Number Of Cycles Research Articles

Effect of multifunction cavitation on microstructure and plane bending fatigue properties of low-alloy steel

Multifunction cavitation (MFC) has potential as an environmentally friendly surface-modification method. In the present study, the modified surface layer and the fatigue properties for MFC-processed low-alloy steel were investigated. When the processing time was longer than 2 min, the surface roughness increased and the surface potential decreased. The maximum compressive residual stress was induced after a processing time of 2 min, and decreased for longer processing times. Electron backscatter diffraction analysis of a cross section of a sample subjected to MFC for 30 min showed that the modified layer was thicker than that for samples processed for shorter times. The fatigue life at high cycle numbers increased for the specimens processed by MFC under the conditions corresponding to the greatest compressive residual stress. MFC processing was shown to be effective in improving the fatigue properties of steel, and therefore has potential as a next-generation surface-modification method.

Study on the bond properties between BFRP bars and hybrid fibers reinforced recycled concrete under freeze-thaw cycles

To study the bond properties between basalt fiber reinforced polymer (BFRP) bars and hybrid fibers which were basalt fiber (BF) and polypropylene fiber (PF) reinforced recycled concrete under freeze-thaw cycles, conducting center pull-out tests to study the effects of three factors on the bond properties: the number of freeze-thaw cycles, the volume fractions of single fiber, and the volume fractions of hybrid fibers. Based on the data obtained from the test, establishing a four-stage bond-slip constitutive relationship model. The results showed that the failure modes were pull-out failure and splitting failure. The bond strength decreased when adding the single fiber, with a maximum reduction of 13.18%, but the peak slip increased, with a maximum increase of 69.92%. When the volume fraction of BF was 0.3%, it achieved the optimal effect. The bond strength and peak slip increased when adding hybrid fibers, with maximum increases of 13.47 and 130.08%, respectively. However, excessive fiber content will reduce the increase of bond strength. The bond strength between BFRP bars and hybrid fiber-reinforced recycled aggregate concrete (HFRAC) increased when the number of freeze-thaw cycles increased but decreased when the number of freeze-thaw cycles exceeded 50. The four-stage bond-slip constitutive relationship model fitted well with the bond-slip curves. Compared with other fiber-reinforced recycled concrete specimens, this model fitted better with the curves of HFRAC specimens after freeze-thaw cycles and had the best fitting effect for the internal crack slip stage of the curves.

Effect of high-temperature thermal fatigue on mode I fracture toughness of gabbro

Investigating variations of rock fracture toughness after high-temperature thermal fatigue is greatly significant for developing deep geothermal resources. This study investigated the mode I fracture toughness of gabbro after high-temperature fatigue treatment by heating a cracked straight-through Brazilian disc (CSTBD) gabbro specimen to 200, 400, 500, and 600 °C, followed by 100 thermal cycles. Additionally, acoustic emission (AE) and digital image correlation (DIC) were used to monitor the failure process of gabbro. The results showed that the peak load, fracture toughness, and fracture energy of gabbro decreased with the increased temperature and number of cycles, which was most significant at 500 and 600 °C. Under mode I loading, cracks developed along the loading direction and connected with the prefabricated crack. Additionally, the regions with higher von Mises equivalent strain (Evm) values were concentrated at the loading points and prefabricated crack of the rock sample. The degree of bending of the primary cracks increased, the number of secondary cracks increased, and the Evm values changed significantly as the temperature increased. The phase transformation of plagioclase feldspar at 450 °C and the oxidation of iron- and magnesium-containing pyroxene at 600 °C changed the internal structure of the rock. Cyclic treatment further exacerbated the thermal damage, developing microcracks within the rock and reducing fracture toughness significantly.

