerated UV degradation tests on a variety of composite materials to rapidly assess their susceptibility to UV-induced changes. High-density polyethylene (HDPE) served as the matrix material and was reinforced with natural fibers, specifically fique fibers (Furcraea bedinghausii), banana fibers, and goose feathers. Our findings indicate that UV radiation exposure results in a noticeable reduction in the tensile strength of these materials. For example, wood composites experienced a 48% decline in tensile strength over a 60-day period, a rate of deterioration notably higher than that of other tested composite materials. Conversely, HDPE composites fortified with banana fibers initially demonstrated tensile strengths exceeding 9 MPa and 10 MPa. Although these values gradually decreased over the observation period, the composites still displayed favorable stress–strain characteristics. This research underscores the substantial influence of UV radiation on the longevity and efficacy of beehive materials, which in turn affects the durability of natural wood hives exposed to these environmental factors. The resultant increased maintenance and replacement costs for beekeepers further emphasize the need for judicious material selection in beehive construction and point to the viability of the composite materials examined in this study.

Fluoroelastomers are suitable materials for several applications at high temperature. The present paper presents the modifications of material stability of fluoroelastomer Tecnoflon FOR 80 HS under hard operation conditions: thermal and radiation degradation. The sequence of aging stages influences the oxidation state of polymer, which loses its thermal characteristics in the close relation with scission degrees. The chemiluminescence investigation and mechanical testing are the selected procedures for the evaluation of sustained degradation asked for the qualification of O-rings, buffers and gaskets destined to nuclear power plants. The contributions of the two kinds of degrading energies: heat and ionizing radiation are discussed by means of the values of activation energies, which may describe the modification in the oxidation strength. The high temperatures applied in the assessment of material stability (170, 195 and 220 °C) as well as the descendant shape dependencies of the CL intensity vs time indicate the damage tendency with respect to the progress of oxidation in polymer matrix. The large differences between the evolutions of oxidation in the nonisothermal CL spectra of Tecnoflon material depict the existence of different local concentrations of radicals. Their decay takes place over about 100 °C, after which various routes of degradation are followed. [ABSTRACT FROM AUTHOR]

This study provides insight into the accelerated hydrolysis of polyester PLA through the addition of phosphites based on pentaerythritol. To control hydrolysis and ensure processing stability, different types of phosphites and combinations of phosphites with acid scavengers were studied. Therefore, commercially available PLA was compounded with selected additives on a twin-screw extruder, and hydrolysis experiments were performed at 23 °C, 35 °C and 58 °C in deionized water. Hydrolysis of PLA was evaluated by the melt volume rate (MVR) and size-exclusion chromatography (SEC). For example, after 4 days of water storage at 58 °C, the number average molecular weight of the PLA comparison sample was reduced by 31.3%, whereas PLA compounded with 0.8% phosphite P1 had a 57.7% lower molecular weight. The results are in good agreement with the expected and tested stability against hydrolysis of the investigated phosphite structures. 31P-NMR spectroscopy was utilized to elucidate the hydrolysis of phosphites in the presence of lactic acid. With the addition of phosphites based on pentaerythritol, the hydrolysis rate can be enhanced, and faster biodegradation behavior of biodegradable polyesters is expected. Accelerated biodegradation is beneficial for reducing the residence time of polymers in composting facilities or during home composting and as litter or microplastic residues. [ABSTRACT FROM AUTHOR]

The biodiesel susceptibility to oxidation causes its qualitative deterioration and affects both its handling and long-term storage. This study aims to evaluate biodiesel (commercial-grade and fresh samples) oxidative degradation via combined extended storage studies and under dynamic laboratory-scale accelerated conditions. Biodiesel samples from various feedstocks (waste cooking oils, tallow oil, vegetable oils) with and without addition of a synthetic commercial antioxidant (Chimec HR 876 HFP, 500 mg/kg) were stored at ambient conditions for long-time periods (6 and 14 months), and/or submitted to accelerated aging. During the accelerated oxidation tests, the samples were exposed to an air flow rate of 100, 200 and 300 mL/min for 2, 4 and 6 h at 120 °C. The storage stability of biodiesels depended on the utilized feedstock, while the antioxidant addition rendered the storage of the samples from waste cooking oil and tallow oil for ~ 12 months. The biodiesels were intensively deteriorated when submitted to dynamic oxidation (at 120 °C with air flow rate of 300 mL/min for 6 h), as confirmed by the acidity and induction period. After 2 h of intense oxidation, the IP of the biodiesels decreased below EN 14214 limit, while after ~ 2–4 h, the TAN values exceeded the respective limit (with the exception of PME samples). These conditions could correspond to the biodiesel's quality deterioration after ~ 1–3 months of storage under the examined conditions, accounting the biodiesel type. Based on these results, the stability of biodiesel is associated with the aging conditions, its type and the antioxidant, as well. [ABSTRACT FROM AUTHOR]

