Cycle Ratio Research Articles

Spontaneously Blinkogenic Probe for Wash‐Free Single‐Molecule Localization‐Based Super‐Resolution Imaging in Living Cells

Single‐molecule localization super‐resolution fluorescence imaging relies on the fluorescence ON/OFF switching of fluorescent probes to break the diffraction limit. However, the unreacted or nonspecifically bound probes cause non‐targeted ON/OFF switching, resulting in substantial fluorescence background that significantly reduces localization precision and accuracy. Here, we report a blinkogenic probe HM‐DS655‐Halo that remains blinking OFF until it binds to HaloTag, thereby triggering its self‐blinking activity and enabling its application in direct SMLM imaging in living cells without wash‐out steps. We employed the ratio of the duty cycle before and after self‐blinking activation, termed as the parameter "RDC" to characterize blinkogenicity. The covalent binding to HaloTag induces HM‐DS655‐Halo to transition from a fluorescent OFF state to a fluorescence blinking state. This transition also leads to a change in the RDC value, which is calculated to be 12, ensuring super blinkogenicity to effectively suppress background signals in living cells. HM‐DS655‐Halo was successfully applied in dynamic SMLM imaging of diverse intracellular sub‐structures with minimal background noise, including mitochondrial fission and contact, cell migration, and pseudopod growth.

Spontaneously Blinkogenic Probe for Wash-Free Single-Molecule Localization-Based Super-Resolution Imaging in Living Cells.

Single-molecule localization super-resolution fluorescence imaging relies on the fluorescence ON/OFF switching of fluorescent probes to break the diffraction limit. However, the unreacted or nonspecifically bound probes cause non-targeted ON/OFF switching, resulting in substantial fluorescence background that significantly reduces localization precision and accuracy. Here, we report a blinkogenic probe HM-DS655-Halo that remains blinking OFF until it binds to HaloTag, thereby triggering its self-blinking activity and enabling its application in direct SMLM imaging in living cells without wash-out steps. We employed the ratio of the duty cycle before and after self-blinking activation, termed as the parameter "RDC" to characterize blinkogenicity. The covalent binding to HaloTag induces HM-DS655-Halo to transition from a fluorescent OFF state to a fluorescence blinking state. This transition also leads to a change in the RDC value, which is calculated to be 12, ensuring superblinkogenicity to effectively suppress background signals in living cells. HM-DS655-Halo was successfully applied in dynamic SMLM imaging of diverse intracellular sub-structures with minimal background noise, including mitochondrial fission and contact, cell migration, and pseudopod growth.

Damage Proportion Analysis of the Combined High and Low Cycle Fatigue Based on the Continuum Damage Mechanics

ABSTRACTA combined high and low cycle fatigue (CCF) life prediction model, considering creep, low‐cycle fatigue (LCF), high‐cycle fatigue (HCF) at the maximum LCF nominal stress (HLCF) damages, and the interaction damage between LCF and HLCF, is proposed. The proportions for these four types of damage in total CCF damage are quantified. Compared with the existing CCF models, the CCF model proposed in this paper considers creep damage in CCF and has higher accuracy. The escalation in HCF stress amplitudes leads to reduced CCF life owing to the augmentation of HLCF and interaction damages. The increase in the cycle ratio of HCF to LCF, causing a reduction in CCF life is ascribed to elevated HLCF and creep damages. The calculated damage proportion results from the proposed model are consistent with the observations of the fracture characteristics using a scanning electron microscope (SEM), indicating the necessity of considering creep damage in CCF life prediction at high temperatures.

