Phase Characteristics Research Articles

Velocity-Based Training With Weightlifting Derivatives: Barbell and System Velocity Comparisons.

Suchomel, TJ, Kissick, CR, Techmanski, BS, Mann, JB, and Comfort, P. Velocity-based training with weightlifting derivatives: Barbell and system velocity comparisons. J Strength Cond Res XX(X): 000-000, 2024-The aim of this study was to examine the differences in barbell and system (i.e., subject + load) velocity during weightlifting derivatives performed across a spectrum of relative loads. 14 resistance-trained men participated in 6 testing sessions, which included 1 repetition maximum hang power clean (HPC) testing and individual jump shrug (JS), hang high pull (HHP), HPC, hang clean pull (HCP), and countermovement shrug (CMS) sessions. The order of the exercise testing sessions was randomized and required the subjects to perform either JS, HHP, HPC, HCP, or CMS repetitions while standing on a force platform with a linear position transducer attached to the barbell. The JS and HHP were performed with 20, 40, 60, 80, and 100% of their 1 repetition maximum HPC, HPC with 20, 40, 60, and 80% 1RM, and the HCP and CMS performed with 20, 40, 60, 80, 100, 120, and 140% 1RM. Mean and peak barbell and system velocities were determined across all exercises and loads using either 2 × 5, 2 × 4, or 2 × 7 repeated measures ANOVA depending on the number of loads performed. Significantly ( p < 0.001) and meaningfully ( g ≥ 1.49) greater mean and peak barbell velocities existed at every exercise and load combination compared with the mean and peak system velocities produced. Barbell and system velocity are distinct characteristics that should not be substituted for one another. Owing to the characteristics of the transition phase, mean barbell and system velocity may not provide strength and conditioning practitioners with meaningful information related to load prescription.

Approximate Solutions of the Boussinesq Equation for Horizontal Unconfined Aquifers During Pure Drainage Phase

In this work, conceptual approximations of the Boussinesq equation were introduced and analyzed, resulting into a very accurate and well-applicable model for horizontal unconfined aquifers during the pure drainage phase, without any recharge and zero-inflow conditions. The model was constructed by employing a variety of methods that included wave solution, variable separation, and series expansion, and its analysis and performance against the Boussinesq equation, at early and later times, providing fruitful insights enlightening the main mechanisms and physical characteristics of the drainage phase. The modeled non-linear forms were finally linearized, concluding with explicit analytical expressions that accurately incorporated most of the basic characteristics regarding the evolution of the water table and the outflow from the exact Boussinesq equation under different initial conditions. The endeavors of this work can be utilized for theoretical and modeling purposes related to this problem.

Influence of bed temperature on the final properties of PLA parts manufactured by material extrusion

Purpose This paper aims to study the influence of bed temperature on the properties of printed parts and their structural stability. Design/methodology/approach Material extrusion is a manufacturing technique in which a part is completed layer by layer with molten filament. The first layer is deposited on a build platform called bed, which is usually at a controlled temperature above room temperature. The density, coefficient of thermal expansion and Young’s modulus were determined as a function of the bed temperature. The complex permittivity was determined at different temperatures, with the aim of analyzing the influence of the bed temperature and isothermal treatments on the characteristics of the amorphous phase. Findings The Young’s modulus presented a non-monotonic behavior, while the coefficient of thermal expansion did not present a clear dependence on the bed temperature. However, a contraction of the dimensions of the parts was observed after heating at temperatures above the glass transition. With treatments at temperatures lower than the glass transition temperature, no changes were observed. However, with treatments at temperatures higher than this, changes in the mobile amorphous region were inferred. Originality/value Issues related to the use of parts manufactured by 3D printing after a posterior heating were analyzed: an improvement in the Young’s modulus and a slight variation of the coefficient of thermal expansion were observed. However, a significant variation in dimensions was detected, mainly for the lowest bed temperatures. This is important for possible applications at temperatures above 60°C.