Microplastics (MPs) are one of the emerging contaminants in environmental media, and they have raised great concern because they are resistant to degradation and persist in ecosystems. Although numerous advanced technologies have been developed, suitable technologies are still lacking for degradation of widespread MPs in the natural environment. We have discovered that MPs can be degraded exceptionally rapidly in frozen environments. Taking polystyrene (PS) as an example, its degradation rate in ice (−20 °C) is surprisingly competitive to most artificial technologies. PS particles are trapped and squeezed to achieve excited state (3PS*) in the narrow space of the liquid layer between ice crystals, which further react with the highly concentrated dioxygen to selectively produce singlet oxygen (1O2). The 1O2 boosts PS oxidation in the liquid layer thus further causing accelerated degradation at freezing temperature. This finding offers a highly efficient pathway for degradation of MPs and it sheds light on an unusual MPs disposal mechanisms in nature. [ABSTRACT FROM AUTHOR]

Poly(lactic acid) (PLA) has been found to be important in various applications, such as in the medical, pharmaceutical, and packaging industries. However, the long-term associated degradation process of PLA is a limiting factor for some applications. Therefore, in this research, the influence of corona and radio-frequency (RF) surface plasma treatment on the degradation of PLA in accelerated weathering tests was studied. The accelerated weathering test was applied using standard UV irradiation for up to 2000 h. The morphological/topographical, chemical, crystallization, mechanical, and thermal changes were analyzed after 500, 1000, and 2000 h of accelerated weathering time. The introduction of the polar functional groups caused by plasma treatment on the PLA surface improved its wettability, and therefore, hydrolytic degradation was promoted over the accelerated weathering time. It was revealed that the plasma treatment enhanced the hydrolytic and UV degradation of the PLA, as was confirmed by investigation of the physical, chemical, mechanical, and thermal properties. Moreover, the RF plasma was more pronounced than the corona plasma in the degradation of the PLA. Such an approach represents a pathway to promote and tailor PLA degradation.

The primary mode of failure in electric connectors is contact failure, one of the reasons is which occurs as a result of external vibrations in the environment. This failure arises due to the reduction in positive pressure on the electric connector terminal caused by the vibration, leading to fluctuations in the electrical contact resistance (ECR). When both vibrational stress and plug/pull stress is simultaneously present, the contact area of electric connectors experiences fretting wear and shear stress, resulting in a more intricate failure mechanism for the electrical connector. Thus, this study presents an accelerated degradation testing method designed to investigate the reliability of the junior power timer (JPT) electric connector employed in automobiles. A temperature resistance test, plug/pull test (sliding wear) and vibration test (fretting wear) were conducted for the JPT electric connector. The electrical contact failure mechanism of the JPT electrical connector was analyzed, with specific focus on its correlation with the concentration of oxides in the contact area. [Display omitted] • Consider the multiple effects of elevated temperature, vibration and plug/pulling. • Analyzed electrical contact properties for connector with different coating. • Explain the electrical contact property degradation under multiple stress coupling. • The failure mechanism of different coatings under multiple stresses is clarified. [ABSTRACT FROM AUTHOR]

