Shield tunneling in saturated ground poses challenges due to the potential risk of ground collapse resulting from seepage force and inadequate support pressure.This study employed a laboratory model test and a theoret...Shield tunneling in saturated ground poses challenges due to the potential risk of ground collapse resulting from seepage force and inadequate support pressure.This study employed a laboratory model test and a theoretical validation to elucidate the mechanisms of face failure and subsequent ground collapse in saturated ground during slurry pressure-balanced shield(SPBS)tunneling operations.A slurry circulation system was developed to ensure steady shield tunneling and to replicate the phenomena of ground collapse.Investigations into shield tunneling parameters and ground responses,including soil pressure,pore water pressure,and surface subsidence,were conducted to understand the mechanisms of face failure and subsequent ground collapse.The theoretical solution for the critical collapse pressure of the tunnel face,based on the rotational failure mechanism,was validated through the comparison with the experimentally determined critical collapse pressure.The results indicate that:(1)appropriate adjustments of tunneling parameters are crucial for promoting filtercake formation,maintaining chamber pressure,and minimizing ground subsidence;(2)chamber pressure,soil pressure,pore water pressure,and ground subsidence are closely correlated with shield tunneling parameters and the formation of filter cake;(3)ground collapse follows a continuous failure mode due to the destruction of filtercake and the decrease in chamber pressure;(4)the soil pressure at the cutterhead is more sensitive to disturbances from shield tunneling than chamber pressure;and(5)experimentally determined critical collapse pressures is consistent with the theoretical solution of limit analysis.展开更多
This study examines how native pore structures and loading conditions influencethe fracture size distribution and the predictability of catastrophic failure in rocks.Four lithologies with distinct pore characteristics...This study examines how native pore structures and loading conditions influencethe fracture size distribution and the predictability of catastrophic failure in rocks.Four lithologies with distinct pore characteristics,i.e.granite,limestone,red sandstone,and marble,were tested under uniaxial compression and Brazilian splitting.Nuclear magnetic resonance(NMR)was used to characterize pore structures,while acoustic emission(AE)monitoring captured the temporal evolution of microcracking.The relationships among pore properties,AE b-values,and failure predictability were systematically evaluated.Results show that the overall b-value is primarily controlled by native pore size rather than loading condition.Rocks with larger pores display higher b-value and greater temporal variability,whereas those with smaller pores exhibit lower and more stable b-value.To assess failure predictability,the AE count rate was incorporated into an inverse power law model.The model demonstrates higher predictive accuracy for high-porosity rocks.The average predicted failure time(t_(p))decreases monotonically with porosity:under uniaxial compression,t_(p)for granite,marble,limestone,and sandstone are 2.32,1.82,1.42,and 0.03,respectively;under Brazilian splitting,3.54,3.30,0.10,and 0.03.Among the four rock types,sandstone with the highest porosity exhibits the smallest discrepancy between predicted and actual failure time,whereas granite with the lowest porosity shows the largest.As porosity decreases,prediction accuracy progressively declines for limestone and marble.Overall,the findings indicate that native pore heterogeneity governs both fracture scaling behavior and failure predictability,and that these effects are largely independent of the loading conditions examined in this study.展开更多
In the past few decades,the navigation performance of ships and structures in ice-covered waters has not been fully studied,especially the influence of ice mechanical properties on icebreaking ability.Ice bending stre...In the past few decades,the navigation performance of ships and structures in ice-covered waters has not been fully studied,especially the influence of ice mechanical properties on icebreaking ability.Ice bending strength is a key ice parameter for predicting ship ice loads,and accurate ice bending strength is also the key to scaling model tests results to real ship.However,numerical simulation studies on model ice bending strength of ice tanks are often neglected.In this paper,an explicit finite element method model is used to simulate the ice cantilever beam test,and the failure load and bending strength of the ice are obtained.In this model,the Tsai-Wu failure criterion is used as the material constitutive model,and the required simulation parameters are obtained from the model ice test in ice tank.Parameter sensitivity analysis shows that the cantilever beam size of the model ice has a significant effect on the flexural strength.The results show that proper rounding at the root of the cantilever beam is beneficial to reduce stress concentration and obtain more accurate bending strength;the thickness,width and length of the cantilever beam should conform to a certain ratio,and consistent with the ITTC recommended reference.Therefore,the results of this study can promote model ice experiments and numerical studies and provide ice strength data support for ship design and polar ship maneuvering.展开更多
Modeling HIV/AIDS progression is critical for understanding disease dynamics and improving patient care. This study compares the Exponential and Weibull survival models, focusing on their ability to capture state-spec...Modeling HIV/AIDS progression is critical for understanding disease dynamics and improving patient care. This study compares the Exponential and Weibull survival models, focusing on their ability to capture state-specific failure rates in HIV/AIDS progression. While the Exponential model offers simplicity with a constant hazard rate, it often fails to accommodate the complexities of dynamic disease progression. In contrast, the Weibull model provides flexibility by allowing hazard rates to vary over time. Both models are evaluated within the frameworks of the Cox Proportional Hazards (Cox PH) and Accelerated Failure Time (AFT) models, incorporating critical covariates such as age, gender, CD4 count, and ART status. Statistical evaluation metrics, including Akaike Information Criterion (AIC), Bayesian Information Criterion (BIC), log-likelihood, and Pseudo-R2, were employed to assess model performance across diverse patient subgroups. Results indicate that the Weibull model consistently outperforms the Exponential model in dynamic scenarios, such as younger patients and those with co-infections, while maintaining robustness in stable contexts. This study highlights the trade-off between flexibility and simplicity in survival modeling, advocating for tailored model selection to balance interpretability and predictive accuracy. These findings provide valuable insights for optimizing HIV/AIDS management strategies and advancing survival analysis methodologies.展开更多
High-altitude cold regions exhibit complex geological and environmental conditions,fostering steep rock slopes with macroscopic joints and mesoscopic freeze-thaw(F-T)damage.Cyclic loading further exacerbates rock inst...High-altitude cold regions exhibit complex geological and environmental conditions,fostering steep rock slopes with macroscopic joints and mesoscopic freeze-thaw(F-T)damage.Cyclic loading further exacerbates rock instability,yet the fracture mechanisms and load response relationships remain poorly understood.This study prepared intact and fractured sandstone specimens,subjected them to F-T cycles and graded loading-unloading,and monitored their structural evolution via X-ray computed tomography.First,the progressive failure process was investigated from both qualitative morphologic features and quantitative void parameters.The results showed that intact and fractured sandstone instability behaviors are determined by F-T damage and joint arrangement,respectively.However,both indicate that precursory localization of failure can only be detected when heterogeneous damage exists in advance.Furthermore,the void parameters of undamaged intact sandstone exhibit power-law acceleration,while damaged sandstones are characterized by a trend of initial decrease followed by an increase.Subsequently,a damage constitutive model for freeze-thawed fractured sandstone under graded loading-unloading was established.This model is based on the Lemaitre strain equivalence hypothesis and defines the coupled damage variable through multivariable indicators.In this framework,the material damage induced by fractures and F-T is unified and characterized by void parameters;while the load-induced damage is integrated with the energy linear allocation law and defined by damage energy.Thus,the stress-strain theoretical relationship is depicted,and the model is validated as reliable.Finally,a conceptual model of rock damage due to F-T and loading-unloading was proposed by combining the microscopic testing results from X-ray diffraction and scanning electron microscopy.展开更多