Improving microvascular sensitivity of color Doppler using phase mask based flow recycling algorithm

&#xD;Blood flow sensitivity is a crucial metric for appraising the effectiveness of color Doppler flow imaging (CDFI). Color Doppler velocity maps based on classic autocorrelation techniques are widely used in clinical practice. However, these techniques often produce twinkling artifacts in noisy regions due to the inherent randomness of noise phases. To mitigate artifacts and improve image quality, Power Mask (PoM) technology becomes imperative. Nevertheless, PoM technology unintentionally filters out small flow signals that have similar power and frequency characteristics to noise signals, thereby reducing the imaging system's sensitivity to flow. &#xD;Approach:&#xD;To address this issue, a novel Flow Recycling Algorithm (FRA) based on phase anomaly is introduced in this study. This algorithm, excavating small flow signals from noise, aims to enhance the small flow signals with low-velocity by the phase characteristics of the color Doppler flow information. &#xD;Main results: &#xD;Experiments in multi-organ imaging have shown that the FRA-CDFI approach is more effective in suppressing twinkling artifacts in noisy regions, preserving intricate small flow signals, and markedly improving small blood flow sensitivity. This novel approach provides adequate technical support for clinical ultrasound imaging of organs with dense small blood vessels, such as the brain, kidneys, liver, and more. &#xD;Significance: &#xD;As a novel post-processing method, FRA-CDFI holds significant potential for future deployment in clinical high-frame-rate ultrasound imaging devices.

Microstructural and Performance Analysis of (TiAl)95−xCu5Nix Coatings Prepared via Laser Surface Cladding on Ti–6Al–4V Substrates

In this study, the surface of (Ti-6Al-4V)TC4 alloy was modified via laser cladding. The elemental composition of the coating was (TiAl)95−xCu5Nix, with Ni as the variable (where x = 0, 3, 6, and 9 at.%). Multi-principal alloy coatings were successfully prepared, and their constituent phases, microstructures, and chemical compositions were thoroughly investigated. The hardness and wear resistance of the coatings were analyzed, and the compositions and interfacial characteristics of the different phases were examined via transmission electron microscopy. The analysis revealed that Ni formed a solid solution and a eutectic structure in the Ti(Al, Cu)2 phase. These findings provide valuable insights into the coating properties. Moreover, reciprocal dry sliding friction experiments were conducted to investigate the wear mechanism. The results revealed a significant increase in wear resistance owing to the formation of a Ni solid solution and changes in the coating structure. Additionally, tensile tests demonstrated that the tensile strength of the coatings initially increased and then decreased with varying Ni content. By combining these results with various analyses, we determined that the coating exhibited optimal properties at a Ni content of 6 at.%. Overall, this study comprehensively investigated the microstructure and phase transition behavior of these coatings through various analytical techniques. These findings provide valuable guidance for further optimizing both the preparation process and the performance of the coatings. The coatings exhibit excellent wear resistance and could inspire the design of more advanced protective surfaces.

Effect of Heating Temperature for Hardening on Structural and Phase Characteristics of Heat-Resistant Steels with 12% Chromium

Effect of Heating Temperature for Hardening on Structural and Phase Characteristics of Heat-Resistant Steels with 12% Chromium

Characterizing the Effects of Concussion and Head Impact Exposure: Design, Methods, and Participant Traits of the CARE 2.0 Study.

