Time-dependent Characteristics Research Articles

Evaluation of thermal radiation and Lewis number effects on oscillatory thermal-diffusive instabilities of counterflow premixed flame fed with moisty biomass particles

In this study, a thermal-diffusive model using a sinusoidal function for the oscillation term is presented. The model is employed to evaluate the pulsating behavior in a premixed counterflow flame fed with biomass particle cloud considering Lewis number and thermal radiation effects. In order to scrutinize the pulsating characteristics of a flame, time-related governing equations are written for the assumed multi-zone system and analytically solved utilizing Matlab and Mathematica software. To enforce continuity, suitable matching conditions for the temperature and heat flux at the interfaces are derived. Time-dependent characteristics of burning velocity, flame temperature, flame front position, reactants temperature, and mass distributions are presented, taking into account effective Lewis number, thermal radiation, and strain rate influences. An acceptable comparison with numerical simulations affirms the reliability of the mathematical procedure. The obtained results indicated that the pulsating instability of biomass-fueled premixed flames in counterflow arrangements significantly relevant not only to the effective Lewis number but also to thermal radiation transferred from the reaction zone to unburnt reactants. Furthermore, it is found that in counterflow premixed flames, strain rate, in addition to Lewis number and thermal radiation, can be the key to controlling the individual flame oscillation modes.

Investigation on failure mechanism and time-delay fracturing behavior of hard-rock tunnel under extremely high geostress state

To investigate the failure mechanism and time-delay fracturing behavior of hard-rock tunnel under extremely high geostress state, a series of conventional triaxial compression tests and time-delay loading–unloading mechanical tests on rocks were conducted. Combining testing results and on-site data of deep-buried tunnels, the generation mechanism and failure process of time-delay rockbursts were analyzed. The results indicate that with the increase of confining pressure, the failure mode of hard-rock exhibits a transition from axial splitting type and shear-slip type to special squeezing-expansion type. The progressive damage of rocks under extremely high stress state mainly manifests as aging lateral and volumetric expansion. Under time-delay compression tests, the long-term strength of hard-rock is lower than the threshold stress of σeb. In extremely high stress state, the fracture and dissipated energy evolution of rocks has significant time-dependent characteristics. Under extremely high stress conditions, rocks can store a large amount of releasable energy internally and gradually generate numerous cracks without the need for external work, ultimately leading to sudden unstable failure. Affected by the superposition of time-delay pressure and loading–unloading effects, the hard-rock also exhibits the same time-dependent fracturing behavior as soft-rock under high stress state, but its deformation mechanism is dominated by lateral expansion and crack volumetric dilatancy. When the stress level is far from reaching the ultimate strength required for rockmass failure, it is sufficient to cause the propagation of internal microcracks. Under the action of time-delay loads, the spalling and peeling failure of surrounding rock is significantly reduced, but the scale of unstable blocks is larger. Based on the failure process and microseismic monitoring date of rockburst in hard-rock tunnels, the entire evolution process of time-delay rockbursts can be divided into the following six stages: before excavation, rockmss excavation, aging cracking, squeezing-expansion, instability and spalling, time-delay rockburst. Time-delay rockburst has an obvious acoustic emission calm period before its occurrence, making its incubation process has strong suddenness and randomness.

Effect of Sampling Frequency on a Unilateral Isometric Hamstring Strength Assessment Using Force Plates

AbstractThe purpose of this study was to determine the effect of sampling frequency on the 90–90° (90-degrees hip and knee flexion) isometric hamstring assessment. Thirty-three elite female soccer players (age: 18.7 ± 3.7 years; height: 158.3 ± 5.9 cm; body mass: 62.8 ± 5.5 kg) performed three unilateral trials on a single occasion of the 90–90° isometric hamstring assessment. Force-time data were collected using force plates at 1000 Hz and down sampled to 500-, 250-, and 100 Hz. Peak force (N), force (N) at 100- and 200 ms and average rate of force development (aRFD) (N/s) over a 100- and 200 ms epoch were calculated. A repeated measures of analysis of variance and effect size was used to compare means. Excellent absolute and good relative reliability was observed for peak force across all sampling frequencies. Force at 100- and 200 ms and aRFD over 100 ms and 200 ms resulted poor-moderate relative reliability and poor-excellent absolute reliability. No significant trivial differences were observed for peak force between sampling frequencies (P > 0.05, Cohen’s d = 0.02–0.12). A significant difference (P < 0.001) was identified in 500, 250 and 100 Hz, with small-moderate and small-large increases in force at set time points and aRFD, respectively, in comparison to 1000 Hz (d = 0.21–2.00). Higher sampling frequencies (> 500 Hz) reduces the reliability of time dependent force characteristics, with minimal effect on peak force. Regular monitoring of peak force can be performed with higher sampling frequencies, but lower sampling frequencies would be beneficial to collect reliable rapid-force generating measures.