An in vitro study of irrigation rate, operator duty cycle and intrarenal temperature in superpulse fiber thulium laser lithotripsy

ObjectiveThe present study aimed to examine the relationship between irrigation velocity, operator duty cycle (ODC), and intrarenal temperature during retrograde intrarenal surgery with a superpulse fiber thulium laser.MethodsPlace the stones into the fresh isolated porcine kidneys, use puncture needle to place the temperature probe 2 mm around the stones, and place the pressure probes in the upper calyx, lower calyx, and renal pelvis. Place the entire setup in a 37 °C constant temperature water bath to simulate the human body environment. The laser power varies between 10 and 30 W, and the irrigation speed is 10-30 ml/min. Additionally, at a laser power of 20 W and an irrigation speed of 10 ml/min, different On-Duty Cycles (ODC) are set. Monitor the changes in temperature and pressure.ResultsA direct proportionality of temperature in the kidney to the rate of irrigation has been reported between 10 W and 30 W laser powers. The percentage ratio of the rate of irrigation and power in the laser is 1:1, which can keep the temperature in the kidney at a safe level. At a laser power of 20 W and irrigation of 10 ml/min, the temperature inside the kidney increases sharply with the increase in ODC. By decreasing the ratio of ODC, the increase of temperature inside the kidney can be brought to a great reduction.ConclusionMaintaining a 1:1 ratio between laser power and irrigation speed can effectively prevent thermal damage or injury to kidney tissue.Additionally, by adjusting the On-Duty Cycle (ODC) ratio, the intrarenal temperature can also be reduced.

Ultrasound-assisted synthesis of methyl acrylate using Amberlyst-15 catalyst: optimization using response surface method

Ultrasound-assisted synthesis of methyl acrylate was performed in a solvent-free ultrasound batch reactor using acid ion exchange resin (amberlyst-15) as a heterogeneous catalyst. Influence of different reaction parameters such as temperature (40-70°C), alcohol to acid mole ratio (2-8), catalyst loading (0-10 % w/w), and addition of molecular sieves (0-8%), ultrasound power (0-120W), and duty cycle (20-80%) on the activity of reaction were investigated through one parameter at a time. Further, four significant parameters were optimized using response surface methodology using a central composite design. The maximum conversion of acrylic acid 61.02 %, was obtained at optimum reaction conditions at 61°C reaction temperature, 6.5 alcohol to acid mole ratio, 7.85% catalyst loading, and 60% ultrasound duty cycle. The equilibrium conversion improved from 29.2% to 61.02%, with a significant decrease in reaction time as compared to the conventional approach.

Evaluation of the impact of customized serum-free culture medium on the production of clinical-grade human umbilical cord mesenchymal stem cells: insights for future clinical applications

BackgroundThe selection of suitable culture medium is critical for achieving good clinical outcomes in cell therapy. To support the commercial application of stem cell therapy, customized culture media not only need to promote stem cell proliferation, but also need to save costs and meet industrial requirements for inter-batch consistency, efficacy, and biosafety. In this study, we developed a series of serum-free media (SFM) and elucidated the effects between different SFM, as well as between SFM and serum-containing meida (SCM), on human umbilical cord mesenchymal stem cells (hUC-MSCs) phenotype and function. We analyze and emphasize from the perspectives of clinical and commercial application why research on customized culture media is critical for the success of enterprises developing novel cellular therapeutics.MethodsWe cultured hUC-MSCs with identical cell seeding densities in different formulations of SFM and SCM until passage 10 and examined the changes in cell phenotype and function. We analyzed the results with the commercial application requirments of the cellular therapy industry to assess the potential impact of customized culture media on inter-batch consistency, efficacy, stability, biosafety, and cost-effectiveness of industrial-scale cell production.ResultshUC-MSCs cultured in SCM and SFM exhibit consistent cell morphology and surface molecule expression, but hUC-MSCs cultured in SFM demonstrate higher activity, superior proliferative capacity, and greater stability. Furthermore, hUC-MSCs cultured in different SFM exhibit differences in cell activity, proliferative capacity, senescent rate, and S/M ratio of cell cycle, while maintaining a normal karyotype after long-term in vitro cultivation. Moreover, we found that hUC-MSCs cultured in different media exhibit variations in paracrine capacity and in their support of hematopoietic stem cell (HSC) self-renewal.ConclusionConsidering the substantial funding and time required for cell-based drug development, our results underscore the importances of comprehensively optimizing the composition of medium for the specific disease prior to conducting clinical trials of cell-based therapies. The criteria for selecting culture medium should be based on the requirements of the target disease for cellular function. In addition, we provide a way to formulate different customized SFM, which is beneficial for the development of cell therapy industry.