This article describes the design, methods, and participant characteristics of the second phase of the Concussion Assessment, Research, and Education (CARE) Consortium study ("CARE 2.0") of the effects of concussion and repetitive head impact exposure on neuropsychiatric health. The authors conducted a prospective multisite observational study of male and female collegiate athletes and military service academy cadets and midshipmen participating in the CARE study. Participants were assessed at three time points: undergraduate baseline (UB), before departure from university or service academy (exit), and up to 6 years following graduation (postgrad) via an online battery of brain health assessments. Participant characteristics were compared across the three time points and four levels of head impact exposure. A total of 4,643 participants completed the exit assessment, and 3,981 completed the postgrad assessment. Relative to the UB assessment cohort, the exit and postgrad assessment cohorts differed with respect to the percentage of women, baseline Wechsler Test of Adult Reading scores, National Collegiate Athletic Association division category, sport contact level, and number of previous concussions. The median standardized difference across balancing variables, assessment time points, and degree of head impact exposure was 0.12 (with 90% of effect sizes ≤0.29). Although there were some statistically significant differences between participants across assessments, the effect sizes were modest, and overall the data suggest that the exit and postgrad cohorts reflect the characteristics of the baseline cohort. The CARE study design and its large, richly characterized sample provide an opportunity to answer important questions about cumulative and persistent effects of concussion and repetitive head impact exposure on neuropsychiatric health.

Multi-Fidelity Aeromechanical Design Framework for High Flow Speed Multistage Axial Compressors

Abstract The development of novel engine architectures is vital in achieving the aviation sector&amp;#x92;s net-zero carbon emission target by 2050. With today&amp;#x92;s digital decade providing support for an accelerated technology maturation, the challenge for turbomachinery design remains to significantly push the limits of current performance within an ambitious development lead time. In this context, it is essential to adopt a design framework where the predictive models or simulations employed target a sufficiently reliable performance assessment. These models must be tailored to the dynamics of evolving industrial design processes, and therefore continuously balance required design flexibility, robust evaluation, appropriate fidelity (i.e. the level of detail and accuracy they provide), and resulting evaluation time. This paper discusses a framework for designing axial compressors and its application to the aeromechanical optimisation of a high-speed compressor rotor. The design environment integrates geometry parametrisation, modular evaluation with different levels of fidelity for the aerodynamic and structural models, and surrogate-based optimisation (SBO) capabilities. It is shown how the combination of a modular sequencing of the different models and the acceleration enabled by high-performance computing (HPC) and machine learning allows for a more advanced preliminary design. A significant gain in isentropic efficiency is attained while satisfying all structural constraints. At the same time, it is demonstrated that the framework is compatible with the characteristics of the preliminary design phase: both in its ability to adapt to cycle and design changes as well as regarding the turnaround time of the optimisation itself.

Spontaneous imbibition of unsaturated sandstone under different vertical temperature gradients: neutron radiography experiments and dynamic models

To elucidate the imbibition behavior of water in complex temperature and stress environments, spontaneous imbibition experiments were conducted on unsaturated matrix sandstones at different vertical temperature gradients by neutron radiography technology. Additionally, corresponding dynamic models of water imbibition in porous media were established. The research results reveal the phased characteristics of sandstone spontaneous imbibition and the influence of vertical temperature gradient on the evolution of wetting front. Specifically, the initial development speed of the wetting front increases with an increase in the vertical temperature gradient, indicating a direct relationship. However, the growth rate of the wetting front gradually slows down with increasing time, eventually reaching a saturated state. Model validation demonstrates that the traditional Washburn's law is still valid in isothermal conditions without temperature gradient (G=0). Further analysis indicates that the imbibition rate has a direct correlation with linear thermal expansion coefficient (α) and viscosity temperature coefficient (β) across various vertical temperature gradients, and an inverse correlation with surface tension temperature coefficient (γ). Furthermore, when the values of α, β, and γ fall below 0.001, their impact on the imbibition rate becomes negligible. The sensitivity of the imbibition rate to parameters γ, β, and α decreases in that order, with γ being the most sensitive, followed by β, and α being the least sensitive. Moreover, the relative importance of α, β, and γ dictates their specific influence on the imbibition rate, and a synergistic effect exists among these parameters, which collectively influence the water absorption behavior of sandstone.