High-Performance Solar-Blind Photodetector Based on (010)-Plane β-Ga2O3 Thermally Oxidized from Nonpolar (110)-Plane GaN.

A high-performance planar structure metal-semiconductor-metal-type solar-blind photodetector (SBPD) was fabricated on the basis of (010)-plane β-Ga2O3 thermally oxidized from nonpolar (110)-plane GaN. A full width at half maximum of 0.486° was achieved for the X-ray rocking curve associated with (020)-plane β-Ga2O3, which is better than most reported results for the heteroepitaxially grown (-201)-plane β-Ga2O3. As a result of the relatively high crystalline quality, a dark current as low as 6.30 × 10-12 A was achieved at 5 V, while the photocurrent reached 1.86 × 10-5 A under 254 nm illumination at 600 μW/cm2. As a result, the photo-to-dark current ratio, specific detectivity, responsivity, and external quantum efficiency were calculated to be 2.95 × 106, 2.39 × 1012 Jones, 3.72 A/W, and 1815%, respectively. Moreover, the SBPD showed excellent repeatability and stability in the time-dependent photoresponse characteristics with fast relaxation time constants for the rise and decay processes of only 0.238 and 0.062 s, respectively. This study provides a promising approach to fabricate the device-level (010)-plane β-Ga2O3 film and a new way for the epitaxial growth of (010)-plane β-Ga2O3 and (110)-plane GaN as mutual substrates.

A hybrid fault diagnosis method for rolling bearings based on GGRU-1DCNN with AdaBN algorithm under multiple load conditions

The fault diagnosis of rolling bearings is a critical aspect of rotating machinery, as it significantly contributes to the overall operational safety of the mechanical equipment. In the practical engineering environment, the complex and variable working conditions, along with the presence of overlapping noise, contribute to intricate frequency information in the acquired signals and their highly time-dependent characteristics, which makes it difficult to extract the available fault features hidden in the signal. Based on this, a hybrid fault diagnosis method named GGRU-1DCNN-AdaBN is introduced, which combines improved gap-gated recurrent unit network (GGRU), one-dimensional convolutional neural network (1DCNN), and adaptive batch normalization (AdaBN). The proposed approach involves several parts to enhance fault diagnosis accuracy in vibration signals under constant load conditions and variable load conditions. Firstly, the end-layer structure of the traditional GRU is replaced with a one-dimensional global average pooling layer to aggregate the influence components of defects and reduce model training parameters. Secondly, the fusion of different types of frequency and sequence features is achieved by combining 1DCNN, addressing the limitation of a single network’s feature extraction capability and the loss of temporal features in a cascaded hybrid model. Subsequently, the fused features are input into a softmax multi-classifier to obtain fault type identification results. Lastly, the GGRU-1DCNN method is further improved by incorporating the AdaBN algorithm, enhancing the model’s domain adaptive capability under variable load conditions and noisy environments. The method is validated using datasets obtained from Case Western Reserve University, aero-engine bearings, Xi’an Jiaotong University, and the Changxing Sumyoung Technology. The findings suggest that the proposed method demonstrates superior accuracy and robustness in fault diagnosis, as well as excellent generalization capability and universal applicability.