Assessing the stability of slopes is one of the crucial tasks of geotechnical engineering for assessing and managing risks related to natural hazards,directly affecting safety and sustainable development.This study pr...Assessing the stability of slopes is one of the crucial tasks of geotechnical engineering for assessing and managing risks related to natural hazards,directly affecting safety and sustainable development.This study primarily focuses on developing robust and practical hybrid models to predict the slope stability status of circular failure mode.For this purpose,three robust models were developed using a database including 627 case histories of slope stability status.The models were developed using the random forest(RF),support vector machine(SVM),and extreme gradient boosting(XGB)techniques,employing 5-fold cross validation approach.To enhance the performance of models,this study employs Bayesian optimizer(BO)to fine-tuning their hyperparameters.The results indicate that the performance order of the three developed models is RF-BO>SVM-BO>XGB-BO.Furthermore,comparing the developed models with previous models,it was found that the RF-BO model can effectively determine the slope stability status with outstanding performance.This implies that the RF-BO model could serve as a dependable tool for project managers,assisting in the evaluation of slope stability during both the design and operational phases of projects,despite the inherent challenges in this domain.The results regarding the importance of influencing parameters indicate that cohesion,friction angle,and slope height exert the most significant impact on slope stability status.This suggests that concentrating on these parameters and employing the RF-BO model can effectively mitigate the severity of geohazards in the short-term and contribute to the attainment of long-term sustainable development objectives.展开更多
Embedding optical fiber sensors into composite materials offers the advantage of real-time structural monitoring.However,there is an order-of-magnitude difference in diameter between optical fibers and reinforcing fib...Embedding optical fiber sensors into composite materials offers the advantage of real-time structural monitoring.However,there is an order-of-magnitude difference in diameter between optical fibers and reinforcing fibers,and the detailed mechanism of how embedded optical fibers affect the micromechanical behavior and damage failure processes within composite materials remains unclear.This paper presents a micromechanical simulation analysis of composite materials embedded with optical fibers.By constructing representative volume elements(RVEs)with randomly distributed reinforcing fibers,the optical fiber,the matrix,and the interface phase,the micromechanical behavior and damage evolution under transverse tensile and compressive loads are explored.The study finds that the presence of embedded optical fibers significantly influences the initiation and propagation of microscopic damage within the composites.Under transverse tension,the fiber-matrix interface cracks first,followed by plastic cracking in the matrix surrounding the fibers,forming micro-cracks.Eventually,these cracks connect with the debonded areas at the fiber-matrix interface to form a dominant crack that spans the entire model.Under transverse compression,plastic cracking first occurs in the resin surrounding the optical fibers,connecting with the interface debonding areas between the optical fibers and the matrix to form two parallel shear bands.Additionally,it is observed that the strength of the interface between the optical fiber and the matrix critically affects the simulation results.The simulated damage morphologies align closely with those observed using scanning electron microscopy(SEM).These findings offer theoretical insights that can inform the design and fabrication of smart composite materials with embedded optical fiber sensors for advanced structural health monitoring.展开更多
Electric vehicles,powered by electricity stored in a battery pack,are developing rapidly due to the rapid development of energy storage and the related motor systems being environmentally friendly.However,thermal runa...Electric vehicles,powered by electricity stored in a battery pack,are developing rapidly due to the rapid development of energy storage and the related motor systems being environmentally friendly.However,thermal runaway is the key scientific problem in battery safety research,which can cause fire and even lead to battery explosion under impact loading.In this work,a detailed computational model simulating the mechanical deformation and predicting the short-circuit onset of the 18,650 cylindrical battery is established.The detailed computational model,including the anode,cathode,separator,winding,and battery casing,is then developed under the indentation condition.The failure criteria are subsequently established based on the force–displacement curve and the separator failure.Two methods for improving the anti-short circuit ability are proposed.Results show the three causes of the short circuit and the failure sequence of components and reveal the reason why the fire is more serious under dynamic loading than under quasi-static loading.展开更多
Cemented tailings backfill(CTB)is a crucial support material for ensuring the long-term stability of underground goafs.A comprehensive understanding of its compressive mechanical behavior is essential for improving en...Cemented tailings backfill(CTB)is a crucial support material for ensuring the long-term stability of underground goafs.A comprehensive understanding of its compressive mechanical behavior is essential for improving engineering safety.Although extensive studies have been conducted on the uniaxial compressive properties of CTB,damage constitutive models that effectively capture its damage evolution process remain underdeveloped,and its failure mechanisms are not yet fully clarified.To address these gaps,this study conducted systematic uniaxial compression tests on CTB specimens prepared with varying cement-tailings ratios.The results revealed distinct compaction and softening phases in the stress−strain curves.A lower cement-tailings ratio significantly reduced the strength and deformation resistance of CTB,along with a decrease in elastic energy accumulation at peak stress and dissipation energy in the post peak stage.Based on these findings,a modified damage constitutive model was developed by introducing a correction factor,enabling accurate simulation of the entire uniaxial compression process of CTB with different cement-tailings ratios.Comparative analysis with classical constitutive models validated the proposed model’s accuracy and applicability in describing the compressive behavior of CTB.Furthermore,particle size distribution and acoustic emission tests were employed to investigate the influence of cement-tailings ratio on failure mechanisms.The results indicated that a lower cement-tailings ratio leads to coarser particle sizes,which intensify shear-related acoustic emission signals and ultimately result in more pronounced macroscopic shear failure.This study provides theoretical support and practical guidance for the optimal design of CTB mix ratios.展开更多
Background1 Currently,there is a scarcity of risk prediction models for frailty in hospitalized patients with chronic heart failure(CHF).This study aimed to investigate the frailty status of hospitalized CHF patients,...Background1 Currently,there is a scarcity of risk prediction models for frailty in hospitalized patients with chronic heart failure(CHF).This study aimed to investigate the frailty status of hospitalized CHF patients,identify independent risk factors significantly associated with frailty,and construct an effective risk prediction model.The goal was to provide a reference for clinical strategies in preventing and managing frailty among CHF patients.Methodss Using convenience sampling,we enrolled 184 hospitalized CHF patients from a tertiary hospital between February 2022 and December 2024.General demographic data were collected via questionnaires,alongside frailty screening using the FRAIL scale and assessment of daily functioning with the Activities of Daily Living(ADL)scale.Clinical data were obtained by reviewing medical records.Participants were categorized into a frail group(n=65)and a non-frail group(n=119)based on frailty status.Clinical risk factors were compared between groups.Multivariate logistic regression was used to identify independent risk factors.A prediction model was constructed,and a receiver operating characteristic(ROC)curve was plotted to evaluate its predictive value.Results A total of 184 hospitalized CHF patients were included,with 65(35.33%)exhibiting frailty.Multivariate logistic regression analysis showed that independent risk factors for frailty included:age,ADL score,N-terminal pro-brain natriuretic peptide(NT-pro-BNP),left ventricular ejection fraction(LVEF),New York Heart Association(NYHA)class II/IV,≥3 comorbidities,comorbid diabetes mellitus(DM),comorbid valvular heart disease(VHD),smoking history,hemoglobin(Hb),albumin,high-density lipoprotein cholesterol(HDL-C),low-density lipoprotein cholesterol(LDL-C),creatinine(Cr),and blood urea nitrogen(BUN).The aforementioned factors were incorporated into logistic regression analysis and the prediction model was built.The prediction model showed quite strong predictive performance.Its area under the ROC curve was 0.904(95%CI:0.857-0.951),with a sensitivity of98.5%and a specificity of 85.7%.ConclusionssThe frailty risk prediction model for hospitalized CHF patients demonstrated robust discriminative ability and calibration.It provided substantial reference value for clinical management of CHF,offering a basis for early assessment,risk stratification,and targeted interventions to prevent frailty by identifying high-risk patients.展开更多