Сравнительное исследование элементов и биохимических компонентов стерильных и фертильных бурых водорослей Ascophyllum nodosum

Brown algae are a valuable renewable bioresource and are also important organisms to monitor due to anthropogenic impacts in the Arctic. In both cases, the content of natural elements and their potential seasonal variations are important knowledge for developing a monitoring program and planning biomass collection. The purpose of this work was a comparative study of the influence of the reproductive phase and biochemical characteristics on the elemental composition of Ascophyllum nodosum from the Barents Sea, the Irminger Sea and the Norwegian Sea. The content of polysaccharides (alginic acid, laminaran, fucoidan and mannitol) and 12 elements was studied. It was shown that the content of Fe, Al, Co, Cu correlates significantly in pairs, regardless of the presence of receptors in algae (r = 0.71–0.95, p &lt; 0.05). It has been shown that the content of alginic acid significantly correlates with Co, Ca, Cu, As, Rb (r = –0.95, –0.89, –0.89, –0.88, –0.81, p ˂ 0.05, respectively) in sterile algae A. nodosum. Also for sterile individuals, a direct correlation of mannitol with Ca, Cu, Co, Rb, Sr, Al, Ba, Fe, Mn was noted (r = 0.98, 0.95, 0.93, 0.92, 0.91, 0.89, 0.82, 0.78, 0.76, р ˂ 0.05, respectively) and polyphenols with Zn (r = 0.94 at р ˂ 0.05) and As (r = 0.85 at р ˂ 0.05). For the first time, a direct correlation between the accumulation of alginic acid and fucoidan has been revealed for A. nodosum from the Arctic seas, which is not associated with the reproductive phase of the algae.

Tunable phase and electrical characteristics induced by Al content in Zr1− xAlxN films for temperature sensors with wide temperature range

Tunable phase and electrical characteristics induced by Al content in Zr1<b>−</b> <i>x</i>Al<i>x</i>N films for temperature sensors with wide temperature range

A two-fluid multiphase flow model coupled with the population balance equations for the flow of a multidispersed particle system

SummaryWe present a two-fluid multiphase flow model that can be applied to the flow of polydisperse particle systems. In the model, the flow of polydisperse particle systems with different N particle sizes is considered only as two phases of fluid and particle phases, without considering the individual N phases, and the motion of particles with different diameters is represented by the motion characteristics of fluid and granular phases. The equations for the granular phase are obtained by averaging the Euler equations for the particles of different particle sizes. And the velocity of particles of different particle sizes is calculated by an explicit approximation, similar to determining the slip velocity in a mixed model of multiphase flow without solving the Eulerian momentum equation. Also, the conservation equation of particles of different particle sizes was obtained by adding the source term to the population balance equation, which is caused by the difference in the particle velocity of the particles with different particle sizes. The proposed method was compared with the results of experimental studies presented in the previous study to verify the validity of the method. The method has the advantage of not only visualizing the particle size fraction distribution but also of being stable in calculation and not increasing the computational effort significantly in studying the flow of polydisperse particle systems with particle size distribution.

B-080 Development and Validation of a GQ1b IgG ELISA as a Diagnostic Aid for Subacute Demyelinating Polyneuropathies

