Rhegmatogenous retinal detachment(RRD)is a serious ocular condition marked by the separation of the neuroretina from the retinal pigment epithelium(RPE).The pathogenesis of RRD involves intricate molecular and cellula...Rhegmatogenous retinal detachment(RRD)is a serious ocular condition marked by the separation of the neuroretina from the retinal pigment epithelium(RPE).The pathogenesis of RRD involves intricate molecular and cellular mechanisms,including inflammation,cell migration,and the activation of proliferative signaling pathways.One of the most challenging complications of RRD is proliferative vitreoretinopathy(PVR),which refers to the proliferation and contraction of fibrocellular membranes on the retinal surface and in the vitreous cavity.PVR is a major cause of surgical failure in RRD,as it can lead to recurrent retinal detachment and severe vision loss.However,the pathogenesis of PVR is not yet fully understood,and the treatment options are quite limited.Recent advances in analytical techniques have offered valuable insights into the molecular alterations present in the subretinal fluid(SRF)of patients with RRD.This review seeks to consolidate the current knowledge regarding the SRF profile in RRD and PVR,emphasizing potential biomarkers and therapeutic targets.展开更多
AIM:To investigate the effects of shortening the duration of silicone oil tamponade on retinal structure and function in patients undergoing silicone oil removal(SOR)after surgery for primary rhegmatogenous retinal de...AIM:To investigate the effects of shortening the duration of silicone oil tamponade on retinal structure and function in patients undergoing silicone oil removal(SOR)after surgery for primary rhegmatogenous retinal detachment(RRD).METHODS:A total of 58 eligible patients were enrolled and randomly assigned to two groups based on tamponade duration:the short-term group(30-45d)and the conventional group(≥90d).Comprehensive evaluations were performed before and after SOR,including slitlamp examination,best-corrected visual acuity(BCVA)measurement,intraocular pressure(IOP)testing,optical coherence tomography(OCT),optical coherence tomography angiography(OCTA),microperimetry,electroretinography(ERG),and visual evoked potential(VEP)assessment.RESULTS:A total of 33 patients(23 males and 10 females;33 eyes)were enrolled in the short-term SO tamponade group with mean age of 52.45±9.35y,and 25 patients(15 males and 10 females;25 eyes)were enrolled in the conventional SO tamponade group with mean age of 50.80±12.06y.Compared with the conventional group,the short-term silicone oil tamponade group had a significantly lower incidence of silicone oil emulsification and cataract progression,with no significant difference in retinal reattachment success rate.Structurally,short-term tamponade was associated with increased thickness of the retinal ganglion cell layer(RGCL)in the nasal and superior macular regions and improved recovery of superficial retinal vascular density in these areas.Functionally,the shortterm group showed better BCVA and retinal sensitivity both before and 1mo after SOR;additionally,the P100 amplitude in VEP tests was significantly increased in this group.CONCLUSION:Shortening the duration of silicone oil tamponade effectively reduces damage to retinal structure and function without compromising the success rate of retinal reattachment in patients with primary RRD.展开更多
Improvements in surgical techniques have led to 90% success in the surgical repair of rhegmatogenous retinal detachment(RRD).However,anatomical reattachment of the retina does not ensure complete recovery of visual fu...Improvements in surgical techniques have led to 90% success in the surgical repair of rhegmatogenous retinal detachment(RRD).However,anatomical reattachment of the retina does not ensure complete recovery of visual function.The incidence of metamorphopsia remains the most common postoperative complaint,from 24% to 88.6%.Currently,the risk factors of metamorphopsia are categorized into macular involvement,retinal shift,outer retinal folds,subretinal fluid,secondary epiretinal membrane,outer retinal layer damage,and surgical approach.The associations of metamorphopsia with postoperative best-corrected visual acuity and postoperative vision-related quality of life were still controversial.The most popular methods for assessment of metamorphopsia remain the Amsler grid and M-Charts.Most treatments cannot progress beyond the management of negative visual sensations,through methods such as occlusion therapy and aniseikonia-correcting spectacles.The main treatment approach involves RRD prevention and the management of risk factors that can lead to postoperative metamorphopsia after RRD repair.Additional research concerning metamorphopsia treatment,further upgrades of auxiliary inspection methods,and more accurate microstructural assessments are needed to address this common complication.展开更多
The study focuses on the creep characteristics of significant yellow sandstone for water conservancy, hydropower, and other waterrelated slope excavation unloading rock-graded loading creep characteristics. It conduct...The study focuses on the creep characteristics of significant yellow sandstone for water conservancy, hydropower, and other waterrelated slope excavation unloading rock-graded loading creep characteristics. It conducts a uniaxial graded loading creep test on yellow sandstone under different pre-peak unloading and wetting-drying cycles. The improved nonlinear Nishihara model was obtained by introducing a nonlinear viscous element with an accelerated creep threshold switch. The sensitivity characteristics of the parameters of the improved creep model were analyzed and a nonlinear creep constitutive model was established, considering the unloading-cyclic intrinsic damage induced by water intrusion. The research results show that:(1)With an increase in the unloading point, the porosity of the rock samples initially decreases and then increases. As the number of cyclic water intrusions rises, the porosity of the rock samples gradually increases, reaching a maximum of 9.58% at an unloading point of 70% uniaxial compression stress(0.7 Rc) after five cycles.(2) Total creep deformation increases with the number of cyclic water intrusions;however, with an increase in the unloading ratio, the original samples show an initial decrease, followed by an increase in creep deformation. With a higher unloading ratio and various instances of cyclic water intrusion, the total creep time of the rock samples,compared to the original samples, is reduced by 21.8%and 23.02%. The creep damage mode gradually changes from shear damage to tensile damage.(3) The sensitivity characteristics of the improved creep model parameters show that transient elasticity modulus E1 is affected by the coupling of unloading and cyclic water intrusion. The viscoelastic modulus E2 and viscous coefficient η1 are mainly affected by unloading and cyclic water intrusion.(4) Based on the strain equivalence principle of damage mechanics, the damage treatment of the parameters in the original model is improved to construct a nonlinear creep constitutive model that considers unloading-cyclic water intrusion damage. A parameter inversion and comparison to the traditional Nishihara model reveal an average relative standard deviation of 0.271%,significantly less than 1%, indicating a more accurate nonlinear creep constitutive model. The research results are crucial for analyzing the long-term stability of water-related steep rocky slopes post-excavation and unloading and for preventing and controlling creep-type landslide disasters.展开更多