Experimental investigations on combined high and low cycle fatigue: Material-level specimen design and strain response characteristics

The paper designs a novel material-level specimen and its dedicated fixture suitable for applying Combined high- and low- Cycle Fatigue (CCF) loads. Unlike full-scale or simulation specimens, the CCF specimen eliminates geometrically induced stress gradients in the test region. Experimental data on CCF life and strain responses of ZSGH4169 alloy are acquired under different CCF loads. The Maximum Strain within Each(MSE) CCF cycle is demonstrated to be independent of the Low-Cycle Fatigue (LCF) loads and High-Cycle Fatigue (HCF) stress amplitudes, but exhibits a correlation with the Cycle Ratio of HCF/LCF (Rf). The growth law of MSE changes from linear to logarithmic as Rf decreases. Strain amplitudes in the dwell stage, observed unaffected by Rf, are quantified as a function of LCF nominal stresses and HCF stress amplitudes. However, under a defined CCF load, strain amplitudes in the dwell stage remain constant. Strain peaks in the dwell stage in a single CCF cycle decrease in a power function with increasing HCF cycles.

Crack Evolvement of Ancient Brick Masonry Under Uniaxial Compression Fatigue Loading

ABSTRACT Cracking is an essential intuitive indicator of damage in masonry structures. Evaluating the progression of fatigue cracks in ancient brick masonry structures is vital for the preservation and safety of ancient buildings. By conducting amplitude cyclic uniaxial compression tests on ancient brick masonry specimens, using the video image correlate-3d (VIC-3D) technology to collect images of the entire process from loading to failure, the development of fatigue cracks is analyzed and concluded. A reversed S-shaped function for fatigue crack evolution was established based on the fatigue damage mechanism. The model parameters’ physical significance, value range, and their impact on the model curve were discussed. The fatigue damage evolution equation was derived from the fatigue crack evolution model. The research results show that a reversed S-shaped function for fatigue crack evolution covers various types of fatigue crack evolution laws, with strong adaptability and high accuracy. The damage evolution curve established, based on the fatigue crack evolution model, has a reversed S-shaped change rule, and was divided into three stages: the first stage (0 N f ~ 0.1 N f ) fatigue damage grows faster; the second stage (0.1 N f ~ 0.9 N f ) fatigue damage growth is stable, close to linear change; when the cycle ratio exceeds 0.9, it enters the third stage, and fatigue damage increases rapidly.

Application of Artificial Intelligence Technology in Optimizing Control Parameters of Traffic Signal Group Systems

On the basis of introducing the concept of intersection signal state phase difference, the author proposes a proportional signal phase difference design scheme for traffic signal system control, on the basis of the HCM signal delay calculation formula, a standardized signal cycle and effective green signal ratio optimization design model were compiled, thus forming a complete set of optimization design modes for the control parameters of the urban main road traffic signal group system. The experimental results indicate that, the entire simulation experiment took 6000 seconds to compare the traditional fuzzy algorithm with the controller implemented by the author's fuzzy neural network, each case was simulated 5 times, the data in the Table is the average of 5 times, compared with traditional fuzzy algorithms, the author's method shows an improvement of 20.8% to 45.67% in average vehicle delay time, especially when the traffic flow is different in the east-west and north-south directions, the improvement is more significant.