Localized rock failures,like cracks or shear bands,demand specific attention in modeling for solids and structures.This is due to the uncertainty of conventional continuum-based mechanical models when localized inelas...Localized rock failures,like cracks or shear bands,demand specific attention in modeling for solids and structures.This is due to the uncertainty of conventional continuum-based mechanical models when localized inelastic deformation has emerged.In such scenarios,as macroscopic inelastic reactions are primarily influenced by deformation and microstructural alterations within the localized area,internal variables that signify these microstructural changes should be established within this zone.Thus,localized deformation characteristics of rocks are studied here by the preset angle shear experiment.A method based on shear displacement and shear stress differences is proposed to identify the compaction,yielding,and residual points for enhancing the model's effectiveness and minimizing subjective influences.Next,a mechanical model for the localized shear band is depicted as an elasto-plastic model outlining the stress-displacement relation across both sides of the shear band.Incorporating damage theory and an elasto-plastic model,a proposed damage model is introduced to replicate shear stressdisplacement responses and localized damage evolution in intact rocks experiencing shear failure.Subsequently,a novel nonlinear mathematical model based on modified logistic growth theory is proposed for depicting the shear band's damage evolution pattern.Thereafter,an innovative damage model is proposed to effectively encompass diverse rock material behaviors,including elasticity,plasticity,and softening behaviors.Ultimately,the effects of the preset angles,temperature,normal stresses and the residual shear strength are carefully discussed.This discovery enhances rock research in the proposed damage model,particularly regarding shear failure mode.展开更多
BACKGROUND:Acute kidney injury(AKI)is a severe and fatal complication of acute heart failure(AHF).Existing studies on AKI following AHF in the Chinese population have scarce insights available from the emergency depar...BACKGROUND:Acute kidney injury(AKI)is a severe and fatal complication of acute heart failure(AHF).Existing studies on AKI following AHF in the Chinese population have scarce insights available from the emergency department(ED).This study aimed to investigate the predictive factors of patients with AHF complicated with AKI in a Chinese ED cohort,and to establish a risk prediction model.METHODS:Hospitalized patients diagnosed with AHF in the ED from December 2016 to September 2023 were included.The overall dataset were divided into the training set and the testing set at a 7:3 ratio.Univariate and multivariate logistic regression analyses were performed to identify the risk factors for AKI in patients with AHF in the training set,leading to the development of a risk prediction model.The performance of the model was further assessed.RESULTS:A total of 789 patients with AHF were enrolled,with an AKI incidence of 29.7%.The mortality rates of the AKI and non-AKI groups were 23.1%and 7.6%,respectively.Logistic regression analysis showed that the levels of white blood cell(OR=2.368;95%CI:1.502-3.733,P<0.001),albumin(OR=2.669;95%CI:1.601-4.451,P<0.001),serum creatinine(OR=3.221;95%CI:1.935-5.363,P<0.001),and hemoglobin(OR=2.009;95%CI:1.259-3.205,P=0.003),maximum 24-h furosemide dosage(OR=2.196;95%CI:1.346-3.582,P=0.002),the use of non-invasive ventilation(OR=2.419;95%CI:1.454-4.024,P=0.001),and diabetes mellitus(OR=3.192;95%CI:2.014-5.059,P<0.001)were independent risk factors for AKI after AHF.These factors were subsequently incorporated into a risk prediction model.The area under the receiver operating characteristic(AUROC)curve for the predictive model was 0.815(95%CI:0.776-0.854)and 0.802(95%CI:0.776-0.854)in the training set and the testing set,respectively.CONCLUSION:This risk prediction model might assist physician to predict AKI following AHF effectively in the emergency setting.展开更多
BACKGROUND Partial hepatectomy continues to be the primary treatment approach for liver tumors,and post-hepatectomy liver failure(PHLF)remains the most critical lifethreatening complication following surgery.AIM To co...BACKGROUND Partial hepatectomy continues to be the primary treatment approach for liver tumors,and post-hepatectomy liver failure(PHLF)remains the most critical lifethreatening complication following surgery.AIM To comprehensively review the PHLF prognostic models developed in recent years and objectively assess the risk of bias in these models.METHODS This review followed the Checklist for Critical Appraisal and Data Extraction for Systematic Reviews of Prediction Modelling Studies and the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guideline.Three databases were searched from November 2019 to December 2022,and references as well as cited literature in all included studies were manually screened in March 2023.Based on the defined inclusion criteria,articles on PHLF prognostic models were selected,and data from all included articles were extracted by two independent reviewers.The PROBAST was used to evaluate the quality of each included article.RESULTS A total of thirty-four studies met the eligibility criteria and were included in the analysis.Nearly all of the models(32/34,94.1%)were developed and validated exclusively using private data sources.Predictive variables were categorized into five distinct types,with the majority of studies(32/34,94.1%)utilizing multiple types of data.The area under the curve for the training models included ranged from 0.697 to 0.956.Analytical issues resulted in a high risk of bias across all studies included.CONCLUSION The validation performance of the existing models was substantially lower compared to the development models.All included studies were evaluated as having a high risk of bias,primarily due to issues within the analytical domain.The progression of modeling technology,particularly in artificial intelligence modeling,necessitates the use of suitable quality assessment tools.展开更多
Dear Editor,Heart failure(HF)is a common multi-faceted and life-threatening syndrome,of which up to 23%occur acute kidney injury(AKI)[1].HF-related AKI is largely overlooked or delayed in identification[2].Approximate...Dear Editor,Heart failure(HF)is a common multi-faceted and life-threatening syndrome,of which up to 23%occur acute kidney injury(AKI)[1].HF-related AKI is largely overlooked or delayed in identification[2].Approximately 85%of AKI cases that occurred during cardiac hospitalization in China were either ignored or identifi ed too late[3].Currently,there are no specific guidelines for the management of HF-related AKI.Hence,it is essential to identify patients at the risk of developing AKI and intervene promptly.展开更多
Ceramic matrix composites have broad application prospects in the aerospace field due to their high temperature resistance and oxidation resistance.The effect of temperature and environment atmosphere on the fracture ...Ceramic matrix composites have broad application prospects in the aerospace field due to their high temperature resistance and oxidation resistance.The effect of temperature and environment atmosphere on the fracture toughness and failure mechanisms of two-dimensional plain-woven SiC_(f)/SiC composites was investigated.The results show that they exhibit pseudo-plastic deformation behavior at different temperatures.The fracture toughness is as high as 48 MPa m^(1/2)at room temperature,and gradually decreases with rising temperature.The difference in fracture toughness between argon and air initially increases and then decreases with rising temperature.Furthermore,the high-temperature failure mechanisms of these composites were analyzed through macro and micro analysis.Based on this,a physic-based temperature-dependent fracture toughness model considering matrix toughness,plastic power,fiber pull-out,and residual thermal stress was developed for fiber-reinforced ceramic matrix composites.The model has been well validated by experimental results.An analysis of influencing factors regarding the evolution of fracture toughness was conducted by the proposed model.This work contributes to a better understanding of the mechanical performance evolution and failure mechanisms of ceramic matrix composites under multifield coupling conditions,thereby promoting their applications.展开更多