Within this study, we investigate the intrinsic photostability of thin‐film solar cells, here organic photovoltaic cells. Since degradation under natural sun light proceeds within the timeframe of months and years, the process needs to be speeded up for fast material analysis and screening, using high‐concentration accelerated lifetime testing (high‐C ALT). For this purpose, we established setups allowing irradiances of up to 730 sun equivalents (SE). One key finding of our study is that accelerating the testing procedure by such large intensities is possible but a precise measurement and control of the solar cell temperature is absolutely essential. Accordingly, we developed an innovative method of determining the temperature of the active layer which offers significant advantages over commonly used measurement methods. Furthermore, it was found that the degradation process under high illumination densities can be well described by a stretched exponential law. We demonstrate that the temperature kinetics of P3HT:PCBM was found to be Arrhenius governed with an activation energy of 27.2 kJ/mol under continuous illumination of 300 SE. Finally, it was shown that the velocity of light‐induced degradation of short‐circuit current depends linearly on the used irradiance dose at a given temperature starting from normal illumination conditions up to at least 300 SE. This makes high‐C ALT a very valuable tool for swift screening of the lifetime of novel thin‐film solar cells and materials. [ABSTRACT FROM AUTHOR]

Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) is a polyester, produced naturally by microorganisms, with excellent biocompatibility. Corona and radio-frequency (RF) plasma treatment were applied in order to improve the degradation process of PHBV. Samples were subjected to an accelerated weathering test for 500, 1000, and 2000 h of weathering exposure and to natural weathering for one year. Various analytical, spectroscopic, and microscopic techniques have been used to analyze the degradation process. This study revealed that corona and RF plasma treatment acted as a hydrolytic and ultraviolet light (UV) degradation promoter for PHBV. Both plasma treatments chemically modify the PHBV surface resulting in better wettability contributing to the hydrolytic degradation. Microscopic analysis revealed a rougher defects-containing surface of plasma-treated PHBV in comparison with untreated PHBV after the degradation process, promoting deeper water diffusion and UV penetration. The photo- and hydrolytic degradation caused significant surface changes of plasma-treated PHBV after 2000 h of accelerated weathering and one year of natural weathering. Moreover, deterioration in mechanical properties has been more pronounced in the RF plasma-treated samples. These results demonstrate the potential use of plasma treatment on improving the degradability of PHBV. [ABSTRACT FROM AUTHOR]

Museums and galleries house increasingly large collections of objects and contemporary art made of plastic materials, many of which undergo rapid material change. The main degradation processes of poly(vinyl chloride) (PVC) are elimination of HCl and plasticizer migration or leaching. This results in visible discolouration, stickiness and cracking. Degradation is known to be a multi-stage process that includes HCl elimination, formation of conjugated polyenes and cross-linking. Elimination of HCl begins due to structural irregularities (allylic and tertiary chlorides) and results in the formation of polyenes. When at least 7 conjugated double bonds are present, discolouration of PVC becomes visible. Non-invasive techniques, such as IR and Raman spectroscopy are used for polymer identification and plasticizer quantification. Plasticizer degradation and particularly the late stages of PVC degradation can be investigated using SEC, GC-MS, TGA and DSC. Studies in heritage collections have revealed that, apart from HCl, PVC objects emit 2-ethylhexanol and other volatile degradation products, however, there is currently no indication that HCl is emitted at usual indoor conditions. There seems to be a general lack of systematic research into PVC degradation at the conditions of storage and display, which could result in the development of dose-response functions and in the development of preventive conservation guidelines for the management of PVC collections.

Designing laboratory-scale degradation experiments for polymer-based biomaterials is crucial for the development of safe and functional implants, in particular regarding high molecular weight polyesters. Within this work, we compared accelerated degradation of solvent cast HMW-PLLA and HMW-P3HB films at 55 °C (16 weeks) with enzyme-associated (proteinase K and lipases) real-time degradation at 37 °C (108 weeks). During real-time degradation, PLLA showed mass loss up to 83%, in contrast to accelerated conditions, where no changes occurred. Moreover, we observed wave-shape development of crystallinity for PLLA and PHB for both degradation conditions applied, whereby PLLA χ value nearly doubled to up to 75%. These results were used to develop a correlation model based on molecular weight decrease and were furthermore discussed in light of a detailed literature review. In summary, real-time in vitro studies could be adapted to accelerated protocols providing the same limiting conditions such as molecular weight and initial crystallinity are given.

