Cyclic Degradation Research Articles

Experimental investigation of mechanical behavior of lightweight RC elements under repeated loadings

Today, the use of lightweight structural concrete in earthquake-prone countries of the world has grown more and more. Therefore, it is important to study the behavior of this type of concrete against seismic loads. So far, many studies have been conducted on the behavior of reinforced concrete (RC) elements against cyclic loads caused by earthquakes, but recent observations show that many earthquakes occur consecutively. That is, structural elements and systems may experience several weak earthquakes or aftershocks during their lifetime. It is obvious that a structure that experiences several cyclic vibrations will suffer a degradation of strength and stiffness, and its behavior will change against subsequent earthquakes. The existing structural models consider the cyclic degradation resulting from the cyclic movement during an earthquake, but many of these models do not consider the effects of degradation caused by previous earthquakes; While this degradation can have significant effects on the behavior of structural elements. In this research, the degradation caused by cyclic loading in lightweight concrete structural elements was investigated first, and then their post-degradation behavior under different levels of degradation was studied; For this purpose, 12 specimens of lightweight RC beams and 4 specimens of lightweight RC columns were made with a scale of 50% and subjected to different uniform and cyclic loadings, and three levels of slight, moderate and extensive degradation were defined based on a number of constant fatigue cycles. Then, in the next step, the cyclic behavior of the specimens after degradation was tested in three levels of slight, moderate and extensive degradation. The results of the tests showed that with the increase in the degradation level, the amount of energy absorption of RC beams decreases; Especially in beams with extensive degradation level, the amount of beam energy absorption decreases by more than 40%. Comparing the cyclic behavior after the degradation of the damaged columns with the behavior of the intact specimen shows that the increase in the level of degradation reduces the ductility of the columns.

Unravelling the effects of ratcheting and constraint on the cyclic behaviour of a martensitic steel under elevated temperature

This work examines important aspects of the high-temperature cyclic visco-plasticity behaviour, namely the ratcheting (cyclic creep) and constraint effects, under low-cycle fatigue (LCF) via experimental characterisation and physically based damage modelling. For this purpose, fully-reversed, load-controlled uniaxial and multi-axial saw-tooth (SWT) low cycle fatigue tests were carried out on a martensitic steel (FV566) at 600oC. Further, an improved physically-based viscoplasticity modelling framework is introduced, which links the material microstructural properties to the constitutive mechanical behaviour, thereby allowing us to explore the ratcheting and constraint effects not only at the macro level but also at the subgrain level. The Finite Element (FE) analyses were complemented by detailed microstructural characterisation of the tested samples to unveil the key mechanisms contributing to the cyclic visco-plasticity damage in the FV566 steel at high temperatures. Based on this investigation, the micromechanics origin of the softening was elucidated. Moreover, the micro-damage modelling results in conjunction with the physical characterisation offered an improved mechanistic understanding of fatigue notch strengthening behaviour in multi-axial LCF tests. Importantly, an additional cyclic degradation mechanism was captured in the presence of constraints, which relates to the precipitate coarsening behaviour.

Backbone curve variations on steel building seismic response

A 4-story steel moment-frame building designed according to ASCE 7 was used in a numerical parameter study to assess the effects of modeling features on peak drift demands. Features studied included strength, stiffness, ductility, and degradation along with several hysteretic models. Attention was given to ASCE 41-type backbone curves. Of particular interest was exploring the effects of degradation, in which an adaptive backbone curve was used to capture both in-cycle and cyclic degradations. Incremental dynamic analyses (IDAs) were performed using a suite of earthquake records to assess the response over a range of shaking intensities. It was found that in-cycle degradation had more influence on the response compared to cyclic degradation for the set of ground motion records that were employed. Moreover, use of the monotonic backbone alone, with its in-cycle degradation, was sufficient. In addition, it was found that increasing strength, stiffness, and/or ductility resulted in decreased peak drift demands, whereas modifying the hysteretic type (elasto-plastic, stiffness-degrading, and pinching) had little effect on peak drifts. These findings indicate that using backbone curves based on envelopes of first-cycle test data, as done in ASCE 41, can result in overly conservative seismic response predictions.