This research extends ongoing efforts to develop methods for reinforcing damaged main gas pipelines to prevent catastrophic failure.This study establishes the use of scaled-down experimental models for assessing the d...This research extends ongoing efforts to develop methods for reinforcing damaged main gas pipelines to prevent catastrophic failure.This study establishes the use of scaled-down experimental models for assessing the dynamic strength of damaged pipeline sections reinforced with wire wrapping or composite sleeves.A generalized dynamic model is introduced for numerical simulation to evaluate the effectiveness of reinforcement techniques.The model incorporates the elastoplastic behavior of pipe and wire materials,the influence of temperature on mechanical properties,the contact interaction between the pipe and the reinforcement components(including pretensioning),and local material failure under transient internal pressure.Based on these parameters,a finite element model was developed using ANSYS 19.2 to enable parametric studies.The accuracy of the proposed model was verified by comparing the simulation results with the experimental findings.Pipeline section samples containing non-penetrating longitudinal crackswere subjected to comparative analyses and transient pressure until critical failure.The unreinforced and steel wire-wrapped sections were investigated.The results confirm the feasibility of applying the computational model to study the dynamic strength of reinforced damaged pipe sections.Furthermore,pipelines with longitudinal cracks reinforced using circular composite overlays with orthotropic mechanical properties were examined,and recommendations are provided for selecting the geometric parameters of such overlays.展开更多
In this editorial,we comment on the article by Teerasarntipan et al published in a recent issue of the World Journal of Gastroenterology.Dengue infection is a major mosquito-borne disease with global significance.Deng...In this editorial,we comment on the article by Teerasarntipan et al published in a recent issue of the World Journal of Gastroenterology.Dengue infection is a major mosquito-borne disease with global significance.Dengue-induced severe hepatitis(DISH)is a rare complication though severe,as it can lead to acute liver failure(ALF)with an incidence rate between 0.7%and 2.0%and mortality rates from 47.0%to 58.8%.In this context,the identification of patients at risk of ALF could improve prognosis in DISH patients.Teerasarntipan et al retrospectively enrolled 2532 dengue patients,counting 193 DISH and 20 ALF.The authors explored the prognostic role of liver-specific scores,as the model for end-stage liver disease(MELD)score,albumin-bilirubin(ALBI)score,easy(EZ)-ALBI score,and platelet-ALBI(PALBI)score.Univariate analysis identified international normalized ratio(INR),total bilirubin,albumin,and creatinine as independent laboratory factors associated with ALF,while age,gender,and liver comorbidities were not linked to in-hospital mortality.The presence of dengue shock syndrome significantly increased mortality,with an odds ratio(OR)of 28.05(95%CI:7.21-109.18,P<0.001).High INR and low albumin were laboratory markers associated with death from DISH,with ORs of 5.83(95%CI:2.59-13.12,P<0.001)and 0.15(95%CI:0.05-0.44,P<0.001),respectively.Multivariate analysis confirmed that INR remained the only significant predictor of both ALF and death,with adjusted ORs of 19.54(95%CI:3.37-113.38,P<0.001)and 3.86(95%CI:1.13-13.18,P=0.031),respectively.Among prognostic models,the MELD score performed best in predicting ALF,with a very high accuracy[area under the receiver operating characteristic curve(AUROC)of 0.929,87.5%sensitivity,89.3%specificity at a cutoff of 16],followed by the EZ-ALBI,ALBI,and PALBI scores,with AUROCs of 0.865,0.832,and 0.797,respectively.As MELD remains the best scoring system for predicting poor outcomes in DISH-related ALF,EZ-ALBI is a valid adjunct tool that could improve medical care in these patients.展开更多
In 2018,a catastrophic high-altitude landslide occurred at Baige,located within the tectonic suture zone of the Upper Jinsha River.The failure mechanism of this event remains poorly understood.This study aims to eluci...In 2018,a catastrophic high-altitude landslide occurred at Baige,located within the tectonic suture zone of the Upper Jinsha River.The failure mechanism of this event remains poorly understood.This study aims to elucidate the deformation characteristics and failure mechanism of the Baige landslide by employing a comprehensive methodology,including field geological surveys,analysis of historical remote sensing imagery,high-density electrical resistivity surveys,and advanced displacement monitoring.Additionally,the physical modeling experiments were conducted to replicate the unique failure modes.The findings propose a novel perspective on the failure mechanism of the Baige landslide,which involves two critical stages:first,the brittle shear zone bypasses and fails at the lower locked segment,and second,the failure of the upper locked segment,combined with the shear zone's impact on the lower locked segment,triggers overall slope instability.Physical modeling experiments revealed a transition from initial acceleration to a rapid acceleration phase,particularly marked by a significant increase in velocity following the failure of the upper locked segment.The intensity of acoustic emission signals was found to correlate with the failure of the locked segments and the state of particle collisions post-failure.It offers new insights into the failure mechanisms of tectonic mélange belt large-scale landslides in suture zones,contributing to the broader field of landslide research.展开更多
Objective:To explore the effect of implementing a time-sensitive incentive model combined with specialized rehabilitation nursing in patients with severe pneumonia and respiratory failure.Methods:Seventy-eight patient...Objective:To explore the effect of implementing a time-sensitive incentive model combined with specialized rehabilitation nursing in patients with severe pneumonia and respiratory failure.Methods:Seventy-eight patients with severe pneumonia and respiratory failure admitted from January 2024 to February 2025 were selected and randomly divided into two groups using a computer-based random drawing method.The control group(39 patients)received routine nursing,while the observation group(39 patients)received a time-sensitive incentive model combined with specialized rehabilitation nursing.Lung function and adverse emotional states were compared between the two groups.Results:After 2 weeks of nursing,the lung function of the observation group was higher than that of the control group(P<0.05),and the adverse emotional states of the observation group were lower than those of the control group(P<0.05).Conclusion:Implementing a time-sensitive incentive model combined with specialized rehabilitation nursing in patients with severe pneumonia and respiratory failure can improve lung function and emotional state.展开更多
Four different types of three-body model composed of rock and coal with different strength and stiffness were established in order to study the failure characteristics of compound model such as roof-coal-floor. Throug...Four different types of three-body model composed of rock and coal with different strength and stiffness were established in order to study the failure characteristics of compound model such as roof-coal-floor. Through stress analysis of the element with variable strength and stiffness extracted from the strong-weak interface, the tri-axial compressive strength of the weak body and strong body near the interface as well as the areas away from the contact surface was found. Then, on the basis of three-dimensional fast Lagrangian method of continua and strain softening constitutive model composed of Coulomb-Mohr shear failure with tensile cut-off, stress and strain relationship of the four three-body combined models were analyzed under different confining pressures by numerical simulation. Finally, the different features of local shear zones and plastic failure areas of the four different models and their development trend with increasing confining pressure were discussed. The results show that additional stresses are derived due to the lateral deformation constraints near the strong-weak interface area, which results in the strength increasing in weak body and strength decreasing in strong body. The weakly consolidated soft rock and coal cementation exhibit significant strain softening behavior and bear compound tension-shear failure under uni-axial compression. With the increase of confining pressure, the tensile failure disappears from the model, and the failure type of composed model changes to local shear failure with different number of shearing bands and plastic failure zones. This work shows important guiding significance for the mechanism study of seismic, rock burst, and coal bump.展开更多
基金support of the National Natural Science Foundation of China(Grant Nos.52179116 and 51991392)the support of Key Deployment Projects of Chinese Academy of Sciences(Grant No.ZDRW-ZS-2021-3).