Simulation of liquid cone formation on the tip apex of indium field emission electric propulsion thrusters

Field emission electric propulsion (FEEP) thrusters possess excellent characteristics, such as high specific impulse, low power requirements, compact size and precise pointing capabilities, making them ideal propulsion devices for micro-nano satellites. However, the detection of certain aspects, such as the evolution process of the liquid cone and the physical quantities at the cone apex, proves challenging due to the minute size of the needle tip and the vacuum environment in which they operate. Consequently, this paper introduces a computational fluid dynamics (CFD) model to gain insight into the formation process of the liquid cone on the tip apex of indium FEEP. The CFD model is based on electrohydrodynamic (EHD) equations and the volume of fluid (VOF) method. The entire cone formation process can be divided into three stages, and the time-dependent characteristics of the physical quantities at the cone apex are investigated. The influences of film thickness, apex radius size and applied voltage are compared. The results indicate a gradual increase in the values of electrostatic stress and surface tension stress at the cone apex over an initial period, followed by a rapid escalation within a short duration. Apex configurations featuring a small radius, thick film and high voltage exhibit a propensity for liquid cone formation, and the cone growth time decreases as the film thickness increases. Moreover, some unstable behavior is observed during the cone formation process.

Validation and comparison of prognostic scoring systems in patients with head and neck squamous cell carcinoma treated with nivolumab.

Several scoring systems have been developed to predict prognosis in patients with refractory cancer. We aimed to validate eight scoring systems and determine the best method for predicting the prognosis of head and neck squamous cell carcinoma treated with nivolumab. This multicentre retrospective study involved 154 patients with recurrent and/or metastatic head and neck squamous cell carcinoma treated with nivolumab between 2017 and 2020. Oncological outcomes were assessed according to the scoring systems, including MD Anderson Cancer Center + neutrophil-to-lymphocyte ratio and Hammersmith scores. Objective response, overall survival and progression-free survival were evaluated using logistic regression and Cox proportional hazards analyses. Receiver operating curve analysis was used to calculate the area under the curve and estimate the efficacy of each score. No significant associations were found between the responses and any score. Seven of the eight scoring systems were associated with disease control (odds ratio, 0.26-0.70). Amongst the eight scoring systems, MD Anderson Cancer Center + neutrophil-to-lymphocyte ratio showed the highest area under the curve for predicting response and disease control. Seven scoring systems were prognostic factors for progression-free survival (hazard ratio, 1.22-1.95). All eight scoring systems were prognostic factors for overall survival (hazard ratio, 1.62-3.83). According to the time-dependent receiver operating characteristics analysis for overall survival, the Hammersmith scoring system had the best predictive ability at 3months, and the MD Anderson Cancer Center + neutrophil-to-lymphocyte ratio scoring system had the highest area under the curve between 6 and 24months. MD Anderson Cancer Center + neutrophil-to-lymphocyte ratio and Hammersmith scoring systems were better predictors of prognosis in patients with head and neck squamous cell carcinoma treated with nivolumab.

New insights into early-stage time-dependent dielectric characteristics coupled with frequency dependency and hydration-driven reaction of hydraulic cement pastes: Experiments and statistical modelling

In the field of cement and concrete materials engineering, a comprehensive understanding of dielectric properties is crucial for optimising hydraulic cement paste mix designs. This study examines the relationships among the dielectric constant (ε’), loss tangent (tan δ), frequency, hydration time, water content and admixture dosage in different compositions of hydraulic cement paste. A consistent pattern can be observed across the frequency spectrum, where dielectric constants decrease as frequency increases. This aligns with the expected behaviour of cementitious materials. The most notable finding is the inversely proportional relationship between the loss tangent and frequency. As the frequency increases, the loss tangent consistently decreases, indicating improved energy retention and reduced dissipation. This characteristic is of significant value for various applications, including sustainable infrastructure and smart materials. Furthermore, the interactions among hydration time, water content and admixture dosage present an opportunity for dynamic optimisation within the cement paste matrix. These factors collectively impact dielectric properties, providing insights into the potential for tailored material performance and durability, especially in applications where dielectric properties are critical, such as sensing applications and structural health monitoring of concrete structures. This study emphasises the importance of customising cementitious compositions for specific applications in cement and concrete materials engineering. It achieves this through a detailed comparative analysis of different compositions, each representing varying water content and admixture dosage levels. This approach has the potential to significantly transform the field by enabling engineers to create hydraulic cement pastes with customised dielectric properties that meet the specific requirements of construction, infrastructure and other related applications.