Recovery of DNA from acetaminophen exploring physical state and sampling methods

Research into the recovery of DNA from illicit drug samples has shown it is possible to get forensically useful profiles from such substrates. However, it is not yet known if the different physical states that drugs can be found in influences the quantity and quality of DNA that can be recovered or what is the best sampling method to adopt for powdered samples. This research used acetaminophen in four different states – large crystalline, powder, in solution, or residue – to determine the efficacy of current DNA technology in recovery and analysis of the resulting sample. Five replicates of each were prepared. Human blood was deposited on or mixed with the drug and left for 1 hour. The surface of the drug was sampled by wet/dry swabbing (where appropriate), or the entire sample was deposited in a tube, and the DNA then extracted using DNA-IQ™. The amount of DNA recovered (ng), degradation index, number of PCR cycles (Ct) required for the IPC to reach threshold, number of alleles in the DNA profile and average peak height (APH) were assessed. All samples, irrespective of the physical state they were collected from, returned full DNA profiles that corresponded to the DNA profile of the blood donor, with no degradation or inhibition detected. It was also found the wet/dry swabbing method returned higher levels of DNA than inclusion of the entire sample into the tube for powdered acetaminophen and the appropriate method to use will be dependent on casework circumstances. The findings of this research further develops our understanding of the recovery of DNA from drugs, and supports the need for further investigation to understand under what conditions DNA can be recovered from illicit substances.

Analysis of damage models and mechanisms of mechanical sand concrete under composite salt freeze–thaw cycles

Mechanical sand concrete (MSC) deterioration in bridge engineering within cold-salt environments in the West was investigated. This study evaluated the salt-freezing resistance and damage models of granite mechanical sand concrete (GMSC) and tuff mechanical sand concrete (TMSC) under composite salt freezing-thaw cycles, using multiple indicators such as mass loss, relative dynamic elastic modulus, flexural strength, and compressive strength. A mechanistic study on the evolution of microscopic pores was conducted using nuclear magnetic resonance technology. The results showed that with an increase in composite salt freeze–thaw cycles, both TMSC and GMSC exhibited a decreasing trend in all indicators except for mass loss, which initially decreased and then increased. The relative dynamic modulus of elasticity decreased by 13.8 % and 17.4 % after 125 freeze–thaw cycles for TMSC and GMSC; compressive strength decreased to 36.16 MPa and 35.01 MPa; and flexural strength decreased to 4.977 MPa and 4.973 MPa, respectively. Combined with the T2 spectrum analysis of NMR, it can be seen that with the increase of the number of freeze-thaw cycles of the composite salt, the internal porosity of the TMSC structure increases from 1.91 % to 2.55 %, and the GMSC from 2.1 % to 2.86 %, and the harmful pore percentage increases by 1.73 times and 1.75 times, in turn, compared with that before the freeze-thaw.Thus, TMSC demonstrated superior salt-freezing resistance compared to GMSC. This study offers a reference and guidance for adopting MSC in cold and salty western regions.

Study on the Degradation Law of Physical and Mechanical Properties of Granite under the Action of Freeze-thaw Cycle

This study demonstrates the effect on the mechanical properties of granite through the freeze-thaw cycle test method, and investigates the mechanical property parameters and its changing law of the rock samples under different numbers of freeze-thaw cycles. The results show that with the increase of the number of freeze-thaw cycles, the physical property parameters such as mass and longitudinal wave speed of the samples show a tendency of attenuation. Mechanical property parameters such as peak strength and elastic modulus of the specimen also showed a trend of decay.

Water-Based Bi2S3 Nano-Inks Obtained with Surfactant-Assisted Liquid Phase Exfoliation and Their Direct Processing into Thin Films

Bi2S3 has gained considerable attention as a semiconductor for its versatile functional properties, finding application across various fields, and liquid phase exfoliation (LPE) serves as a straightforward method to produce it in nano-form. Till now, the commonly used solvent for LPE has been N-Methyl-2-pyrrolidone, which is expensive, toxic and has a high boiling point. These limitations drive the search for more sustainable alternatives, with water being a promising option. Nonetheless, surfactants are necessary for LPE in water due to the hydrophobic nature of Bi2S3, and organic molecules with amphoteric characteristics are identified as suitable surfactants. However, systematic studies on the use of ionic surfactants in the LPE of Bi2S3 have remained scarce until now. In this work, we used sodium dodecyl sulfate (SDS), sodium dodecylbenzene sulfonate (SDBS) and sodium hexadecyl sulfonate (SHS) as representative species and we present a comprehensive investigation into their effects on the LPE of Bi2S3. Through characterizations of the resulting products, we find that all surfactants effectively exfoliate Bi2S3 into few-layer species. Notably, SDBS demonstrates superior stabilization of the 2D layers compared to the other surfactants, while SHS becomes the most promising surfactant for obtaining products with high yield. Moreover, the resulting nano-inks are used for fabricating films using spray-coating, reaching a fine tuning of band gap by controlling the number of cycles, and paving the way for the utilization of 2D Bi2S3 in optoelectronic devices.