A series of true triaxial unloading tests are conducted on sandstone specimens with a single structural plane to investigate their mechanical behaviors and failure characteristics under different in situ stress states...A series of true triaxial unloading tests are conducted on sandstone specimens with a single structural plane to investigate their mechanical behaviors and failure characteristics under different in situ stress states.The experimental results indicate that the dip angle of structural plane(θ)and the intermediate principal stress(σ2)have an important influence on the peak strength,cracking mode,and rockburst severity.The peak strength exhibits a first increase and then decrease as a function ofσ2 for a constantθ.However,whenσ2 is constant,the maximum peak strength is obtained atθof 90°,and the minimum peak strength is obtained atθof 30°or 45°.For the case of an inclined structural plane,the crack type at the tips of structural plane transforms from a mix of wing and anti-wing cracks to wing cracks with an increase inσ2,while the crack type around the tips of structural plane is always anti-wing cracks for the vertical structural plane,accompanied by a series of tensile cracks besides.The specimens with structural plane do not undergo slabbing failure regardless ofθ,and always exhibit composite tensile-shear failure whatever theσ2 value is.With an increase inσ2 andθ,the intensity of the rockburst is consistent with the tendency of the peak strength.By analyzing the relationship between the cohesion(c),internal friction angle(φ),andθin sandstone specimens,we incorporateθinto the true triaxial unloading strength criterion,and propose a modified linear Mogi-Coulomb criterion.Moreover,the crack propagation mechanism at the tips of structural plane,and closure degree of the structural plane under true triaxial unloading conditions are also discussed and summarized.This study provides theoretical guidance for stability assessment of surrounding rocks containing geological structures in deep complex stress environments.展开更多
Dear Editor,Descemet’s membrane detachment(DMD)is considered as a potential sight-threatening complication following various intraocular surgeries,particularly cataract surgery[1].The labile adhesion between the Desc...Dear Editor,Descemet’s membrane detachment(DMD)is considered as a potential sight-threatening complication following various intraocular surgeries,particularly cataract surgery[1].The labile adhesion between the Descemet’s membrane(DM)and the posterior corneal stromal layer can be easily separated with minimal mechanical force.Several risk factors have been associated with the development of DMD including old age,improper intraoperative operation,corneal ectatic disorders,and endothelial disorders and so on[1-4].展开更多
Purpose:To summarize and analyze the clinical features and management of postoperative choroidal detachment in glaucoma.Methods:Ten cases of choroidal detachment that occurred after glaucoma surgery were collected fro...Purpose:To summarize and analyze the clinical features and management of postoperative choroidal detachment in glaucoma.Methods:Ten cases of choroidal detachment that occurred after glaucoma surgery were collected from March 2023 to February 2024 in the hospital.Their clinical characteristics and treatment effects were observed and their causes were analyzed.Results:After the operations,the eyes with choroidal detachment after glaucoma surgery had 2 cases of true microphthalmos,6 cases of advanced glaucoma,and 2 cases of glaucoma secondary to vitreoretinal surgery.The postoperative manifestations were persistent shallow anterior chamber,the formation of anterior chamber,and then suddenly became shallow or disappeared.Meanwhile,the intraocular pressure was lower than 6 mmHg.Ultrasound and funduscopic examination showed that the choroid and retina were partially elevated,and the choroidal detachment recovered after treatment.Conclusion:Choroidal detachment is one of the common postoperative complications in glaucoma,especially in some special types of refractory glaucoma.Adequate perioperative management before surgery,cautious and delicate operation during surgery,and close observation and treatment after surgery can obviously decrease the occurrence and damage.展开更多
AIM:To compare the proportion of rhegmatogenous retinal detachment(RRD)associated with choroidal detachment(RRDCD)in the emergency surgery group with the routine inpatient surgery group and determine risk factors for ...AIM:To compare the proportion of rhegmatogenous retinal detachment(RRD)associated with choroidal detachment(RRDCD)in the emergency surgery group with the routine inpatient surgery group and determine risk factors for RRDCD.METHODS:A total of 694 patients(694 eyes)diagnosed with RRD in the emergency surgery(the median duration of RRD was 5d)group were included from the Department of Ophthalmic Emergency,and 692 patients(eyes)in the routine inpatient surgery group(the median duration was 15d)were selected randomly from the Ocular Fundus Department.Demographics,refractive status,macular status,lens status,extent of retinal detachment,number of retinal breaks,duration of symptoms before surgery,and the incidence of RRDCD were compared.A logistic regression analysis was used to determine potential risk factors for RRDCD.RESULTS:Compared to the routine inpatient surgery group,the emergency surgery group had a significant less median time to surgery(P<0.001)and a decreased proportion of RRDCD(2.88%vs 10.84%,P<0.001).Logistic regression analysis revealed that a prolonged duration of RRD[OR 3.51,95%confidence interval(CI)1.98-6.23],pseudophakia/aphakia status[OR 2.74,95%CI(1.50-4.98)],multiple retinal breaks[OR 1.67,95%CI(1.03-2.70)],and a substantial extent of RRD[OR 11.58,95%CI(7.12-18.84)]were independent risk factors for RRDCD.CONCLUSION:Emergency surgical pattern of RRD demonstrates a lower incidence of RRDCD.The adoption of an expedited surgical approach has the potential to reduce the duration of RRD,possibly correlating with a decreased risk of RRDCD development.展开更多
AIM:To report the refractive and surgical outcomes of scleral buckling(SB)with or without pars plana vitrectomy(PPV)in patients with pseudophakic rhegmatogenous retinal detachment(PRRD).METHODS:A consecutive case seri...AIM:To report the refractive and surgical outcomes of scleral buckling(SB)with or without pars plana vitrectomy(PPV)in patients with pseudophakic rhegmatogenous retinal detachment(PRRD).METHODS:A consecutive case series of patients with pseudophakia who underwent retinal detachment(RD)surgery was enrolled.The SB procedures were selected to initially treat primary pseudophakic PRRDs and SB-PPV for more complex cases,according to preoperative findings.Eyes with anterior chamber intraocular lens,proliferative vitreoretinopathy anterior to equator,previous invasive glaucoma surgery,severe degenerative myopia or macular hole,and<6mo follow-up were excluded from outcomes analysis.The primary clinical outcome measures were the single surgery anatomic success(SSAS)and final surgery anatomic success(FSAS)rates.Secondary outcome measures were postoperative visual acuity and refractive error.RESULTS:A total of 81 consecutive patients(81 eyes)were enrolled for analysis,comprising 66(81%)men and 15(19%)women with a mean age of 58y(range,33-86y)and the mean final follow-up period was 21.0±19.6mo.A total of 62 PRRDs(n=62;76.5%)were repaired with an initial SB,and 19 PRRDs(n=19;23.5%)were repaired with a combined SB-PPV.The SSAS and FSAS rates were 92.6%(75/81)and 100%(81/81),respectively.All initial failures had retinal reattachment after the secondary PPV.The mean final postoperative best-corrected visual acuity(BCVA)was 0.42±0.33 logMAR(visual acuity 20/55)and final mean refractive error was-1.48±1.40 diopters.The patients who underwent initially SB-PPV had a significantly longer duration of RD and a higher giant retinal tear rate(P<0.05)preoperatively.SSAS was 56/62(90.3%)and 19/19(100%),and the mean postoperative refractive error was-1.30±1.32 D and-1.53±1.38 D for the patients in the SB and SB-PPV groups,respectively.There was no statistically significant difference for those who had SSAS and postoperative refractive errors between the 2 groups.The postoperative BCVAs of the patients with SSAS were not significantly better in the SB group(median,20/40)than in the SB-PPV group(median 20/50).In the SB group,patients with macula-on had better visual acuity postoperatively than patients with macula-off(P=0.000).CONCLUSION:The initial surgical procedures of SB with or without PPV according to the preoperative findings achieve a high reattachment rate and an acceptable refractive error for primary pseudophakic RRD management.展开更多