Abstract Background Autoimmunity targeting GQ1b is associated with group of disorders that includes Miller-Fisher Syndrome (MFS), Bickerstaff Brainstem Encephalitis (BBE) and classic Guillain Barre Syndrome (GBS) with ophthalmoplegia. Collectively these are referred to as GQ1B-IgG related syndromes. The prevalence of GQ1b-IgG in this population of patients is high and has been reported to be &amp;gt;80% in well-defined clinical cohorts. Clinical phenotypic presentation is diverse and requires highly accurate antibody testing. The objective of this study was to evaluate a newly developed custom GQ1b-IgG assay, using a semi-quantitative ELISA-based method. Methods A GQ1b-IgG ELISA was developed and validated. Patient sera along with assay controls and a single-point calibrator are diluted and incubated in duplicate wells in a 96-well plate coated with GQ1b antigen. The plate is washed and incubated with anti-human-IgG secondary antibody conjugated with HRP. After a colorimetric reaction, optical densities (OD) are read. The OD of patient samples are compared against the calibrator, generating a cut-off index (COI). Samples ≥1.0 COI are considered positive. During the validation phase, analytical and clinical performance characteristics were evaluated. Studies included assessment of imprecision at multiple concentrations of GQ1b-IgG, accuracy using method comparison, analytical sensitivity and specificity, reference range, common interferences, plate drift, and clinical performance in relevant disease and control cohorts. Results Intra-assay imprecision (coefficient of variation; %CV) ranged from 1.0 - 16% across all concentrations of GQ1b-IgG. Inter-assay imprecision (%CV) ranged from 12.4 - 44.5% but was &amp;lt;20% at or above the assay cut-off. We found perfect qualitative agreement with an independent ELISA reference method (20 positive and 20 negative samples selected based on reference method results [reference interval &amp;lt;1:100]). Limit of detection (LOD) was calculated at a COI of 0.22. To assess analytical specificity, 40 samples with high concentrations of immunoglobulins (hypergammaglobulinemia [N=15], IgG M-protein [N=15] and systemic lupus erythematosus [N=10] were tested and all were negative. A reference interval study was performed on 140 healthy donor serums, all were negative. Interference studies were conducted on 2 positive and 2 negative serum samples, spiked for highly hemolytic (1000 mg/dL), lipemic (2000 mg/dL) and icteric (60 mg/dL) conditions. There was no impact on the assay even with high levels of a given interferent. Plate drift on 2 distinct patient pools tested across the plate (COI range 0.7 - 1.3) had overall plate CV’s ≤10%. ROC analysis was performed on a cohort of 278 patient samples (15 MFS cases and 263 controls [suspected demyelinating neuropathy or disease mimics]). A cut-off value of 1.0 (COI) was selected based on the Youden index. At this cut-off, clinical sensitivity for MFS was 87% while clinical specificity was 99.2%. Conclusions The observed performance of the GQ1b-IgG ELISA was acceptable for clinical laboratory implementation. A COI of ≥ 1.0 was selected for clinical use.

The effect of trace vanadium addition on mechanical properties, microstructure and austenite phase characteristics in a 3.9% Al-Delta TRIP steel

This study aimed to examine the effect of adding 0.12 wt% vanadium on the properties of delta TRIP steel through microstructural and mechanical investigations. The delta ferrite phase was observed in all annealing temperatures and samples. Carrying out bainitic transformation at 350 °C for 6, 10, and 15 min resulted in the stability of the austenite phase and the formation of ferritic bainite phase after heat treatment. The presence of vanadium led to the formation of MC precipitate phases and reduced the remaining austenite percentage from 14% to 6% by weight in the heat-treated sample. The low percentage of austenite in vanadium-containing steel has weakened the TRIP effect in strengthening. On the other hand, the presence of MC precipitates has compensated for the reduction in strength from the TRIP strengthening process through precipitation hardening and reducing the grain size of the delta ferrite phase. The resulting properties (UTS: 866 MPa and El: 41.3%) have led to the creation of a formability index of 35 GPa% in vanadium-containing steel, which is better than the mechanical properties (UTS: 857 MPa and El: 37.4%) and the formability index of vanadium-free steel (32 GPa%). These factors make this steel a suitable option for automotive industry applications. Based on these features make this steel a suitable candidate for automotive industries. Microstructural investigations revealed that the addition of vanadium reduces the grain size of the delta ferrite phase. Typically, the austenite phase forms around the ferritic bainite phase and delta ferrite grain boundaries. During tensile testing, it transforms into martensite through the TRIP process.