Experimental study on response and precursor of pressure stimulated currents of combined coal-rock under cycling stress

The coal-rock combination body is prone to rock burst and surface subsidence under loading, and adopting effective monitoring methods are valuable. In this paper, cyclic loading and unloading (CLU) tests were conducted to investigate the response and precursor of pressure stimulated currents (PSCs) in coal-rock combination samples. The results indicate that the PSCs of the coal-rock combination samples have good response characteristics to stress. Furthermore, the PSCs between the two components are significantly larger and more stable than those of the coal body, which can clearly reflect the failure under a progressive failure mechanism and are related to the difference in the resistivities and microstructures of the components. During the CLU tests, the PSCs of each cycle are well fitted by the Gaussian distribution and have a memory effect. During the loading or unloading process of each cycle, the variation in PSCs with stress conforms to the power function relationship with exponent k. As the cycle number increases, the rates of increase in PSC under stress are gradually weakened, and the indexes of PSCs including exponent k increase or decrease sharply first and then remain stable or even decrease, which is due to the loading history. The stable state of these indexes with obvious inflection points in later cycles of CLU tests can be considered a precursor of coal-rock failure. The PSC flow direction between the two components is exactly opposite to that in the coal body. The results provide new ideas for the monitoring and prediction of coal-rock combination body failure, which is helpful for the prevention of geological disasters in mines.

An audit of adherence to National Cancer Care Programme chemotherapy regimens and prescribing standards in systemic anti-cancer therapy prescriptions in an Irish hospital

Abstract Introduction The availability and usage of systemic anticancer therapy (SACT) has increased significantly over recent years. Whilst SACT has undeniably benefited patients, it also poses a challenge to patient safety as the number of cytotoxic drugs increases. The National Cancer Care Programme (NCCP) has set out to design and implement national policies and practices for oncology medicine in Ireland in order to maintain high levels of patient safety. Aim This study aims to evaluate adherence to NCCP national SACT regimens and prescribing standards at an Irish hospital. Methods This study was a prospective analysis involving an audit of SACT prescriptions for adherence to NCCP regimens and prescribing standards. The study was conducted from June 6th to June 30th 2023; the cohort was defined as patients who were receiving cancer services’ treatment from the medical oncology and haematology department at the hospital. The data collection tool was developed using template in the NCCP Oncology Medication Safety Review Report 2014. A report was run to identify outpatient patients who received SACT on each working day. For inpatients, a daily scheduling Excel file was consulted. Prescriptions were evaluated to complete the data collection tool. Anonymised data was captured and the results were collated to show any trends in adherence to NCCP regimens and prescribing standards. Descriptive analysis of patient and clinical characteristics was performed. Results Pharmacy prescription records of all patients who received SACT during the four-week study period were analysed. A total of 410 SACT prescriptions were reviewed. The median patient age in the study cohort was 59 years (range 23-93 years). Overall, 86.3% of the audited prescriptions adhered to NCCP regimens. The oncology department exhibited a higher adherence rate of adherence to NCCP regimens compared to the haematology department (89.2% versus 82.3%). Melanoma, non-small cell lung cancer, small cell lung cancer, renal cell, prostate, sarcoma, and bladder cancer all had 100% adherence. The lowest adherence rates occurred for CNS (25%), mesothelioma (50%), leukaemia (76.5%), and metastatic colorectal cancer (77.3%). Only 7% of prescriptions were written on pre-printed forms. In this audit, over 98% compliance was observed for eleven of the twenty-four NCCP prescribing standards in the 410 prescriptions: including patient name, patient date of birth, diagnosis, name of supervising consultant, protocol/regimen name, name of drug(s), dose in mg or mg/m2, route of administration, signature of the prescriber and date prescribed. Areas for improvement identified include information about ward/clinic, renal/hepatic function, start date, cycle numbers and medical council numbers. Conclusion This is the first audit of adherence to NCCP regimens using prescription data in Ireland, and the inclusion of 410 samples is a strength; however, the data are from a single site. This study has highlighted areas for improvement in prescribing practices. It emphasises the need for further multidisciplinary team education on adherence to NCCP regimens and prescribing standards. Healthcare professionals should ensure that pre-printed SACT prescription forms are used where available. Additionally, the use of regimen-specific pre-printed forms should be expanded.