Photocatalytic degradation of tetracycline by a Fe-doped BiMnO3 catalyst with honeycomb-like microstructure

Photocatalysis is an effective way to degrade organic pollutants. The development of catalysts with excellent activity is the basis for the practical application of photocatalysis. The activity of a catalyst is closely related to its special microstructure. Therefore, it is very important to study the effect of special microstructure on the activity of a catalyst. In this work, Fe-doped BiMnO3-based catalysts (BiMn1−xFexO3, x = 0, 0.15, 0.20, and 0.25) were synthesized by a hydrothermal method when the pH of the reaction solution was 11. The as-prepared catalysts were denoted as BMO, BMFO(015), BMFO(020), and BMFO(025), respectively. These BMFO catalysts were investigated with different characterization techniques. The photocatalytic activities of the BMFO catalysts were evaluated by degrading tetracycline (TC). Compared with the undoped BMO, the enhanced photocatalytic performance of Fe-doped BMO catalysts may be ascribed to the following factors. Doping Fe decreased the particle size of BMO and both increased the specific surface area and pore volume. Doping Fe also reduced the bandgap of BMO and improved its absorption capability in the visible region. Furthermore, Fe3+ and Fe2+ ions were introduced into the BMO lattice by doping Fe. Along with the cyclic transformation between Mn4+ and Mn3+, the cyclic transformation between Fe3+ and Fe2+ further captured photogenerated electrons (e-) to prevent carrier recombination and boost the generation of ▪O2- radicals. In particular, BMFO(020) acquired a honeycomb-like microstructure in the hydrothermal reaction. To explore the origin of forming different microstructures in BMFO(020), the other two catalysts BMFO(020)-pH= 9 and BMFO(020)-pH= 13 with different micromorphologies were prepared by adjusting the pH of the reaction solution to 9 and 13, respectively. It was found that the honeycomb-like microstructure was the most favorable to enhanced the photocatalytic performance of the BMFO(020) catalyst due to it improved light utilization, provided abundant channels for transferring and absorbing TC molecules, and decreased the recombination of carriers. Therefore, the degradation efficiency of TC solution (10 mg/L, 100 mL) reached 98.47% with 50 mg BMFO(020) after 60-min visible light irradiation. In the cyclic degradation experiment, BMFO(020) exhibited excellent stability performance, and the degradation efficiency of the TC solution was still higher than 89.55% even after 5 times recycling. Results of the trapping experiment demonstrated ▪O2- and h﹢were the main active substances. A possible mechanism for the enhancement of photocatalytic degradation to TC by the BMFO catalysts was proposed. This work highlights that doping with an adequate amount of Fe and adjusting pH of the reaction solution to form a specific microstructure is a new strategy to enhance the photocatalytic performance of BMO in degrading TC.

Synthesis and Characterization of Poly(hydroxy)urethane from Polyols for Beech (Fagus sylvatica) Wood Impregnation

A non-isocyanate route of polyurethane synthesis based on polyol (xylitol, sorbitol, glycerol, and PG3), alkyl carbonate (DMC and DEC), and diamine (HMDA, EDA, and DETA) was conducted for wood impregnation through in-site polymerization. The structure and mass average molecular weight (Mw) of the polyurethanes were analyzed using FTIR, NMR, and SEC. According to the results, polyurethane synthesis by a two-pot method in water brought cyclic carbonate degradation. The distribution of Mw of the polyurethanes showed that the most satisfying polymer (4380 g/mol) was prepared without solvent. Polyurethanes synthesized in methanol have a higher Mw than that in distilled water. In the same solvent, the use of HMDA resulted in a polymer with higher Mw than that of EDA. One-step wood impregnation in a solvent gave unsatisfactory WPG (12.59–19.71%) and LC (50.36–62.80%). However, one-step impregnation without solvent gave a higher WPG (78.39–87.63%) and a lower LC (19.11–21.25%). It is not feasible to be applied industrially. The two-step impregnation gave WPG (14.89-30.73%) and LC (42.22–56.52%). Wood impregnation using methanol or ethanol as the solvent was more recommended than using an aqueous solution. However, the resistance against leaching needs improvement. Keywords: Alkyl carbonate, diamine, polyol, polyurethane, wood impregnation