文摘Shield tunneling in saturated ground poses challenges due to the potential risk of ground collapse resulting from seepage force and inadequate support pressure.This study employed a laboratory model test and a theoretical validation to elucidate the mechanisms of face failure and subsequent ground collapse in saturated ground during slurry pressure-balanced shield(SPBS)tunneling operations.A slurry circulation system was developed to ensure steady shield tunneling and to replicate the phenomena of ground collapse.Investigations into shield tunneling parameters and ground responses,including soil pressure,pore water pressure,and surface subsidence,were conducted to understand the mechanisms of face failure and subsequent ground collapse.The theoretical solution for the critical collapse pressure of the tunnel face,based on the rotational failure mechanism,was validated through the comparison with the experimentally determined critical collapse pressure.The results indicate that:(1)appropriate adjustments of tunneling parameters are crucial for promoting filtercake formation,maintaining chamber pressure,and minimizing ground subsidence;(2)chamber pressure,soil pressure,pore water pressure,and ground subsidence are closely correlated with shield tunneling parameters and the formation of filter cake;(3)ground collapse follows a continuous failure mode due to the destruction of filtercake and the decrease in chamber pressure;(4)the soil pressure at the cutterhead is more sensitive to disturbances from shield tunneling than chamber pressure;and(5)experimentally determined critical collapse pressures is consistent with the theoretical solution of limit analysis.
基金supported by the National Natural Science Foundation of China(Grant No.42172316)the Major National Science and Technology Project for Deep Earth(Grant No.2024ZD100380X)the Natural Science Foundation of Hunan Province of China(2025JJ20030).
文摘This study examines how native pore structures and loading conditions influencethe fracture size distribution and the predictability of catastrophic failure in rocks.Four lithologies with distinct pore characteristics,i.e.granite,limestone,red sandstone,and marble,were tested under uniaxial compression and Brazilian splitting.Nuclear magnetic resonance(NMR)was used to characterize pore structures,while acoustic emission(AE)monitoring captured the temporal evolution of microcracking.The relationships among pore properties,AE b-values,and failure predictability were systematically evaluated.Results show that the overall b-value is primarily controlled by native pore size rather than loading condition.Rocks with larger pores display higher b-value and greater temporal variability,whereas those with smaller pores exhibit lower and more stable b-value.To assess failure predictability,the AE count rate was incorporated into an inverse power law model.The model demonstrates higher predictive accuracy for high-porosity rocks.The average predicted failure time(t_(p))decreases monotonically with porosity:under uniaxial compression,t_(p)for granite,marble,limestone,and sandstone are 2.32,1.82,1.42,and 0.03,respectively;under Brazilian splitting,3.54,3.30,0.10,and 0.03.Among the four rock types,sandstone with the highest porosity exhibits the smallest discrepancy between predicted and actual failure time,whereas granite with the lowest porosity shows the largest.As porosity decreases,prediction accuracy progressively declines for limestone and marble.Overall,the findings indicate that native pore heterogeneity governs both fracture scaling behavior and failure predictability,and that these effects are largely independent of the loading conditions examined in this study.
文摘In the past few decades,the navigation performance of ships and structures in ice-covered waters has not been fully studied,especially the influence of ice mechanical properties on icebreaking ability.Ice bending strength is a key ice parameter for predicting ship ice loads,and accurate ice bending strength is also the key to scaling model tests results to real ship.However,numerical simulation studies on model ice bending strength of ice tanks are often neglected.In this paper,an explicit finite element method model is used to simulate the ice cantilever beam test,and the failure load and bending strength of the ice are obtained.In this model,the Tsai-Wu failure criterion is used as the material constitutive model,and the required simulation parameters are obtained from the model ice test in ice tank.Parameter sensitivity analysis shows that the cantilever beam size of the model ice has a significant effect on the flexural strength.The results show that proper rounding at the root of the cantilever beam is beneficial to reduce stress concentration and obtain more accurate bending strength;the thickness,width and length of the cantilever beam should conform to a certain ratio,and consistent with the ITTC recommended reference.Therefore,the results of this study can promote model ice experiments and numerical studies and provide ice strength data support for ship design and polar ship maneuvering.
文摘Modeling HIV/AIDS progression is critical for understanding disease dynamics and improving patient care. This study compares the Exponential and Weibull survival models, focusing on their ability to capture state-specific failure rates in HIV/AIDS progression. While the Exponential model offers simplicity with a constant hazard rate, it often fails to accommodate the complexities of dynamic disease progression. In contrast, the Weibull model provides flexibility by allowing hazard rates to vary over time. Both models are evaluated within the frameworks of the Cox Proportional Hazards (Cox PH) and Accelerated Failure Time (AFT) models, incorporating critical covariates such as age, gender, CD4 count, and ART status. Statistical evaluation metrics, including Akaike Information Criterion (AIC), Bayesian Information Criterion (BIC), log-likelihood, and Pseudo-R2, were employed to assess model performance across diverse patient subgroups. Results indicate that the Weibull model consistently outperforms the Exponential model in dynamic scenarios, such as younger patients and those with co-infections, while maintaining robustness in stable contexts. This study highlights the trade-off between flexibility and simplicity in survival modeling, advocating for tailored model selection to balance interpretability and predictive accuracy. These findings provide valuable insights for optimizing HIV/AIDS management strategies and advancing survival analysis methodologies.
基金supported by the National Natural Science Foundation of China(Grant Nos.11972283 and 42277182).
文摘High-altitude cold regions exhibit complex geological and environmental conditions,fostering steep rock slopes with macroscopic joints and mesoscopic freeze-thaw(F-T)damage.Cyclic loading further exacerbates rock instability,yet the fracture mechanisms and load response relationships remain poorly understood.This study prepared intact and fractured sandstone specimens,subjected them to F-T cycles and graded loading-unloading,and monitored their structural evolution via X-ray computed tomography.First,the progressive failure process was investigated from both qualitative morphologic features and quantitative void parameters.The results showed that intact and fractured sandstone instability behaviors are determined by F-T damage and joint arrangement,respectively.However,both indicate that precursory localization of failure can only be detected when heterogeneous damage exists in advance.Furthermore,the void parameters of undamaged intact sandstone exhibit power-law acceleration,while damaged sandstones are characterized by a trend of initial decrease followed by an increase.Subsequently,a damage constitutive model for freeze-thawed fractured sandstone under graded loading-unloading was established.This model is based on the Lemaitre strain equivalence hypothesis and defines the coupled damage variable through multivariable indicators.In this framework,the material damage induced by fractures and F-T is unified and characterized by void parameters;while the load-induced damage is integrated with the energy linear allocation law and defined by damage energy.Thus,the stress-strain theoretical relationship is depicted,and the model is validated as reliable.Finally,a conceptual model of rock damage due to F-T and loading-unloading was proposed by combining the microscopic testing results from X-ray diffraction and scanning electron microscopy.