Robust Superconductivity in Infinite-Layer Nickelates.

The recent discovery of nickelate superconductivity represents an important step toward understanding the four-decade mastery of unconventional high-temperature superconductivity. However, the synthesis of the infinite-layer nickelate superconductors shows great challenges. Particularly, surface capping layers are usually unitized to facilitate the sample synthesis. This leads to an important question whether nickelate superconductors with d9 configuration and ultralow valence of Ni1+ are in metastable state and whether nickelate superconductivity can be robust? In this work, a series of redox cycling experiments are performed across the phase transition between perovskite Nd0.8Sr0.2NiO3 and infinite-layer Nd0.8Sr0.2NiO2. The infinite-layer Nd0.8Sr0.2NiO2 is quite robust in the redox environment and can survive the cycling experiments with unchanged crystallographic quality. However, as the cycling number goes on, the perovskite Nd0.8Sr0.2NiO3 shows structural degradation, suggesting stability of nickelate superconductivity is not restricted by the ultralow valence of Ni1+, but by the quality of its perovskite precursor. The observed robustness of infinite-layer Nd0.8Sr0.2NiO2 up to ten redox cycles further indicates that if an ideal high-quality perovskite precursor can be obtained, infinite-layer nickelate superconductivity can be very stable and sustainable under environmental conditions. This work provides important implications for potential device applications for nickelate superconductors.

Development of electrode by using gold-platinum alloy nanopar¬ticles for electrochemical detection of serum amyloid A protein

Gold-platinum alloy nanoparticles (AuPtNP) were electrochemically deposited on the surface of indium-tin-oxide (ITO) modified with (3-aminopropyl)triethoxysilane (APTES), after optimizing deposition conditions for the electroplating solution and number of deposition cycles. Different part ratios of Au/Pt used were 4/0, 3/1, 2/2, 1/3 and 0/4 (AuNP, Au3Pt1, Au2Pt2, Au1Pt3 and PtNP, respectively) in preparation of 1 mM solutions. FE-SEM, EDAX and XRD surface characterization techniques were used to confirm the presence of deposited AuPt alloy nanoparticles on the modified ITO surface. Electrochemical methods (CV, DPV and EIS) were used to investigate the electrochemical properties of prepared electrodes in the presence of ferri/ferrocyanide redox couple, which indicated the following increasing order of electrocatalytic peak current: Au < Au2Pt2 < Pt < Au1Pt3 < Au3Pt1. The most active electrode, Au3Pt1NP/APTES/ITO (with Au/Pt part ratio 3:1), was further used to fabricate the immunoelectrode SAA-Ab/Au3Pt1NP/APTES/ITO. The prepared immunoelec­trode was tested for detection of serum amyloid A protein biomarker (APO-SAA) by immobilising SAA-specific antibodies (SAA ½ Ab) on its surface. Sensing studies on this immunoelectrode, performed by DPV technique, revealed the SAA biomarker detection in the linear range of 10 to 106 fg ml-1. The limit of detection was calculated as 7.0 fg ml-1.