An efficient pseudoelastic pure P‐mode wave equation and the implementation of the free surface boundary condition

AbstractBased on the elastic wave equation, a pseudoelastic pure P‐mode wave equation has been recently derived by projecting the wavefield along the wavefront normal direction. This pseudoelastic pure P‐mode wave equation offers an accurate simulation of P‐wave fields with accurate elastic phase and amplitude characteristics. Moreover, considering no S‐waves are involved, it is computationally more efficient than the elastic wave equation, making it an excellent choice as a forward simulation engine for P‐wave exploration. Here, we propose a new pseudoelastic pure P‐mode wave equation and apply the stress image method to it to implement the free surface boundary condition. The new pseudoelastic wave equation offers significantly improved computational efficiency compared to the previous pseudoelastic wave equation. Additionally, the wavefields simulated by this new pseudoelastic wave equation exhibit clear physical interpretations. We evaluate the accuracy of the new wave equation in simulating elastic P‐waves by employing a model with high‐velocity contrasts. We find that this new equation, which purely admits P‐waves, though having exact amplitude and phase behaviour as the elastic waves for transmission components, the amplitudes slightly suffer in the scattering scenario. The difference in amplitude between the elastic and our pseudoelastic increases as the contrast in velocity at the interface (interlayer velocity ratio) increases, especially the S‐wave velocities. This has negative implications on scattering from the free surface boundary condition or the sea bottom interface, especially if the shear wave velocity below the surface or the sea bottom is high. However, in cases where, like for land data in the Middle East, the transition to a free surface is smoother, the accuracy of the pseudoelastic equation is high. In all cases, regardless of the interlayer velocity ratio, the accuracy of the pseudoelastic wave equation in simulating the elastic case, for scattered waves, exceeds that of the acoustic wave equation in phase and amplitude.

Mechanical properties and JC constitutive modification of tungsten alloys under high strain rates and high/low temperatures

The original Johnson-Cook model's poor prediction of W90 alloy stress at high strain rate and high and low temperatures restricts research and utilization of this alloy. This study used a Split Hopkinson Pressure Bar (SHPB) device to conduct dynamic compression tests on W90 alloy over a temperature range of [-90℃,700℃] and analyze its mechanical behavior. We examined the material's different plastic phase characteristics at high and low temperatures and conducted microstructure research on impact test specimens. Then, we analyzed the stress-strain data from SHPB experiments and quasi-static compression tests on the classical Johnson-Cook model. The original Johnson-Cook model was calibrated using the stress-strain data from SHPB and quasi-static compression tests, and the modified Johnson-Cook model was established and verified. The results show that: low temperature significantly strengthens the material's stress, while increasing temperature thermal softening reduces stress; increasing strain rate increases the strain generated by the workpiece, causing faster strain hardening and thermal softening effects, resulting in higher and more stable stress; low temperature makes thicker grain boundaries, increasing plastic stress, and increasing strain rate also increases plastic stress, as well as making the material's grain boundaries thicker. The increase of strain rate makes the grain more dense, which will also show up in the increase of stress on the macroscopic level; the modified Johnson-Cook model in this paper has high agreement with experimental data, with a mean value of MAPE of only 1.85 %,which is 90.20 % lower than the traditional model, and the average value of the RMSE is 85.56 % lower than the traditional model. The modified model significantly outperforms the traditional model in predicting stress and better describes stress changes in W90 at different temperatures.

Numerical Simulation Study on Optimization of Development Parameters of Condensate Gas Reservoirs

Due to the retrograde condensation phenomenon in the development process, the fluid phase change is complex, and it becomes particularly difficult to accurately describe the fluid flow characteristics and residual oil and gas distribution characteristics during the development of condensate gas reservoirs. It is difficult to select the development program and subsequent dynamic adjustment for the efficient, reasonable, and sustainable development of condensate gas reservoirs. In this paper, the phase characteristics of condensate gas reservoirs are clarified; the basic fluid model is created by using computer modeling, using Win-Prop; and in view of the characteristics of the target condensate gas reservoirs, the CMG (Computer Modeling Group) numerical simulation method is applied to study the effects of six factors, the thickness of the reservoir, permeability, porosity, rock compression coefficient, the ratio of the vertical permeability to the horizontal permeability, and the injection of different media, on the development effect through the study of different development parameters of gas condensate reservoirs. The purpose of this study is to provide guidance for the rational development of condensate gas reservoirs in practical production.