Lung microdialysis and in vivo PK/PD integration of cefquinome against Actinobacillus pleuropneumoniae in a porcine experimental lung infection model.

This study aim to explore the application of microdialysis in pharmacokinetic (PK) and pharmacodynamic (PD) integration of cefquinome against Actinobacillus pleuropneumoniae in a porcine experimental lung infection model. The model was established via intratracheal inoculation where average bacterial counts (CFU) in the lungs of infected pigs reached 6.57 log10 CFU/g after 3 h. The PK profiles of unbound cefquinome in lung dialysates were determined following intramuscular injection of single doses of 0.125, 0.25, 0.5, 1, 2, and 4 mg/kg. Lung dialysate samples were collected using microdialysis at a flow rate of 1.5 μL/min until 24 h. The PD studies were conducted over 24 h based on 10 intermittent dosing regimens and total daily doses ranged from 0.25 to 4 mg/kg and dosage intervals included 12 and 24 h. The lung tissue was collected after 24 h of treatment and homogenized for bacterial counts. The relationships between PK/PD parameters derived from lung dialysates and drug efficacy were analyzed using an inhibitory sigmoid Emax model. The percentage of time the free drug concentration exceeded the minimum inhibitory concentration (%fT > MIC) was the PK/PD index best describing the antimicrobial activity (R2 = 0.96) in the porcine experimental infection model. The %fT > MIC values required to achieve net bacterial stasis, 1, 2 and 3 log10 CFU/g reductions in the lung were 22.45, 28.86, 37.62, and 56.46%, respectively. Cefquinome exhibited time-dependent characteristics against A. pleuropneumoniae in vivo. These results provide valuable insights into the application of microdialysis in PK/PD integration model studies and optima regimen of cefquinome for the treatment of porcine respiratory diseases caused by A. pleuropneumoniae.

Development and validation of a novel model to predict recurrence-free survival and melanoma-specific survival after sentinel lymph node biopsy in patients with melanoma: an international, retrospective, multicentre analysis

The introduction of adjuvant systemic treatment for patients with high-risk melanomas necessitates accurate staging of disease. However, inconsistencies in outcomes exist between disease stages as defined by the American Joint Committee on Cancer (8th edition). We aimed to develop a tool to predict patient-specific outcomes in people with melanoma rather than grouping patients according to disease stage. Patients older than 13 years with confirmed primary melanoma who underwent sentinel lymph node biopsy (SLNB) between Oct 29, 1997, and Nov 11, 2013, at four European melanoma centres (based in Berlin, Germany; Amsterdam and Rotterdam, the Netherlands; and Warsaw, Poland) were included in the development cohort. Potential predictors of recurrence-free and melanoma-specific survival assessed were sex, age, presence of ulceration, primary tumour location, histological subtype, Breslow thickness, sentinel node status, number of sentinel nodes removed, maximum diameter of the largest sentinel node metastasis, and Dewar classification. A prognostic model and nomogram were developed to predict 5-year recurrence-free survival on a continuous scale in patients with stage pT1b or higher melanomas. This model was also calibrated to predict melanoma-specific survival. Model performance was assessed by discrimination (area under the time-dependent receiver operating characteristics curve [AUC]) and calibration. External validation was done in a cohort of patients with primary melanomas who underwent SLNB between Jan 30, 1997, and Dec 12, 2013, at the Melanoma Institute Australia (Sydney, NSW, Australia). The development cohort consisted of 4071 patients, of whom 2075 (51%) were female and 1996 (49%) were male. 889 (22%) had sentinel node-positive disease and 3182 (78%) had sentinel node-negative disease. The validation cohort comprised 4822 patients, of whom 1965 (41%) were female and 2857 (59%) were male. 891 (18%) had sentinel node-positive disease and 3931 (82%) had sentinel node-negative disease. Median follow-up was 4·8 years (IQR 2·3-7·8) in the development cohort and 5·0 years (2·2-8·9) in the validation cohort. In the development cohort, 5-year recurrence-free survival was 73·5% (95% CI 72·0-75·1) and 5-year melanoma-specific survival was 86·5% (85·3-87·8). In the validation cohort, the corresponding estimates were 66·1% (64·6-67·7) and 83·3% (82·0-84·6), respectively. The final model contained six prognostic factors: sentinel node status, Breslow thickness, presence of ulceration, age at SLNB, primary tumour location, and maximum diameter of the largest sentinel node metastasis. In the development cohort, for the model's prediction of recurrence-free survival, the AUC was 0·80 (95% CI 0·78-0·81); for prediction of melanoma-specific survival, the AUC was 0·81 (0·79-0·84). External validation showed good calibration for both outcomes, with AUCs of 0·73 (0·71-0·75) and 0·76 (0·74-0·78), respectively. Our prediction model and nomogram accurately predicted patient-specific risk probabilities for 5-year recurrence-free and melanoma-specific survival. These tools could have important implications for clinical decision making when considering adjuvant treatments in patients with high-risk melanomas. Erasmus Medical Centre Cancer Institute.