Experimental investigation and optimization of modification during coaxial waterjet-assisted femtosecond laser drilling

Waterjet-assisted laser drilling technology facilitates the fabrication of high-quality micro-holes by utilizing the collaborative benefits of waterjets and lasers. In this study, the coaxial waterjet-assisted laser drilling (CWALD) technique was employed to improve the properties of micro-holes during femtosecond laser drilling. Based on computational fluid dynamics (CFD) simulations, the stability of the waterjet was initially verified by optimizing the structure of the watercourse and nozzle shape in the CWALD device. Furthermore, a comparative experiment between laser direct drilling (LDD) and CWALD revealed that while CWALD can produce well-rounded micro-holes with a high aspect ratio, it exhibits lower efficiency and results in a larger heat-affected zone (HAZ). To address these drawbacks associated with CWALD, a two-step coaxial waterjet-assisted composite laser drilling (TS-CWALD) method was proposed. TS-CWALD involves applying CWALD for secondary modification of micro-hole shape following LDD with punching. This modification process is pivotal for enhancing drilling accuracy but requires consideration of multiple parameters. For this purpose, regression models were established for the inlet diameter, outlet diameter, and taper; response surface methodology was then employed to optimize these parameters. Subsequently, interactive effects analysis was conducted on different responses based on laser pulse energy, frequency, modification speed, and number of modification cycles. The adequacy of the developed models was subsequently verified using analysis of variance methods. Finally, the successful fabrication of a film hole with an inlet diameter of 205 μm and an outlet diameter of 200 μm, featuring a taper of only 0.2°, was achieved ultimately through meticulous parameter optimization. Furthermore, the micro-hole retained a minimal HAZ. The optimized parameters encompassed a pulse energy of 20.6 μJ, frequency of 127 kHz, modification speed of 3 mm/s, and shape modification carried out over 335 cycles.

Performance of Recycled Polylactic Acid/Amorphous Polyhydroxyalkanoate Blends.

Blends of polylactic acid (PLA) with amorphous polyhydroxyalkanoate (aPHA) are less brittle than neat PLA, thus enabling their use as biodegradable packaging. This work investigated the impact of recycling on the properties of neat PLA and PLA/aPHA blends with 90 and 75 wt. % PLA. After the materials were subjected to five heat histories in a single-screw extruder, the mechanical, rheological, and thermal properties were measured. All recycled compounds with 100% PLA and 75% PLA had similar decomposition behavior, whereas the decomposition temperatures for the blends with 90% PLA decreased with each additional heat cycle. The glass transition and melting temperatures were not impacted by reprocessing, but the crystallinity increased with more heat cycles. The complex viscosity of the reprocessed PLA and PLA/aPHA blends was much lower than for the neat PLA and increasing the number of heat cycles produced smaller reductions in the complex viscosity of 100% PLA and the blend with 90% PLA; no change in complex viscosity was observed for blends with 75% PLA exposed to 2 to 5 heat cycles. The tensile properties were not affected by reprocessing, whereas the impact strength for the 75% PLA blend decreased with reprocessing. These properties suggest that users will be able to incorporate scrap into the neat resin for thermoformed packaging.

Evaluation of freeze-thaw resistance of geopolymer concrete incorporating GFRP waste powder

This study investigates the use of glass fiber reinforced polymer (GFRP) waste powder as a partial replacement for cementitious materials in the synthesis of geopolymer concretes (GPCs), focusing on their durability under freeze-thaw (F-T) conditions. Two types of binary GPCs were synthesized: GFRP powder/ground granulated blast furnace slag (GGBS)-based GPC and GFRP powder/fly ash (FA)-based GPC, with a GFRP powder weight content of 30 %. Single GFRP powder-based, GGBS-based and FA-based GPCs were prepared as reference materials. The F-T resistance was evaluated through mass loss and residual compressive strength (RCS), as well as examining the microstructure using scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP). Results demonstrated that the mass loss of all GPC samples remained below the critical value of 5 % after 300 cycles. The incorporation of 30 wt% GFRP powder into GGBS-based GPC resulted in improved resistance to F-T damage, increasing the number of cycles endured from 200 to 300. Similarly, adding 30 wt% GFRP powder to FA-based GPC demonstrated enhanced resistance to F-T deterioration, with the number of cycles increasing from 150 to 175. The pore distributions of GFRP powder/FA-based GPC remained relatively unchanged before 200 F-T cycles, indicating it effective resistance against F-T conditions. GFRP powder/GGBS-based GPC exhibited a more uniform and denser microstructure with a reduced presence of pores, even after enduring 300 F-T cycles, making it better equipped to withstand F-T cycles. Furthermore, prediction models were developed to estimate RCS and damage evolution due to F-T conditions, producing accurate results compared to test data. This study presents an effective method for the utilization of GFRP waste as a building material in cold environments.