A Zero‐Voltage Switching Three‐Level Nonisolated Bidirectional DC/DC Converter With a Lossless Passive Component Auxiliary Circuit and Design‐Oriented Analysis

ABSTRACTA three‐level bidirectional buck/boost converter (TLBBBC) is suitable for power electronic systems with a high‐voltage DC link for its switches with half voltage. In order to achieve higher efficiency, a novel zero‐voltage switching (ZVS) TLBBBC is proposed in this paper to enable operation with higher switching frequencies. In the proposed ZVS TLBBBC, two identical ZVS cells, each composed of a resonant inductor, two snubber capacitors, and two resonant capacitors, are integrated with the conventional three‐level (TL) topology to enable soft switching in all four switches in both buck and boost modes. Here, one advantage is that soft‐switching conditions are ensured under conventional control methods without using the auxiliary switch or complex control methods. In addition, the soft‐switching region is derived, clearly illustrating the relationship between the duty cycle ratio and the power inductor current that ensures the soft‐switching condition. Hence, the soft‐switching region is beneficial for assisting in ZVS cell design and guiding the converter in running in ZVS. Then, the operation and design considerations of the proposed topology are analyzed in detail. Finally, the experimental results of an 800‐W prototype for both the boost and buck modes are presented to confirm the theoretical analysis.

Effects of Petasitin as Natural Extract on Proliferation and Pathological Changes of Pediatric Neuroblastoma SK-N-SH Cells

This research was developed to investigate the impact and mechanisms of petasitin as natural extract on the proliferation and pathological changes of pediatric neuroblastoma SK-N-SH cells. The sample cells were selected as experimental materials and randomly rolled into a control (Ctrl), a low-dose (LD), a medium-dose (MD), and a high-dose (HD) group, which were subjected to regular culture, 0.5, 1.5, and 5 μM/L petasitin for 12 hours, respectively. Meanwhile, the cell proliferation was evaluated using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Flow cytometry (FCT) was employed to assess the cycle progression and apoptosis of SK-N-SH cells, while Hoechst 33258 fluorescent staining was applied to observe the nuclear changes. Meanwhile, the real-time quantitative PCR (RT-qPCR) was applied to measure the mRNA levels of PI3K, PTEN, AKT1, and mTOR genes in SK-N-SH cells. Western blot was conducted to determine the protein expression levels (PELs) of p-PI3K, PI3K, p-Akt, Akt, p-mTOR, and mTOR in SK-N-SH cells. The results revealed that after treatment for 48 and 72 hours, the optical density (OD) values in the petasitin treatment groups were lower and exhibited great differences to those in the Ctrl group (P < 0.05), while inhibition rates (IRs) were higher (P < 0.05). Furthermore, the petasitin treatment groups exhibited an obvious increase in the G1/G0 cell cycle ratio (CCR) and a great decrease in S and G2/M phase CCR (P < 0.05). Moreover, the apoptotic rates in the petasitin treatment groups were much higher at different time points, showing observable differences with P < 0.05. Besides, the Hoechst 33258 staining positivity rates (PRs) of SK-N-SH cell nuclei in the petasitin treatment groups were higher and presented great differences with P < 0.05 to those in the Ctrl group. In addition, the cells in petasitin treatment groups exhibited greatly downshifted mRNA levels of PI3K and AKT1 and obviously elevated PTEN (all P < 0.05). PELs of PI3K, AKT1, and mTOR exhibited no great differences (P > 0.05), but phosphorylation levels of p-PI3K, p-Akt, and p-mTOR were decreased in the petasitin treatment groups, presenting great differences with P < 0.05. Together, these results suggested that petasitin exerted a suppressive role in proliferation and promote the apoptosis of pediatric SK-N-SH cells by adjusting PI3K-Akt-mTOR signaling pathway (SPW).

Plasma-enhanced atomic layer deposition as a technique for controlling the composition and properties of indium-based transparent conductive oxides