Comparative analysis of four nutritional scores in predicting adverse outcomes in biopsy-confirmed diabetic kidney Disease.

Malnutrition is associated with adverse outcomes in patients with diabetic kidney disease (DKD). However, it is uncertain which nutritional assessment tools are most effective in predicting the adverse outcomes of DKD. This retrospective study was conducted at a single center and included 367 patients diagnosed with DKD based on biopsy results between August 2009 and December 2018. Four nutritional assessment indices, namely the Prognostic Nutritional Index (PNI), Geriatric Nutritional Risk Index (GNRI), Triglycerides (TG) × Total Cholesterol (TC) × Body Weight (BW) Index (TCBI), and Controlling Nutritional Status (CONUT) score, were selected and calculated. We aimed to assess the association between these nutritional scores and adverse outcomes, including progression to end-stage kidney disease (ESKD), cardiovascular diseases events (CVD), and all-cause mortality. Univariate and multivariate Cox regression analyses, Kaplan-Meier analysis, along with Restricted cubic spline analysis were used to examine the relationship between nutritional scores and adverse outcomes. Furthermore, the area under the curve (AUC) was calculated using time-dependent receiver operating characteristics to determine the predictive value of the four nutritional scores alone and some combinations. Lastly, ordered logistic regression analysis was conducted to explore the correlation between the four nutritional scores and different renal histologic changes. The incidence of ESKD, CVD, and all-cause mortality was significantly higher in patients with DKD who had a lower PNI, lower GNRI, and higher CONUT score. Additionally, The TCBI performed the worst in terms of grading and risk assessment. The PNI offer the highest predictive value for adverse outcomes and a stronger correlation with renal histologic changes compared to other nutritional scores. Patients diagnosed with DKD who have a worse nutritional status are more likely to experience higher rates of adverse outcomes. The PNI might offer more valuable predictive values and a stronger correlation with different renal histologic changes compared to other nutritional scores.

Development of acidochromic colloidal polymer nanoparticles containing azobenzene derivatives as eco-friendly time-dependent anticounterfeiting inks

N,N-dihydroxyethyl azobenzene compounds with different functional groups of hydrogen, electron-donating hydroxyl (OH), and electron-withdrawing nitro (NO2) were synthesized by a two-step diazotization and coupling method. Colloidal poly(methyl methacrylate) (PMMA) nanoparticles, prepared by emulsifier-free emulsion polymerization, were doped with 3 wt% of the three azobenzenes to prepare acidochromic colloids. Acidochromic properties of all the azobenzenes and the polymer colloids were investigated in acidic buffers. Azobenzene compounds doped on polymer particles showed different colors in buffers with different pH values due to the presence of different functional groups, which makes them highly applicable as acid detectors. The electron-withdrawing NO2 functional group caused a small bathochromic shift in the azobenzene spectrum, and the azobenzene containing OH functional group showed higher bathochromic shift than the unsubstituted azobenzene. The colloidal PMMA nanoparticles doped with the three azobenzene compounds were used as eco-friendly inks for stamping and hand-signing on cellulosic papers. Exposure to acidic HCl vapor resulted in different coloration of the printed marks due to the protonation of the azobenzenes. These colors of the protonated forms were decayed with time and also after exposure to triethylamine vapor. The stamped patterns showed a high fatigue and no change in color intensity up to 20 cycles. This shows that these polymeric inks can be used as anticounterfeiting inks for security-marking of confidential documents and banknotes. The developed inks showed time-dependent characteristics and responsivity to acid and base vapors, which make them highly applicable in security marking of confidential documents and also detection of acid and base.