Fabrication and characterizations of Zn-doped SnO2-Ti4O7 anode for electrochemical degradation of hexafluoropropylene oxide dimer acid and its homologues

Hexafluoropropylene oxide dimer acid (HFPO-DA) and its homologues, as perfluorinated ether alkyl substances with strong antioxidant properties, have rarely been reported by electrooxidation processes to achieve good results. Herein, we report the use of an oxygen defect stacking strategy to construct Zn-doped SnO2-Ti4O7 for the first time and enhance the electrochemical activity of Ti4O7. Compared with the original Ti4O7, the Zn-doped SnO2-Ti4O7 showed a 64.4% reduction in interfacial charge transfer resistance, a 17.5% increase in the cumulative rate of •OH generation, and an enhanced oxygen vacancy concentration. The Zn-doped SnO2-Ti4O7 anode exhibited high catalytic efficiency of 96.4% for HFPO-DA within 3.5 h at 40 mA/cm2. Hexafluoropropylene oxide trimer and tetramer acid exhibit more difficult degradation due to the protective effect of the -CF3 branched chain and the addition of the ether oxygen atom leading to a significant increase in the C-F bond dissociation energy. The degradation rates of 10 cyclic degradation experiments and the leaching concentrations of Zn and Sn after 22 electrolysis experiments demonstrated the good stability of the electrodes. In addition, the aqueous toxicity of HFPO-DA and its degradation products was evaluated. This study analyzed the electrooxidation process of HFPO-DA and its homologues for the first time, and provided some new insights.

The impact of battery operating management strategies on life cycle cost assessment in real power market for a grid-connected residential battery application

The relatively short lifetime of batteries is one of the crucial factors that affects its economic viability in current electricity markets. Thus, to make batteries a more viable technology in real power market from life cycle cost assessment perspective, full understanding of battery ageing parameters and which operating control strategies cause slower degradation rate is essential and still an open problem. This study deals with the 32 different battery operating control strategies to evaluate their importance on cyclic and calendric degradation, lifetime, and life cycle cost assessment of a battery system in a grid-connected residential application. In other words, it is evaluated that at which operating control strategy the system simulation results in a more beneficial system from techno-economic perspective. A battery modelling scenario is proposed to accurately estimate battery performance, degradation, and lifetime under real operational condition given different operating control strategies. An operational strategy, which benefits from the dynamic real-time electricity price scheme, is conducted to simulate the system operation. The key results show that selecting a proper state-of-charge control strategy positively affects the battery lifetime and consequently its net-present-value, in which the best strategy led to 30% improvement in net-present-value compared to the worst strategy.

Damping Ratio of Sand Containing Fine Particles in Cyclic Triaxial Liquefaction Tests

Sand liquefaction triggered by earthquakes is a devastating geological disaster and has emerged as an engaging topic in earthquake engineering. With an enhanced understanding of pure sand liquefaction promoted by laboratory research, there is a growing concern, following filed investigations, over the influence of fine particles on the liquefaction potential of sand containing inclusions. Efforts have been devoted to clarifying the significance of certain physical indicators (e.g., plasticity index, particle shape and gradation characteristics), and fruitful conclusions can be found in the published literature. However, the relationship between the content of fine particles and the cyclic degradation in liquefaction process seems still unclear. To fill this knowledge gap, three sets of cyclic triaxial tests were performed on various sand–fines mixtures with the dry tamping method. The experimental results revealed that (i) fine particles provided a negative contribution to the global soil structure; (ii) however, the damping ratio measured from the obtained stress–strain loops manifested its independence from the fines content during cyclic degradation. In this paper, we propose a shearing mechanism on the microscopic scale to explain the above contrasting observations. For a given soil fabric, the fine particles around sand-to-sand contact points probably break strong force chains, intensifying the threat of liquefaction. By contrast, these fines play the same role in favouring relative sliding between sand grains during both the loading and unloading stages. As the maximum stored energy and the energy loss per cycle are amplified with the same scaling factor, the damping ratio, defined as the ratio between them, should display a macroscopic invariance in triaxial tests.