The optocoupler is a weak link in the inertial navigation platform of a kind of guided munitions. It is necessary to use accelerated storage test to verify the storage life of long storage products. Especially for small sample products, it is very important to obtain prior information for the design and implementation of accelerated degradation test. In this paper, the optocoupler failure mechanism verification test is designed and the experimental results are analyzed and the prior information is obtained. The results show that optocouplers have two failure modes, one is sudden failure and the other is degradation failure; the maximum temperature stress of optocoupler can't exceed 140 °C; the increase of leakage current of optocoupler is caused by movable ions contaminating the LED chip. The surface leakage current is proportional to the adsorption amount. The increase of leakage current makes p-n junction tunneling effect occur which LEDs the failure of the optocoupler. The lifetime distribution model of the optocoupler is determined by the failure physics. The lifetime of the optocoupler is subject to the lognormal distribution. The degeneracy orbit of the optocoupler leakage current is described by a power law model. The estimated values of the orbital parameters are initially calculated and the parameters of its life distribution function are deduced. The above information lays a good foundation for the optimization design and data processing of the accelerated degradation experiment.

This study provides insight into the accelerated hydrolysis of polyester PLA through the addition of phosphites based on pentaerythritol. To control hydrolysis and ensure processing stability, different types of phosphites and combinations of phosphites with acid scavengers were studied. Therefore, commercially available PLA was compounded with selected additives on a twin-screw extruder, and hydrolysis experiments were performed at 23 °C, 35 °C and 58 °C in deionized water. Hydrolysis of PLA was evaluated by the melt volume rate (MVR) and size-exclusion chromatography (SEC). For example, after 4 days of water storage at 58 °C, the number average molecular weight of the PLA comparison sample was reduced by 31.3%, whereas PLA compounded with 0.8% phosphite P1 had a 57.7% lower molecular weight. The results are in good agreement with the expected and tested stability against hydrolysis of the investigated phosphite structures. 31P-NMR spectroscopy was utilized to elucidate the hydrolysis of phosphites in the presence of lactic acid. With the addition of phosphites based on pentaerythritol, the hydrolysis rate can be enhanced, and faster biodegradation behavior of biodegradable polyesters is expected. Accelerated biodegradation is beneficial for reducing the residence time of polymers in composting facilities or during home composting and as litter or microplastic residues.

Poly(lactic acid) (PLA) has been found to be important in various applications, such as in the medical, pharmaceutical, and packaging industries. However, the long-term associated degradation process of PLA is a limiting factor for some applications. Therefore, in this research, the influence of corona and radio-frequency (RF) surface plasma treatment on the degradation of PLA in accelerated weathering tests was studied. The accelerated weathering test was applied using standard UV irradiation for up to 2000 h. The morphological/topographical, chemical, crystallization, mechanical, and thermal changes were analyzed after 500, 1000, and 2000 h of accelerated weathering time. The introduction of the polar functional groups caused by plasma treatment on the PLA surface improved its wettability, and therefore, hydrolytic degradation was promoted over the accelerated weathering time. It was revealed that the plasma treatment enhanced the hydrolytic and UV degradation of the PLA, as was confirmed by investigation of the physical, chemical, mechanical, and thermal properties. Moreover, the RF plasma was more pronounced than the corona plasma in the degradation of the PLA. Such an approach represents a pathway to promote and tailor PLA degradation. [ABSTRACT FROM AUTHOR]

The degradable polymer Polydioxanone (PDO) is used for medical implants since 1981. Manufacturers state a degradation timeframe of

To more accurately predict the permanence of paper during natural aging, we studied cellulose aging according to closed vial setup, which compared to alternative paper aging methods is closer to natural aging with regard to predictions of paper life expectancy. To improve kinetic evaluation, not only cellulose degradation by hydrolysis and oxidation, but also the moisture content in the closed vial were measured during the aging process. This allowed to eliminate the long-known errors of the method caused by vial leakage which falsely produce different aging rates for different aging periods. With the aim of predicting paper permanence more accurately, several ways of considering the moisture changes and the influences of paper moisture and vial leakage were considered and an improved protocol was elaborated that corrects the rate of cellulose chain scission based on the average moisture content in the paper. Based on this hydrolysis rate, the expected half-life DP becomes independent of the aging period and thus less error-prone and more reliable. We hope that this improvement of the very common closed-vial aging method will quickly be accepted and welcomed by the paper conservation community. [ABSTRACT FROM AUTHOR]