Study on creep characteristics of granite of deep tunnel affected by joint orientation

Joints are an important part of rock masses and the spatial relationship between joint orientation and in situ stress (or tunnel axis) has a significant impact on the deformation, strength, and failure behavior of the surrounding rock. To study the influence of joint orientation on creep characteristics of deep hard rock, the true triaxial creep tests were performed in the laboratory on natural jointed granite under different loading angles ω (defined as the angle between the strike of the joint plane and σ2-direction) conditions. The test results show that ω has a significant effect on the time-dependent deformation and failure characteristics of the jointed rock. As ω increases, there is a decrease in creep deformation, steady creep rate in the σ3-direction, and value of the DI index (used to evaluate the difference in the time-dependent deformation in the σ2- and σ3-directions). Stress-structure-controlled failure (sliding along the joint plane) occurs when ω ≤ 30°. However, when ω > 30°, the failure of the jointed granite is not affected by joint and stress-controlled failure occurs. The stress-structure-controlled time-dependent failure evolution enters a stage that is dominated by shear cracks earlier than stress-controlled failure according to AE results. In addition, the time-dependent failure went through stages of microcracks initiation and interaction, stable crack growth and unstable crack propagation. And when the time-dependent failure evolution enters the unstable crack propagation stage, the nature of the cracks changed from tensile-dominated to shear-dominated.

Enhancing ground source heat pump system design optimization: A stochastic model incorporating transient geological factors and decision variables

In this study, a cost minimization model of a ground source heat pump (GSHP) was performed to obtain its best design configurations based on system reliability. To implement a high-fidelity optimization, the uncertainties of decision parameters and geological parameters' distributions were considered. The GSHP's lifespan costs were functionalized based on an analytical borehole heat transfer model. Multiple constraints were established to serve as reliability goals to ensure a turbulent ground pipe flow without extreme temperature variations. The ground thermal conductivity, groundwater velocity, and unit price of electricity were considered as three random variables. Their dynamic characteristics were incorporated by assigning different increasing rates to the average magnitudes of them. Additionally, their transient fluctuations were accommodated by integrating probabilistic uncertainties into the optimization process, all of which followed normal distributions. The results demonstrated that the time-dependent characteristics of these uncertain variables could significantly affect the system investment of GSHP by reducing the total costs by 20.7% and 21.1% when the increasing rates of groundwater velocity and ground thermal conductivity reach 5% and 4% respectively. The study also provided optimized design variables under an 85% confidence level in various predicted scenarios, considering a wide range of dynamic geological parameters and energy costs.

Glassy-like Transients in Semiconductor Nanomaterials.

Glassy behavior is manifested by three time-dependent characteristics of a dynamic physical property. Such behaviors have been found in the electrical conductivity transients of various disordered systems, but the mechanisms that yield the glassy behavior are still under intensive debate. The focus of the present work is on the effect of the quantum confinement (QC) and the Coulomb blockade (CB) effects on the experimentally observed glassy-like behavior in semiconductor nanomaterials. Correspondingly, we studied the transient electrical currents in semiconductor systems that contain CdSe or Si nanosize crystallites, as a function of that size and the ambient temperature. In particular, in contrast to the more commonly studied post-excitation behavior in electronic glassy systems, we have also examined the current transients during the excitation. This has enabled us to show that the glassy behavior is a result of the nanosize nature of the studied systems and thus to conclude that the observed characteristics are sensitive to the above effects. Following this and the temperature dependence of the transients, we derived a more detailed macroscopic and microscopic understanding of the corresponding transport mechanisms and their glassy manifestations. We concluded that the observed electrical transients must be explained not only by the commonly suggested principle of the minimization of energy upon the approach to equilibrium, as in the mechanical (say, viscose) glass, but also by the principle of minimal energy dissipation by the electrical current which determines the percolation network of the electrical conductivity. We further suggest that the deep reason for the glassy-like behavior that is observed in the electrical transients of the nanomaterials studied is the close similarity between the localization range of electrons due to the Coulomb blockade and the caging range of the uncharged atomic-size particles in the classical mechanical glass. These considerations are expected to be useful for the understanding and planning of semiconductor nanodevices such as corresponding quantum dot memories and quantum well MOSFETs.