Fissured coal mass under triaxial unloading condition exhibits higher burst potential than the triaxial loading condition,which poses challenge to safety and productivity of resources extraction and underground space ...Fissured coal mass under triaxial unloading condition exhibits higher burst potential than the triaxial loading condition,which poses challenge to safety and productivity of resources extraction and underground space utilization.To comprehensively understand the mechanism of unloading-induced burst during excavation process,this study investigated the fracture and energy evolution of samples with different fissure types such as single,two parallel,and two coplanar-parallel using PFC2D modelling.Triaxial loading tests were conducted to determine the compressive strengths and other parameters.With increase of fissure inclination angle,the triaxial compressive strength decreases forβ=0°-30°,and then increase forβ=30°-90°.The strength of samples with two coplanar-parallel fissures is the highest.Fissure can significantly change the distribution of fracture and elastic energy.Secondary cracks were generated starting from both ends of the fissure.Forβ=0°-60°,low elastic strain energy area was produced around the fissure along the loading direction.The elastic strain energy is transferred to the outside of fissures.Forβ=75°-90°,only a small amount of high elastic strain energy was generated on both sides of the fissure.The fracture expansion under unloading conditions occurred due to tensile stress T caused by unloading differential rebound deformation and the shear stress on the fissure surface.展开更多
During the EAST radiative divertor experiments,one of the key challenges was how to avoid the occurrence of disruptive events caused by excessive impurity seeding.To estimate the required impurity fraction for diverto...During the EAST radiative divertor experiments,one of the key challenges was how to avoid the occurrence of disruptive events caused by excessive impurity seeding.To estimate the required impurity fraction for divertor detachment,we introduce a reduced edge plasma radiation model.In the model,based on the momentum conservation along the magnetic field line,the upstream pressure is determined by the plasma density and temperature at the divertor target,and then the impurity radiation loss is obtained by the balance of the heat and particle fluxes.It is found that the required impurity fraction shows a non-monotonic variation with divertor electron temperature(T_(d))when 0.1 eV<T_(d)<10 eV.In the range of 0.1 eV<T_(d)<1 e V,the position near the valley of required impurity fraction corresponds to strong plasma recombination.Due to the dependence of the volumetric momentum loss effect on the T_(d)in the range of 1 eV<T_(d)<10 eV,the required impurity fraction peaks and then decreases as T_(d)is increased.Compared to neon,the usage of argon reduces the impurity fraction by about twice.In addition,for the various fitting parameters in the pressure-momentum loss model,it is shown that the tendency of required impurity fraction with T_(d)always increases first and then decreases in the range of 1 eV<T_(d)<10 eV,but the required impurity fraction decreases when the model that characterizes the strong loss in pressure momentum is used.展开更多
Gas rapid unloading(GRU)is an innovative technology for ore comminution.Increasing the production of fine powder in each ore grinding cycle is vital for scaling up the GRU method to industrial applications.This study ...Gas rapid unloading(GRU)is an innovative technology for ore comminution.Increasing the production of fine powder in each ore grinding cycle is vital for scaling up the GRU method to industrial applications.This study utilizes laboratory experiments to demon-strate that moderately reducing the orifice size significantly enhances pulverization and increases fine particle yield.Numerical simulations suggest that smaller orifices improve pulverization by increasing jet speed,reducing pressure drop,and creating a larger pressure difference inside and outside the unloading orifice.The orifice size should be optimized based on feed size to ensure efficient ore discharge.Reducing the unloading orifice size improves GRU grinding efficiency and energy use,offering guidance for the design of ore discharge ports in future industrial-scale equipment.展开更多
Kinesin is an archetypal microtubule-based molecular motor that can generate force to transport cargo in cells. The load dependence of the detachment rate is an important factor of the kinesin motor, the determination...Kinesin is an archetypal microtubule-based molecular motor that can generate force to transport cargo in cells. The load dependence of the detachment rate is an important factor of the kinesin motor, the determination of which is critically related to the chemomechanical coupling mechanism of the motor. Here, we use three models for the load dependence of the detachment rate of the kinesin motor to study theoretically and numerically the maximal force generated and microtubuleattachment duration of the motor. By comparing the theoretical and numerical results with the available experimental data,we show that only one model can explain well the available experimental data, indicating that only this model can be applicable to the kinesin motor.展开更多
This paper presents a new criterion for determining the unloading points quantitatively and consistently in a multi-stage triaxial test.The radial strain gradient(RSG)is first introduced as an arc tangent function of ...This paper presents a new criterion for determining the unloading points quantitatively and consistently in a multi-stage triaxial test.The radial strain gradient(RSG)is first introduced as an arc tangent function of the rate of change of radial strain to time.RSG is observed to correlate closely with the stress state of a compressed sample,and reaches a horizontal asymptote as approaching failure.For a given rock type,RSG value at peak stress is almost the same,irrespective of the porosity and permeability.These findings lead to the development of RSG criterion:Unloading points can be precisely determined at the time when RSG reaches a pre-determined value that is a little smaller than or equal to the RSG at peak stress.The RSG criterion is validated against other criteria and the single-stage triaxial test on various types of rocks.Failure envelopes from the RSG criterion match well with those from single-stage tests.A practical procedure is recommended to use the RSG criterion:an unconfined compression or single-stage test is first conducted to determine the RSG at peak stress for one sample,the unloading point is then selected to be a value close to the RSG at peak stress,and the multi-stage test is finally performed on another sample using the pre-selected RSG unloading criterion.Generally,the RSG criterion is applicable for any type of rocks,especially brittle rocks,where other criteria are not suitable.Further,it can be practically implemented on the most available rock mechanical testing instruments.展开更多
AIM:To establish a risk prediction model for secondary cataract within 2y after pars plana vitrectomy(PPV)in patients with primary rhegmatogenous retinal detachment(RRD).METHODS:Clinical data of patients with primary ...AIM:To establish a risk prediction model for secondary cataract within 2y after pars plana vitrectomy(PPV)in patients with primary rhegmatogenous retinal detachment(RRD).METHODS:Clinical data of patients with primary RRD treated at the Shenzhen Eye Hospital were retrospectively collected.Twenty-four potential influencing factors,including patient characteristics and surgical factors,were selected for analysis.Independent risk factors for secondary cataract were identified through univariate comparisons and multivariate logistic regression analysis.A risk prediction model was constructed and evaluated using receiver operating characteristic(ROC)curves,area under the ROC curve(AUC),calibration plots,and decision curve analysis(DCA)curves.RESULTS:The 386 cases(389 eyes)of patients who underwent PPV and had complete surgical records were ultimately included.Within a 2-year longitudinal observation,41.39%of patients developed cataract secondary to PPV.Logistic regression results identified a history of hypertension[odds ratio(OR)=1.78,95%CI:1.002–3.163,P=0.049],silicone oil tamponade(OR=3.667,95%CI:2.373–5.667,P=0.000),and lens thickness(OR=1.978,95%CI:1.129–3.464,P=0.017)as independent risk factors for cataract secondary to PPV.The constructed nomogram achieved AUC=0.6974.Calibration plots indicated good agreement between predicted and observed outcomes,while DCA curves demonstrated the model’s clinical utility.CONCLUSION:By incorporating a history of hypertension,vitreous substitute type,and lens thickness,this study constructs a prediction model with moderate discriminative ability.This model offers a valuable tool for clinicians to identify high-risk patients early,potentially allowing for more timely interventions and improved patient outcomes.展开更多