Microstructure and deterioration mechanism of hydraulic concrete under variable temperature dry-wet cycles

In the variable water level area, hydraulic concrete structures are susceptible to variable temperature and alternating dry-wet cycles, especially for thin-walled structures. To elucidate alterations in the microstructure and strength of hydraulic concrete subjected to variable temperature dry-wet cycles, this paper firstly conducted a durability test on hydraulic concrete. Subsequently, CT scan images of the specimens are acquired during the variable temperature dry-wet cycle. Secondly, in view of the shortcomings of existing threshold methods for CT image pore segmentation, a new image segmentation method (RASLPSO-TV-Top-hat) is proposed by using Tensor voting and Top-hat technology, combined with a Reverse Adaptive Particle Swarm Optimization algorithm with Self-Learning ability. The evolution process of pore structure (microcracks) of hydraulic concrete under the variable temperature dry-wet cycles is captured. Thirdly, an in-depth analysis is conducted on the compressive strength and acoustic emission characteristics. The analysis shows that with the number of cycles increases, there is a discernible interconnection among the pore structures. This interconnection leads to a noteworthy reduction in the compressive strength of the concrete. Additionally, the cumulative number of Acoustic Emission ringing events exhibits an initial rise followed by a subsequent decline. The study successfully identifies the patterns governing the deterioration of strength and microstructure evolution in hydraulic concrete. The mechanism underlying the decline in performance of hydraulic concrete under variable temperature dry-wet cycles is elucidated. It provides a reliable and valuable basis for the safety assessment of hydraulic concrete structures in the variable water level area.

Monitoring the crack lengths in composite lap joints under cyclic loading

Abstract Monitoring crack lengths in composites lap joints is crucial for the evaluation of safety and integrity in composite structures. The crack lengths in adhesively bonded single-lap and double-strap joints were characterized by using epoxy adhesive containing aligned graphene. The epoxy adhesive was prepared by adding graphene to epoxy resin and then aligning the graphene through an electrical field. The incorporation of 0.15wt% aligned graphene can have the epoxy adhesive being electrically conductive. The single-lap and double-strap joints containing the graphene epoxy adhesive were tested under cyclic loading. During the cyclic tests, the crack extension and electrical resistance were measured concurrently. In addition, the electrical resistance model expressed in terms of the crack lengths for the lap joints was proposed in the examination. The results illustrated that the crack length and the electrical resistance increased as the cyclic number increased. Moreover, the experimental resistance variation associated with the increased crack length can be described using the electrical resistance model. Thus, the functionalized epoxy adhesive containing aligned graphene can be employed for effectively detecting the length of cracks in composite lap joints under cyclic loading.

Generalized coefficients of clustering in (un)directed and (un)weighted networks: An application to systemic risk quantification for cryptocoin markets

A coefficient of clustering is one of the important network parameters to describe clustering characteristics around a node in a network. It accounts for the number of cycles of length 3 (triangles) relative to the number of paths of length 2 in which this node participates as their inner node. In practice, the number of longer paths and cycles may be larger than the number of 2-paths and 3-cycles, thereby requiring its generalized version. In this paper, we aim at proposing the so-called λ-clustering coefficient to characterize the node clustering tendency at level λ≥3. We define it by counting the number of λ-cycles relative to the number of (λ−1)-paths containing a fixed inner node. In addition, we introduce the total clustering coefficient by considering the total number of all cycles relative to the total number of all paths consisting of this inner node. We formulate these generalized clustering coefficients for each of the following cases: undirected and unweighted networks, undirected but weighted networks, directed but unweighted networks, and directed and weighted networks. We then implement them for correlation- and conditional risk measure-based networks that represent conventional cryptocurrency markets and stablecoin markets. They can be viewed as new measures of systemic risk. The larger their values, the larger the tendency of risk transmission from one market to other subsequent markets forming longer cycles, and therefore the higher the systemic risk level. The systemic risk quantification is appropriate when they fulfill certain properties. In summary, the novelty of this study lies in the mathematical formulation of the generalized clustering coefficients and their computation for the cryptocoin networks with the purpose of appropriately managing systemic risk in the represented cryptocoin markets.