Study on time-varying characteristics and flow behavior of microencapsulated polymer

Due to the challenges posed by high injection pressure and significant viscosity shear loss, conventional polymer flooding methods are unable to effectively meet the urgent demand for enhanced oil recovery in medium- and low-permeability reservoirs. Microencapsulated polymer flooding is a promising solution to address the aforementioned challenges due to its advantages of easy wellbore injection, shear resistance, and delayed thickening. However, there is a lack of research on the release behavior and time-dependent characteristics of microencapsulated polymer and its impact on flow behavior in reservoirs. To address this gap, we conducted a series of experiments, including thermal stability tests, microfluidic chip experiments, and micro-scale oil displacement experiments, to reveal the time-varying behavior generated by the triggered release of microencapsulated polymers. The results showed that microencapsulated polymer can be fully triggered after 8 days of aging at 85 °C, with a viscosity exceeding the initial viscosity by more than 25 times. The release mechanism of the polymer aligned with the Ritger-Peppas model, transitioning from super Case-II transport to anomalous transport, and finally to Fickian diffusion with increasing temperature. During the triggering process, the presence of particles stabilized shear and improved oil displacement, particularly in small pore throats. Higher triggering degrees of the solution resulted in greater flow resistance within the microchannel, effectively suppressing fluid fingering. The oil displacement effectiveness of fully triggered microencapsulated polymer was comparable to that of conventional polymers. This study provides insights into the flow behavior of microencapsulated polymer at a microscopic level, offering valuable references for its application in the field.

Time-dependent fatigue reliability analysis of heavy-haul railway steel bridges

Fatigue of heavy-haul railway bridges has been an ongoing concern due to the excessive stresses and frequent cyclic effects of freight trains. Current fracture-based fatigue research, which promotes fatigue reliability analysis caused by crack propagation, is challenged by the dilemma between the detailed modeling of cyclic stress and the reflection of temporal characteristics of loading conditions. In addition, due to the strong non-Gaussian nature of the fatigue limit state function and the computational inefficiency of integrating finite element analysis, current time-dependent reliability methods need to be further developed. To evaluate the fatigue reliability of heavy-haul railway steel bridges considering the temporal dependence of cyclic train loading, a time-dependent fatigue reliability methodology is developed in this study with two innovations. Firstly, a cyclic stress range model is proposed based on the load analysis at the bridge level, which can capture the time-dependent characteristics of the incurred stress range throughout service life. Then, an improved outcrossing rate method for strong non-Gaussian fatigue limit state functions is developed to reduce the computational costs associated with reliability analysis integrated with the finite element model. The developed time-dependent fatigue reliability methodology is then applied to a heavy-haul railway steel truss bridge located in Shandong, China, which proves its efficiency and accuracy in evaluating the time-dependent fatigue reliability of heavy-haul railway steel bridges. Furthermore, the developed methodology is able to provide insight into the balance between bridge fatigue damage and freight volume, and it is found that the combination of small train axle weight and high operation frequency is the optimal solution to achieve the fatigue reliability of the steel bridge while fulfilling the freight demand.

Impact of osteoporosis and Cement-Augmented fusion on adjacent spinal levels Post-Fusion Surgery: Patient-Specific finite element analysis