In this study,based on the rockburst disaster mechanism of excess energy △E>0,true triaxial transient unloading strainburst(including instantaneous strainburst and delayed strainburst)experiments were performed on...In this study,based on the rockburst disaster mechanism of excess energy △E>0,true triaxial transient unloading strainburst(including instantaneous strainburst and delayed strainburst)experiments were performed on granite specimens at different maximum principal stress levels.The experimental results were then analyzed,with the strainburst characteristics and acoustic emission(AE)responses of the granite specimens being examined.The excess energy △E was derived through a comparison with the results of conventional biaxial compression tests.The following beneficial conclusions were drawn.The mechanical strength of delayed strainburst specimens initially increases and then decreases with the rise of the unloading stress level.In contrast,the mechanical strength of instantaneous strainburst specimens is higher than that of delayed ones,increasing with the unloading stress level.In terms of fragment ejection velocity and scale,the rockburst intensity of a specimen is positively correlated with its mechanical strength.A pronounced linear relationship exists between the excess energy △E and the fragment ejection velocity(as well as weight),indicating that △E is intimately linked to the kinetic energy of rockbursts.Rockbursts lead to the formation of burst pits and typical V-shaped damage zones near the free face of the specimens,within which tensile cracks dominate.Additionally,the distribution of AE AFRA values indicates that the proportion of tensile cracks increases with the rise of unloading stress level,suggesting that transient unloading under high stress levels significantly promotes tensile fracture.It is anticipated that this study will provide further elucidation on the mechanism of rockburst kinetic energy generation,thereby establishing a foundation for the design of rockburst support measures in engineering applications.展开更多
It is important to analyze the damage evolution process of surrounding rock under different water content for the stability of engineering rock mass.Based on digital speckle correlation(DSCM),acoustic emission(AE)and ...It is important to analyze the damage evolution process of surrounding rock under different water content for the stability of engineering rock mass.Based on digital speckle correlation(DSCM),acoustic emission(AE)and electromagnetic radiation(EMR),uniaxial hierarchical cyclic loading and unloading tests were carried out on sandstones with different fracture numbers under dry,natural and saturated water content,to explore the fracture propagation,failure precursor characteristics and damage response mechanism under the influence of water content effect.The results show that with the increase of water content,the peak stress and crack initiation stress decrease gradually,and the decreases are 15.28%-21.11%and 17.64%-23.04%,respectively.The peak strain and crack initiation strain increase gradually,and the increases are 19.85%-44.53%and 19.15%-41.94%,respectively.The precracked rock with different water content is mainly characterized by tensile failure at different loading stages.However,with the increase of water content,the proportion of shear cracks gradually increases,while acoustic emission events gradually decrease,the dissipative energy and energy storage limits of the rock under peak load gradually decrease,and the charge signal increases significantly,which is because the lubrication effect of water reduces the friction coefficient between crack surfaces.展开更多
This article investigates the mechanical responses and acoustic emission(AE)characteristics of sandstone under the triaxial differential cyclic loading(DCL)at different unloading rates of confining stress.The test res...This article investigates the mechanical responses and acoustic emission(AE)characteristics of sandstone under the triaxial differential cyclic loading(DCL)at different unloading rates of confining stress.The test results indicate that strength of rock specimens under different stress paths of triaxial unloading confining stress-differential cyclic loading(TUCS-DCL)can be fitted by the Mohr–Coulomb,Hoek–Brown,and Bieniawski criteria.The confining stress unloading rate can dominate the radial strain rate,while the axial DCL pattern has an unpronounced effect.The confining stress unloading rate affects the energy evolution in radial and axial directions of specimens,with the ratio of radially released energy to axially consumed energy fluctuating more significantly during the fast unloading of confining stress,the valley value of the ratio can serve as a precursor for failure.The confining stress unloading rate has no significant effect on stress–strain phase shift,while axial rapid-loading-slow-unloading can correspond to a larger magnitude of phase shift.AE signals begin to significantly increase after the confining stress is unloaded to zero,and a notable Kaiser effect is observed during cyclic loading preceding the failure.展开更多
Rhegmatogenous retinal detachment(RRD)is a sight threatening condition in which the neurosensory retina separates from the underlying retinal pigment epithelium.With an incidence of 6.3 to 17.9 per 100,000 persons(1),...Rhegmatogenous retinal detachment(RRD)is a sight threatening condition in which the neurosensory retina separates from the underlying retinal pigment epithelium.With an incidence of 6.3 to 17.9 per 100,000 persons(1),RRD is a condition frequently encountered by vitreoretinal specialists.Because the fovea is responsible for central visual acuity,foveal detachment is associated with poor presenting vision and is the strongest prognostic factor predicting poor visual outcome after RRD repair(2).展开更多
During the excavation of large-scale rock slopes and deep hard rock engineering,the induced rapid unloading serves as the primary cause of rock mass deformation and failure.The essence of this phenomenon lies in the o...During the excavation of large-scale rock slopes and deep hard rock engineering,the induced rapid unloading serves as the primary cause of rock mass deformation and failure.The essence of this phenomenon lies in the opening-shear failure process triggered by the normal stress unloading of fractured rock mass.In this study,we focus on local-scale rock fracture and conduct direct shear tests under different normal stress unloading rates on five types of non-persistent fractured hard rocks.The aim is to analyze the influence of normal stress unloading rates on the failure modes and shear mechanical characteristics of non-persistent fractured rocks.The results indicate that the normal unloading displacement decreases gradually with increasing normal stress unloading rate,while the influence of normal stress unloading rate on shear displacement is not significant.As the normal stress unloading rate increases,the rocks brittle failure process accelerates,and the degree of rocks damage decreases.Analysis of the stress state on rock fracture surfaces reveals that increasing the normal stress unloading rate enhances the compressive stress on rocks,leading to a transition in the failure mode from shear failure to tensile failure.A negative exponential strength formula was proposed,which effectively fits the relationship between failure normal stress and normal stress unloading rate.The findings enrich the theoretical foundation of unloading rock mechanics and provide theoretical support for disasters prevention and control in rock engineering excavations.展开更多
文摘Rhegmatogenous retinal detachment(RRD)is a serious ocular condition marked by the separation of the neuroretina from the retinal pigment epithelium(RPE).The pathogenesis of RRD involves intricate molecular and cellular mechanisms,including inflammation,cell migration,and the activation of proliferative signaling pathways.One of the most challenging complications of RRD is proliferative vitreoretinopathy(PVR),which refers to the proliferation and contraction of fibrocellular membranes on the retinal surface and in the vitreous cavity.PVR is a major cause of surgical failure in RRD,as it can lead to recurrent retinal detachment and severe vision loss.However,the pathogenesis of PVR is not yet fully understood,and the treatment options are quite limited.Recent advances in analytical techniques have offered valuable insights into the molecular alterations present in the subretinal fluid(SRF)of patients with RRD.This review seeks to consolidate the current knowledge regarding the SRF profile in RRD and PVR,emphasizing potential biomarkers and therapeutic targets.