P-y based approach to predicting the response of monopile embedded in soft clay under long-term cyclic loading

Offshore wind turbines (OWTs) are subjected to environmental loadings such as those induced by waves or wind typically comprising up to millions of cycles (i.e., high-cycle loading). To evaluate the performance of OWTs during a lifetime cycle, this study proposed a p-y based approach to predict monopile response subjected to a long-term cyclic loading. A cyclic loading may cause an accumulation of strain and a built-up of excess pore water pressure under undrained conditions, accompanied by a corresponding reduction of stiffness and shear strength in soft marine clay. In the proposed procedure, the cyclic degradation and strain accumulation of soft clay is considered by a generalized empirical model given the soil reaction calculated from p-y analysis for a prescribed loading condition on the pile. Afterward, the response of pile subjected to a long-term cyclic loading is predicted by modifying the preselected p-y curve by p-multiplier and y-multiplier to take account for the cyclic degradation and strain accumulation, respectively. The proposed approach is validated by three centrifuge tests on a monopile in soft clay. The simulation results are in good accordance with the measurements in terms of pile displacement and bending moment versus number of applied cycles. Therefore, the proposed approach is feasible to predict the long-term pile response subjected to high-cycle loading. Moreover, it is easily implemented in the widely used p-y approach.

H-NOX Regulates Biofilm Formation in Agrobacterium Vitis in Response to NO.

Transitions between motile and biofilm lifestyles are highly regulated and fundamental to microbial pathogenesis. H-NOX (heme-nitric oxide/oxygen-binding domain) is a key regulator of bacterial communal behaviors, such as biofilm formation. A predicted bifunctional cyclic di-GMP metabolizing enzyme, composed of diguanylate cyclase and phosphodiesterase (PDE) domains (avi_3097), is annotated downstream of an hnoX gene in Agrobacterium vitis S4. Here, we demonstrate that avH-NOX is a nitric oxide (NO)-binding hemoprotein that binds to and regulates the activity of avi_3097 (avHaCE; H-NOX-associated cyclic di-GMP processing enzyme). Kinetic analysis of avHaCE indicates a ∼four-fold increase in PDE activity in the presence of NO-bound avH-NOX. Biofilm analysis with crystal violet staining reveals that low concentrations of NO reduce biofilm growth in the wild-type A. vitis S4 strain, but the mutant ΔhnoX strain has no NO phenotype, suggesting that H-NOX is responsible for the NO biofilm phenotype in A. vitis. Together, these data indicate that avH-NOX enhances cyclic di-GMP degradation to reduce biofilm formation in response to NO in A. vitis.

Experimental investigation and load-deformation analysis of reinforced concrete bridge columns under various loading cycles

Twenty reinforced concrete (RC) bridge columns were tested under constant axial compressive as well as cyclic lateral loading, to explore the effect of loading cycle numbers (3, 10, 20 cycles for a given displacement amplitude) on the seismic behavior of RC bridge columns. Test results demonstrate that the bridge column specimens under cyclic loading failed in flexural-shear mode, which was evident by the presence of diagonal cracks, buckled longitudinal reinforcement, fractured stirrup, as well as saliently pinched lateral force–displacement hysteretic curves. As the axial compression ratio increased from 0.05 to 0.15 at the aspect ratio 1.6, there was about 50% increase in their yield and peak strengths, significant decrease in ultimate displacement, and about 30% decrease in the displacement ductility in the RC bridge columns. As the aspect ratio decreased from 2.3 to 1.6 at the axial compression ratio 0.05, there was about 35% increase in their yield and peak strengths, about 40% increase in the displacement ductility in the RC bridge columns. Additionally, the effect of loading cycle numbers on the seismic behavior of RC bridge column specimens is investigated. The effect of the number of loading cycles on seismic behavior is more significant after peak load than prior to the attainment of peak strength, and the deformation capacity is significantly reduced. During post-peak loading stage increasing the loading cycle numbers accelerates damage accumulation and impairs the seismic behavior of the specimens due to substantial reduction of their energy dissipation capacity and seismic ductility. Based on the analysis of test results under varied loading cycles and monotonic lateral force–displacement curves, a calculation model of lateral force–displacement relationship considering the influence of loading cycle numbers is developed, and its effectiveness and accuracy is verified. The objective of this paper is to investigate the effect of the number of loading cycles on the seismic behavior of RC bridge columns through experimental testing. The research results would improve seismic assessment of RC bridge columns exposed to such hazards that flexural-shear failure caused by cyclic degradation.