Cement-augmentation is a technique commonly used during posterior lumbar instrumented fusion (PLIF) to reinforce compromised osteoporotic vertebral bone, minimize the risk of loosening screws, enhance stability, and improve overall surgical outcomes. In this study, we introduce a novel segmented vertebral body regional modeling approach to investigate the effects of osteoporosis and cement-augmented lumbar fusion on disc biomechanics at spinal levels adjacent to the fused vertebrae. Using our previously validated personalized-poroelastic-osteoligamentous FE model of the spine, fusion was simulated at L4-L5, and the biomechanics of adjacent levels were studied for 30 patients (non-osteoporotic patients (N = 15), osteoporotic patients (N = 15)). PLIF models, with and without cement-augmentation, were developed and compared after an 8 h-rest period (200 N), following a 16 h-cyclic compressive loading of 500–1000 N (40 and 20 min, respectively). Movement in different directions (flexion/ extension/ lateral bending/ axial rotation) was simulated using 10Nm moment before and after cyclic loading. The material mapping algorithm was validated by comparing the results of voxel-based and parametric models. The FE cement-augmented models, subject to daily activity loading, demonstrated significant differences in disc height loss and fluid loss as compared to non-cemented models. The calculated axial stress and fiber strain values were also significantly higher for these models. This work demonstrates that although osteoporosis does not significantly alter the time-dependent characteristics of adjacent IVDs post-surgery, cement-augmentation increases the risk of adjacent segment disease (ASD) incidence. A holistic understanding of the trade-offs and long-term complex interplay between structural reinforcement modalities, including cement augmentation, and altered biomechanics warrants further investigation.

Concurrent process and feedrate scheduling with convoluted basis functions and its application to fluid jet polishing

Non-traditional laser and fluid jet processes exhibit time-dependent material removal characteristics. The feedrate profile must be planned carefully along the toolpath for accurate surface profile generation while ensuring that the kinematic limits of machine tools are not violated. Conventional methods iteratively solve a deconvolution/convolution problem on the dwell-time density (reciprocal of the feedrate profile) that is computationally heavy, may leave significant residual processing errors, and even generate infeasible feed profiles with the manufacturing equipment. This paper proposes a novel approach that fully addresses the shortcomings above. Dwell-time density is first expressed as a continuous B-spline profile. The associated dwell basis functions (DBF) are convolved with the process influence function (PIF) to generate new process basis functions (PBF). This approach conveniently allows the posing of the problem as a concurrent linear least-squares problem on the control points shared by the DBFs and PBFs while ensuring the numerical stability of the solution and smoothness of the feed profile. To mitigate excessive acceleration peaks and any ringing effect around the edges of the toolpath, this paper also presents methodologies for stabilizing the scheduled feedrate profile by introducing knot vector adjustments (adaptive knot dropping) and linear edge constraints. The effectiveness of the proposed method is demonstrated and validated through simulation case studies and experimentally in fluid jet processing of precision optics. Results indicate that the proposed technique overcomes the limitations of conventional strategies and allows high-frequency surface components beyond the first zero-power frequency of the process footprint to be tracked while still generating a smooth feed profile within the acceleration limits of a machine tool. This ability stems from the localization characteristics associated with the basis functions. By improving the accuracy of high-frequency components, the proposed method exhibits the potential to fabricate topographies with sharper edges, which has been a challenge for conventional techniques.

Time-dependent behavior of RC slab-column connections under high sustained loads

Reinforced concrete (RC) flat-plate slab-column connections may be exposed to high sustained stresses under gravity loads far exceeding the typical service-level stresses due to design errors, construction defects, or material deterioration. If the connections fail, then collapse of the structure could occur. Plain concrete can fail when exposed to sustained compressive stress in excess of 75% of its short-term strength. However, very little research has been conducted on the time-dependent strength and stiffness characteristics of RC slab-column connections under high sustained loads. This paper presents the experimental results of eleven aged slab-column connections under sustained concentric and eccentric gravity loading. The specimens were constructed at a 0.47-scale and had slab tensile reinforcement ratios of 0.64% and 1.0% without using shear reinforcement. Three specimens were loaded to failure in a short time, while eight specimens were tested for periods of approximately 45 days under high sustained loads (83% to 98% of their peak capacity). Test results showed that high sustained loads may lead to an eventual failure; however, the level of sustained load needs to be very close (∼95%) to the short-term capacity. Under the sustained loads, the deflection of specimens increased by 18% to 39% of the initial deflections. The deflection and steel strain creep rate approximately followed a logarithmic function, but there was a greater increase in deflection than steel strain. A sharp increase in deflection due to tertiary creep occurred only 2 to 3 min before failure, leaving little warning of the impending failure.