基金Supported by the Key Science&Technology Project of Guangzhou(No.202103000045)the National Natural Science Foundation of China(No.82070972,No.82271093).
文摘AIM:To investigate the effects of shortening the duration of silicone oil tamponade on retinal structure and function in patients undergoing silicone oil removal(SOR)after surgery for primary rhegmatogenous retinal detachment(RRD).METHODS:A total of 58 eligible patients were enrolled and randomly assigned to two groups based on tamponade duration:the short-term group(30-45d)and the conventional group(≥90d).Comprehensive evaluations were performed before and after SOR,including slitlamp examination,best-corrected visual acuity(BCVA)measurement,intraocular pressure(IOP)testing,optical coherence tomography(OCT),optical coherence tomography angiography(OCTA),microperimetry,electroretinography(ERG),and visual evoked potential(VEP)assessment.RESULTS:A total of 33 patients(23 males and 10 females;33 eyes)were enrolled in the short-term SO tamponade group with mean age of 52.45±9.35y,and 25 patients(15 males and 10 females;25 eyes)were enrolled in the conventional SO tamponade group with mean age of 50.80±12.06y.Compared with the conventional group,the short-term silicone oil tamponade group had a significantly lower incidence of silicone oil emulsification and cataract progression,with no significant difference in retinal reattachment success rate.Structurally,short-term tamponade was associated with increased thickness of the retinal ganglion cell layer(RGCL)in the nasal and superior macular regions and improved recovery of superficial retinal vascular density in these areas.Functionally,the shortterm group showed better BCVA and retinal sensitivity both before and 1mo after SOR;additionally,the P100 amplitude in VEP tests was significantly increased in this group.CONCLUSION:Shortening the duration of silicone oil tamponade effectively reduces damage to retinal structure and function without compromising the success rate of retinal reattachment in patients with primary RRD.
文摘Improvements in surgical techniques have led to 90% success in the surgical repair of rhegmatogenous retinal detachment(RRD).However,anatomical reattachment of the retina does not ensure complete recovery of visual function.The incidence of metamorphopsia remains the most common postoperative complaint,from 24% to 88.6%.Currently,the risk factors of metamorphopsia are categorized into macular involvement,retinal shift,outer retinal folds,subretinal fluid,secondary epiretinal membrane,outer retinal layer damage,and surgical approach.The associations of metamorphopsia with postoperative best-corrected visual acuity and postoperative vision-related quality of life were still controversial.The most popular methods for assessment of metamorphopsia remain the Amsler grid and M-Charts.Most treatments cannot progress beyond the management of negative visual sensations,through methods such as occlusion therapy and aniseikonia-correcting spectacles.The main treatment approach involves RRD prevention and the management of risk factors that can lead to postoperative metamorphopsia after RRD repair.Additional research concerning metamorphopsia treatment,further upgrades of auxiliary inspection methods,and more accurate microstructural assessments are needed to address this common complication.
基金We gratefully acknowledge the financial support from the Key Laboratory of Geological Safety of Coastal Urban Underground Space,Ministry of Natural Resources(BHKF2022Y03)Shandong Provincial Colleges and Universities Youth Innovation Technology Support Program,Education Department of Shandong Province(grant number 2023KJ092).
文摘The study focuses on the creep characteristics of significant yellow sandstone for water conservancy, hydropower, and other waterrelated slope excavation unloading rock-graded loading creep characteristics. It conducts a uniaxial graded loading creep test on yellow sandstone under different pre-peak unloading and wetting-drying cycles. The improved nonlinear Nishihara model was obtained by introducing a nonlinear viscous element with an accelerated creep threshold switch. The sensitivity characteristics of the parameters of the improved creep model were analyzed and a nonlinear creep constitutive model was established, considering the unloading-cyclic intrinsic damage induced by water intrusion. The research results show that:(1)With an increase in the unloading point, the porosity of the rock samples initially decreases and then increases. As the number of cyclic water intrusions rises, the porosity of the rock samples gradually increases, reaching a maximum of 9.58% at an unloading point of 70% uniaxial compression stress(0.7 Rc) after five cycles.(2) Total creep deformation increases with the number of cyclic water intrusions;however, with an increase in the unloading ratio, the original samples show an initial decrease, followed by an increase in creep deformation. With a higher unloading ratio and various instances of cyclic water intrusion, the total creep time of the rock samples,compared to the original samples, is reduced by 21.8%and 23.02%. The creep damage mode gradually changes from shear damage to tensile damage.(3) The sensitivity characteristics of the improved creep model parameters show that transient elasticity modulus E1 is affected by the coupling of unloading and cyclic water intrusion. The viscoelastic modulus E2 and viscous coefficient η1 are mainly affected by unloading and cyclic water intrusion.(4) Based on the strain equivalence principle of damage mechanics, the damage treatment of the parameters in the original model is improved to construct a nonlinear creep constitutive model that considers unloading-cyclic water intrusion damage. A parameter inversion and comparison to the traditional Nishihara model reveal an average relative standard deviation of 0.271%,significantly less than 1%, indicating a more accurate nonlinear creep constitutive model. The research results are crucial for analyzing the long-term stability of water-related steep rocky slopes post-excavation and unloading and for preventing and controlling creep-type landslide disasters.