Architecting the Z-scheme heterojunction of Gd2O3/g-C3N4 nanocomposites for enhanced visible-light-induced photoactivity towards organic pollutants degradation.

A basic calcination process in one step was employed to create g-C3N4 photocatalytic composites modified by Gd2O3 nanoparticles. SEM (scanning electron microscopy), FTIR (Fourier-transform infrared spectroscopy), XRD (X-ray diffraction), EIS (electrochemical impedance spectroscopy), PL (photoluminescence studies) as well as TEM (transmission electron microscopy), XPS (X-ray photoelectron spectroscopy), and CV (cyclic voltammetry) were employed to explain the structural traits, optical properties, and morphological features of the processed photocatalyst. The findings show that Gd2O3(Gd) does not affect the sample's crystalline structure but rather increases g-C3N4 surface area by spreading it superficially. Furthermore, Gd can redshift the light absorption peak, reduce the energy gap, and improve the efficiency with which photogenerated holes and electrons are removed in g-C3N4. The surfacemorphology of g-C3N4, in particular, could be significantly enhanced. We similarly employed three distinct photocatalytic complexes of Gd2O3 and g-C3N4 in 1:1, 2:1, and 3:1 proportions to degrade methylene blue (MB). After 100min in visible light (400-800nm), the photodegradation rate of composites is 58.8% for 1:1 (GG1), 94.5% for 2:1 (GG2), and 92% for 3:1(GG3). In addition to the MB dye, thephotocatalytic activity of synthesized materials was also studied for methyl orange. The result shows phenomenal degradation values, i.e.; for GG1 86%, GG2 96%, and for GG3 84.6%. The narrow band gap that separates the photogenerated electron and hole enhances g-C3N4 ability to degrade photo-catalytically. From the result, we concluded that the photocurrent and cyclic photocatalytic degradation of methylene blue shows that a composition of 2:1 Gd2O3/g-C3N4 has high photocatalytic stability.

Thermal decomposition synthesis of cylindrical rod-like MoO3 and irregular sphere-like Ag2MoO4 nanocrystals for accelerating photocatalytic degradation of industrial reactive dyes and biosensing application

This paper reports the thermal decomposition method to prepare a facile, one-pot synthesis of cylindrical rod-like MoO3 and irregular sphere-like Ag2MoO4 nanocrystals. The characteristic properties of MoO3 and Ag2MoO4 nanocrystals were investigated by XRD, FESEM, HRTEM, EDS, IR, UV-Vis, PL, EIS, XPS, and CV techniques. Ag2MoO4 nanocrystals result in an optical band gap to redshift, assessed by Tauc plots of the ultraviolet-visible (UV–vis) spectra. When compared to other MWCNTs modified and unmodified CPEs for the detection of the 5-Flououracil drug, the MoO3/MWCNTs/CPE showed excellent electrocatalytic activity in terms of a larger anodic peak current and an inferior peak potential. Ag2MoO4 nanocrystals shown in an excellent photocatalytic degradation efficiency of 91.39% and 57.89% for the Cibacron Deep Red C-D (CR) and Cibacron Orange C-RN (CO) dyes as compared to MoO3 as evaluated by UV–visible spectrophotometric analysis in 150 mins under 100 W visible-light irradiation. Electrochemical impedance spectroscopy has shown that the improved separation and transport of photogenerated electron-hole pairs account for Ag2MoO4’s greater efficiency than MoO3. The effects of experimental parameters for the photocatalytic degradation of dyes, including initial dye concentration of 10 mg/L, catalyst dose 75 mg, pH 7, and catalyst recycling, have been investigated to optimize reaction conditions. The primary active species were obtained to be photogenerated holes (h+) and superoxide radical anions (O2•‾). The cyclic photocatalytic degradation of CR and CO testified to Ag2MoO4’s good extent of reusability. The details of the electrochemical and photocatalytic mechanisms were then provided. Also, liquid chromatography-mass spectra (LC-MS) were used to find out the photocatalytic degradation intermediate products.