Evaluation of matrix crack growth in interlaminar toughened quasi-isotropic carbon-fiber reinforced plastic laminates up to the very-high cycle regime by ultrasonic fatigue testing

It is time-consuming to conduct conventional hydraulic fatigue testing up to the very-high cycle fatigue (VHCF, N (number of cycles) ≥ 108) regime. Ultrasonic fatigue testing has been proposed as an accelerated alternative method. In this study, ultrasonic fatigue testing was conducted on interlaminar toughened quasi-isotropic carbon-fiber reinforced plastic (CFRP) laminates to evaluate the characteristics and mechanism of fatigue up to the VHCF regime. Hydraulic fatigue tests were conducted at the same stress ratio as a comparison. The resulting S–N diagrams showed a lower fatigue strength and different fatigue mechanisms for specimens subjected to ultrasonic fatigue tests compared with those subjected to hydraulic fatigue tests. The observed growth of the matrix crack density in each laminate layer was used to perform a shear-lag analysis to calculate the energy release rate considering off-axis matrix cracks. The results suggested different damage growth behaviors for specimens subjected to ultrasonic and conventional fatigue tests.

Improving SiO2 to SiNx etch selectivity during atomic layer etching with multiple selective organic pre-functionalization steps

Selective thermal pre-functionalization of plasma-deposited SiNx surface with benzaldehyde has been shown to facilitate the formation of a carbon-rich hydrofluorocarbon layer, which retards the etch of SiNx, thereby increasing the etch selectivity of SiO2 to SiNx during atomic layer etching (ALE). However, in technological applications in device manufacturing, the SiNx layer is often buried under the SiO2 layer or has been exposed to the atmosphere. This leads to low uptake of benzaldehyde on the SiNx surface either due to a residual CFx layer or due to the formation of surface SiOxNy. Using in situ attenuated total reflection Fourier transform infrared spectroscopy, we show that the selectivity for benzaldehyde attachment to SiNx over SiO2 is reduced with the slow accumulation of a fluorocarbon residue on both surfaces with an increasing number of ALE cycles. Using in situ ellipsometry, we show that if the two surfaces are dosed with benzaldehyde after the first and fifth ALE cycles, there is a nearly 60% increase in etch selectivity compared to dosing benzaldehyde once after the first ALE cycle. A nearly 100% improvement in etch selectivity was observed compared to the scenario without benzaldehyde pre-functionalization for a target SiO2 etch of ∼20 nm in 20 ALE cycles.

Unsupervised dynamic prognostics for abnormal degradation of lithium-ion battery

Lithium-ion batteries may suffer an abnormal degradation defined by a significantly accelerated performance drop after a period of linear and low-rate degradation, resulting in severe danger to operational safety and reliability. Existing supervised data-driven prognostics for abnormal degradation rely heavily on adequate high-quality training samples, thus hindering their real-world utilization. Therefore, this paper develops an unsupervised dynamic prognostics framework that is dynamically executed as the cycle number increases to provide accurate and timely warnings for abnormal degradation. In the framework, an extended asymmetric quantum clustering (EAQC) can preliminarily identify the risky battery with the abnormal degradation trend. Its use of multi-dimensional feature degradation rates and potential function for clustering makes it outperform other density-based clustering methods. Then, for the identified battery, a time-varying double-layer autoregression (TVDLAR) can accurately predict its knee point of abnormal degradation. TVDLAR produces much earlier warning than other autoregression methods, which owes to its modeling ability of the time-varying correlation in battery historical degradation data. Through applying to two experimental datasets consisting of 174 lithium-ion batteries of different types under various working conditions, the framework is proven highly effective and shows significant superiority over some alternative approaches; all abnormal degradation can be timely warned before the corresponding knee points, and the average earlier warning cycles are 86 and 116, respectively. Compared with supervised data-driven methods, the proposed unsupervised dynamic prognostics framework has the advantages of low data requirement, low computational consumption, and good interpretability, indicating its substantial potential for application.