基金supports from the National Natural Science Foundation of China (Grant Nos.52004143 and 52374095)the open fund for the Laboratory of Mining Response and Disaster Prevention and Control in Deep Coal Mines (Grant No.SKLMRDPC21KF06).
文摘A series of true triaxial unloading tests are conducted on sandstone specimens with a single structural plane to investigate their mechanical behaviors and failure characteristics under different in situ stress states.The experimental results indicate that the dip angle of structural plane(θ)and the intermediate principal stress(σ2)have an important influence on the peak strength,cracking mode,and rockburst severity.The peak strength exhibits a first increase and then decrease as a function ofσ2 for a constantθ.However,whenσ2 is constant,the maximum peak strength is obtained atθof 90°,and the minimum peak strength is obtained atθof 30°or 45°.For the case of an inclined structural plane,the crack type at the tips of structural plane transforms from a mix of wing and anti-wing cracks to wing cracks with an increase inσ2,while the crack type around the tips of structural plane is always anti-wing cracks for the vertical structural plane,accompanied by a series of tensile cracks besides.The specimens with structural plane do not undergo slabbing failure regardless ofθ,and always exhibit composite tensile-shear failure whatever theσ2 value is.With an increase inσ2 andθ,the intensity of the rockburst is consistent with the tendency of the peak strength.By analyzing the relationship between the cohesion(c),internal friction angle(φ),andθin sandstone specimens,we incorporateθinto the true triaxial unloading strength criterion,and propose a modified linear Mogi-Coulomb criterion.Moreover,the crack propagation mechanism at the tips of structural plane,and closure degree of the structural plane under true triaxial unloading conditions are also discussed and summarized.This study provides theoretical guidance for stability assessment of surrounding rocks containing geological structures in deep complex stress environments.
基金Supported by the Natural Science Foundation of Fujian Province(No.2024J011318No.2024J011321)Fuzhou Science and Technology Program(No.2023-S-005).
文摘Dear Editor,Descemet’s membrane detachment(DMD)is considered as a potential sight-threatening complication following various intraocular surgeries,particularly cataract surgery[1].The labile adhesion between the Descemet’s membrane(DM)and the posterior corneal stromal layer can be easily separated with minimal mechanical force.Several risk factors have been associated with the development of DMD including old age,improper intraoperative operation,corneal ectatic disorders,and endothelial disorders and so on[1-4].
基金Key Research and Development Program of Hubei Province(Project No.:2021BCA125)。
文摘Purpose:To summarize and analyze the clinical features and management of postoperative choroidal detachment in glaucoma.Methods:Ten cases of choroidal detachment that occurred after glaucoma surgery were collected from March 2023 to February 2024 in the hospital.Their clinical characteristics and treatment effects were observed and their causes were analyzed.Results:After the operations,the eyes with choroidal detachment after glaucoma surgery had 2 cases of true microphthalmos,6 cases of advanced glaucoma,and 2 cases of glaucoma secondary to vitreoretinal surgery.The postoperative manifestations were persistent shallow anterior chamber,the formation of anterior chamber,and then suddenly became shallow or disappeared.Meanwhile,the intraocular pressure was lower than 6 mmHg.Ultrasound and funduscopic examination showed that the choroid and retina were partially elevated,and the choroidal detachment recovered after treatment.Conclusion:Choroidal detachment is one of the common postoperative complications in glaucoma,especially in some special types of refractory glaucoma.Adequate perioperative management before surgery,cautious and delicate operation during surgery,and close observation and treatment after surgery can obviously decrease the occurrence and damage.
基金Supported by the Medical Scientific Research Foundation of Guangdong Province,China(No.C2022060).
文摘AIM:To compare the proportion of rhegmatogenous retinal detachment(RRD)associated with choroidal detachment(RRDCD)in the emergency surgery group with the routine inpatient surgery group and determine risk factors for RRDCD.METHODS:A total of 694 patients(694 eyes)diagnosed with RRD in the emergency surgery(the median duration of RRD was 5d)group were included from the Department of Ophthalmic Emergency,and 692 patients(eyes)in the routine inpatient surgery group(the median duration was 15d)were selected randomly from the Ocular Fundus Department.Demographics,refractive status,macular status,lens status,extent of retinal detachment,number of retinal breaks,duration of symptoms before surgery,and the incidence of RRDCD were compared.A logistic regression analysis was used to determine potential risk factors for RRDCD.RESULTS:Compared to the routine inpatient surgery group,the emergency surgery group had a significant less median time to surgery(P<0.001)and a decreased proportion of RRDCD(2.88%vs 10.84%,P<0.001).Logistic regression analysis revealed that a prolonged duration of RRD[OR 3.51,95%confidence interval(CI)1.98-6.23],pseudophakia/aphakia status[OR 2.74,95%CI(1.50-4.98)],multiple retinal breaks[OR 1.67,95%CI(1.03-2.70)],and a substantial extent of RRD[OR 11.58,95%CI(7.12-18.84)]were independent risk factors for RRDCD.CONCLUSION:Emergency surgical pattern of RRD demonstrates a lower incidence of RRDCD.The adoption of an expedited surgical approach has the potential to reduce the duration of RRD,possibly correlating with a decreased risk of RRDCD development.
文摘AIM:To report the refractive and surgical outcomes of scleral buckling(SB)with or without pars plana vitrectomy(PPV)in patients with pseudophakic rhegmatogenous retinal detachment(PRRD).METHODS:A consecutive case series of patients with pseudophakia who underwent retinal detachment(RD)surgery was enrolled.The SB procedures were selected to initially treat primary pseudophakic PRRDs and SB-PPV for more complex cases,according to preoperative findings.Eyes with anterior chamber intraocular lens,proliferative vitreoretinopathy anterior to equator,previous invasive glaucoma surgery,severe degenerative myopia or macular hole,and<6mo follow-up were excluded from outcomes analysis.The primary clinical outcome measures were the single surgery anatomic success(SSAS)and final surgery anatomic success(FSAS)rates.Secondary outcome measures were postoperative visual acuity and refractive error.RESULTS:A total of 81 consecutive patients(81 eyes)were enrolled for analysis,comprising 66(81%)men and 15(19%)women with a mean age of 58y(range,33-86y)and the mean final follow-up period was 21.0±19.6mo.A total of 62 PRRDs(n=62;76.5%)were repaired with an initial SB,and 19 PRRDs(n=19;23.5%)were repaired with a combined SB-PPV.The SSAS and FSAS rates were 92.6%(75/81)and 100%(81/81),respectively.All initial failures had retinal reattachment after the secondary PPV.The mean final postoperative best-corrected visual acuity(BCVA)was 0.42±0.33 logMAR(visual acuity 20/55)and final mean refractive error was-1.48±1.40 diopters.The patients who underwent initially SB-PPV had a significantly longer duration of RD and a higher giant retinal tear rate(P<0.05)preoperatively.SSAS was 56/62(90.3%)and 19/19(100%),and the mean postoperative refractive error was-1.30±1.32 D and-1.53±1.38 D for the patients in the SB and SB-PPV groups,respectively.There was no statistically significant difference for those who had SSAS and postoperative refractive errors between the 2 groups.The postoperative BCVAs of the patients with SSAS were not significantly better in the SB group(median,20/40)than in the SB-PPV group(median 20/50).In the SB group,patients with macula-on had better visual acuity postoperatively than patients with macula-off(P=0.000).CONCLUSION:The initial surgical procedures of SB with or without PPV according to the preoperative findings achieve a high reattachment rate and an acceptable refractive error for primary pseudophakic RRD management.