An application-oriented lithium-ion battery degradation modelling framework for ageing prediction

In battery-powered applications with high energy demands, the battery is one of the most expensive single components. Since electrochemical storages such as lithium-ion batteries are prone to a slow but steady degradation process, at some point the battery will not be able to fulfil the application’s requirements any more. Due to the high component costs, predicting the battery’s end-of-life is essential for economic operations. Generally, degradation models parametrised from laboratory ageing studies are the solution to predicting the batteries’ lifetime if the loads are known. In this work, we introduce a degradation modelling framework, which has been parametrised to depict the ageing influences of different cycle depths and state-of-charges for the calendar and cyclic degradation. It models the non-linear degradation trajectories, including variances, evaluated in a laboratory ageing study. The ageing framework deploys the degradation model to simulate the expected time, cycles and charge throughput until a given end-of-life criterion. The model and the ageing framework achieve good accuracy with almost zero verification error for the cyclic ageing degradation rate when using interval estimation with the ageing variance confidence intervals. For the point estimation, neglecting the cell’s ageing variance, we achieved MAPE=10.88% and MAPE=22.97% for the degradation rates, respectively.

A united hardening rule considering monotonic and cyclic strength degradation of clay

The strength degradation of clay subjected to monotonic or cyclic loading is a crucial factor causing nearshore or offshore marine structures instability. The monotonic shear strength softening or cyclic stiffness degradation is mainly discussed in previous degradation models, while the coupling of these two characteristics is rarely considered because of its complexity. Existing studies show that different from cyclic stiffness degradation, the post-cyclic shear strength will not eventually degenerate to zero but reach a residual shear strength, which is rarely accurately predicted by previous models. Therefore, in this paper, a united hardening rule is proposed within the bounding surface model framework, which can describe the monotonic shear strength softening, cyclic stiffness degradation, and post-cyclic strength degradation. The accuracy and validity of the proposed model are verified by experimental results.

Hysteretic model of reinforced concrete bridge piers based on earthquake damage and corrosion from saline soil

A hysteretic model of reinforced concrete (RC) bridge piers in saline soil environment, incorporating corrosion-induced overall structural degradation, is obtained based on earthquake damage by applying damage parameter. A damage analysis of the observed 13 RC bridge piers tested under cyclic loading including cracks evolution, residual deformation, relative unloading degradation, cyclic unloading stiffness degradation and strength deterioration is presented. A quantification approach for seismic damage considers the sources of deterioration: i.e., number of loading cycles and controlled displacements and incorporates a deterioration parameter aiming to control the deterioration modes. The skeleton model consists of three segments and is determined by simplifying the experimental skeleton curve. Yield strength reduction and sectional loss of reinforcement are computed to characterize the corrosion-induced degradation. It is determined that the equivalent skeleton model could match the experimental results. The applicability as well as accuracy of proposed model in simulating the hysteretic behaviours are calibrated by comparing the model with the experimental curves. The model is capable to approximate the complete hysteretic response.