A wideband folded reflectarray antenna with a 3-D printed circularly polarized converter

Abstract In this letter, a wideband folded reflectarray antenna with a novel circularly polarized converter is presented. The main reflectarray is composed of dual-polarized units, which can achieve good polarization and phase characteristics with a smaller size. Based on 3-D printing technology, the proposed dielectric unit can be used to design the low-cost linear-to-circular polarization converter (LCPC) with wider bandwidth. In order to validate the performance of the proposed circularly polarized folded reflectarray antenna (CPFRA), a prototype is manufactured and measured. The maximum gain of 25.3 dBic and the maximum aperture efficiency of 38 % are obtained. The measured 3 dB gain bandwidth is 32.7 % and the measured 3 dB AR bandwidth is 31.7 %, respectively. The simulated and measured results show great agreement.

Influence of bedding on fracture toughness and failure patterns of anisotropic shale

The initiation and propagation of hydraulic fractures are closely related to the fracture ability of rocks. Such processes in shale reservoirs are, to a certain extent, controlled by bedding. However, the control mechanism of bedding on the anisotropy of fracture toughness and fracturing behavior remains unclear. In this study, a series of numerical notched semi-circular bend (NSCB) tests are conducted using the discrete element method (DEM) to investigate the influence of bedding properties on the anisotropy of fracture toughness and fracture patterns. Based on the DEM framework, a novel simulation method is proposed to accurately identify two key fracture indicators, the fracture process zone (FPZ) and crack tip opening displacement (CTOD), to reveal the fracture driving mechanism. The results show that the fracture toughness of shale is negatively correlated with bedding angles β but positively correlated with bedding spacing and bedding strength. Both the bedding strength and spacing significantly influence the fracture pattern of the specimens with β = 0°–60°, whereas the specimen with β = 90° is scarcely affected by the bedding planes. The evolution of the CTOD and FPZ in shale exhibits distinct phased characteristics. Due to the strong suppression effect of low-angle bedding planes on pre-peak crack deflection, the CTOD and FPZ exhibit opposite trends with respect to bedding angles before and after the peak load. This study facilitates the understanding of the fracture propagation process of anisotropic shale and could provide guidance for hydraulic fracturing design in shale reservoirs.

Exploring W-EUROFER brazed joints: S/TEM and nanoindentation analysis following post-brazing tempering treatment

Tempering treatments are essential for restoring the hardness and microstructure of EUROFER steel when W-EUROFER joints are formed at temperatures exceeding the steel's austenitization point (890 °C). This post-brazing heat treatment can, however, alter the microstructure and thereby affect the mechanical properties. This study explores the microstructural and nanomechanical effects in the brazed area of W-EUROFER joints following this heat treatment, utilizing copper as an intermediate filler material. Using Scanning Transmission Electron Microscopy (STEM) with Energy Dispersive Spectroscopy (EDS) on FIB lamellae and nanoindentation techniques we examined the stability and phase characteristics of the post-tempered microstructure in two lamellae that covers the whole phases of the braze microstructure.The tempering process enhances copper diffusion and the growth of copper precipitates without significantly altering the joint's overall microstructure. Despite the general stress-relief effects of tempering, which typically lower mechanical properties, the diffusion phases formed during brazing maintained high hardness and modulus, indicative of a complex, element-rich composition. A reduction in mechanical properties was observed in the iron-rich phase near the W-braze interface and the EUROFER base material, aligning with the purpose of the heat treatment. However, the copper braze and tungsten base material largely retained their stability and resilience to thermal treatments.This research provides vital insights into the behavior of these material systems under thermal processing, highlighting the necessity of optimizing heat treatment parameters to preserve joint integrity in high-performance applications such as nuclear fusion reactors. The findings contribute significantly to the development of durable and reliable materials for fusion energy, emphasizing the importance of controlled tempering processes to enhance material properties.