基金supported by the National Science and Technology Major Project(2024ZD1000705)the Basic Research Project of Liaoning Provincial Department of Education-Key Project of Independent Topic Selection(LJ212410147007).
文摘Fissured coal mass under triaxial unloading condition exhibits higher burst potential than the triaxial loading condition,which poses challenge to safety and productivity of resources extraction and underground space utilization.To comprehensively understand the mechanism of unloading-induced burst during excavation process,this study investigated the fracture and energy evolution of samples with different fissure types such as single,two parallel,and two coplanar-parallel using PFC2D modelling.Triaxial loading tests were conducted to determine the compressive strengths and other parameters.With increase of fissure inclination angle,the triaxial compressive strength decreases forβ=0°-30°,and then increase forβ=30°-90°.The strength of samples with two coplanar-parallel fissures is the highest.Fissure can significantly change the distribution of fracture and elastic energy.Secondary cracks were generated starting from both ends of the fissure.Forβ=0°-60°,low elastic strain energy area was produced around the fissure along the loading direction.The elastic strain energy is transferred to the outside of fissures.Forβ=75°-90°,only a small amount of high elastic strain energy was generated on both sides of the fissure.The fracture expansion under unloading conditions occurred due to tensile stress T caused by unloading differential rebound deformation and the shear stress on the fissure surface.
基金supported by National Natural Science Foundation of China(No.12375227)Innovation in Fusion Engineering Technology of Institute(No.E35QT1080C)。
文摘During the EAST radiative divertor experiments,one of the key challenges was how to avoid the occurrence of disruptive events caused by excessive impurity seeding.To estimate the required impurity fraction for divertor detachment,we introduce a reduced edge plasma radiation model.In the model,based on the momentum conservation along the magnetic field line,the upstream pressure is determined by the plasma density and temperature at the divertor target,and then the impurity radiation loss is obtained by the balance of the heat and particle fluxes.It is found that the required impurity fraction shows a non-monotonic variation with divertor electron temperature(T_(d))when 0.1 eV<T_(d)<10 eV.In the range of 0.1 eV<T_(d)<1 e V,the position near the valley of required impurity fraction corresponds to strong plasma recombination.Due to the dependence of the volumetric momentum loss effect on the T_(d)in the range of 1 eV<T_(d)<10 eV,the required impurity fraction peaks and then decreases as T_(d)is increased.Compared to neon,the usage of argon reduces the impurity fraction by about twice.In addition,for the various fitting parameters in the pressure-momentum loss model,it is shown that the tendency of required impurity fraction with T_(d)always increases first and then decreases in the range of 1 eV<T_(d)<10 eV,but the required impurity fraction decreases when the model that characterizes the strong loss in pressure momentum is used.
基金financially supported by the National Natural Science Foundation of China(No.51934001)。
文摘Gas rapid unloading(GRU)is an innovative technology for ore comminution.Increasing the production of fine powder in each ore grinding cycle is vital for scaling up the GRU method to industrial applications.This study utilizes laboratory experiments to demon-strate that moderately reducing the orifice size significantly enhances pulverization and increases fine particle yield.Numerical simulations suggest that smaller orifices improve pulverization by increasing jet speed,reducing pressure drop,and creating a larger pressure difference inside and outside the unloading orifice.The orifice size should be optimized based on feed size to ensure efficient ore discharge.Reducing the unloading orifice size improves GRU grinding efficiency and energy use,offering guidance for the design of ore discharge ports in future industrial-scale equipment.
基金Project supported by Youth Project of Science and Technology Research Program of Chongqing Education Commission of China (Grant No. KJQN202404522)。
文摘Kinesin is an archetypal microtubule-based molecular motor that can generate force to transport cargo in cells. The load dependence of the detachment rate is an important factor of the kinesin motor, the determination of which is critically related to the chemomechanical coupling mechanism of the motor. Here, we use three models for the load dependence of the detachment rate of the kinesin motor to study theoretically and numerically the maximal force generated and microtubuleattachment duration of the motor. By comparing the theoretical and numerical results with the available experimental data,we show that only one model can explain well the available experimental data, indicating that only this model can be applicable to the kinesin motor.
文摘This paper presents a new criterion for determining the unloading points quantitatively and consistently in a multi-stage triaxial test.The radial strain gradient(RSG)is first introduced as an arc tangent function of the rate of change of radial strain to time.RSG is observed to correlate closely with the stress state of a compressed sample,and reaches a horizontal asymptote as approaching failure.For a given rock type,RSG value at peak stress is almost the same,irrespective of the porosity and permeability.These findings lead to the development of RSG criterion:Unloading points can be precisely determined at the time when RSG reaches a pre-determined value that is a little smaller than or equal to the RSG at peak stress.The RSG criterion is validated against other criteria and the single-stage triaxial test on various types of rocks.Failure envelopes from the RSG criterion match well with those from single-stage tests.A practical procedure is recommended to use the RSG criterion:an unconfined compression or single-stage test is first conducted to determine the RSG at peak stress for one sample,the unloading point is then selected to be a value close to the RSG at peak stress,and the multi-stage test is finally performed on another sample using the pre-selected RSG unloading criterion.Generally,the RSG criterion is applicable for any type of rocks,especially brittle rocks,where other criteria are not suitable.Further,it can be practically implemented on the most available rock mechanical testing instruments.
基金Supported by the Shenzhen Science and Technology Program(No.JCYJ20220818103207015)the SanMing Project of Medicine in Shenzhen(No.SZSM202311012).