A storage degradation model of Li-ion batteries to integrate ageing effects in the optimal management and design of an isolated microgrid

Li-ion batteries are being increasingly used in stationary applications, allowing for greater autonomy and facilitating the integration of renewable energies. However, these devices lose their capacity over time, especially during their so-called second life. This degradation affects the operation of the system and its cost, and must be taken into consideration if an optimal management is to be found. In this work, we present a framework for the integration of the battery aging in a microgrid design and energy management problem. To do so, we first propose a method to simplify a reference model for cyclic degradation of batteries. The results show that the battery loss of capacity shall be compute on a weekly to monthly basis to accurately keep track of degradation effects. Also, at a first order, we show that ageing is dependent with the initial battery State of Health at every update and the energy exchanged normalized by the nominal capacity. This simplified model formulated with Mixed Integer Linear Programming is integrated in a management problem of an isolated energy system for cost minimization. Optimization results show the necessary trade-off between storage degradation and overall system performances. Finally, a tailored dynamic programming is proposed to simulate successive years for the optimal sizing of the considered system in terms of battery capacity and its replacements. Compared to the proposed pproach, not accounting for the storage degradation leads to inaccurate results and significant cost underestimations (>20 %).

Simultaneous enhancement of charge transfer and light absorption via construction of atom–sharing Bi/Bi3Ti2O8F:Yb3+,Er3+ plasmonic heterojunctions for the efficient degradation of ciprofloxacin

The rational design of plasmonic heterojunction photocatalysts is crucial to achieving light capture capability and interfacial charge transfer/separation. Herein, an atom–sharing Bi/Bi3Ti2O8F:Yb3+,Er3+ (Bi/BTOFYE) plasmonic heterojunction with oxygen vacancies and upconversion function was constructed in–situ by self–sacrificing a part of Bi3Ti2O8F:Yb3+,Er3+ (BTOFYE) as source of metallic Bi. The results show that optimum Bi/BTOFYE–2 achieves the highest ciprofloxacin degradation efficiency of 70% within 120 min, with a significant promotion of 1.77 folds compared with BTOFYE. The enhancement mechanism of photocatalysis is not only derived from surface plasmon resonance, oxygen vacancies and upconversion function for the expansion of absorption spectrum and the improvement of carrier separation efficiency. Notably, in–situ interface engineering affords atomic–level close contacts and strong electronic coupling between Bi and BTOFYE, which promote interfacial charge transport and separation, as confirmed experimentally and theoretically. Additionally, the results of cyclic experiments and degradation experiments of different pollutants proved that Bi/BTOFYE was stable and nonselective. The degradation mechanism has been discussed based on the analysis of intermediates of degradation products via liquid chromatography–mass spectrometry. This study provides an idea on how to enhance photocatalysis efficiency by surface plasmon resonance of non–noble metals and makes a case for the development and design of novel atom–level contact heterojunctions.

Investigating the influence of lithium-ion batteries degradation on the parameters of the electric power storage system

This article deals with the use of a battery-based energy storage system (ESS) to ensure the required power output of power plants (PP) based on renewable energy sources (RES) integrated into the electric power system (EPS). A model of a lithium-iron-phosphate battery-based ESS has been developed that takes into account the calendar and cyclic degradation of the batteries, and the limitations of the conversion subsystem. The nominal capacity and power of the ESS is proposed to be chosen based on two levels of tolerances: the preset range of RES-based power output and the relative period of deviation from the committed power. When choosing the ESS parameters, the features of its operation, as well as restrictions on the part of the EPS, were taken into account. The developed method was applied to the EPS model including solar power plants (SPP) and wind power plants (WPP). In the end of the article, the obtained results are analyzed and the effect of the ESS operation on its residual capacity and service life is shown.

Fatigue of a cylindrical shell lying on a rigid bed

In the extractive industries of the oil and gas industry, multi-span pipelines with lodgement-type supports are widely used. In the contact area of the pipeline with the support, contact stresses arise, created by the internal pressure of the pipeline, weight and wind load, and which can change during operation depending on the load. The assessment of the service life of such pipeline structures is an urgent technical and economic problems, which allows not only to prevent man-made and environmental disasters, but also to save material. This paper presents a method for calculating the fatigue of a steel cylindrical shell that is in contact with a rigid or elastic support of the lodgement type. Shell fatigue analysis is performed for contact stresses, which are determined by solving the corresponding contact problem. When calculating the fatigue of the shell, the linear damage summation hypothesis and the modified model of cyclic degradation of the material were used.