Indium oxide and doped indium oxide films were successfully grown utilizing a plasma-enhanced atomic layer deposition supercycling process, which was found to be an effective means of controlling films’ composition and, hence, their properties. Using trimethylindium and oxygen plasma as an indium precursor and a co-reactant, respectively, a growth rate of approximately 1.26 Å per cycle was obtained based on thickness measurements by spectroscopic ellipsometry. Three distinct dopants, Sn, Ti, and Mo, have been incorporated into indium oxide. The effects of dopant type, cycle ratio of dopant to indium oxide, and thermal annealing on the structural, electrical, and optical properties were studied. The deposited films consisted of polycrystalline columnar grains perpendicular to the substrate with a cubic bixbyite structure and [111] as the favored growth direction. Thermal annealing had a significant effect on the film characteristics, resulting in an order of magnitude reduction in resistivity, as well as changes in transmittance in the near-infrared (NIR) and ultraviolet (UV) regions. The lowest resistivities achieved for Sn-doped, Ti-doped, and Mo-doped were 2.8 × 10−4, 4.2 × 10−4, and 6.1 × 10−4 Ω cm, respectively. The changes are attributed to dopant activation, as the UV shift between the differently doped samples may be linked to the Moss–Burstein effect and the NIR behavior can be explained by an increase in charge carrier density, as predicted by the Drude model. The three dopants primarily provide a trade-off between electrical resistance and NIR transparency. Mo-doped films exhibited the highest near-infrared transparency, while Sn-doped films offered the lowest sheet resistance.

(Invited) Oxide Semiconductor Gain Cell Memory

The energy and delay consumed by the off-chip memory (DRAM) and memory-to-logic chip data movement becomes the bottleneck (known as the memory wall) for the computing systems nowadays, especially for abundant-data computing and neural network accelerators. Larger on-chip memory capacity with high bandwidth can be a solution, yet it is difficult to achieve using SRAM and DRAM. Oxide semiconductor FET (OSFET)-based gain cell memory on the logic platform provides higher density than SRAM due to 3D stacking and is an attractive complement to off-chip DRAM. OSFET with extremely low leakage is used as the write transistor for long retention time, while the read transistor can either adopt OSFET for multiple-layer stacking (OS-OS gain cell) or Si FET for higher read speed (Hybrid gain cell). Designing OSFET gain cell is more than simply choosing materials/device designs that have the lowest off-state leakage current for the longest retention time. Atomic Layer Deposition (ALD) Indium Tin Oxide (ITO) FET is chosen to balance retention time with memory bandwidth. With material, process, and device co-design, the ITO films deposited by ALD with TMIn precursor, 9:1 In:Sn cycle ratio, and 2nm thickness exhibited optimized characteristics for OSFET-based gain cell. The experimentally optimized device exhibits low off-current 2×10-18 A/µm, high on-current 26.8 µA/µm, low SS 70 mV/dec, and high mobility 27 cm2/Vs. It also shows good stability with small VTH shift < 0.2 V under 125 °C, low PBS shift < 0.35 V and low NBS shift < 0.1 V under 1000s bias stress. Oxide semiconductor transistors is an accumulation mode transistor that requires a gate electric field to turn off the transistor. The transistor design calls for nanometer-thin oxide semiconductor channels. Significant device design tradeoffs exists between high on-current, low off-current, short gate length scalability, and the setting of proper threshold voltages. This talk will give an overview of the above experimental achievements today and the device design considerations for future gain cell memories.

Memristive Hodgkin–Huxley Neurons with Diverse Firing Patterns for High‐Order Neuromorphic Computing

The rich firing behaviors of biological neurons enable the nervous system to execute complex computations, emulating which in hardware is advantageous for constructing advanced intelligent machines. Hodgkin–Huxley (H–H) neurons based on memristors feature great merits of high bio‐plausibility and low hardware cost. However, a universal design rule of memristive H–H neurons is still lacking, hindering its development and applications. Herein, a universal H–H neuron circuit structure is proposed and its feasibility based on NbOx memristors is demonstrated. The constructed neuron achieves 23 types of firing behaviors observed in biological neurons, simplifying the communication between neurons. To better understand the correlation between circuit parameters and firing patterns, the firing patterns into three classes according to the switching cycle ratio of two memristors are categorized. The circuit design rules of each category of firing patterns are deeply elucidated and universal regularities for tuning circuit parameters to implement the switch between different firing behaviors are presented. Finally, the potential applications of different firing behaviors in neuromorphic intelligence systems are discussed. This work provides theoretical guidance for engineering memristive H–H neuron circuits, assisting in building high‐order neuromorphic systems based on firing patterns.