Freshly assembled proton exchange fuel cells (PEMFC) require conditioning to reach maximum power density. This process may last up to tens of hours and adds to the cost of commercial fuel cell technology. We present an accelerated conditioning procedure involving starving the cathode of oxidant. In single cells, this procedure conditions a membrane electrode assembly (MEA) within 40 min, without compromising durability. The performance and durability of MEAs conditioned using this technique are compared with US Department of Energy (DOE) and European Union (EU) harmonized protocols, and to an amperometric conditioning protocol. The time to reach peak power density using cathode starvation conditioning is

The EPDM (ethylene-propylene-diene monomer) hybrids with improved thermal and radiation strengths containing 1 and 5 phr of polyhedral oligomeric silsesquioxane (vinyl-POSS, Ov-POSS) and/or 2 phr of microalgae (Chlorella vulgaris (CV) and Spirulinaplatensis (SP)) powders were investigated in respect to their thermal stability after γ-irradiation. The material durability under accelerated degradation was qualified by chemiluminescence and gelation, which prove the contribution of inorganic filler and microalgae extracts on the increase of hybrid thermal stability, as well as the interaction between added components (POSS and CV or SP). The activation energies and the durabilities under accelerated degradation were calculated, indicating their suitable usage as appropriate materials in various applications. The reported results indicate the improvement effect of both microalgal powders on the oxidation strength, but the contribution of Spirulinaplatensis grabs attention on its efficient effects upon the prevention of degradation under accelerated aging conditions. The thermal performances of the tested EPDM based hybrids are remarkably ameliorated, if the certain formulation includes Ov-POSS (5 phr) and Spirulinaplatensis (2 phr), certifying its suitability for the pertinent applications.

Scientists use biological procedures as ecofriendly and cost‐effective routes to synthesis nanoparticles and nanomaterials. In this work, the biological attitude was aimed at the production of nanoparticles by Haplophyllum obtusifolium watery extract. Several procedures used to describe fabricated nanoparticles are transmission electron microscopy, ultraviolet–visible (UV–vis) spectrometry, Fourier transform infrared spectroscopy, and X‐ray diffraction. UV–vis technique indicated a sharp peak in area 416 nm and transmission electron microscopy pictures show that the shape of the nanoparticles is spherical and the mean diameter of the synthesised nanoparticle is 13 nm. The silver and silver oxide‐nanoparticles (Ag/Ag2O‐NPs) exhibited antimicrobial properties against positive/negative infective bacteria for instance Staphylococcus aureus/Pseudomonas aeruginosa, Escherichia coli. The biosynthesised nanoparticles show anticancer activity against liver cancer cell (HepG2) which depend on time and concentrations. Also, the synthesised Ag/Ag2O‐NPs act as a green catalyst because of accelerated degradation of stable and organic dye. Consequences established this protocol as easy, fast, nontoxic and alternative conventional physico‐chemical approache. [ABSTRACT FROM AUTHOR]

Museums and galleries house increasingly large collections of objects and contemporary art made of plastic materials, many of which undergo rapid material change. The main degradation processes of poly(vinyl chloride) (PVC) are elimination of HCl and plasticizer migration or leaching. This results in visible discolouration, stickiness and cracking. Degradation is known to be a multi-stage process that includes HCl elimination, formation of conjugated polyenes and cross-linking. Elimination of HCl begins due to structural irregularities (allylic and tertiary chlorides) and results in the formation of polyenes. When at least 7 conjugated double bonds are present, discolouration of PVC becomes visible. Non-invasive techniques, such as IR and Raman spectroscopy are used for polymer identification and plasticizer quantification. Plasticizer degradation and particularly the late stages of PVC degradation can be investigated using SEC, GC-MS, TGA and DSC. Studies in heritage collections have revealed that, apart from HCl, PVC objects emit 2-ethylhexanol and other volatile degradation products, however, there is currently no indication that HCl is emitted at usual indoor conditions. There seems to be a general lack of systematic research into PVC degradation at the conditions of storage and display, which could result in the development of dose-response functions and in the development of preventive conservation guidelines for the management of PVC collections. [ABSTRACT FROM AUTHOR]