文摘Assessing the stability of slopes is one of the crucial tasks of geotechnical engineering for assessing and managing risks related to natural hazards,directly affecting safety and sustainable development.This study primarily focuses on developing robust and practical hybrid models to predict the slope stability status of circular failure mode.For this purpose,three robust models were developed using a database including 627 case histories of slope stability status.The models were developed using the random forest(RF),support vector machine(SVM),and extreme gradient boosting(XGB)techniques,employing 5-fold cross validation approach.To enhance the performance of models,this study employs Bayesian optimizer(BO)to fine-tuning their hyperparameters.The results indicate that the performance order of the three developed models is RF-BO>SVM-BO>XGB-BO.Furthermore,comparing the developed models with previous models,it was found that the RF-BO model can effectively determine the slope stability status with outstanding performance.This implies that the RF-BO model could serve as a dependable tool for project managers,assisting in the evaluation of slope stability during both the design and operational phases of projects,despite the inherent challenges in this domain.The results regarding the importance of influencing parameters indicate that cohesion,friction angle,and slope height exert the most significant impact on slope stability status.This suggests that concentrating on these parameters and employing the RF-BO model can effectively mitigate the severity of geohazards in the short-term and contribute to the attainment of long-term sustainable development objectives.
基金funded by the National Key Research and Development Program of China(Grant No.2022YFB3402500)the National Natural Science Foundation of China(Grant No.12372129).
文摘Embedding optical fiber sensors into composite materials offers the advantage of real-time structural monitoring.However,there is an order-of-magnitude difference in diameter between optical fibers and reinforcing fibers,and the detailed mechanism of how embedded optical fibers affect the micromechanical behavior and damage failure processes within composite materials remains unclear.This paper presents a micromechanical simulation analysis of composite materials embedded with optical fibers.By constructing representative volume elements(RVEs)with randomly distributed reinforcing fibers,the optical fiber,the matrix,and the interface phase,the micromechanical behavior and damage evolution under transverse tensile and compressive loads are explored.The study finds that the presence of embedded optical fibers significantly influences the initiation and propagation of microscopic damage within the composites.Under transverse tension,the fiber-matrix interface cracks first,followed by plastic cracking in the matrix surrounding the fibers,forming micro-cracks.Eventually,these cracks connect with the debonded areas at the fiber-matrix interface to form a dominant crack that spans the entire model.Under transverse compression,plastic cracking first occurs in the resin surrounding the optical fibers,connecting with the interface debonding areas between the optical fibers and the matrix to form two parallel shear bands.Additionally,it is observed that the strength of the interface between the optical fiber and the matrix critically affects the simulation results.The simulated damage morphologies align closely with those observed using scanning electron microscopy(SEM).These findings offer theoretical insights that can inform the design and fabrication of smart composite materials with embedded optical fiber sensors for advanced structural health monitoring.
基金supported by the National Natural Science Foundation of China(Grant Numbers:12172149 and 12172151).
文摘Electric vehicles,powered by electricity stored in a battery pack,are developing rapidly due to the rapid development of energy storage and the related motor systems being environmentally friendly.However,thermal runaway is the key scientific problem in battery safety research,which can cause fire and even lead to battery explosion under impact loading.In this work,a detailed computational model simulating the mechanical deformation and predicting the short-circuit onset of the 18,650 cylindrical battery is established.The detailed computational model,including the anode,cathode,separator,winding,and battery casing,is then developed under the indentation condition.The failure criteria are subsequently established based on the force–displacement curve and the separator failure.Two methods for improving the anti-short circuit ability are proposed.Results show the three causes of the short circuit and the failure sequence of components and reveal the reason why the fire is more serious under dynamic loading than under quasi-static loading.
基金Project(52374153)supported by the National Natural Science Foundation of ChinaProject(kq2502150)supported by the Natural Science Foundation of Changsha,China。
文摘Cemented tailings backfill(CTB)is a crucial support material for ensuring the long-term stability of underground goafs.A comprehensive understanding of its compressive mechanical behavior is essential for improving engineering safety.Although extensive studies have been conducted on the uniaxial compressive properties of CTB,damage constitutive models that effectively capture its damage evolution process remain underdeveloped,and its failure mechanisms are not yet fully clarified.To address these gaps,this study conducted systematic uniaxial compression tests on CTB specimens prepared with varying cement-tailings ratios.The results revealed distinct compaction and softening phases in the stress−strain curves.A lower cement-tailings ratio significantly reduced the strength and deformation resistance of CTB,along with a decrease in elastic energy accumulation at peak stress and dissipation energy in the post peak stage.Based on these findings,a modified damage constitutive model was developed by introducing a correction factor,enabling accurate simulation of the entire uniaxial compression process of CTB with different cement-tailings ratios.Comparative analysis with classical constitutive models validated the proposed model’s accuracy and applicability in describing the compressive behavior of CTB.Furthermore,particle size distribution and acoustic emission tests were employed to investigate the influence of cement-tailings ratio on failure mechanisms.The results indicated that a lower cement-tailings ratio leads to coarser particle sizes,which intensify shear-related acoustic emission signals and ultimately result in more pronounced macroscopic shear failure.This study provides theoretical support and practical guidance for the optimal design of CTB mix ratios.
基金supported by Guangdong Medical Science and Technology Research Fund Project(No.A2022458)Guangdong Provincial People's Medical Climbing Plan(Nursing Research Project)(No.DFJH2020011)。
文摘Background1 Currently,there is a scarcity of risk prediction models for frailty in hospitalized patients with chronic heart failure(CHF).This study aimed to investigate the frailty status of hospitalized CHF patients,identify independent risk factors significantly associated with frailty,and construct an effective risk prediction model.The goal was to provide a reference for clinical strategies in preventing and managing frailty among CHF patients.Methodss Using convenience sampling,we enrolled 184 hospitalized CHF patients from a tertiary hospital between February 2022 and December 2024.General demographic data were collected via questionnaires,alongside frailty screening using the FRAIL scale and assessment of daily functioning with the Activities of Daily Living(ADL)scale.Clinical data were obtained by reviewing medical records.Participants were categorized into a frail group(n=65)and a non-frail group(n=119)based on frailty status.Clinical risk factors were compared between groups.Multivariate logistic regression was used to identify independent risk factors.A prediction model was constructed,and a receiver operating characteristic(ROC)curve was plotted to evaluate its predictive value.Results A total of 184 hospitalized CHF patients were included,with 65(35.33%)exhibiting frailty.Multivariate logistic regression analysis showed that independent risk factors for frailty included:age,ADL score,N-terminal pro-brain natriuretic peptide(NT-pro-BNP),left ventricular ejection fraction(LVEF),New York Heart Association(NYHA)class II/IV,≥3 comorbidities,comorbid diabetes mellitus(DM),comorbid valvular heart disease(VHD),smoking history,hemoglobin(Hb),albumin,high-density lipoprotein cholesterol(HDL-C),low-density lipoprotein cholesterol(LDL-C),creatinine(Cr),and blood urea nitrogen(BUN).The aforementioned factors were incorporated into logistic regression analysis and the prediction model was built.The prediction model showed quite strong predictive performance.Its area under the ROC curve was 0.904(95%CI:0.857-0.951),with a sensitivity of98.5%and a specificity of 85.7%.ConclusionssThe frailty risk prediction model for hospitalized CHF patients demonstrated robust discriminative ability and calibration.It provided substantial reference value for clinical management of CHF,offering a basis for early assessment,risk stratification,and targeted interventions to prevent frailty by identifying high-risk patients.