Ultrasonic-Assisted Extraction of Phytochemicals Such as L-Tryptophan, Serotonin, and Melatonin from Tomatoes

Large amounts of byproducts are generated by the food processing industries in the 21st century including bioactive compounds such as polysaccharides, polyphenols, carotenoids, and dietary fiber. Due to a lack of sustainable extraction techniques, these processing wastes are regarded as having negligible value in comparison to processed fruit or vegetables. Conventional extraction has limitations in terms of time, energy, and solvent usage. In comparison with conventional methods of extraction, ultrasonic-assisted extraction can extract bioactive components in a short period, at low temperatures, and with less energy and solvent, as well as maintaining the functionality of the components. However, UAE-related variables such as frequency, power, duty cycle, temperature, time, solvent type, and liquid-solid ratio must be understood and optimized for each byproduct. This article provides the mechanism, concept, and factors that influence bioactive compound extraction, with a focus on tomatoes.

Fully atomic layer deposition induced InAlO thin film transistors

The atomic layer deposition (ALD) technique has been extensively utilized for depositing metal oxide (MO) thin films, particularly as gate insulators in thin film transistors (TFTs). However, research on MO semiconductors as channel layer materials in TFTs using ALD is limited, especially for fully ALD-fabricated MO TFTs. In this study, fully ALD-fabricated InAlO TFTs were developed, with optimized aluminum doping content and annealing temperature to enhance the electrical properties and stability. The InAlO TFTs, fabricated with a cycle ratio of 15:1 and annealed at 350 °C, exhibit superior performance, including a field-effect mobility of 7.2 cm2/V·s, a subthreshold swing of 165 mV/decade, and an on/off current ratio of 2.3 × 106, with a threshold voltage of only 0.1 V. Additionally, they demonstrated good stability, with a threshold voltage shift of 0.11 V under positive bias stress. The improved electrical properties and stability are attributed to reduced carrier concentration and the inhibition of oxygen defect generation, achieved through appropriate annealing temperatures and aluminum doping. Thus, the development of fully ALD-fabricated high-performance TFTs holds promise for next-generation display technologies as pixel-driving circuits.

Unlocking the potential of zwitterionic vapor-induced phase separation membranes synthesized from maleic anhydride in polyvinylidene fluoride-based systems for antifouling applications

This work presents an approach to form zwitterionic porous poly(vinylidene fluoride) (PVDF) membranes fabricated by vapor-induced phase separation (VIPS). The reaction between maleic anhydride groups, incorporated initially in the casting solution by blending styrene maleic anhydride (SMA), with 3-((3-aminopropyl)dimethylammonio)propane-1-sulfonate led to the desired zwitterionic moieties. XPS and FTIR analyses confirm the functionalization of the membrane. SEM analyses revealed that it did not have any major impact on the membrane morphology deemed to be close to bicontinuous. While the mean pore size of the virgin membrane was 0.57 μm, it increased to 0.85 μm suggesting the pore-forming effect of SMA during the phase-inversion process. Hydration was significantly enhanced, attributed to the zwitterionic groups on the one hand, but also to the formation of carboxylic acid and amide groups following the ring-opening reaction. It led to significant resistance to bacterial attachment as tested with 4 strains of bacteria including Escherichia coli, Stenotrophomonas maltophilia, Staphylococcus aureus and Streptococcus mutans (>99 % reduction for each). Applied in cyclic water/bacterial solution filtration tests, the modified membrane showed clear improvement in overall performances. Hence, for the virgin membrane, the initial water permeability, flux recovery ratio after the first cycle and flux recovery ratio after the second cycle were found to be 3000 L m−2 h−1.bar−1, 12 % and 53 %, respectively. For the optimized zwitterionic membrane, they were measured to be 7000 L m−2 h−1.bar−1, 26 % and 100 %, respectively. The efficacy of styrene maleic anhydride as a precursor for achieving stable and efficient zwitterionization of PVDF microfiltration membranes is evidenced, rendering it valuable for the filtration of microorganism-containing wastewater. Moreover, its potential application extends to the biomedical realm.