The nonlinear accelerated degradation severely limits the lifetime of fuel cells. This paper presents a comprehensive analysis of polarization processes during accelerated performance degradation. The double trap model is applied to reveal kinetic degradation, and an equivalent circuit model based on the distribution of relaxation times is proposed to identify and quantify the polarization loss and low-frequency inductive loop. Combined with monitoring dynamic voltage, the results show that the accelerated performance decline is dominated by the growth of platinum oxides rather than kinetic degradation and structural damage. The platinum oxides reduce the cathode mixed potential gradually, leading to the accelerated decay occurring earlier at low current density. Meanwhile, the high oxide coverage hinders oxygen diffusion and water removal, resulting in sudden and drastic concentration polarization in the high current density region. Furthermore, the formation and reduction of platinum oxide affect voltage stability and steady performance of loading and unloading processes due to their potential dependency. The present study helps in modeling and predicting the nonlinear accelerated ageing to improve the lifetime of fuel cells. • Double trap mechanism reveals the kinetics degradation in different currents. • Each polarization is identified by equivalent circuit considering inductive loop. • Mass transfer resistance dominates the accelerated performance decline. • The growth of platinum oxides induces the change in kinetic and mass transfer. [ABSTRACT FROM AUTHOR]

Reliability demonstration testing is widely applied to the industry for the verification of products' certain reliability requirement. However, for long-life and high-reliability products, the sample size and testing time are both unacceptable. To shorten the testing time, the performance degradation data are used to predict whether one sample will fail by the end of the testing. To decrease the sample size or further shorten the testing time, the hardened testing method is considered. Thus, this paper proposes a hardened reliability demonstration testing method with the accelerated degradation model to demonstrate the structural reliability at a high confidence level. First, an accelerated gamma degradation model for the considered problem is formulated. Then, the transformation method of the reliability indexes under different stress levels is proposed. Finally, we develop the optimal testing plan to obtain the stress level, sample size, and average testing time by minimizing the total testing cost, and give the testing termination rules for one sample. A numerical example is given to demonstrate the availability of the proposed method on shortening the testing time and reducing the sample size.

The autocorrelation among measurement errors has been usually ignored in the traditional accelerated degradation modeling procedure. For this problem, a step-stress accelerated degradation model is proposed by simultaneously considering a first-order autoregressive (AR(1)) measurement error series for reliability analysis. The Wiener process is utilized to describe the performance degradation procedure, and an AR(1) model is adopted for modeling the measurement error term. In addition, the relation function between the drift parameter and the accelerated stress is also constructed. Meanwhile, a parameter in the accelerated relation function is randomized to characteristic the individual variation. Then, under the concept of the first hitting time, closed-forms of the probability density function and the distribution function are derived. Moreover, the maximum likelihood estimation method is used for estimating unknown parameters in the proposed model. Finally, a real application involving the GaAs laser is conducted to illustrate the validity and efficiency of the proposed model. Results show that compared with the reference methods, the proposed model shows a better fitting goodness and an enhanced accuracy, and so that it can provide a strong support for further maintenance decision making. [ABSTRACT FROM AUTHOR]

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Highlights • A Gamma accelerated degradation model based on the principle of degradation mechanism invariance is proposed. • The existence of the maximum likelihood estimate of the parameters of the proposed model is proved. • The approximate confidence interval for the shape parameter based on Cornish–Fisher expansion is derived. • The generalized confidence intervals for other model parameters and some important quantities are developed. Abstract This paper proposes a Gamma constant-stress accelerated degradation model based on the principle of the degradation mechanism invariance. The maximum likelihood estimators of the parameters of the proposed model are derived. Based on Cornish–Fisher expansion, the approximate confidence interval for the shape parameter of the Gamma degradation process is developed. Since it is difficult to obtain the exact confidence intervals for other model parameters and some quantities such as the mean degradation in unit time, the quantile and the reliability function of the lifetime at the normal stress level, the generalized confidence intervals for these quantities are proposed. The percentiles of the proposed generalized pivotal quantities can be obtained by the simulation. The performances of the proposed confidence intervals are evaluated by the Monte Carlo simulation method. In the simulation study, the proposed confidence intervals are compared with the Wald and the bootstrap- p confidence intervals. The simulation results show that the proposed confidence intervals outperform the Wald and the bootstrap- p confidence intervals in terms of the coverage percentage. Finally, a real example is used to illustrate the proposed procedures. [ABSTRACT FROM AUTHOR]