文摘AIM:To establish a risk prediction model for secondary cataract within 2y after pars plana vitrectomy(PPV)in patients with primary rhegmatogenous retinal detachment(RRD).METHODS:Clinical data of patients with primary RRD treated at the Shenzhen Eye Hospital were retrospectively collected.Twenty-four potential influencing factors,including patient characteristics and surgical factors,were selected for analysis.Independent risk factors for secondary cataract were identified through univariate comparisons and multivariate logistic regression analysis.A risk prediction model was constructed and evaluated using receiver operating characteristic(ROC)curves,area under the ROC curve(AUC),calibration plots,and decision curve analysis(DCA)curves.RESULTS:The 386 cases(389 eyes)of patients who underwent PPV and had complete surgical records were ultimately included.Within a 2-year longitudinal observation,41.39%of patients developed cataract secondary to PPV.Logistic regression results identified a history of hypertension[odds ratio(OR)=1.78,95%CI:1.002–3.163,P=0.049],silicone oil tamponade(OR=3.667,95%CI:2.373–5.667,P=0.000),and lens thickness(OR=1.978,95%CI:1.129–3.464,P=0.017)as independent risk factors for cataract secondary to PPV.The constructed nomogram achieved AUC=0.6974.Calibration plots indicated good agreement between predicted and observed outcomes,while DCA curves demonstrated the model’s clinical utility.CONCLUSION:By incorporating a history of hypertension,vitreous substitute type,and lens thickness,this study constructs a prediction model with moderate discriminative ability.This model offers a valuable tool for clinicians to identify high-risk patients early,potentially allowing for more timely interventions and improved patient outcomes.
基金funded by the National Natural Science Foundation of China(Grant No.41941018).
文摘In this study,based on the rockburst disaster mechanism of excess energy △E>0,true triaxial transient unloading strainburst(including instantaneous strainburst and delayed strainburst)experiments were performed on granite specimens at different maximum principal stress levels.The experimental results were then analyzed,with the strainburst characteristics and acoustic emission(AE)responses of the granite specimens being examined.The excess energy △E was derived through a comparison with the results of conventional biaxial compression tests.The following beneficial conclusions were drawn.The mechanical strength of delayed strainburst specimens initially increases and then decreases with the rise of the unloading stress level.In contrast,the mechanical strength of instantaneous strainburst specimens is higher than that of delayed ones,increasing with the unloading stress level.In terms of fragment ejection velocity and scale,the rockburst intensity of a specimen is positively correlated with its mechanical strength.A pronounced linear relationship exists between the excess energy △E and the fragment ejection velocity(as well as weight),indicating that △E is intimately linked to the kinetic energy of rockbursts.Rockbursts lead to the formation of burst pits and typical V-shaped damage zones near the free face of the specimens,within which tensile cracks dominate.Additionally,the distribution of AE AFRA values indicates that the proportion of tensile cracks increases with the rise of unloading stress level,suggesting that transient unloading under high stress levels significantly promotes tensile fracture.It is anticipated that this study will provide further elucidation on the mechanism of rockburst kinetic energy generation,thereby establishing a foundation for the design of rockburst support measures in engineering applications.
基金financially supported by National Natural Science Foundation of China(No.52304136)Young Talent of Lifting Engineering for Science and Technology in Shandong,China(No.SDAST2024QTA060)Key Project of Research and Development in Liaocheng(No.2023YD02)。
文摘It is important to analyze the damage evolution process of surrounding rock under different water content for the stability of engineering rock mass.Based on digital speckle correlation(DSCM),acoustic emission(AE)and electromagnetic radiation(EMR),uniaxial hierarchical cyclic loading and unloading tests were carried out on sandstones with different fracture numbers under dry,natural and saturated water content,to explore the fracture propagation,failure precursor characteristics and damage response mechanism under the influence of water content effect.The results show that with the increase of water content,the peak stress and crack initiation stress decrease gradually,and the decreases are 15.28%-21.11%and 17.64%-23.04%,respectively.The peak strain and crack initiation strain increase gradually,and the increases are 19.85%-44.53%and 19.15%-41.94%,respectively.The precracked rock with different water content is mainly characterized by tensile failure at different loading stages.However,with the increase of water content,the proportion of shear cracks gradually increases,while acoustic emission events gradually decrease,the dissipative energy and energy storage limits of the rock under peak load gradually decrease,and the charge signal increases significantly,which is because the lubrication effect of water reduces the friction coefficient between crack surfaces.
基金funded by NSFC(52204086,52474122)Guangdong Provincial Department of Science and Technology(2025B1515020067,2022A1515240009).
文摘This article investigates the mechanical responses and acoustic emission(AE)characteristics of sandstone under the triaxial differential cyclic loading(DCL)at different unloading rates of confining stress.The test results indicate that strength of rock specimens under different stress paths of triaxial unloading confining stress-differential cyclic loading(TUCS-DCL)can be fitted by the Mohr–Coulomb,Hoek–Brown,and Bieniawski criteria.The confining stress unloading rate can dominate the radial strain rate,while the axial DCL pattern has an unpronounced effect.The confining stress unloading rate affects the energy evolution in radial and axial directions of specimens,with the ratio of radially released energy to axially consumed energy fluctuating more significantly during the fast unloading of confining stress,the valley value of the ratio can serve as a precursor for failure.The confining stress unloading rate has no significant effect on stress–strain phase shift,while axial rapid-loading-slow-unloading can correspond to a larger magnitude of phase shift.AE signals begin to significantly increase after the confining stress is unloaded to zero,and a notable Kaiser effect is observed during cyclic loading preceding the failure.
文摘Rhegmatogenous retinal detachment(RRD)is a sight threatening condition in which the neurosensory retina separates from the underlying retinal pigment epithelium.With an incidence of 6.3 to 17.9 per 100,000 persons(1),RRD is a condition frequently encountered by vitreoretinal specialists.Because the fovea is responsible for central visual acuity,foveal detachment is associated with poor presenting vision and is the strongest prognostic factor predicting poor visual outcome after RRD repair(2).
基金supported by the National Natural Science Foundation of China(Grant Nos.42372326 and 42090054)supported by the State Key Laboratory of Geohazard Prevention and Geoenvironment Protection Independent Research Project(SKLGP2023Z015).
文摘During the excavation of large-scale rock slopes and deep hard rock engineering,the induced rapid unloading serves as the primary cause of rock mass deformation and failure.The essence of this phenomenon lies in the opening-shear failure process triggered by the normal stress unloading of fractured rock mass.In this study,we focus on local-scale rock fracture and conduct direct shear tests under different normal stress unloading rates on five types of non-persistent fractured hard rocks.The aim is to analyze the influence of normal stress unloading rates on the failure modes and shear mechanical characteristics of non-persistent fractured rocks.The results indicate that the normal unloading displacement decreases gradually with increasing normal stress unloading rate,while the influence of normal stress unloading rate on shear displacement is not significant.As the normal stress unloading rate increases,the rocks brittle failure process accelerates,and the degree of rocks damage decreases.Analysis of the stress state on rock fracture surfaces reveals that increasing the normal stress unloading rate enhances the compressive stress on rocks,leading to a transition in the failure mode from shear failure to tensile failure.A negative exponential strength formula was proposed,which effectively fits the relationship between failure normal stress and normal stress unloading rate.The findings enrich the theoretical foundation of unloading rock mechanics and provide theoretical support for disasters prevention and control in rock engineering excavations.