Effect of Business Cycle, Income Diversification, and Financial Ratios on Bank Risk in the ASEAN Region

Research Aims: This research aims to analyze the influence of the business cycle, income diversification, and financial ratios as proxied by profitability and liquidity on the level of banking risk adjustment in ASEAN in the 2020-2022 period. Design/methodology/approach: The research used a sample of 93 banks in the ASEAN region. Sample selection applied purposive sampling techniques based on certain criteria in the Philippines, Indonesia, Malaysia, Singapore, Thailand and Vietnam. The estimation technique used is the Ordinary Least Square method on panel data to analyze the model being built. Research Findings: Research shows that the relationship between the business cycle and bank risk is negative. This means that when the economy is in a contraction phase, bank risk will decrease and vice versa. Then, banks that diversify their income can reduce bank risk. On the other hand, the influence of profitability and liquidity has a negative effect, meaning that a high level of income accompanied by liquid bank assets has the potential to reduce the level of bank risk. Apart from that, there are several other aspects that banks need to pay attention to in anticipating emerging risks, including previous year's credit risk, business size, loan loss reserves, asset growth and financial freedom. Theoretical Contribution/Originality: The originality of the research lies in its comprehensive approach to analyzing the impact of business cycles, income diversification, and financial ratios on bank risk in the ASEAN region. The study's methodology, variables, and empirical evidence all contribute to its originality and relevance to the existing literature Keywords: Revenue Diversification, Liquidity, Profitability, Bank Risk, Business Cycle

Ultrasonic Study of Longitudinal Critically Refracted and Bulk Waves of the Heat-Affected Zone of a Low-Carbon Steel Welded Joint under Fatigue

Currently, ultrasonic methods for assessing the fatigue lifetime of various structural materials are being actively developed. Many steel constructions are made by welding. The weld heat-affected zone is the weak point of the construction, as it is most susceptible to destruction. Therefore, it is actually important to search for acoustic parameters that uniquely characterize the structural damage accumulation in the heat-affected zone of a welded joint in order to predict failure. In this work, the specimens were made from the base metal and the welded joint’s heat-affected zone. The specimens were subjected to uniaxial tension–compression under a symmetrical cycle in the region of low-cycle fatigue with control of the strain amplitude. The propagation bulk velocities of longitudinal, shear waves and subsurface longitudinal critically refracted (LCR) waves during cyclic loading were studied. The acoustic birefringence of shear waves was calculated, and a similar parameter was proposed for longitudinal and LCR waves. The dependence of the elastic modulus ratio on the cycle ratio was obtained. It was shown that the acoustic parameters change most intensively in the heat-affected zone. According to the data of the C33/C55 ratio changes measured through the ultrasonic method, a formula for calculating the remaining fatigue life in the heat-affected zone was proposed.

Experimental Study on Cyclic Simple Shear Test of Coastal Tidal Soft Soil

Based on undrained cyclic simple shear tests conducted on coastal tidal soft soil under various conditions of cyclic stress ratios and moisture contents, this study investigated the influence of these factors on the dynamic properties of the soil. The findings indicated that with increasing moisture content and stress cycle ratio, the stress–strain hysteresis loop gradually expanded, resulting in a higher strain difference and a transition from a dense to a sparse curve pattern. Moreover, the symmetry of the hysteresis loop was lost in the later stages of shearing. With an increase in the number of cycles, the cumulative shear strain gradually increased, and the increase in the cyclic ratio of water content to stress reduced the number of cyclic shear cycles required to achieve failure, thereby accelerating the soil’s failure rate. A predictive formula was developed based on the experimental results to estimate the failure cycles as a function of the cyclic stress ratio and moisture content. Furthermore, the softening index decreased gradually with an increasing number of cycles, and a higher moisture content and cyclic stress ratio accelerated the soil’s softening process. It was observed that under the conditions of optimal moisture content, the soil exhibited a slower softening rate during the initial stage of shearing.