• Is it worth degrading BESS for ensuring more reliability benefits? • Annualised indices are required to compare BESS degradation risks against reliability benefits. • It is vital to include asset degradation in asst management platforms for utilities. To ensure the future networks' secure and flexible operation, NOs will increasingly rely upon grid-scale storage services as a secondary (ancillary) service. During critical contingencies, NOs may drive some battery energy storage systems (BESS) that operate at higher depth-of-discharge cycles for increasing reliability benefits. This eventually could lead to accelerated degradation of BESS. The reliability benefits versus the accelerated BESS degradation risks over the BESS lifetime are not deeply investigated in the up-to-date literature. This paper develops a reliability evaluation framework integrating a Bi-Level Sequential Monte Carlo loops with a detailed BESS degradation model. The integration captures the BESS normal and accelerated cycle and capacity degradation across a multi-year network analysis. Annualized indices are defined for assessing the risks of BESS accelerated degradation named as expected equivalent life cycle accelerated degradation (EELCAD), expected equivalent capacity degradation (EECD) and expected battery accelerated degradation costs (EBADC). In addition, it provides a techno-economic assessment of reliability benefits versus the degradation risks over the battery's lifetime. Therefore, the paper presents an in-depth analysis of the benefits and risks associated with battery degradation and the potential implications in long-term planning studies. [ABSTRACT FROM AUTHOR]

Accelerated microbial degradation following previous repeated applications of the same pesticide, or another pesticide of a similar chemical structure, is a known phenomenon. Currently there is limited information regarding accelerated degradation of sulfonylurea (SU) herbicides. This study is aimed to evaluate the effect of repeated SU applications on the degradation rate of the SU herbicide sulfosulfuron in soil. The effect of repeated applications of sulfosulfuron on its degradation was assessed in two soils, using a sorghum root elongation bioassay. The effect of consecutive applications of sulfonylurea herbicides over the course of three to four seasons was further examined in controlled environment and a field study. Degradation of sulfosulfuron was determined following its application to soil samples from the field or a controlled environment, by measuring sulfosulfuron residues using liquid chromatography-tandem mass spectrometry. Following the repeated application of sulfosulfuron in the bioassay, the time to reduce sorghum root growth by 50% was shortened by up to 31.6%. However, consecutive application of SUs in the controlled environment had no effect on sulfosulfuron degradation rate constant. Yet, sulfosulfuron degradation rate was enhanced by a factor of 1.35 following consecutive application of SUs in the field, compared to untreated control soil. The data confirm that sulfosulfuron degradation could be enhanced due to repeated sulfosulfuron applications, thus potentially reducing its herbicidal efficacy.

This study evaluated the insulation resistance characteristics of TFR-8 (Tray Frame Retardant power cable for fire service) and VCTF (Light PVC Sheathed Circular Cord) cables under external flame, over-current, and accelerated degradation tests. In the accelerated degradation test of the cable, aging times of 10, 20, 30, and 40 years were tested according to a temperature derived using the Arrhenius equation. The insulation resistance of the TFR-8 cables was reduced from a maximum of 7.5 T ohm to 0.008 T ohm during the flame contact and recovered to its original state after cooling. However, dielectric breakdown occurred in the VCTF cable during flame contact and the cable did not return to its original state, even after cooling. In the forced convection oven test, the insulation resistance of the cable was reduced at 160 °C, whereas the insulation resistance of the cable was reduced at 125 °C in the over-current test. This result implied that the over-current had a greater impact than did heat applied externally on the degradation of the cable insulator. In the accelerated degradation tests from 10–30 years, the TFR-8 cable did not show any reduction in insulation resistance at room temperature. However, after an induced aging time of 40 years, the cable showed a rapid reduction in insulation resistance at room temperature.