基金supported by the China Scholarship Council Program(Grant No.202008320274)it is also supported by Technical University of Munich.
文摘Localized rock failures,like cracks or shear bands,demand specific attention in modeling for solids and structures.This is due to the uncertainty of conventional continuum-based mechanical models when localized inelastic deformation has emerged.In such scenarios,as macroscopic inelastic reactions are primarily influenced by deformation and microstructural alterations within the localized area,internal variables that signify these microstructural changes should be established within this zone.Thus,localized deformation characteristics of rocks are studied here by the preset angle shear experiment.A method based on shear displacement and shear stress differences is proposed to identify the compaction,yielding,and residual points for enhancing the model's effectiveness and minimizing subjective influences.Next,a mechanical model for the localized shear band is depicted as an elasto-plastic model outlining the stress-displacement relation across both sides of the shear band.Incorporating damage theory and an elasto-plastic model,a proposed damage model is introduced to replicate shear stressdisplacement responses and localized damage evolution in intact rocks experiencing shear failure.Subsequently,a novel nonlinear mathematical model based on modified logistic growth theory is proposed for depicting the shear band's damage evolution pattern.Thereafter,an innovative damage model is proposed to effectively encompass diverse rock material behaviors,including elasticity,plasticity,and softening behaviors.Ultimately,the effects of the preset angles,temperature,normal stresses and the residual shear strength are carefully discussed.This discovery enhances rock research in the proposed damage model,particularly regarding shear failure mode.
基金supported by the Research and Development Fund of Peking University People’s Hospital,China(No.PTU2021-02).
文摘BACKGROUND:Acute kidney injury(AKI)is a severe and fatal complication of acute heart failure(AHF).Existing studies on AKI following AHF in the Chinese population have scarce insights available from the emergency department(ED).This study aimed to investigate the predictive factors of patients with AHF complicated with AKI in a Chinese ED cohort,and to establish a risk prediction model.METHODS:Hospitalized patients diagnosed with AHF in the ED from December 2016 to September 2023 were included.The overall dataset were divided into the training set and the testing set at a 7:3 ratio.Univariate and multivariate logistic regression analyses were performed to identify the risk factors for AKI in patients with AHF in the training set,leading to the development of a risk prediction model.The performance of the model was further assessed.RESULTS:A total of 789 patients with AHF were enrolled,with an AKI incidence of 29.7%.The mortality rates of the AKI and non-AKI groups were 23.1%and 7.6%,respectively.Logistic regression analysis showed that the levels of white blood cell(OR=2.368;95%CI:1.502-3.733,P<0.001),albumin(OR=2.669;95%CI:1.601-4.451,P<0.001),serum creatinine(OR=3.221;95%CI:1.935-5.363,P<0.001),and hemoglobin(OR=2.009;95%CI:1.259-3.205,P=0.003),maximum 24-h furosemide dosage(OR=2.196;95%CI:1.346-3.582,P=0.002),the use of non-invasive ventilation(OR=2.419;95%CI:1.454-4.024,P=0.001),and diabetes mellitus(OR=3.192;95%CI:2.014-5.059,P<0.001)were independent risk factors for AKI after AHF.These factors were subsequently incorporated into a risk prediction model.The area under the receiver operating characteristic(AUROC)curve for the predictive model was 0.815(95%CI:0.776-0.854)and 0.802(95%CI:0.776-0.854)in the training set and the testing set,respectively.CONCLUSION:This risk prediction model might assist physician to predict AKI following AHF effectively in the emergency setting.
基金Supported by The Science and Technology Innovation 2030-Major Project,No.2021ZD0140406.
文摘BACKGROUND Partial hepatectomy continues to be the primary treatment approach for liver tumors,and post-hepatectomy liver failure(PHLF)remains the most critical lifethreatening complication following surgery.AIM To comprehensively review the PHLF prognostic models developed in recent years and objectively assess the risk of bias in these models.METHODS This review followed the Checklist for Critical Appraisal and Data Extraction for Systematic Reviews of Prediction Modelling Studies and the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guideline.Three databases were searched from November 2019 to December 2022,and references as well as cited literature in all included studies were manually screened in March 2023.Based on the defined inclusion criteria,articles on PHLF prognostic models were selected,and data from all included articles were extracted by two independent reviewers.The PROBAST was used to evaluate the quality of each included article.RESULTS A total of thirty-four studies met the eligibility criteria and were included in the analysis.Nearly all of the models(32/34,94.1%)were developed and validated exclusively using private data sources.Predictive variables were categorized into five distinct types,with the majority of studies(32/34,94.1%)utilizing multiple types of data.The area under the curve for the training models included ranged from 0.697 to 0.956.Analytical issues resulted in a high risk of bias across all studies included.CONCLUSION The validation performance of the existing models was substantially lower compared to the development models.All included studies were evaluated as having a high risk of bias,primarily due to issues within the analytical domain.The progression of modeling technology,particularly in artificial intelligence modeling,necessitates the use of suitable quality assessment tools.
基金supported by the National Key Research and Development Program of China(2021YFC2500200,2021YFC2500204)the Key Technologies Research and Development Program of Guangdong Province(2023B1111030004)the Guizhou Science and Technology Department(QKHPTRC2018-5636-2,QKHCG2023-ZD010).
文摘Dear Editor,Heart failure(HF)is a common multi-faceted and life-threatening syndrome,of which up to 23%occur acute kidney injury(AKI)[1].HF-related AKI is largely overlooked or delayed in identification[2].Approximately 85%of AKI cases that occurred during cardiac hospitalization in China were either ignored or identifi ed too late[3].Currently,there are no specific guidelines for the management of HF-related AKI.Hence,it is essential to identify patients at the risk of developing AKI and intervene promptly.
基金supported by the National Natural Science Foundation of China(Grant Nos.12102354,12472214 and 12002288)the Young Elite Scientists Sponsorship Program by CAST(Grant No.2022QNRC001)+2 种基金the Guangdong Basic and Applied Basic Research Foundation(Grant Nos.2023A1515012620 and 2024A1515012018)the independent research project of the National Key Laboratory of Strength and Structural Integrity(Grant No.LSSIZZYJ202305)the Basic Research Program of Taicang(Grant No.TC2022JC09).
文摘Ceramic matrix composites have broad application prospects in the aerospace field due to their high temperature resistance and oxidation resistance.The effect of temperature and environment atmosphere on the fracture toughness and failure mechanisms of two-dimensional plain-woven SiC_(f)/SiC composites was investigated.The results show that they exhibit pseudo-plastic deformation behavior at different temperatures.The fracture toughness is as high as 48 MPa m^(1/2)at room temperature,and gradually decreases with rising temperature.The difference in fracture toughness between argon and air initially increases and then decreases with rising temperature.Furthermore,the high-temperature failure mechanisms of these composites were analyzed through macro and micro analysis.Based on this,a physic-based temperature-dependent fracture toughness model considering matrix toughness,plastic power,fiber pull-out,and residual thermal stress was developed for fiber-reinforced ceramic matrix composites.The model has been well validated by experimental results.An analysis of influencing factors regarding the evolution of fracture toughness was conducted by the proposed model.This work contributes to a better understanding of the mechanical performance evolution and failure mechanisms of ceramic matrix composites under multifield coupling conditions,thereby promoting their applications.
基金funded by the Science Committee of the Ministry of Science and Higher Education of the Republic of Kazakhstan(Grant No.AP19680589).
文摘This research extends ongoing efforts to develop methods for reinforcing damaged main gas pipelines to prevent catastrophic failure.This study establishes the use of scaled-down experimental models for assessing the dynamic strength of damaged pipeline sections reinforced with wire wrapping or composite sleeves.A generalized dynamic model is introduced for numerical simulation to evaluate the effectiveness of reinforcement techniques.The model incorporates the elastoplastic behavior of pipe and wire materials,the influence of temperature on mechanical properties,the contact interaction between the pipe and the reinforcement components(including pretensioning),and local material failure under transient internal pressure.Based on these parameters,a finite element model was developed using ANSYS 19.2 to enable parametric studies.The accuracy of the proposed model was verified by comparing the simulation results with the experimental findings.Pipeline section samples containing non-penetrating longitudinal crackswere subjected to comparative analyses and transient pressure until critical failure.The unreinforced and steel wire-wrapped sections were investigated.The results confirm the feasibility of applying the computational model to study the dynamic strength of reinforced damaged pipe sections.Furthermore,pipelines with longitudinal cracks reinforced using circular composite overlays with orthotropic mechanical properties were examined,and recommendations are provided for selecting the geometric parameters of such overlays.
文摘In this editorial,we comment on the article by Teerasarntipan et al published in a recent issue of the World Journal of Gastroenterology.Dengue infection is a major mosquito-borne disease with global significance.Dengue-induced severe hepatitis(DISH)is a rare complication though severe,as it can lead to acute liver failure(ALF)with an incidence rate between 0.7%and 2.0%and mortality rates from 47.0%to 58.8%.In this context,the identification of patients at risk of ALF could improve prognosis in DISH patients.Teerasarntipan et al retrospectively enrolled 2532 dengue patients,counting 193 DISH and 20 ALF.The authors explored the prognostic role of liver-specific scores,as the model for end-stage liver disease(MELD)score,albumin-bilirubin(ALBI)score,easy(EZ)-ALBI score,and platelet-ALBI(PALBI)score.Univariate analysis identified international normalized ratio(INR),total bilirubin,albumin,and creatinine as independent laboratory factors associated with ALF,while age,gender,and liver comorbidities were not linked to in-hospital mortality.The presence of dengue shock syndrome significantly increased mortality,with an odds ratio(OR)of 28.05(95%CI:7.21-109.18,P<0.001).High INR and low albumin were laboratory markers associated with death from DISH,with ORs of 5.83(95%CI:2.59-13.12,P<0.001)and 0.15(95%CI:0.05-0.44,P<0.001),respectively.Multivariate analysis confirmed that INR remained the only significant predictor of both ALF and death,with adjusted ORs of 19.54(95%CI:3.37-113.38,P<0.001)and 3.86(95%CI:1.13-13.18,P=0.031),respectively.Among prognostic models,the MELD score performed best in predicting ALF,with a very high accuracy[area under the receiver operating characteristic curve(AUROC)of 0.929,87.5%sensitivity,89.3%specificity at a cutoff of 16],followed by the EZ-ALBI,ALBI,and PALBI scores,with AUROCs of 0.865,0.832,and 0.797,respectively.As MELD remains the best scoring system for predicting poor outcomes in DISH-related ALF,EZ-ALBI is a valid adjunct tool that could improve medical care in these patients.
基金supported by the National Major Scientific Instruments and Equipment Development Projects of China(No.41827808)the Major Program of the National Natural Science Foundation of China(No.42090055)Supported by Science and Technology Projects of Xizang Autonomous Region,China(No.XZ202402ZD0001)。
文摘In 2018,a catastrophic high-altitude landslide occurred at Baige,located within the tectonic suture zone of the Upper Jinsha River.The failure mechanism of this event remains poorly understood.This study aims to elucidate the deformation characteristics and failure mechanism of the Baige landslide by employing a comprehensive methodology,including field geological surveys,analysis of historical remote sensing imagery,high-density electrical resistivity surveys,and advanced displacement monitoring.Additionally,the physical modeling experiments were conducted to replicate the unique failure modes.The findings propose a novel perspective on the failure mechanism of the Baige landslide,which involves two critical stages:first,the brittle shear zone bypasses and fails at the lower locked segment,and second,the failure of the upper locked segment,combined with the shear zone's impact on the lower locked segment,triggers overall slope instability.Physical modeling experiments revealed a transition from initial acceleration to a rapid acceleration phase,particularly marked by a significant increase in velocity following the failure of the upper locked segment.The intensity of acoustic emission signals was found to correlate with the failure of the locked segments and the state of particle collisions post-failure.It offers new insights into the failure mechanisms of tectonic mélange belt large-scale landslides in suture zones,contributing to the broader field of landslide research.
文摘Objective:To explore the effect of implementing a time-sensitive incentive model combined with specialized rehabilitation nursing in patients with severe pneumonia and respiratory failure.Methods:Seventy-eight patients with severe pneumonia and respiratory failure admitted from January 2024 to February 2025 were selected and randomly divided into two groups using a computer-based random drawing method.The control group(39 patients)received routine nursing,while the observation group(39 patients)received a time-sensitive incentive model combined with specialized rehabilitation nursing.Lung function and adverse emotional states were compared between the two groups.Results:After 2 weeks of nursing,the lung function of the observation group was higher than that of the control group(P<0.05),and the adverse emotional states of the observation group were lower than those of the control group(P<0.05).Conclusion:Implementing a time-sensitive incentive model combined with specialized rehabilitation nursing in patients with severe pneumonia and respiratory failure can improve lung function and emotional state.
基金Project(51174128)supported by the National Natural Science Foundation of ChinaProject(20123718110007)supported by the Specialized Research Fund for the Doctoral Program of Higher Education of China
文摘Four different types of three-body model composed of rock and coal with different strength and stiffness were established in order to study the failure characteristics of compound model such as roof-coal-floor. Through stress analysis of the element with variable strength and stiffness extracted from the strong-weak interface, the tri-axial compressive strength of the weak body and strong body near the interface as well as the areas away from the contact surface was found. Then, on the basis of three-dimensional fast Lagrangian method of continua and strain softening constitutive model composed of Coulomb-Mohr shear failure with tensile cut-off, stress and strain relationship of the four three-body combined models were analyzed under different confining pressures by numerical simulation. Finally, the different features of local shear zones and plastic failure areas of the four different models and their development trend with increasing confining pressure were discussed. The results show that additional stresses are derived due to the lateral deformation constraints near the strong-weak interface area, which results in the strength increasing in weak body and strength decreasing in strong body. The weakly consolidated soft rock and coal cementation exhibit significant strain softening behavior and bear compound tension-shear failure under uni-axial compression. With the increase of confining pressure, the tensile failure disappears from the model, and the failure type of composed model changes to local shear failure with different number of shearing bands and plastic failure zones. This work shows important guiding significance for the mechanism study of seismic, rock burst, and coal bump.
